User:Geronimo20/Sandbox/box3

Sexual maturity in females is reached at about 34–77 mm tail width (TW) (about 60–120 mm carapace length), depending on locality. Mating takes place after moulting in autumn, and the eggs hatch in spring into the short-lived naupliosoma larvae. Most of the phyllosoma larval development takes place in oceanic waters tens to hundreds of kilometres offshore over at least 12 months. Near the edge of the continental shelf the final-stage phyllosoma metamorphoses into the settling stage, the puerulus. Puerulus settlement takes place mainly at depths less than 20 m, but not uniformly over time or between regions. Settlement indices measured on collectors can fluctuate widely from year to year. Most females in the south and southeast of the South Island do not breed before reaching MLS.

Some rock lobsters undertake long-distance migrations in some areas. During spring and early summer, variable proportions of usually small males and immature females move various distances against the current from the east and south coasts of the South Island towards Fiordland and south Westland.^[53]

Southern rock lobster The Southern rock lobster or Red rock lobster, Jasus edwardsii, usually called simply crayfish, is a species of spiny lobster found throughout coastal waters of southern Australia and New Zealand including the Chatham Islands. The commercial rock lobster fishery is New Zealand's third biggest seafood export earner. Spiny rock lobsters are both carnivorous and filter feeders. They live in and around reefs at depths ranging from 5 to 275 metres deep at the continental shelf. They can be dark red and orange above with paler yellowish abdomens or grey-green brown with the paler underside. The more tropical animals tend to have the brighter colours.

Rock lobsters crawl on the bottom or swim backwards by flexing their tail sharply from extended to beneath the body. Their antenna are sensitive to water vibrations and, where active fisheries exist, they are quite timid and quick to withdraw further into their den. Otherwise they are relatively active ocean-bottom explorers and feed on almost anything that they come across without fear of most predators. Females carry their eggs externally under their tails and normal practice is not to harvest females while they are carrying eggs.

The rock lobster has among the longest larval development known for any marine creature. The phyllosoma (Greek for leaf-like) larvae spend close to two years in oceanic waters before metamorphosing to the postlarval stage, known as the puerulus, which then swims towards the coast to settle.

Rock lobsters are caught in pots which can be any sort of open-weave or slatted box-like structure with an entry at the top that is V-shaped so that the lower end is well off the floor of the box and relatively narrow. Any form of fish or meat bait is tied into the floor area to attract the rock lobsters. A light buoy on a line from the pot marks the location, and the name of the fisher too. Rock lobsters are quite robust out of water and, if kept cool and damp, will live for many hours — possibly days.

In New Zealand, rock lobsters are an important kai moana (seafood) and are caught by non-commercial divers using their hands or a short gaff to haul the rock lobsters out of caves, crevices or tunnels. Rock lobsters are normally found facing outwards and the gaff is positioned under the body shell so that the hook can be located at the join of that shell and in front of the softer tail-joint membranes. The animal is often plunged into boiling water for a few minutes to cook. Some people prefer to have the animal part-frozen before cooking.

Many people in financially well-off countries eat only the tail meat. New Zealanders and many Polynesians, however, tend to eat every part of the animal except for the exoskeleton and the gills.

Rock lobsters, in well-fished areas, may weigh up to 3 kg and are usually found in deeper cool water. In less-fished areas in the southern hemisphere it is not uncommon to catch individuals weighing 10 kg.

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Scampi moult several times per year in early life and probably about once a year after sexual maturity (at least in females). Early work suggested that female M. challengeri achieve sexual maturity at about 40 mm orbital carapace length (OCL) in the Bay of Plenty and on the Chatham Rise, about 36 mm OCL off the Wairarapa coast, and about 56 mm OCL around the Auckland Islands. Work on more recent trawl surveys in QMAs 1 and 2 suggest that 50% of females were mature at 30 mm OCL in these areas. The peak of moulting and spawning activity seems to occur in spring or early summer. Larval development of M. challengeri is probably very short, and may be less than 3 days in the wild. The abbreviated larval phase may, in part, explain the low fecundity of M. challengeri compared with N. norvegicus (that of the former being about 10–20% that of the latter).

Relatively little is known of the growth rate of any of the Metanephrops species in the wild. Tagging of M. challengeri to determine growth rates was undertaken in the Bay of Plenty in 1995, and the bulk of recaptures were made late in 1996. About 1% of tagged animals were recaptured, similar to the average return rate of similar tagging studies for scampi and prawns overseas. Many more females than males were recaptured, and small males were almost entirely absent from the recapture sample. Scampi captured and tagged at night were much more likely to be recaptured than those exposed to sunlight.

Scampi from QMA2 were successfully reared in aquariums for over 12 months in 1999–2000. Results from these growth trials suggested a von Bertalanffy K of about 0.3 for both sexes, compared with <0.15 for the tagging trial. Extrapolating the length-based results to age-based curves suggests that scampi are about 3–4 years old at 30 mm carapace length and may live for 15 years. There are many uncertainties with captive reared animals, however, and these estimates should not be regarded as definitive. In particular, the rearing temperature was 12º C compared with about 10º C in the wild (in QMAs 1 and 2), and the effects of captivity are largely unknown.

The maximum age of New Zealand scampi is not known, although analysis of tag return data and aquarium trials suggest that this species may be quite long lived. Metanephrops spp in Australian waters may grow rather slowly and take up to 6 years to recruit to the commercial fishery, consistent with estimates of growth in M. challengeri. N. norvegicus populations in some northern European populations achieve a maximum age of 15–20 years, consistent with the estimates of natural mortality, M, for M. challengeri.^[59]

Scampi (Metanephrops challengeri) are deep-water burrowing lobsters. They have been commercially harvested since the 1980s from the Bay of Plenty, off the Chatham Rise, and around the subantarctic Auckland Islands. They are slender pink animals, up to 30 centimetres long and weighing 100 grams. Scampi are cooked and eaten in the same manner as prawns.

This little crustacean was the subject of a 2003 parliamentary select committee inquiry. There had been allegations of corruption against senior officers of the Ministry of Fisheries regarding scampi quotas. Although the inquiry found there was no foundation to the allegations, it did find that the ministry had given preferential treatment to the fishing company holding most of the scampi quota.^[60]

Haliotis iris H. australis Paua are herbivores which can form large aggregations on reefs in shallow subtidal coastal habitats. Movement is over a sufficiently small spatial scale that the species may be considered sedentary. Paua are broadcast spawners and spawning is thought to be annual. Habitat related factors are an important source of variation in the post-settlement survival of paua.

Growth, morphometrics, and recruitment can vary over short distances and may be influenced by factors such as wave exposure. Recruitment indices (i.e., the mean number of juveniles sampled in dive surveys) indicate a higher abundance of juveniles off D’Urville Island and in Cook Strait than in the wave exposed habitats of west coast Stewart Island, Fiordland and southern Otago.^[62]

Paua or pāua is the Māori name given to three species of large edible sea snails, marine gastropod molluscs which belong to the family Haliotidae (genus Haliotis), known in the USA as abalone and in the UK as Ormer shells.

The New Zealand paua is endemic to New Zealand coastal waters. They are commonly found in shallow coastal waters along rocky shorelines in depths of 1 to 15 m. These large sea snails survive the strong tidal surges by clinging to rocks using their large muscular foot. They feed on seaweed.

There are three species. The main one, Haliotis iris, grows up to 18 cm in length.

The shell of the paua is oval and the exterior is often covered with greyish incrustations. In contrast the interior of a Paua is an iridescent swirl of intense green, blue, purple, and sometimes pink colours.

The paua is iconic in New Zealand: its black muscular foot is considered a delicacy, and the shell is frequently used in jewelry.

To Māori, paua are recognised taonga, or treasure, esteemed both as kai moana (seafood) and as a valued resource for traditional and contemporary arts and crafts. Paua are frequently used to represent the eyes in Māori carvings and traditionally are associated with the stars, or whetu the eyes of ancestors that gaze down from the night sky.

Paua are gathered recreationally and commercially but strict catch limits are set for both - for recreational fishers this is 10 paua per person, per day. The minimum legal size for caught paua is 125 mm. (The New Zealand Herald, May 30, 2006). Paua can only be caught by free diving. It is illegal to dive for paua using scuba equipment.

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Paphies australis The pipi (Paphies australis) is a common burrowing bivalve mollusc of the family Mesodesmatidae. Pipi are distributed around the New Zealand coastline, including the Chatham and Auckland Islands (Powell, 1979) , and are characteristic of protected beaches, bays and estuaries (Morton & Miller, 1968) . Pipi are tolerant of moderate wave action, and commonly inhabit coarse shell sand substrata in bays and at the mouths of estuaries where silt has been removed by waves and currents (Morton & Miller, 1968) . They have a broad tidal range, occurring intertidally and subtidally in high-current harbour channels to water depths of at least 7 m (Dickie, 1986a; Hooker, 1995a) , and are locally abundant, with densities greater than 1000 m-2 in certain areas (Grace, 1972).

Pipi reproduce by free-spawning, and most individuals are sexually mature at about 40 mm shell length (Hooker & Creese, 1995a) . Gametogenesis begins in autumn, and by late winter many pipi have mature, ready-to-spawn gonads (Hooker & Creese, 1995a) . Pipi have an extended breeding period from late winter to late summer, with greatest spawning activity occurring in spring and early summer. Fertilised eggs develop into planktotrophic larvae, and settlement and metamorphosis occur about three weeks after spawning (Hooker, 1997) . In general, pipi have been considered sedentary when settled, although Hooker (1995b) found that pipi may utilise water currents to disperse actively within a harbour. The trigger for movement is unknown, but this ability to migrate may have important implications to their population dynamics.

Pipi growth dynamics are not well known. Growth appears to be fairly rapid, at least in dynamic, high-current environments such as harbour channels. Hooker (1995a) showed that pipi at Whangateau Harbour (northeastern New Zealand) grew to about 30 mm in just over one year (16–17 months), reached 50 mm after about three years, and grew very slowly after attaining 50 mm. There was a strong seasonal component to growth, with rapid growth occurring in spring and summer, and little growth in autumn and winter. Williams et al. (2006) used Hooker’s (1995a) tag-recapture and length frequency time series data to generate formal growth estimates for Whangateau Harbour pipi (Table 2). Estimates are available also from time series of size frequencies on sheltered Auckland beaches (Table 2; Morrison & Browne, 1999; Morrison et al., 1999) , although these estimates were likely to have been poorly estimated due to variability in the length data.

Little is known about the natural mortality or maximum longevity of pipi. Haddon (1989) suggested pipi are unlikely to live much more than 10 years, and used assumed maximum ages of 10, 15 and 20 years old to estimate maximum constant yield for Mair Bank pipi in 1989. The estimation of the rate of instantaneous natural mortality (M) is difficult for pipi owing to the immigration and emigration of individuals from different areas. As the timing and frequency of these movements are largely unknown, the separation of mortality from movement effects is likely to be problematic. Williams et al. (2006) assumed values of M = 0.3, 0.4, and 0.5 to estimate yields for Mair Bank in 2005­–06.^[64]

Settlement is likely to be sporadic among years and appears to differ among locations and habitats (Dix 1972, Walker 1995). Few small kina were observed in any of the surveys in Dusky Sound (McShane et al. 1993). These results suggest that the productivity of stocks in Fiordland may be low and that recruitment over-fishing is a real possibility. Overall, there is very little knowledge of the processes that limit the settlement and recruitment of kina.

There is relatively little information available on the interactions between kina, its predators and competitors. Although a wide range of fish and invertebrate predators eat kina, there is limited evidence that these species control or limit populations of kina in Fiordland. Recent work in a marine reserve, where large predators such as reef fishes and crayfish are abundant, indicates that predators can control numbers of kina surviving the transition from crevice-bound to open substratum grazing (Cole and Keuskamp 1998, Babcock et al. 1999). Babcock et al. have drawn a direct link between the increases in snapper and crayfish populations and the long-term decline in kina populations in the Leigh Marine Reserve. It is likely, however, that changes in the abundance of kina, and the consequent changes in habitat representation, are part of a complex set of interacting processes, including but not exclusively, increased predation. There no evidence that high kina densities limit rock lobster populations (Andrew and MacDiarmid 1991).

Kina compete with a range of invertebrate herbivores, including paua. There is no published evidence that high densities of kina limit paua populations in Fiordland. McShane (1997) reported that paua are abundant in Dusky Sound, and in Chalky and Preservation Inlets but are rare in the fjords.

Lamare and Mladenov (2000) estimate that kina grow 8–10 mm in their first year of life. Growth rates will vary considerably depending on local conditions but kina may take 8–9 years to reach 100 mm TD and very large individuals may reach ages of 20+ years (McShane and Anderson 1997, Lamare and Mladenov 2000).^[65]

Kina or the common sea urchin or sea egg (Evechinus chloroticus) is the best-known species – commercially valuable and considered a delicacy by Māori. Resembling a curled-up green hedgehog, kina has a nearly spherical shell (or test) protecting its internal organs. Projecting from the shell are long and short movable spines and tube feet. Its mouth, on the underside, contains a five-sided limy structure known as Aristotle’s lantern. This acts like a set of jaws and teeth, grinding up food into digestible pellets.

These small creatures (5–10 centimetres in diameter) are endemic to New Zealand, found on shallow water reefs from the Three Kings Islands to the Snares, and around the Chatham Islands. They spawn from November to March, and have a free-swimming larval stage that lasts for up to 3 months. They can live for 20 years or more.

Kina are important members of rocky reefs. They are omnivorous but prefer to eat large brown seaweeds, especially the common kelp Ecklonia radiata. Dozens may gather and eat out all the seaweed at a site, leaving it barren. Their fearsome spines afford some protection from predators, but small kina are no match for large rock lobsters, snapper or the seven-armed starfish.

Like most echinoderms, kina have separate sexes, but it is difficult to tell them apart unless the shell is cracked open. During early summer, their five sets of sex glands become very swollen. These are the highly prized kina roe, traditionally eaten raw by Māori. Some 600–700 tonnes of wild kina are commercially harvested each year, most being sold on the domestic market. New Zealand fishermen would like to export kina to Japan, where top-quality roe sells for NZ$500 a kilogram. However, the quality of wild roe is variable – some may be bitter or brown, and a reliable export market has not yet developed. Scientists have started raising kina in aquaculture facilities to investigate whether different diets enhance growth or roe quality.^[66]

Zygochlamys delicatula The New Zealand queen scallop (Zygochlamys delicatula) is also known as the southern queen scallop, southern fan scallop, and gem scallop. This small pectinid species is distributed on the outer continental shelf along the east coast of the South Island, from Kaikoura down to Macquarie Island. There are nine other species in the genus, none of which have attracted commercial interest, probably because of their small size. Similar species such as Chlamys islandica and Chlamys varia support important fisheries in other countries. New Zealand queen scallops are distributed from Kaikoura to the southern islands including the Snares, Bounty, Antipodes, and Macquarie Islands. There are no records of live queen scallops being caught north of Kaikoura, or on the west coast of the South Island.

A dredge survey off Otago in October 1983 showed queen scallops were distributed in long patches orientated along the slope of the continental shelf. They were most abundant in depths beyond 130 m, on the plateau between the Taiaroa and Papanui Canyons, and south. North of the Taiaroa Canyon catches diminished steadily towards the Karitane Canyon; few were caught north of the canyon. Only low numbers of queen scallops were caught in depths shallower than 110 m.

Juvenile queen scallops are frequently found attached to fragments of bryozoa and other biogenic debris, including the shells of other scallops and the dredge oyster. Height frequency distributions of samples show size composition of the population differs with area, and it is inferred that settlement probably varies spatially and temporally. The estimated 40-50 days larval life may result in queen scallop larvae being well mixed, both vertically and horizontally, in the water column. Predation of newly settled spat may also affect the pattern of recruitment and add to the variability in year class representation.

Estimates of growth for New Zealand queen scallops suggest they become sexually mature at four years for males and five years for females. As length is slightly less than height, queen scallops are estimated to reach the minimum takeable size of 50 mm at about eight years. However, growth estimates are uncertain, with information from tagging studies suggesting queen scallops enter the fishery much earlier, at three to five years.^[67]

Scallop

Pecten novaezelandiae SCA 1

P. fumatus and P. modestus. Scallops of various taxonomic groups are found in all oceans and support many fisheries world-wide. Most undergo large population fluctuations.

Scallops are found in a variety of coastal and intertidal habitats, but particularly in semi-enclosed areas where circulating currents are thought to retain larvae. After the planktonic larval phase and a relatively mobile phase as very small juveniles, scallops are largely sessile and move actively, mainly in response to predators. They may, however, be moved considerable distances by currents and storms and are sometimes thrown up in large numbers on beaches.

Scallops are functional hermaphrodites, and become sexually mature at a size of about 60–70 mm shell length. They are extremely fecund and may spawn several times each year. Fertilisation is external and larval development lasts for about 3 weeks. Initial settlement occurs when the larva attaches via a byssus thread to filamentous material or dead shells on or close to the seabed. The major settlement of spat in northern fisheries usually takes place in early January. After growth to about 5 mm, the byssus is detached and, after a highly mobile phase as a small juvenile, the young scallop takes up the relatively sedentary adult mode of life.

The very high fecundity of this species, and likely variability in the mortality of larvae and pre-recruits leads to great variability in annual recruitment. This, combined with variable mortality and growth of adults, leads to scallop populations being highly variable from one year to the next, especially in areas of rapid growth where the fishery may be supported by only one or two year classes. This variability is characteristic of scallop populations world-wide, and often occurs independently of fishing pressure.

Little detailed information is available on the growth and natural mortality of Northland scallops, although the few tag returns from Northland indicate that growth rates in Bream Bay are similar to those in the nearby Coromandel fishery (see the report for SCA CS). The very large average size of scallops in the northern parts of the Northland fishery and the consistent lack of small animals there suggests that growth rates may be very fast in the far north.

SCA CS
Pecten novaezelandiae is one of several species of “fan shell” bivalve molluscs found in New Zealand waters. Others include queen scallops and some smaller species of the genus Chlamys. P. novaezelandiae is endemic to New Zealand, but is very closely related to the Australian species P. fumatus and P. modestus. Scallops of various taxonomic groups are found in all oceans and support many fisheries world-wide. Most undergo large population fluctuations.

Scallops are found in a variety of coastal and intertidal habitats, but particularly in semi-enclosed areas where circulating currents are thought to retain larvae. After the planktonic larval phase and a relatively mobile phase as very small juveniles, scallops are largely sessile and move actively mainly in response to predators. They may, however, be moved considerable distances by currents and storms and are sometimes thrown up in large numbers on beaches. ^[68]

Scallops are functional hermaphrodites, and become sexually mature at a size of about 60–70 mm shell length. They are extremely fecund and may spawn several times each year. Fertilisation is external and larval development lasts for about 3 weeks. Initial settlement occurs when the larva attaches via a byssus thread to filamentous material or dead shells on or close to the seabed. The major settlement of spat in northern fisheries usually takes place in early January. After growth to about 5 mm, the byssus is detached and, after a highly mobile phase as a small juvenile, the young scallop takes up the relatively sedentary adult mode of life.

The very high fecundity of this species, and likely variability in the mortality of larvae and pre-recruits, leads to great variability in annual recruitment. This, combined with variable mortality and growth rate of adults, leads to scallop populations being highly variable from one year to the next, especially in areas of rapid growth where the fishery may be supported by only one or two year classes. This variability is characteristic of scallop populations world-wide, and often occurs independently of fishing pressure.

The growth of scallops within the Coromandel fishery is variable among areas, years, seasons and depths, and probably among substrates. In the Hauraki Gulf scallops have been estimated to grow to 100 mm shell length in 18 months or less whereas this can take three or more years elsewhere. In some years, growth is very slow, whereas in others it is very rapid. There is a steep relationship with depth and scallops in shallow water grow much faster than those in deeper water. This is not a simple relationship, however, as scallops in some very deep beds (e.g., Rangaunu Bay and Spirits Bay in the far north, both deeper than 40 m) appear to grow at least as fast as those in favourable parts of the Coromandel fishery. Food supply undoubtedly plays a role.

A variety of studies suggest that average natural mortality in the Coromandel fishery is quite high at M = 0.50 y-1 (instantaneous rate), and maximum age in unexploited populations is thought to be about 6 or 7 years.

The New Zealand scallop is a large industry and export product of New Zealand. The large white adductor muscle is eaten, sometimes the yellow gonad is often eaten as well. Pectin novaezealandiae is considered a fine food and can be expensive to purchase. Recreational and commercial fishing of this species is allowed at particular times of the year, this is called scallop season. The size and number of scallops which can be caught are under control of the quota management system. In some areas of suitable habitat, such as Tasman Bay scallop spat is seeded. This is an attempt to achieve a sustainable fishery.

Overview map

Dredge oyster (Foveaux Strait) Ostrea chilensis Ostrea chilensis is a protandrous hermaphrodite and breeds in spring and summer. Females produce large (280–290 mm) yolky eggs, which after fertilisation continue to develop to pediveligers in the inhalant chamber for 18–32 days (depending on temperature). Most larvae settle immediately on release (at a size of 444–521 mm) and seldom disperse more than a few centimetres from the parent oyster. Some larvae are released at smaller sizes and spend time in the plankton. In Foveaux Strait spat settlement is primarily during the summer months from December to February. Mean fertility of incubating oysters in Foveaux Strait was estimated to be 5.09 x 104 larvae, and only 6–18% of the sexually mature oysters spawned as females each year. Larvae settle primarily on live oysters, oyster shell and circular saws Astraea heliotropium. About two percent of the spat survive the first winter. Most mortality appears to result from predation by polychaetes, crabs and small gastropods. Although settlement predominates on under-surfaces of oysters and shell, most surviving spat are attached to the left (curved and generally uppermost) valve of living oysters. Growth rate of oysters has been estimated from height increment data. It varies between years and between areas of Foveaux Strait. Spat generally grow 5 to 10 mm in height the winter after settlement. Mean height after one year is 18 to 25, 25 to 35 mm after two, 30 to 51 mm after three, 40 to 65 mm after four, and 65 to 75 mm after the fifth year. They recruit to the legal-sized population (a legal-sized oyster will not pass through a 58 mm diameter ring, i.e., it must be at least 58 mm in the smaller of the two dimensions of height or length) at ages of 4–8 years. Oysters probably become sexually mature and breed as males in the third year and as females in the fourth year when greater than 50 mm in height.

Dunn et al. (1998a)(please refer to Plenary document for reference list) modelled the growth of oysters in four areas in Foveaux Strait. The oysters were measured at six-monthly intervals over three years. Dunn et al. (1998a) found that there was evidence for strong seasonal variation in growth, with mean growth over the winter found to be zero or even slightly negative (the latter presumably due to shell abrasion). The applicability of these estimates of growth to the fishery is unknown.

Mortality of adult oysters (outside epizootics) is probably low. The instantaneous rate of mortality, M, was estimated from the results of a mark-recapture experiment in 1974 and 1975 to lie between 0.009 y-1 and 0.015 y-1. The Working Group believes M was likely to be underestimated by this method, as did Allen (1979), who assumed a value of 0.1 for oysters in a simulation model of the fishery.

Dunn et al. (1998b) estimated natural mortality for the years 1974 to 1986 from the reanalysis of the above data. Estimated natural mortality was found to increase from 0.017 y-1 to 0.188 y-1 from 1974-1986 for oysters released in 1974, and from 0.009 y-1 to 0.199 y-1 for oysters released in 1973. The weighted average instantaneous natural mortality, M, for all data combined for the years from 1974 to 1986 was 0.042 y-1. The applicability of this estimate of mean M in the fishery is unknown. The value of mean M most likely lies between 0.042 and 0.1.

Two oysters, one tagged in 1973 and the other in 1975–76 were recaptured live in January 2003. They were recruit size when tagged and had survived a further 26–29 years (at an estimated age of at least 30 and 33 years). These oysters appeared to have grown little in length and height, but had significantly increased in depth and weight.

A major epizootic between 1986 and 1992 caused very high mortality. The haemocyte parasite B. exitiosus was identified as the cause of this mass mortality of oysters in 1986. The species was described in 1987 (Dinamani et al.,1987) and its life history in 1991 (Hine, 1991). ^[78]

Dredge oyster (Other) Ostrea chilensis The biology of T. chilensis was summarised by Handley and Michael (2001). Most of the parameters required for management purposes are based on the Foveaux Strait fishery described by Cranfield and Allen (1979). Oyster stocks in the Challenger area are generally low and seasonally variable suggesting high variability in recruitment (Osborne, 1999). Challenger oysters are reported to spawn at temperatures above 14°C. In Tasman and Golden Bay, significantly smaller and less developed larvae have been collected in the plankton than those collected from Foveaux Strait, implying Challenger oysters appear to release their larvae into the plankton for longer periods (Cranfield & Michael, 1989). The distances that the larvae could disperse have been estimated at 20 km in 5–12 days. These planktonic larvae may then be concentrated in patches by oceanographic conditions giving rise to substantial spatfalls in areas where suitable settlement surfaces allow.

The variability in shell shapes and high variability in growth rate between individuals, within areas, within the Challenger, and between years require careful consideration in describing growth. Assuming minimum legal size equals 58–65 mm in diameter, data from Drummond (1994b) infer Tasman Bay oysters could grow to legal size in two to three years. ^[79]

Bluff oysters. Bluff harbour is home to the Foveaux Strait oyster fleet. Bluff oysters are renowned for their succulence and flavour, and are considered a delicacy nationwide, with Bluff holding an annual oyster festival.^[80]. The oyster quota was severely reduced during the 1990s due to the effects of the toxic protozoan parasite Bonamia exitiosa upon the oyster beds.^[81]

Variously known in New Zealand as Bluff oyster, dredge oyster and flat oyster, or by its Māori name tio, this much-loved delicacy is really the Chilean oyster – Ostrea chilensis.

Found all around the New Zealand coast in small patches to depths of 35 metres or more, dredge oysters grow in extensive beds in the South Island’s Foveaux Strait, Golden Bay and Tasman Bay. The pear-shaped adult is a heavy-shelled bivalve, some 6–10 centimetres long, with a cupped lower shell and a flat upper shell. Life cycle

A dredge oyster spends its first 18–30 days as a larva within its parent’s body. It is then released into the water and settles a few centimetres away. It immediately cements the lower shell to some surface, often the shell of another oyster.

After about two years the cement bonding breaks down and the oyster lies on the muddy sea floor. It reaches sexual maturity around this time. A dredge oyster may be a hermaphrodite, producing eggs and sperm at the same time, or it may be in a definite male or female phase. It can alternate between each sex.

Dredge oysters can live for eight years or more and reach harvest width of 58 millimetres in four to six years. Foveaux Strait oyster fishery

Foveaux Strait oyster beds have been dredged since 1863. The first beds were small, and were soon depleted. A large bed discovered in eastern Foveaux Strait was dredged from 1888 until the 1950s. When this proved uneconomic, the focus moved to the centre of the strait. In the early 1930s, the oysters were struck by disease and many died. Other disease outbreaks followed in the early 1960s and between 1986 and 1992. The culprit was Bonamia exitiosus, a parasite that lives inside the oyster’s blood cells. Mullock reefs

Fishermen knew that the densest beds of oyster were associated with reefs of material known as mullock. Resembling coral, mullock reefs are built up from the skeletons of assorted bryozoans, shellfish, polychaete worms and sponges. They are common around New Zealand where strong currents flow through shallow channels, and they may stretch for several kilometres.

After 140 years of dredging, most mullock reefs in Foveaux Strait have been destroyed by heavy equipment, and few sites are available for young oysters to settle. The oyster population in the eastern Foveaux Strait has never recovered since the 1950s, and neither have the mullock reefs. Some environmentalists believe the fishery will collapse if destruction of the reefs continues. ^[82]

Juveniles congregate in sheltered inshore waters, e.g., estuarine areas, shallow mudflats and sandflats, where they remain for up to two years. Juvenile survival is highly variable. Flatfish move offshore for first spawning at 2–3 years of age during winter and spring. Adult mortality is high, with many flatfish spawning only once and few spawning more than two or three times. However, fecundity is high, e.g., from 0.2 million eggs to over 1 million eggs in sand flounders.^[83]

Recent work on the banding of statoliths from N. sloanii suggests that the animals live for around 1 year. Growth is rapid. Modal analysis of research data has shown increases of 3.0–4.5 cm per month for Gould's arrow squid measuring between 10 and 34 cm Dorsal Mantle Length (DML).

Estimated ages suggest that N. sloanii hatches in July and August, with spawning occurring in June and July. It also appears that N. gouldi may spawn one to two months before N. sloanii, although there are some indications that N. sloanii spawns at other times of the year. All squid taken by the fishery do not appear to have spawned.

Tagging experiments indicate that arrow squid can travel on average about 1.1 km per day with a range of 0.14–5.6 km per day.^[84]

Japanese boats began fishing for squid in New Zealand waters in 1969. New Zealand fishermen took up squid fishing a decade or so later, employing, at first, jigging techniques learnt from the Japanese. Jigging happens at night, when squid are lured to surface waters by powerful lights hung from boats, and are caught on spinning multi-barbed hooks attached to long lines. Most squid are now caught by trawling. Squid fishery

The New Zealand squid fishery is based on two closely related species of arrow squid (Nototodarus gouldi and Nototodarus sloanii). Both live for a year, growing rapidly to about 30 centimetres in length and just over 1 kilogram in weight. The fishery is concentrated around the South Island and the subantarctic Auckland Islands, and runs from February to May. The catch is highly variable, depending upon the survival rate of juvenile squid. Most of the squid is frozen and exported worldwide. Earnings were $86 million in 2002. ^[85]

Colossal Squid#Largest known specimen

The southern Māori tribe Ngāi Tahu had various uses for bull kelp, or rimurapa: the narrow stalk, connecting the holdfast to the blade, was fashioned into a flute; the blade was roasted and chewed; and wide blades were used as bags for preserving food. Māori made bags called pōhā by splitting open the blades and inflating them. They produced the bags in large quantities during summer in preparation for the muttonbirding season. Inflated blades were hung up to dry for several days, then deflated and rolled up.

In autumn the bags were taken to the islands around Stewart Island where muttonbirds, or tītī, were caught. They were filled with muttonbird chicks; an average-sized pōhā could hold up to 50 birds. When the bag was full, hot fat was poured over the birds and the top tied off to exclude air. Birds have been preserved for up to six years with this method.

Although not widely practised today, customary harvest of some seaweed species by Māori has continued and is recognised in legislation. The Ngai Tahu Claims Settlement Act 1998 protects bull kelp and karengo from commercial harvesting within the tribe’s traditional seaweed-gathering grounds.^[86]

Agar Agar is a by-product of some red seaweeds. An agar industry developed in New Zealand during the Second World War, when supplies from Japan dwindled. Agar was needed as a culture medium for growing bacteria and other micro-organisms, and also as a jelly for preserving the canned meat sent to soldiers overseas. In 1941 a young botanist, Lucy Moore, was directed by the Department of Scientific and Industrial Research to search for agar-producing seaweeds. She found vast quantities of Pterocladia lucida on the east coast of the North Island, and arranged for local children to collect and dry the seaweed. After hours of boiling in water, agar dissolved out of the fronds.

New Zealand agar proved to be of very high quality and has been commercially produced since 1943. Today most of the seaweed is collected from south Wairarapa and then sent to Ōpōtiki where the agar is extracted.

Seaweeds and shellfish farms Washed-up seaweed that is covered in tiny young mussels (mussel spat) is collected from Ninety Mile Beach in Northland and sent to mussel farms. In the 2001–2 fishing year, 250 tonnes of seaweed was harvested and transported to mussel farms in the Marlborough Sounds, where it was transferred to cultivation ropes.

Marine farmers harvested 300 tonnes of beach-cast and free-floating giant kelp in 2001–2 in order to feed young pāua (abalone). Karengo harvest

Karengo has been sustainably harvested from the Kaikōura coast since the mid-1980s. At first it was just sold locally, but eventually it was air-dried and milled into flakes for food seasoning, and made available around New Zealand. An annual average of 2.5 tonnes of karengo was collected in the 10 years to 2002. Future prospects

Two other important seaweed products are carrageenans and alginates. Like agar, these are jelly-forming chemicals. Carrageenans are useful thickeners, used in the food industry in syrups, custards, chocolates and yoghurts. They also appear in shampoos, toothpastes and body lotions. Alginates are used to make water-based products creamier, and are added to ice cream and other dairy products to stop ice crystals from forming. In dentistry, impressions of teeth are usually made on an alginate base. Alginates have applications in the paper and textile industries for coatings and dyeing.

Carrageenans and alginates are not commercially produced in New Zealand, although Gigartina, a carrageenan-producing seaweed, grows prolifically around the country, as does bull kelp, which has the highest alginate content of any seaweed.

With its long coastline and abundant seaweed resources, New Zealand has the potential for a thriving seaweed industry. However, the labour-intensive nature of harvesting and aquaculture has prevented the country from competing against bigger producers in Asia.^[87]

The most common whitebait species in New Zealand is the common galaxias or inanga, which lays its eggs during spring tides in Autumn on the banks of a river amongst grasses that are flooded by the tide. The next spring tide causes the eggs to hatch into larvae which are then flushed down to the sea with the outgoing tide where they form part of the ocean's plankton mass. After six months the developed juveniles return to rivers and move upstream to live in freshwater.

New Zealand whitebait are caught in the lower reaches of the rivers using small open-mouthed hand-held nets. Where the whitebait is more plentiful, set nets may be used adjacent to river banks.

Whitebaiting in New Zealand has a limited season enforced during the period that the whitebait normally migrate up-river. Strict control over net sizes and rules against blocking the river permit sufficient quantity of whitebait to reach the adult habitat and maintain stock levels. Whitebait are very sensitive to objects in the river and are adept at dodging nets.

New Zealand whitebait are small, sweet and tender. They are smaller and much more delicate than Chinese whitebait. The most popular way of cooking them is the whitebait fritter, which is essentially an omelette containing whitebait. Purists use only the egg white in order to minimise interfering with the taste of the bait.

Whitebait is very much a delicacy and is the most costly fish on the market. It can normally be purchased only during or close to the netting season. It is normally sold fresh in small quantities, although some is frozen to extend the sale period.

The combination of fishing controls, a limited season and the depletion of habitat as a result of forest felling during the era of colonisation results in limited quantities being available on the market. Some jurisdictions permit fishing of the adults but again under regulation or licence in order to preserve the adult population. Others ban it altogether unless the fisher is a Māori).

Pagrus auratus Snapper are demersal fish found down to depths of about 200 m, but are most abundant in 15–60 m. They are the dominant fish in northern inshore communities and occupy a wide range of habitats, including rocky reefs and areas of sand and mud bottom. They are widely distributed in the warmer waters of New Zealand, being most abundant in the Hauraki Gulf.

Snapper are serial spawners, releasing many batches of eggs over an extended season during spring and summer. The larvae have a relatively short planktonic phase which results in the spawning grounds corresponding fairly closely with the nursery grounds of young snapper. Young fish school in shallow water and sheltered areas and move out to deeper water in winter. The fish disperse more widely as they grow older. They first reach maturity from 20 to 28 cm fork length at 3–4 years of age. Large schools of snapper congregate before spawning and move on to the spawning grounds, usually in November-December. The spawning season may extend to January-March in some areas and years before the fish disperse, often inshore to feeding grounds. The winter grounds are thought to be in deeper waters where the fish are more widespread.

Water temperature appears to play an important part in the success of recruitment. Generally strong year classes in the population correspond to warm years, weak year classes correspond to cold years.

Growth rate varies geographically and from year to year. Snapper from Tasman Bay/Golden Bay and the west coast of the North Island grow faster and reach a larger average size than elsewhere. Snapper have a strong seasonal growth pattern, with rapid growth from November to May, and then a slowing down or cessation of growth from June to September. They may live up to 60 years or more and have very low rates of natural mortality. An estimate of M = 0.06 yr-1 was made from catch curves of commercial catches from the west coast North Island pair trawl fishery in the mid-1970s. These data were re-analysed in 1997 and the resulting estimate of 0.075 yr-1 has been used in the base case assessments for SNA 1, 2, and 7 (and SNA 8 up to 2004). In the 2005 assessment for SNA 8, natural mortality was estimated within the model.^[89]

The Australasian snapper or squirefish, Chrysophrys auratus, the only member of the genus Chrysophrys, is a species of porgie found in coastal waters of New Zealand and southern Australia. Although it is almost universally known in these countries as snapper it does not belong to the Lutjanidae family. It is highly prized as an eating fish.

The Māori people of New Zealand call the fish tamure.

The fish is found on all coasts of New Zealand, especially in the north. The fish spawn in inshore waters and live in rocky areas and reefs of up to 200 m deep. They school, and will migrate between reefs. Larger fish are known to enter estuaries and harbours.

Growth rates are quite slow, a 10 kg adult is probably 20 years old, and a fish at the maximum size of 1.3 m long and 20 kg is probably 50 years old. Sexual maturity is reached at about 30 cm long and a small percentage of the males will actually turn into females at puberty. Anglers are advised not to take immature fish, so as not to reduce breeding stock. Minimum sizes are supposed to be designed to allow these fish to participate in spawning runs at least once before they become available to the fishery, however given the slow growth rates of this species, there is need to consider area closures and/or further increasing the minimum sizes in each state to reduce the chances of growth overfishing ^[90] of the various populations of snapper throughout its range. This may be important with recent developments in technology such as the Global Positioning System GPS and fishing tackle developments such as scented fishing lures ^[91] like the squidgy pro range ^[92]which have been shown in laboratory and field testing to be particularly effective in catching snapper over traditional lure types and thus are an example of technology creep^[93] in fishing for this species.

For more information see Fishbase: Chrysophrys auratus

Hoplostethus atlanticus

Orange roughy otoliths have a marked transition zone in banding which is believed to be associated with first spawning (Francis & Horn 1997) (please refer to Plenary document for reference list). This has been used to estimate mean age at the onset of maturity, which ranges from 23 to 31.5 years for fish from various New Zealand fishing grounds (Horn et al. 1998, SeaFIC/NIWA unpublished data). Orange roughy in New Zealand waters reach a maximum size of about 50 cm standard length (SL), and 3.6 kg in weight. Their average size is around 35 cm SL, although there is some variation between areas. Fecundity is relatively low, with females carrying on average about 40 000–60 000 eggs. The eggs are large (2–3 mm in diameter), are fertilised in the water column, and then drift upwards towards the surface and remain planktonic until they hatch close to the bottom after about 10 days. Details of larval biology are poorly known.^[96]

The orange roughy is a deep-sea fish belonging to the slimehead family. This fish is categorized as vulnerable to exploitation by the Marine Conservation Society. It is found in cold (3 to 9 °C), deep (bathypelagic, 180 to 1,800 m) waters off New Zealand. The orange roughy is notable for its great age — a recorded (disputed by commercial fishers but supported by scientists) maximum of 149 years — and importance to commercial deep trawl fishery. Actually a bright brick red in life, the orange roughy fades to a yellowish orange after death.

Like other slimeheads, the orange roughy is slow-growing and late to mature, resulting in a very low resilience. They are extremely susceptible to overfishing because of this, the New Zealand stocks, which were first exploited in the late 1970s, have already crashed.

The orange roughy is the largest known species of slimehead at a maximum standard length (SL, a measurement excluding the tail fin) of 75 centimetres and a maximum weight of seven kilograms. However, the average commercial catch size is 30 to 40 cm SL.

Orange roughy are generally sluggish and demersal; they form aggregations with a population density of up to 2.5 fish per square meter. These aggregations form in and around geologic structures, such as undersea canyons and seamounts, where water movement and mixing is high — ensuring dense concentrations of prey items. The aggregations do not necessarily form for the purpose of spawning or feeding; it is thought that the fish cycle through metabolic phases (active or feeding and inactive or resting) and seek areas with ideal hydrologic conditions to congregate during their active and inactive phases. Observations made of orange roughy aggregations during submersible dives have also shown that the fish lose almost all pigmentation whilst inactive, during which time they are very approachable. Predators of orange roughies include large deep-roving sharks, cutthroat eels, merluccid hakes, and snake mackerels.

Orange roughy are very slow-growing, reaching maturity at 20 to 30 years of age.

The maximum published age of 149 years was determined via radiometric dating of trace isotopes found in an orange roughy's otolith ("ear bone"). Similarly, counting the growth rings of orange roughy otoliths has given a maximum age of 125 to 156 years. The validity of these results is questioned by commercial fishers as some state the former method is controversial and the latter method is known to underestimate age in older specimens. The issue has yet to be resolved definitively but carries important implications relating to the orange roughy's conservation status.

In recent years, the consumption of orange roughy has risen drastically due to increased supply through previously impossible deep-sea trawling techniques. Its recovery rate from fishing is slow because of its life cycle and sporadic reproduction making the fish incredibly prone to overfishing. It is the first commercially sought fish to be added to Australia's list of endangered species because of overfishing. ^[97] According to Seafood Watch, orange roughy is currently on the list of fish that American consumers who are health and sustainability minded should avoid.

The New Zealand Ministry of Fisheries tried to implement quotas for catches, but because of the underestimated slow-maturing nature of the orange roughy, the quotas have been reduced each year. However, the quotas may still be too high for the fisheries to be sustainable. Since the orange roughy is a valuable export, the Ministry of Fisheries has launched projects to study the fish. ^[98]

In addition to the dangers for the species, the method of bottom trawling has been heavily criticized by environmentalists for its destructive nature. The destructive nature of bottom trawling combined with the heavy commercial demand has garnered focused criticism from both environmentalists and media. ^[99]

slimeheads The larger species — namely the orange roughy (Hoplostethus atlanticus) and Darwin's slimehead (Gephyroberyx darwinii) — are the target of extensive commercial fisheries off Australia and New Zealand. Many populations have already crashed, while others are showing signs of severe overfishing; due to slimeheads' slow rate of reproduction, the future viability of these fisheries has been put into question. Orange roughies are food fish and are marketed fresh and frozen, whereas Darwin's slimeheads are utilised for their oil and made into fishmeal.

• 30 November 2007 - The orange roughy fishery is closed to allow stocks of the fish to recover. ^[100]

Maximum sustainable yield Unfortunately errors in estimating the population dynamics of a species can lead to setting the maximum sustainable yield too high (or too low). An example of this was the New Zealand Orange roughy fishery. Early quotas were based on an assumption that the orange roughy had a fairly short lifespan and bred relatively quickly. However, it was later discovered that the orange roughy lived a long time and had bred slowly (~30 years). By this stage stocks had been largely depleted.

Seamounts The main cause for the recent interest in seamounts is the discovery that they maintain large stocks of commercially important fishes and invertebrates. This began during the 1960s when Russia, Australia and New Zealand started to look for new stocks of fish and began to trawl the seamounts. The majority of the invertebrates brought up are corals, and are mainly used for the jewelry trade. The two major fish species were the orange roughy (Hoplostethus atlanticus) and pelagic armourhead (Pseudopentaceros wheeleri), which were quickly overexploited due to lack of knowledge of the longevity of the fish, late maturity, low fecundity, small geographic range and recuitment to the fishery. As well as the fishes being overexploited the benthic communities were destroyed by the trawling gear.

Orange roughy (Hoplostethus atlanticus) are trawled from depths of 700–1,000 metres and caught when they come together to spawn. The orange roughy was first reported from New Zealand waters in 1957, when it was given the unappealing name of ‘slimehead’. This was changed for marketing purposes when commercial quantities were taken in 1979. Catches peaked at around 54,000 tonnes in 1988–89. Since then new information about their biology has led to the imposition of quotas inside the New Zealand Exclusive Economic Zone. Most fish biologists now believe that orange roughy are long-lived (up to 150 years) and slow growing; fishing is being managed to take this into account. The biggest fishery is on the Challenger Plateau, while many areas on the Chatham Rise are no longer economic for fishing. There is concern that stocks are being over-fished.^[101]

A rough life: In the 1980s, when the orange roughy fishery was established, scientists knew little about the species. A decade later they had a better idea of its life history: "A typical orange roughy is probably at least 50–60 years old and has probably been dodging sharks, sperm whales and giant squids since it began life as a 2 mm egg drifting near the sea surface … Spawning is now interrupted by large factory trawlers; tens of thousands of individuals are headed and gutted".^[102]

Orange roughy lives in very cold, deep water, where there is no light. Fished from 600–1,500 metres beneath the surface, it is the deepest commercial fishery in the world. This remarkable fish has a life expectancy of up to 150 years. Its longevity and slow rate of breeding means that only small numbers can be harvested without affecting the size of the population. This was not known in the 1980s, and orange roughy seemed to be a boundless resource. On one occasion 54 tonnes were caught in only 20 minutes’ trawling – but this apparent abundance was an illusion, as the fish had been concentrated in spawning schools. Big catches were taken in the 1980s, but the boom years could not, and did not, last. The harvest peaked in 1989 at 54,000 tonnes, and has been in decline ever since. Popular in North American restaurants in the 1980s, by the 2000s orange roughy was scarce in New Zealand and commercial quotas were only a fraction of those in the 1980s. Partly this was due to the stocks being fished down for too long when populations were overestimated. Current harvest levels may be about right, or may still be too high, or may even increase slightly once over-fished stocks are re-established.^[103]

Environment:        bathypelagic; oceanodromous (Ref. 51243); marine; depth range 180 – 1809 m

Climate: deep-water; 3 – 9°C; 65°N - 56°S, 84°W - 168°W Importance: fisheries: highly commercial; price category: medium; price reliability: reliable: based on ex-vessel price for this species Resilience: Very low, minimum population doubling time more than 14 years (K=0.04-0.06; tm=5-33; tmax=140; Fec=10,000) Vulnerability: High to very high vulnerability (73.97), based on Lmax and K (Ref. 59153) Distribution: Gazetteer Western Atlantic: Gulf of Maine (Ref. 4784) [in error according to Moore (Fishes of the Gulf of Maine, in press), should be off northern Nova Scotia]. Eastern Atlantic: Iceland to Morocco; Walvis Bay, Namibia to off Durban, South Africa. Indo-Pacific: south-central Indian Ocean and New Zealand. Eastern Pacific: Chile (Ref. 27363). Several stocks may exist as suggested by distinct spawning sites and seasons. Morphology: Dorsal spines (total): 4 - 6; Dorsal soft rays (total): 15 - 19; Anal spines: 3; Anal soft rays: 10 – 12. Bright brick-red in color, mouth and gill cavity bluish black (Ref. 4181). Ventral scutes: 19-25. Biology: Inhabits deep, cold waters over steep continental slopes, ocean ridges and sea-mounts. Shallow range of usual occurrence from Ref. 27121. Appears to be dispersed over both rough bottoms and steep, rough grounds where it feeds on crustaceans and fish. In New Zealand, the main prey include mesopelagic and benthopelagic prawns, fish, and squid, with other organisms such as mysids, amphipods and euphausiids occasionally being important (Ref. 9072). Juveniles feed mainly on crustaceans (Ref. 27075, 27076). Grows very slowly and is one of the longest lived fish species known. Based on parasite and trace-element analyses, orange roughy is a sedentary species with little movement between fish-management zones (Ref. 27089). Little is known of the larvae and juveniles which are probably confined to deep water (Ref. 27088). The fishery targets sporadically formed dense spawning and non-spawning aggregations. Marketed fresh and frozen; eaten steamed, fried, microwaved and baked (Ref. 9988). Because of severe overfishing the species has been listed as threatened by the Australian Government in 2006.^[104]

eat and eaten by

Kahawai feed mainly on fishes but also on pelagic crustaceans, especially krill (Nyctiphanes australis). Kahawai smaller than 100 mm mainly eat copepods. Although kahawai are principally pelagic feeders, they will take food from the seabed.

spawning

The spawning habitat of kahawai is unknown but is thought to be associated with the seabed in open water. Schools of females with running ripe ovaries have been caught by bottom trawl in 60–100 m in Hawke Bay (Jones et al., 1992). Other females with running ripe ovaries have been observed in east coast purse seine landings sampled in March and April 1992, and between January and April in 1993 (McKenzie, NIWA, unpublished data). Length-maturation data collected from thousands of samples in early 1990s suggest the onset of sexual maturity in males occurs at around 39 cm and in females at 40 cm (McKenzie, NIWA, unpublished data). This closely matches an estimate of 39 cm used for Australian A. trutta (Morton et al., 2005). This length roughly corresponds to fish of four years of age in both countries. Eggs have been found in February in the outer Hauraki Gulf. Juvenile fish (0+ year class) can be found in shallow water over eelgrass meadows (Zostera spp.) and in estuaries.

age

Kahawai are usually aged using otoliths, following an aging technique that has been validated (Stevens and Kalish, 1998). Kahawai grow rapidly, attaining a length of around 15 cm at the end of their first year, and maturing after 3–5 years at about 35–40 cm, after which their growth rate slows. The longest recorded A. trutta had a fork length of 79 cm and was caught by a recreational fisher in the Waitangi Estuary, in Hawke Bay in August 1997 (Duffy & Petherick, 1999). Northern kahawai, Arripis xylabion, grow considerably bigger than kahawai and attain a maximum length of at least 94 cm, but beyond this, little is known about the biology of A. xylabion. Male and female von Bertalanffy growth curves appear to be broadly similar, with females attaining a slightly higher value for L ¥ , although statistical comparison of sex specific curves using a likelihood ratio test (Kimura, 1980) suggests that they are statistically different (Hartill & Walsh, 2005). Combined-sex growth curves are probably adequate for modelling purposes and are provided for some areas in Table 8. Sex specific growth parameters given for KAH 1 in previous plenary documents have higher estimates for L50 (56.93 for males and 55.61 for females). The maximum recorded age of kahawai is 26 years. The instantaneous rate of natural mortality (M) was estimated from the equation M=loge 100/maximum age, where maximum age is the age to which 1% of the population survives in an unexploited stock. Based on a maximum age of 26 years, M was estimated to equal 0.18. A range of 0.15-0.25 has previously been assumed to reflect the lack of precision in the estimate.^[106]

Although the kahawai (Arripis trutta) is sometimes called sea trout or sea salmon, its resemblance to trout or salmon is only superficial. The average size is 40–50 centimetres. The fish group together according to size, and schools of juveniles 20–35 centimetres long are quite common. Kahawai live in open coastal waters throughout New Zealand, but are more common around the North Island. They seldom venture more than 20 kilometres offshore. Adults eat crustaceans and small fish, juveniles feed on plankton. In turn, they are prey for orcas, bottlenose dolphins, kingfish and bronze whaler sharks. An important commercial species since the 1970s, kahawai are also sought by recreational anglers for their fighting qualities. The flesh has not always been considered the best eating, but if the fish are bled and kept cool they yield good-quality fillets, and taste delicious when prepared in a smoker.^[107]

• Fishbase: Arripis trutta (Eastern Australian salmon)|}
• Fishbase: Arripis xylabion (Northern kahawai)

spawning

Barracouta spawn mainly in late-winter/spring (August-September) on the east and west coasts of both of the main islands, and in late spring (November-December) in Southland and in the Chatham Islands. Some spawning activity may also extend into summer/autumn. Sexual maturity is reached at about 50–60 cm fork length (FL) at about 2–3 years of age.

occurrence

Juvenile barracouta have been recorded from inshore areas (< 100 m) all around New Zealand and the Chatham Islands, although they appear to be less common on the west coast of the South Island. Adult fish are found out to about 400 m depth. Tagged barracouta have moved considerable distances to spawn (up to 500 nautical miles).

age and size

There are no age data available prior to the onset of commercial fishing, which developed rapidly from 1968. Ageing studies carried out in the mid-1970s showed that the maximum age rarely exceeded 10 years. Data have been validated for fish up to 3 years old by following modal progressions over time.

M was estimated using the equation M = loge100/maximum age, where maximum age is the age to which 1% of the population survives in an unexploited stock. Using 10 years for the maximum age suggests an M of up to 0.46. The effect of fishing on age structure prior to the mid-1970s is unknown, but M is unlikely to be less than 0.3, which has been assumed in previous stock assessments.^[110]

• Fishbase: Thyrsites atun (Snoek)

Pseudocaranx dentex Trevally are both pelagic and demersal in behaviour. Juvenile fish up to 2 years old are found in shallow inshore areas including estuaries and harbours. Young fish enter a demersal phase from about 1 year old until they reach sexual maturity. At this stage adult fish move between demersal and pelagic phases. Schools occur at the surface, in mid-water and on the bottom, and are often associated with reefs and rough substrate. Schools are sometimes mixed with other species such as koheru and kahawai. The occurrence of trevally schools at the surface appears to correlate with settled weather conditions rather than with a specific time of year.

Surface schooling trevally feed on planktonic organisms, particularly euphausids. On the bottom, trevally feed on a wide range of invertebrates.

Trevally are known to reach in excess of 40 years of age. The growth rate is moderate during the first few years, but after sexual maturity at 32 to 37 cm fork length (FL), the growth rate becomes very slow. The largest fish are typically around 60 cm FL and weigh about 4.5 kg, however much larger fish of 6–8 kg are occasionally recorded.

Fecundity is relatively low until females reach about 40 cm FL. They appear to be partial spawners, releasing small batches of eggs over periods of several weeks or months during the summer.^[112]

occurrence

Hoki are widely distributed throughout New Zealand waters from 34o S to 54o S, from depths of 10 m to over 900 m, with greatest abundance between 200 and 600 m. Large adult fish are generally found deeper than 400 m, while juveniles are more abundant in shallower water. In the January 2003 Chatham Rise trawl survey, exploratory tows with mid-water gear over a hill complex east of the survey area found low density concentrations of hoki in mid-water at 650 m over depths of 900 m or greater in January 2003 (Livingston et al., 2004). The proportion of larger hoki outside the survey grounds is unknown. Commercial data also indicate that small catches of older hoki are targeted over other hill complexes outside the survey areas of both the Chatham Rise and Sub-Antarctic (Dunn & Livingston, 2004), and are also caught as a bycatch by tuna fishers over very deep water (Bull & Livingston, 2000).

spawning

The two main spawning grounds on the WCSI and in Cook Strait are assessed as two separate stocks, based on the geographical separation of these spawning grounds and a number of other factors. Hoki migrate to spawning grounds in Cook Strait, WCSI, Puysegur, and ECSI areas in the winter months. Throughout the rest of the year the adults are dispersed around the edge of the Stewart and Snares shelf, over large areas of the Sub-Antarctic and Chatham Rise, and to a lesser extent around the North Island. Juvenile fish (2–4 yrs) are found on the Chatham Rise throughout the year. Hoki spawn from late June to mid-September, releasing multiple batches of eggs. They have moderately high fecundity with an average sized female of 90 cm TL spawning over 1 million eggs in a season (Schofield and Livingston 1998). Not all hoki within the adult size range spawn in a given year. Winter surveys of both Chatham Rise and Sub-Antarctic have found significant numbers of large hoki with no gonad development, at times when spawning is occurring in other areas. Histological studies of female hoki in the Sub-Antarctic in May 1992 and 1993 estimated that 67% of hoki age 7 years and older in the Sub-Antarctic would spawn in winter 1992, and 82% in winter 1993 (Livingston et al., 1997). A similar study repeated in April 1998 found that a much lower proportion (40%) of fish age 7 and older was developing to spawn (Livingston & Bull, 2000). Unlike in 1992 and 1993, the 1998 study was not preceded by a summer survey to allow estimation of the numbers of fish already departed from the Sub-Antarctic survey area. Further, the timing of this survey was a month earlier than either 1992 or 1993, and may therefore have underestimated the proportion spawning in 1998 (Livingston & Bull, 2000). A recent histological study of female hoki from the Sub-Antarctic in November–December of 2002 to 2004 (using a different methodology) estimated a higher proportion of hoki had spawned in the previous season (Grimes & O’Driscoll, 2006). These results and the methodology are being reviewed in 2007.

The main spawning grounds are centred on the Hokitika Canyon off the WCSI and in Cook Strait Canyon. The planktonic eggs and larvae move inshore by advection or upwelling (Murdoch, 1990; Murdoch, 1992) and are widely dispersed north and south with the result that 0+ and 1‑year‑old fish can be found in most coastal areas of the South Island and parts of the North Island. The major nursery ground for juvenile hoki aged 2–4 years is along the Chatham Rise, in depths of 200 to 600 m. The older fish disperse to deeper water and are widely distributed on both the Sub-Antarctic and Chatham Rise. Analyses of trawl survey (1991-2002) and commercial data suggests that a significant proportion of hoki move from the Chatham Rise to the Sub-Antarctic as they approach maturity, with most movement between ages 3 and 7 years (Bull & Livingston, 2000; Livingston et al., 2002). Based on a comparison of Tangaroa trawl survey data, on a proportional basis (assuming equal catchability between areas), 80% or more of hoki aged 1–2 years occur on the Chatham Rise. Between ages 3 and 7, this drops to 60–80%. By age 8, 35% or less fish are found on the Chatham Rise compared with 65% or more in the Sub-Antarctic. A study of the observed sex ratios of hoki in the two spawning and two non-spawning fisheries found that in all areas, the proportion of male hoki declines with age (Livingston et al., 2000). There is little information at present to determine the season of movement, the exact route followed, or the length of time required, for fish to move from the Chatham Rise to the Sub-Antarctic. Bycatch of hoki from tuna vessels following tuna migrations from the Sub-Antarctic showed a northward shift in the incidence of hoki towards the WCSI in May–June (Bull & Livingston, 2000). The capture of net-damaged fish on Pukaki Rise following the WCSI spawning season where there had been intense fishing effort in 1989 also provides circumstantial evidence that hoki migrate from the WCSI back to the Sub-Antarctic post-spawning (Jones, 1993).^[127]

age and size

Growth is fairly rapid with juveniles reaching about 27–35 cm TL at the end of the first year. There is considerable variability in growth rates in subsequent years and there has been a trend of increasing size at age in data from both the trawl surveys and the commercial catch since 1983. In the past, hoki reached about 45, 55 and 60–65 cm TL at ages 2, 3, and 4 respectively. More recently, length modes have been centred at 45–50, 60–65, and 70–75 cm TL for ages 2, 3, and 4. Although smaller spawning fish are taken on the spawning grounds, males appear to mature mainly from 60‑65 cm TL at 3–5 years, while females mature at 65–70 cm TL. From the age of maturity the growth of males and females differs. Males grow up to about 115 cm TL, while females grow to a maximum of 130 cm TL and up to 7 kg weight. Horn & Sullivan (1996) estimated growth parameters for the two stocks separately. Fish from the eastern stock sampled in Cook Strait are smaller on average at all ages than fish from the WCSI. Maximum age is from 20-25 years, and the instantaneous rate of natural mortality in adults is about 0.25 to 0.3 per year.

There is evidence that ageing error causes problems in the estimation of year class strength. For example, the 1989 year class appeared as an important component in the catch at age data at older ages, yet this year class is believed to have been extremely weak in comparison to the preceding 1988 and 1987 year classes. A new ageing protocol has been developed to increase the consistency of hoki age estimation. This has been applied to the survey data from 2000 onwards and to catch samples from 2001 (Francis, 2001). Data from earlier samples, however, are still based on the original methodology and otolith readings.^[128]

In New Zealand, hoki (Macruronus novaezelandiae) are typically trawled from depths of 200–800 metres. Between 1990 and 1995, catches averaged a staggering 200,000–240,000 tonnes annually. Hoki, also known as blue grenadier, is now New Zealand’s most valuable export fish.^[129]

The deep-sea fish hoki, also known as blue hake or blue grenadier, is one of New Zealand’s biggest fish exports. Hoki fishing began in the Tasman Sea, but has expanded to include Cook Strait, the Chatham Rise and subantarctic waters. In the decade to 2002 the annual quota for the catch was 200,000 tonnes. In 2004 the Tasman Sea stock was estimated to be down to about 13% of the biomass before fishing developed in 1972, with a warming trend in the Tasman likely to be a contributing factor. The quota was reduced to 180,000, then to 100,000 tonnes in 2004. ^[130]

age and size

Ling live to a maximum age of about 30 years. A growth study of ling from five areas (west coast South Island, Chatham Rise, Bounty Plateau, Campbell Plateau, and Cook Strait) showed that females grew significantly faster and reached a greater size than males in all areas, and that growth rates were significantly different between areas. Ling grow fastest in Cook Strait and slowest on the Campbell Plateau.

M was estimated from the equation M = loge100/maximum age, where maximum age is the age to which 1% of the population survives in an unexploited stock. The mean M calculated from 5 samples of age data from the Chatham Rise and Campbell Plateau was 0.18 (range = 0.17–0.20). A likely minimum value of M = 0.15 was calculated using a maximum age of 30 years. Less than 0.2% of successfully aged ling have been older than 30 years.

spawning

Ling in spawning condition have been reported in a number of localities throughout the EEZ. Time of spawning appears to vary between areas: July to November on the Chatham Rise; September to December on Campbell Plateau and Puysegur Bank; September to February on the Bounty Plateau; July to September off west coast South Island and in Cook Strait. Little is known about the distribution of juveniles until they are about 40 cm total length, when they begin to appear in trawl samples over most of the adult range.

occurrence

Ling appear to be mainly bottom dwellers, feeding on crustaceans such as Munida and scampi and also on fish. However, they may at times be caught well above the bottom, for example when feeding on hoki during the hoki spawning season.^[133]

eat and eaten by

spawning

age and size

value as food

Hake

age and size

The New Zealand hake reach a maximum age of at least 25 years. Males, which rarely exceed 100 cm total length (TL), do not grow as large as females, which can grow to 120 cm TL or more. Both sexes reach sexual maturity between 6 and 10 years of age, at lengths of about 67–75 cm TL (males) and 75–85 cm TL (females). Colman (1998) suggested that hake reached 50% maturity at between 6–8 years for HAK 1, and 7–8 years for HAK 4.

Horn (1997) validated the use of otoliths to age hake. Readings of otoliths have been used in age-length keys to scale length frequency distributions for hake collected from trawl surveys in HAK 1 and HAK 4 and from commercial vessels in the HAK 4 fishery to produce catch at age distributions.

Estimates of natural mortality (M) and the associated methodology are given in Dunn et al. (2000); M is estimated as 0.18 y-1 for females, and as 0.20 y-1 for males. Colman et al. (1991) previously estimated M as 0.20 y-1 for females and 0.22 y-1 for males using the maximum age method of Hoenig (1983) (the maximum ages at which 1% of the population survives in an unexploited stock were estimated at 23 years for females and 21 years for males). These are similar to the values proposed by Horn (1997), who determined the age of hake by counting zones in sectioned otoliths and concluded that M was likely to be in the range of 0.20–0.25 y-1.

Data collected by observers on commercial trawlers and data from trawl surveys suggest that there are at least three main spawning areas for hake (Colman, 1998). The best known area is off the west coast of the South Island, where the season can extend from June to October, usually with a peak in September. Spawning also occurs to the west of the Chatham Islands during a prolonged period from at least September to January. Spawning on the Campbell Plateau, primarily to the north-east of the Auckland Islands, occurs from September to February with a peak in September–October. Spawning fish have been recorded occasionally on the Puysegur Bank, with a seasonality that appears similar to that on the Campbell Plateau (Colman, 1998).

Juvenile hake have been taken in coastal waters on both sides of the South Island and on the Campbell Plateau. They reach a length of about 15–20 cm total length at one year old, and about 35 cm total length at 2 years (Colman, 1998).^[134]

Spawning occurs from late October to at least December and is widespread on the south Chatham Rise. Mean length at maturity for females, estimated from Chatham Rise trawl surveys (1986–87, 1990, 1991–93) using macroscopic gonad staging, is 34 cm TL.

They appear to have a pelagic juvenile phase, but little is known about this phase because only about 12 fish less than 21 cm TL have been caught. The pelagic phase may last for 4–5 years to lengths of 21–26 cm TL.

Unvalidated age estimates were obtained for Chatham Rise and Puysegur-Snares fish in 1995 and 1997 respectively using counts of the zones (assumed to be annual) observed in thin sections of otoliths. These estimates indicate that black oreo is slow growing and long lived. Maximum estimated age was 153 years (45.5 cm TL fish). Australian workers used the same methods, i.e., sections of otoliths, and reported similar results.

A von Bertalanffy growth curve was fitted to the Puysegur samples only. Estimated age at maturity for females was 27 years.

A first estimate of natural mortality (M), 0.044 (yr-1), was made in 1997 using the Puysegur growth data only. This estimate is uncertain because it appeared that the otolith samples were taken from a well fished part of the Puysegur area.

Black oreo appear to settle over a wide range of depths on the south Chatham Rise, but appear to prefer to live in the depth interval 600–800 m that is often dominated by individuals with a modal size of 28 cm TL.

Note: Oreo was introduced into the QMS as a species grouping consisting of three species of oreo - smooth, black, and spiky. No TAC, TACC and allowances have been set for smooth and black oreo individually and all catch and allowance data relates to the three oreo species combined.^[135]

Oreo (smooth)

Pseudocyttus maculatus Occur from 650 to about 1500 m depth. The geographical distribution south of about 45° S is not well known. It is a southern species and is abundant on the south Chatham Rise, along the east coast of the South Island, the north and east slope of Pukaki Rise, the Bounty Platform, the Snares slope, Puysegur Bank and the northern end of the Macquarie Ridge. They probably occur right round the slope of the Campbell Plateau.

Spawning occurs from late October to at least December and is widespread on the south Chatham Rise in small aggregations. Mean length at maturity for females, estimated from Chatham Rise trawl surveys (1986–87, 1990, 1991–93) using macroscopic gonad staging, is 40 cm TL.

They appear to have a pelagic juvenile phase, but little is known about this phase because only about six fish less than 16 cm TL have been caught. The pelagic phase may last for 5–6 years to lengths of 16–19 cm TL.

Unvalidated age estimates were obtained for Chatham Rise and Puysegur-Snares fish in 1995 and 1997 respectively using counts of the zones (assumed to be annual) observed in thin sections of otoliths. These estimates indicate that smooth oreo is slow growing and long lived. Maximum estimated age was 86 years (51.3 cm TL fish). Australian workers used the same methods, i.e., sections of otoliths, and reported similar results.

A von Bertalanffy growth curve was fitted to the age estimates from Chatham Rise and Puysegur-Snares fish combined and the parameters estimated for the growth curve are in Table 1. Estimated age at maturity for females was 31 years.

An estimate of natural mortality, 0.063 (yr-1), was made in 1997. The estimate was from a moderately exploited population of fish from the Puysegur region. The Puysegur fishery started in 1989–90 and by August-September 1992 (when the otoliths were sampled) about 24% of the smooth oreo catch from 1989–90 to 1995–96 had been taken. Future estimates of M should, if possible, be made from an unexploited population.

There are concentrations of recently settled smooth oreo south and south west of Chatham Island, although small individuals (16–19 cm TL) occur widely over the south Chatham Rise at depths of 650–800 m.^[136]

The age and length at recruitment to the fishery varies between areas and between years. In the northern SSRUs (88.1A–88.1G), toothfish recruit at a length of about 130 cm to the fishery. In the southern SSRUs the length at recruitment depends on the depth of fishing. In some years fish have been fully recruited by about age 7–8, whereas in other years fish have not been fully recruited until at least age 10. During the 2006 season, sub adult fish (with a mode at 60–70 cm) were recorded from the continental slope (1000–1500 m) in Subarea 88.2.

Details of the age and length of maturity and the timing of the spawning cycle are poorly known because the area is covered by ice for at least six months of the year. The smallest females with maturing ovaries are 90–100 cm TL. However, the proportion of these maturing females at length is currently unknown and so the maturity ogive has not yet been determined. Spawning is believed to be quite protracted starting in late May, peaking during the winter months, and probably extending into October/November. However, spawning may not be highly synchronised because small numbers of running ripe females have also been caught from December through April. Fish in the northern SSRUs appear to be more sexually advanced at any time of the year.

M was estimated by Dunn et al. (2006) using the methods of Chapman-Robson (1960), Hoenig (1983), and Punt et al. (2005). Estimates of M derived from these methods ranged from 0.11 to 0.17. After a consideration of possible biases Dunn et al. (2006) proposed that a value of 0.13 be used for stock modelling, with a range of 0.11–0.15 for sensitivity analyses. They noted that further work is required on values of M and in possible changes of M with age. Biological parameters relevant to the stock assessment are shown in Table 3 (available in 2007 Plenary Doc).

Antarctic toothfish feeds on a wide range of prey but is primarily piscivorous. The most important prey species of fish caught in the main fishery is Whitson’s grenadier (Macrourus whitsoni). In continental slope waters, M. whitsoni, the icefish Chionobathyscus dewitti, eel cods (Muraenolepis spp.) and cephalopods predominate in the diet, while on oceanic seamounts M. whitsoni, violet cod (Antimora rostrata) and cephalopods are important. In the coastal waters around McMurdo Sound, adults feed principally on Antarctic silverfish (Pleuragramma antarcticum). In the coastal waters around McMurdo Sound, adults feed principally on Antarctic silverfish (Pleuragramma antarcticum). In the open oceanic waters, Antarctic toothfish feed on small squid. The diet of Antarctic toothfish also varies with fish size. Crustaceans are more common prey items in smaller toothfish, whereas squid are more common in larger toothfish. Its main predators are likely to be cetaceans (sperm whales, killer whales), pinnipeds (Weddell seals), and colossal squid.

A hypothetical life history for D. mawsoni in the Ross Sea was developed by Hanchet al. (2007b). It is believed that they spawn to the north of the Antarctic continental slope, mainly on the ridges and banks of the Pacific-Antarctic Ridge. The spawning appears to take place during winter and spring, and may extend over a period of several months. Depending on the exact location of spawning, eggs and larvae become entrained by the Ross Sea gyres (a small clockwise rotating western gyre located around the Balleny Islands and a larger clockwise rotating eastern gyre covering the rest of 88.1 and 88.2), and may either move west settling out around the Balleny Islands and adjacent Antarctic continental shelf, south onto the Ross Sea shelf, or eastwards with the eastern Ross Sea gyre settling out along the continental slope and shelf to the east of the Ross Sea in Subarea 88.2. As the juveniles grow in size they move west back towards the Ross Sea shelf and then move out into deeper water (greater than 600m). The fish gradually move northwards as they mature, feeding in the slope region in depths of 1000–1500 m, where they gain condition before moving north onto the Pacific- Antarctic ridge to start the cycle again. Spawning fish may remain in the northern area for up to 2–3 years. They then move southwards back onto the shelf and slope where productivity is higher and food is more plentiful where they regain condition before spawning.^[137]

Antarctic cod: The Antarctic Cod is famous for producing antifreeze glycoprotein that allows it to survive in the ice-laden waters of the Southern Ocean surrounding Antarctica. Also called the Antarctic toothfish, with a heartbeat once every six seconds, research involving Antarctic cod may lead to advances in cardiac medicine involving conditions where human hearts beat slowly during certain medical procedures or fail to beat fast enough due to hypothermia.

Despite its name, the Antarctic Cod is quite unrelated to the true cod; it is not even in the same order, being classified as a perciform rather than a gadiform.

These large fish are probably mesopelagic and have been caught in waters deeper than 2000 meters. Fully grown, these grayish fish are among the biggest in the Antarctic, adults of more than 2 meters in length and weighing over 135 kg (300 lb/21.3 st) have been recorded during New Zealand research work carried out in the Ross Sea. The flesh is white with a high oil content. The taste is said to be similar to cod, which led to the common name Antarctic Cod. Their primary predators are the Weddell seal, the leopard seal, large squid, and Orca. They are closely related to, and sometimes confused with the Patagonian toothfish, Dissostichus eleginoides.

Its distribution range is generally below 65 degrees South. It is mainly caught in the Ross Sea in the austral summer but has also been recorded from Antarctic coastal waters south of the Indian Ocean sector, in the vicinity of the Antarctic peninsula, and near the South Sandwich Islands. Antarctic toothfish is managed by CCAMLR the Convention for the Conservation of Antarctic Marine Living Resources. (CCAMLR) has limited fishing to a precautionary catch level in the Ross sea, fishing takes place with the aim of collecting sufficient biological and stock size information to effectively manage this fishery in the future.

Despite these new acts, unregulated and illegal fishing, particularly of Patagonian toothfish (marketed as Chilean Sea Bass in the U.S.), remains a serious problem. The illegal fishing of toothfish has been increasing, with estimates of 32,000 tonnes (35,300 short tons) in 2000.^[138][139]

The Patagonian toothfish (Dissostichus eleginoides) lives in waters south of the New Zealand subantarctic islands. To increase marketing appeal it was renamed Chilean sea bass. It grows to just over 2 metres long and 100 kilograms in weight, and can fetch a high price in Japan and the United States. The fish were originally trawled, but longlines are now used for adult fish. As a result many seabirds become entangled in the lines. Most fishing occurs at depths between 400 and 1,500 metres. Poaching of these valuable fish in Australian and other waters may threaten the viability of the fishery. Populations typically survive 2–3 years of harvesting before the fishery collapses. In 2004 the New Zealand government recommended a plan of action to stop illegal, unregulated and unreported fishing of the species.^[140]