Atlantic menhaden

Atlantic menhaden
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Clupeiformes
Family: Clupeidae
Subfamily: Alosinae
Genus: Brevoortia
Species: B. tyrannus
Binomial name
Brevoortia tyrannus
(Latrobe, 1802)

The Atlantic menhaden (Brevoortia tyrannus) is a North American species of fish in the herring family, Clupeidae.[1]

Atlantic menhaden are found in the North Atlantic coastal and estuarine waters from Nova Scotia south to northern Florida. They are commonly found in all salinities of the Chesapeake Bay and Mid-Atlantic water. They swim in large schools that stratify by size and age along the coast. Younger and smaller fish are found in the Chesapeake Bay and southern coastline while older, larger fish are found along the northern coastline.[2]

Characteristics

Atlantic menhaden are silvery coloured fishes characterized by a moderately compressed body and a black spot on their shoulder behind their gill openings. They can reach a size of approximately 15 inches.[2]

Biology

Diet

Atlantic menhaden are filter feeders, meaning that they collect food by filtering water through modifications of the branchial apparatus (gill arches and gill rakers). Atlantic menhaden’s diet depends on the size of their gill rakers, which change as menhaden age. When the rakers are smaller, which generally correspond to when they are under the age of 1, Atlantic menhaden feed primarily on phytoplankton. As they age and their gill rakers grow larger, menhaden shift their diet to primarily consume zooplankton.[3]

Life cycle

Atlantic menhaden can spawn year round in inshore waters off the Atlantic coast, with the highest spawning rates near North Carolina in the late fall. The eggs hatch in the open ocean and the larvae drift to sheltered estuaries via ocean currents. The young spend a year developing in these estuaries before returning to the open ocean. At this early stage, they are commonly known as "peanut bunker". Atlantic menhaden usually do not become sexually mature until the end of their second year, after which they reproduce until death. A young, sexually mature female can produce roughly 38,000 eggs, while a fully mature female can produce upwards of 362,000.[4]

Eggs are buoyant and hatch within 2 to 3 days depending on the temperature. The larvae will spend 1 to 3 months in waters over the continental shelf. The Chesapeake Bay is a popular nursery for juvenile menhaden. Larval fish will enter the Bay in late winter and early summer. The larval fish will move into lower salinity waters in estuarine tributaries while juvenile and immature fish remain in the Bay until the fall. Atlantic menhaden can live up to 10 to 12 years.[2]

Predators

Atlantic menhaden are preyed upon by fish such as striped bass, weakfish and bluefish, and by birds such as ospreys and eagles.[5] Humpback whales off the coast of New Jersey feed on Atlantic menhaden.[6][7] Other cetaceans, such as fin whales and dolphins also eat menhaden.[8][9][10][11][12] Dolphins can eat up to 20 pounds of Atlantic menhaden a day.[13]

Fisheries and management

Historical uses

Menhaden have historically been used as a fertilizer for crops. It is likely that menhaden is the fish that Squanto taught the Pilgrims to bury alongside freshly planted seeds as fertilizer. Other uses for menhaden include: feed for animals, bait for fish, oil for human consumption, oil for manufacturing purposes and oil as a fuel source.

In the early years of the United States, Atlantic menhaden were being harvested by thousand of ships of fishermen. The Atlantic coastline was lined with processing facilities to quickly transform the fish into a product of worth, typically oil but later fish meal became more popular. Tragedy of the commons set in and the menhaden population began to dwindle. Many of these small companies could not manage, which left only a handful of menhaden fishing companies to remain on the Atlantic coast.[14]

While many sources today claim that the menhaden is inedible, the fish were once consumed as sardines might be, or fried. Maine fisherman, for example, would eat fried pogies for breakfast. The fish that were not sold for bait would be sold to the poorer classes for food.

Commercial fishery

In the Atlantic, menhaden are targeted by two types of fisheries, a reduction fishery and a bait fishery.

The reduction fishery processes whole menhaden into fish meal, fish oil, and fish solubles while the bait fishery supplies fishermen with menhaden as bait for key commercial and recreational fisheries. Both menhaden fisheries use a process known as purse seine fishing, in which two fishing boats surround a single school of fish with a large net. Purse seining is one of the most efficient methods of fishing available, with one of the lowest levels of bycatch.[15] The UN Food and Agriculture Organization has cited the Atlantic and Gulf menhaden fisheries as having one of the lowest levels of bycatch in the world.[16] The reduction fishery is largely based in the Chesapeake Bay and nearby Atlantic waters, and its season runs annually starting in May through the fall.

The bait fishery operates throughout the Atlantic coastline, ranging from North Carolina to New England.[17] Cast nets are also used for bait catch in the recreational fishing sector.

The fishery’s sustainability has also been certified by independent organizations. Friend of the Sea, an international seafood sustainability certification program, has recognized both the Atlantic menhaden and Gulf menhaden fisheries as sustainable.[18] This is both due to the healthy status of the stock as well as the fishery’s low levels of bycatch, which it achieves with the use of purse seine nets.[19]

Management

Atlantic menhaden are managed by the Atlantic States Marine Fisheries Commission (ASMFC), an interstate compact formed under an agreement by the 15 Atlantic coast states. Like with other species, the ASMFC manages menhaden to prevent overfishing and to keep the stock from being overfished. There is a subtle but distinct difference between the two designations. Overfishing occurs when too many fish are being taken from the population of a fish stock. A stock is considered overfished when it is not able to produce enough new fish to maintain the population.

The ASMFC uses two biological measurements, or reference points, to measure the health of the menhaden stock. To determine if the stock is overfished, the ASMFC measures fecundity (FEC), the number of mature eggs in the menhaden population, which indicates the stock’s reproductive capability. To measure overfishing, the ASMFC monitors fish mortality (F), the measure of the amount of fish removed from the water. In 2010, the ASMFC’s stock assessment found that the stock’s mortality levels were high enough that overfishing was occurring, but its fecundity level indicated that it was not overfished.[20]

Because the ASMFC’s 2010 assessment concluded that Atlantic menhaden was experiencing overfishing, some environmental organizations began campaigning for the Commission to impose new harvest restrictions, and the ASMFC began the process of drafting new limits. This culminated in a 2012 amendment to the menhaden Fishery Management Plan that reduced the coastwide Atlantic menhaden harvest by 20 percent of the average landings from 2009-2011.[21]

The cuts followed a sustained campaign by environmental groups like the Pew Charitable Trusts and the Chesapeake Bay Foundation, as well as authors like Paul Greenberg, who called for a ban on fishing menhaden in US federal waters and the Chesapeake Bay. The decision was opposed by many working in the menhaden fishery, who considered the cuts unnecessary and economically harmful.

These regulations joined older restrictions, such as a harvest cap on the number of menhaden that can be caught in the Chesapeake Bay, that were implemented to address concerns of localized depletion. Despite these concerns, there is currently no evidence that localized depletion is occurring in the Chesapeake Bay.[22]

Critics have since evaluated several claims made about the status of menhaden during the development of the 2012 management measures. For example, claims about historic overfishing of menhaden made by the Pew Charitable Trusts were rated “mostly false” by the non-partisan fact-checking organization Politifact.[23]

Since that amendment went into effect in 2013, the ASMFC’s Menhaden Technical Committee reported that, based on the inconclusive 2012 update stock assessment, it was impossible to determine whether or not the stock was “overfished” (i.e., stock size below its threshold size) due to uncertainties regarding the assessment model.[24] The issue was clarified when the ASMFC’s 2014 peer-reviewed, full benchmark menhaden assessment was published in early 2015. The 2014 assessment indicates that the stock is not subject to overfishing and is not overfished,[25] and that it has not been since the 1990s.[26]

Environmental concerns in the Chesapeake Bay

Dead zone

While popularly cited as filter feeders that remove excess algae and nutrients from the water, evidence suggests that menhaden do not significantly impact water quality. Adult menhaden largely do not eat phytoplankton, whose excessive growth leads to dead zones, instead feeding mainly on zooplankton.[27] There is evidence that, because menhaden secrete nitrogen, that they may actually be a net contributor to phytoplankton growth.[28]

Separate, but related, to the issue of dead zones are fish kills, where large numbers of menhaden or other fish will turn up dead in a single area. According to the Virginia Institute of Marine Sciences, which investigates fish kills in the Chesapeake Bay, the causes of fish kills are varied, but often are related to environmental factors such as low amounts of oxygen in the water, algal blooms, and water temperatures that are either too hot or too cold. Other factors, such as the dumping hazardous materials or excess bycatch, can also contribute.[29]

Striped bass

Due to the change in striped bass population many have begun to cite the commercial harvesting of menhaden as the reasoning behind the shift. Several claims state that menhaden are a key staple in the striped bass diet. However, other studies see the striped bass as an opportunistic feeder with a variety of aquatic creatures that it consumes and therefore does not completely rely on the menhaden. In fact, menhaden has been represented as low as 8% of the striped bass diet.[30][31]

History of the names

Wikimedia Commons has media related to Brevoortia_tyrannus.

References

  1. ↑ Froese, Rainer and Pauly, Daniel, eds. (2005). "Brevoortia tyrannus" in FishBase. 10 2005 version.
  2. 1 2 3 NOAA Fish Facts: Atlantic Menhaden
  3. ↑ "Menhaden appear to have little net impact on Bay water quality." Virginia Institute of Marine Science.
  4. ↑ "Atlantic Menhaden." South Atlantic Fishery Management Council.
  5. ↑ "Menhaden". National Oceanic and Atmospheric Administration. Retrieved 2015-09-08.
  6. ↑ Zimmer, R. (July 13, 2015). "Majestic humpback whale feeding in New Jersey". USA Today. Retrieved 2015-09-08.
  7. ↑ Radel, D. (June 22, 2014). "Whale tales: Humpbacks, more off Jersey Shore". Courier-Post. Retrieved 2015-09-08.
  8. ↑ Kaplan-Levensen, L. "Managing Menhaden: A New Plan for "The Most Important Fish in the Sea"". NolaVie. Retrieved 2015-09-08.
  9. ↑ McMurray, J. "Of Menhaden, Stripers Threshers and Whales". reel-time.com. Retrieved 2015-09-08.
  10. ↑ Joyce, C. (February 11, 1989). "Poisonous Algae Killed the Atlantic Dolphins". New Scientist. p. 31. Retrieved 2015-09-08.
  11. ↑ Blaylock, R.A. "The Marine Mammals Of Virginia" (PDF). Retrieved 2015-09-08.
  12. ↑ Reeves, R.R.; et al. "Humpback and Fin Whaling in the Gulf of Maine from 1800 to 1918" (PDF). p. 2. Retrieved 2015-09-08.
  13. ↑ Wheeler, D. & O'Gorman, M. (2011). Wild New Jersey: Nature Adventures in the Garden State. Rutgers University Press. p. 122. ISBN 9780813549217.
  14. ↑ ASMFC 2005
  15. ↑ Friend of the Sea, "Omega Protein’s Purse Seine Menhaden fleet"
  16. ↑ UN Food and Agriculture Organization, "A global assessment of fisheries bycatch and discards," 1996.
  17. ↑ NOAA, Chesapeake Bay Office, "Fish Facts: Menhaden"
  18. ↑ Friend of the Sea, "Fisheries USA – Purse seine – Gulf menhaden, Atlantic menhaden – FAO Western Atlantic Ocean"
  19. ↑ Friend of the Sea, "Omega Protein’s Purse Seine Menhaden Fleet."
  20. ↑ Atlantic States Marine Fisheries Commission, “2010 Atlantic Menhaden Stock Assessment,” 2010.
  21. ↑ Atlantic States Marine Fisheries Commission, “Amendment 2 to the Interstate Fishery Management Plan for Atlantic Menhaden,” December 2012
  22. ↑ VIMS. Menhaden, “Frequently Asked Questions.”
  23. ↑ Politifact Rhode Island, “Pew Environment Group says the Atlantic menhaden population declined by 90 percent in recent years,” The Providence Journal, December 14, 2012
  24. ↑ Atlantic States Marine Fisheries Commission, “2012 Atlantic Menhaden Stock Assessment Update,” July 2012
  25. ↑ SEDAR. 2015. SEDAR 40–Atlantic MenhadenStock Assessment Report
  26. ↑ See Figures 8.3.2.4 & 8.3.2.5, pages 192-193, SEDAR 40-1.3 Assessment Report Figures
  27. ↑ Friedland, Kevin; Lynch, Patrick; Gobler, Christopher, “Time Series Mesoscale Response of Atlantic Menhaden Brevoortia tyrannus to Variation in Plankton Abundances,” Journal of Coastal Research, February 11, 2011
  28. ↑ Ann and Edward Durbin, “Effects of Menhaden Predation on Plankton Populations in Narragansett Bay, Rhode Island,” Estuaries, September 1998
  29. ↑ Virginia Institute of Marine Science, “Fish Kill Events”
  30. ↑ http://www.vims.edu/research/departments/fisheries/programs/multispecies_fisheries_research/data_products/chesmmap_reports/2009.pdf
  31. ↑ http://www.fisheriessociety.org/mid-atlantic/Presentations_2010/08_Clark_Striped_bass_feeding_habits.pdf
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