Gobioidei

Gobioidei is a suborder of the Perciformes, the largest order of fish. The suborder includes the gobies. The suborder Gobioidei is made up of 2,211 species which are divided into seven different families. Phylogenetic relationships of Gobioidei have been elucidated using molecular data.^[1][2] Gobioids are generally small fish and are mostly marine (saltwater) fishes but roughly 10% of the population inhabit fresh waters. This suborder is made up of mainly benthic or sand burrowing fish. Benthic fish are aquatic lifeforms which live on the bottom of a body of water. Like in most benthic organisms, Gobioids do not have a gas bladder/ swim bladder which keeps them from suspending in the water column; so they must stay on the bottom.^[3][4]

Families Within the Gobioidei Suborder

Gobiidae

The family of gobiidae which is made up of fish called gobies make up the largest marine family of fish in the world with around 1,950 different species. It is common for gobies to have their pelvic fins fused together. This allows them to use their pelvic fins as a suction device to keep them anchored on a hard surface such as a rock or piece of coral. Gobies often live in association with invertebrates such as sponges and sea urchins in or around corals both soft and hard; however some species live on bare mud and sand. Gobies are typically small fish many do not exceed a total length of 10 cm. Some of the smallest fish in the world belong to this suborder such as the Trimmatom nanus. This is a species found in the Indian Ocean which is only 8–10 mm as an adult. The largest of the Gobiid family is found in the South Atlantic and Caribbean region the Violet Goby or Gobioides broussenetti can grow to a length of 50 cm long, this goby which is purple in color resembles an eel with its elongated anal fin and dorasl fin. Some gobies under the genus of Periophthalmus and Boleophthalmus are practically amphibious, meaning they can breath in and out of water. Species like the Atlantic mudskipper (Periophthalmus barbarus) which can grow to a length of 25 cm can actually breath air. These gobies will skip across the mud of intertidal flats in mangrove swamps in search of food, adults feed mostly on crabs, insects and other arthropods.^[5]

While most of the species in this family are found in a marine setting there are some species that inhabit fresh water streams and lakes. Some of which are important to island stream assemblages. Species such as the Red-Tailed Stream Goby (Lentipes concolor) are able to use their fused pelvic fins as a suction device which enables them to ascend rock faces alongside waterfalls allowing them to inhabit waters far from the ocean.^[6]

Kraemeriid

The members of the family Kraemeriid are known as the sand gobies. This is because these particular gobies will regularly rest in the sand with just their head showing.^[7] The genus Knipowitschia is one of the five genus in the Kraemeriid family of sand gobies. There are fifteen different species found within the genus Knipowitschia. The Vrgorac goby (Knipowitschia croatica) is one of the fifteen found within the Knipowitschia genus. This species is found in the Black Sea and surrounding seas such as the Caspian and Adriatic seas. It can grow up 5 cm but reaches sexual maturity at an early age being able to reproduce at a length of 45 mm. Females lay a clutch of eggs which range from about 200 to 600 eggs. Spawning occurs from March to November but the majority of spawning activity occurs between April and September[6].^[8]

Rhyacichthyid

The specimens within the family Rhyacichthyidae are known as the loach gobies these fish are found in and around the countries of Indonesia and Australia. The third of their body towards their tail is fairly flat this adaptation along with their pelvic fins serving as a suction cup allows them to withstand very strong current.^[9]

Eleotridae

The family of Eleotridae are often referred to as sleepers; this is because these fish usually lie still on the bottom as if they were asleep. These have a wide range and are distributed in tropical and subtropical regions in estuaries and streams. Fish in the Eleotridae family are often primary predators in streams and ocean islands in and around areas such as Hawaii and New Zealand where larger predators are absent.^[10] Although these species are native to the Indonesia area of the Pacific they are expanding there range to the southwestern Atlantic along the coast of Brazil. The species Butis koilomatodon has been found on the eastern coast of Brazil. It was first found in the year 1989 but was never identified until the year 2000. As of the summer of 2012 twenty three specimens of Butis koilomatodon have been collected along the coast of Brazil, all specimens were collected at 6 different locations along the coast. Biologist have been able to identify seventeen of the specimens as males, four as females and two more were unable to be sexed. And many of the specimens were in different stages of maturity meaning there is likely a breeding population established but there is not enough data to conclude that there is. How this species got to the other side of the continent of South America is unclear. Many believe that they were brought over in the [ballast tanks] of ships. The small size (10 cm max) of the species Butis koilomatodonmakes it very easy for them to enter the intake holes on a ships ballast tank. Also their able to tolerate a wide range of salinity levels as well as temperature fluctuations makes it likely for them to inhibit a ballast tank on journeys across the ocean.^[11] Biologist are unsure as to how Butis koilomatodon will affect native fishes found along the Brazilian coast but are monitoring their impact.

Microdesmidae

This family is often referred to as the wormfish family. These are similar to the fish from the family of Kraemeriidae in the fact that they too will submerge themselves in the sand and mud. The only difference is the anatomical appearance of the Microdesmidae family. Fishes in the Microdesmidae family are small fish which often resemble an eel.^[12]

Ptereleotrids

The fish within the family of Ptereleotrids have several names associated with them which are; dart fishes, fire fishes, and hover gobies. They have been given these nicknames because of their bright coloration as well as their ability to hover just above the bottom of the reef whereas most gobys are actually lying on the bottom most of the time and are called dart fish because when threatened or frightened they will quickly dart to a burrow beneath a rock or other structure.^[13] The Chinese Zebra Goby (Ptereleotris zebra) is an example of a fish from this family. The Ptereleotris zebra can reach a maximum length of 12 cm and is usually found in and around reefs in depths from 2 – 31 meters be are predominantly found in reefs with a depth of 2 – 4 m . The native range of the Chinese Zebra Goby is in the Indonesia Pacific area occupying the Great Barrier Reef as well as the Red Sea and the Marshall Islands of Micronesia.^[14] This is a schooling species which means that will stay in groups and that many of these fish can be found in the same refuge at once.

Schindleriidae

This family has only three species within it, the fewest number of species of all the other families. These fish are called the infant fishes this is due to their size.These fish reach maturity and are able to reproduce once they reach a length of 2 cm. Another reason for the name of infant fishes is because these fish are neotenic. Neoteny is when adults retain traits or their juvenile form. This is true for these species because they spend their entire life in a larval state. Some characteristics which they retain are the lack of pigmentation or color, a larval kidney, and also they have an unossified skeleton. Ossification is the process in which new bone material is made to make bones bigger and stronger ^[15]

Species of Endangerment

The Tidewater Goby ( Eucyclogobius newberryi) was listed as an endangered species on February 4, 1994, it is the only species of goby with the genus Eucyclogobius. E. newberryi is native to the coastal region of California, USA found in marshes and lagoons with brackish water. Predominately found in waters where the salinity is less than 12 parts per thousand but has been documented in waters with a salinity of 42 parts per thousand. E. newberryi prefer water with mild temperatures (8 to 25 degrees Celsius) and waters with a depth from 25 to 200 cm. There is little vegetation within the habitat of E. newberryi, there are species of submerged and emergent plants. The gobies often use thick patches of these aquatic vegetation to hide in if threatened or disturbed. The average life span of the E. newberryi is only one year. These species occur in groups ranging from just a few individuals to thousands in a group. Spawning and reproduction is at its peak during spring and on into late summer. However in the southern region of its range where waters remain at a warmer temperature E. newberryi will reproduce year round. The females will lay between 300 and 500 eggs into a burrow dug out vertically by the male which is 10 to 20 cm deep. Spawning locations are usually located out in the open away from any vegetation. The male will then guard the eggs until they hatch which is 9 to 11 days. Habitat loss and modification are the main threats to the E. newberryi.The brackish areas where saltwater and freshwater meet are where E. newberryis prefer to live, these areas along the coast of California has been altered due to development. Barriers such as dikes and levees have been implemented to protect residents from potential flooding however, the creation of these barriers has reduced habitat for the E. newberryi. Other reasons for population declines are attributed to exotic fish and amphibians which have been introduced to the region. Many of these fish prey on the E. newberryiand other out compete them for food and habitat. The altering of streams flow with diversions have affected the salinity of the water and have also changed the habitat at creek mouths where E. newberryi have historically lived. Restoration projects have been started to bring populations back to a more stable number by making more habitat available as well as providing protective areas. Some levees have been removed and exotic species reduction programs are in the midst of being initiated.^[16]

References