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.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 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 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 . Biologist are unsure as to how Butis koilomatodon will affect native fishes found along the Brazilian coast but are monitoring thier impact.
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