Bangladesh Gets New Marine Fish (Actinopterygii: Teleostei): First Observation of Seven Species from Rocky Tidal Habitats of the St. Martin’s Island, Bay of Bengal

On the northeastern flank of the Bay of Bengal, the St. Martin’s Island, a sedimentary continental formation, is the only maritime island and an Ecologically Critical Area of Bangladesh. Rock beds fringing the island from supratidal to subtidal zone with a subtidal depth around 10 m and presence of non-reef forming scleractinian corals from lower rocky intertidal to about 200–600 m offshore comprise a rich but least-explored rocky tidal habitat. Addressing the knowledge gap, during December 2017, an expedition was conducted to observe fish diversity caught in beach seines, gillnets and drifting handlines. Studying morphological and meristic characters of the collected specimens revealed 7 bony fish species for the first time in Bangladesh and northern seaboard of the Bay of Bengal. These are Ablennes hians, Callionymus erythraeus, Ellochelon vaigiensis, Grammatobothus polyophthalmus, Istiblennius dussumieri, Omobranchus punctatus, and Trichonotus setiger. The family Trichonotidae and the genera Ablennes, Callionymus, Grammatobothus, and Istiblennius, too, represent the first record for Bangladesh. Omobranchus punctatus, I. dussumieri, C. erythraeus and T. setiger were strongly associated with the tidal boulder beds. Grammatobothus polyophthalmus, a flounder threatened by shrimp harvesting, was caught in trawling gillnet operated in the surrounding subtidal waters. Ellochelon vaigiensis, a catadromous mullet known to spend natal stages near shoreline, was collected from a rock-pool. Fish diversity of the St. Martin’s Island is not well understood; the last comprehensive checklist dated back to 1997. Thus, these results remarkably obtained from a cursory expedition entail a thorough diversity assessment of the island.