Selective predation by the zoarcid fish Thermarces cerberus at hydrothermal vents

This study investigates predation by the vent zoarcid fish Thermarces cerberus through gastrointestinal analyses of 27 specimens collected with the submersible ALVIN at vents at 9°50′N on the East Pacific Rise. T. cerberus fed most frequently on gastropod mollusks (mainly Lepetodrilus elevatus) and amphipod crustaceans (mainly Ventiella sulfuris). Species found occasionally in high abundance included the swarming amphipod Halice hesmonectes and the snail Cyathermia naticoides. Other items also found in gastrointestinal tracts, but in very low numbers, included polychaete worms, crustaceans and unidentified tissue clumps. The comparison between the size distribution of L. elevatus limpets ingested by T. cerberus and those found attached to vestimentiferan tubes suggest that the fish may selectively prey on large limpets. If the selective removal of large Lepetodrilus spp. limpets by T. cerberus does occur, then it would have potential community-level consequences at hydrothermal vents, since these mobile gastropods appear to inhibit the settlement of sessile vent species, including tube-building worms. Our results suggest possible direct and indirect effects of T. cerberus on benthic community structure at hydrothermal vents on the East Pacific Rise.