Mesopelagic fishes of the Arabian Sea: distribution, abundance and diet ofChauliodus pammelas, Chauliodus sloani, Stomias affinis, and Stomias nebulosus

Four species of predatory fishes - Chauliodus pammelas, Chauliodus sloani, Stomias affinis and Stomias nebulosus - were collected on two cruises to th e Arabian Sea during 1995. We present data on the abundances, horizontal an d vertical distributions, and diet of these fishes. We also discuss briefly the importance of the oxygen minimum zone and predation on myctophid fishe s to the ecology of these mesopelagic predators. Chauliodus pammelas and C. sloani appear to have only partially overlapping horizontal distributions in the Arabian Sea, with C. pammelas more common to the north and C. sloani more common to the south. Our data support previous results suggesting tha t diel vertical migration is the norm for these species, with smaller indiv iduals usually nearer to the surface and larger individuals tending to stay deeper. In contrast to Chauliodus, Stomias affinis and S. nebulosus appear to have largely overlapping horizontal distributions in the Arabian Sea. H owever, they may have slightly different vertical distributions, with S. af finis living slightly shallower (especially at night) than S. nebulosus. Al l four species spend most of their time in the oxygen minimum zone, enterin g the surface oxygenated waters (100-150 m) only at night (if at all). The diets of C. pammelas, C. sloani, and S. affinis consisted mainly of lantern fishes, Myctophidae, and other fishes. In contrast, S, nebulosus, the small er of the two Stomias species, ate mostly copepods and other crustaceans. T his differential feeding may allow the two Stomias species to co-occur. Thr ee of these four stomiids appear to play an important role in predation on myctophid fish populations in the Arabian Sea. (C) 2001 Elsevier Science Lt d. All rights reserved.