Mesopelagic nekton and associated physics of the southeastern Bering Sea

Abstract

Abstract The mesopelagic community of fishes and squids are fundamental in the diet of apex predators, but in most cases their life histories and habitat requirements are poorly understood. In May 1999, a pilot study was conducted to identify mesopelagic nekton, describe dominant physical characteristics of their habitat, and compare their relative abundances over several study sites in the southeastern Bering Sea. Biological samples were collected at 250, 500, and 1000 m depths with an open pelagic rope trawl lined with 1.2-cm mesh in the codend. Net type, mesh size, and trawling techniques were designed to parallel those of extensive Russian research surveys in the western Bering Sea, permitting direct comparisons between study results. Forty-three species of fish and 15 species of cephalopods were identified, including a new species of gonatid squid and a range extension for Paraliparis paucidens, a snailfish never before observed in Alaskan waters. Faunal biomass was high with over 25,000 (1400 kg) fish and squid collected in only 13 trawls. Concentrations of fish in this area surpass published records from the western Bering Sea and North Pacific Ocean by an order of magnitude, driven primarily by Leuroglossus schmidti, a deep-sea smelt. Generally, specimens were of high quality, and new size records were established for several species of fish and squid. The physical environment as determined from altimetry, satellite-tracked drifters, and water properties (temperature and salinity) was typical of the last decade for this area. Spatial patterns in species distribution were observed, but further research is needed to determine whether these are a factor of mesoscale variability or of habitat characteristics.