Recent quantitative values of Macrohectopus branickii (Dyb.) (amphipoda) from Lake Baikal

摘要

Macrohectopus branickii is the only amphipod with an exclusively pelagic lifestyle. Although this species plays an important role in the diet of pelagic fish of Lake Baikal, there is no regular monitoring of its abundance. We present data on the status of the population from a lake-wide 2015 survey and compare these data with available historical information. The survey was conducted with a modified Juday net and simultaneous hydroacoustics profiling from up to 700 m depth to the surface. The abundance of M. branickii in the pelagic zone over depths >300 m in 2015 averaged 1700 ind/m(2) (range 320-4090 ind/m(2)) and the biomass averaged 3.7 g/m(2) (range 1.1-14.4 g/m(2)). Sites with the greatest abundance of M. branickii were located in the South and Middle Basins off the eastern shore. These values are comparable to the published data from 1950s to 1980s. The characteristics of nearshore aggregations of larger mature females were more variable and need further study. (C) 2019 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.