The dynamics of prespawning capelin (Mallotus villosus socialis) off the West Kamchatka coast

Abstract

Pacific capelin catches for the period 1961-2000 are analysed. Biological data are used to show that spawning-stock biomass, spawning time, and size of the spawning areas were not stable. Estimates of stock biomass were made from a helicopter. Stock size, in terms of catch and estimated spawning-stock biomass, fluctuated in a two-year cycle, and differed by a factor of 10 or more from year to year. Every 20-22 years, the cycle shifted from even- to odd-numbered years. Capelin have also seemingly started to spawn earlier, coincident with a decrease in sunspot activity. The highest occupancy of spawning grounds was in 1990, when 90% of the possible habitat was used. Minimum occupation of spawning grounds was about 3%, in 1984. © 2002 Published by Elsevier Science Ltd on behalf of International Council for the Exploration of the Sea.