An evaluation of recruitment indices for Northeast Arctic cod (Gadus morhua L.)

Abstract

Indices of the abundance of Northeast Arctic cod (Gadus morhua L.) for various life stages were compared in order to determine the earliest stage at .which year-class strength is established. The indices considered are: VPA estimates of spawning stock biomass; an egg abundance index; an early juvenile (approximately three-months old) abundance index; 0-group (age four to five months) abundance indices; bottom trawl and acoustic survey abundance indices for one, two and three- year-old cod and VPA estimates of the abundance of three-year-old cod. Based on a regression analysis, the relative abundance of early juvenile cod was the first life stage that was correlated with their relative'abundance as three year olds. Since the cokelation between the estimates of spawning stock biomass or total egg production and the relative abundance of three-year-old cod was weak, it is concluded that considerable yearly variation in mortality occurs before cod reach the early juvenile stage