Seasonal cycles in weight and condition in Atlantic cod (Gadus morhua L.) in relation to fisheries

Abstract

Abstract Seasonal cycle in weight and physiological condition of Atlantic cod (Gadus morhua) influenced productivity and economic impacts of the cod fishery in Placentia Bay, Newfoundland. Condition indices (Fulton's K condition factor and hepatosomatic index – HSI) were lowest during the spawning season (spring) and increased rapidly during the postspawning period, reaching maximum values by fall (K and HSI increased on average 24% and 82% between spring and fall, respectively). Somatic weight and condition indices varied seasonally. Condition indices were correlated with an industry index of product yield. Historically, cod fisheries have been prosecuted during all seasons, but simulations of 1997–1999 fisheries indicate that a fall fishery (period of peak physiological condition) resulted in a 8–17% decrease in the number of cod removed from the stock while maintaining the same weight-based quotas, and profiting from maximum yield and better product quality. Spring and summer fisheries resulted in lower yield (6%) and quality (5–26%) of fish products by weight. Seasonal biological cycles could be used as templates for management strategies that promote fisheries conservation and economic benefits by harvesting fish during periods when biological impacts are minimal and economic returns maximal.