The role of life history parameters as indicators of stock structure

Vital population parameters, such as growth, survival, recruitment, reprodu ction, distribution, and abundance, are the consequences of life history mo des to which fish stocks have evolved. Differences in these parameters have long been used to identify separate management stocks assuming that phenot ypic variation is due to genotypic and environmental controls. However, few studies have examined the temporal stability of life history parameters, n or the mechanisms by which differences in these parameters between stocks a re maintained. We examine the temporal and spatial stability of several lif e history parameters of Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and yellowtail flounder (Limanda ferruginea) in the northwest Atlantic Ocean to assess their utility for stock identification. Although significant temporal differences in vital rates were found within stocks, d ifferences were generally maintained between stocks. Both genetic (biologic al) and oceanographic (physical) conditions play an integral role in mainta ining stock structure. Although, the utility of vital life history paramete rs for stock identification may decrease with stock complexity and exploita tion history, their applicability increases with the number of parameters e xamined. (C) 1999 Elsevier Science B.V. All rights reserved.