Journal of Northwest Atlantic Fishery Science 

About: Journal of Northwest Atlantic Fishery Science is an academic journal published by Northwest Atlantic Fisheries Organization. The journal publishes majorly in the area(s): Population & Gadus. It has an ISSN identifier of 0250-6408. It is also open access. Over the lifetime, 512 publications have been published receiving 16529 citations.

A Review of Size Dependant Survival During Pre-recruit Stages of Fishes in Relation to Recruitment

Abstract: The theory of recruitment in fishes and hypotheses pertaining to causes of recruitment fluctuation are summarized. In spite of considerable research effort over several decades there has been no significant improvement in identifying clear causal mechanisms of recruitment in marine fish stocks. Starvation has not been demonstrated to be a primary mechanism controlling survival of fish larvae. Studies matching food levels and year-class strength continue to provide indirect evidence that growth during the first year of life is dependent on food supply and may be important in determining survival. The hypothesis that survival is a direct function of growth provides a rational theoretical framework for recruitment research and is suggested as a basis for future work. Growth rate must be studied as a function of both ration and temperature. Studies examining the relationship of growth rate to survival should be specific to each life history stage and ideally integrated throughout the pre-recruit period. It remains to be demonstrated that survival is a direct function of growth, mediated through size-dependent predation.

Emerging from Hjort's Shadow

Abstract: Early in the 20 th century, Johan Hjort developed compelling arguments and hypotheses to explain recruitment variability that became dominant for more than 75 years. A cautious emergence from Hjort’s shadow began late in the 20 th century. Hjort’s “Critical Period” hypothesis, i.e., failure of first-feeding larvae to find food, and a second hypothesis, “Aberrant Drift” of eggs and larvae, were proposed to explain causes of recruitment variability. Tests of the Critical Period hypothesis became an obsession, although support for it was inconsistent and equivocal. Single-minded research on the Critical Period hypothesis gave way to realization that recruitment variability was the outcome of complex trophodynamic and physical processes acting over many temporal and spatial scales and throughout pre-recruit life. A complex mix of main effects and interacting factors can easily generate order-ofmagnitude variability in recruitment via small effects on mortality and growth rates during the abundant egg and larval stages, or via cumulative effects during the pre-recruit juvenile stage. New considerations of compensatory mechanisms that can dampen variability and stabilize recruitment emerged. A little density dependence, especially in the relatively long juvenile stage, can regulate recruitment. Multidisciplinary programs instituted in the 1990s and successful development of statistical models and coupled bio-physical models, offered new insights into mechanisms generating recruitment variability. Despite progress, forecasting recruitment remains a formidable challenge. “Solving the recruitment problem” is no longer the Holy Grail of fishery science. Appreciating recruitment variability, explain ing its probable causes, considering implications for management, and understanding it in the context of broader variability in marine ecosystems, are all worthy goals.