LIFE HISTORY CONSEQUENCES OF OCEAN WARMING AND EXPLOITATION IN NORTHWEST ATLANTIC HERRING (CLUPEA HARENGUS)
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Explaining the mechanisms that generate and maintain intraspecific variation in life histories – the manners in which organisms acquire and allocate resources to growth, reproduction, and survival – is a fundamental goal of evolutionary biology, with applied relevance to resource conservation and management. The primary objective of this thesis was to evaluate the combined influences of temperature and exploitation strategy on metrics of life history in Atlantic herring (Clupea harengus), a widely distributed marine fish of key ecological and socio-economic importance in the northwest Atlantic. Chapter 2 demonstrates that a relatively simple thermal optimum model coupled with a common trend in the model residuals can account for most of the variability in mean length-at-age 4 within and among populations since the early 1960s. Building upon this evidence, Chapter 3 illustrates that the distinction between fisheries that do and do not target spawners, albeit clearly relevant for age at maturity, may be of secondary importance to reproductive success compared with effects of time-varying growth and total mortality. By developing a series of comparative analyses within and among populations of the same species, the present work illustrates how both the context and spatio-temporal scale of inference can affect perceptions concerning the relative importance of fishing and the environment for stock productivity and yield. From a management perspective, these findings call for increased collaboration among regional monitoring agencies and a more integrated view of the role of trait-based management strategies in sustainability.