Reproductive Biology and Population Models in Fisheries: Are We Assuming Too Much?

Biologists have long known that fish exhibit a wide range of reproductive strategies, many of which can influence population dynamics. Yet, the complex reproductive life history strategies of hermaphroditism, batch and skip spawning, and variable age at maturity are rarely or only partially incorporated into stock assessments for management. Basic biological data are rarely collected on an annual basis, despite strong evidence of fishing- and climate-induced shifts in maturation, spawning frequency, and natural mortality in many valuable fish stocks. Importantly, we may not be adequately monitoring population productivity – rather, we often make assumptions about productivity based on theoretical models that assume stationarity in many vital rates and rely on age structure monitoring to derive recruitment variability. This may lead to over-estimates of steepness and other key demographic parameters that may be shifting over time. Furthermore, directional change in climate parameters may invalidate predictions based on historical data. However, the resources needed to collect data to generate time series of population productivity may be difficult to obtain in today’s fiscal climate. In this symposium we will offer perspectives from across North America on how much information is needed to appropriately incorporate this biological complexity into our population models and what are the potential consequences of failing to do so, as stocks respond to changing climates and management structures.
Scott A. Heppell
Scott A. Heppell, Gary R Fitzhugh and Selina Heppell
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