Ed Trippel, Research Scientist Fisheries and Oceans Canada, from the St. Andrews Biological Station

Title: Demography, degrees and development of scientific advice for fisheries management 


Advancements in our understanding of reproductive and early life processes of marine fishes have been slow to become integrated into stock assessment advice.  Factors such as age-based spawning periodicity, nutritional-based indices of gamete quality, and viability of eggs and larvae as a function of spawner experience have been experimentally demonstrated for a number of fish species with medium to extended longevity.  A number of experimental and modelling approaches will be summarized that highlight the discrepancies that arise when not accounting for these recent scientific advancements.  The significance of building up and maintaining a balanced age structure over decades is critical to sustaining long-term recruitment during periods of environmental uncertainty.  Common harvest practices of setting total annual allowable catches often fail to recognize the underlying damage done by size-selective cropping of long-lived species.  A greater appreciation for the full suite of biological traits of individuals is required for the conservation and sustainability of fishery resources.  Oceanographic changes including temperature variation are also of obvious importance to reproduction.  Examples of significant temperature effects and their relative magnitude to age-based effects on timing of spawning, egg size and match-mismatch of larval-prey resources will be given.

Fishery managers are in a position to influence stock biomass and age structure but have no influence over ocean environmental conditions.  The inter-play of these factors and capacity for science to assist in resource management will be discussed.