Spatial distribution, spawning stock biomass and the development of spatial reference points
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The relationship between spawning stock biomass (SSB) and 3 spatial distribution metrics (SDMs), measuring range, concentration, and density, using fisheries independent survey data for 10 demersal Northwest Atlantic fish populations (9 species), show metrics of density offer the best correlate of SSB. The concave, positive relationship between high density area (HDA) and SSB indicates that a decline in HDAs beyond a spatial threshold is associated with disproportionately large SSB declines in 6 populations. HDAs might indicate highly productive areas and/or positive fitness consequences, enhancing the ability of individuals to successfully spawn, locate prey, and evade predators. HDAs can help to assess the status of a population’s spatial structure and serve as a spatial reference point. By comparing spatial reference point locations relative to existing biomass reference points (based on MSY), scenarios are described wherein spatial reference points contribute to biomass reference points and to a precautionary approach to fisheries management.