title: The potential for spatial distribution indices to signal thresholds in marine fish biomass.
abstract: The frequently observed positive relationship between fish population abundance and spatial distribution suggests that changes in distribution can be indicative of trends in abundance. If contractions in spatial distribution precede declines in spawning stock biomass (SSB), spatial distribution reference points could complement the SSB reference points that are commonly used in marine conservation biology and fisheries management. When relevant spatial distribution information is integrated into fisheries management and recovery plans, risks and uncertainties associated with a plan based solely on the SSB criterion would be reduced. To assess the added value of spatial distribution data, we examine the relationship between SSB and four metrics of spatial distribution intended to reflect changes in population range, concentration, and density for 10 demersal populations (9 species) inhabiting the Scotian Shelf, Northwest Atlantic. Our primary purpose is to assess their potential to serve as indices of SSB, using fisheries independent survey data. We find that metrics of density offer the best correlate of spawner biomass. A decline in the frequency of encountering high density areas is associated with, and in a few cases preceded by, rapid declines in SSB in 6 of 10 populations. Density-based indices have considerable potential to serve both as an indicator of SSB and as spatially based reference points in fisheries management.
authors: Department of Biology, Dalhousie University, P.O. Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada.
authors: Emilie
authors: E
authors: Reuchlin-Hugenholtz
authors: Oceans Science Division, Department of Fisheries and Oceans, Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia, B2Y 4A2, Canada.
authors: Nancy L
authors: NL
authors: Shackell
authors: Department of Biology, Dalhousie University, P.O. Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada; Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, P.O. Box 1066, Blindern, NO-0316, Oslo, Norway.
authors: Jeffrey A
authors: JA
authors: Hutchings
mesh_terms: D000818:Animals; D018533:Biomass; D003247:Conservation of Natural Resources; D005399:Fishes; D008962:Models, Theoretical; D009792:Oceans and Seas