Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8802
Title: Species-specific responses of demersal fishes to near-bottom oxygen levels within the California Current large marine ecosystem
Author: A. A. Keller, L. Ciannelli, W. Waldo Wakefield, V. H. Simon, John A. Barth, S. D. Pierce
Publication Year: 2017
Journal: Marine Ecology Progress Series
Issue: 568
Pages: 151-173
Keywords: hypoxia, demersal fish, GAM,

Long-term environmental sampling provided information on catch and near-bottom oxygen levels across a range of depths and conditions from the upper to the lower limit of the oxygen minimum zone and shoreward across the continental shelf of the U.S. west coast (U.S. – Canada to U.S. – Mexico).  During 2008 – 2014, near-bottom dissolved oxygen concentrations (DO) ranged from 0.02 to 5.5 mL L-1 with 63.2% of sites experiencing hypoxia (DO<1.43 mL L-1). The relationship between catch per unit effort (CPUE) and DO was estimated for 34 demersal fish species in five subgroups by life history category (roundfishes, flatfishes, shelf rockfishes, slope rockfishes and thornyheads) using Generalized Additive Models.  Models included terms for position, time, near-bottom environmental measurements (salinity, temperature, oxygen) and bottom depth. Significant positive relationships between CPUE and DO occurred for 19 of 34 groundfish species within hypoxic bottom waters. Community effects (total CPUE and species richness for demersal fishes) also exhibited significant and positive relationships with low near-bottom oxygen levels. GAM analysis revealed an apparent threshold effect at lower oxygen levels, where small changes in oxygen produced large changes in catch for several species, as well as total catch and species richness. An additional seven species displayed negative trends. Based on AIC-values, near-bottom oxygen played a major role in the distribution of flatfishes, roundfishes and thornyheads.  By examining similarities and differences in the response of various subgroups of commercially important groundfish species to low DO levels, we uncovered ecological inferences of potential value to future ecosystem-based management.


Species response to hypoxia along the US West Coast


Theme: Recovery and rebuilding of marine and coastal species
Foci: Characterize the population biology of species, and develop and improve methods for predicting the status of populations.