Evidence of habitat associations and distribution patterns of rockfish in Puget Sound from archival data (1974-1977)

Abstract

Rockfish (<italic>Sebastes spp.</italic>) populations have declined dramatically and failed to recover in Puget Sound, WA following a period of heavy exploitation in the 1970s and 1980s. Despite these declines, there exist few historical data on which to base management and rebuilding plans. I explored whether archival data from an early recreational fishing survey could be used to 1) characterize the distribution of rockfish species in Puget Sound in the 1970s with respect to environmental variables and 2) detect changes in rockfish distribution and abundance over time. Results of multivariate analysis indicated that catch for black rockfish (<italic>S. melanops</italic>) and brown rockfish (<italic>S. auriculatus</italic>) in part could be explained by proximity to kelp and the average magnitude of bottom currents, while bathymetric characteristics were not effective for predicting catch for any species. Comparisons of catch across sites revealed that copper rockfish (<italic>S. caurinus</italic>) and brown rockfish were unlikely to be caught at the same sites, suggesting limited co-occurrence at locations within the study area. Black rockfish, yelloweye rockfish (<italic>S. ruberrimus</italic>), greenstriped rockfish (<italic>S. elongatus</italic>) and quillback rockfish (<italic>S. maliger</italic>) were caught along a range of sites, suggesting a weak gradient in their distribution across the study area. The data ultimately proved unsuitable for the purposes of detecting change over time, due to problems of data adequacy and mismatches between the scale of data collection and the scale of ecological processes. Despite this, multivariate statistical methods were able to detect distributional patterns that may prove useful for management with respect to assemblage approaches to rockfish management in Puget Sound, and designation of essential fish habitat or marine protected areas. This example illustrates that even seemingly challenging historical data sets may yield new insights that justify their retrospective analysis.