A genetic tagging approach to assessment of abundance and movement rates for copper and quillback rockfish in a small marine protected area in the Strait of Georgia, B.C.

Sean P. Cox, Simon Fraser University
$48,886

Marine protected areas are the main conservation tool used to manage British Columbia’s inshore rockfish populations. Over 30 Rockfish Conservation Areas (RCAs) currently exist to protect inshore rockfish from directed harvesting and bycatch in Pacific salmon and groundfish fisheries. In addition to covering only a small fraction of the total coastline, relatively small individual RCAs have been implemented under the assumption that rockfish have particularly small home range sizes. However, there has been little scientific investigation of actual rockfish home range sizes in B.C. because rockfish are difficult to observe using traditional sampling methods. If home range sizes are large relative to overall RCA size, then existing spatial refuges will be inadequate to protect inshore rockfish from exploitation by recreational and commercial fishing fleets. Therefore, research that evaluates RCAs as a management tool for conserving inshore rockfish is urgently needed. The objectives of this project are to: (1) demonstrate that the non-destructive, genetic tagging approach can be used to estimate absolute population sizes of inshore rockfish and (2) determine possible movement patterns of copper and quillback rockfish within a small (2km2) RCA located in the Strait of Georgia, B.C. We will employ a novel genetic tagging approach to determine rockfish abundance and movement rates within the Trincomali Channel RCA located off Galiano Island. This is an ideal location in which to test the method because the RCA is bounded east and west by landforms. Genetic tagging of inshore rockfish involves obtaining small tissue samples by means of specially designed remote biopsy hooks. Accurate spatial position information for each tissue sample is recorded using a handheld WAAS Global Positioning System that is accurate to approximately +/- 3m. Highly variable DNA microsatellite markers obtained from each tissue sample are then analyzed to identify individual fish. In contrast to existing tagging methods, which have proven impractical for rockfish, our genetic tagging method greatly reduces handling mortality and eliminates tag loss (i.e., DNA fingerprints are permanent). Such improvements increase our ability to estimate abundance, long-term survival, and movement rates, because tagged fish remain in the population for long periods of time. Tag recapture information will be analysed using a stratified-Petersen mark-recapture estimator in which tagging site and sampling events represent the strata.

Research on abundance monitoring approaches and movement rates are needed to determine if current RCA designs and locations are adequate to promote recovery of diverse inshore rockfish populations in British Columbia, as well as those within other jurisdictions across the Pacific Northwest. Historically, mark-recapture methods have been extremely valuable for determining movement patterns of animals in both terrestrial and aquatic environments. Our research will apply a ground-breaking new approach to providing basic abundance and movement rate estimates for inshore rockfish, which will in turn improve our ability to design marine protected area management strategies.