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Black rockfish tagging off Oregon coast

Oregon Department of Fish and Wildlife leads the way in applying PIT tag technology to marine fish in the wild. Working in cooperation with area charter fishermen, the agency’s Marine Program is using the tiny electronic tags in whole new way to obtain information on Oregon’s black rockfish population.

The lack of solid data has made it tough for managers responsible for black rockfish to generate population estimates. With the West Coast groundfish crises looming, ODFW scientists anticipated the need to acquire accurate data for this important recreational and commercial fishery. With the support of Newport’s charter vessel operators, they designed a project to provide an independent estimate of population abundance and exploitation rate for black rockfish near Newport.

The rice-grain sized PIT (Passive Integrated Transponder) tags have been used in several applications since the mid 80’s. They are used extensively in salmon research in the Columbia River Basin to track the movements of individual fish and to monitor the downstream migration of smolts through dams. Pet owners and ranchers may recognize the technology as the injected PIT tags now being used as animal ID cards. But this is the first time the have been used in a wild marine fish and the first time they have been used to determine the actual abundance and exploitation rate of a stock.

Another first for the project is the use of dockside staff to scan fish carcasses for the tags. In the past, tagging programs have relied on the public to voluntarily turn in tags. According to Steve Parker, “Having staff dedicated to counting carcasses and scanning for tags completely eliminates the problem of estimating tag non-reporting and greatly increases the accuracy of the study. The beauty of the study is that fishermen bring all their fish to you”, states Parker. “The downside is that it takes a lot of staff time to pull it off.”

The tagging project began in Spring 2002. With the help of Newport’s charter operators, and using past sport fishing data, the ODFW research team designed the tagging strategy. Captain Terry Burbee and crewman Jake Burbee provided the F/V Umatilla II and expert fishing. In 20 days of fishing, staff caught, PIT tagged and released 2500 black rockfish. ODFW biologist Polly Rankin noted “The on-deck handling of the fish was critical. In order to minimize the traumatic effects of gas expansion in the rockfish, we worked to get them tagged and back down to depth in under 60 seconds.” On deck, the crew recorded data on the fish’s length and all symptoms of barotrauma, caused by the ascent to the surface. The fish was then injected with the PIT tag and scanned with a reader to “energize” the tag and acquire the individual ID number. The crew ran a logging GPS unit and recorded the time of each fish scanned, tying it to an exact location. The fishing crew sent all fish back over the side in a PVC fish cage, which was quickly dropped to 40 feet to re-compress the fish’s swim bladder at the time of release.

In late May 2002, ODFW port samplers began the daily counting and scanning of black rockfish carcasses coming into Newport and Depoe Bay. Because PIT tags are an injected tag, they are invisible, so each carcass must be scanned to find the tagged fish. By August 1, the dockside samplers had scanned 34,000 fish carcasses for tags and found 36 tagged fish.

What happens now? If the pilot study works out, expansion of the project to other vessels and areas of the coast would mean that the group could get annual information on multiple populations representing Oregon’s key marine sport fishery. The ODFW team plans to use the PIT tag technology to alleviate the uncertainty about the black rockfish population and to promote sustainable fishing.