ROCKFISH MOVEMENT STUDIES
AT BIG CREEK RESEARCH RESERVE
In response to the collapse of fisheries worldwide, fishery managers are looking at ways to monitor and enhance fish populations. One method being studied is the use of fishery reserves, designated areas in which taking of fish is prohibited. Reserves have several potential benefits, including preservation of genetic and biological diversity, preservation of fish habitats and the development of underwater parks.
"There are a number of questions relating to reserves and their value from a fishery standpoint," explains Starr.
rock fish in a kelp forest
Research into fishery reserves is taking place locally, at the Big Creek Research Reserve, a California Department of Fish & Game (DFG) reserve on the Big Sur coast. Rick Starr of the UC Sea Grant Extension Program, in cooperation with Moss Landing Marine Labs, the National Marine Fisheries Service and DFG, is studying the role of fishery reserves in enhancing fish populations. His study involves tagging rockfish in the reserve and mapping their movements, to learn how big and what shape the ideal reserve for rockfish should be.
The idea behind fish reserves is that the number of fish will increase, as will their average size, within the protected area. Because of the increase in fish density it is thought that there will be a spill-over effect, increasing the population density outside the reserve's borders also, with the protected area acting as a source for export of juveniles and larvae out into the surrounding waters.
The spill-over and value of a reserve relevant to a particular species depends on the size, shape and location of a reserve. The shape is important because of migration patterns of target fish. For example, some fish make a vertical migration (offshore - onshore), while some run along the shore, and the reserve that doesn't take into account their movements will be ineffective. But to date, most of these concepts for fishery reserves have not been well studied.
"One of these questions is, How big should the reserve be? It needs to be big enough to encompass the home range [typical movement] of target fish, because if the fish moves in and out of the reserve on a daily basis, it is not protected." This is one of the key goals of Starr's research: to learn the home range of rockfish and to use that data to help define what size and shape reserves for that species should be.
To do this Starr and his researchers insert acoustic transmitters into the fish and then monitor their movements. He spent last summer at the Monterey Bay Aquarium testing the best way to attach transmitters; results showed that surgical implantation was better for the fish than fastening transmitters to their dorsal fins.
The actual research began this summer, and Starr anticipates that it will continue for several years. The team took advantage of the McArthur cruise this spring to use side scan sonar to help map the rockfishes' habitats within the reserve. They also hope to use submersibles to study the number of species in the study area.
Starr's research fits well into the Monterey Bay National Marine Sanctuary's overall research plan, which includes working to describe and delineate habitats, to understand the relationship between fisheries and ecosystem processes and to understand the effect of fishing on structure of fish assemblages. Starr expects the benefits from these rockfish movement studies to be far-reaching: "We anticipate that we will get a better understanding of fish movements in and around the reserve area, and an understanding of the home ranges of fish off the Big Sur coastline. The results should help sanctuary and reserve managers here and internationally to do a better job designing the size, shape and location of ecological reserves."