Predicting where certain species of fish congregate and move is important for sport and commercial anglers and is the focus of a new study by Christopher G. Lowe, a CSULB marine biology professor, and Professor Jennifer Caselle of UC Santa Barbara.
"By tagging and tracking fish, we evaluated the site fidelities and home ranges of four of the most heavily fished, reef-associated sport fish in Southern California — California sheephead, kelp bass, barred sand bass and ocean whitefish," Lowe said.
Lowe, Caselle and CSULB graduate students Tom Mason and Lyall Bellquist undertook the study, funded by the California Sea Grant Program of the National Oceanic and Atmospheric Administration.
The team studied fish in the Catalina Island Marine Science Center Marine Life Refuge near Two Harbors to help understand what size marine reserves need to be to protect reproducing adult fish. They also examined whether reserve boundaries are 'leaky' or 'tight,' for certain species, meaning that the fish tend to stay within the boundaries or leave at certain times, making them susceptible to fishing.
Researchers implanted acoustic tracking devices into caught fish, then followed the fishes' movements over time and distance. These results were overlaid onto maps of habitats depicting such parameters as depth, rock formations and sand.
Altogether, 19 kelp bass, 19 ocean whitefish, 18 sheephead and eight barred sand bass were monitored for a year to evaluate their fidelity to the Catalina refuge." We found that whitefish were active during the day but stationary at night, which was a new discovery," Lowe said. "Overall, whitefish and kelp bass stayed in the area the longest."
Researchers also moved 15 fish away to understand how breaks in habitat such as going from sand-mud to rock affect fish movement. Five of the nine fish that were moved to discontinuous reef returned to the refuge, while all six of the fish moved to continuous rock reef quickly returned home. A barred sand bass took only nine hours to find its way home from discontinuous reef while the sheephead took 11 days. When moved to continuous reef, whitefish took nine hours and sheephead took up to 32 hours.
Lowe said kelp bass and sheephead seem less uncomfortable traversing large expanses of sand to neighboring reefs than the other two species, and that all the species they studied preferred continuous rock reef nearby for protection and for food sources.
Even small marine reserves could benefit kelp bass and barred sand bass, while "placing reserve boundaries at least 100 meters away from rocky habitat edges will reduce capture rates of all four species," he added.