Developing New Management Techniques for Sharks in the Drift Gillnet Fishery of the Southern California Bight

The Southern California Bight (SCB) is a contiguous geographical region that extends from Point Conception, California to northern Baja California and west into the California Current. This region’s productive ecosystem supports various recreational and commercial fisheries, some of which target pelagic sharks. For example, the common thresher shark (Alopias vulpinus) comprises the largest commercial shark fishery in California waters (the California drift gillnet fishery, or CA-DGF. Mako sharks (Isurus oxyrinchus) are also taken in large numbers.The biology and status of pelagic sharks within the SCB have implications for California’s marine resource sustainability. In addition, the SCB is known to be an important nursery area for these and other pelagic shark species. It is thus important to learn what defines mako and thresher shark essential habitat (i.e., the specific areas important for the growth and survival of these species). The objectives for this grant were to learn more about the fine-scale movement patterns and depth distributions of SCB mako and threshers in order to understand ways to reduce their potential vulnerability to the CA-DGF. We accomplished this goal using acoustic telemetry (juvenile makos and threshers) and archival tagging (threshers) technology. This work supported three Scripps Institution of Oceanography (SIO) graduate students as Sea Grant trainees (C. Sepulveda, N. Wegner, D. Cartamil), and provided material for three SIO doctoral thesis chapters (one for trainee Sepulveda, two for trainee Cartamil).For further information on this study, please contact Jeffrey B. Graham (jgraham@ucsd.edu) or Daniel P. Cartamil (dcartamil@ucsd.edu