Events & Media

The Bren School of Environmental Science & Management
at the University of California, Santa Barbara



"Withering syndrome and the management of southern California abalone fisheries"

Tal Ben-Horin
Bren School of Environmental Science & Management

Thursday, Sept. 27, 2012
3:00 p.m.
Bren Hall 3526

Hunter Lenihan, faculty advisor
Frank Davis, Bruce Kendall, and Kevin Lafferty (Marine Science Institute), committee members

Despite the importance of pathogens in natural populations, little attention has been given to host-pathogen dynamics in fisheries management. Population thresholds for the invasion or persistence of infectious diseases are central to the theory and practice of disease ecology and epidemiology, and are naturally extended to fisheries. By driving host populations below thresholds for transmission, fishing supports a number of desirable outcomes, including the extirpation, or fishing out, of pathogens. Southern California abalone fisheries closed in 1997 due to a combination of overexploitation and a fatal infectious disease caused by a Rickettsiales-like pathogen (WS-RLO). The susceptibility of abalone populations to WS-RLO varies considerably by species, and for a number of apparently tolerant species, promising signs of recovery have been observed throughout the Southern California Bight since the fishery closure. These observations have motivated a proposal to re-open a limited-access abalone fishery at San Miguel Island. I will present results from laboratory experiments and field observations evaluating the susceptibility of abalone populations to WS-RLO, and from having combined fisheries and disease models to apply the concept of fishing out disease to the proposed abalone fishery. Although fishing out WS-RLO is unlikely, fishing with the pathogen can provide modest sustainable yields while reducing the rate of WS-RLO transmission. Infectious diseases inherently increase the risk of overexploitation, and I found that fishing effort should be lower than predicted in the absence of infection. However, contrary to principles of precautionary fisheries management, I found fishery yield to be sustainable at a lower minimum size limit than predicted in the absence of infection. This work complements assessments of the San Miguel Island abalone stock and highlights the importance of explicitly considering the role of pathogens when managing fisheries impacted by disease.