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Research Technical Report

The Use of Seal Bombs in California Fisheries: Unknown Impacts Point to an Urgent Need for More Research

Kerr, A., and J. Scorse (2018)

Unpublished Report, Center for the Blue Economy, Middlebury Institute of International Studies, Monterey, California. 14 pp.


Commercial fishing in California is a significant source of jobs and incomes. The industry can also produce detrimental environmental impacts, including injuries to threatened and endangered marine mammals and damage to marine ecosystems. There are a host of state and federal legal and regulatory mechanisms in place to protect marine mammals and their habitat. Some of these are more effective than others, and all exist within a continually evolving political and economic landscape. Seal bombs are incendiary devices used by some fishers to deter sea lions, seals, and other mammals from fish nets and fishing grounds. Measures to allow the use of seal bombs were adopted in part to protect fishermen from mammal depredation, but there is increasing evidence that the devices are being used off the coast of California at higher levels than previously realized. The available evidence indicates that seal bombs may pose a significant risk to marine life, both due to risk of direct injury from the blasts and the large number of intense noise impulses being introduced into marine ecosystems filled with animals that depend on the natural soundscape to live and thrive. The current regulation of these devices is weak, informed by outdated and incomplete research. Further, the monitoring and enforcement of their use is minimal, and their direct consideration by seafood certification organizations is practically nonexistent. Therefore, the authors recommend that the state and federal agencies tasked with monitoring and enforcing the use of seal bombs in California immediately review their policies, and consider significant investments in seal bomb research and monitoring to ensure that they are being used according to the law and not producing significant harm to marine mammals.