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AFSC Seminar Series No. 17

Scheduled Seminars

"Has The Steller Sea Lion ‘Experience’ Taught Us Something About Ecosystem Approaches to Management?"

Presenter: Lowell Fritz, AFSC
When: Thursday, March 1, 2007, 11:00am
Where: Traynor Seminar Rm (2076), Bldg. 4,  AFSC, Sand Point Campus, Seattle, Washington

  • This seminar will be transmitted live to the Auke Bay Laboratory (main conference room), and to the Newport Laboratory (BFB - Room 201).
  • When arriving from off the WRC campus, leave extra time to check in with security at the gate and at the entrance to building 4.


The decline of the western Steller sea lion population and listing under the Endangered Species Act (ESA) has challenged scientists and fishery managers to determine causes for the decline and promote recovery, while simultaneously allowing opportunities for some of the largest commercial fisheries in the country. Fisheries under the Sustainable Fisheries Act (SFA), marine mammals under the Marine Mammal Protection Act (MMPA), and endangered species under ESA, are all managed using largely single-species approaches. However, all Acts point to healthy ecosystems as a primary objective for management: to support the sustainable use of fished species, to insure that marine mammals continue to be functional ecosystem components, and to preserve habitat and ecosystem structure for the recovery of ESA-listed species.

Since 2001, over $140 million has been spent on hundreds of research and management projects investigating 6 primary factors hypothesized to have caused, either singularly or in combination, the decline of western Steller sea lions: predation by killer whales, disease, contaminants, direct killing by humans (including legal and illegal shooting, and incidental take in fisheries), and nutritional stress caused by environmental change or competition with fisheries. Population dynamics (viability) models indicate that if the steep decline observed in the late-1980s has no chance of occurring in the future (i.e., we controlled the responsible factor), then the current population has a low chance of extinction within 100 years. However, if natural (i.e., largely uncontrollable) forces were primarily responsible for the decline and have even a small chance of reoccurring, then the western Steller sea lion population has a high probability of extinction.

Reconstruction of the timing of changes in sea lion survivorship and natality suggest that a combination of top-down and bottom-up forces contributed to the decline. These data indicate a shift in the vulnerable age/sex class from juveniles (and their survival) to adult females (and their reproductive rates). Although direct killing by humans has been reduced, the potential effects of fishery competition could affect sea lion recovery, as well as populations of other upper trophic level piscivores (e.g., northern fur seals). Based on our experience with Steller sea lions, an ecosystem approach to fisheries and marine mammal management (1) must involve recognition that fishing is likely to have ecosystem impacts beyond those predicted by single-species models, (2) should manage fishery impacts on spatial and temporal scales applicable to competitors, not just on scales convenient for humans, (3) is likely more than the sum of conservatively set single-species fishery catch quotas and should incorporate food web dynamics, and (4) should involve implementation of the ecosystem-protection provisions of the SFA and MMPA prior to the use of the ‘critical care’ regulatory authority available under the ESA.

Presenter's Bio:

Lowell Fritz received a BA in Biology from Bucknell University in 1976, and a MS in Marine Science from the Virginia Institute of Marine Science, College of William and Mary in 1982, where he studied (that’s right) the shell microstructure of the commercial hard clam. Following a brief stint with NMFS (and marriage to Alyce) in 1982, he went to work as a Research Associate with Rutgers University at the Shellfish Research Lab in (that’s right) Bivalve, NJ, where his studies ranged from freshwater to deep-sea hydrothermal vent mollusks. The west beckoned in 1990 with opportunities for both Alyce (with NOS) and Lowell (with NMFS-AFSC) in Seattle. Lowell began working with REFM on Steller sea lion-fishery interactions and fishery stock assessments, moved to the Center Directorate office in 2001 to help with Steller sea lion research coordination, and is currently with NMML, Alaska Ecosystem Program.


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