Brown pelicans as anchovy stock indicators and their relationships to commercial fishing
Anderson, D.W.; Gress, F.; Mais, K.F.; Kelly, P.R. (1980). Brown pelicans as anchovy stock indicators and their relationships to commercial fishing. Rep. - Calif. Coop. Ocean. Fish. Invest. XXI: 54-61
In: Reports. California Cooperative Oceanic Fisheries Investigations. Scripps Institution of Oceanography: La Jolla, Calif.. ISSN 0575-3317, more
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| Authors | | Top |
- Anderson, D.W.
- Gress, F.
- Mais, K.F.
- Kelly, P.R.
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| Abstract |
Seabirds as offshore wildlife resources have largely been unstudied by wildlife managers until recently. Brown pelicans (Pelecanus occidentalis californicus) in Southern California Bight (SCB) have received special attention in the past under the Endangered Species Act of 1973 (ESA), Special consideration is given to species with endangered status in commercial fishery management plans mandated by the Fisheries Conservation and Management Act of 1976, but such plans also attempt to deal positively with all species of seabirds and marine wildlife as society's values change more positively toward such offshore wildlife resources. Brown pelican breeding status is heavily dependent on abundance and/or availability of anchovies during the prebreeding and breeding periods. This is likely due to the dominance of northern anchovy (Engraulis mordax) biomass in surface schooling fishery stocks in the SCB. The predator-prey relationship that involves brown pelicans and anchovies in the SCB is a tenuous one due to 1) the strong dependence almost solely on anchovies evidenced over the last nine years of study and 2) potential increases of commercial harvest of anchovies since 1979 under some options of the Anchovy Management Plan provided by the Pacific Fishery Management Council. There are also two elements of this interaction that complicate straightforward management of pelicans: a) implementation of a liberal harvest option under the Anchovy Management Plan rather than a more conservative one and b) increasing anchovy harvests in Mexico. Unless anchovies are replaced by another prey, breeding pelicans may ultimately require a larger forage reserve of anchovies, offshore refuges (critical habitat under the ESA), and possibly more conservative quotas in the anchovy reduction fishery. A management plan for brown pelicans and other seabirds in the SCB has not yet been developed by the appropriate agencies. Past anchovy harvests (pre-1979) probably did not detectably disrupt the pelican/anchovy relationship, although at the higher observed levels of pelican reproduction (coincident with higher levels of anchovy biomass and catch), pelican reproductive rate was not maximal. This is more likely because pollution may still be chronically affecting pelican reproduction. Anchovy harvests under an optimum yield scheme will be monitored closely for possible effects on pelican reproduction. Although more detailed studies are needed, we provide some initial suggestions based on brown pelican requirements. |
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