success of both Brown Pelicans and Double-crested 

 Cormorants has improved dramatically and the 

 population of Brown Pelicans may be on its way 

 to recovery (Anderson et al. 1975). 



Chlorinated hydrocarbons and poly- 

 chlorinated biphenyls have also been linked with 

 shell thinning of Ashy Storm-Petrel and Common 

 Murre eggs on the Farallon Islands (Coulter and 

 Riseborough 1973, Cress et al. 1973). Many 

 other populations of seabirds in North America 

 have been similarly affected by these contaminants. 



This Brown Pelican egg was broken under the 

 weight of incubating adults as a result of thin 

 eggshells from pesticide contamination. Photo by 

 Frank Gress. 



Plastic particles are commonly found in the 

 stomachs and gizzards of seabirds collected for 

 scientific study (Baltz and Morejohn 1976, 

 Rothstein 1973). It is likely that seabirds mistake 

 these for larval fish, eggs, or other foods floating 

 on the ocean surface. These particles enter the 

 environment by physical breakdown of the huge 

 quantities of plastics which are dumped into the 

 world's oceans each year. 



The physical presence of plastic particles 

 may affect the health of birds. Particles which 

 accumulate in the gi/zard probably are not as 

 effective as the pebbles normally used to grind up 

 food. Fortunately, plastics are nearly chemically 

 inert and are unlikely to affect birds the way toxic 

 chemicals do. More research on this topic and 

 concern about the "garbage can" attitude we have 

 toward our oceans are needed. 



FISHERIES 



Commerical fisheries can affect seabirds in 

 three primary ways: 1) birds drown in gillnets, 

 2) offal from fishing boats provides an additional 



food supply for certain seabird species, and 

 3) extensive fisheries deplete some seabird prey 

 species. Depletion of prey fishes presently seems 

 to be the major fisheries-related threat to seabirds 

 in California. Gillnet drowning and offal discharge 

 have dramatically affected seabirds in other 

 parts of the world. 



Seabirds drown in gillnets when they are 

 caught while diving or plunging into the water for 

 food. The alcids, which dive to feed, and shear- 

 waters (Pufftnus spp.), which plunge into the 

 ocean to feed, are among the most vulnerable of 

 seabirds. The salmon driftnet fisheries of the 

 North Atlantic and North Pacific Oceans have 

 caused high mortality of seabirds. The Danish 

 salmon fishery off West Greenland killed an 

 estimated 500,000 to 750,000 Thick-billed 

 Murres (Uria lomvia) annually between 1968 and 

 1975 (Tull et al. 1972). In the North Pacific, the 

 Japanese salmon mothership fishery kills over 

 200,000 seabirds in gillnets each summer (Ainley 

 et al. in prep.), and large numbers of seabirds die 

 in the Japanese land-based fishery as well (Sano 

 1978). Restriction of gillnet fishing near colonies 

 and in regions of known high seabird concentra- 

 tions at sea could reduce this kill. The large 

 incidental kill of Thick-billed Murres in the 

 Danish fishery was curtailed after an international 

 agreement took effect in 1976, restricting the 

 Danish fishery to only coastal waters (Salomonsen 

 1979). The Japanese fishery, although reduced in 

 size in recent years, is still very active in the 

 North Pacific. 



The only salmon gillnet fishery In California 

 is located in the Klamath River of northern 

 California. Some birds drown in the nets of this 

 fishery each summer (Chatto pers. comm.) 

 but the total number of birds killed is small. 



An unknown number of seabirds are killed 

 annually in a small coastal gillnet fishery for 

 bottomfish that operates from Tomales Bay south 

 to Santa Barbara (Miller pers. comm.). Common 

 Murres, cormorants, and Sooty Shearwaters 

 (Puffinus griseus) are apparently the species most 

 frequently caught. Although this fishery has 

 existed for at least 50 years, it has only recently 

 become large enough to cause concern. The 

 California Department of Fish and Game and 

 the U.S. Fish and Wildlife Service are currently 

 investigating the mortality of marine birds and 

 mammals in this fishery. 



Offal from boats, particularly processing 

 ships associated with large whaling and fishing 

 fleets, provides large amounts of food for some 

 seabird species, especially Northern Fulmars 



