responses to different types of net structure and lines may 

 suggest ways for reducing incidental mortality of the species 

 in set net fisheries. Therefore, in 1987, the Commission 

 provided additional funds to the University of California to 

 support experiments using net structures of different types 

 to better determine possible variables affecting the ability 

 of harbor porpoise to detect and avoid fishing nets. Field 

 work is scheduled to be conducted during summer and fall of 

 1988. 



It may also be possible to detect discrete populations 

 by identifying differences in patterns of contaminant loads 

 in animals from different regions. As discussed in previous 

 Annual Reports, the National Marine Fisheries Service's South- 

 west Fisheries Center contracted in 1985 for an investigation 

 to test for regional patterns in the concentration of contami- 

 nants and their ratios in harbor porpoise and to evaluate the 

 feasibility of using contaminants to obtain information about 

 the degree of intermixing of harbor porpoise along the west 

 coast of North America. Results of that study were made avail- 

 able at the end of 1986. The study found strong regional 

 patterns in both the concentrations of DDE (dichlorodiphenyl- 

 dichloroethylene) and the ratios of various contaminants. 

 Thus, the use of contaminant ratios to gain information on 

 geographic interchange of harbor porpoise appears promising, 

 especially in areas like California where the presence of 

 pollutants in the marine environment varies widely from location 

 to location. 



As discussed elsewhere in this Chapter, the State of 

 California enacted legislation in 1986 to reduce the incidental 

 take of sea birds, marine mammals and non-target fish species 

 in gill and trammel set net fisheries by means of selected 

 fishing area closures. Also in 1986, in order to bring the 

 fisheries into compliance with the Migratory Bird Treaty Act, 

 the California Department of Fish and Game proposed to amend 

 the State regulations by banning use of set nets inside 20 

 fathoms between Franklin Point, San Mateo County, to the Men- 

 docino-Sonoma County line. On 3 December 1986, the National 

 Marine Fisheries Service wrote to the California Department 

 of Fish and Game, noting that the proposed modification, 

 designed primarily to protect sea birds, would relocate the 

 fishing effort into deeper waters and thus would likely increase 

 the incidental kill of harbor porpoise. The Service recom- 

 mended that the State amend its proposed prohibition on set 

 nets to include a prohibition on use of trammel nets north of 

 Point Reyes, where more than 60 percent of the harbor porpoise 

 mortality occurred in 1984 and 1985. 



Subsequently, representatives of the Service, the Cali- 

 fornia Department of Fish and Game, the Marine Mammal Commis- 

 sion, environmental groups, and affected fisheries met and 



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