27 



FISHERY SYSTEMS ANALYSIS 



The costs and earnings analysis of tlie fleet of tuna 

 boats based in California ports, wiiich was completed 

 some time ago. proved to be so valuable ;ti examining the 

 economic constraints on the prosperity of this fleet that 

 R.E. Green has started a second economic study to in- 

 vestigate the economic base of the California industrial 

 fishery -which, as has been noted earlier, is in a very 

 depressed situation. The planning of this study was per- 

 formed in collaboration with B.C. Noetzel of the BCF 

 Division of Hconomics, 



Among other matters of less immediate concern, 

 the study should prove valuable in assessing the earnings 

 lost to the fleet througli the assignment of zone limits in 

 the anchovy reduction fishery. 



R.E. Green's services were given in November- 

 December 1967 to the International Bank for Recon- 

 struction and Development. He went on a mission to 

 Ecuador to estimate the economic soundness of a request 

 put to the Bank by the Government of Ecuador for the 

 development of a small fleet of tuna purse seiners in the 

 eastern tropical Pacific Ocean. 



Technicians from this project have made a number 

 of trips on tuna purse seiners in the last year. They 

 have collected data on aspects of seining operations, 

 principally the rate of sinking of nets of varying sizes 

 and constructions-an important matter in view of 

 Green's recent demonstration of the relation between the 

 depth of the mixed layer and nature of the thermocline 

 and the percentage of successful sets in this fishery. Dur- 

 ing these studies, bathykymographs were mounted at sev- 

 eral points along the leadlines of purse seines and, from 

 their records. Green has prepared diagrams of the shape 

 of the net at critical stages during its setting. 



Fishing (>penirii>ns ivsainli cxpcrinu'iiful purse seine f<)r 

 (una is huill in a San Pedro nel-vard. j Qg^,^ 



|fe-n»— ' 



This modified design incorporates a 33 percent 

 hang-in of webbing at the corkline to allow rapid sinking 

 with a decreasing hang-in down to 1 5 percent on the 

 leadline to permit the net to stay at depth during pursing. 

 The net is also tapered at the ends to save webbing and 

 equipped with "gavels" which will decrease the open 

 area next to the seiner. 



The net will initially be placed aboard a chartered 

 vessel and, suitably instrumented with bathykymographs, 

 will be tested at sea in simulated setting operations. 

 When tests are successfully completed the net will be 

 loaned to a commercial vessel for the late summer blue- 

 fin and albacore tuna fisheries; the operation of this ves- 

 sel and of the net will be obsei-ved by technicians from 

 the project. 



EXPERIMENTAL PURSE SEINE 



In I96ti, R.E. Green studied the design and per- 

 formance of purse seines with M. Ben-^'anii, a fishing 

 gear technologist from the Department of Fisheries of 

 the State of Israel, who spent 3 months at the Fishery- 

 Oceanography Center during that year. Comparative 

 studies with model nets at La JoUa showed that an im- 

 proved net design might increase the sinking rate by as 

 much as twice and, moreover, fish more deeply at the 

 net ends. These tests were so encouraging that, in collab- 

 oration with BCF Exploratory Fishing and Gear Re- 

 search Base in Seattle, the construction of a full-scale 

 tuna purse seine based on Green and Ben-Yami's design 

 was undertaken. The net is now complete and ready for 

 trials. 



Fishing operations researeh resting mocki of experi- 

 mental tuna purse seine. ^ Q|.gg^ 



