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I. RESKABCH 



The Immediate focus of research efforts relating to the incidental taking of 

 marine mammals in the course of commercial fishing operations should be the 

 development <>f gear and techniques which will result in the reduction of 

 Incidental mortality and serious injury rate to an insignificant level approach- 

 ing zcn>. Additional efforts should be devoted to gaining an understanding of 

 such aspects <>f the subject as the bond between \ellowfin tuna and porpoise 

 to facilitate the development of effective gear and techniques. Estimate of 

 mortality and serious injury and the population levels of marine mammals 

 subject to incidental taking are also needed to permit an assessment of the 

 significance of the impact of such taking on those populations. 



Although progress has been made toward reducing porpoise mortality and 

 serious injury incidental to commercial tuna lishing, the total kill and serious 

 injury levels remain unaceptably hi^h. Gear and techniques such as the 

 Medina panel, the current indicator, the antitorque cable, the backdown pro- 

 cedures, and the training of skippers appear to contribute to some reduction 

 in the rate of incidental mortality and serious injury. However, indications 

 are that no matter how widely these new devices and techniques are utilized 

 by the industry in the course of commercial tuna fishing operations, they will 

 probably not, in themselves, produce _an acceptably low rate of incidental kill 

 and injury. The Commission is convinced by a review of current research 

 efforts that more and substantially different research is urgently needed and 

 should be instituted as soon as possible. 



Mortality and serious injury statistics seem to be increasingly available, at 

 least with respect to commercial yellowfin tuna fishing operations within the 

 IATTC permit zone (CYRA), and some data are becoming available with 

 respect to operations conducted outside the permit zone. Extrapolations from 

 these data are being reduced to provide a limited idea of the impact of inci- 

 dental taking upon the porpoise populations as a whole. The Committee of 

 Scientific Advisors is proceeding with its efforts to provide you with estimates 

 of the incidental taking in response to your request but progress has been 

 delayed by the unavailability of some data. The Southwest Fisheries Center 

 has recently made the necessary data available to permit the Committee to 

 estimate incidental take figures for the 1971-73 seasons which should be 

 transmitted in the near future. Data relating to the 1974 season have not yet 

 been received from the Center. An estimate by the Committee of the incidental 

 take resulting from regulations which apply to commercial fishing operations 

 after October 1974 will, of course, not be available until those regulations are 

 finally prescribed and data derived from fishing under those regulations are 

 available. 



A NMFS aerial reconnaissance program to determine porpoise population 

 levels has been reviewed by the Commission and Committee. This program is 

 limited in scope, by aircraft range, to approximately 500 miles offshore and 

 the results of the program are very difficult to interpret because of w r eather, 

 sea state problems, inadequate ground truth data, observer variations and 

 fatigue, and other factors which were discussed at a meeting in La Jolla. 

 Neither the kill statistics program nor the aerial reconnaissance program pro- 

 vides reliable direct data on the frequency of capture of individual animals, 

 population sizes, population movements, or age related mortality. It is our 

 opinion that at the conclusion of the present work on this subject, the very 

 important datum of total population size for the porpoise popidations im- 

 pacted by commercial tuna fishing operations will be, at best, crudely and 

 inadequately known. 



Although NMFS work on the life histories of the affected porpoise species 

 seems to be proceeding well, data on the nature of the tuna-porpoise bond, 

 the behavior of porpoises inside and outside the net with relation to each 

 other, differential behavior that might allow separation of fish and porpoise, 

 and the exact nature and timing of mortality in the net, are essentially non- 

 existent and we are aware of no program, presently contemplated by NMFS, 

 to gather such data. 



Research on gear modification and development has thus far resulted in 

 some reduction in kill and serious injury but future research and development 

 plans seem, in our opinion, to be far too restricted to substantially contribute 

 to a solution to this problem. Further testing of new gear and techniques as 

 well as modifications of those presently utilized should be undertaken. Much 



