Variation in Age Structure of the Incidental Kill of Spotted Dolphins, Stenella attenuata, in the U.S. Tropical Purse-Seine Fishery

During the 1979 SOPS Workshop, an analysis by D. Goodman of the age structure of the dolphin populations indicated that the stocks were likely to be in serious condition due to a shortage of younger age classes in the samples (Smith (ed) 1979). At the time of the analysis, W. Perrin warned that there were serious problems with the tooth readings and the samples upon which the analysis was based, and that the data could be seriously biased to the point where no useful conclusions could be drawn from the data as far as age structure is concerned. Shortly after the workshop, NMFS personnel developed a plan for a multi-phase analysis of all available data to determine what the age structure of the populations were. This report is an attempt to deduce from the observer data how representative the life history samples collected from spotted dolphins, Stenella attenuata, killed in the purse seine fishery may be. To date, I have analyzed only the observer data and have not yet done crosscorrelations between the life history and observer data. The analyses reported here were also designed to investigate variations in the age structure of the spotted dolphin kill by purse seiners so as to allow selection of life history specimens from situations where there is the greatest likelihood that the samples will be unbiased and thus reflect the true age structure of the population. 1980 United States. Marine Mammal Protection Act of 1972 NMFS (National Marine Fisheries Service) SWFSC (Southwest Fisheries Science Center) Library Public Domain 1930