4 research outputs found
Differences in Dolphin Mortality Rates in Night and Day Sets for the U.S. Eastern Tropical Pacific Tuna Purse Seine Fishery
Because dolphins sometimes travel with yellowfin tuna, Thunnus albacares, in the eastern tropical Pacific (ETP), purse seiners use the dolphins to locate and capture tuna schools. During the process of setting the purse seine nets, dolphins often become entangled and drown before they can be released. Data for the U.S. purse seine fleet in the ETP during 1979-88 show that dolphin mortality rates in sets made during the night are higher than mortality rates in sets made during the day. Even with efforts to reduce nightset mortality rates through the use of high intensity floodlights, night set mortality rates remain higher. The data are also used to simulate a regulation on the fishery aimed at eliminating night sets and show that dolphin mortality rates would decrease
The 1996 U.S. Purse Seine Fishery for Tropical Tunas in the Central-Western Pacific Ocean
The U.S. tropical tuna purse seine fleet has fished the central-western Pacific Ocean under the South Pacific Tuna Treaty since 1988. The 1996 fishery was the poorest since the start ofthe Treaty. Fishing effort declined due to the financial collapse of a large fishing enterprise. Catches reached record lows for yellowfin tuna, Thunnus albacares, and skipjack tuna, Katsuwonus pelamis, and continued a declining trend that started in 1995. Catch rates also decreased to the lowest levels since 1991. Whether this declining trend in catch rates is due to reduced availability of fish caused by cyclic ocean environmental changes affecting vulnerability or to reduced abundance from excessive fishing pressure is not yet known and needs to be assessed
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Fish Bulletin 175. The California Drift Gill Net Fishery For Sharks and Swordfish, 1981β82 Through 1990β91
California's drift gill net fishery developed rapidly in the late 1970s off southern California. The fishery originally targeted the common thresher Alopias vulpinus. Almost immediately swordfish Xiphias gladius and shortfin mako Isurus oxyrinchus became important components of the catch. We examined and summarized data obtained from the California logbook system, landing receipts, and market samples taken from this fishery over the 10 fishing seasons from 1981β82 through 1990β91. During this period the fishery evolved from a small nearshore experiment to a major California fishery. Significant changes in nearly every aspect of the fishery occurred including boats and gear, techniques and regulations, fishing areas and seasons, and targeted species. These data form a base line from which changes in the fishery and harvested stocks can be compared in the future. The drift gill net fishery operates primarily in the area between San Diego and Cape Mendocino and concentrates much of its effort on swordfish in the Southern California Bight during the months of May to December. During the period studied, fishing effort decreased 50% to 60%, from highs of approximately 11,000 sets to a low of about 4000 sets in the 1990β91 season. This decrease in effort corresponds to a decrease in total landings of approximately the same proportions. Decreases in landings of common thresher were over 80%, while swordfish and shortfin mako landings decreased 60% and 40% respectively. Average sizes of swordfish showed no change during the 1981β82 to 1990β91 fishing seasons. Average sizes of shortfin makos showed a decrease of approximately 40% from the 1982β83 through the 1985β86 fishing season, but rebounded during the 1989β90 season to within 15% of the 1982β83 season. Average sizes of common thresher, however, decreased 30% from the 1982β83 season and remained low. This may indicate a decline in the common thresher stock or reflect changes in the season and area of fishing operations. A number of problems and conflicts occurred during the first 10 years of the fishery (e.g. bycatch of marine mammals and striped marlin Tetrapturus audax) which were resolved for the most part through the cooperative efforts of the commercial industry, the sport industry, environmental groups, and State and Federal governments. The incidental catch of marine mammals is apparently low and not compromising any stocks, although the potential for damage remains and therefore monitoring is prudent. Bycatch of other fishes does not appear to be a problem except for the catch of blue sharks Prionace glauca, which has an unknown affect on local stocks