Browsing by Subject "Northwest Atlantic"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Feeding habits of the tiger shark, Galeocerdo cuvier, in the northwest Atlantic Ocean and Gulf of Mexico
    (2017-04-14) Aines, Alexandra
    Sharks are apex predators that structure marine communities through predation. Despite a large number of studies in other areas, especially the Pacific, there are no quantitative data on the diet of tiger sharks, Galeocerdo cuvier, in the northwest Atlantic Ocean and Gulf of Mexico. Diet was assessed from 169 tiger sharks by life stage, area, and environmental factors. Fifteen prey groups were identified, with teleosts, molluscs, birds, cephalopods, and reptiles being the predominant prey categories. There was an ontogenetic shift in diet, prey size and diversity with an increase in shark size. Molluscs were most common in smaller sharks, while teleosts and reptiles became more important in the diet of larger sharks. Dietary overlap was significant by area (Gulf of Mexico vs Atlantic Ocean) and among all life stages except for young-of-the-year and adult tiger sharks. Overall, tiger sharks in the northwest Atlantic and Gulf of Mexico had diverse diets and exhibited ontogenetic shifts, similar to Pacific tiger sharks. Juvenile tiger sharks also demonstrated selective feeding by targeting gastropod foot over ingesting the entire animal. The results of this study can contribute to developing ecosystem models for tiger sharks in an area where their diet has been studied very little.
  • Thumbnail Image
    ItemOpen Access
    IMPLICATIONS OF HISTORICAL CHANGES IN FIXED FISHING GEAR FOR LARGE WHALE ENTANGLEMENTS IN THE NORTHWEST ATLANTIC
    (2003) Kozuck, Amanda
    North Atlantic right whales (Eubalaena glacialis) are one of the most critically endangered large whales in the world, with an estimate of 300 animals remaining. Despite international protection from whaling since 1935 and an endangered status listing under the United States Endangered Species Act, this population has been in decline since the 1990s. Factors hindering recovery include entanglements in fishing gear and ship collisions. Today, lobster pots and gillnets are most commonly implicated in large whale entanglements, especially those of right and humpback (Megaptera novaeangliae) whales. However, other fixed fishing gear presents entanglement risk to large whales, such as crab pots and slime eel gear. Entanglements typically occur when whales come into contact with lines attached to the gear; any body part can be involved. I present historical data tracking changes in fishing line and fixed fishing gear, as well as changes in fishing practices, from the mid-1940s to the present in the Northwest Atlantic. The introduction of synthetic materials to the fishing industry in the 1950s, coupled with government subsidies and legislation for domestic fishery expansion, led to dramatic increases in fishing effort and efficiency. These attempts to promote the development of the U.S. fishing industry have created entanglement risk for large whales. In 2002, eight right and eleven humpback whale entanglements were documented; two deaths resulted, one of each species. This suggests that existing protective measures are inadequate. I briefly examine current regulations and provide suggestions for further measures to reduce the conflict between large whales and fixed gear fisheries.