Copyright (c) 2013 University of Massachusetts - Amherst All rights reserved. http://scholarworks.umass.edu/marine_theses Recent documents in Marine Sciences and Technology Masters Theses Collection en-us Fri, 25 Jan 2013 21:57:50 PST 3600 http://scholarworks.umass.edu/theses/956 http://scholarworks.umass.edu/theses/956 Fri, 23 Nov 2012 07:53:21 PST Mercury accumulation of upper trophic level marine fishes is a growing concern for human consumers. Diet is the primary source of mercury bioaccumulation in both fish and humans and yet remains unexamined in many intensely fished regions such as southern New England (SNE). The feeding ecology and mercury concentrations of recreationally caught albacore (Thunnus alalunga) and yellowfin (T. albacares) tunas, shortfin mako (Isurus oxyrinchus) and common thresher (Alopias vulpinus) sharks and dolphinfish (Coryphaena hippurus) were evaluated. Important prey were identified and also measured for total mercury content. Seventy percent of the predator fishes sampled in this study had mercury concentrations greater than the EPA recommended 0.3ppm, and included shortfin makos (2.65 ± 1.16ppm), threshers (0.87 ± 0.71ppm) and albacore (0.45 ± 0.14ppm). Mercury concentrations were lowest in dolphinfish (0.20 ± 0.17ppm) and yellowfin (0.32 ± 0.09ppm). Length was positively correlated with mercury content and bioaccumulation rates were linear for tunas and dolphinfish, while exponential for both shark species. Small schooling fishes (Pomatomus saltatrix, 0.110 ± 0.102ppm) were the primary prey of shortfin makos. Shortfin squid (Illex illecebrosus, 0.028 ± 0.005ppm) was a principal and consistent dietary component of both tunas and dolphinfish diets. The diets of SNE dolphinfish and yellowfin tuna were more invertebrate dominated than other regions previously examined. Though the method of sample collection for this study biases toward larger individuals, these are the sizes of fish targeted by anglers, generally for human consumption.

]]> Teffer, Amy K. http://scholarworks.umass.edu/theses/209 http://scholarworks.umass.edu/theses/209 Wed, 21 Jan 2009 12:07:21 PST This is the first study to assess how the coastal migratory stock of striped bass (Morone saxatilis) uses non-natal New England estuaries during their foraging migration. Using hydroacoustic telemetry from June through October in Plum Island Estuary, Massachusetts, I examined how long coastal migratory striped bass stayed throughout the seasons, if they were equally distributed, if individual striped bass were distributed differently, and if distribution changed with season, tide, or light. Striped bass, ages 2-5 (300-480 mm), were tagged with VEMCO transmitters in the spring and summer of 2005 (N=14) and 2006 (N=46). They stayed for an average of 66 days in 2005 (SE=7.6) and 72 days in 2006 (SE=6.2). Of the fish tagged in 2005 and 2006, 60% remained for longer than 30 days. This might reflect two striped bass migration strategies: 1) transient migration, in which striped bass visit many estuaries, and 2) estuary-specific, in which they reside in a single location for the summer. The amount of time the striped bass spent in six reaches delineated within the estuary was quantified. Striped bass were not evenly distributed across these reaches. Instead, they spent the most time in the mid Plum Island Sound and lower Rowley River reaches in both years. Three different uses of PIE were observed. Some striped bass stayed briefly (5-20 d; N=24), some stayed primarily in the Rowley River (N=14), and others stayed primarily in Plum Island Sound (N=22). Striped bass use of the mid Plum Island Sound and lower Rowley River reaches remained consistently high in spring and summer, but decreased in fall, while use of the lower Plum Island Sound did not vary much. Use of other reaches varied seasonally. Tide and light were less associated with distribution, but in the summer the Rowley River use-group increased utilization of tidal creeks during the day, though not at high tide. These three use-groups identified in Plum Island Estuary may be foraging contingents that may learn how to forage in specific parts of the estuary demonstrated by over half the striped bass remaining for much of the summer and congregating in distinct areas.

]]> Pautzke, Sarah M.