Stomach content analysis of the Atlantic Sharpnose Shark from the Northeast Gulf of Mexico from 2000 to 2003 (NCEI Accession 0164788)
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Atlantic sharpnose shark Rhizoprionodon terraenovae diet is described from Crooked Island Sound, an embayment of the northeast Gulf of Mexico. Diet was assessed by life-stage and quantified using six indices: percent by number, percent by weight, frequency of occurrence, the index of relative importance (IRI), IRI expressed on a percent basis (IRI), and IRI based on prey category (IRIPC). Young-of-the-year sharks (n56) fed on a mix of teleosts (mostly clupeids, 44.6 IRIPC) and invertebrates (combined, 25.1 IRIPC), juveniles (n185) on sciaenids (40.7 IRIPC) and clupeids (37.8 IRIPC), and adults (n105) on sciaenids (71.4 IRIPC). Differences in diet by site and ontogeny were tested by comparing diet from Crooked Island Sound with published information from St. Vincent Island in Apalachicola Bay, an adjacent estuary. Stomach contents were also used to expand on published prey size-predator size information.
Diet of scalloped hammerhead shark in eastern Gulf of Mexico
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Juvenile scalloped hammerhead sharks, Sphyrna lewini, were collected in northwest Florida to examine foraging ecology, bioenergetics, and trophic level (30-60 cm FL mean FL 41.5 cm n 196). Diet analysis was performed using single and compound measures of prey quantity. Diet was also analyzed using seven broad diet categories (DC). Diet composition and estimated daily ration were compared to previously published information on bonnethead sharks, S. tiburo. Diet overlap was low between species. Juvenile S. lewini feed on relatively small (85 of prey items 5 shark length) teleosts (mostly bothids and sciaenids) and shrimps, whereas S. tiburo have been documented to feed mostly on crustaceans and plant material in northwest Florida. Plant material contributed little to the diet of S. lewini. Estimated daily ration was significantly lower for S. lewini (4.6 BW d-1) than for S. tiburo in northwest Florida, regardless if plant material was included in the model (p0.02 including and p0.00001 excluding plant material). Trophic level was calculated at 4.0 for S. lewini and 2.6 for S. tiburo. Stable isotope analysis showed S. lewini had significantly higher 15N values and significantly lower 13C values than S. tiburo, supporting the difference observed in calculated trophic level. These results provide evidence that small juvenile hammerhead species co-exist in coastal northwest Florida by feeding at separate trophic levels.
Swordfish Stomach Content Data, 1989-2000
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Stomach contents were tabulated for 734 swordfish (Xiphias gladius) from the central North Pacific from 1989 to 2000 (most from 1994-1998). The swordfish were captured by various commercial fishermen (with stomachs collected by the Pacific Islands Region Observer Program) or during PIFSC research cruises. Prey items from the stomachs were identified to the lowest taxonomic rank possible, enumerated, weighed, and measured, primarily by Bruce Mundy, Michael Seki, Happy Williams, Alan Everson, with assistance from Fisheries Observers from the Pacific Islands Regional Office. Associated data on fish length, weight, collection year, month, and location were obtained from observer, fishermen, or cruise data records, or from whole fish brought to the laboratory.