Data Management Plan (Deprecated)

A reassessment of the diet of the Atlantic sharpnose shark Rhizoprionodon terraenovae was conducted to provide an update on their trophic level (n390). Rhizoprionodon terraenovae primarily consume teleost fish however, loggerhead sea turtles Caretta caretta were also found in the diet for the first reported time. Analysis suggests that calculated trophic level may significantly depend on geographic area, thus adding a new factor to fishery management decisions.

Atlantic Ocean, U.S. South

Process Steps:

• Rhizoprionodon terraenovae were collected by onboard National Marine Fisheries Service contract fishery observers in the Florida shark drift gillnet fishery from 2001 to 2005 (n390). All R. terraenovae were collected in areas off the east coast of Florida ranging from 27 05 to 28 43 N. A complete description of the observer program and shark processing is detailed in Carlson Bethea (2006). Rhizoprionodonterraenovae were randomly selected from the catch, and fork length (LF) andsex were recorded. Stomachs were removed and immediately frozen or stored on iceprior to transport. At the laboratory, stomachs were stored in a large walk-in freezer(c. -12 C) until dissection. Upon dissection, prey items were identified to the lowestpossible taxonomic level, counted, measured and weighed wet (with a precision of001 g).A cumulative prey curve was created to determine if sample size was sufficient toaccurately describe diet. The order of stomach analysis was randomized 10 times,and the mean number of new prey species found in consecutive stomachs was plottedagainst the number of non-empty stomachs. The existence of an asymptotic relationshipindicates that sample size is adequate to represent overall dietary habits (Cailliet et al.,1986 Ferry Cailliet, 1996). The final 10 values of the cumulative prey curve weresignificantly different from a slope0 (t 4669, P001), and the slope increased at589. While greater sampling could yield an even more comprehensive analysis ofR. terraenovae diet, the slope was only slightly higher than the threshold of 5 (Ferry Calliet, 1996), indicating that the diets were well described overall.Published 2014. This article is a U.S. Government work and is in the public domain in the USA.Journal of Fish Biology 2015, 86, 385391DIET AND TROPHIC ANALYSIS OF R . TERRAENOVAE 387Diet was analysed following Corts (1997) using four standard indices: per cent bynumber (N), per cent by mass (W), per cent frequency of occurrence (O) (Hyslop,1980) and the index of relative importance (IRI Piankas et al., 1971). The IRI wasused to facilitate comparison with previous diet studies and was calculated as IRI O(N W). The IRI was then expressed on a per cent basis (IRI Corts, 1997) by summing all IRI values for every prey item and then dividing each individual IRI valueby the total.To calculate the TL, the stomach contents were pooled into eight major diet categories:cephalopods, chondrichthyans, decapods, teleosts, invertebrates (excludingdecapods and molluscs), molluscs, marine plants and marine reptiles (Corts, 1999).Each prey category was assigned an average trophic level, TLj, based on estimatesaggregated by Corts (1999) in order to compare values. The TL was expressed asTL 1 8Sj1PjTLj, where Pj is the proportion by IRI of each category.The means.d. TL calculated for R. terraenovae was 4201, with the teleost preycategory comprising 9103 IRI, followed by invertebrates (excluding decapods) at261 IRI and decapods at 200 IRI (Table II). While the majority of fishes in thediet was unidentifiable, the increase in TL from Corts (1999) is due to an increase infish consumption (664 v. 910 IRI) over crustaceans (316 v. 26 IRI). Comparisonof the IRI of the four major prey categories between this study, Gelsleichter et al.(1999), Bethea et al. (2006) and Drymon et al. (2012) shows that results reported byDrymon et al. (2012) and Bethea et al. (2006) closely resemble the findings reportedhere, with a very high IRI of teleosts. While the percentages were similar, each study reported unique prey items not found in the other studies, thus demonstrating regional differences.

Findings from this dataset are published in a peer-reviewed journal. This is a static data set that has undergone rigorous QA/QC prior to publication.

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