scholarly journals Grow fast, die young: Does compensatory growth reduce survival of juvenile blacktip sharks ( Carcharhinus limbatus ) in the western Gulf of Mexico?

2021 ◽  
Author(s):  
Philip Matich ◽  
Jeffrey D. Plumlee ◽  
Mark Fisher
2020 ◽  
Vol 31 ◽  
pp. SC25-SC30
Author(s):  
Sarah R. Alewijnse ◽  
R. J. David Wells

The stomach contents of 90 Blacktip Shark (Carcharhinus limbatus) specimens caught in the northwestern Gulf of Mexico (GOM) were examined. Stomach contents were identified to the lowest possible taxon, and quantified using percent weight, percent number, percent frequency of occurrence, and percent index of relative importance (IRI). Teleosts were the dominant prey group (98.95% IRI), although most were unidentified (61.70% IRI). Of identified teleost species, Atlantic Croaker (Micropogonias undulatus) (28.43% IRI), and Gulf Menhaden (Brevoortia patronus) (2.31% IRI) were the most important. Crustaceans (0.65% IRI), mollusks (0.46% IRI), and elasmobranchs (0.03% IRI) formed a minor component of the diet. Suspected shrimp fishery discards were found in 11% of stomachs, highlighting the potential importance of this food source for the Blacktip Shark. Diet composition did not differ between male and female sharks, but did between juveniles and adults. Juvenile shark diets had greater proportions of unidentified teleost, Clupeidae and Penaeidae, while adult diets had greater proportions of Sciaenidae, Ariidae and cephalopods. Our results were similar, although not identical to, other studies of Blacktip Shark diets in the northwestern GOM. Of note is finding of the mantis shrimp Squilla empusa, a species previously unreported in Blacktip Shark stomach contents. This new finding, the high importance of unidentified teleosts, and the lack of asymptote in the prey accumulation curve emphasize the need for further study of the Blacktip Shark diet in the northwestern GOM.


2016 ◽  
Vol 67 (7) ◽  
pp. 1014 ◽  
Author(s):  
Justin P. Lewis ◽  
William F. Patterson ◽  
John K. Carlson ◽  
Katherine McLachlin

Identifying and protecting shark nurseries is a common management strategy used to help rebuild overfished stocks, yet we know little about connectivity between juvenile and adult populations. By analysing trace metals incorporated into vertebral cartilage, it may be possible to infer natal origin based on nursery-specific chemical signatures. To assess the efficacy of this approach, we collected juvenile blacktip sharks (Carcharhinus limbatus; n = 93) from four regions in the Gulf of Mexico in 2012 and 2013 and analysed their vertebral centra with laser ablation–inductively coupled plasma–mass spectrometry. We observed significant regional differences in six element:Ca ratios in both 2012 and 2013. Multi-element chemical signatures were significantly different among regions and between year-classes. Year-class-specific linear discriminant function analysis yielded regional classification accuracies of 81% for 2012 and 85% for 2013, although samples were not obtained from all four regions in 2012. Combining year-classes resulted in an overall classification accuracy of 84%, thus demonstrating the usefulness of this approach. These results are encouraging yet highlight a need for more research to better evaluate the efficacy of vertebral chemistry to study elasmobranch population connectivity.


2012 ◽  
Vol 28 (5) ◽  
pp. 827-828 ◽  
Author(s):  
W. B. Driggers ◽  
K. M. Hannan ◽  
E. R. Hoffmayer ◽  
J. Jensen

<em>Abstract.</em>—Mexican coastal waters of the Gulf of Mexico serve as nursery areas for many shark species and traditional fishing grounds for artisanal fishermen. To characterize the use of these areas as shark nurseries, obtain information on the biology of juvenile sharks and understand the fishing pressure on these resources, a multiyear study was conducted in Laguna Yalahau, a shallow coastal lagoon located on the northeastern corner of the Yucatán Peninsula. Using primarily gill-net surveys and tagging of juvenile sharks during the late spring months of May–June, our binational research team conducted six expeditions inside the lagoon from 1995 to 2001. Sixty-seven species of teleosts, elasmobranchs, and other marine vertebrates consisting of 5,590 individuals were collected during the surveys. We captured 1,384 sharks of which 99% were neonate, young-of-the-year, or older juvenile blacktip sharks <em>Carcharhinus limbatus</em>, confirming that Laguna Yalahau is a primary nursery for that species. Other sharks collected were lemon shark <em>Negaprion brevirostris</em>, bonnethead <em>Sphyrna tiburo</em>, nurse shark <em>Ginglymostoma cirratum</em>, and Atlantic sharpnose shark <em>Rhizoprionodon terraenovae</em>. Using the Petersen method during 2000 and 2001, we estimated the sampled population size of newborn blacktip sharks in the lagoon to be 726 and 1,066, respectively, born to approximately 189 and 277 maternal females, respectively. Over the course of the study, 1,155 sharks were tagged and released. The recapture rate of tagged sharks by artisanal fishermen was 21.9%, more than five times the rate for similar sharks off the Florida coast, and all recaptures came from the coast of the Yucatán Peninsula. In light of this high recapture rate, it appears that Laguna Yalahau serves as a primary nursery for sharks that have been heavily exploited by Mexican artisanal fishermen.


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