Abstract:Erroneous standard error values of the percentage index of relative importance (%IRI) were presented in the above article (see Figure 3); leading to the unsubstantiated conclusion that %IRI calculations were much less precise than those of the percentage geometric index of importance (%GII). When corrected, standard error estimates of %IRI were actually only slightly less precise than those of %GII. For example, %IRI and %GII values (mean ± SE) corresponding to the most important prey taxa of the sandpaper ska… Show more
“…However, according to Bizzarro et al . (2007), curves for both groups did not reach an asymptote since slopes were significantly different from a zero slope ( P < 0.05). Fig.…”
Section: Resultsmentioning
confidence: 84%
“…Yet, according to Bizzarro et al . (2007), sample sizes should be increased to improve the quantitative description of the diet. In addition, previous studies of the diets of Alopias have found a greater number of prey (20–27 taxa; Preti et al ., 2001, 2004; Polo-Silva, 2004; Polo-Silva & Grijalba-Bendeck, 2007; Polo-Silva et al ., 2009).…”
Section: Discussionmentioning
confidence: 99%
“…A more rigorous procedure proposed by Bizzarro et al . (2007) establishes that to determine if a cumulative prey curve reaches an asymptote, the slope of the line generated from the endpoints should be compared to a line of zero slope (horizontal asymptote). The endpoints consist of the mean cumulative number of prey taxa generated for the final four stomach samples.…”
Section: Cumulative Prey Curvesmentioning
confidence: 99%
“…The endpoints consist of the mean cumulative number of prey taxa generated for the final four stomach samples. Slopes are statistically compared using a Student's t -test and slopes that are not significant ( P > 0.05), indicate that the curve reached an asymptote (Bizzarro et al ., 2007).…”
The stomach contents of thresher sharks (Alopias spp.; 162–385 cm total length) were collected from five landing points in northern Peru during 2015. A total of 128 thresher sharks were sampled, with 38 individuals identified as Alopias pelagicus and 90 aggregated to the genus level Alopias sp. to prevent any misidentification. The diet comprised 13 and 10 prey taxa for Alopias sp. and A. pelagicus, respectively. Humboldt squid Dosidicus gigas dominated the diet of both groups, with only minor differences in the diet in relation to size classes and location. The diet of Alopias shows a high degree of specialization and the average trophic positions were high for both groups, A. pelagicus (4.4 ± 0.13) and Alopias sp. (4.5 ± 0.14).
“…However, according to Bizzarro et al . (2007), curves for both groups did not reach an asymptote since slopes were significantly different from a zero slope ( P < 0.05). Fig.…”
Section: Resultsmentioning
confidence: 84%
“…Yet, according to Bizzarro et al . (2007), sample sizes should be increased to improve the quantitative description of the diet. In addition, previous studies of the diets of Alopias have found a greater number of prey (20–27 taxa; Preti et al ., 2001, 2004; Polo-Silva, 2004; Polo-Silva & Grijalba-Bendeck, 2007; Polo-Silva et al ., 2009).…”
Section: Discussionmentioning
confidence: 99%
“…A more rigorous procedure proposed by Bizzarro et al . (2007) establishes that to determine if a cumulative prey curve reaches an asymptote, the slope of the line generated from the endpoints should be compared to a line of zero slope (horizontal asymptote). The endpoints consist of the mean cumulative number of prey taxa generated for the final four stomach samples.…”
Section: Cumulative Prey Curvesmentioning
confidence: 99%
“…The endpoints consist of the mean cumulative number of prey taxa generated for the final four stomach samples. Slopes are statistically compared using a Student's t -test and slopes that are not significant ( P > 0.05), indicate that the curve reached an asymptote (Bizzarro et al ., 2007).…”
The stomach contents of thresher sharks (Alopias spp.; 162–385 cm total length) were collected from five landing points in northern Peru during 2015. A total of 128 thresher sharks were sampled, with 38 individuals identified as Alopias pelagicus and 90 aggregated to the genus level Alopias sp. to prevent any misidentification. The diet comprised 13 and 10 prey taxa for Alopias sp. and A. pelagicus, respectively. Humboldt squid Dosidicus gigas dominated the diet of both groups, with only minor differences in the diet in relation to size classes and location. The diet of Alopias shows a high degree of specialization and the average trophic positions were high for both groups, A. pelagicus (4.4 ± 0.13) and Alopias sp. (4.5 ± 0.14).
“…In addition, a quantitative criterion for assessing sample-size sufficiency was used to determine whether the cumulative prey curves approached an asymptote, by comparing the slope of the line generated from the curve's four last points to a slope of zero through a Student's t -test. If the slopes were not significantly different ( P > 0.05), the prey curve was considered to approach an asymptote (Bizzarro et al ., 2007). Sample-size sufficiency could not be tested for individual size classes because of the small number of individuals in each class.…”
As apex predators, sharks are known to play an important role in marine food webs. Detailed information on their diet and trophic level is however needed to make clear inferences about their role in the ecosystem. A total of 335 stomachs of smooth hammerhead sharks, Sphyrna zygaena, were obtained from commercial fishing vessels operating in the Ecuadorian Pacific between January and December 2004. A total of 53 prey items were found in the stomachs. According to the Index of Relative Importance (%IRI), cephalopods were the main prey (Dosidicus gigas, Sthenoteuthis oualaniensis, Ancistrocheirus lesueurii and Lolliguncula [Loliolopsis] diomedeae). Sphyrna zygaena was thus confirmed to be a teutophagous species. The estimated trophic level of S. zygaena was between 4.6 and 5.1 (mean ± SD: 4.7 ± 0.16; males: 4.7; females: 4.8). Levin's index (BA) was low (overall: 0.07; males: 0.08; females: 0.09), indicating a narrow trophic niche. We found that sharks <150 cm in total length consumed prey of coastal origin, whereas sharks ≥150 cm foraged in oceanic waters and near the continental shelf. The analyses indicate that S. zygaena is a specialized predator consuming mainly squids.
Blue Catfish Ictalurus furcatus (Figure 1) are an invasive species found in high abundance throughout the Chesapeake Bay (Bunch et al., 2018;Fabrizio et al., 2018). Originally introduced to establish a fishery, Blue Catfish expanded throughout the Chesapeake Bay ecosystem (Schloesser et al., 2011). Blue Catfish have been documented in excess of 5 feet and 100 pounds (Graham, 1999). Size combined
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
