Unraveling the Ecological Importance of Elasmobranchs

Heithaus, Michael R.; Frid, Alejandro; Vaudo, Jeremy J.; Worm, Boris; Wirsing, Aaron J.

doi:10.1201/9781420080483-c16

Cited by 100 publications

(89 citation statements)

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“…Sevengill sharks are considered to be one of the most important apex predators in temperate coastal systems (Ebert 2002;Lucifora et al 2005) and, given the diversity of their diet, may be taking advantage of a niche vacated by other species with reduced populations. Similar niche occupation has been postulated for tiger sharks in more tropical environs (Heithaus et al 2010).…”

Section: Discussionmentioning

confidence: 76%

Decadal trends in shark catches and effort from the New South Wales, Australia, Shark Meshing Program 1950 - 2010

Reid

Robbins

Peddemors

2011

Mar. Freshwater Res.

126

115

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Abstract. The New South Wales (NSW) government has operated a program of netting beaches for the protection of swimmers and surfers against shark attack since 1937 in Sydney, and since 1949 in Newcastle and Wollongong. The scope and directives of the Shark Meshing Program have remained constant since its inception, with operational modifications in net specifications in 1972, changes in spatial deployment in 1972, 1987 and 1992, and the elimination of winter netting since 1989. This markedly increased meshing effort in 1972, and again in 1987. In the present study, we examine the trends in catch and effort for the period from 1950-1951 to 2009-2010 over this 200-km section of the NSW coast. Significant temporal trends in species, size and sex composition are described herein. Catches were consistently dominated by three shark taxa, hammerhead sharks (Sphyrna spp.), whaler sharks (Carcharhinus spp.) and Australian angel sharks (Squatina australis), although their relative contributions to catches varied over time. Catch per unit effort has significantly declined for five of the most abundant shark taxa over the study period, increasing only for a single taxon, the sevengill shark (Notorynchus cepedianus). Catches of larger, potentially dangerous white sharks (Carcharodon carcharias) and tiger sharks (Galeocerdo cuvier) saw fewer large animals being caught over time. This pattern was not observed across other taxa. Four different monthly trends were observed in landings of the most abundant eight taxa, reflecting differences in the biology of the catch species. The current study also provides useful information on catches and sizes of grey nurse (Carcharias taurus) and white sharks before and after their protection in NSW waters in 1984 and 1998, respectively.

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Section: Discussionmentioning

confidence: 76%

Decadal trends in shark catches and effort from the New South Wales, Australia, Shark Meshing Program 1950 - 2010

Reid

Robbins

Peddemors

2011

Mar. Freshwater Res.

126

115

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“…Being top predators makes them important in controlling lower trophic levels (Stevens et al, 2000;Myers et al, 2007;Heithaus et al, 2008;Navia et al, 2010). Thus, the reduction of their populations may result, through trophic cascade effects, in changes in marine populations (Ferretti et al, 2010;Heithaus et al, 2010).…”

Section: Short Communicationmentioning

confidence: 99%

Diet of the bull shark, Carcharhinus leucas, and the tiger shark,Galeocerdo cuvier, in the eastern Pacific Ocean

et al. 2017

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Sharks are apex predators in marine ecosystems and play an important role in regulating prey populations at lower trophic levels (e.g., fish, invertebrates, reptiles, mammals and birds) (Ellis et al., 1996).The bull shark, Carcharhinus leucas (Müller and Henle, 1839), and the tiger shark, Galeocerdo cuvier (Péron and Lesueur, 1822), are common worldwide in tropical and subtropical coastal areas (Compagno, 1984). The bull shark grows to a large size (over 340 cm) (Compagno, 1984) and frequently inhabits shallow water (max. depth 30 m) (Compagno, 1984). It is one of the few shark species that is physiologically capable of spending time in fresh water (Pillans and Franklin, 2004) and has been reported in rivers and lakes (Thorson et al., 1973;Thomerson et al., 1977;Montoya and Thorson, 1982; Simpendorfer et al., 2005). The tolerance of bull sharks for low-salinity conditions allows them to frequent areas close to shore and near river mouths, where they may interact with other shark species (Carlson et al., 2010). The tiger shark reaches a larger size than the bull shark (over 550 cm) (Compagno, 1984), with a wide tolerance for different marine habitats at depths ranging from the surface to 140 m. This species

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“…Los batoideos, con un nivel trófico bajo (<4), están considerados como consumidores secundarios cuando son comparados con la mayoría de las especies de tiburones. Sin embargo, todavía se desconoce el nivel trófico estándar de muchos de ellos (Heithaus et al 2010). Se predice que los batoideos tienen un papel crítico en la dinámica de los ecosistemas marinos como especies depredadoras a niveles intermedios (Ritchie …”

Section: Introductionunclassified

“…Batoids occupy lower trophic levels (<4) and are considered secondary consumers when compared with most of the large shark species. Still, most of the standardized trophic levels of several batoid species have yet to be estimated (Heithaus et al 2010). It is predicted that batoids play a critical role in the dynamics of marine ecosystems as predator species at intermediate levels (Ritchie and Johnson 2009), where they are a significant link in food webs in the demersal marine communities (Belleggia et al 2008) and an important component of the community structure (Braccini and Perez 2005, Heithaus et al 2008.…”

Section: Introductionmentioning

confidence: 99%

Feeding habits of the speckled guitarfish Rhinobatos glaucostigma (Elasmobranchii, Batoidea) in the southeastern Gulf of California

Rosa-Meza

Cueva

2013

Cienc. Mar.

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INTRODUCCIÓNEn el nivel más básico, el papel ecológico de una especie se define por su posición en la red trófica. Los batoideos, con un nivel trófico bajo (<4), están considerados como consumidores secundarios cuando son comparados con la mayoría de las especies de tiburones. Sin embargo, todavía se desconoce el nivel trófico estándar de muchos de ellos (Heithaus et al. 2010). Se predice que los batoideos tienen un papel crítico en la dinámica de los ecosistemas marinos como especies depredadoras a niveles intermedios (Ritchie ABSTRACT.To assess the feeding habits of Rhinobatos glaucostigma (speckled guitarfish), the stomach contents of 176 individuals were examined. Specimens were obtained from the artisanal gillnet fisheries operating off Nayarit, Mexico, in the southeastern region of the Gulf of California, during January-August 2008 and January-May 2009. Relative measures of prey quantities and nonparametric multivariate methods were used to analyze diet differences between sex and maturity stages. The trophic relationship and feeding strategy were determined using Levin's niche amplitude index, the Costello method modified by Amundsen, and Pianka's diet overlap index. The overall diet was dominated by crustaceans, primarily decapods, brachyurans, and cumaceans. Diets were similar between sexes and maturity stages, except between mature females and males where only slight differences were found. Mature females and immature specimens of both sexes showed specialized diets, while mature males had a generalist diet. A significant overlap between sexes and maturity stage diets was found. Diet compositions allowed us to estimate a standardized trophic level of 3.57 for R. glaucostigma. The diet compositions between sexes and maturity stages suggest that all individuals consume similar prey items and have similar trophic roles in the benthic community of the southeastern region of the Gulf of California, where R. glaucostigma should be considered a secondary consumer.Key words: guitarfish diet, feeding strategy, trophic level, diet overlap, feeding habitat.RESUMEN. Para caracterizar los hábitos alimentarios de Rhinobatos glaucostigma (guitarra punteada), se muestrearon los contenidos estomacales de 176 individuos. Los especímenes fueron capturados con redes agalleras por la pesca artesanal que opera frente a Nayarit, México, en la región sureste del golfo de California, durante los periodos de enero a agosto de 2008 y de enero a mayo de 2009. Para analizar las diferencias de dieta entre sexos y estadios de madurez, se utilizaron las medidas relativas de cuantificación de dieta y métodos no paramétricos multivariados. Las relaciones tróficas y la estrategia de alimentación fueron determinadas con el índice de amplitud de nicho de Levin, el método gráfico de Costello modificado por Amundsen y el índice de traslapo de dietas de Pianka. La dieta global estuvo dominada por crustáceos, principalmente por decápodos, braquiuros y cumáceos. Las dietas fueron similares entre sexos y estadios de madurez, excepto entre hemb...

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Unraveling the Ecological Importance of Elasmobranchs

Cited by 100 publications

References 0 publications

Decadal trends in shark catches and effort from the New South Wales, Australia, Shark Meshing Program 1950 - 2010

Decadal trends in shark catches and effort from the New South Wales, Australia, Shark Meshing Program 1950 - 2010

Diet of the bull shark, Carcharhinus leucas, and the tiger shark,Galeocerdo cuvier, in the eastern Pacific Ocean

Feeding habits of the speckled guitarfish Rhinobatos glaucostigma (Elasmobranchii, Batoidea) in the southeastern Gulf of California

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