虎鲨在西北大西洋和墨西哥湾的食性
Abstract
Tiger sharks, Galeocerdo cuvier, are apex predators that may structure marine communities through predation. Despite a large number of studies in other areas such as the Pacific Ocean, there are no quantitative data on the diet of tiger sharks in the northwest Atlantic Ocean and Gulf of Mexico. Diet was assessed from 169 tiger sharks by life stage, area, and environmental factors. Fifteen prey groups were identified, with teleosts, molluscs, birds, cephalopods, and reptiles being the predominant prey categories. There was an ontogenetic shift in diet, prey size and diversity. Molluscs were the most common prey in smaller sharks, while teleosts and reptiles became more important in the diet of larger sharks. Dietary overlap was significant by area (Gulf of Mexico vs Atlantic Ocean) and among all life stages except for young-of-the-year and adult tiger sharks. Juvenile tiger sharks also demonstrated selective feeding by targeting gastropod feet over ingesting the entire animal. While results were similar to feeding studies conducted on tiger sharks in other ocean basins, an understanding of area-specific trophic interactions is necessary to inform decision support tools for ecosystem-based approaches to management。
Tiger sharks, Galeocerdo cuvier, are apex predators that may structure marine communities through predation. Despite a large number of studies in other areas such as the Pacific Ocean, there are no quantitative data on the diet of tiger sharks in the northwest Atlantic Ocean and Gulf of Mexico. Diet was assessed from 169 tiger sharks by life stage, area, and environmental factors. Fifteen prey groups were identified, with teleosts, molluscs, birds, cephalopods, and reptiles being the predominant prey categories. There was an ontogenetic shift in diet, prey size and diversity. Molluscs were the most common prey in smaller sharks, while teleosts and reptiles became more important in the diet of larger sharks. Dietary overlap was significant by area (Gulf of Mexico vs Atlantic Ocean) and among all life stages except for young-of-the-year and adult tiger sharks. Juvenile tiger sharks also demonstrated selective feeding by targeting gastropod feet over ingesting the entire animal. While results were similar to feeding studies conducted on tiger sharks in other ocean basins, an understanding of area-specific trophic interactions is necessary to inform decision support tools for ecosystem-based approaches to management。
Introduction
Tiger sharks, Galeocerdo cuvier (Péron and Lesueur,1822), are found in temperate and tropical oceansaround the world, where they reside in ecosystems fromshallow coastal waters to the open ocean (Ebert et al.2013). In the northwest Atlantic Ocean, tiger sharks aretypically found from New England to the Florida Keys,and throughout the Gulf of Mexico (Lea et al. 2015).Both sexes are thought to mature at about 250 cm forklength(Branstetteretal.1987)andcanreachsizeslargerthan 450 cmtotal length(Castro 2010).The Internation-al Union for the Conservation of Nature (IUCN) RedList of Threatened Species currently classifies tigersharks as BNear Threatened^ throughout their range(Simpfendorfer 2009).
Tiger sharks are considered opportunistic foragers,feeding on a broad range of taxa including teleosts, seaturtles, cephalopods, gastropods, crabs, and marinebirds, as well as solid anthropogenic waste (SAW).Tigersharkshavealsobeenfoundtoexhibitontogeneticshifts in their diet. For example, Rancurel and Intes(1982) observed small tiger sharks in New Caledoniafeeding more on reef fish, while larger tiger sharksconsumed turtles, birds, and squid. Lowe et al. (1996)found thatteleostsand cephalopodpreyitems decreasedin frequency as sharks got larger and were replaced byelasmobranchs, crustaceans, turtles, and marinemammals. Simpfendorfer (1992) determined that small-er tiger sharks in Australia fed predominantly on seasnakes and teleosts while larger sharks fed on turtles,birds, and elasmobranchs.Despite a number of studies conducted on tiger sharkfeeding, most comprehensive studies have been fromthe Pacific Ocean. There is little information on the dietof tiger sharks in the Atlantic and Gulf of Mexico, withmost information coming from descriptive studiesconducted in localized regions. For example, Nicholsand Murphy (1916) noted that tiger shark diet includedwhelks, conch, squid, and fish for sharks caught off ofLong Island, New York. Coles (1919) and Bell andNichols (1921) found that tiger sharks caught off ofNorth Carolina ate crabs, birds, other sharks, turtlesandporpoises,whileGudger(1949)foundmarinebirds,turtles, SAW, livestock, fish, conch opercula, horseshoecrabs, and worm tubes inside six tiger sharks collectedin the Florida Keys. Clark and von Schmidt (1965)notedpreyitemsofothersharks,birds,turtles, tunicates,octopuses, crabs, molluscs, jellyfish, and SAW in tigershark stomachs from the Central Gulf Coast of Florida.Taken together, these Pacific and Atlantic studies showtiger sharks feed on a wide variety of prey items thatmay vary by region and age class.Studying the foraging patterns of top level predatorsis important for informing our understanding of theirrole in the ecosystem. Apex predators, such as tigersharks, may impact ecosystem structure and functionthrough feeding and trophic cascades (Estes et al.1998). As studies of diet and feeding patterns contributetodevelopingecosystemmodelsusedinmanagement,itis critical that whenever possible, diet information spe-cific to the area of concern is applied when developingthe ecosystem model. There is a growing interest indevelopingecosystemmodelsforthenorthwestAtlanticOcean to better understand the ecological role of sharks(e.g., Morgan and Sulikowski 2015) but using diet datafrom tiger sharks in the Pacific Ocean would not beappropriate. Accordingly, we quantitatively describethe diet of tiger sharks in the northwest Atlantic Oceanand the Gulf of Mexico by examining diet by life stageand area. We further testthe predictabilityofthe feedingon major prey categories by abiotic factors
Tiger sharks, Galeocerdo cuvier (Péron and Lesueur,1822), are found in temperate and tropical oceansaround the world, where they reside in ecosystems fromshallow coastal waters to the open ocean (Ebert et al.2013). In the northwest Atlantic Ocean, tiger sharks aretypically found from New England to the Florida Keys,and throughout the Gulf of Mexico (Lea et al. 2015).Both sexes are thought to mature at about 250 cm forklength(Branstetteretal.1987)andcanreachsizeslargerthan 450 cmtotal length(Castro 2010).The Internation-al Union for the Conservation of Nature (IUCN) RedList of Threatened Species currently classifies tigersharks as BNear Threatened^ throughout their range(Simpfendorfer 2009).
Tiger sharks are considered opportunistic foragers,feeding on a broad range of taxa including teleosts, seaturtles, cephalopods, gastropods, crabs, and marinebirds, as well as solid anthropogenic waste (SAW).Tigersharkshavealsobeenfoundtoexhibitontogeneticshifts in their diet. For example, Rancurel and Intes(1982) observed small tiger sharks in New Caledoniafeeding more on reef fish, while larger tiger sharksconsumed turtles, birds, and squid. Lowe et al. (1996)found thatteleostsand cephalopodpreyitems decreasedin frequency as sharks got larger and were replaced byelasmobranchs, crustaceans, turtles, and marinemammals. Simpfendorfer (1992) determined that small-er tiger sharks in Australia fed predominantly on seasnakes and teleosts while larger sharks fed on turtles,birds, and elasmobranchs.Despite a number of studies conducted on tiger sharkfeeding, most comprehensive studies have been fromthe Pacific Ocean. There is little information on the dietof tiger sharks in the Atlantic and Gulf of Mexico, withmost information coming from descriptive studiesconducted in localized regions. For example, Nicholsand Murphy (1916) noted that tiger shark diet includedwhelks, conch, squid, and fish for sharks caught off ofLong Island, New York. Coles (1919) and Bell andNichols (1921) found that tiger sharks caught off ofNorth Carolina ate crabs, birds, other sharks, turtlesandporpoises,whileGudger(1949)foundmarinebirds,turtles, SAW, livestock, fish, conch opercula, horseshoecrabs, and worm tubes inside six tiger sharks collectedin the Florida Keys. Clark and von Schmidt (1965)notedpreyitemsofothersharks,birds,turtles, tunicates,octopuses, crabs, molluscs, jellyfish, and SAW in tigershark stomachs from the Central Gulf Coast of Florida.Taken together, these Pacific and Atlantic studies showtiger sharks feed on a wide variety of prey items thatmay vary by region and age class.Studying the foraging patterns of top level predatorsis important for informing our understanding of theirrole in the ecosystem. Apex predators, such as tigersharks, may impact ecosystem structure and functionthrough feeding and trophic cascades (Estes et al.1998). As studies of diet and feeding patterns contributetodevelopingecosystemmodelsusedinmanagement,itis critical that whenever possible, diet information spe-cific to the area of concern is applied when developingthe ecosystem model. There is a growing interest indevelopingecosystemmodelsforthenorthwestAtlanticOcean to better understand the ecological role of sharks(e.g., Morgan and Sulikowski 2015) but using diet datafrom tiger sharks in the Pacific Ocean would not beappropriate. Accordingly, we quantitatively describethe diet of tiger sharks in the northwest Atlantic Oceanand the Gulf of Mexico by examining diet by life stageand area. We further testthe predictabilityofthe feedingon major prey categories by abiotic factors
附加一篇虎鲨的年龄和增长速度，同样来自于墨西哥湾。论文是1987年的。
标题为：A COMPARISON OF THE AGE AND GROWTH OFTHE TIGER SHARK, GALEOCERDO CUVIERI, FROM OFF VIRGINIAAND FROM THE NORTHWESTERN GULF OF MEXIC01
简述：Lengths at age and growth rates for the tiger shark, Galeocerdo cuvieri. in the northwestern Alantic and Gulf of Mexico were estimated from bands formed seasonally in the vertebral centra. The tiger shark grows rapidly compared with many other shark species. Growth rates for Gulf of Mexico juveniles were faster than for Atlantic juveniles. This produced significantly different (P < 0.01) estimates of the parameters of von Bertalanffy curves for the two regional samples. With sexes combined, parameter estimates for the Gulf of Mexico sample were L"" = 388 cm TL. K "" 0.184. to = -1.13 years; for the Atlantic sample they were L"" = 440 cm TL, K = 0.107, to = -2.35 years. Males mature at approximately 310 cm TL, females at 315-320 cm TL, but the regional differences in juvenile growth rates result in different ages at maturity. In the Gulf of Mexico. males mature in 7 years. females in 8 years; in the Atlantic. males and females both mature in approximately 10 years. The largest male and female examined (381 cm TL) were 15 and 16 years of age.
标题为：A COMPARISON OF THE AGE AND GROWTH OFTHE TIGER SHARK, GALEOCERDO CUVIERI, FROM OFF VIRGINIAAND FROM THE NORTHWESTERN GULF OF MEXIC01
简述：Lengths at age and growth rates for the tiger shark, Galeocerdo cuvieri. in the northwestern Alantic and Gulf of Mexico were estimated from bands formed seasonally in the vertebral centra. The tiger shark grows rapidly compared with many other shark species. Growth rates for Gulf of Mexico juveniles were faster than for Atlantic juveniles. This produced significantly different (P < 0.01) estimates of the parameters of von Bertalanffy curves for the two regional samples. With sexes combined, parameter estimates for the Gulf of Mexico sample were L"" = 388 cm TL. K "" 0.184. to = -1.13 years; for the Atlantic sample they were L"" = 440 cm TL, K = 0.107, to = -2.35 years. Males mature at approximately 310 cm TL, females at 315-320 cm TL, but the regional differences in juvenile growth rates result in different ages at maturity. In the Gulf of Mexico. males mature in 7 years. females in 8 years; in the Atlantic. males and females both mature in approximately 10 years. The largest male and female examined (381 cm TL) were 15 and 16 years of age.