Sharks caught in the protective gill nets off Natal, South Africa. 3. The shortfin mako shark<i>Isurus oxyrinchus</i>(Rafinesque)

Cliff, Geremy; Dudley, Sheldon F.; Davis, B. N. K.

doi:10.2989/025776190784378808

Cited by 59 publications

(44 citation statements)

References 4 publications

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“…Growth curves from our study and from the north-west Atlantic (L. Natanson, unpublished data) were similar, indicating little regional variability in growth rates. Similarly, length at maturity is similar in New Zealand and elsewhere, except perhaps for females from South Africa which may mature at a shorter length (Cliff et al 1990;Francis & Duffy in prep). It therefore seems that makos worldwide may mature at similar ages.…”

Section: Age At Maturitymentioning

confidence: 65%

Age, growth, maturity, longevity and natural mortality of the shortfin mako shark (Isurus oxyrinchus) in New Zealand waters

Bishop

Francis

Duffy³

et al. 2006

Mar. Freshwater Res.

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EXECUTIVE SUMMARY BishopShortfin mako sharks were aged by counting growth bands in sectioned vertebrae collected from recreational fishing competitions and the tuna longline fishery. Replicate counts were made from images taken under reflected light. No systematic ageing bias was present within or between readers and count precision was high. Growth is rapid in early years and quickly declines. Vertebral data showed that males and females grow at similar rates until age 7-9 years, after which the relative growth of males declines. Von Bertalanffy growth parameters were: male L ∞ = 302.16 cm fork length (FL), K = 0.0524 and t 0 = -9.04 years: female L ∞ = 732.41 cm FL, K = 0.0154 and t 0 = -10.79 years. MULTIFAN analysis of length-frequency data from the tuna longline fishery estimated substantially faster growth than that derived from vertebral ages. MULTIFAN growth rates were considered reliable up to age 2-3 years, and thereafter vertebral ages were more reliable. Longevity estimates based on the maximum ages from vertebral band counts were 29 and 28 years for males and females respectively. Natural mortality estimates calculated from Hoenig's (1983) equation were 0.14 for males and 0.15 for females. Ages at 50% maturity determined by probit analysis of paired age and maturity data were 6.9 years for males and 19.1 years for females. Indirect age at maturity estimates from conversion of length at maturity data were 8-9 years for males and 20-21 years for females. Median maturity in males corresponded with the age at which male growth rate declined.The shortfin mako is a large, slow-growing, and late-maturing species with high longevity and low natural mortality. Comparison of growth curves reported here with overseas studies suggest that there are no regional differences in growth rates. Stock size and structure are unknown for this species internationally, and management should be of a precautionary nature.

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Section: Age At Maturitymentioning

confidence: 65%

Age, growth, maturity, longevity and natural mortality of the shortfin mako shark (Isurus oxyrinchus) in New Zealand waters

Bishop

Francis

Duffy³

et al. 2006

Mar. Freshwater Res.

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“…All these odontocete remains were thought to have been scavenged. In South Africa, mako sharks primarily feed on other elasmobranchs and teleosts (Cliff, Dudley & Davis, 1990), and prey size was 23±35% of the body length of the attacking shark. The above studies did not contain many large sharks, and this may bias the view of mako shark predation on odontocetes.…”

Section: Suspected Predatorsmentioning

confidence: 99%

Predator–prey and competitive interactions between sharks (order Selachii) and dolphins (suborder Odontoceti): a review

2001

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The importance of interactions between sharks and cetaceans has been a subject of much conjecture, but few studies have addressed these interactions. Sharks (order Selachii) have been hypothesized to be important predators on dolphins and porpoises (suborder Odontoceti). Unfortunately, there are often few data to back up claims that certain shark species are major threats to cetaceans. To help identify potential shark predators in speci®c locations, available data on interactions with odontocetes for all shark species that may include cetaceans in their diet are reviewed. Shark species are categorized into groups based on predatory interactions with dolphins and porpoises (regular predators, occasional predators, potential predators, ectoparasites and insuf®cient data). Several shark species that have been overlooked in the cetacean literature are identi®ed as potentially important predators while others that have been suspected to be important predators are probably at most occasional predators. How shark predation can in¯uence dolphin populations, habitat use, group size and behaviour is discussed. How risk of shark predation can vary with habitat attributes in both nearshore and pelagic waters is also discussed. Predator±prey interactions have been the focus of most studies of shark±dolphin interaction, but competitive interactions may also occur. The ®rst analysis of shark±dolphin dietary overlap is presented, which shows it to be signi®cant between common dolphins and several species of sharks, including species that prey upon these dolphins.

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“…Cliff et al (1990) found more large males than females in coastal bather 59 protection nets in eastern South Africa, and catches increased in winter and spring. 60…”

mentioning

confidence: 99%

Population structure and biology of shortfin mako, Isurus oxyrinchus, in the south-west Indian Ocean

Groeneveld

Cliff

Dudley³

et al. 2014

Mar. Freshwater Res.

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14The population structure, reproductive biology, age and growth, and diet of shortfin 15 makos caught by pelagic longliners (2005)(2006)(2007)(2008)(2009)(2010) and bather protection nets (1978-16 2010) in the Southwest Indian Ocean were investigated. The mean fork length (FL) of 17 makos measured by observers on longliners targeting tuna, swordfish and sharks was 18 similar, and decreased from east to west, with the smallest individuals occurring near 19 the Agulhas Bank edge, in June to November. Nearly all makos caught by longliners 20 were immature, with equal sex ratio. Makos caught by bather protection nets were 21 significantly larger, males were more frequent, and 93% of males and 55% of females 22 were mature. Age was assessed from band counts of sectioned vertebrae, and a von 23Bertalanffy growth model fitted to sex-pooled length-at-age data predicted a birth size 24 (L 0 ) of 90 cm, maximum FL (L ∞ ) of 285 cm and growth coefficient (k) of 0.113 y -1 . 25Males matured at 190 cm FL, aged 7 y, and females at 250 cm, aged 15 y. Litter sizes 26 ranged from nine to 14 pups, and the presence of gravid females in bather protection 27 nets suggested that some pupping occurred in shelf waters. Teleosts (mainly 28Trachurus capensis) occurred in 84% of stomachs collected on longliners, whereas 29 elasmobranchs (63.5%) were most common in samples collected from bather 30 protection nets, followed by teleosts (43.1%) and cephalopods (36.5%). Larger prey 31 size may be a factor that attracts large makos to coastal waters. 32 33

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Sharks caught in the protective gill nets off Natal, South Africa. 3. The shortfin mako sharkIsurus oxyrinchus(Rafinesque)

Cited by 59 publications

References 4 publications

Age, growth, maturity, longevity and natural mortality of the shortfin mako shark (Isurus oxyrinchus) in New Zealand waters

Age, growth, maturity, longevity and natural mortality of the shortfin mako shark (Isurus oxyrinchus) in New Zealand waters

Predator–prey and competitive interactions between sharks (order Selachii) and dolphins (suborder Odontoceti): a review

Population structure and biology of shortfin mako, Isurus oxyrinchus, in the south-west Indian Ocean

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