Isurus oxyrinchus (Indo-west Pacific subpopulation)
|Scientific Name:||Isurus oxyrinchus (Indo-west Pacific subpopulation)|
|Red List Category & Criteria:||Vulnerable A2bd+4d ver 3.1|
|Assessor(s):||Cailliet, G.M., Cavanagh, R.D., Kulka, D.W., Stevens, J.D., Soldo, A., Clo, S., Macias, D., Baum, J., Kohin, S., Duarte, A., Holtzhausen, J.A., Acuña, E., Amorim, A. & Domingo, A.|
|Reviewer(s):||Fowler, S.L., Dudley, S., Soldo, A., Francis, M. & SSG Pelagic Shark Red List Workshop participants (Shark Red List Authority)|
Shortfin Mako (Isurus oxyrinchus) is taken by tuna and shark longline fisheries in Indonesia (White et al. 2006), and throughout many areas of its range in the Indo-West Pacific. Pelagic fisheries have operated in the Indian Ocean for more than 50 years. Sharks are targeted in several areas in this region, including off India where they are captured using hook and line and in the worlds largest mesh gillnets. Finning and discarding of carcasses has been reported, especially in offshore and high seas fisheries. Most artisanal and industrial marine fisheries in the Indian Ocean are multispecies and the state of most resources is poorly documented. A recent review of fisheries in the Indian Ocean reported that sharks in this region are considered fully to over-exploited. Its distribution overlaps many intensive pelagic fisheries in this area. Although species-specific data are not currently available from this region for evaluation, given the declines observed where it is heavily fished in the north Atlantic, declines in this area are inferred based on continuing high levels of exploitation.
|Range Description:||Indo-West Pacific: South Africa (east coast), Mozambique, Madagascar, Mauritius and Kenya north to Red Sea and east to Maldives, Iran, Oman, Pakistan, India, Indonesia, Viet Nam, China, Taiwan (Province of China), North Korea, South Korea, Japan, Russia (Primorskiyi Kray), Australia (all states and entire coast except for Arafura Sea, Gulf of Carpentaria and Torres Strait), New Zealand (including Norfolk Island), New Caledonia, Fiji.|
Native:Australia (Lord Howe Is., Macquarie Is., New South Wales, Queensland, South Australia, Tasmania, Victoria, Western Australia); China; Fiji; India; Indonesia; Iran, Islamic Republic of; Japan (Hokkaido, Honshu, Kyushu, Nansei-shoto, Shikoku); Kenya; Korea, Democratic People's Republic of; Korea, Republic of; Madagascar; Malaysia (Peninsular Malaysia, Sabah, Sarawak); Maldives; Mauritius (Mauritius (main island)); Mozambique; New Caledonia; New Zealand (Antipodean Is., Chatham Is., Kermadec Is., North Is., South Is.); Oman; Pakistan; Russian Federation (Primoryi); Somalia; South Africa (Eastern Cape Province, KwaZulu-Natal); Sri Lanka; Taiwan, Province of China (Taiwan, Province of China (main island)); Viet Nam
|FAO Marine Fishing Areas:|
Indian Ocean – western; Indian Ocean – eastern; Pacific – northwest; Pacific – southwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Habitat and movements|
The Shortfin Mako is an active, offshore littoral and epipelagic species, found in tropical and warm-temperate seas from the surface down to at least 500 m, seldom occurring where water temperature is <16°C (Compagno 2002). It is probably the fastest shark and is among the most active and powerful of fishes. Like other lamnid sharks, the Shortfin Mako,is endothermic using a heat-exchanging circulatory system to maintain muscle and visceral temperatures above that of the surrounding seawater allowing a higher level of activity (Carey et al. 1981, Bernal et al. 2001).This shark occurs well offshore but penetrates the inshore littoral just off the surf zone in some areas such as parts of KwaZulu-Natal, South Africa where the continental shelves are narrow. Off South Africa, shark meshing data suggests that this species occurs in clear to turbid water in water temperatures from 17–22°C. In the western north Atlantic it occurs in a similar range of temperatures, and only moves onto the continental shelf when surface temperatures exceed 17°C. In the eastern north Pacific, juveniles range into southern California waters and tend to be seen and caught near the surface. They appear to use these offshore continental waters as nursery areas (Taylor and Holts 2001). It was previously thought that they stay near the surface above 20 m depth, in waters between 20–21°C, seldom descending into cold subsurface waters below the thermocline (Holts and Bedford, 1992). However,this has been challenged by more recent tracking studies (summarized below).
Results from a large tagging study in the western north Atlantic show that Shortfin Makos make extensive movements of up to 3,433 km with 36% of recaptures caught at greater than 420 km from their tagging site (Casey and Kohler 1992). However, only one fish crossed the mid-Atlantic ridge suggesting that trans-Atlantic migrations are not as common as in blue sharks Prionace glauca.
Klimley et al. (2002) tracked three Shortfin Makos near La Jolla, California, for several days, and their movements were mainly offshore from the surface to 50 m. Holts and Kohin (2003) deployed pop-up archival tags on eight makos (118–275 cm TL) in June–July 2002 for 2–4 months. Pop-up locations ranged from 20–911 km from deployment locations. The sharks utilized near-shore and open-water areas off California and Baja California roughly between 23–43°N and out to 125°W. While the records indicate that greater than 90% of the time was spent above 50 m, several sharks showed a diurnal pattern of vertical excursions to beyond 200 m during daylight hours. Sharks frequently dove into water less than 10°C. These data demonstrate the range of habitats utilized by mako sharks and begin to shed light on their daily and seasonal behaviors. Sepulveda et al. (2004) found that seven tagged juveniles stayed near the surface at night, and went as deep as 200 m, mostly during the day. In addition, stomach temperatures were measured, indicating feeding occurred during the daytime, with meals taken during a dive causing stomach temperatures to drop noticeably.
Life History Parameters
The Shortfin Mako reaches a maximum size of about 4 m (Compagno 2001). Initial age and growth studies in the western north Atlantic suggested that two pairs of growth bands are laid down each year in their vertebral centra, at least in young shortfin makos (Pratt and Casey 1983). However, recent evidence using marginal increment analysis in Mexico (Ribot-Carballal et al. 2005) and bomb radiocarbon (Campana et al. 2002, Ardizzone et al. 2006) indicates that the alternative hypothesis (one pair of growth bands per year; Cailliet et al. 1983) is valid. Age at maturity has been determined recently in several populations, including New Zealand (7–9 years for males, and 19–21 years for females Bishop et al. (2006)), and the western north Atlantic (eight years for males, and 18 years for females (Natanson et al. 2006)). Longevity has been estimated as 29–32 years (Bishop et al. 2006, Natanson et al. 2006).
There is a large difference in size at sexual maturity between the sexes. In the northwest Atlantic, males reach maturity at about 195 cm and females at about 265–280 cm (Pratt and Casey 1983, Stevens 1983, Cliff et al. 1990). In New Zealand, males mature at 198–204 cm and females at 301–307 cm (Francis and Duffy 2005). Compagno (2001) reports males mature between 203–215 cm, reaching a maximum size of 296 cm, and females mature between 275–293 cm, reaching a maximum of almost 4 m.
The Shortfin Mako is ovoviviparous and oophagous, but what little is known of its reproductive cycle indicates the gestation period is 15–18 months, with a three year reproductive cycle (Mollet et al. 2000). Litter size is 4–25 pups (possibly up to 30, mostly 10-18), which are about 60-70 cm long at birth (Garrick 1967, Compagno 2001). There are comparatively few records of pregnant females. Among 26 shark species, the Shortfin Mako has an intrinsic rebound potential (a measure of its ability to recover from exploitation) in the mid-range (Smith et al. 1998). The annual rate of population increase is 0.046 yr-1 (S. Smith pers. comm.) Cortes (2002) calculated a finite rate of increase (lambda) of 1.141 (1.098 to 1.181 95% CI, r = 0.13) and the average reproductive age as 10.1 (9.2 to 11.1 95% CI) years.
The diet of Shortfin Makos has been reported to consist mainly of teleost fishes (including mackerels, tunas, bonitos and other scombrids, anchovies, herrings, grunts, lancet fishes, cod, ling, whiting and other gadids, salmon, yellowtails and other carangids, sea basses, porgies, swordfish) and cephalopods in studies from the Northwest Atlantic and Australia (Stillwell and Kohler 1982, Stevens 1984), while elasmobranchs were the most common prey category from Natal, South Africa (Cliff et al. 1990). A daily ration of 2 kg/day (based on an average weight of 63 kg) was estimated for makos in the northwest Atlantic (Stillwell and Kohler 1982). Large makos over (3 m in length) have very broad, more flattened and triangular teeth, perhaps better suited to cutting large prey than the awl-shaped teeth of smaller individuals (Compagno 1984a). There are several anecdotal accounts of makos attacking and consuming Broad-bill Swordfish (Xiphias gladius). It also eats sea turtles, dolphins, salps and occasionally detritus (Compagno 1984a).
|Movement patterns:||Full Migrant|
|Use and Trade:||
This is one of the most valuable shark species for its high quality meat. The meat is utilized fresh, frozen, smoked and dried-salted for human consumption; the oil is extracted for vitamins; the fins used for shark-fin soup; the hides are processed into leather and the jaws and teeth are used for ornaments (Compagno 2001).
Big-game sports angling for mako sharks is widespread, e.g. New Zealand, South Africa and California - see Threats section above for more information.
Makos have become the subject of ecotourism diving in recent years, with most of the mako dive sites being off southern California from the Los Angeles Basin to San Diego, but with sites also in South Africa and the Maldives (Compagno 2001).
This species is taken by tuna and shark longline fisheries in Indonesia (White et al. 2006) and throughout many areas of its range in the Indo-West Pacific. Pelagic fisheries have operated in the Indian Ocean for more than 50 years; Japanese long-liners in the eastern Indian Ocean since 1952 and in the western region since 1956. Russian, Taiwanese and South Korean vessels have fished there since 1954-1966 (Gubanov and Paramonov 1993). The Spanish swordfish longline fishery, which also targets sharks, is also active across the Indian Ocean (ICCAT 2006). Sharks are targeted in several areas, including off India where they are captured using hook and line and in large mesh gillnets, which are among the worlds largest (Anderson and Simpfendorfer 2005). Finning and discarding of carcasses has also been reported, especially in offshore and high seas fisheries (Anderson and Simpfendorfer 2005). A recent review of fisheries in the Indian Ocean (Young et al. 2006) reported that sharks in this region are considered fully to over-exploited. Its distribution overlaps many intensive pelagic fisheries in this area. Although species-specific catch data are not currently available from this region, given the declines observed where it is heavily fished elsewhere, declines in this area are inferred based on continuing high levels of exploitation.
Big-game sports angling for mako sharks is widespread, New Zealand and South Africa being traditional places for offshore sports fishing.
No direct conservation measures in place in the Indo-west Pacific region.
New Zealand included Shortfin Mako shark in its Quota Management System in October 2004.
A vast improvement in the collection of data is required and effective conservation of this species will require international agreements. Fishing pressure must be considerably decreased through reduction in effort, catch limits, measures to enhance chances of survival after capture, when released and possibly through the implementation of large-scale oceanic non-fishing areas. Closed areas can only be effective if overall fishing effort is reduced, rather than merely displacing effort outside of the closed area (Baum et al. 2003).
Further informaiton is required on this population, it's range and interactions with fisheries.
|Citation:||Cailliet, G.M., Cavanagh, R.D., Kulka, D.W., Stevens, J.D., Soldo, A., Clo, S., Macias, D., Baum, J., Kohin, S., Duarte, A., Holtzhausen, J.A., Acuña, E., Amorim, A. & Domingo, A. 2009. Isurus oxyrinchus (Indo-west Pacific subpopulation). The IUCN Red List of Threatened Species 2009: e.T161750A5495661.Downloaded on 19 March 2018.|