|Scientific Name:||Isurus paucus|
|Species Authority:||Guitart, 1966|
|Red List Category & Criteria:||Vulnerable A2bd+3d+4bd ver 3.1|
|Assessor/s:||Reardon, M.B., Gerber, L. & Cavanagh, R.D.|
|Reviewer/s:||Kyne, P.M., Fowler, S.L., Clarke, S. & Simpfendorfer, C. (Shark Red List Authority)|
The Longfin Mako Isurus paucus is a widely distributed but rarely encountered oceanic tropical shark. This species is known to be caught as bycatch in tropical pelagic longline fisheries for tuna, swordfish and sharks and in other oceanic fisheries, which operate throughout its range, but at much lower ratios than the smaller, more fecund Shortfin Mako Isurus oxyrinchus. Catches are inadequately monitored and underestimated due to common misidentification with Shortfin Makos and because landings do not reflect numbers of individuals finned and discarded at sea. The Shortfin Mako may have undergone significant documented declines in the North (50% or more) and South Atlantic and faces high fishing pressures throughout its epipelagic habitat from commercial longline fleets. Since Longfin Makos are often caught in the same fishing gear, populations are considered also likely to have declined. In addition to the inferred declines, this is a species of conservation concern due to its apparent rarity, large maximum size (>4 m), low fecundity (2 to 8 pups/litter) and continued bycatch in intensive oceanic fisheries. A global assessment of Vulnerable is considered appropriate for this species as a precautionary measure. A vast improvement in the collection of data is required and effective conservation of this species will require international agreements.
|Range Description:||This species appears to be cosmopolitan in tropical and warm temperate waters. However, at present records are sporadic and the complete distribution remains unclear. This is in part due to confusion with the more common Shortfin Mako Isurus oxyrinchus (Compagno 2001).|
Native:Australia (New South Wales, Queensland); Brazil; Cuba; Ghana; Guinea-Bissau; Japan; Liberia; Madagascar; Mauritania; Micronesia, Federated States of ; Morocco; Nauru; Portugal; Solomon Islands; Spain (Canary Is.); Taiwan, Province of China; United States (California, Florida, Hawaiian Is.); Western Sahara
|FAO Marine Fishing Areas:||
Atlantic – eastern central; Atlantic – northeast; Atlantic – northwest; Atlantic – southeast; Atlantic – southwest; Atlantic – western central; Indian Ocean – eastern; Indian Ocean – western; Pacific – eastern central; Pacific – northwest; Pacific – southwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
Seasonally common off central and southern Florida and occurs off of the Bahamas throughout the year (Castro in prep). Common in the Western Atlantic and possibly the Central Pacific, but apparently reported to be rare elsewhere (Compagno 2001). In some areas of its range its occurrence is very poorly known, for example in Australian waters (Stevens and Scott 1995).
Subpopulation structure is unknown but it is possible that Atlantic and Indo-Pacific populations may be isolated.
|Habitat and Ecology:||
A little-known epipelagic, tropical and warm-temperate shark. The species is apparently a deep-dwelling shark, although both sightings on the ocean surface and the species? diet suggest a much greater depth range (Compagno 2001, Castro in prep).
Very little is known of the biology of I. paucus. It is aplacental viviparous with oophagy and uterine cannibalism, and a pregnant female may have 2 to 8 embryos at one time. Parturition size is recorded at 97 to 120 cm TL; females males have been reported as mature at >245 cm TL; the smallest mature male observed has been 229 cm TL; maximum size is around 425 cm TL (Gilmore 1993, Castro et al. 1999, Compagno 2001, Castro in prep). It has been suggested that females may approach land to pup (Compagno 2001).
Life history parameters
Age at maturity (years): Unknown.
Size at maturity (total length): Female: >245 cm TL (Compagno 2001); Male: Smallest reported mature male: 229 cm TL (Castro in prep).
Longevity (years): Unknown. .
Maximum size (total length): At least 426.7 cm TL (Castro in prep.).
Size at birth: 97 to 120 cm (Compagno 2001).
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: 2 to 8 young in a litter (Castro et al. 1999, Compagno 2001).
Annual rate of population increase: Unknown.
Natural mortality: Unknown.
Isurus paucus is of conservation concern due to its apparent rarity or uncommonness, large maximum size, low fecundity (shown to be 2?8 pups/litter), and bycatch in intensive oceanic fisheries (Compagno 2001), (including retention of fins for the international fin trade (Clarke et al. in press). It is probably taken regularly as bycatch in tropical pelagic longline fisheries for tuna, swordfish and shark and in other oceanic fisheries which operate throughout its range, for example, it is also known to be caught with hook and line and anchored gillnets (Amorim et al. 1998, Compagno 2001).
The Longfin Mako is often caught in the same fishing gear as that of the Shortfin Mako, but in much lower ratios (L.J.V. Compagno, pers. comm.). Baum et al. (2003) reported that Shortfin Makos had declined approximately 40% in the Northwest Atlantic over the past 15 years. A recent ICCAT stock assessment workshop reported that stock depletions for North Atlantic Shortfin Mako are likely to have occurred based on CPUE declines of 50% or more. Model results varied widely suggesting, according to one model, that stock size lies between the carrying capacity and the maximum sustainable yield (MSY) threshold, and in another model, that biomass has declined approximately 50% since 1950s levels. In the South Atlantic the magnitude of decline appears less than in the North Atlantic, and the stock size appears to lie above MSY. However, for both stocks, uncertainties about demographic parameters and catches, and the uninformative nature of available data, indicate that further analysis is necessary. If in fact historical Shortfin Mako catch is higher than the estimates in this report, the likelihood of the stock being below the biomass at MSY will surely increase (ICCAT 2005). Longfin Makos have not been identified correctly in the past and could be a component of these trends. They are less abundant, less fecund and therefore more vulnerable to fisheries than Shortfin Mako and thus may have been similarly depleted by longline fisheries.
Analysis of longline data from the EEZ of Mexico?s Pacific coast (1986?2001) shows that I. paucus was recorded at a low frequency in the catches (F. Marquez pers. comm.). Similarly, this species is caught in low numbers by longliners in Indonesian waters, and given the high level of exploitation in this area, if Longfin Makos were abundant here, this would likely be reflected in the fisheries catch (W. White pers.comm.). Between 1971?1972 it accounted for about six percent of the total number of sharks caught off the north coast of Cuba (Castro in prep), but was infrequently caught between 1974?1997 by longliners off southern Brazil, with only a few samples taken. Similarly, sampling of Spanish fishing ports showed only 0.1% of makos were I. paucus (Moreno and Morón 1992 reported in Compagno 2001).
For the period of 1989?1994 the US reported catch statistics to FAO ranging from 2?12 t per year, but landings do not accurately reflect the numbers of Longfin Mako that are discarded because of poor markets for the meat (Castro et al. 1999). The meat is of low quality and these animals are often finned and discarded at sea.
Overall, the severity and extent of threats to this species need urgent appraisal because of the extent of current oceanic fishing practices, the rarity and biology of the species, and because the more resilient member of the genus is known to have undergone significant declines.
There is no commercial market for this species in the U.S. The meat is not usually landed in the eastern US because it is of poor quality (Castro in prep.). When taken the species is usually finned and discarded at sea. Longfin Mako fins are not of the highest value (for example if compared with hammerheads, guitarfish, etc), however, they are still of high relative value compared to the carcass, and are known to enter the international fin trade (Clarke et al. in press).
There are currently no conservation measures in place for this species yet these are much needed. Specifically, fishing pressure on this species must be considerably decreased through reduction in fishing effort, catch limits, measures to enhance chances of survival after capture and possibly also through the implementation of large-scale oceanic non-fishing areas. Effective conservation of this species will require international cooperation.
The Longfin Mako is listed as a highly migratory species under the 1995 UN Agreement on the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (UNFSA). The Agreement specifically requires coastal States and fishing States to cooperate and adopt measures to ensure the conservation of these listed species. To date, there is little progress in this regard (see United Nations Convention on the Law of the Sea for further details). Also of relevance is the FAO International Plan of Action for the Conservation and Management of Sharks (IPOA?Sharks) which specifically recommends that Regional Fisheries Organisations (RFO) carry out regular shark population assessments and that member States cooperate on joint and regional shark management plans. This is of particular importance for pelagic sharks such as I. paucus whose stocks are exploited by more than one State on the high seas. Although steps are being taken by some RFOs, such as ICCAT, to collect species-specific data on pelagic sharks, and to ban the practise of shark finning, to date no RFO has limited shark catches or drafted a ?Shark Plan? as suggested in the IPOA-Shark guidelines (R. Cavanagh, pers.comm).
The recent ICCAT shark stock assessment workshop (ICCAT 2005) reported that the current situation on submission of shark statistics indicates that the overall volume of catch reported to ICCAT does not represent the total removals of these sharks and the data are also very limited with respect to the size-, age- and sex- composition of the catch. It is noted that improvements in the ICCAT shark database can only be achieved if the Contracting Parties increase infrastructure investment into monitoring the overall catch composition and disposition of the overall catch of sharks and other by-catch species. Therefore, the workshop group recommended that larger monitoring and research investments directed at sharks in particular, and other by-catch species in general, need to be made by the Parties. Above and beyond this main recommendation, the group identified a number of research activities that could provide for improved advice on the status of these species, if implemented. See ICCAT (2005) for further details. This situation applies to all RFOs and is included here as a standard that needs to apply internationally for fisheries that capture pelagic sharks such as I. paucus.
|Citation:||Reardon, M.B., Gerber, L. & Cavanagh, R.D. 2006. Isurus paucus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 21 April 2014.|