|Scientific Name:||Sphyrna tudes (Valenciennes, 1822)|
|Taxonomic Notes:||The historical confusion that surrounds this species' taxonomy is pending resolution and nomenclatural stability. The current lectotype of this species (MNHN 1049 from Nice, France) most likely represents S. couardi, and the paralectotype (MNHN 1019 from Cayenne, French Guiana) most likely represents S. bigelowi. The retention of the name S. tudes would require the rejection of the current lectotype and redesignation of the Cayenne specimen as the lectotype. Compagno (in preparation b) outlines the history and problems associated with this issue.|
|Red List Category & Criteria:||Vulnerable A2ad+3d+4ad ver 3.1|
|Assessor(s):||Mycock, S.G., Lessa, R. & Almeida, Z.|
|Reviewer(s):||Kyne, P.M., Cavanagh, R.D., Fowler, S.L., Heupel, M.R. & Simpfendorfer, C.A. (Shark Red List Authority)|
With a confused taxonomic history Sphyrna tudes has likely been misreported from several localities, and its true range appears restricted to the Western Central and Southwest Atlantic from Venezuela to Uruguay. Records from the Mediterranean are probably incorrect. The adults' preference for inshore habitats at depths of 9 to 40 m and the juveniles' use of shallow coastal nursery areas predisposes this species to capture in inshore multi-species artisanal gillnet fisheries. It is taken as bycatch in such fisheries throughout its range with all size classes and reproductive stages susceptible to capture. This species has a one-year reproductive cycle with litters of 5 to 19 pups. Marked declines have been reported anecdotally in catches of this species off Trinidad and declines are now apparent off northern Brazil. Given its inshore coastal habitat, limited reproductive capacity, susceptibility to capture and heavy (and increasing) gillnet fishing pressure throughout its range, S. tudes is assessed as Vulnerable. Quantitative evaluation of gillnet catches across its range is a priority and protected areas should be established.
|Range Description:||Original records from the Mediterranean by Valenciennes (1822) may be incorrect and may be based on Sphyrna couardi (Cadenat and Blache 1981, Compagno in prep. b). |
Observations that the species has been recorded off the western Florida, USA, Mexico and Panama require verification (records off Mississippi, USA probably incorrect; Compagno in prep. b).
Key inshore muddy beach habitats along the north east coast of South America, Trinidad and Tobago and Northern Brazilian Coast to the State of Maranhão, are identified as pupping and nursery grounds for this species and adults are known from the continental shelf over its range from the southern Gulf of Mexico to Uruguay.
Native:Brazil; French Guiana; Guyana; Suriname; Trinidad and Tobago; Uruguay; Venezuela, Bolivarian Republic of
|FAO Marine Fishing Areas:|
Atlantic – western central; Atlantic – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Sphyrna tudes is a small, inshore hammerhead shark. Newborn and juveniles occupy inshore muddy beach nursery areas, and adults to a maximum size of 150 cm TL are found in depths of 5 to 40 m over muddy substrates. |
Geographic variation in maturity and aspects of reproductive biology are apparent:
Off Trinidad, males mature at ~80 cm TL; females at ~98 cm TL and are reported to ovulate and mate during August. Following a ten month gestation the young are born in shallow water from late May to June. Size at birth is ~30 cm TL. The annual reproductive cycle of this species results from gestation running concurrently with the ovarian cycle, and females are fertilized soon after parturition. Litter size 5 to 12 pups (Castro 1989).
Off northern Brazil (Maranhão state) the smallest pregnant female observed was 101 cm TL, however, the estimated size at 50% maturity for females was 114 cm TL. The estimated size of first maturity for males in northern Brazil was 92.1 cm TL, considerably higher than off Trinidad. Pregnant females are observed from June to October and also from January to April. The highest gonadal indices where observed in males from May to November and in March. Uterine eggs and embryos measuring 34 mm TL were observed in June. Embryos measuring 90, 150, 190 and 237 mm TL were observed in January. The number of embryos in females 101 to 132 cm TL ranged between 5-19. There is a strong relationship between the fecundity and the size of females (Lessa et al. 1998).
The characteristic golden colour of live specimens results from a pigment present in their penaeid shrimp and ariid catfish diet.
In experimental fisheries using gillnets with different meshes (1990/91/92) the species was the second most important in shallow waters off northern Brazil (Maranhao State), yielding a maximal CPUE in May of 20 kg/km/hr. In other periods of the year the CPUE was below 5 kg/km/hr. Using 20-25 cm mesh size gillnets, the species represented 25% of the total catch in 1991 and 15% in 1992 (Stride et al. 1992).
Multi-species gillnet fisheries over this species' range are reported to catch individuals of all sizes from newborns to adults. In Brazil, the species is reported to be of interest only to artisanal fisheries. A marked decline in such artisanal catches around Trinidad reported anecdotally between observations in 1985-86 and 1995-96 suggests the population has been impacted significantly in that region (Castro and Woodley 1998, Castro et al. 1999). The same decreasing trend in catches has been observed in recent years in northern Brazil (Almeida, unpublished data). Inshore coastal fishing is intense (and increasing in many areas) across this species' range and there is every reason to suspect that declines have occurred across its entire distribution.
None currently in place.
It is recommended that collection of quantitative artisanal catch data on this little known species is initiated. This should be combined with an investigation into the commercial value and utilization of its flesh and fins to enable a strategy for protection and management to be developed. Protection of shallow inshore habitat is certainly necessary for this and many other marine species.
|Citation:||Mycock, S.G., Lessa, R. & Almeida, Z. 2006. Sphyrna tudes. The IUCN Red List of Threatened Species 2006: e.T60202A12318061.Downloaded on 24 October 2017.|
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