Dasyatis leylandi

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	CHONDRICHTHYES	RAJIFORMES	DASYATIDAE

Scientific Name:

Dasyatis leylandi

Species Authority:

Last, 1987

Common Name/s:

English

–

Brown-reticulate Stingray, Painted Maskray

Synonym/s:

Amphotistius sp. 2

Assessment Information [top]

Red List Category & Criteria:	Near Threatened ver 3.1
Year Assessed:	2006
Assessor/s	Barratt, P.J., Last, P.R. & Kyne, P.M.
Evaluator/s:	Fowler, S.L. & Cavanagh, R.D. (Shark Red List Authority)
Justification: This small coastal stingray has a fairly wide distribution across northern Australia and southern New Guinea; however most of its range is fished, heavily in some areas (e.g., presently Gulf of Carpentaria and Arafura Sea, and historically Northwest Shelf), which will have likely caused some population depletion. Although not targeted by any Australian fisheries, it is currently taken as bycatch and discarded; if retained in the future this may become an issue. Survivorship when discarded is generally unknown, and probably dependent on the method of capture but this stingray does not appear to be robust in heavy trawl gear where it is often crushed. Fishing pressure in the Arafura Sea, including the range of D. leylandi, from vessels operating out of Indonesia is high. On the east coast of Australia, Green Zones in the Great Barrier Reef Marine Park provide some refuge for the species. Although common in parts of its range with some refuge areas, given the heavy fishing pressure and relatively high abundance in trawl bycatch in some areas (which may include pupping grounds), its susceptibility to capture and low fecundity (1 to 2 embryos), and in the absence of any detailed information, this species is assessed on a precautionary basis as Near Threatened (with a proviso that the population is homogenous). If the east and west forms are shown to be different then this assessment will need to be reviewed due to differing pressure in the east and the west and more protected areas in the east. The two populations are considered to be geographically distinct, with no opportunity for exchange between the populations east and west of Torres Strait. Re-evaluation will be required when more information is available on the population structure of this species.

Geographic Range [top]

Range Description:	The geographic range of the two forms (east and west) needs better evaluation. Failure to capture D. leylandi in the northern range of the East Coast Trawl Fishery suggests that the range may be restricted somehow, possibly by habitat type (P. Kyne pers. obs). This may create a natural barrier to migration and intermixing between the east coast and Gulf of Carpentaria/western populations, resulting in two distinct populations (P. Last pers. obs.).
Countries:	Native: Australia (Northern Territory, Queensland, Western Australia); Indonesia; Papua New Guinea
FAO Marine Fishing Areas:	Native: Indian Ocean – eastern; Pacific – western central

Population [top]

Population:	Highly abundant species within some parts of its distribution; commonly caught as trawl bycatch within its range. Species can form large aggregations (not schools, but aggregations). Common on Queensland scallop trawling grounds between Yeppoon and Hervey Bay (Kyne et al. 2005), but not commonly encountered on prawn trawl grounds north of Cairns (P. Kyne pers. obs). Populations east and west of Torres Straight are considered to be geographically distinct. It is difficult to determine population trends as D. leylandi, D. kuhlii and D. annotata were previously all considered to be variations of D. kuhlii.
Population Trend:	Unknown

Population:

Highly abundant species within some parts of its distribution; commonly caught as trawl bycatch within its range. Species can form large aggregations (not schools, but aggregations). Common on Queensland scallop trawling grounds between Yeppoon and Hervey Bay (Kyne et al. 2005), but not commonly encountered on prawn trawl grounds north of Cairns (P. Kyne pers. obs). Populations east and west of Torres Straight are considered to be geographically distinct.

It is difficult to determine population trends as D. leylandi, D. kuhlii and D. annotata were previously all considered to be variations of D. kuhlii.

Population Trend:

Unknown

Habitat and Ecology [top]

Habitat and Ecology:	Unless otherwise referenced, information below drawn from Barratt (2003). A small stingray found in coastal waters. Specimens have been recorded in shallow waters (<5m) on the east and west coasts, and up to 75 m on the west coast (Last and Stevens 1994, W. White pers. comm.). Specimens from the East Coast Trawl Fishery (ECTF) were captured in depths 18 to 53.5 m, and in depths 13.4 to 52.8 m from the Northern Prawn Fishery (NPF). Little is known of its biology and habits. Data on reproductive biology is limited, particularly for reproductive periodicity and seasonality, and gestation period. Its reproductive strategy is aplacental yolksac viviparity with trophonemata. Fecundity is 1 to 2 embryos, which is low, even for dasyatids. The range of maximum ovum diameters and presence of neonates and near neonates throughout a number of months of the year for the Gulf of Carpentaria population suggests that the females of this population do not display a seasonal reproductive cycle. Reproduction may be asynchronous, in the Gulf of Carpentaria population at least, with breeding, gestation and parturition occurring throughout the year. It is not known whether this species has restricted pupping grounds, however pups were caught as bycatch at assumed birth size, suggesting that pupping may occur within the areas of the ECTF and NPF. Assumed birth size is 11 cm DW (Last and Stevens 1994). Juveniles of 11 cm DW were recorded for the east coast population, while juveniles measuring 11, 10 and 9 cm DW were recorded for Gulf of Carpentaria population, however these may have been aborted. Size at maturity has been given as 18cm DW for females and 18.5 cm DW for males (Stobutzki et al. 2002). A study of two populations found that maturity of females occurs between 16.5 to 18.2 cm DW for the Gulf of Carpentaria population and 18.5 cm DW for the east coast population; maturity of males occurs at between 16.7 to 17.7 cm DW for the Gulf of Carpentaria population and 18.0 cm DW for the east coast population. Earlier maturation in the Gulf population may be a result of higher temperatures promoting higher productivity. Calculation of 50% maturity may provide a more reliable estimate of maturity. Age at maturity (years) has not been validated, but the number of bands counted on vertebral samples supports earlier maturation of animals in the Gulf of Carpentaria compared with the east coast populations. Females of the east coast population form 3 to 4 bands by maturity, compared with only 1 to 2 bands for the Gulf of Carpentaria population, and males of the east coast and Gulf of Carpentaria populations form 2 to 3 bands by maturity. Longevity (years) has not been validated, but a maximum of 12 and 9 bands were recorded for females, and 7 and 6 bands recorded for males, of the east coast and Gulf of Carpentaria populations, respectively. Size sexual dimorphism is present in this species, with females generally being larger at maturity and reaching a larger maximal size than males. Maximum size of females was recorded as 31.7 cm DW and 28.1 cm DW from the east coast and Gulf of Carpentaria populations, respectively; maximum size for males was 26.7 cm DW and 24.7 cm DW from the east coast and Gulf of Carpentaria populations, respectively. Female to male sex ratio was found to be higher for both east coast (1.18:1) and Gulf of Carpentaria (1.31:1) populations. D. leylandi is a demersal feeder, eating predominantly crustaceans, and some annelids, teleosts and molluscs. Life history parameters Age at maturity (years): Female: Unknown. Age has not been validated, but females of the east coast population form 3 to 4 bands by maturity, compared with only 1 to 2 bands for the Gulf of Carpentaria population. Male: Unknown. Age has not been validated, but males of the east coast and Gulf of Carpentaria populations form 2 to 3 bands by maturity. Size at maturity (disc width): Female: 18 cm DW (Stobutzki et al. 2002). 16.5 to 18.2 cm DW Gulf of Carpentaria population; 18.5 cm DW east coast population. Male: 18.5 cm DW (Stobutzki et al. 2002). 16.7 to 17.7 cm DW Gulf of Carpentaria population; 18.0 cm DW east coast population. Longevity (years): Unknown. Age has not been validated, but a maximum of 12 and 9 bands were recorded for females, and 7 and 6 bands recorded for males, of the east coast and Gulf of Carpentaria populations, respectively. Maximum size (disc width): Females: 31.7 cm DW (east coast population); 28.1 cm DW (Gulf of Carpentaria). Males: 26.7 cm DW (east coast population); 24.7 cm DW (Gulf of Carpentaria population). Size at birth: 11 cm DW (Last and Stevens 1994). 11 cm DW east coast; juveniles of 9.1 and 10 cm DW were recorded for Gulf of Carpentaria population, though these may have been aborted. Average reproductive age (years): Unknown. Gestation time (months): Unknown. Reproductive periodicity: Unknown. Range of maximum ovum diameters and the presence of neonates and near neonates in females from the Gulf of Carpentaria population for a number of months throughout the year suggests that this population at least do not display a seasonal reproductive cycle. Average annual fecundity or litter size: 1 to 2 (Stobutzki et al. 2002). Annual rate of population increase: Unknown. Natural mortality: Unknown.
Systems:	Marine

Habitat and Ecology:

Unless otherwise referenced, information below drawn from Barratt (2003).

A small stingray found in coastal waters. Specimens have been recorded in shallow waters (<5m) on the east and west coasts, and up to 75 m on the west coast (Last and Stevens 1994, W. White pers. comm.). Specimens from the East Coast Trawl Fishery (ECTF) were captured in depths 18 to 53.5 m, and in depths 13.4 to 52.8 m from the Northern Prawn Fishery (NPF). Little is known of its biology and habits.

Data on reproductive biology is limited, particularly for reproductive periodicity and seasonality, and gestation period. Its reproductive strategy is aplacental yolksac viviparity with trophonemata. Fecundity is 1 to 2 embryos, which is low, even for dasyatids. The range of maximum ovum diameters and presence of neonates and near neonates throughout a number of months of the year for the Gulf of Carpentaria population suggests that the females of this population do not display a seasonal reproductive cycle. Reproduction may be asynchronous, in the Gulf of Carpentaria population at least, with breeding, gestation and parturition occurring throughout the year. It is not known whether this species has restricted pupping grounds, however pups were caught as bycatch at assumed birth size, suggesting that pupping may occur within the areas of the ECTF and NPF. Assumed birth size is 11 cm DW (Last and Stevens 1994). Juveniles of 11 cm DW were recorded for the east coast population, while juveniles measuring 11, 10 and 9 cm DW were recorded for Gulf of Carpentaria population, however these may have been aborted.

Size at maturity has been given as 18cm DW for females and 18.5 cm DW for males (Stobutzki et al. 2002). A study of two populations found that maturity of females occurs between 16.5 to 18.2 cm DW for the Gulf of Carpentaria population and 18.5 cm DW for the east coast population; maturity of males occurs at between 16.7 to 17.7 cm DW for the Gulf of Carpentaria population and 18.0 cm DW for the east coast population. Earlier maturation in the Gulf population may be a result of higher temperatures promoting higher productivity. Calculation of 50% maturity may provide a more reliable estimate of maturity.

Age at maturity (years) has not been validated, but the number of bands counted on vertebral samples supports earlier maturation of animals in the Gulf of Carpentaria compared with the east coast populations. Females of the east coast population form 3 to 4 bands by maturity, compared with only 1 to 2 bands for the Gulf of Carpentaria population, and males of the east coast and Gulf of Carpentaria populations form 2 to 3 bands by maturity.

Longevity (years) has not been validated, but a maximum of 12 and 9 bands were recorded for females, and 7 and 6 bands recorded for males, of the east coast and Gulf of Carpentaria populations, respectively.

Size sexual dimorphism is present in this species, with females generally being larger at maturity and reaching a larger maximal size than males. Maximum size of females was recorded as 31.7 cm DW and 28.1 cm DW from the east coast and Gulf of Carpentaria populations, respectively; maximum size for males was 26.7 cm DW and 24.7 cm DW from the east coast and Gulf of Carpentaria populations, respectively. Female to male sex ratio was found to be higher for both east coast (1.18:1) and Gulf of Carpentaria (1.31:1) populations.

D. leylandi is a demersal feeder, eating predominantly crustaceans, and some annelids, teleosts and molluscs.

Life history parameters
Age at maturity (years): Female: Unknown. Age has not been validated, but females of the east coast population form 3 to 4 bands by maturity, compared with only 1 to 2 bands for the Gulf of Carpentaria population. Male: Unknown. Age has not been validated, but males of the east coast and Gulf of Carpentaria populations form 2 to 3 bands by maturity.
Size at maturity (disc width): Female: 18 cm DW (Stobutzki et al. 2002). 16.5 to 18.2 cm DW Gulf of Carpentaria population; 18.5 cm DW east coast population. Male: 18.5 cm DW (Stobutzki et al. 2002). 16.7 to 17.7 cm DW Gulf of Carpentaria population; 18.0 cm DW east coast population.
Longevity (years): Unknown. Age has not been validated, but a maximum of 12 and 9 bands were recorded for females, and 7 and 6 bands recorded for males, of the east coast and Gulf of Carpentaria populations, respectively.
Maximum size (disc width): Females: 31.7 cm DW (east coast population); 28.1 cm DW (Gulf of Carpentaria). Males: 26.7 cm DW (east coast population); 24.7 cm DW (Gulf of Carpentaria population).
Size at birth: 11 cm DW (Last and Stevens 1994). 11 cm DW east coast; juveniles of 9.1 and 10 cm DW were recorded for Gulf of Carpentaria population, though these may have been aborted.
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown. Range of maximum ovum diameters and the presence of neonates and near neonates in females from the Gulf of Carpentaria population for a number of months throughout the year suggests that this population at least do not display a seasonal reproductive cycle.
Average annual fecundity or litter size: 1 to 2 (Stobutzki et al. 2002).
Annual rate of population increase: Unknown.
Natural mortality: Unknown.

Systems:

Marine

Threats [top]

Major Threat(s):	As with other stingrays D. leylandi is highly susceptible to capture due to its bottom-dwelling nature. It is a common component of trawl bycatch (which is discarded) within its Australian range. Stobutzki et al. (2000) reported that this susceptibility is a threat to the sustainability of a species. Also, the effect of fishing on the macrobenthos, which is the primary habitat of this species, is another concern. There is particularly high pressure on this species in the Gulf of Carpentaria. In the area of the NPF it is caught in about 15% of trawls and accounts for about 4.5% of the total catch (Stobutzki et al. 2002). In the Scallop sector of the QLD ECTF fishery-independent surveys between Yeppoon and Hervey Bay revealed that D. leylandi was the third most common elasmobranch species by number in the bycatch (15.6% of elasmobranch bycatch) (P. Kyne unpublished data). While this represents reasonable pressure, Green Zones in the Great Barrier Reef Marine Park provide partial protection for the east coast population. Dasyatis leylandi is also recorded as irregular bycatch in the Exmouth Gulf Prawn Trawl Fishery, and is presumably caught as bycatch in the Shark Bay/Carnavon area Prawn Trawl Fishery, though data is unavailable. Indonesian fisheries operate to the PNG border and would certainly be taking this species. There is an increasing effort of Australian operators on the coast off PNG. Large pair trawlers operate out of Merauke, West Papua. This fishery consists of some 650 vessels and pressure is intense where the vessels operate in the Arafura Sea. These vessels also operate illegally into northern Australian waters. The effect of historical trawl pressure from foreign fleets operating from 1959 to 1991 on the Northwest Shelf upon this species is unknown. Trawl effort was high at times during that period and is known to have caused a shift in community structure (Sainsbury et al. 1992). Survivorship is generally unknown, and probably dependent on the method of capture. Stobutzki et al. (2002) reports that 27% of females and 95% of males (57% total) captured in the NPF died within the trawl net. This species does not appear to be robust in heavy trawl gear with scallop catch, where it is often crushed, resulting in reasonable mortality (P. Kyne unpublished data).

Major Threat(s):

As with other stingrays D. leylandi is highly susceptible to capture due to its bottom-dwelling nature. It is a common component of trawl bycatch (which is discarded) within its Australian range. Stobutzki et al. (2000) reported that this susceptibility is a threat to the sustainability of a species. Also, the effect of fishing on the macrobenthos, which is the primary habitat of this species, is another concern.

There is particularly high pressure on this species in the Gulf of Carpentaria. In the area of the NPF it is caught in about 15% of trawls and accounts for about 4.5% of the total catch (Stobutzki et al. 2002). In the Scallop sector of the QLD ECTF fishery-independent surveys between Yeppoon and Hervey Bay revealed that D. leylandi was the third most common elasmobranch species by number in the bycatch (15.6% of elasmobranch bycatch) (P. Kyne unpublished data). While this represents reasonable pressure, Green Zones in the Great Barrier Reef Marine Park provide partial protection for the east coast population. Dasyatis leylandi is also recorded as irregular bycatch in the Exmouth Gulf Prawn Trawl Fishery, and is presumably caught as bycatch in the Shark Bay/Carnavon area Prawn Trawl Fishery, though data is unavailable.

Indonesian fisheries operate to the PNG border and would certainly be taking this species. There is an increasing effort of Australian operators on the coast off PNG. Large pair trawlers operate out of Merauke, West Papua. This fishery consists of some 650 vessels and pressure is intense where the vessels operate in the Arafura Sea. These vessels also operate illegally into northern Australian waters.

The effect of historical trawl pressure from foreign fleets operating from 1959 to 1991 on the Northwest Shelf upon this species is unknown. Trawl effort was high at times during that period and is known to have caused a shift in community structure (Sainsbury et al. 1992).

Survivorship is generally unknown, and probably dependent on the method of capture. Stobutzki et al. (2002) reports that 27% of females and 95% of males (57% total) captured in the NPF died within the trawl net. This species does not appear to be robust in heavy trawl gear with scallop catch, where it is often crushed, resulting in reasonable mortality (P. Kyne unpublished data).

Conservation Actions [top]

Conservation Actions:	There is a need to define forms and stocks of this species and monitor changes in pressure on these (particularly if there is an increased fishing effort etc). Green Zones in the Great Barrier Reef Marine Park in Australia provide some refuge for the species. No take zones need to be implemented on Northwest Shelf, which would benefit this and other species. Dasyatis leylandi could be a potential indicator of fish down (common enough to begin with; acts as a surrogate species for other elasmobranchs which are less common). A shift from discarding to retention through increased landings (as the market for ray products increases) could alter the present situation and would need monitoring. Mandatory use of Turtle Exclusion Devices and Bycatch Reduction Devices in the Queensland ECTF and NPF have had little impact on reducing catches because of the small size of the species (P. Kyne unpublished data). Further investigation is needed into the life history traits of this species, particularly reproductive biology, as well as the extent of population differences. These differences may have ramifications for management, especially for areas subject to heavy fishing pressure such as the Gulf of Carpentaria and the Queensland east coast.

Conservation Actions:

There is a need to define forms and stocks of this species and monitor changes in pressure on these (particularly if there is an increased fishing effort etc).

Green Zones in the Great Barrier Reef Marine Park in Australia provide some refuge for the species. No take zones need to be implemented on Northwest Shelf, which would benefit this and other species.

Dasyatis leylandi could be a potential indicator of fish down (common enough to begin with; acts as a surrogate species for other elasmobranchs which are less common). A shift from discarding to retention through increased landings (as the market for ray products increases) could alter the present situation and would need monitoring.

Mandatory use of Turtle Exclusion Devices and Bycatch Reduction Devices in the Queensland ECTF and NPF have had little impact on reducing catches because of the small size of the species (P. Kyne unpublished data).

Further investigation is needed into the life history traits of this species, particularly reproductive biology, as well as the extent of population differences. These differences may have ramifications for management, especially for areas subject to heavy fishing pressure such as the Gulf of Carpentaria and the Queensland east coast.

Citation:	Barratt, P.J., Last, P.R. & Kyne, P.M. 2006. Dasyatis leylandi. In: IUCN 2008. 2008 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 04 December 2008.
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