Dasyatis chrysonota. The IUCN Red List of Threatened Species 2020

Abstract

Red list assessment of Dasyatis chrysonata

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The IUCN Red List of Threatened Species™
ISSN 2307-8235 (online)
IUCN 2020: T161643A124520303
Scope(s): Global
Language: English
Dasyatis chrysonota, Blue Stingray
Assessment by: Pollom, R., Bennett, R., Da Silva, C., Ebert, D.A., Gledhill, K.,
Leslie, R., McCord, M.E. & Winker, H.
View on www.iucnredlist.org
Citation: Pollom, R., Bennett, R., Da Silva, C., Ebert, D.A., Gledhill, K., Leslie, R., McCord, M.E. &
Winker, H. 2020. Dasyatis chrysonota. The IUCN Red List of Threatened Species 2020:
e.T161643A124520303. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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THE IUCN RED LIST OF THREATENED SPECIES™

Taxonomy
Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Myliobatiformes Dasyatidae
Scientific Name:ÊÊDasyatis chrysonota (Smith, 1828)
Synonym(s):
• Trygon chrysonata Smith, 1828
Common Name(s):
• English: Blue Stingray
Taxonomic Source(s):
Fricke, R., Eschmeyer, W.N. and Van der Laan, R. (eds). 2020. Eschmeyer's Catalog of Fishes: genera,
species, references. Updated 02 March 2020. Available at:
http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp.
Taxonomic Notes:
This species has been previously confused with the Marbled Stingray Dasyatis marmorata and the
Common Stingray D. pastinaca, neither of which overlap with the range of the Blue Stingray (Last et al.
2016).
Assessment Information
Red List Category & Criteria: Near Threatened A2bd ver 3.1
Year Published: 2020
Date Assessed: August 1, 2019
Justification:
The Blue Stingray (Dasyatis chrysonota) is a medium-sized (to 75 cm disc width) benthic stingray
endemic to southern Africa in the Southeast Atlantic and Western Indian Oceans from central Angola to
St. Lucia, South Africa. It occurs in shallow inshore waters in summer and moves to deeper waters on
the continental shelf in winter to a depth of 110 m. It has a moderate age-at-maturity of 7 years and
small litters of 1–7 pups. The species is captured by trawl, commercial and recreational line, beach
seine, and gill net fisheries. It is not utilized and although previously persecuted by recreational fishers,
it is now discarded alive by recreational and artisanal fishers, with variable mortality from trawling
likely ranging from 17–70%. Trend analysis of research trawl data in South African commercially fished
areas estimated a population reduction of 62% over the past three generation lengths (31.5 years), with
the highest probability of a 50–79% reduction over the past three generation lengths. Overall, due to an
estimated population reduction over some of its range likely driven by steep declines preceding a
substantial reduction in fishing effort in South Africa, combined with a suspected range shift away from
the trawl grounds due to climate change that likely accounts for some of the estimated reduction,
minimal fishing pressure and refuge elsewhere (with a stable trend in shore-angling nominal catches), it
is suspected that the Blue Stingray has undergone a population reduction of 20–29% over the past
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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three generation lengths (31.5 years) due to levels of exploitation, and it is assessed as Near Threatened
(nearly meeting Vulnerable A2bd).
For further information about this species, see Supplementary Material.
Previously Published Red List Assessments
2009 – Least Concern (LC)
https://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T161643A5471417.en
Geographic Range
Range Description:
The Blue Stingray is a southern African endemic occurring from central Angola to St. Lucia, South Africa
in the Southeast Atlantic and Western Indian Oceans (Cowley 1997, Last et al. 2016).
Country Occurrence:
Native, Extant (resident): Angola; Namibia; South Africa
FAO Marine Fishing Areas:
Native: Indian Ocean - western
Native: Atlantic - southeast
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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Distribution Map
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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Population
There are no estimates of population size for the Blue Stingray. Population trend data of annual density
estimates (kg per nm² area swept) were available from demersal research trawl surveys conducted over
26 years (1991–2016) in commercially fished areas of South Africa during autumn and spring along the
south coast by the Fisheries Branch of the South African Department of Agriculture, Forestry and
Fisheries (DAFF, unpubl. data, 2018). The trend data were analyzed over three generation lengths (31.5
years) using a Bayesian state-space framework (Winker and Sherley 2019). This analysis yields an annual
rate of change, a median change over three generation lengths, and the probability of the most likely
IUCN Red List category percent change over three generations (see the Supplementary Information).
The trend analysis revealed an annual rate of reduction of 3.3% over the trawl grounds, consistent
with an estimated reduction of 62.4% over the past three generation lengths (31.5 years), with the
highest probability (51.4%) of a 50–79% reduction over the past three generation lengths. The
estimated reduction is driven partly by a steep decline in catch rates during the early 1990s when
fishing pressure in South Africa was substantially higher; over the last two decades the population
reduction has been less dramatic. Some reduction is likely a result of a northeast range shift in
abundance away from the trawl grounds from 1941 to 2016 due to climate change (Supplementary
Information Figure 2; Currie et al. 2019). This geographic range shift is also supported by observed
increased abundance of the Blue Stingray on the South African east coast; research trawls found this
species was absent from the east coast during the 1920s–1930s and then it became fairly common and
increased in abundance from the 1980s onwards (S. Fennessy, Oceanographic Research Institute,
unpubl. data 2018). Further to the above trend data, monitoring of retained catches in KwaZulu-Natal
recreational shore-angling from 1977 to 2012 indicated nominal catches of the Blue Stingray were stable
over that period (S. Fennessy, Oceanographic Research Institute, unpubl. data 2018). Some catch data
are from angling competitions that target aggregations (S. Fennessy, Oceanographic Research Institute,
unpubl. data, 2018) and without concurrent effort data there is some uncertainty whether the nominal
catch stability represents an actual stable population.
Overall, due to an estimated population reduction over some of its range, likely driven by steep declines
preceding a substantial reduction in fishing effort in South Africa combined with a suspected range shift
away from the trawl grounds due to climate change that likely accounts for some of the estimated
reduction, minimal fishing pressure elsewhere (with a stable trend in shore-angling nominal catches), it
is suspected that the Blue Stingray has undergone a population reduction of 20–29% over the past three
generation lengths (31.5 years) due to levels of exploitation.
For further information about this species, see Supplementary Material.
Current Population Trend:ÊÊDecreasing
Habitat and Ecology (see Appendix for additional information)
The Blue Stingray is benthic in inshore shallow bays, estuaries, and sheltered sandy beaches in summer,
and moves offshore to mid-continental shelf waters in winter to a depth of 110 m (Cowley 1990, Bianchi
et al. 1999, Last et al. 2016). It reaches a maximum size of 75 cm disc width (DW); males mature at ~41
cm DW and females mature at 50 cm DW (Last et al. 2016). Reproduction is lecithotrophic viviparous
with litter sizes of 1–7 pups, a gestation period of ~9 months, and size-at-birth of 17 cm DW (Cowley
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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1990, Ebert and Cowley 2009). Female age-at-maturity is 7 years and maximum age is 14 years;
generation length is therefore 10.5 years (Cowley 1997).
Systems:ÊÊMarine
Use and Trade (see Appendix for additional information)
The Blue Stingray has not been recorded in trade, and is not known to be utilized.
Threats (see Appendix for additional information)
The Blue Stingray is captured by trawl, commercial and recreational line, beach seine, and gill net
fisheries (da Silva et al. 2015). The trawl fisheries in South Africa have decreased in effort over the last
decade, particularly the trawl fishery off KwaZulu-Natal (S. Fennessy unpubl. data 2018). All fisheries
combined in South Africa have landed less than 1 t annually of Blue Stingray from 2010–2012 (da Silva et
al. 2015). Effort in South African shore line fisheries has decreased as a result of a 2002 South African
ban on all-terrain vehicles on beaches. Parts of Namibia are remote and offer refuge from fishing
pressure (Belhabib et al. 2015). Since 2002, artisanal and recreational fishing pressure in a few parts of
southern Angola has increased while other areas remain unfished (Beckensteiner et al. 2016). The Blue
Stingray is not utilized and although 30 years ago it was persecuted by recreational fishers likely causing
high post-release mortality (D. Ebert unpubl. data 2019), it is now discarded alive by recreational and
artisanal fishers, with mortality from trawling likely variable; at-vessel-mortality for trawled congeneric
stingrays ranges from 17–70% (Ellis et al. 2017). Refuge for this species could be provided by extensive
areas of the Agulhas Bank, South Africa that are untrawlable, and several inshore bays and marine
protected areas along the South African coast that are closed to trawling.
The Blue Stingray has tended to move northeast within South Africa over three decades from
1981–2016, from the wide shelf area of Agulhus Bank to the narrower shelf area to the east (Currie et
al. 2019). This shift is concurrent with a reduction in the probability of encounter in the DAFF research
trawl surveys (Supplementary Information Figure 2). The range shift and reduction in likelihood of
encounter are likely at least partially related to climate change (Rouault et al. 2010, Blamey et al. 2015).
The range shift may represent a loss of habitat to this species.
Conservation Actions (see Appendix for additional information)
There are no species-specific protections or conservation measures in place. It occurs in several
protected areas, including in South Africa: the West Coast National Park, the de Hoop Marine Protected
Area (MPA), iSimangaliso MPA, and the uThukela MPA. Further research is needed on population size
and trend, and life history, and catch rates should be monitored.
Credits
Assessor(s): Pollom, R., Bennett, R., Da Silva, C., Ebert, D.A., Gledhill, K., Leslie, R.,
McCord, M.E. & Winker, H.
Reviewer(s): Dulvy, N.K., Crysler, Z. & Kyne, P.M.
Contributor(s): Fennessy, S., Herman, K., Smale, M.J. & Rigby, C.L.
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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Facilitator(s) and
Compiler(s):
Kyne, P.M., Pollom, R. & Dulvy, N.K.
Authority/Authorities: IUCN SSC Shark Specialist Group (sharks and rays)
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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Bibliography
Beckensteiner, J., Kaplan, D.M., Potts, W.M., Santos, C.V. and O’Farrell, M.R. 2016. Data-limited
population-status evaluation of two coastal fishes in southern Angola using recreational catch length-
frequency data. PLOS ONE 11(2): e0147834.
Belhabib, D., Willemse, N.E. and Pauly, D. 2015. A fishery tale: Namibian fisheries between 1950 and
2010. Working Paper Series. Working Paper #2015-65. Fisheries Centre, University of British Colombia.
Bianchi, G., Carpenter, K.E., Roux, J.-P., Molloy, F.J., Boyer, D. and Boyer, H.J. 1999. Field guide to the
living marine resources of Namibia. FAO, Rome, Italy.
Blamey, L.K., Shannon, L.J., Bolton, J.J., Crawford, R.J., Dufois, F., Evers-King, H., Griffiths, C.L., Hutchings,
L., Jarre, A., Rouault, M. and Watermeyer, K.E. 2015. Ecosystem change in the southern Benguela and
the underlying processes. Journal of Marine Systems 144: 9-29.
Cowley, P.D. 1990. The taxonomy and life history of the blue stingray Dasyatis marmorata capensis
(Batoidea: Dasyatidae) from southern Africa. Unpublished M.Sc. Thesis. Rhodes University.
Cowley, P.D. 1997. Age and growth of the blue stingray Dasyatis chrysonota chrysonota from the South-
Eastern Cape coast of South Africa. South African Journal of Marine Science 18(1): 31–38.
Currie, J.C., Thorson, J.T., Sink, K.J., Atkinson, L.J., Fairweather, T.P. and Winker, H. 2019. A novel
approach to assess distribution trends from fisheries survey data. Fisheries Research 214: 98–109.
da Silva, C., Booth, A.J., Dudley, S.F.J., Kerwath, S.E., Lamberth, S.J., Leslie, R.W., McCord, M.E., Sauer,
W.H.H. and Zweig, T. 2015. The current status and management of South Africa's chondrichthyan
fisheries. African Journal of Marine Science 37(2): 233-248.
Ebert, D.A. and Cowley, P.D. 2009. Reproduction and embryonic development of the blue stingray,
Dasyatis chrysonota, in southern African waters. Journal of the Marine Biological Association of the
United Kingdom 89(4): 809–815.
Ellis, J.R., McCully Philips, S.R. and Poisson, F. 2017. A review of capture and post‐release mortality of
elasmobranchs. Journal of Fish Biology 90(3): 653–722.
IUCN. 2020. The IUCN Red List of Threatened Species. Version 2020-2. Available at: www.iucnredlist.org.
(Accessed: 13 June 2020).
Last, P., White, W., de Carvalho, M., Séret, B., Stehmann, M. and Naylor, G. 2016. Rays of the World.
CSIRO Publishing, Clayton.
Rouault, M., Pohl, B. and Penven, P. 2010. Coastal oceanic climate change and variability from 1982 to
2009 around South Africa. African Journal of Marine Science 32: 237–246.
Winker, H, Pacoureau, N. and Sherley, R.B. 2020. JARA: 'Just Another Red List Assessment'. BioRᵴiv
Preprint: http://dx.doi.org/10.1101/672899.
Citation
Pollom, R., Bennett, R., Da Silva, C., Ebert, D.A., Gledhill, K., Leslie, R., McCord, M.E. & Winker, H. 2020.
Dasyatis chrysonota. The IUCN Red List of Threatened Species 2020: e.T161643A124520303.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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Disclaimer
To make use of this information, please check the Terms of Use.
External Resources
For Supplementary Material, and for Images and External Links to Additional Information, please see the
Red List website.
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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Appendix
Habitats
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Habitat Season Suitability Major
Importance?
9. Marine Neritic -> 9.4. Marine Neritic - Subtidal Sandy Resident Suitable Yes
9. Marine Neritic -> 9.5. Marine Neritic - Subtidal Sandy-Mud Resident Suitable Yes
9. Marine Neritic -> 9.6. Marine Neritic - Subtidal Muddy Resident Suitable Yes
9. Marine Neritic -> 9.10. Marine Neritic - Estuaries Resident Suitable Yes
Threats
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Threat Timing Scope Severity Impact Score
5. Biological resource use -> 5.4. Fishing & harvesting
aquatic resources -> 5.4.3. Unintentional effects:
(subsistence/small scale) [harvest]
Ongoing Majority (50-
90%)
No decline Low impact: 5
Stresses: 2. Species Stresses -> 2.1. Species mortality
5. Biological resource use -> 5.4. Fishing & harvesting
aquatic resources -> 5.4.4. Unintentional effects:
(large scale) [harvest]
Ongoing Majority (50-
90%)
Slow, significant
declines
Medium
impact: 6
Stresses: 2. Species Stresses -> 2.1. Species mortality
Conservation Actions in Place
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Conservation Action in Place
In-place research and monitoring
Action Recovery Plan: No
Systematic monitoring scheme: No
In-place land/water protection
Conservation sites identified: No
Area based regional management plan: No
Occurs in at least one protected area: Yes
Invasive species control or prevention: Not Applicable
In-place species management
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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Conservation Action in Place
Harvest management plan: No
Successfully reintroduced or introduced benignly: No
Subject to ex-situ conservation: No
In-place education
Subject to recent education and awareness programmes: No
Included in international legislation: No
Subject to any international management / trade controls: No
Conservation Actions Needed
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Conservation Action Needed
1. Land/water protection -> 1.1. Site/area protection
3. Species management -> 3.1. Species management -> 3.1.1. Harvest management
3. Species management -> 3.1. Species management -> 3.1.2. Trade management
Research Needed
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Research Needed
1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.3. Life history & ecology
1. Research -> 1.4. Harvest, use & livelihoods
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.2. Harvest level trends
Additional Data Fields
Distribution
Lower depth limit (m): 110
Upper depth limit (m): 0
Habitats and Ecology
Generation Length (years): 10.5
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
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The IUCN Red List of Threatened Species™
ISSN 2307-8235 (online)
IUCN 2020: T161643A124520303
Scope(s): Global
Language: English
The IUCN Red List Partnership
The IUCN Red List of Threatened Species™ is produced and managed by the IUCN Global Species
Programme, the IUCN Species Survival Commission (SSC) and The IUCN Red List Partnership.
The IUCN Red List Partners are: Arizona State University; BirdLife International; Botanic Gardens
Conservation International; Conservation International; NatureServe; Royal Botanic Gardens, Kew;
Sapienza University of Rome; Texas A&M University; and Zoological Society of London.
THE IUCN RED LIST OF THREATENED SPECIES™
© The IUCN Red List of Threatened Species: Dasyatis chrysonota – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161643A124520303.en
11