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Gymnura natalensis

(Backwater butterfly ray)

Overview

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Family : Butterfly rays ; Occurs off sandy beaches, muddy estuaries and offshore banks. Found singly or in large groups[1]. Feeds on a variety of fishes , crabs and polychaete worms[1]. Ovoviviparous[2]. Ability to change markings and color to blend into environment[3]. Caught by offshore trawlers [1]. Caught by shore anglers , it is prized for its strong fight when hooked , often released[1].

Common Names

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Click on the language to view common names.

Common Names in Afrikaans:

Rem vinderrog, Rem vlinderrog, Rem-vinderrog, Rem-vlinderrog

Common Names in Chinese:

南非沙粒魟, 南非燕魟

Common Names in Dutch:

Diamantvlinderrog

Common Names in English:

Backwater butterfly ray, Backwater butterflyray, Butterfly ray, Diamond ray, Short tailed Ray, Short-tailed Ray

Common Names in French:

Raia-papillon de Natal, Raie papillon du Natal, Raie-papillon du Natal

Common Names in German:

Schmetterlingsrochen

Common Names in Mandarin Chinese:

南非沙粒魟, 南非燕魟

Common Names in Spanish:

Raya Mariposa, Raya mariposa de Natal

Common Names in Spanish, Castilian:

Raya mariposa de Natal

Description

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Habitat

Typically found in water with a depth of 0 to -5,744 meters (0 to -18,845 feet).[4]

Ecology: Habitat
This species occurs close inshore , especially off sandy beaches as well as on offshore banks down to 75 m (Compagno et al. 1989, Smith 1991). Fennessy (1994) found that the species occurs more frequently in the deeper trawls (33 to 45 m) on the Tugela Bank. He observed no diel pattern for this species. Gymnura natalensis is also found in river estuaries (Wallace 1967, Compagno et al. 1989, Smith 1991) and lagoons (Wallace 1967).

Behaviour
Although normally solitary, large shoals have been spotted, often comprising animals of one sex (van der Elst 1988). Single rays tend to be found on the seabed, whereas shoals are often found in the midwater region (van der Elst 1988). Young (2001) found, between 1981 and 2001, 37 occurrences of three or more diamond rays caught in the same Natal Sharks Board (NSB) net installation in one or two days. The majority was of mixed sex and 19 groups were caught off Durban. Most of these multiple catches took place in October and November.

Seasonality
Gymnura natalensis occurs year round (common in Natal throughout the whole year; Wallace 1967) with a peak abundance in December/January (van der Elst 1988). Fennessy (1994) also found that in trawl catches diamond rays occurred more frequently during summer. This differs from the findings of Young (2001), who examined NSB net captures between 1981 and 2000. She found that catches occurred throughout the year, but peaked in October and November (40.5% of total catch) and declined sharply in December. Despite a slight increase during June and July, catches remained low for the rest of the year. Females outnumbered males during warmer months (December to May), while males were more numerous during the cooler period. However, overall both sexes were more common in catches during the cooler months and this association was significant (Young 2001). The sex ratio of NSB catches between 1981 and 2000 was 1:0.92 (m:f) (Young 2001).

Reproduction and Maturity
Wallace (1967) examined a shoal of 28 male specimens caught in Durban nets October 1964. Animals ranged between 109.7and 131.4 cm DW and appeared to be sexually mature . Gravid females (146.2 and 188.0 cm DW) with 5 to 9 embryos were recorded in Durban Bay during January, February, March, June and August. The largest embryo was 38.2 cm DW/453.6 g. A number of the glandular villi, which clothe the uterine walls of the mother, are always found inserted into the spiracular openings of the embryos, suggesting that some of the uterine ?milk? is absorbed this way (Wallace 1967). Van der Elst (1988) states gestation period is one year. The smallest mature male dissected at the NSB was 96.4 cm DW and the smallest mature female was 166.9 cm DW (NSB, unpubl. data ).

According to the length-age curve of van der Elst (1988), diamond rays are ~24 years old at ~250 cm DW /120 kg . Using the above maturity lengths from Wallace (1967), males mature at approximately two years (~100 cm DW/10 kg) and females at approximately six years (~150 cm DW/25 kg).

Smallest free-swimming specimen: 46.8 cm DW (Wallace 1967); 37 to 39 cm field length (NSB unpubl. data).
Largest embryo: 38.2 cm DW (Wallace 1967).
Maximum reported size: 250 cm DW (Smith 1991).
Largest observed animal: 182 cm DW (Wallace 1967); 250 cm DW, 200 cm field length (dubious!) (NSB, unpubl. data).
South Africa angling record : 89.8 kg (Wallace 1967, van der Elst 1988).

Tagged by NSB between 1996 and 2002: 25 animals, no recaptures to date (NSB, unpubl. data). Tagged by shore anglers between 1984 and 2002: 1,766 animals, 10 recaptures (0.57% recapture rate), which includes washed-up tags . Maximum distance moved: 151 km , maximum time at liberty: 330 days (Bullen et al. 2003).

Diet : flat-fish, sardine, gurnard, mole crabs, worms, crabs and squid (van der Elst 1988, Compagno et al. 1989, Smith 1991, Smale et al. 2001). (Ref. 275892).

List of Habitats:

Taxonomy

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Synonyms

Gymnura natalensisPteroplatea natalensisPteroplatea natalensis Gilchrist & Thompson, 1911 • Pteroplatea natalensis Gilchrist & Thompson • Urogymnus natalensis (Gilchrist & Thompson

Notes

Name Status: Accepted Name .

Last scrutiny: Data last modified by FishBase 19-Oct-2000

See Wallace (1967) and Smith (1991).[5].

Similar Species

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Members of the genus Gymnura

ZipcodeZoo has pages for 13 species and subspecies in this genus:

G. altavela (Spiny Butterfly Ray) · G. australis (Australian Butteryfly Ray) · G. bimaculata (Twin-Spot Butterfly Ray) · G. crebripunctata (Longsnout Butterfly Ray) · G. hirundo (Madeira Butterfly Ray) · G. japonica (Japanese Butterfly Ray) · G. marmorata (California Butterfly Ray) · G. micrura (Smooth Butterfly Ray) · G. natalensis (Backwater Butterfly Ray) · G. poecilura (Long-Tailed Butterfly Ray) · G. tentaculata (Tentacled Butterfly Ray) · G. zonura (Bleeker's Butterfly Ray) · G. poecilura (Madeira Butterfly Ray)

More Info

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Further Reading

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Notes

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Contributors

Data Sources

Accessed through GBIF Data Portal March 01, 2008:

Identifiers

Footnotes

  1. Compagno, L.J.V., D.A. Ebert and M.J. Smale (1989). Guide to the sharks and rays of southern Africa. New Holland (Publ.) Ltd., London. 158 p. [back]
  2. Dulvy, N.K. and J.D. Reynolds (1997). Evolutionary transitions among egg-laying, live-bearing and maternal inputs in sharks and rays. Proc. R. Soc. Lond. B 264:1309-1315. [back]
  3. Compagno, L.J.V. (1986). Dasyatidae. p. 135-142. In M.M. Smith and P.C. Heemstra (eds.) Smiths' sea fishes. Springer-Verlag, Berlin. [back]
  4. Mean = -169.490 meters (-556.070 feet), Standard Deviation = 887.750 based on 73 observations. Ocean depth information for each observation from British Oceanographic Data Centre. [back]
  5. Wintner, S.P. 2006. Gymnura natalensis. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 01 February 2012. [back]
Last Revised: 2014-11-21