Gill plate trade

The gill plate trade is the buying and selling of stingray gill plates for their use in traditional Chinese medicine. The gill plates are harvested from stingrays that are caught intentionally, or caught as bycatch. The plates are sold whole or in a powder form. A single kilogram of the gill plate can be sold for up to US$350, though the price varies by ray species.[1]

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Process

Stingrays are caught by fishing lines or nets. Private fishermen tend to target these ray species due to the high payout from their gill plates. Large fishing operations tend to catch rays as bycatch when fishing for more desirable food fish such as tuna, where they are brought back to shore and sold regardless of the intention to catch these fish. The gill plates are split in two and dried after they are taken from the dead rays.[2] Once dried the plates are sold whole or ground into a powder.

Uses in traditional Chinese medicine

Tonics made from stingray gill plates are used in traditional Chinese medicine,[3][4] but there is no evidence of its effectiveness in any medical treatment.[4][5]

Impacts

On stingray populations

A few biological factors known as K-selected traits make the stingray more susceptible to population decline. These K-selected traits include, but are not limited to, late sexual maturity, long gestation, and low number of offspring.[6][5][4][7] Because the gill plate trade will accept plates from both immature and mature rays, the number of rays that are able to reproduce is decreased by the capture of these animals. The population is slow to recover from these losses due to the K-selected traits and as fishing continues the population of stingrays decreases at a faster rate than it increases.[7]

On other marine species

The gill plate trade effects other marine species in one of two ways. The first is the impact that the fishing has on these other species which inhabit the rays ecosystem is when rays are caught intentionally they are typically caught by longline fishing. Longline fishing involves thousands of baited hooks on one very long fishing line close to the ocean's surface.[8] These hooks draw many species including birds, marine mammals, fish, sharks, and rays. The second impact of stingray fishing and population decline is an ecological effect. The stingrays are keystone predators in coral reef environments, when these species are declined the other reef species are effected through trophic factors, for instance predator populations decrease therefore prey populations increase, and risk effects. Risk effects are the behavioral mannerisms that prey learn to avoid predators, such as where or when to feed without becoming a meal for a predator.[9] Without predators such as stingrays, the behavior of prey species is altered.

Legislation

It is currently illegal to trade manta and mobula ray species without proper documentation that it is sustainable trade due to these species having been added to the CITES list.[10][11] Once a species has been added to the CITES list it is internationally protected in legal trade; however, black market transactions still occur.

References
  1. Wu, Joyce (June 2016). "Shark Fin and Mobulid Ray Gill Plate Trade in Mainland China, Hong Kong and Taiwan" (PDF). Traffic Report – via IUCN.
  2. Stevens, Guy. "Field Identification Guide of the Prebranchial Appendages (Gill Plates) of Mobulid Rays for Law Enforcementand Trade Monitoring Applications" (PDF). Unia. Retrieved 6 August 2017.
  3. "Gill Plate Trade | Manta Trust". www.mantatrust.org. Archived from the original on 2016-10-25. Retrieved 2017-08-05.
  4. "New Protections For World's Largest Population of Giant Manta Rays". National Geographic News. 2016-01-08. Retrieved 2017-08-06.
  5. 1943-, Kuiter, Rudie H. (2014). Fishes of the Maldives : Indian Ocean (2. ed.). Cairns, Australia: Atoll Ed. ISBN 9781876410971. OCLC 919432043.CS1 maint: numeric names: authors list (link)
  6. "K-selected species | biology". Encyclopedia Britannica. Retrieved 2017-08-05.
  7. Croll, Donald A.; Dewar, Heidi; Dulvy, Nicholas K.; Fernando, Daniel; Francis, Malcolm P.; Galván-Magaña, Felipe; Hall, Martin; Heinrichs, Shawn; Marshall, Andrea (2016-06-01). "Vulnerabilities and fisheries impacts: the uncertain future of manta and devil rays" (PDF). Aquatic Conservation: Marine and Freshwater Ecosystems. 26 (3): 562–575. doi:10.1002/aqc.2591. ISSN 1099-0755.
  8. Dayton, Paul K.; Thrush, Simon F.; Agardy, M. Tundi; Hofman, Robert J. (1995-09-01). "Environmental effects of marine fishing". Aquatic Conservation: Marine and Freshwater Ecosystems. 5 (3): 205–232. doi:10.1002/aqc.3270050305. ISSN 1099-0755.
  9. "Predicting ecological consequences of marine top predator declines[Trends in Ecology and Evolution 23 (2008) 202–210]". Trends in Ecology & Evolution. 23 (10): 537. 2008. doi:10.1016/j.tree.2008.08.001.
  10. Fisheries, NOAA. "Sharks and Manta Rays Receive Protection Under CITES :: NOAA Fisheries". www.nmfs.noaa.gov. Retrieved 2017-08-05.
  11. "Appendices | CITES". www.cites.org. Retrieved 2017-08-08.
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