Conservation Through Captive Breeding Programs

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There are only three large scale freshwater stingray breeding programs in the world. Of the three, only one is not dedicated to the pet trade. Dark Rivers Hatchery is the only AZA approved research site for fresh water stingray breeding in the United States. Studies are needed to help conserve  wild populations  of these apex predators. This proposed study would compare  wild breeding rates and captive breeding rates of fresh water stingrays in order to consider, how we can ensure wild populations will not diminish due to over fishing in their natural environment.

Environmental factors, such as food types, water quality and weather patterns, will affect spawning. Data will be  compared from several sources, to note the stomach contents, types of prey available during spawning in the wild. If the types of prey found in the stomachs are given to the captive study subjects, as well as water tables  kept the same,  it will induce captive spawning. If captive stingrays are given larger amounts of food  more often than their spawning cycle will be more frequent  and they will have larger litters per birth cycle than the wild population stingrays.

Introduction | | Fresh water stingrays are found in several of the tributaries and connecting river systems of the Amazon River basin. Due to the remote locations were stingray populations are found, makes it especially hard to conduct conservation studies. Due to this population monitoring and breeding cycle studies of wild populations are limited.

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There are no published studies comparing both wild population breeding and captive breeding, this is due to a limited number of breeding populations kept in a captive state. Methodology This paper will review and compare several written articles about wild stingray populations and successful captive breeding. Data such as stomach contents, water quality of wild populations and successful captive breeding populations will be compared and evaluated. Once all of the article’s are gathered and read each one will be referenced below and evaluated to their usefulness to the proposed research.

Results/ Discussion Charvet-Almeida and Barthem, RB. (2010) There paper is a extremely well that shows what fresh water stingray diets are, by dividing the sexual maturity and gender by type of prey items. Using very well thought out charts and tables it is very easy to collect data needed for the proposed research and is the most current data found by this papers author to date about the diet of fresh water stingrays. Charvet-Almeida and Barthem, RB. 2010) writes, “The stomach contents of 137 examples of Potamotrygon motoro caught in 3 locations (Muana, Afua and Lake Arari) on Marajo Island were analyzed. The values of the Index of Relative Importance (IRI) and its respective percentage (%IRI) were calculated. The level of repletion 1 (? full) was the most representative for both sexes, as well as for immature and mature specimens. Most of the food items found were well-digested. The food items identification indicated the presence of 15 orders, including insects, mollusks, crustaceans, annelids and fish.

Differences in diet were observed among the locations studied when comparing %IRI, crustaceans being the most preferred in Afua, fish in Lake Arari and mollusks in Muana. Silva TB and Uieda VS (2007) research shows that freshwater stingrays seem to specialize in certain types of prey items which as previously thought of as mainly small fish turns out to be incorrect . Silva TB and Uieda VS (2007) writes, ” Stingrays of the Potamotrygonidae family are a singular group of Neotropical ichthyofauna. Although ancient reports exist about the roup, there are still many questions that need to be clarified, such as the biology of the species that occur in the Parana-Paraguay River system. In the present work, the diet of Potamotrygon falkneri and Potamotrygon motoro, captured in the Upper Parana River, downstream from the Engenheiro Souza Dias Hydroelectric Power Station (UHE Jupia), was analyzed. Both species showed a diversified diet, consisting of 14 food items, including Mollusca, Crustacea, Insecta and fish, with the predominance in diversity and abundance of aquatic insects.

Only one individual of each species ingested fish. Potamotrygon motoro consumed mainly Ephemeroptera, while P. falkneri consumed mainly Mollusca, Hemiptera and Trichoptera. The data apparently indicate a more specialized diet for P. motoro, consuming more Ephemeroptera (Baetidae), and a more generalized diet for P. falkneri. The analysis of individuals captured in three microhabitats that differ in function of the substrate type and presence of marginal vegetation, suggests differences in the food items consumed. This data is an excellent source of information for the proposed research project . It gives a in-depth study and show critical data that would be key in the proposed research paper. The authors also state that more research should be concluded about the stingray’s diet. Oldfield’s (2005) articles do not, as the articles’ titles imply, give much direct data about breeding freshwater stingrays other than a discussion of sizes of breeding rays. It focuses instead on successful breeding of saltwater rays at several public aquariums.

Oldfield (2005) writes, ” Saltwater rays are common in, and have reproduced in, zoos and public aquariums. Southern stingrays, Dasyatis Americana, common in tropical and subtropical waters of the western Atlantic, produced 47 litters and a total of 199 pups at the National Aquarium in Baltimore between March 1994 and March 1999″ Since this article is supposed to be about the husbandry and reproduction of Freshwater Stingrays, the author risks confusing the reader about captive breeding of freshwater stingrays by referring to successful breeding data of the salt water stingrays.

The paper was not a significant source of data to help research captive breeding of freshwater stingrays. Charvet-Almeida’s (2005) paper talks about several key factors regarding reproductive cycles of wild populations of freshwater stingrays. The authors also make reference to differences in captive breeding rates over the wild population, Charvet-Almeida (2005) states, ” the results obtained refer to observations of freshwater stingray reproductive biology in natural habitat conditions. Rays kept in captivity might present different characteristics”.

The amount of technical terminology and data is of great use for researchers that have with an interest in the subject. Conclusion After looking at all the referenced data the information give is conclusive to the proposed research by giving copious amounts of data and recent research about feeding habits and wild population breeding , it however does show weakness in the knowledge base of published information about captive breeding. More studies should be concluded based upon theories about the possibilities of large scale captive breeding programs.

Work Cited (1) Charvet-Almeida, P. , M. L. G. DE Araujo, and M. P. De Almeida  and  Barthem, RB. 2010. Diet of the freshwater stingray Potamotrygon motoro (Chondrichthyes: Potamotrygonidae) on Marajo Island (Para, Brazil). Braz. J. Biol. [online]. 2010, vol. 70, n. 1, pp. 155-162 (2) Silva, T. B. & Uieda, V. S. 2007. Preliminary data on the feeding habits of the freshwater stingrays Potamotrygon falkneri e Potamotrygon motoro (Potamotrygonidae) from the Upper Parana River basin, Brazil. Biota Neotrop. 7(1): http://www. biotaneotropica. org. r/v7n1/pt/fullpaper? bn02007012007 (3) Charvet-Almeida, P. , M. L. G. DE Araujo, and M. P. De Almeida. 2005. Reproductive Aspects of Freshwater Stingrays (Chondrichthyes: Patamotrygonidae) in the Brazilian Amazon Basin. J. Northw. Atl. Fish. Sci. , 35: 165-171. doi:10. 2960/J. v35. m502 (4) Oldfield, R. G. 2005. Biology, husbandry, and reproduction of freshwater stingrays I. Tropical Fish Hobbyist. 53(12): 114-116 (5) Oldfield, R. G. 2005. Biology, husbandry, and reproduction of freshwater stingrays II. Tropical Fish Hobbyist. 54(1): 110-112