http://rds.yahoo.com/_ylt=A0geu91IG...ess/2004/Elasmo/9Ara%C3%BAjoConservationl.DOC
It's a word document too big to paste here, but definitely worth looking at.
It's a word document too big to paste here, but definitely worth looking at.
Great paper on stingray exports from Brazil
- Thread starter ewurm
- Start date
Good read.
Personally I would like to see the worlds supply of hobbiest rays come frm captive breeding. That is just me.
Respectfully,
FireMedic.
Personally I would like to see the worlds supply of hobbiest rays come frm captive breeding. That is just me.
Respectfully,
FireMedic.
link doesnt work for me..
Is it the article by Patricia Charvet-Almeida?
http://209.85.173.132/search?q=cach...ida&hl=en&ct=clnk&cd=5&gl=us&client=firefox-a
Is it the article by Patricia Charvet-Almeida?
http://209.85.173.132/search?q=cach...ida&hl=en&ct=clnk&cd=5&gl=us&client=firefox-a
When Yahoo says it isn't authorized, click the link anyway
Page bomb
Abstract
Potamotrygonids are Elasmobranchs that share some features with marine forms: low fecundity, late maturation and slow growth. Besides this, constrains of freshwater environment become potamotrygonids species more vulnerable to fisheries than the marine counterparts. Potamotrygonidae are fisheries to ornamental purpose for more than two decades at Brazilian Amazon. Artisanal fisheries for food purposed also capture potamotrygonids. Commercial fisheries with trawl net use to catch freshwater stingrays as bycatch. The main problems involving fishery and conservation in this group are species incorrect identification, and lost biological information.
Introduction
South American freshwater stingrays are included in a single Family (Potamotrygonidae) and represent an important part of the Neotropical ichthyofauna. Potamotrygonids belong to the only group of Elasmobranchs completely restricted to freshwater habitats (Brooks et al, 1981; Compagno & Cook, 1995) and are widely distributed in most river systems of tropical and subtropical South America draining to the Atlantic Ocean (Rosa, 1985).
The life history of potamotrygonids exhibits some features similar to the ones found in marine Elasmobranchs, such as: low fecundity, late maturation and slow growth (Camhi et al., 1998). Besides this, constrain to freshwater environments (including habitat reduction during the dry season) makes these stingray species more vulnerable to fishing activities than their marine counterparts. Some freshwater stingrays are endemic and have a restricted range with a relatively low limit of tolerance to both natural and anthropogenic impacts, such as ecotourism, habitat deterioration and loss (Compagno & Cook, 1995; Barcellos, 1996; Araújo, 1998; Charvet-Almeida, 2001, Araújo et al., 2004).
Potamotrygonids have been fished for different purposes for several decades in the Brazilian Amazon region. Only recently, baseline and historic data on species biology and abundance began to be collected. Part of this information is being used as guidelines in the management plan of this fishing activity in Brazil (Araújo et al, 2004). Freshwater stingrays present high polychromatism (Almeida, 2003) that often leads to species misidentification and may cause loss of accurate biological information (Charvet-Almeida et al., 2002). In order to be sustainable, elasmobranch fisheries must take into account the biological capacity of the species, which requires basic taxonomic knowledge (Camhi et al, 1998). In this sense, lots of effort must be put to help solve some of the potamotrygonid species identification problems.
Many species of freshwater stingrays occur in more than one country (Araújo et al, 2004) and probably there are stock differences that require distinct management plans. The lack of adequate management in some regions associated to habitat damage and deterioration may be factors that lead to population declines as has been suggested by Camhi et al. (1998) for sharks species. Considering these aspects, isolated species protection measures and fishery management will not offer sufficient / good support to develop conservation programs for freshwater stingrays, except for a few endemic species. This report provides a brief summary of some fishery aspects and conservation status of potamotrygonid species in the Brazilian Amazon.
Material and Methods
The present study included data from two different areas in the Brazilian Amazon region. Area A is included in the BarcelosMunicipality (0°30’ S, 63°12’ W), located in the Rio NegroBasin and corresponds to the main fishing area of the ornamental fishery industry in the AmazonasState. Area B included two islands (Cotijuba 01o15’30’’ S, 48o33’30’’ W; and Colares 00o55’27’’ S, 048o17’21’’ W) located in the MarajóBay, Amazon estuary, State of Pará, and is known for its high abundance of stingrays species (Figure 1).
Figure 1: Map of the two main study areas where points 1 and 2 correspond to Area B and point 3 to Area A.
In both sites, fishing trips were conducted in collaboration with local fishermen, during the fishing season (Area A) and all year round (Area B). Several specimens of freshwater stingrays were collected, dissected and had biological parameters observed. Environmental variables, such as temperature (°C), dissolved oxygen (mg/l), conductivity (mS), and pH data were also collected at each sample site. During the research trips several fishermen were interviewed to provide complementary information. Capture effort data (CPUE) and post-capture mortality were calculated only for Area A, considering the ornamental fishery (Araújo, 1998). The main fishery characteristics of each area, sampling method to obtain the specimens and basic environmental differences are indicated in Table 1.
Table 1: Fishery, sampling and main environmental characteristics of each studied area.
Results and Discussion
Freshwater stingrays presently are not among the main target species for the ornamental fish industry, nor for the commercial fishery fleet in the Brazilian Amazon region. The species observed in the present study were: Plesiotrygon iwamae, Paratrygon aiereba, Potamotrygon motoro, Potamotrygon orbignyi, Potamotrygon schroederi, Potamotrygon scobina and Potamotrygon cf. histrix (Potamotrygon sp. C or “cururu” freshwater stingray). The different species studied seemed to have distinct specific uses according to each area (Table 2).
[FONT="]
[/FONT] Table 2 - List of species of Potamotrygonidae in evaluation by the current study and their uses as natural resource.
Potamotrygonids have been captured for ornamental purposes for over two decades in the Brazilian Amazon (Araújo, 1998). The exportation of theses species represents less than 1 % of all fishes exported from Amazonas and ParáStates. Nevertheless, these stingrays have a significant role in the ornamental trade since often the exportation of other species takes place only if a few freshwater stingrays are included in the deal. Potamotrygonids also can raise the exports of other traditional species, such as Paracheirodon axelrodi (Araújo et al. 2004). Nowadays freshwater stingray exports are controlled by a Brazilian Environmental Agency federal regulation (IBAMA, number 036/2003), which determines a list of six species of potamotrygonids that are allowed to be exported according to a yearly species-specific quota system. Only recently catch and effort dates of Potamotrygonidae fisheries for the ornamental trade began to be collected.
In AmazonasState, where 10.000 units of stingrays are exported annually, the fishery effort is concentrated on Potamotrygon cf. hystrix stocks (Figure 2).
Figure 2 - Potamotrygon cf. hystrix, commonly known as “arraia cururu” and presently being described (Photo: Maria Lúcia G. Araújo).
This species is one the smallest species of freshwater stingrays, with maximum disc width of 500 mm. It is endemic of the Rio NegroBasin and high densities of individuals are observed in island and flooded forest. Approximately 60% of the captures of this species are concentrated in only one tributary of the Rio Negro. The CPUE data for this species in this area does not exhibit a direct relationship with fishery effort, neither exportation demand. Observations indicated that the effort pressure on the stocks varies according to the level of the river (Table 3).
Table 3 - CPUE data of freshwater stingray captures in area A.
This species vulnerability is associated to habitat accessibility by traditional ornamental fishermen and to opportunistic commercial fishermen fishing for food. The average post-capture mortality of this species ranges between 2 - 5 %. Potamotrygon cf. hystrix represents 31,25 % of all freshwater stingrays legally exported from Brazil Its captures are monitored and the number of individuals exported annually is controlled to avoid stocks depletion.
Potamotrygon motoro (Figure 3) is one of the most fecund stingrays and presents a wide distribution in all Neotropical region. Its captures and exportations are monitored too. There is no evidence of reduction in the abundance in this species, but a strict export control must exist to avoid misidentification of this species with the endemic P. leopoldi and P. henlei. The post-capture mortality is estimated between 10 - 12 %.
Potamotrygon orbignyi (Figure 4) is a well-distributed species in all AmazonBasin. It is a highly polychromatic stingray and sometimes difficult to be recognized, especially due to the existence of some faded color patterns. The evaluation of CPUE for this species did not show reduction in abundance and post-capture mortality ranges from 8 - 10 %.
Potamotrygon schroederi (Figure 5) is a rare stingray with not many exports records. This is due partially because this species has the highest post-capture mortality (10 - 12 %) of all legally exported stingrays. The capture and exportation of this species must also be controlled because it might be irregularly exported as Potamotrygon cf. hystrix.
Artisanal fisheries also capture potamotrygonids as a food source. These captures are restricted to some areas, such as the Amazon estuary (Area B), where longlines are used as the main fishing gear. This stingray fishery is considered of low economic value. Potamotrygonids are not the main target species but are never discarded when caught and are sold at local fish markets. At least three species are caught in this fishery: Plesiotrygon iwamae, Potamotrygon orbignyi and P. scobina (Charvet-Almeida, 2001; Almeida, 2003).
Incidental capture by commercial fisheries with trawl net happen along Solimões-AmazonasRiver, and it has introduced an unknown mortality rate on freshwater stingrays stocks.
The negative image of freshwater stingrays cause the “negative fishery” The effect of disturbance from ecotourism operations has removed at least 21 000 individuals Potamotrygonidae (mainly Potamotrygon orbignyi and Paratrygon aiereba) at Rio Negro Basin This kind of fishery is developed by some ecotourism companies to avoid accidents with freshwater stingrays. It is an unregulated activity because is not considered “fishery” by Brazilian Environmental Agency (IBAMA) (Araújo et al 2004).
Brazil is in South America the only country that has a specific regulation to control the export of freshwater stingrays species to ornamental trade. Two of the three endemic species permitted to be exported Potamotrygon henlei and P. leopoldi are in basins where dam projects are planning to be developed in the next years. The other endemic species Potamotrygon cf hystrix will need soon National protection of its habitat because in this range ecotourism projects and dragging activities of Rio Negro will compromise its abundance Habitat damage or loss, can deplete freshwater stingrays population more severity than fisheries. (Araújo et 2004)
A critic question at ornamental fish trade is mortality post-capture. The values estimated for freshwater stingray depends of the species rusticity, fishermen practice and exportation area facilities.
The causes of mortality can be categorized as high density in the tanks or plastic boxes, oxygen and pH requirements, and skin lesions (inflammatory oedema) around the mouth, the anterior margin of the disc and pelvic fins. Potamotrygon cf hystrix exhibit the smallest mortality rate what justify its high capture rates, the opposite happens with P. schroederi
Many species of freshwater stingrays occur in more than one country, this is the case of P. motoro, P. orbignyi, P schroederi, Paratrygon aiereba and Plesiotrygon iwamae but until now there are no shared stocks. Despite the fact that Brazilian scientist has proposed a National Plan to management the capture of Potamotrygonidae from commercial vessels, and practice of negative fishery, any effective measured has been considering by IBAMA
Conclusions
The importance to ornamental fish industry is having stingray to offer to ornamental trade, cannot be ignored because this activity employs at least 10.000 families in Brazilian Amazon. The lack of adequate identification of some freshwater stingrays species is a problem that must be solve soon, because the population models to Elasmobranch species require a species-specific data on life cycle parameters. A conservation program to freshwater stingrays species to be well succeed must consider not only the regulation of fish activities but the habitat deterioration and loss, as well the development of ecotourism.
[FONT="]
[/FONT] References
Almeida, M. P. 2003 .Pesca, Policromatismo e Aspectos Sistemáticos de Potamotrygon scobina,Garman 1913 (Chondrichthyes: Potamotrygonidae) da Região da Ilha de Colares da IIha de Marajó - Pará. Masters Dissertation. Belém, Museu Paraense Emílio Goeldi & Universidade Federal do Pará. 145 p.
Almeida, M. P.; Charvet-Almeida, P. & Viana, A. S. 2003. Polychromatic and Morphometric Aspects of the Freshwater Stingray Potamotrygon scobina (Chondrichthyes: Potamotrygonidae) in the Marajó Bay Region (Pará, Brazil).
Araújo, M. L. G., 1998. Biologia Reprodutiva e Pesca de Potamotrygon sp. C (Chondrichthyes - Potamotrygonidae), no Médio Rio Negro, Amazonas. Masters Dissertation. Manaus, Instituto Nacional de Pesquisas da Amazônia & Universidade do Amazonas. 171 p
Araújo, M. L. G. 2001. Plano de Monitoramento de Arraias de Água Doce – Technical Report Convênio IBAMA-AM/ACEPOAM. 29 p.
Araújo, M. L. G , Charvet-Almeida, P, Almeida M. P , Pereira, H.. 2004. Freshwater Stingrays (Potamotrygonidae): status, conservation and management challenges. Information document AC 20 info 08:1-6 http://www.cites.org/common/cttee/animals/20/E20-inf-08.pdf
Barcellos, J. F. M. 1996. Amônia, Uréia e o Conteúdo do Oxigênio do Sangue de Potamotrygon sp (Chondrichtyes
otamotrygonidae) da Amazônia. Masters Dissertation. Manaus, Instituto Nacional de Pesquisas da Amazônia & Universidade do Amazonas. 61 p.
Brooks, D. R.; Thorson, T. B. & Mayes, M. A. 1981. Freshwater stingrays (Potamotrygonidae) and their helminth parasites: testing hypotheses of evolution and coevolution. In: Advances in Cladistics. Funk, V. A. & Brooks, D. R. (eds.). Proceedings of the First Meeting of the Willi Hennig Society, New York. p. 147-175.
Camhi, M.; Fowler, S.L.; Musick , J.A. , Bräutigam, A. & Fordham, S.V. 1998. Sharks and their relatives. – Ecology and Conservation. IUCN/SSC Sahrk Specialist Group.IUCN, Gland, Switzerland and Cambridge, UK.iv+39P.
Charvet-Almeida, P. 2001. Ocorrência, Biologia e Uso das Raias de Água Doce na Baía de Marajó (Pará, Brasil), com Ênfase na Biologia de Plesiotrygon iwamae (Chondrichthyes: Potamotrygonidae). Masters Dissertation. Belém, Museu Paraense Emílio Goeldi & Universidade Federal do Pará. 213 p.
Charvet-Almeida, P.; Araújo, M. L. G.; Rosa, R. S. & Rincon, G. 2002. Neotropical freshwater stingrays: diversity and conservation status. IUCN Shark News 14: 1-2.
Compagno, L. J. V. & S. F. Cook. 1995. The exploitation and conservation of freshwater elasmobranchs: status of taxa and prospects for the future. In: The Biology of Freshwater Elasmobranchs. Oetinger, M. I. & Zorzi, G. D. (eds.). Journal of Aquariculture & Aquatic Sciences, 7: 62-90.
IBAMA. 2003. Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis. Portaria N°. 036/2003, de 25 de junho de 2003.
Rosa, R. S. 1985. A Systematic Revision of the South American Freshwater Stingrays (Chondrichthyes: Potamotrygonidae). Doctorate Thesis, Williamsburg, College of William and Mary. 523 p.
Acknowledgements
Page bomb
CONSERVATION STATUS OF FRESHWATER STINGRAYS
(CHONDRICHTHYES: POTAMOTRYGONIDAE)
IN THE BRAZILIAN AMAZON
Maria Lúcia Góes de Araújo
ESA - Universidade Estadual do Amazonas - Rua Carvalho Leal 1777. Cachoeirinha - Manaus - AM, Brazil. 69005-000. Phone fax 55 92 2419702
Patricia Charvet-Almeida
Ph.D. student, Universidade Federal da Paraíba (UFPB), Departamento de Sistemática e Ecologia, CCEN, João Pessoa, PB, Brazil. 58059-900.
Mauricio Pinto de Almeida
Ph.D. student, Museu Paraense Emílio Goeldi (MPEG), Setor de Ictiologia, Coordenação de Zoologia, P.O. Box 399, Belém, PA, Brazil. 66017-970. maupalm@nautilus.com.br
Abstract
Potamotrygonids are Elasmobranchs that share some features with marine forms: low fecundity, late maturation and slow growth. Besides this, constrains of freshwater environment become potamotrygonids species more vulnerable to fisheries than the marine counterparts. Potamotrygonidae are fisheries to ornamental purpose for more than two decades at Brazilian Amazon. Artisanal fisheries for food purposed also capture potamotrygonids. Commercial fisheries with trawl net use to catch freshwater stingrays as bycatch. The main problems involving fishery and conservation in this group are species incorrect identification, and lost biological information.
Introduction
South American freshwater stingrays are included in a single Family (Potamotrygonidae) and represent an important part of the Neotropical ichthyofauna. Potamotrygonids belong to the only group of Elasmobranchs completely restricted to freshwater habitats (Brooks et al, 1981; Compagno & Cook, 1995) and are widely distributed in most river systems of tropical and subtropical South America draining to the Atlantic Ocean (Rosa, 1985).
The life history of potamotrygonids exhibits some features similar to the ones found in marine Elasmobranchs, such as: low fecundity, late maturation and slow growth (Camhi et al., 1998). Besides this, constrain to freshwater environments (including habitat reduction during the dry season) makes these stingray species more vulnerable to fishing activities than their marine counterparts. Some freshwater stingrays are endemic and have a restricted range with a relatively low limit of tolerance to both natural and anthropogenic impacts, such as ecotourism, habitat deterioration and loss (Compagno & Cook, 1995; Barcellos, 1996; Araújo, 1998; Charvet-Almeida, 2001, Araújo et al., 2004).
Potamotrygonids have been fished for different purposes for several decades in the Brazilian Amazon region. Only recently, baseline and historic data on species biology and abundance began to be collected. Part of this information is being used as guidelines in the management plan of this fishing activity in Brazil (Araújo et al, 2004). Freshwater stingrays present high polychromatism (Almeida, 2003) that often leads to species misidentification and may cause loss of accurate biological information (Charvet-Almeida et al., 2002). In order to be sustainable, elasmobranch fisheries must take into account the biological capacity of the species, which requires basic taxonomic knowledge (Camhi et al, 1998). In this sense, lots of effort must be put to help solve some of the potamotrygonid species identification problems.
Many species of freshwater stingrays occur in more than one country (Araújo et al, 2004) and probably there are stock differences that require distinct management plans. The lack of adequate management in some regions associated to habitat damage and deterioration may be factors that lead to population declines as has been suggested by Camhi et al. (1998) for sharks species. Considering these aspects, isolated species protection measures and fishery management will not offer sufficient / good support to develop conservation programs for freshwater stingrays, except for a few endemic species. This report provides a brief summary of some fishery aspects and conservation status of potamotrygonid species in the Brazilian Amazon.
Material and Methods
The present study included data from two different areas in the Brazilian Amazon region. Area A is included in the BarcelosMunicipality (0°30’ S, 63°12’ W), located in the Rio NegroBasin and corresponds to the main fishing area of the ornamental fishery industry in the AmazonasState. Area B included two islands (Cotijuba 01o15’30’’ S, 48o33’30’’ W; and Colares 00o55’27’’ S, 048o17’21’’ W) located in the MarajóBay, Amazon estuary, State of Pará, and is known for its high abundance of stingrays species (Figure 1).
In both sites, fishing trips were conducted in collaboration with local fishermen, during the fishing season (Area A) and all year round (Area B). Several specimens of freshwater stingrays were collected, dissected and had biological parameters observed. Environmental variables, such as temperature (°C), dissolved oxygen (mg/l), conductivity (mS), and pH data were also collected at each sample site. During the research trips several fishermen were interviewed to provide complementary information. Capture effort data (CPUE) and post-capture mortality were calculated only for Area A, considering the ornamental fishery (Araújo, 1998). The main fishery characteristics of each area, sampling method to obtain the specimens and basic environmental differences are indicated in Table 1.
Table 1: Fishery, sampling and main environmental characteristics of each studied area.
Fishery Characteristics
Area A
Area B
Capture methods.
Hook and line, drill net with flashlights and battery, harpoon, night captures only.
Longlines, hook and line, beach seine, bottom trawl net, day and night captures.
Purpose of the captures.
Ornamental and “negative fishery”.
Food source, medicinal and occasionally ornamental.
Months of capture (fishing season).
August - April.
All year round.
Water quality.
Poor black water, acid, warm and low in dissolved oxygen.
White water, warm, slightly acid (pH 5-6), oxygen rich, with seasonal salinity influence.
Bottom substrate.
Sandy and muddy.
Sandy, muddy and rocky.
Duration of each research trip (main season of sampling).
10 days
(August - April)
5 days
(all year round).
Results and Discussion
Freshwater stingrays presently are not among the main target species for the ornamental fish industry, nor for the commercial fishery fleet in the Brazilian Amazon region. The species observed in the present study were: Plesiotrygon iwamae, Paratrygon aiereba, Potamotrygon motoro, Potamotrygon orbignyi, Potamotrygon schroederi, Potamotrygon scobina and Potamotrygon cf. histrix (Potamotrygon sp. C or “cururu” freshwater stingray). The different species studied seemed to have distinct specific uses according to each area (Table 2).
[FONT="]
[/FONT] Table 2 - List of species of Potamotrygonidae in evaluation by the current study and their uses as natural resource.
Species
Type of use
Area
Plesiotrygon iwamae
Food, medicinal and
ornamental purposes.
B
Paratrygon aiereba
Food, ornamental and
medicinal purposes.
A and B
Potamotrygon motoro
Ornamental, food and medicinal purposes
A and B
P. orbignyi
Ornamental, food and medicinal purposes.
A and B
P. schroederi
Ornamental purpose.
Just in A
P. scobina
Food, ornamental and
medicinal purposes.
Just in B
Potamotrygon. cf. hystrix
Ornamental purpose.
Endemic to A
Potamotrygonids have been captured for ornamental purposes for over two decades in the Brazilian Amazon (Araújo, 1998). The exportation of theses species represents less than 1 % of all fishes exported from Amazonas and ParáStates. Nevertheless, these stingrays have a significant role in the ornamental trade since often the exportation of other species takes place only if a few freshwater stingrays are included in the deal. Potamotrygonids also can raise the exports of other traditional species, such as Paracheirodon axelrodi (Araújo et al. 2004). Nowadays freshwater stingray exports are controlled by a Brazilian Environmental Agency federal regulation (IBAMA, number 036/2003), which determines a list of six species of potamotrygonids that are allowed to be exported according to a yearly species-specific quota system. Only recently catch and effort dates of Potamotrygonidae fisheries for the ornamental trade began to be collected.
In AmazonasState, where 10.000 units of stingrays are exported annually, the fishery effort is concentrated on Potamotrygon cf. hystrix stocks (Figure 2).
This species is one the smallest species of freshwater stingrays, with maximum disc width of 500 mm. It is endemic of the Rio NegroBasin and high densities of individuals are observed in island and flooded forest. Approximately 60% of the captures of this species are concentrated in only one tributary of the Rio Negro. The CPUE data for this species in this area does not exhibit a direct relationship with fishery effort, neither exportation demand. Observations indicated that the effort pressure on the stocks varies according to the level of the river (Table 3).
Table 3 - CPUE data of freshwater stingray captures in area A.
Year
Months of low water period
CPUE
1998-1999
2
10,26
1999-2000
4
34,62
2000-2001
3
26,15
This species vulnerability is associated to habitat accessibility by traditional ornamental fishermen and to opportunistic commercial fishermen fishing for food. The average post-capture mortality of this species ranges between 2 - 5 %. Potamotrygon cf. hystrix represents 31,25 % of all freshwater stingrays legally exported from Brazil Its captures are monitored and the number of individuals exported annually is controlled to avoid stocks depletion.
Potamotrygon motoro (Figure 3) is one of the most fecund stingrays and presents a wide distribution in all Neotropical region. Its captures and exportations are monitored too. There is no evidence of reduction in the abundance in this species, but a strict export control must exist to avoid misidentification of this species with the endemic P. leopoldi and P. henlei. The post-capture mortality is estimated between 10 - 12 %.
Figure 3: Potamotrygon motoro (Photo: Mauricio P. Almeida).
Potamotrygon orbignyi (Figure 4) is a well-distributed species in all AmazonBasin. It is a highly polychromatic stingray and sometimes difficult to be recognized, especially due to the existence of some faded color patterns. The evaluation of CPUE for this species did not show reduction in abundance and post-capture mortality ranges from 8 - 10 %.
Figure 4 - Potamotrygon orbignyi (Photo: Patricia Charvet-Almeida).
Potamotrygon schroederi (Figure 5) is a rare stingray with not many exports records. This is due partially because this species has the highest post-capture mortality (10 - 12 %) of all legally exported stingrays. The capture and exportation of this species must also be controlled because it might be irregularly exported as Potamotrygon cf. hystrix.
Figure 5 - Potamotrygon schroederi (Photo: Maria Lúcia G. Araújo).
Artisanal fisheries also capture potamotrygonids as a food source. These captures are restricted to some areas, such as the Amazon estuary (Area B), where longlines are used as the main fishing gear. This stingray fishery is considered of low economic value. Potamotrygonids are not the main target species but are never discarded when caught and are sold at local fish markets. At least three species are caught in this fishery: Plesiotrygon iwamae, Potamotrygon orbignyi and P. scobina (Charvet-Almeida, 2001; Almeida, 2003).
Incidental capture by commercial fisheries with trawl net happen along Solimões-AmazonasRiver, and it has introduced an unknown mortality rate on freshwater stingrays stocks.
The negative image of freshwater stingrays cause the “negative fishery” The effect of disturbance from ecotourism operations has removed at least 21 000 individuals Potamotrygonidae (mainly Potamotrygon orbignyi and Paratrygon aiereba) at Rio Negro Basin This kind of fishery is developed by some ecotourism companies to avoid accidents with freshwater stingrays. It is an unregulated activity because is not considered “fishery” by Brazilian Environmental Agency (IBAMA) (Araújo et al 2004).
Brazil is in South America the only country that has a specific regulation to control the export of freshwater stingrays species to ornamental trade. Two of the three endemic species permitted to be exported Potamotrygon henlei and P. leopoldi are in basins where dam projects are planning to be developed in the next years. The other endemic species Potamotrygon cf hystrix will need soon National protection of its habitat because in this range ecotourism projects and dragging activities of Rio Negro will compromise its abundance Habitat damage or loss, can deplete freshwater stingrays population more severity than fisheries. (Araújo et 2004)
A critic question at ornamental fish trade is mortality post-capture. The values estimated for freshwater stingray depends of the species rusticity, fishermen practice and exportation area facilities.
The causes of mortality can be categorized as high density in the tanks or plastic boxes, oxygen and pH requirements, and skin lesions (inflammatory oedema) around the mouth, the anterior margin of the disc and pelvic fins. Potamotrygon cf hystrix exhibit the smallest mortality rate what justify its high capture rates, the opposite happens with P. schroederi
Many species of freshwater stingrays occur in more than one country, this is the case of P. motoro, P. orbignyi, P schroederi, Paratrygon aiereba and Plesiotrygon iwamae but until now there are no shared stocks. Despite the fact that Brazilian scientist has proposed a National Plan to management the capture of Potamotrygonidae from commercial vessels, and practice of negative fishery, any effective measured has been considering by IBAMA
Conclusions
The importance to ornamental fish industry is having stingray to offer to ornamental trade, cannot be ignored because this activity employs at least 10.000 families in Brazilian Amazon. The lack of adequate identification of some freshwater stingrays species is a problem that must be solve soon, because the population models to Elasmobranch species require a species-specific data on life cycle parameters. A conservation program to freshwater stingrays species to be well succeed must consider not only the regulation of fish activities but the habitat deterioration and loss, as well the development of ecotourism.
[FONT="]
[/FONT] References
Almeida, M. P. 2003 .Pesca, Policromatismo e Aspectos Sistemáticos de Potamotrygon scobina,Garman 1913 (Chondrichthyes: Potamotrygonidae) da Região da Ilha de Colares da IIha de Marajó - Pará. Masters Dissertation. Belém, Museu Paraense Emílio Goeldi & Universidade Federal do Pará. 145 p.
Almeida, M. P.; Charvet-Almeida, P. & Viana, A. S. 2003. Polychromatic and Morphometric Aspects of the Freshwater Stingray Potamotrygon scobina (Chondrichthyes: Potamotrygonidae) in the Marajó Bay Region (Pará, Brazil).
Araújo, M. L. G., 1998. Biologia Reprodutiva e Pesca de Potamotrygon sp. C (Chondrichthyes - Potamotrygonidae), no Médio Rio Negro, Amazonas. Masters Dissertation. Manaus, Instituto Nacional de Pesquisas da Amazônia & Universidade do Amazonas. 171 p
Araújo, M. L. G. 2001. Plano de Monitoramento de Arraias de Água Doce – Technical Report Convênio IBAMA-AM/ACEPOAM. 29 p.
Araújo, M. L. G , Charvet-Almeida, P, Almeida M. P , Pereira, H.. 2004. Freshwater Stingrays (Potamotrygonidae): status, conservation and management challenges. Information document AC 20 info 08:1-6 http://www.cites.org/common/cttee/animals/20/E20-inf-08.pdf
Barcellos, J. F. M. 1996. Amônia, Uréia e o Conteúdo do Oxigênio do Sangue de Potamotrygon sp (Chondrichtyes
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