Aspectos ecológicos de endoparasitos de piranha vermelha (Pygocentrus nattereri, Kner, 1860) proveniente do rio Cuiabá / Ecological aspects of endoparasites in red piranha (Pygocentrus nattereri Kner, 1860) from Cuiabá river, Mato Grosso, Brazil

This study evaluated the infrapopulations of parasites in red piranha (Pygocentrus nattereri) from theCuiabá river, Mato Grosso, Brazil. One hundred sixty-four specimens of red piranha were captured and examined in the period from October to December, 2007 in Barão de Melgaço, Mato Grosso, Brazil. The parasitism was reviewed by data of prevalence, localization, mean intensity of infection, and abundancefor each group of parasite found. In the examined fishes, nematodes (Eustrongylides spp., Contracaecum spp,. and Procamallanus spp.) and pentastomids were found. Among the examined fishes, 141 (86 percent) presented parasitism by at least one species of parasite; from those, 23 (14 percent) by nematodes identified as Eustrongylides spp., 106 (64.6 percent) by Contracaecum spp., 55 (33.5 percent) by Procamallanus spp., and 90 (54.9 percent) by pentastomids. About the localization of the parasites, from the 23 fishes positive to the infection by Eustrongylides spp., 19 (82.6 percent) presented larvae in the muscle, two (8.7 percent)in the celomatic cavity, and two (8.7 percent) in the air bladder. From the 106 fishes positive to the infection by larvae of Contracacecum spp., 105 (99 percent) presented the celomatic cavity as the locus of parasitism, and one (0.9 percent) presented the parasitism in the air bladder. All the fishes positives to the infection by Procamallanus spp., presented the intestine as parasitism site. From the 90 fishes parasited by pentastomids, 41 (45.6 percent) presented the parasitism in the muscle, 17 (18.9 percent) in the celomatic cavity, and 32 (35.6 percent) in the air bladder. The mean intensities of infection by larvae of Contracaecum spp. and Eustrongylides spp., Procamallanus spp., and pentastomids were 1.04; 3.93; 2.27; and 3.72 parasites per fish, respectively, and the abundance values were 0.14; 2.54; 0.76; and 2.04 parasites per fish, respectively.

Aspectos ecológicos de endoparasitos de piranha vermelha (Pygocentrus nattereri, Kner, 1860) proveniente do rio Cuiabá / Ecological aspects of endoparasites in red piranha (Pygocentrus nattereri Kner, 1860) from Cuiabá river, Mato Grosso, Brazil

This study evaluated the infrapopulations of parasites in red piranha (Pygocentrus nattereri) from theCuiabá river, Mato Grosso, Brazil. One hundred sixty-four specimens of red piranha were captured and examined in the period from October to December, 2007 in Barão de Melgaço, Mato Grosso, Brazil. The parasitism was reviewed by data of prevalence, localization, mean intensity of infection, and abundancefor each group of parasite found. In the examined fishes, nematodes (Eustrongylides spp., Contracaecum spp,. and Procamallanus spp.) and pentastomids were found. Among the examined fishes, 141 (86%) presented parasitism by at least one species of parasite; from those, 23 (14%) by nematodes identified as Eustrongylides spp., 106 (64.6%) by Contracaecum spp., 55 (33.5%) by Procamallanus spp., and 90 (54.9%) by pentastomids. About the localization of the parasites, from the 23 fishes positive to the infection by Eustrongylides spp., 19 (82.6%) presented larvae in the muscle, two (8.7%) in the celomatic cavity, and two (8.7%) in the air bladder. From the 106 fishes positive to the infection by larvae of Contracacecum spp., 105 (99%) presented the celomatic cavity as the locus of parasitism, and one (0.9%) presented the parasitism in the air bladder. All the fishes positives to the infection by Procamallanus spp., presented the intestine as parasitism site. From the 90 fishes parasited by pentastomids, 41 (45.6%) presented the parasitism in the muscle, 17 (18.9%) in the celomatic cavity, and 32 (35.6%) in the air bladder. The mean intensities of infection by larvae of Contracaecum spp. and Eustrongylides spp., Procamallanus spp., and pentastomids were 1.04; 3.93; 2.27; and 3.72 parasites per fish, respectively, and the abundance values were 0.14; 2.54; 0.76; and 2.04 parasites per fish, respectively.(AU)

Sustainable harvest of two large predatory catfish in the Cuiabá river basin, northern Pantanal, Brazil.

Fishery is an important economic activity in the Pantanal. Among the regions species, the Pimelodidae catfish stands out as an important part of the annual catch. This study assesses the structure, exploitation and stock management of Hemisorubim platyrhynchos and Sorubim cf. lima, the sixth and seventh largest Pimelodidae of the Pantanal. The analysis is based on fish caught by commercial fishing in the Cuiabá river and landed at the "Antônio Moysés Nadaf" Market in the Cuiabá city, Mato Grosso state, Brazil. The findings indicate that commercial fishing activities target several fish cohorts and that usually only individuals above mean length at first maturation are caught. Estimates of the instantaneous mortality coefficient show that the current fishing mortality is low. Simulations of relative yield-per-recruit model demonstrate that the current yield of two species could be greater if the fishery effort were increased, indicating that the stocks are underexploited. However, an increase in current fishery efforts should be viewed with caution, since the stock-recruitment relationship for the species is unknown. The results indicate that the current harvest of two species in the Cuiabá River Basin is sustainable.

Sustainable harvest of two large predatory catfish in the Cuiabá river basin, northern Pantanal, Brazil

Fishery is an important economic activity in the Pantanal. Among the regionÆs species, the Pimelodidae catfish stands out as an important part of the annual catch. This study assesses the structure, exploitation and stock management of Hemisorubim platyrhynchos and Sorubim cf. lima, the sixth and seventh largest Pimelodidae of the Pantanal. The analysis is based on fish caught by commercial fishing in the Cuiabá river and landed at the "Antônio Moysés Nadaf" Market in the Cuiabá city, Mato Grosso state, Brazil. The findings indicate that commercial fishing activities target several fish cohorts and that usually only individuals above mean length at first maturation are caught. Estimates of the instantaneous mortality coefficient show that the current fishing mortality is low. Simulations of relative yield-per-recruit model demonstrate that the current yield of two species could be greater if the fishery effort were increased, indicating that the stocks are underexploited. However, an increase in current fishery efforts should be viewed with caution, since the stock-recruitment relationship for the species is unknown. The results indicate that the current harvest of two species in the Cuiabá River Basin is sustainable.

A pesca é uma importante atividade econômica no Pantanal. Entre as espécies que ocorrem na região, os bagres Pimelodídeos se destacam como uma importante parte da captura anual. Este estudo avalia a estrutura, estado de explotação e o manejo do estoque do Hemisorubim platyrhynchos e Sorubim cf. lima, respectivamente o sexto e o sétimo maiores Pimelodídeos do Pantanal. As análises se baseiam nos peixes capturados no Rio Cuiabá pela pesca e desembarcados no Mercado Municipal "Antônio Moysés Nadaf", na cidade de Cuiabá, Estado do Mato Grosso. Os resultados indicam que a pesca comercial incide sobre várias coortes do estoque e que usualmente somente são capturados indivíduos acima do comprimento médio na primeira maturação. Estimativas do coeficiente instantâneo de mortalidade mostram que a mortalidade por pesca atual é baixa. Simulações do modelo de rendimento relativo por recruta indicam que o rendimento atual das duas espécies poderia aumentar com um aumento no esforço de pesca, indicando que o estoque está subexplotado. Contudo, um aumento no esforço de pesca corrente deve ser visto com cautela, uma vez que a relação entre o estoque e o recrutamento para as espécies é desconhecido. Em síntese, os resultados indicam que o nível atual de captura das duas espécies no Rio Cuiabá é sustentável.

First gonadal maturation of Pinirampus pirinampu (Siluriformes: Pimelodidae) in the Pantanal, Mato Grosso do Sul State, Brazil.

Information regarding the reproductive cycle of commercially exploited fish species is extremely important for their appropriate management. The reproductive size of Pinirampus pirinampu (Spix, 1829) was determined for a population studied in the Pantanal wetlands of western Brazil. Samples were taken in September, October, and December 1997, and in February and March 1998. Gonadal stages were macroscopically determined and a monthly gonadossomatic index (GSI) was used to determine the breeding period. The length of the first gonadal maturation was determined by classifying male and female adults and immature fish into length classes. The data on the adult individuals were plotted on graphs and the median values estimated to find the length at which 50% of the individuals reached maturity (L50). L100 was also determined. Males and females in the gonadal maturation process were recorded from October on, and the highest frequency was found to occur in February. Individuals with empty gonads occurred from February onwards. The GSI showed that gonadal development began in September and reached its peak in February. The L50 was 574 mm for females and 536 mm for males, while the L100 was 590 mm for females and 580 mm for males.

First gonadal maturation of Pinirampus pirinampu (Siluriformes: Pimelodidae) in the Pantanal, Mato Grosso do Sul State, Brazil

Informações sobre o ciclo reprodutivo de espécies exploradas pela pesca são imprescindíveis para o seu manejo adequado. O tamanho de início da atividade reprodutiva do Pinirampus pirinampu (Spix, 1829) foi determinado. Os exemplares foram capturados em setembro, outubro e dezembro de 1997 e fevereiro e março de 1998. O estádio de desenvolvimento gonadal foi identificado macroscopicamente. O índice gonadossomático médio (IGS), calculado mensalmente, foi utilizado como indicador da época de desova. Para determinação do comprimento da primeira maturação gonadal agruparam-se, separadamente, machos e fêmeas por classes de comprimento em imaturos e adultos. Os resultados referentes aos indivíduos adultos foram lançados em gráficos e a mediana correspondeu à estimativa do comprimento no qual 50% dos indivíduos atingem a maturidade (L50). Foi também determinado o L100, estimativa do comprimento em que todos os indivíduos estão aptos à reprodução. Machos e fêmeas em processo de maturação gonadal foram encontrados a partir de outubro, com maior freqüência em fevereiro, e, somente a partir deste mês, foram encontrados indivíduos com gônadas esvaziadas. O índice gonadossomático mostrou que a partir de setembro inicia-se o processo de desenvolvimento gonadal, com seu valor máximo em fevereiro. O L50 para fêmeas foi 574 mm e para machos foi 536 mm. O L100 para fêmeas foi 590 mm e para os machos, 580 mm.

Age and growth of the porthole shovelnose catfish (Hemisorubim platyrhynchos) in the Pantanal

O jurupoca, Hemisorubim platyrhynchos, é o sexto maior pimelodídeo do Pantanal. Sua idade e crescimento foram estudados a partir dos espinhos de nadadeiras peitorais de exemplares coletados no rio Cuiabá, Pantanal mato-grossense. Os exemplares provieram da pesca comercial e experimental com linha e anzol. A análise do índice de incremento marginal não permitiu que se distinguissem a periodicidade e a época de formação dos anéis de crescimento (H = 4,142; p = 0,247). Porém, o declínio acentuado do índice de incremento marginal registrado na vazante sugere que esse seja o período de formação dos anéis. A estimativa dos parâmetros que descrevem a curva de crescimento de von Bertalanffy, ajustada por meio de regressão não-linear aos comprimentos observados e com o valor do LØ fixado em 64,0 cm (comprimento furcal), foi de k = 0,222 ano-1 e to = -2,149 anos. A longevidade dos indivíduos foi estimada em 11,4 anos. Os resultados indicam que o comprimento furcal é bom preditor da idade para os indivíduos dessa espécie de peixe.

Age, growth and yield per recruit analysis of the pintado Pseudoplatystoma corruscans (Agassiz, 1829) in the Cuiabá River basin, Pantanal Matogrossense, Brazil.

The age and growth of the pintado Pseudoplatystoma corruscans were studied during the period from May 1994 to May 1995. The standard length ranged from 52 to 145 cm and the weight from 1.3 to 41 kg. The biometric relationship between the standard length (Ls) and total length (Ltotal) and between the total weight (Wt) and the standard length (Ls) were obtained for the species, being respectively: Ltotal = 3.296 + 1.069 * Ls and Wt = 0.00624 * Ls(3.134). The condition factor calculated monthly suggests the spawning season to be between the months of February and March. The age was estimated by counting growth rings present in the spines of the pectoral fins, and 10 age classes were detected. The mean distance of the last ring until the border of the spine suggests that the period of least growth is between July and September (dry period). Von Bertalaffy's equation describing the growth of the pintado is: Lt= 183 * [1 - exp - 0.085 * (t + 3.274)]. Total mortality was Z = 0.24 year(-1) and natural mortality M = 0.20 year(-1). As the present level of exploitation, F = Z - M = 0.04 year(-1), we conclude that the pintado stock was still underexploited in the Pantanal in the sampled period.

Age, growth and yield per recruit analysis of the pintado Pseudoplatystoma corruscans (Agassiz, 1829) in the Cuiabá River basin, Pantanal Matogrossense, Brazil

A idade e o crescimento do pintado Pseudoplatystoma corruscans foram estudados durante o período de maio de 1994 a maio de 1995. O comprimento-padrão variou de 52 a 145 cm e o peso total, de 1,3 a 41 kg. As relaçäes biométricas entre comprimento-padrão (Ls) e comprimento total (Ltotal) e entre peso total (Wt) e comprimento-padrão (Ls) foram obtidas, sendo, respectivamente: Ltotal = 3,296 + 1,069 * Ls e Wt = 0,00624 * Ls3,134. O fator de condição, calculado mensalmente, sugere que a desova ocorreu entre os meses de fevereiro e março. A idade foi estimada pela contagem de anéis de crescimento presentes nos raios modificados (esporão) das nadadeiras peitorais, detectando 10 classes etárias. A distância média do último anel até a borda do esporão sugere que o período de menor crescimento ocorreu entre julho e setembro (seca). A equação de von Bertalaffy que descreve o crescimento do pintado é: Lt = 183 * [1 - exp - 0,085 * (t + 3,274)]. A mortalidade total obtida foi Z = 0,24 ano-1 e a mortalidade natural M = 0,20 ano-1. Com o presente nível de explotação, F = Z - M = 0,04 ano-1, conclui-se que o estoque do pintado ainda não estava sobrexplotado na bacia do rio Cuiabá, Pantanal Matogrossense, na época em que foi realizado o estudo.

Age and growth of the Duckbill Catfish (Sorubim cf. lima) in the Pantanal

O Jurupensém, Sorubim lima, é um predador dos grandes rios da América do Sul. A idade e o crescimento do S. lima foram estudados a partir de espinhos de nadadeiras peitorais de exemplares coletados no Rio Cuiabá, Pantanal Mato-grossense. Os exemplares provieram da pesca comercial e experimental, com linha e anzol. A análise do índice de incremento marginal sugere que os anéis de crescimento se formam uma vez ao ano, durante a estação da seca, entre julho e setembro (ANOVA tipo I: F = 4,183; g.l. = 3 e 104; p = 0,008). Os parâmetros que descrevem a curva de crescimento de von Bertalanffy, ajustados por meio de regressão não-linear aos comprimentos observados na idade, foram estimados em: Loo = 56,0 cm (comprimento furcal); k = 0,245 ano-1; to = -2,605 anos. A longevidade dos indivíduos foi estimada em 9,6 anos. Os resultados indicam que o comprimento furcal é um bom preditor de idade para os indivíduos dessa espécie de peixe.

Age and growth of the porthole shovelnose catfish (Hemisorubim platyrhynchos) in the Pantanal.

The porthole shovelnose catfish, Hemisorubim platyrhynchos, is the sixth largest pimelodidae of the Pantanal. Its age and growth were studied using pectoral fin-spines from fish collected in the Cuiabá river basin, Pantanal. The fish, which came from commercial and experimental fisheries, were all caught with hook and line. Growth-ring formation time could not be defined through the Kruskal-Wallis test on marginal increment (H = 4.142; p = 0.247). Nevertheless, decrease in the marginal increment index occurring as waters recede suggests this as the probable time when growth rings form. Estimation of the parameters of von Bertalanffy growth curve, adjusted through nonlinear regression to observed fork lengths, with L(infinity) fixed at 64 cm, were: k = 0.222 year(-1); t(o) = -2.149 years. Individual life span was estimated at 11.4 years. The results suggest that fork length is a good predictor of age for individuals of this species.