Dinâmica trófica de Plagioscion squamosissimus (Perciformes, Sciaenidae) em trechos de influência da represa Capivara (rios Paranapanema e Tibagi)

Abstract

ABSTRACT. Trophic dynamic of Plagioscion squamosissimus (Perciformes, Scianidae) in stretches under influence of the Capivara dam (Paranapanema and Tibagi rivers). Plagioscion squamosissimus (Heckel, 1840) was studied in five stretches in Paranapanema and Tibagi rivers under the influence of the Capivara reservoir. The samplings were made on a monthly basis during the 1992/1993 and 1994/1995 periods and seasonally during the 2001/2002 period. The captures were made with gillnets with meshes varying between 2 and 12 cm. A total of 993 specimens had their stomach analyzed. The identified food items were grouped in trophic categories and analyzed by the percent composition method. The diet composition was compared among sampling periods and among stretches by the similarity analysis using the Bray-Curtis' coefficient. The results indicated that the consumption of food items was uniform in all periods and stretches analysed. The food items found were grouped in six categories: fishes, shrimp, Odonata, Ephemeroptera, other insect groups and "others" (plant material, detritus and rarely-found organisms). In all stretches and during all the studied periods, P. squamosissimus presented a carnivorous diet, and during the 2001/2002 period the item shrimp (Macrobrachium amazonicum) represented the largest portion of the diet. Concomitant with the shift from fish to shrimp, there were also changes in feeding behavior, shown by the changes in feeding frequency in food taking and in the variety of consumed food items. A large number of prey individuals were found in the stomach contents when P. squamosissimus fed on shrimp, with most specimens feeding exclusively on this food item. KEYWORDS.Introduced species, pescada-do-Piauí, non-native fish, freshwater, predation. Os itens alimentares identificados foram agrupados em categorias e analisados pelo método da composição percentual. A composição da dieta foi comparada entre os períodos de amostragens e entre trechos, pela análise de similaridade usando o coeficiente de Bray-Curtis. Os resultados indicaram que em todos os períodos e em todos os trechos houve uniformidade no consumo dos tipos de itens alimentares. Os itens encontrados foram agrupados em seis categorias: peixes, camarão, Odonata, Ephemeroptera, outros grupos de insetos e outros (material vegetal, detritos e organismos, raramente encontrados). Em todos os trechos e em todas as épocas analisadas, P. squamosissimus se manteve como carnívora, e no período 2001/2002 o item camarão (Macrobrachium amazonicum) foi o de maior participação em sua dieta. Concomitante com o fato de a corvina trocar de alimento substituindo peixes por camarão, mudou o comportamento quanto à freqüência na tomada de alimento e na variedade de tipos de itens consumidos. Quando P. squamosissimus utiliza camarão, maior número de indivíduos são encontrados nos estômagos, na maioria dos casos com apenas este tipo de item. PALAVRAS-CHAVE.Espécie introduzida, pescada-do-Piauí, peixe não nativo, água doce, predação.A corvina Plagioscion squamosissimus ...

Reproductive biology of Plagioscion magdalenae (Teleostei: Sciaenidae) (Steindachner, 1878) in the bay of Marajo, Amazon Estuary, Brazil

“…Regarding the marine and estuarine species, information on the population dynamics is restricted to specific areas of the Amazon Estuary, considering a few species, such as Scomberomorus brasiliensis, Macrodon ancylodon, Cynoscion acoupa, Sciades parkeri, Cathorops spixii, Stellifer rastrifer, S. naso and Aspredo aspredo (Camargo & Isaac, 1998;Espírito Santo & Isaac, 1999;MMA, 2006). With regards to freshwater sciaenids, some studies on ecology and population dynamics are mainly available for the cogeneric species, the white hake, P. squamosissimus (Rodrigues et al, 1988;Braga, 1997Braga, , 2001Castro, 1999;Carnelós & Benedito-Cecilio, 2002;Stefani et al, 2005;Bennemann et al, 2006). In relation to P. magdalenae, only some information is available on the population parameters in the middle Xingu (Carmargo & Giarrizo, 2009).…”

Aquatic insects as the main food resource of fish the community in a Neotropical reservoir

“…This species, widely described as piscivorous (Almeida et al, 1997;Hahn et al, 1997a), presented Odonata nymphs and shrimp as their main food resources in Nova Avanhandava Reservoir. In stretches under the influence of the Capivara Reservoir (Paranapanema River), Bennemann et al (2006) observed that, since the introduction of corvina in 1992 to 2002, this species switched their diet from fish (mainly A. altiparanae) to shrimps, due to the reduction in the abundance of prey species, and to the fact that this species is not a selective predator, eating all prey that is available.…”

Artisanal fisheries in a Brazilian hypereutrophic reservoir: Barra Bonita reservoir, middle Tietê river

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