Ingestion and selection of suprabenthic crustaceans by small-sized fishes in a lower saltmarsh system

Abstract

. Abstract: This study was performed in the lower saltmarsh system of the Arrozal, in the Cananéia lagoon estuarine region (25"02'S-47"56'W), Brazil. Suprabenthic fauna was surveyed with a small sledge and fishes were captured with casting and set nets to analyse: crustacean fauna as food for local fish species; difference in the diet at different times of the year; if there is diet overlap between species and the feeding behaviour of the species analysed. The fauna of Arrozal is poor in s{>ecies, dominated mainly by Metamysidopsis elongata atlantica, Acartia lilljeborgr,Atylus minikoi, decapod larvae, and reveals a strong seasonal variation. The fishes were alI carnivorous with suprabenthic crustacean as their main food resource. Seasonal changes in food supply are also reflected in the diet. Of the 12 fish species collected sixwere opportunishc feeders whereas sixothers were selective feeders. Food overlap value of 0.08 for alI of the fish community indicates an almost completely distinct food niches. The increased overlapping of summer food between Cathorops spixii and species of Group 11and between Oligop/itessp and species of Group I seems to have two different explanations: 1) the '"nunishing of food supply for species feeding on benthic originated suprabenthic crustaceans and 2) overabundance of planktonic forms of suprabenthos as well as a period of high feeding activity of fishes with such diet.. Resumo: O presente estudo foi realizado no infralitoral contíguo à marisma, na Ponta do Arrozal, região estuarina lagunar de Cananéia (25°02'S-47"56'W), Brasil. A fauna suprabêntica foi amostrada com uma pequena draga e os peixes capturados com tarrafa e rede de espera, com a finalidade de analisar: a composição de espécies dos crustáceos suprabênticos como itens alimentares dos peixes; diferenças na dieta em diferentes época~do ano; se ocorre sobreposição alImentar entre as espécies e o comportamento alimentar das espécies de peixe analisadas. A fauna suprabêntica do Arrozal é pobre em espécies, dominada principalmente por Metamysidopsis elongata atlantica, Acartia /illjeborgi,Atylus minikoi e larvas de decapoda, e revela uma forte variação temporal. Os peixes são todos carnívoros e têm crustáceos suprabênticos como sua principal fonte alimentar. Variação temporal no suprimento alimentar se reflete na dieta. Das 12 espécies de peixes coletadas, 6 são oportunistas e 6 seletivas, em relação à captura do alimento. O valor da sobreposição alimentar de 0,08 para toda a comunidade de peixes indica nichos alimentares completamente distintos. O aumento de sobreposição alimentar no verão entre Cathoropsis spixii e espécies do Grupo 11e Oligop/itessp e espécies do Grupo I parece ter duas explicações diferentes: 1) a diminuição do fornecimento alimentar para as espécies que se alimentaram de crustáceos suprabênticos com origem bêntica e 2) superabundância de formas planctônicas do suprabentos, assim como um período de alta atividade alimentar para peixes com esta dieta.

Suprabenthic amphipods from the littoral zone of Barlovento, Venezuela: spatial distribution and seasonal variation

“…Nototropis minikoi is a cosmopolitan species reported in plankton samples and in sea weeds and swarms of this species have been reported in shallow waters (Naomi, 1979). Nototropis minikoi has also been reported as the preponderant species in a Brazilian estuary in winter, and serves as an important food source for fishes (Wakabara et al, 1996).…”

Seasonal composition and spatial distribution of macrobenthic associations along an estuarine gradient in Itanhaém, São Paulo, Brazil.

“…Fluc tua tions in fresh wa ter in flow as so cia ted to ant hro po ge nic fac tors are li kely to play a ro le in the main te nance of low va lues of di ver sity (Tes ke & Wool dridge, 2001). The low spe cies rich ness and di versity va lues re cor ded he re for the Itan haém ri ver es tuary ha ve al so been re cor ded pre viously for 6 VALÉRIO-BERARDO et al Ta ra ram et al, 1996;Wa ka ba ra et al, 1996;Ri bei ro et al, 1997;Pas cual et al, 2002). The low va lues of di ver sity are as so cia ted to a high nu me ri cal abun dan ce of a few spe cies, H. si mi lis and C. sa le bro sa, as well as to low spe cies rich ness.…”