Ictiofauna e ecologia trofica de peixes em ambientes praiais da Ilha das Peças, complexo estuarino de Paranagua, Parana

Abstract

The study took place between 20005 and 2006, in three areas: Pontal do Sul, Barrancos and Shangrilá and the main aim was to evaluate discards production and the interaction of seabirds with fisheries discards on the Parana coast. The methods were based on three different focuses: (1) discards composition, through direct observations in field and manipulation of discards samples in laboratory referring to each area. (2) the use of those discards by seabirds on the shore line and at open sea were evaluated through weekly counts on the shore line and monthly counts on the open sea and (3) the reproduction of Larus dominicanus was evaluated during montly samples in the Archipelago of Currais during its breeding cycle. The discards composition was identified as 96 species of fish based on field samples and 70 species of fish based on laboratory samples, mainly in the form of whole fish. Extrapolating the value of discard produced by fisheries activities in the present area based on laboratory samples we obtained an annual discard production of 129.529.6 Kg. In relation to the interaction on the shore line, we counted nine species of birds using discards, with numeric prominence for Kelp gulls, Larus dominicanus,while on the open sea we observed eight species of birds, with Fregata magnificens and Sula leucogaster being the predominant species. Kleptoparasitism behaviour was observed mainly in intraspecific interactions on the shore line (78,69%), as on the open sea (71,92%). There was a tendency of higher levels of kleptoparasitism during the moratorium period, a situation where trawling activity is not permitted. The first indications of reproduction, was represented by pair flight and courtship, these were observed during May and June. Construction of the first nests, and the beginning of egg laying, occurred in July, with reproductive peak in September. We counted 45 nests distributed accross four areas, located in the periphery of the island, close to the water. In relation to weight, width and length we obtained mean values of 84,42mm±8,83 g, 49,30±1,78mm e 70,89±3,20mm respectively. During December the last indications of reproduction were observed, represented by completely feathered nestlings and beginning the first flights.