Ecologia da pesca e biologia reprodutiva do acará-disco (Symphysodon aequifasciatus, Pellegrin 1904) (Perciformes: Cichilidae) na RDS Piagaçu-Purus, Amazônia Central: subsídios para o manejo sustentável de um recurso natural

Abstract

Historically ornamental fish have been commercially exploited in the Amazon. Nevertheless this exploitation has been carried out without much planning with little attention to the vulnerability of the fish population or to the social economical aspects of the activity for the local fishermen. Among the most known ornamental fish species commercially used is the discus fish (Symphysodon spp.) but very little is known about its biology and ecology. The little information available about this species comes from individuals raised in captivity. This study aimed: a) describe the fishing of discus (Symphysodon aequifasciatus, Cichlidae Pellegrin, 1904), b) determine the abundance and colonization rate through artificial fishing atractors commonly used by local fishermen, c) estimate size at first reproduction, fecundity, sex ratio to develop a management plan for rational commercial use of the species. I also evaluated the efficiency of underwater auditory methods to estimate presence and abundance of discus and the impact of the cutting of the branches on the riparian plant species (“araçá”, Eugenia sp.) used as fish atractors in the water. This study was carried out in three areas of the Sustainable Development Reserve Piagaçu-Purus (SDR-PP) in the dry season from September to November in 2006 and 2007. This study revealed that the fishing of discus occurs in very low intensity and contributes little to the local economy at the SDR-PP and it uses very artesanal forms of capturing, storage and transport. Fishing atractors showed high efficiency as capturing grounds for discus and other commercially important fish species. S. aequifasciatus was the most abundant species representing more than 50% of all cichlids found in the attractors. Mean fecundity was 1.490 eggs (± 304 SD), and population sex ratio was 1:1. Estimated L 50 (body size at which 50% of the population is mature) was 98,4mm (0,38 SD) and 95,8mm (0,86 SD) for females and males respectively. Underwater auditory estimates of discus abundance by the local fishermen predicted the number of discus in the attractors with more than 75% accuracy. Ninety eight percent of the individuals of Eugenia sp. which branches were cut to serve as fish attractors for discus showed regeneration indicating that the impact on this plant species is neglectable. The biological information allied to the local ecological knowledge and understanding of the social aspects involved in the exploitation of discus generated by this study will be incorporated in the management plan for the species.