Electrofishing as a sampling technique for coastal stream fish populations and communities in the Southeast of Brazil

Abstract

Electrofishing adequacy was tested as a technique to obtain quantitative data of coastal stream fish populations and communities in the Southeast of Brazil. Seven field trips, between July/94 and July/95, were done in 5 localities of the Ubatiba fluvial system (Maricá, RJ). Seventeen species, among the 22 collected, had their numbers estimated through the Zipping method, the model used to test the sampling methodology. At each field trip, three removals with electrofishing were done in each locality and, according to the number of obtained species at each locality/field trip, we analysed 315 cases. Nineteen cases, among 315, showed failure condition. Estimates were significant (p < 0.01) in 96% of the studied cases. Non-significant cases were obtained for rare species due to over and randomly efficient electrofishing in 63.3% and 36.4% of the cases, respectively. No correlation was found between catchability and the estimated number of individuals and/or environmental characteristics. High values for sampling efficiency (> 85%) were found for all estimates. An experimental analyses were done for one locality and, the comparison between the estimates for 3 and 6 successive removals showed a mean error and a standard deviation of 5.5% and 2.1% respectively. Therefore, it can be concluded that electrofishing was an efficient method for quantitative data analysis of fish populations and communities in the Ubatiba fluvial system.

Plasticity in the diet of Astyanax taeniatus in a coastal stream from south-east Brazil

“…Samples were collected from March 2006 to February 2007 by electric fishing in sites F1 and F2 (CA -1600 W, 220 V, 2-4 A - Mazzoni et al, 2000), and using dragnets (mesh size 5 mm) in site A due to difficult access and high water turbidity. Each study site was characterised by collecting the following data: (i) stream width; (ii) stream depth; (iii) current velocity; (iv) river bed substrate; (v) water turbidity; (vi) vegetation cover; and (vii) type of mesohabitats present.…”

Aspectos da alimentação de Bryconamericus microcephalus(Characiformes, Tetragonopterinae) no córrego Andorinha, Ilha Grande – RJ

“…Atualmente, apenas 5% da vegetação original da Mata Atlântica encontra-se intacta, determinando que os sistemas naturais desta região estão em franca modificação (Coltrinari, 1996) com muitas espécies em sério risco de desaparecimento (Menezes et al, 1990;Mazzoni et al, 2000). Esse tipo de informação, associado à elevada taxa de perda de ambientes naturais (desflorestamento) aponta para a importância de estudos que viabilizem o entendimento da dinâmica das populações e comunidades.…”

Ictiofauna do Ribeirão Limoeiro, Bacia do Rio Cachoeira, BA

“…Foram realizadas quatro amostragens de peixes em 2007 (março, junho, setembro e dezembro) utilizando a pesca elétrica, com metodologia modificada a partir de Suzuki et al (1997) e Mazzoni et al (2000). Esse método consiste em produzir um campo elétrico na água, passando uma corrente entre dois eletrodos submersos.…”