Effects of fishing technique on assessing species composition in aquatic systems in semi-arid Brazil

Abstract

In most ecological field research, appropriate sampling is critical for the understanding of processes underlying fish populations and communities, and is even more important in heterogeneous environments such as the aquatic systems of the semi-arid region of Brazil. This study intends to make a contribution to the development of sampling programs and gear selection in aquatic systems of semi-arid Brazil by evaluating the effects of different fishing techniques on the assessment of richness and composition of the fish fauna in selected aquatic environments. Six sites were selected to represent typical artificial (reservoirs) and natural (intermittent streams) environments and four different types of sampling gear were applied to each site during four occasions. The present study shows that when selecting sampling techniques to be used in aquatic systems in semi-arid Brazil, one must consider the objectives of the study, e.g. ecological or taxonomic, in order to decide on inclusion of rare species in the sampling population. Also, the effect of the sampling gear on natural abundances of fish must be considered given that some sampling techniques are highly detrimental to fish population numbers.Keywords: semi-arid, fish, richness, sampling technique, intermittent streams. Efeitos de diferentes artes de pesca na avaliação da composição de espécies em ambientes aquáticos do semiárido brasileiro ResumoNa maioria dos estudos ecológicos, uma amostragem representativa é crucial para o conhecimento dos processos que organizam populações e comunidades de peixes, principalmente em ambientes reconhecidamente heterogêneos como os ecossistemas aquáticos da região semiárida do Brasil. O presente estudo pretende contribuir para este conhecimento avaliando os efeitos de diferentes técnicas de captura de peixes na riqueza e composição das espécies amostradas em ambientes aquáticos do semiárido. Seis pontos de coleta foram selecionados, representando ambientes aquáticos artificiais (açudes) e naturais (rios intermitentes), onde quatro tipos de apetrechos de pesca foram empregados em quatro ocasiões. O presente estudo mostra que, ao selecionar técnicas de amostragem de peixes em ambientes aquáticos do semiárido brasileiro, dois fatores devem ser levados em consideração: primeiro, os objetivos do estudo, ecológicos ou taxonômicos, para se avaliar a importância da inclusão de espécies raras na população amostral; e segundo, os efeitos da técnica de amostragem na abundância natural de espécies, tendo em vista que algumas artes de pesca têm um efeito negativo nos números populacionais das espécies de peixes.Palavras-chave: semiárido, peixes, riqueza de espécies, artes de pesca, rios intermitentes.

Parotocinclus seridoensis, a new hypoptopomatine catfish (Siluriformes: Loricariidae) from the upper rio Piranhas-Açu basin, northeastern Brazil

“…Total vertebrae 24 (2 c&s). this microhabitat was found only at the right margin, where P. jumbo was observed forming small shoals, behavior already registered by Britski & Garavello (2002 (Medeiros et al, 2010). In addition to these species, in rio Piranhas were also collected: Serrasalmus rhombeus (Linnaeus), Triportheus signatus (Garman) and Trachelyopterus galeatus (Linnaeus).…”

Ichthyofauna of the Reserva Biológica Guaribas and surrounding areas, state of Paraíba, Brazil

“…Fish collection was performed during daylight hours based on Medeiros et al (2010) using a short beach seine net (4 m long, 1.5 m high and 5 mm mesh), a long beach seine net (20 m long, 2 m high and 12 mm mesh), a cast net (2.4 m high and 12 mm mesh) and a dip net (50 cm wide and 5 mm mesh). Effort of capture was similar across sampling occasions and sites.…”

Ichthyofauna of two reservoirs in the middle Acaraú river basin, Ceará, Northeastern Brazil

“…The relatively small fish diversity observed in our study is probably the result of the type of gear employed (gillnets) in a single habitat, the limnetic zone of the reservoirs (Medeiros et al 2010). The use of other fishing methods, such as cast nets or seine nets, might have resulted in the capture of additional species, including Poecilia vivipara, which has previously been observed during field work in local coastal freshwater systems (Sánchez-Botero, personal observation); and Synbranchus marmoratus, a native species registered by Batista in 2011 (unpublished data) based on interviews with local subsistence fishermen.…”