Factors affecting spatial variability in seine net catches of fish in the surf zone of False Bay, South Africa

Abstract

Ichthyofaunal assemblages at 11 surf zone localities along the perimeter of False Bay South Afnca were sampled by seine netting at monthly intervals between July 1991 and J u n e 1993 Sampllng localit~es were selected to encompass as wide a range of physical vanables as possible incorporatlng sheltered, exposed, sandy and mixed-shore habitats, thus providing a colnprehensive assessment of the factors lnfluenclng surf zone fish assemblages Data collected at each site were averaged over the 2 yr p e i~o d in order to highlight the influence of various physical environnlental vanables on the abundance and co~nmunity structure ot these assemblages Athenr~a brevlceps, Liza rlchardsonii and Rhahdosarg~ls gloh~ceps were numeiically domlnant at all sites together providing between 69 and 99%) of the catches Overall catches of juvenile flsh exceeded that ot adult fish, making up almost 53 of the catch Fish abundance (no ind per 100 m') and number of species recorded at each site ranged from 6 to 199 and from 12 to 31 respectivel) Multivdriate analyses Indicated that the deglee of wave exposure the presencc of emergent rock on the shore dnd turbid~ty were responsible for most of the s p a t~a l vanab~lity in abundance and community structure observed Although of lesser importance abundance of detached macrophytes salinity dnd water temperature also played a role in structuring fish assemblages Species specific preferences for varying combinations of these var~ables are responsible for fluctuations in the structure and overall abundance of assemblages in different a r e a

Efeito do grau de exposição às ondas sobre a comunidade de peixes juvenis em praias arenosas do Município do Rio de Janeiro, Brasil

“…Isto pode ser decorrente de variações no período de atividade das espécies, uma vez que as coletas foram realizadas apenas no período diurno. A sucessão dos dias e noites produz uma oscilação da maioria dos fatores ambientais de interesse ecológico (Margalef 1986), que influenciam a abundância relativa de certas espécies, alterando a composição e a riqueza nas assembléias de peixes (Clark et al 1996). A importância das áreas rasas costeiras no ciclo de vida dos peixes foi demonstrada por Lenanton (1982) que ressaltou a importância de tais áreas para peixes jovens em praias costeiras da Austrália.…”

“…A ação das ondas, considerada como sinônimo de exposição, é um dos fatores primários mais importantes no controle das características físico-químicas na zona de arrebentação (McLachlan 1980). Essa variável ambiental tem uma importante contribuição na composição e estrutura da comunidade íctica (McLachlan et al 1984, Dexter 1990, Clark et al 1996, Clark 1997, devido ao estresse físico local decorrente do quebrar das ondas, afetando a modificação da estrutura do sedimento e/ou as fontes de alimentos (Bennett 1989).…”

“…Fatores como diferenciação nos equipamentos de pesca, metodologia de amostragens e influências ambientais, como abundância de macró-fitas, salinidade e turbidez podem interagir e influenciar os resultados de testes sobre o grau de exposição às ondas (Monteiro-Neto & Musick 1994, Clark 1996, Gaelzer & Zalmon 2003.…”

Spatial and temporal variations of diurnal ichthyofauna on surf-zone of São Francisco do Itabapoana beaches, Rio de Janeiro State, Brazil

“…As an important beach modeler (Hoefel, 1998) and transporter of organic matter and nutrients between continent and sea (Yañez-Aranciabia, 1978), the surf-zones support a widely fauna, mainly zooplankton and fishes (Maes et al, 1998). In fact, it has been observed that environmental complexity in terms of wave exposure and microhabitats formation, like seagrass and reefs, are related to composition and dynamics of surf-zone fish assemblages (Clark et al, 1996;Clark, 1997). Surf-zone ichthyofauna are both seasonal and diel dynamic (Modde and Ross, 1981).…”

Diel Variations and Ecological Aspects in Fish Assemblages of a Sandy Beach in the Semi-Arid Region of Northeast Brazil.

“…Moreover, the incident light exerts influence on the abundance of many species, changing in the composition and richness of fish assemblages (Clark et al, 1996). These changes in fish community may be associated with the use of the sandy beach at different times of the day.…”