Utilização de índices ecológicos em assembléias de peixes como instrumento de avaliação da degradação ambiental em programas de monitoramento

Abstract

Este trabalho utiliza índices ecológicos em taxocenoses de peixes (constância de ocorrência, diversidade de espécies, riqueza, equitabilidade, índice de qualidade integrado (IQ)) como instrumento de avaliação da degradação ambiental. As amostragens foram padronizadas e realizadas sazonalmente durante dois anos, com rede de arrasto do tipo picaré, em onze pontos da bacia hidrográfica do lago Guaíba. Os pontos que apresentaram maior regularidade sazonal nos índices coincidem com locais de melhor qualidade ambiental indicados por outros fatores (frequência de anomalias, DBO5, temperatura, coliformes totais, oxigênio dissolvido). O cálculo do índice de qualidade integrado (IQ), entretanto, foi extremamente influenciado pela abundância e riqueza de espécies, sendo que os locais considerados de melhor qualidade por este índice correspondem aos de pior qualidade ambiental indicados por outros fatores. A análise realizada demonstrou que à medida que a qualidade da água melhora, o Índice de Margalef diminui. Isto demonstra que mesmo havendo uma melhora na qualidade da água, não houve uma melhora da estrutura da comunidade deste local.

Diet and trophic guilds of fish assemblages in two streams with different anthropic impacts in the northwest of Paraná, Brazil

“…Some studies addressing urban streams have detected the presence of trophic groups such as omnivores and detritivores , ALEXANDRE et al 2010. This may be the result of a degradation of the food base, which provides opportunities for exploitation by more opportunistic and resistant species (ARAÚJO 1998, FLORES-LOPES et al 2010. According to ABELHA et al (2001), trophic specialization among tropical fish is rare, and the apparent specialization shown by some species may be more related to the availability of food resources in the aquatic system than to actual trophic specialization by a species.…”

Assessment of environmental quality through analysis of frequency of the black spot disease in an assemblage of fish, Guaíba lake, RS, Brazil

“…It was observed in this study that fish responded to the presence of parasites with an encapsulation formed by cellular involucres around the parasite, which can be fragile or resistant, sometimes consisting of many concentric layers of cells derived mainly from connective tissue, as described by Flores-Lopes et al (2002) and Rohde (1984), where a separate capsule originating from the host is formed. Metacercariae infestation is extremely common in fish and most often results in severe injuries for the hosts (Rohde, 1984).…”

“…Moreover, another study (Flores-Lopes and Reuss-Strenzel, 2011) on the morphological changes could verify that point 3 did not show statistically significant result by chi-square test. Studying the composition of fish fauna, Flores-Lopes et al (2010) found that point 5 showed the diversity index more regularly during the sampling period, thereby being classified as quality mean by integrated quality index.…”

Record of morphological deformities in Corydoras aff. longipinnis in two reservoirs under urban influence in Upper Iguaçu and Southern Coastal basins in Paraná State, Brazil

“…Also, tumors (neoplasias) on bones and skin and deformations on vertebral column (kyphosis, lordosis and scoliosis) can be observed (Flores-Lopes & Reuss-Strenzel, 2011). The occurrence of these morphological conditions coupled with other metrics, such as proportion of taxonomic groups, quantity of tolerant species, trophic position of species, fluctuating asymmetry, and the fish health, are present in many environmental assessments (Jaramillo-Villa & Caramaschi, 2008;Flores-Lopes et al 2010). …”