Exploring the effects of fishing on fish assemblages using Abundance Biomass Comparison (ABC) curves

Abstract

The possible effect of fishing on dominance patterns in the South African south coast demersal trawl fishery is assessed using Abundance Biomass Comparison (ABC) curves for the period 1986–2003. The ABC method compares the ranked distribution of abundance among species against the similar distribution of biomass among species. The temporal pattern in the ABC curves and the W-statistic for two depth groups (<100 m and 101–200 m), and for the whole area combined, shows a gradient of change in the demersal assemblages from neutral (W ≥ 0) towards negative (W < 0), suggesting a disturbed or stressed condition. This corresponds to the onset of longline fishing effort in 1994, still ongoing in 2003, superimposed upon declining trawl effort in the same region. The ABC method shows promise as a guide for assessing the effects of fishing on fish communities, being based on established r- and k-selection theory. More modelling and comparative work is needed to establish acceptable ranges for the W-statistic, and their application in an ecosystem approach to fisheries management.

Changes in the structure of fish assemblages in streams along an undisturbed-impacted gradient, upper Paraná River basin, Central Brazil

“…In this case the biomass curve lies above the abundance curve. In disturbed states there is a dominance of r-selected species displaying small fast-growing bodies and opportunistic comportment, expressed by the biomass curve lying below the abundance curve (Yemane et al, 2005).…”

Long-term changes in fish assemblage following the impoundments of the Three Gorges Reservoir in Hejiang, a protected reach of the upper Yangtze River

“…In undisturbed states, the community was supposed to be dominated by k selection species (slow-growing, large body size, long lifespan and late-maturing), but with increasing disturbance, the system was gradually dominated by r selection species with the attributes of fast-growing, small body size and short lifespan. The ABC can reflect changes not only in relative abundance of large and small species, but also in size composition (Yemane et al, 2005). The present study is the first application of the ABC method to explore fish assemblage changes in the Upper Yangtze River, and the ABC curves and their corresponding W-statistic revealed remarkable temporal variations during the study period.…”

“…The species that considerably increased, such as C. guichenoti, C. heterodon and H. molitrix, were larger-bodied compared with other species; their influx would undoubtedly lead to changes in the body size structure and outweighed the impacts caused by fishing. The large influx of recruits of dominant species can seriously affect the results of ABC analysis, which was also observed by Penczak (1998) and Yemane et al (2005). In this study, we did not examine fish movements (e.g., telemetry and mark-recapture).…”

“…Multivariate clustering methods, such as classification and ordination, were sensitive to changes in community structure, but they did not show exactly the direction of these changes (Yemane et al, 2005). The Abundance Biomass Comparison (ABC) method based on the classical evolutionary theory r and k selection was initially proposed by Warwick (1986) as a technique for monitoring disturbance of benthic invertebrate communities.…”

“…The Abundance Biomass Comparison (ABC) method based on the classical evolutionary theory r and k selection was initially proposed by Warwick (1986) as a technique for monitoring disturbance of benthic invertebrate communities. It was also widely applied to detecting the fish assemblage changes in response to disturbance, such as fishing (Bianchi, 2000;Yemane et al, 2005), pollution and engineering (Penczak, 1999). In undisturbed states, the community was supposed to be dominated by k selection species (slow-growing, large body size, long lifespan and late-maturing), but with increasing disturbance, the system was gradually dominated by r selection species with the attributes of fast-growing, small body size and short lifespan.…”