Publication Abstract

Estimating habitat carrying capacity and the spatio-temporal distribution of adult sole in the eastern English Channel

P. D. Eastwood, S. I. Rogers, and G. J. Meaden

The spatial range and number of habitats occupied by freshwater and marine fish populations is often found to be greatest at times of high population abundance. We examined whether range contraction and expansion over time is displayed by adult sole in the eastern English Channel during summer feeding, by constructing empirical models that combine time-series catch data from fisheries-independent surveys with spatially explicit environmental data. The models were based on quantile regression estimates of the upper bounds of adult sole catch densities, which in turn yielded estimates of habitat carrying capacity. Two models were constructed: one to estimate the limiting effect of a varying thermal regime on habitat carrying capacity, and a second to estimate habitat selection under different levels of population abundance. The models predicted reduced catch densities at higher water column temperatures, and higher catch densities in shallow-water sandy habitats compared to deeper-water gravelly habitats during times of high population abundance. The spatial range of the population also increased with abundance, but this increase was not consistent among all age groups. We conclude that there is little evidence to suggest that the carrying capacity of the inshore sandy habitats was reached over the time period for which catch data was available. In addition, given the levels of population abundance encountered, habitat selection by sole appears to be largely density-independent, in that local densities were predicted to increase at a relatively consistent rate over preferred habitats in line with an increase in the total population abundance. These findings have important implications for the site-specificity of sole habitats in the eastern English Channel.

Reference:

P. D. Eastwood, S. I. Rogers, and G. J. Meaden. 2003. Estimating habitat carrying capacity and the spatio-temporal distribution of adult sole in the eastern English Channel. ICES CM 2003/Q:10. 15pp.