Riparian land use and accessibility to fishers influence size class composition and habitat use by longfin eels in a New Zealand river

Abstract

Fyke nets were used to sample longfin eels Anguilla die.enbachii in fourth order stream sites with contrasting riparian land use (native tussock, exotic pasture and pasture plus willows Salix spp.) in Lee Stream, a tributary of the Taieri River, New Zealand. Total lengths (LT) of longfin eels from locations inaccessible to eel fishers were normally distributed whereas those from accessible locations had a non‐normal, positively skewed distribution. Mean LT and body condition were higher in inaccessible than accessible sites, consistent with considerable fishing exploitation in the latter. Mean LT of the fish was greatest in pasture, intermediate in willow and smallest in tussock sites. Larger longfin eels (≥535 mm) were associated with a riffle‐type habitat consisting of shallow, faster‐flowing water with coarse, variable sediment and were taken farther from cover. In contrast, smaller longfin eels were associated with a pool‐type habitat consisting of slower‐flowing, deeper water, with fine, homogenous sediment and were captured closer to cover. This pattern of habitat use differed from some previous reports and probably reflects differences in methodology: fyke nets set over 48 h to sample actively moving longfin eels compared to daytime electric fishing, which samples longfin eels that are more likely to be at rest.