Spatial and temporal trends in unexploited yellow eel stocks in two shallow lakes and associated streams

Mean yellow eel density and biomass in two adjacent shallow (mean depth c 1.5 m) lochs varied significantly between years. Temporal patterns of density, biomass and size were similar in both soft and rocky substrata in the lochs, although eels were consistently smaller in the latter habitat. In both substrata, average length and weight showed a non-significant inverse relationship with density, supporting the hypothesis of density-dependent regulation of the yellow eel population. Fyke net catches were size selective, catching no eels <30 cm long, and providing length-frequency information for silver eels. Fyke net catch per unit effort (CPUE) declined consistently each autumn but specific annual trends were different. When eel density increased, fyke net CPUE declined substantially. (C) 1999 The Fisheries Society of the British Isles.