What causes the high interannual variability of flatfish (Rhombosolea spp.) in Lake Ellesmere?

Abstract

Lake Ellesmere, Canterbury, a large coastal lake is mechanically opened to the sea at predetermined water levels. The lake maintains important customary and commercial eel (Anguilla spp.) and flatfish (Rhombosolea spp.) fisheries, although the harvest of flatfish varies considerably between years. The three main flatfish species (black flounders Rhombosolea retiaria, sand flounders R. plebia and yellowbelly flounders R. leporina) recruit in spring, grow rapidly within the lake, and reach the minimum commercial size within two or three years. Maturing fish endeavour to leave the lake to spawn at sea during summer and autumn. There is a weak association between commercial catches and lake openings lagged by two years, but strong associations between catches in the lake and in the Canterbury Bight. The high interannual variability in abundance partly reflects timing and duration of lake openings, the opportunity of maturing fish to emigrate to sea, and the strength of regional recruitment.