New Zealand's Southland's four major rivers are famous as brown trout fisheries, especially in the upper and middle sections, but in this episode Anto Hall and Mike Wilkinson are heading to the estuaries, to fish the annual smelt run. These baitfish return to the rivers in huge numbers to spawn, and the trout don't miss out on this feast. This makes for some explosive fishing action, displaying the fish's true predatory nature.