Smelt & Fry (Southern)

Introduced to Lake Taupo in 1934 purely as trout food, and it worked rather better than anyone probably expected — this smelt is now self-sustaining and the single biggest thing keeping Taupo's trout the fish they are. It spawns in the shallows come spring, and that's the moment that matters: dense schools push into the margins and up into the river mouths to do it, and big trout follow them in, holding and feeding right at the confluence where lake meets stream. This is what Taupo anglers mean by "smelting," and the Grey Ghost — tied specifically for this fish — is the genuine local answer, though a Muddler covers smelt and bully both if that's what's in the box. Spring into early summer at the stream mouths is the sharpest window; smelt-following trout will also take a fry pattern out in open water through the rest of the season, just with less certainty about where to start looking.

• New ZealandPresent
• PatagoniaPresent

The New Zealand smelt (Retropinna retropinna) is a small fish endemic to New Zealand's waterways, an elongated silver-green fish with clear fins, typically 8 to 13cm long, identifiable by its adipose fin and characteristic cucumber-like odour. It inhabits shallow estuaries and rivers throughout the North Island, with less frequent populations in the South Island, and is a significant food source for North Island trout populations.