The aim of this research is to apply measured nutrient excretion rates to estimate the potential for catfish to contribute to lake nutrient budgets for lakes Rotorua and Rotoiti. We have assumed that brown bullhead catfish will primarily occupy depths of ≤6m in summer, when water temperatures are highest. This assumption is based on acoustic tracking of catfish in Lake Taupo. Lake Rotorua has about 23.5 km2 of habitat ≤6m deep (29.1% of its area) that is spread almost completely around the lake, whereas Lake Rotoiti has about 6.7 km2 of habitat ≤6m deep (19.9% of its area). The shallow areas of Lake Rotoiti are mainly at the western end (Okere Arm, Okawa Bay, and Te Weta Bay) with only a few shallow bays in the eastern basin (Te Karaka Bay, Te Arero Bay, and Wharetata Bay).