Science Centres: Fisheries

Population declines of toheroa in the 1960s resulted in prohibition of harvesting in 1981, except for Maori customary take and occasional one-day recreational seasons. NIWA has been active in monitoring toheroa populations in their last remaining strongholds, in Northland and Southland, for the Ministry of Fisheries.

Surveys at Oreti and Bluecliffs Beaches in Southland have shown a steady decline of toheroa over the last 20 years, particularly at Bluecliffs, with numbers only a small fraction of those in the 1960s. Populations fluctuate greatly because of variable recruitment and mass mortality events, but the sustained low abundance is somewhat mysterious.

A study at Bluecliffs Beach, commissioned by Meridian Energy, showed that the beach is eroding, with the loss of fine sand substrate. This is almost certainly contributing to toheroa decline at this beach.

This month, NIWA will conduct a repeat survey of toheroa on Ninety Mile Beach, last surveyed in 1999.