Getting a better grip on eels
Native freshwater eels. (Photo: Don Jellyman, NIWA)
Native freshwater eels support important commercial, recreational, and Māori customary fisheries throughout NewZealand. NIWA is the leading provider of scientific research and advice on eels to the Ministry of Fisheries.
Our analysis of commercial fishery data shows that longfin eel stocks have declined since the 1990s and mature females (crucial for breeding) are now very scarce in commercially fished rivers.
Eel abundance and biomass data comes mostly from commercially fished rivers. We have used new spatialmodelling techniques to predict eel abundance throughout New Zealand’s waterways, based on river characteristics and flow, and knowledge of eel habitat preferences. We’ve also used these techniques to assess the value of national parks as eel reserves and to predict the effects of changes in river flow and land use. Field studies indicate that longfins require instream and bank cover for daytime shelter, riffles and runs for nocturnal feeding, and are more abundant in higher river flows.
Information on longfin spatial distribution is key to assessing the current and future status of stocks. We recently piloted the world’s first integrated population model for eels, incorporating spatial distribution data into our CASAL model for the Southland longfin fishery. NIWA’s models are now being considered as a means of assessing management options for habitat protection and alternative harvest strategies.