Recent surveys have shown crayfish numbers declining inside and outside marine reserves at Leigh and Tawharanui.
Dr Nick Shears, a marine biologist at the Leigh Marine Laboratory, says crayfish numbers in the reserves are down a further 25 percent from 2014.
Numbers outside the reserve are the lowest they have been since monitoring began in the 1990s. Biomass is estimated to be <5 percent of unfished levels. Earlier this year scientists released figures showing crayfish numbers inside Goat island reserve were lower than when it was established in 1975 and less than a quarter of their 1990s peak. Dr Shears attributes the decline to fishing pressure on reserve boundaries, a lack of recruitment and high fishing pressure in the CRA2 fishery. He has advocated a case for extending the offshore boundary of the reserves to protect resident animals throughout their home range.