Experience with Management of Orange Roughy (Hoplostethus atlanticus) in New Zealand Waters, and the Effects of Commercial Fishing on Stocks over the Period 1980–1993

Abstract

Orange roughy (Hoplostethus atlanticus) occurs throughout New Zealand waters at depths of 700m to 1500m. Commercial fishing dates from 1980 with the discovery of large concentrations of spawning fish on the Chatham Rise. Since then, further spawning and feeding grounds have been identified, and fishing occurs in 8 separate regions of the New Zealand EEZ. Catches increased rapidly, and throughout much of the 1980’s the total reported catch was 40–50 000 tonnes per year. This made orange roughy New Zealand’s single most valuable fish species.

Management of the fishery has been based on a system of regional Total Allowable Catches (TACs), with the quota allocated amongst fishermen, rather than on an open competitive basis. TACs were initially set using very limited research data. It has since been recognised that orange roughy are slow growing and long lived, with low fecundity and low productivity. Combined with improved estimates of relative abundance from time series of surveys, it is clear that for several of the stocks the initial TACs were set at levels considerably higher than would be sustainable in the long term. Sustainable yields are around 1 to 2% of virgin biomass, with the “optimal’ stock size at about 30% of virgin. Several stocks have been overexploited, and reduced to levels of 15–20% of virgin biomass. Associated with such a decline in biomass on the north Chatham Rise and the Challenger Plateau were contractions in the areas of high density, and the apparent fishing-out of some aggregations. However, no marked biological changes have been observed. The size structure of the populations has not altered, and the location and timing of spawning has remained constant between years.

It is likely that orange roughy populations take a long time to recover from heavy fishing, yet they can be reduced quickly to low levels by commercial operations. The New Zealand experience shows that careful and controlled development of the fishery is required from the outset. Research should occur in advance of substantial commercial fishing effort, so that baseline data on distribution, abundance and biology are collected. This would avoid a number of management problems later on.