Assessment of the Australian deep-water royal red prawn stock using commercial catch and effort data

Abstract

Trends in standardized catch-per-unit effort (CPUE) were analyzed to assess the state of the deep-water royal red prawn ( Haliporoides sibogae) stock exploited off eastern Australia since the mid 1970s. Two aspects of uncertainty in using CPUE as an index of abundance were recognized. First, it was difficult to determine accurately the impact of the fishery on the prawn abundance because all the biological and/or technical factors influencing the CPUE could not be identified and quantified. Analyses of covariance showed that differences in vessel characteristics, period and location of fishing explained only part (33.9%) of the variability of CPUE. The second problem was related to the fact that the fishery exploited only part of the stock, and therefore, trends in CPUE reflected only trends in abundance for that part of the stock. The fishery was concentrated within 1° latitude (34°00′S–35°00′S), from 400 to 500 m deep, and declined markedly during winter months each year. These fishing patterns were more related to economic motivations than to the abundance of prawns which were apparently available year round and over a wider geographic range. Despite its limitations, analysis of CPUE provided useful information for a first appraisal of the state of the stock. The stability of annual landings (300–350 t) and standardized CPUE (300–400 kg per boat-day) since the early years of the fishery indicates that the royal red prawn stock is in a steady state under the current level of fishing effort.