Amorous roughy respond to fishing

A scientific paper (Pitman, Haddy and Kloser) has been released assessing the impact of commercial fishing on the reproductive capacity (fecundity) of orange roughy. Data from when exploitation began (1987–1992) is compared with current observations from the eastern Tasmanian stock. Findings show that fecundity is negatively related to stock size, meaning that as the population of orange roughy declined fecundity per individual increased 41,145 (± 1,363) eggs in 1992 to 59,236 (± 1,047) eggs in 2010. The fecundity per fish has increased by 73%. Modelling this increase based on the 2006 stock assessment showed that the female spawning stock biomass was at 19% of virgin levels, whereas the total reproductive potential was markedly higher and estimated to be at 32% of virgin levels. The biological mechanisms of this compensatory effect were also investigated and showed fecundity was not related to ovarian atresia levels but was positively related to body condition and liver condition. The implications of these findings for stock recovery and management suggest that the stock is in a better position to recover from over-exploitation than would be expected if only spawning stock biomass is considered. The full report can be read here.