Influence on management advice of fishers acoustics - 10 year review of blue grenadier monitoring

An industry-based acoustic observation program was developed and applied to the austral winter spawning blue grenadier fishery from 2002. Blue grenadier has the highest Total Allowable Catch (TAC) among fished stocks of Australia’s Southern and Eastern Scalefish and Shark Fishery (SESSF). High recruitment variability and stock size uncertainty motivated development of an industry-based cost-effective acoustic monitoring program in 2002 to optimise harvest while ensuring sustainability. The development of industry-based acoustic methods resulted in “routine” surveying being carried out by skippers on industry vessels since 2006. During this time an incentive based management approach was introduced by allocation of research quota to assist in the long term implementation and delivery of the biomass indicator. The survey strategy of the industry-based method differed significantly from chartered vessel based surveys; fishers were tasked with recording the maximum biomass during the spawning season. This monitoring method shifted the “burden of proof” to industry and reinforced the need for both local and broad scale surveys to estimate the stock size. Survey results have been used for management advice by reducing uncertainty in stock size, inclusion in the stock assessment model and informing spatial planning for the region. An associated outcome was the confidence by industry that fishers’ observations of the spawning biomass were recorded and used in the stock assessment process for management of the fishery.