This report involves the ‘Western Victorian Snapper (Chrysophrys auratus) Stock’ (WVSS) which supports arguably the most important marine fin-fish fishery for Victoria. While the majority of the harvest is by Victorian fisheries, this stock is a straddling stock shared with South Australia. This report describes a largely scientific project conducted by the Victorian Fisheries Authority (VFA) in collaboration with fisheries modelling scientists from MEZO Research. The project was initiated in 2013 to address concerns about uncertainty of management risks associated with increased fishing pressure across sectors and jurisdictions, and the inability to track recreational harvest trends and adequately incorporate recreational fishing pressure into stock assessment and management.
The project developed approaches using remote internet protocol (IP) cameras at boat ramps to monitor recreational boat fishing effort in the main Victorian fishing areas of Port Phillip Bay and Western Port Bay, and to integrate the fishing effort data with recreational survey (boat ramp creel survey) data on Snapper catch rates and length compositions to create a ‘harvest index’ to track Snapper harvest trends over time. The boat ramp camera trial explored two monitoring approaches; time lapse image capture, where an image of the ramp is recorded every two minutes and sub-sampling routines are applied to estimate total effort, and an ‘activity sensor’ approach, where images are recorded only when certain types of activity are detected (i.e. boat/vehicle movement) within a specified activity area.
A new ‘Management Strategy Evaluation (MSE)’ modelling tool, ‘SnapMSE’, utilising the free population modelling framework, ‘Stock Synthesis’, was created to evaluate management risks and trade-offs associated with different levels of fishing mortality in relation to specified objectives. The analytical tools developed utilised ‘R’, an open source software environment for statistical computing and graphics that is commonly used by scientist worldwide, and have been created so they are accessible to fisheries scientist with moderate experience using R. The MOU agreement between the VFA and PIRSA was developed via numerous phone meetings and a drafting workshop. An operational framework was developed for guiding implementation of the MOU.
The project demonstrated that IP cameras can be a cost-effective approach for monitoring trends in recreational boat fishing effort, and when combined with creel survey data can be used to monitor trends in targeted Snapper fishing effort, harvest from individual access points (boat ramps) and to derive a recreational ‘harvest index’ for monitoring trends in recreational Snapper harvest across the fishery. The first MSE model framework for a Victorian fin-fish fishery was successfully developed. The evaluation of alternative harvest control rules under high, average and low recruitment regimes, showed that maintaining the annual exploitation rate at around 10-15%, similar to the status quo, was likely acceptable for meeting the trial management objectives applied in this study over the long-term.
The monitoring, modelling and other analytical tools developed will improve the assessment of overfishing risk on the WVSS and the capacity of managers, policy makers and stakeholders to work together on a planned and informed approach for managing fishing mortality risks, including development of operational objectives.
