A substantial rise in future demand for seafood is forecast with ocean fishery productivity projected to decline by up to 50% in some fisheries due to ecological disruptions. A key challenge therefore will be maintaining fishery productivity. Shark Bay and the Abrolhos Islands scallop fisheries are prime examples - following the extreme marine heat wave of 2011 lost income from these fisheries is estimated at $53 million GVP, or $155 million including multipliers.

The integration of aquaculture and wild fisheries is becoming increasingly recognised as a tool for enhancing fishery productivity (Taylor et al, 2017). Re-stocking and stock enhancement following recruitment failure could lead to faster fishery recoveries, and also be used to supplement natural recruitment to provide a more consistent and higher yield harvest from year to year. Development of supply chains for scallops into domestic and overseas high-value live markets requires consistent supply. Due to climatic variability and highly variable natural recruitment there is an urgent need to investigate scallop stock enhancement using hatchery-produced juveniles in WA.

A key element for success will be the development of reliable, efficient and scalable seed production systems, which will be based on previous research findings integrated novel, contemporary shellfish production technology. During this project, 16 million cultured scallop spat are planned to be released. The annual yield of scallops from the Rottnest SWF Zone A is 25 to 50 tonnes (whole scallop weight), or approximately 250,000 - 500,000 scallops assuming an average weight of 0.100 kg/whole scallop. This Project aims to release on average 8 million spat each year of the Project (600,000, 1,500,000 and 6,000,000 of 10mm, 5mm and 2mm spat respectively), which could contribute 45,000 hatchery-produced scallops to the catch each year assuming 2.50%, 1.00% and 0.25% of 10mm, 5mm and 2mm spat released respectively were captured, increasing yield by 8.3 – 16.6 % in the annual production, demonstrating the feasibility of scallop stock enhancement.

Critical to the Harvest Strategy for the Qld Mud Crab Fishery are processes for monitoring and assessing fishery performance. Currently, the empirical and estimated indicators for this fishery are based on non-validated harvest and effort. Proposed fishery reforms (i.e., prior reporting of landings and 'market' tagging of harvested crabs) should improve harvest data reliability. Qld GMC are effectively a data-limited species because they cannot be reliably aged, associated effort data is incomplete and potting is a passive fishing technique. Commercial CPUE may not represent changes in population abundance due to variable catchability, hyper-stability and serial depletion. Additionally, there is no index of female abundance nor a male:female ratio to inform spawning-recruitment relationships. It is generally assumed that conservative management of GMC ensures their sustainability. However, evidence from the Northern Territory Western Gulf of Carpentaria suggests that GMC are vulnerable to environmental events (drought + heat = 2015 cohort failure). Gaining a rudimentary understanding of critical aspects of the GMC life cycle in Qld would be prudent (i.e., female abundance, spawning vicinities).

A Total Allowable Catch (TAC) is a key aspect of reform to Qld fisheries. The initial TACs for Qld GMC were informed by a modified catch-MSY analysis (Northrop et al., 2019). Catch-MSY is widely applied in Australian fisheries to data-limited species (FRDC 2017/102). The assessment was performed at large spatial scales (East Coast and Gulf). However, this fails to capture regional variability in spawning-recruitment processes that impact on harvestable biomass e.g., larval dispersal due to oceanic circulation patterns and survival of juvenile crabs due to regional rainfall, flow, temperature, and sea level variations. The proposed research is needed (in the short-term) to gather appropriate quantitative biological information and to develop (for the long-term) a means to cost-effectively monitor Qld GMC populations to support a data-moderate stock assessment approach. The research also aims to address some of the critical knowledge gaps in GMC life history that have been unresolved for over 40 yrs.

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Recently, the risks resulting from not accounting for variability in productivity have become translated into potential risks associated with environmentally driven trends in recruitment, particularly the risk created by ongoing declines in recruitment (and/or growth) driven by climate-change induced trends in water temperature, weather and current patterns.

A number of southeast Australia fish stocks have failed to 'recover' following substantial reductions in catch and effort, and a number of research projects have concluded that some of these have undergone an environmentally-driven reduction in productivity. A productivity shift has already been demonstrated for Eastern Jackass Morwong, with the stock-recruit relationship and reference points being adjusted to reflect this change. Ecosystem and climate-change modelling have predicted increasing likelihood of similar changes in productivity for a number of Australian fish stocks.

Current harvest strategies assume either equilibrium or some average B0, and associated target (B48) and limit (B20) reference points. Use of equilibrium B0-based reference points and harvest strategies do not correctly reflect the natural dynamics of stocks where productivity changes. This can lead to sub-optimal management, either over-utilising a reduced productivity stock or under-utilising an increased productivity stock. In contrast, reference points based on some proportion of naturally variable unfished biomass (Bunfished or dynamic B0) will fluctuate to follow environmentally-driven productivity changes. Dynamic reference points have been evaluated and adopted for a number of international fisheries.

The need to adapt stock assessment methods and harvest strategies to explicitly and justifiably account for shifts in productivity has been recognised by the AFMA Resource Assessment Group for the Southern and Eastern Scalefish and Shark Fishery (SESSF), not least as a result of clearly evident declines in biomass (Jackass Morwong, Redfish) or recruitment (Silver Warehou) that cannot be attributed to fishing under current productivity assumptions.