The commercial scallop (Pecten fumatus) fisheries in south-eastern Australia have long been characterised as boom-and-bust (Tracey & Lyle 2010). While historic overfishing has contributed to this (Young 1989), unpredictable cycles of alternating abundance and large-scale die-off characterise the species, particularly in the eastern portion of the region. For instance, there have been five sudden die-offs on the eastern side of the Tasmanian fishery (TSF) and Commonwealth fishery (BSCZSF) combined since 2005. Whereas, since most recently being fished in 2014, the scallop beds in the King Island region of the BSCZSF have been harvested each year due to predictable and constant recruitment and scallop conditioning.
The relative difference in predictability between the regions likely lie with the changing nature of the EAC on the east coast bringing warm, nutrient-poor water to the east coast and the Leeuwin current bringing cold nutrient-rich water to the west coast, with these differences likely to be further exacerbated due to climate change. A case in point is the Tasmanian fishery, which after being closed for five years due to the stocks being depleted, opened in 2021 off Babel Island (east) only to find the bed had died-off only a few months post-preseason surveying. A sudden influx of warm water was likely the cause of the die-off, with beds in the eastern portion of both the BSCZSF and the Victorian scallop fishery (OSF) simultaneously suffering a significant loss of condition but not death (Semmens unpublished). In 2022, again a major die-off has impacted the TSF, with beds at White Rock (east) found to be dying off upon opening in late June. The unpredictability of these die-offs confounds management decisions, as a lack of understanding into the drivers of die-offs means that even if beds with commercially significant biomass are surveyed and opened, they may be lost before fishing begins. There is a clear need to understand these die-offs, determine if they can be predicted and adapt management such that it can be reactive and is tailored to the region in which the bed occurs (e.g., east vs west). Fitting management strategies to the fishing region also makes sense biologically, with the east and west portions of the species’ distribution displaying different life history features (e.g., spawning and settlement times, growth rates, etc; Semmens et al. 2019) and this may be a contributing factor to die-offs.
This project will use a collaborative industry/management/research approach to investigate the factors causing mass die-off of scallop beds, characterising the impacts of stressors including fishery practices, such as the use of tumblers, survey method (e.g., dredge vs video) and environmental factors, such as location of beds, sea temperatures (considering both absolute temperature and rate of change) and food availability, and assessing them in a framework that fits management practices to the relative risk of loss of fishable stock. Developing an understanding of the factors driving mortalities will also enable evaluation of existing data capture capabilities to identify whether potentially harmful conditions can be identified before beds are lost. Where deficiencies are identified, new data collection techniques will be evaluated, including video surveying of closed regions (both permanent, e.g., MPAs, and fishery closures) to allow more flexibility in decision making around when an area should be fished. The outcome of this research will provide the evidence needed to develop a decision-making framework that will enhance the rapid response capabilities of management of scallop fisheries in the future, but also ensure that they fit the changing environment and region within which the stocks sit, improving the sustainability of this vulnerable industry.

The Tasmanian Commercial Dive Fishery (TCDF) is transitioning from a fishery with minimal controls on catch with no annual assessment, to a carefully managed fishery with annual robust fishery assessments. Two of the three key species Shortspined Sea Urchin (Heliocidaris erythrogramma) and Wavy Periwinkle (Lunella undulata), have similar life histories to abalone, while the third – Longspined Sea Urchin (Centrostephanus rodgersii), has an intermediate life history. All three species have a time-series of catch and effort data, and some level of biological data, and thus don’t fall into the class of data-poor fisheries. However, just as for haliotid fisheries, all the complexities identified by Orensanz et al (1995) for S-Fisheries (small-scale, spatial structured, sedentary target species) apply here, meaning that integrated assessment models assuming Dynamic Pool should not be used. Instead, Empirical Harvest Strategies based on standardised catch rates are the most appropriate approach to underpin annual assessments and determination of stock status. Given the similarities between these species and abalone (life history, habitat, fishing practices), it is desirable to utilise the considerable investment in research on data collection and assessment methods in that fishery. This project will therefore attempt to adopt and adapt ground-breaking research on Abalone, including utilization of high-resolution spatial data from GPS and depth data loggers, as a short-cut to worlds best practices in the TCDF.

Consideration of stock status for the TCDF species to date has been on the basis of graphical inspection of crude catch rates. As Empirical Harvest Strategies rely heavily on robust catch rate metrics, adopting a model for standardizing catch rates is a critical step for the TCDF fisheries. While there are a diversity of philosophies around catch rate standardization, choosing the optimal standardization model is only part of the challenge. The key challenge for the three key TCDF species are that catch is spatially and temporally fragmented. Both urchin species are highly seasonal, and Shortspined Sea Urchin and Wavy Periwinkle fisheries are spatially discrete with a few high catch areas, and a larger proportion of spatially and temporally disparate low productivity fishing grounds. Similarly, catch is largely landed by a small number of highly active participants, with a larger number of primarily part-time fisheries. This fragmented nature (time, space, people) of the dataset creates challenges for applying standardisation models to establish a robust time-series. Primarily this manifests as highly volatile time-series, that can flip above or below Reference Points over consecutive years. In some fisheries, this challenge is addressed by fitting a multi-year running mean through catch rates, essentially smoothing the trend. While this might have the desired effect of removing hyper-variability in catch rates, it will slow action required as the stocks decline, as well slow catch increases under rebuilding. Preferably, we will instead use environmental variables, quantify fisher experience and make use of fine-scale location data on fishing activity in our catch rate standardization methods.

An additional complication in the Tasmanian Commercial Dive fishery is mixed species fishing. This feature is also present in a sub-set of assessment areas within the Tasmanian Abalone fishery where H. rubra and H. laevigata co-occur, as well as in the Central and Western Zone abalone fisheries in South Australia. Developing a clear catch rate signal in these mixed species fisheries is challenging and an optimal solution has not yet been found, although spatial and depth information most likely will enable differentiation of fishing grounds across species. Through this project we will engage with South Australia specifically to collaborate on logger based approaches to improve assessment of mixed species fishing regions.

As with abalone fisheries, TCDA divers are able to modify their in-water fishing behaviour (swim faster and further) to achieve desired daily catches which has the effect of masking decline in abundance. However, this is not the only form of hyperstability expected in the TCDA fisheries. The highly fragmented stock structure and diver experience are likely to interact to create a second form of hyperstability more common in emerging fisheries, and that is serial depletion, or at least serial fishing of discrete patches. This latter form of hyperstability occurs when more experienced divers with greater knowledge are able to move when more accessible patches become over-exploited.

Local scale depletion is addressed by the establishment of size limits for Wavy Periwinkle and the Shortspined Sea Urchin. Robust size limits have recently been adjusted for Wavy Periwinkle (increase from 30 to 45 mm; FRDC 2011-024) and Shortspined Sea Urchin (increase from 60 to 75 mm FRDC 2017-033); No size limit is intended to be set for range-extending Longspined Sea Urchin, as the objective in this fishery continues to be to achieve localised depletion.

From the 2022/2023 season diver GPS and depth loggers will be compulsory to collect detailed spatial information about the fishery. Several key divers have been using dataloggers for the past eight years, providing a valuable time-series from the more experienced TCDF fishers. The availability of such data creates a new opportunity and leads to the key aim of this project, to develop methodologies and tools to incorporate the detailed spatial catch data into formal stock assessment and harvest strategies. In doing so, methods to facilitate the accurate standardisation of historical logbook data to facilitate transition into logger data to preserving the continuum of the time series is required. The development of reliable fishery dependent assessment metrics is essential in these smaller fisheries where there is no scope for cost-prohibitive fishery independent surveys.

In summary, this project is needed to develop strategies to produce robust standardized catch rate trends, that can be utilized in an Empirical Harvest Strategy. Spatial based Catch Per Unit Effort (CPUE) measures and spatial performance indicators and indices of hyperstability will be critical to facilitate the creation of appropriate stock assessment and harvest strategies for small scale dive fisheries, including smaller haliotid fisheries.

Project need from the call for applications (summarised):
Across the globe, First Nations and Indigenous Peoples have been and continue to negotiate recognition of their fishing rights and for their knowledge and interests to be directly accounted for in intersectoral allocation and fisheries management. Recognition of Indigenous fishing rights into current fisheries management, in resource sharing policies and allocation is in various stages of development across Australia's states, territories, and the Commonwealth. At the same time and at the more operational level, harvest strategies are being developed which include Indigenous and cultural fishing, but greater guidance is required regarding harvest strategy settings which recognise the importance and account for the cultural, social, and economic impacts on local abundance and availability of fish stocks for Traditional Owners and local Indigenous communities. However, there is a gap in knowledge of possible approaches to address this, and the ability to generalise is still needed. To this end, this project will undertake a review of approaches and policies developed internationally and domestically for incorporating Indigenous Rights, knowledge, practices and catch (Cultural-Customary and Cultural-Commercial) into resource sharing and harvest strategy frameworks. It will identify possible approaches available for Australian fisheries management agencies, Traditional Owners, and Indigenous communities, while recognising the different historical, cultural, and legal contexts of different jurisdictions.

Summary of UTS approach:
The UTS project team will meet this need through convening a highly experienced team of Indigenous and non-Indigenous researchers, each with relevant expertise and experience in Australia and internationally. The existing work of the research team on multiple Indigenous harvest strategies and Indigenous led natural resource management initiatives will be drawn on to provide a sound basis for a survey of relevant examples. Importantly, senior Indigenous researchers guiding the project already have strong international networks and up to date knowledge on relevant international developments, that will be mobilised to guide this work, and to broker the knowledge and linkages of a range of expert participants into the project.

The research design for this proposal includes a thorough desktop study of the field, including mobilisation of UTS developed databases of specific relevance to the topic area, as well as detailed consultation with Australian and international experts throughout the process. The project will also involve co-production of knowledge with relevant experts/end users, through research activities designed to identify the parameters that influence what approaches are 'fit-for-purpose' in Australian settings.

Commercial in confidence. To know more about this project please contact FRDC.