Prevalence of data-limited fisheries in Australia and options to improve their management
Creators: name: Hill, NJ
Publisher: name: University Of Tasmania
Year: 2023

description: The majority of the world‚ÄövÑv¥s fisheries lack the data and/or management capacity (e.g. personnel, funding) to implement robust fisheries management. Where this is the case, fisheries are more likely to perform poorly in terms of sustainability. Robust fisheries management has been found to be instrumental in reducing fishing mortality and allowing stocks to recover, and includes attributes such as analytical stock assessments, the ability to control fishing pressure, and comprehensive compliance programs. With the prevalence of overfished stocks increasing globally, and external threats such as climate change and habitat degradation increasing, greater implementation of robust management should be a key priority for fisheries administrations. However, few fisheries administrations monitor or assess the quality of management in place for stocks. The intent of this thesis was twofold. First was to assess the status of fisheries management in Australia and evaluate Australia‚ÄövÑv¥s progress in implementing robust management at a stock level (Chapters 2 and 3). The second aim involved testing and exploring ways to improve the management of data- and capacity-limited fisheries (Chapters 4 and 5). The outcomes of this thesis provide a benchmark for the current performance of Australia‚ÄövÑv¥s fisheries management and identifies improved management approaches for those stocks recognised as data- and capacity-limited. For the first aim, a comprehensive literature search was undertaken, compiling relevant fisheries management information for over 600 stocks across Australia‚ÄövÑv¥s eight independent jurisdictions. This information was compiled to assess the performance of Australia‚ÄövÑv¥s fisheries in managing its stocks to target biomass objectives (Chapter 2), and its progress in implementing robust management at a stock level (Chapter 3). The outcomes of this review found that although most of Australia‚ÄövÑv¥s stocks are reported as sustainable, only 33% are at target biomass levels, with 28% above and 39% below, highlighting lost ecological, economic, and social potential. Moreover, most stocks do not possess robust management across the three attributes explored: stock assessments, harvest strategies, and catch/effort restrictions. While progress has been made in reducing the number of overfished stocks in Australia and elsewhere via improved fisheries management, this analysis highlights that even in a developed nation such as Australia, robust management at the stock level remains limited. Given the link between robust management and sustainable outcomes, jurisdictions should consider assessing the management in place for stocks when determining performance. For the second part of this thesis (Chapters 4 and 5), simulation modelling was undertaken across three commercially important species to: 1) identify which empirical performance indicators best monitor stock biomass and, 2) determine the effect of management interval (i.e. time between stock assessment and management updates) on the performance of harvest strategies ranging from data-rich to data-limited. The three species examined were Australian sardine (Sardinops sagax), tiger flathead (Platycephalus richardsoni), and jackass morwong (Nemadactylus macropterus). These species were selected as they span a range of life history characteristics and longevities, and data on their life history characteristics was well documented. Management Strategy Evaluation (MSE), a simulation modelling technique, was used to simulate the three species and various fishing scenarios to generate data and produce outputs for each of these objectives. In total, 11 empirical performance indicators (e.g. catch per-unit effort (CPUE), mean length, % of fish above age at maturity) were tested using a set of five criteria (Change ratio, Linearity, Reliability, Robustness, Cost) to determine their efficacy in monitoring stock biomass. No single empirical performance indicator (PI) performed well across the three species or set of criteria, however proportion-based PIs (e.g. % of fish above length at maturity) were found to monitor biomass best for short-lived species and mean/median-based PIs (e.g. mean age) for longer-lived species. It was also found that larger PI sample sizes were needed to effectively monitor longer-lived species. These results will help to identify those empirical PIs that best monitor biomass across different species, but also highlight the limitations and trade-offs present in selecting an appropriate PI. For the second part of the analysis (Chapter 5), it was found that harvest strategy performance degraded as management interval (i.e. time between updates) increased, with the risk of stocks becoming overfished increasing and yield decreasing. However, multi-year harvest strategies were able to deliver comparative performance to their annual counterparts if appropriate precautionary buffers were incorporated, providing an opportunity to reduce costs. Results of this analysis will help to develop effective harvest strategies for fisheries, particularly those that are data- and capacity-limited. This thesis highlights the size of the challenge faced by Australia‚ÄövÑv¥s fisheries administrations in improving management going forward, but also identifies potential solutions. Outcomes XVII from the first part of this thesis represent one of the most comprehensive national level assessments of fisheries management to date. This analysis provides a benchmark for fisheries administrations on their current performance, identifies key management attributes that are inadequate at a stock level, and highlights approaches that have been successfully adopted elsewhere. The second part of this thesis can act as a guide in identifying management attributes (e.g. data to collect, stock assessment method) that are most likely to achieve improved outcomes for species ranging from short- to long-lived, and for fisheries from data-rich to data-limited. Globally, several fisheries administrations have made progress in reducing the prevalence of overfishing in recent times. Much of this progress has been attributed to the implementation of robust management. If sustainable outcomes are to be achieved, fisheries administrations must look to increase the implementation of robust management across stocks and begin to track its uptake over time to better assess their performance.