South-east Australian waters are recognised as ocean warming hotspots and overall, Australian waters have warmed faster than the global average (Hobday and Pecl 2013, IPCC 2019). Key components of the productivity of marine fish (growth, maturity, and recruitment) are expected to be changing in response to shifts in climate and it is entirely possible that there have been changes in fundamental productivity parameters for Australian stocks.
The regularity with which the biological parameters that are used in stock assessments are evaluated and updated varies considerably among the species that are targeted in Commonwealth Fisheries. Assessment of changes in these parameters is limited largely to sensitivity analyses consisting of exploring alternate time-invariant values of natural mortality, maturity and stock recruitment steepness at values close to those used in the base-case assessment and generally agreed upon as within acceptable ranges of values. Recently an evaluation of the provenance of the biological parameters used in stock assessments found that species from the SESSF contained the largest number of parameters where provenance could not be ascertained from the literature and that SESSF species comprised over 50% of those species where biological parameters were determined to be more than 20 years old (FRDC project 2019-010, Evans et al. 2022). When plausible changes to biological parameters (such as those that might occur under environmental change) were explored quite substantial changes in biomass estimates for key target species occurs. This means that parameter mis-specification, such as due to relying on older parameter estimates that encode predator-prey and other ecosystem processes from a system state that has since changed, could be a real issue for assessments in the SESSF.
The reliance of current assessments on what is likely to be out-of-date information leads to considerable uncertainty, which cannot be easily quantified that then propagates into management decisions. Without an understanding of changes in biological parameters and how these changes might impact assessments, it is difficult (if not impossible) to evaluate whether current management measures are ensuring sustainability. Overall, the project recommended that updating parameters in stock assessments, modifying base cases, or more heavily drawing on results from sensitivity analysis in discussion of stock assessment results would be strongly advisable, especially in regions where large environmental shifts are known to be occurring, such as the SESSF.
The RV Investigator voyages to be conducted in 2023 and 2024 under the CSIRO led SEA-MES project provide a unique opportunity to access relevant biological samples that could be used to update the biological parameters identified in FRDC Project 2019-010 as a high priority (age, growth, reproduction, stock structure and although not directly used in stock assessments themselves but having significant influence on parameters that are used in assessments (such as growth and mortality), diet and food webs). These voyages have a focus on the marine ecosystem that supports the SESSF and a number of the hypotheses being posed by the study are focused on target species within the SESSF and their food webs. This will result in significant sampling of those species , with the co-benefit that there will be new samples available for the contemporary estimation of key biological parameters and evaluation of the representativeness of parameters being used in stock assessments (and with sufficient sample numbers to ensure robust updated estimates). These voyages also provide a unique opportunity to build capacity in at sea sampling, exposure to ecosystem level sampling design and post-voyage biological analyses. By linking post voyage analyses with the direct needs of both stock assessments and ecosystem models used in the SESSF, the project provides opportunities for building deeper understanding of the use of biological parameters in stock assessments, and direct application of fisheries biology.

The so called pragmatic approach to the welfare of aquatic animals (Arlinghaus et al. 2007) measures welfare status using a variety of well-established, un-controversial physiological and functional parameters (Rose et al. 2014, Browman et al. 2019). For example, all finfish, crustaceans and cephalopods can experience stress, which can lead to poor welfare outcomes (Rose et al. 2014). From an animal welfare perspective, the overall aim to maximise fish welfare during capture is to minimise stress within the constraint of practices inherent to the relevant fishing sector (Mazur and Bodsworth 2022).
Using this pragmatic approach, the Aquatic Animal Welfare Working Group (AAWWG) which was formed under the Australian Animal Welfare Strategy (AAWS, 2005-2014), developed a range of Overarching Welfare Principles which related to finfish harvested from the wild in commercial fishing industries.
Out of the eight Overarching Principles developed by the AAWWG, as pointed out by Mazur and Bodsworth (2022) the three that are most relevant to the commercial wild harvest industry are:
1. Timely handling from capture to death is essential to minimise stress;
2. Capture methods should be designed to minimise the capture of unwanted species
3. Any fish selected for harvest should be killed as rapidly as possible, by humane means suitable for the species.
To address the legislative issues under the new Act, meet current and future fish welfare challenges, and maintain their social license to fish, commercial fishers targeting sharks in the NT need to develop workable and effective standards for handling and dispatching sharks which can be recognised and prescribed under the new Regulations.
Since shark fisheries are specialist fisheries which were not covered by the AAWWG during the AAWS, there is a need to develop specific resources to assist the industry with humane dispatch of sharks.
Science shows that brain destruction by pithing or “iki-jime” is the fastest way to dispatch finfish, resulting in the lowest levels of stress and maximising the quality and shelf life of the resulting fish product (Poli et al. 2005, Diggles 2015). However, the brains of sharks are small and vary in location between species, which is why this project is being proposed and is necessary to determine the brain location of the sharks most commonly captured in the NT shark fishery, and then examine various methods of rapidly destroying the brain, in order to develop guidelines and best practice protocols for their humane dispatch. Importantly, it should be noted that this is an industry driven project.

References

Arlinghaus R, Cooke SJ, Schwab A, Cowx IG (2007). Fish welfare: A challenge to the feelings based approach, with implications for recreational fishing. Fish and Fisheries 8: 57-71.

Browman HI, Cooke SJ, Cowx IG, Derbyshire SWG, Kasumyan A, Key B, Rose JD, Schwab A, Skiftesvik AB, Stevens ED, Watson CA, Arlinghaus R (2019). Welfare of aquatic animals: where things are, where they are going, and what it means for research, aquaculture, recreational angling, and commercial fishing. ICES Journal of Marine Science 76: 82–92. doi:10.1093/icesjms/fsy067

Diggles BK (2015). Development of resources to promote best practice in the humane dispatch of finfish caught by recreational fishers. Fisheries Management and Ecology DOI: 10.1111/fme.12127

Mazur N, Bodsworth A (2022). Practicing aquatic animal welfare: Identifying and mitigating obstacles to uptake and adoption by the Australian Seafood Industry. Final Report for FRDC Project No 2019-023, March 2022. 60 pgs.

Poli BM, Parisi G, Scappini F, Zampacavallo G (2005). Fish welfare and quality as affected by presaughter and slaughter management. Aquaculture International 13: 29-49.

Rose JD, Arlinghaus R, Cooke SJ, Diggles BK, Sawynok W, Stevens ED, Wynne CD (2014). Can fish really feel pain? Fish and Fisheries 15: 97–133.

Silver Sponsorship Package Benefits:
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