Novel fishery independent, biological and economic-processing methods to underpin expansion of Australia's fastest growing fishery, the Western Rock Octopus
The Western Rock Octopus fishery has become Australia’s fastest growing fishery, with a 5-year average growth of 50% per annum between 2017 and 2022. Despite this expansion, there are still significant gaps in knowledge and practice that do not allow this fishery to grow and develop in an optimum sustainable and socio-economic manner. This project will fill the information gaps and develop pro-active management and economic policy settings that facilitate a comprehensive development of the fishery to its natural capacity. It meets FRDCs two main outcomes of the 2020-2025 R&D plan; growth for enduring prosperity, best practices and production systems, and also meets Enabling Strategy IV: Building capacity and capability.
Proof-of-concept for innovative new octopus shelter pot and trigger trap designs.
Population biology of octopus species in NSW: research to support developmental octopus trap fisheries
Examining the potential impacts of seismic surveys on Octopus and larval stages of Southern Rock Lobster
CGG has NOPSEMA approval for a 3D seismic survey in the Gippsland Basin to commence in early 2020. This survey overlaps the Victorian shelter-pot octopus fishery off Lakes Entrance. This overlap has raised concerns from the fishing industry about the potential impacts to octopus and the fishers. Tank-based experiments simulating seismic exposure have resulted in high levels of damage in several species of octopus, however, it is unclear how experiments conducted in tanks translate into the field. Field-based seismic experiments have rarely been conducted on invertebrates, with no such studies conducted on octopus. However, the benthic and relatively sessile habit of octopus leaves them potentially vulnerable to impacts, as they have limited capacity to avoid the waterborne and ground-borne energy of seismic signals. CCG has agreed to provide funds to fill the knowledge gap surrounding the potential impact of seismic surveying on octopus and to do this in conjunction with a commercial scale seismic survey, with the lack of a full array often a perceived limitation of seismic research. CGG has also agreed to value add to the work around octopus. This opportunity allows for the potential impact of seismic surveying on larval forms to be examined, with some concerns around localised depletion of larvae of commercially and ecologically important species, such as southern rock lobster and commercial scallops. This project will use a field and laboratory experimental approach to provide a thorough assessment of the potential impacts of seismic surveys on octopus pallidus and its catches, along with rock lobster larvae and other important larvae. These approaches may assist fisheries and petroleum regulators to make informed decisions on the timing and manner in which future surveys are performed. Importantly, along with that of CGG, it has the support of the Victorian Fisheries Authority, who have also offered in-kind support, the two octopus fishers in the region, the Lakes Entrance Fishermen’s co-op, the sustainable shark fishing association and Southern Rock Lobster Inc.
Report
Key Findings
Exposure did not result in any elevated mortality for puerulus or juveniles. Immediately after exposure, righting was significantly impaired for all exposure treatments (E0 and E500 for juveniles and E0 for puerulus) compared to their respective controls, indicating that the impact range extended to at least 500 m from the source, the maximum range tested in the present study. After the first moult, there was no significant difference found in righting between juvenile Control and E0 treatments, and for puerulus, small sample size precluded statistical analysis. When these two stages were pooled, the combined E0 treatment was found to be significantly impaired. In the juvenile E500 lobsters, righting was similar to that of Controls, indicating that the lobsters had recovered from prior impairment. After the second moult, juvenile E0 lobsters showed significant impairment compared to controls. When puerulus, which could not be analysed due to small sample size, were pooled with juveniles, the combined E0 treatment was significantly impaired relative to combined Controls. Righting in juvenile E500 lobsters was similar to that of controls, further supporting recovery in this treatment. Impaired righting has previously been found to correlate with damage to the statocyst, the mechanosensory organ common to many marine invertebrates. The results here from the combined puerulus and juvenile treatments indicated that puerulus and juvenile E0 treatments did not show the capacity for recovery whereas juvenile E500 lobsters recovered from impairment after the first moult, providing evidence of a range threshold for recovery. Intermoult period was significantly increased in E0 juvenile lobsters and appeared to be increased in puerulus, though the latter could not be statistically analysed. Juvenile E500 treatment showed a moderate, non-significant increase in moult duration. Increased intermoult duration suggested impacted development and potentially slowed growth, though the proximate cause was not identified.
• Sound exposure levels recorded in this study were similar to those of prior experiments conducted with a single air gun, validating the single air gun approach for future field-based experimental work.
• Air gun signals caused righting impairment to at least 500 m, the maximum range in this study, in lobsters sampled immediately following exposure, a similar result previously reported in adults that corresponded with significant damage to the mechanosensory statocyst organ that provides the sense of balance, body position and movement that are critical for predator avoidance behaviour.
• Impairment resulting from close range exposure (i.e., combined puerulus and juvenile E0 treatments) appeared to be persistent, as previously reported in adult lobsters, whereas lobsters exposed at a more distant range (juvenile E500) showed recovery. This indicates that a range of 500 m may not cause lasting impairment to righting.
• Intermoult duration was significantly increased in E0 juveniles and appeared to be increased in E0 puerulus, indicating the potential for slowed development and growth and physiological stress.
Understanding population structure and dynamics of Victoria’s developing Octopus fishery
In Victoria, Octopus spp. are predominantly a byproduct species caught across various fisheries. Pale Octopus is not differentiated from other octopus species in catch and effort reporting in Victoria, making it difficult to apply stock assessment methods or catch rate indicators. Maori Octopus (Octopus maorum) are likely caught in the Victorian Rock Lobster Fishery (VRLF); whereas Pale Octopus and Gloomy Octopus (Octopus tetricus) are caught within the Inshore Trawl Fishery, Ocean Access Fishery (OAF), Corner Inlet Fishery (CIF) and Port Phillip and Westernport Bay Fishery (PPWPBF). Targeting octopus using 'shelter traps' within the OAF off Lakes Entrance has significantly increased in 2016 and 2017. The average catch during this period was ten times greater compared with the average catch taken from 2006–2015. With the potential for a developing fishery, management is lacking fundamental information to assist in guiding and building a sustainable fishery. For example, there is no requirement to identify and report quantities of species caught. This makes any sort of assessment impossible. Presently, two license holders actively fish for octopus with a capacity to have many more within the OAF.
Species identification of Australia’s most significant octopus fishery – the Western Australian Common Octopus
Octopus aff. tetricus or the Western Australian common octopus is an endemic species of the temperate waters of Western Australia. It is closely related to the cosmopolitan O. vulgaris species complex, and the ‘gloomy octopus’, O. tetricus on the east coast of Australia and New Zealand, but has been conclusively identified as a separate species through genetic and morphometric studies (Guzik et al., 2005; Amor et al., 2014). Currently, the common octopus supports the largest single-species octopus fishery in Australia, however the animal caught is an unnamed species, and carries the species affinis “Octopus aff. tetricus” instead. This is not an ideal situation for two reasons. First, it hinders a proper assessment of its significant contribution to the Australian cephalopod fisheries harvest. For example there is no dedicated SAFs report for this species, despite the catch levels harvest being three times greater than the 'Pale Octopus' (Octopus pallidus) from Tasmania, which does have its own SAFs assessment report. Secondly, there is an industry impetus to differentiate the product in the marketplace in order to create a distinct branding of the Western Australian octopus fishery into the future. Thus there is both a scientific/administrative need and a marketing need to formalise the correct species name, and its associated common name.