2021 assessment of the status of the West Coast Demersal Scalefish Resource

A recovery program for the West Coast Demersal Scalefish Resource was introduced between late 2007 and early 2010, based on the maintenance of retained catches of demersal species (overall suite and each indicator species) by both the commercial and recreational sectors below 50% of the catches reported in 2005/06 (original catch recovery benchmarks)

Longevity in Australian snapper Pagrus auratus (Sparidae)

In fisheries biology, longevity is one of the estimators of natural mortality, an essential parameter for age-based stock assessments. Increased fishing pressure progressively truncates older fish from the population, highlighting the importance of documenting observations of exceptionally old individuals. Snapper (Pagrus auratus) constitute important fisheries around the southern half of mainland Australia. A literature search and survey of government and semi government agencies responsible for managing snapper fisheries in 5 Australian states reveals the species is capable of living to at least 40 years throughout much of its range. The oldest recorded age, from near Bunbury, Western Australia, was recently estimated to be 40 years and 10 months

Evaluating active-acoustic methods for assessing snapper (Chrysophrys auratus) spawning aggregations in Western Australia

Snapper (Chrysophrys auratus) is an important commercial and recreational species, in Australia and New Zealand. From late winter to early summer, adult snapper migrate the broader metropolitan waters of Perth Western Australia into the protected embayment’s of Cockburn Sound, Warnbro Sound and Owen Anchorage to form spawning aggregations. In Cockburn Sound, they can be acutely exposed to anthropogenic (e.g. industry, fishing) and environmental factors (e.g. deoxygenation, elevated temperatures) that may affect numbers, spawning success and subsequent recruitment. Monitoring the status of these tightly-managed aggregations is particularly important as impacts of these stressors can be significant and rapid. To facilitate this monitoring, evaluation of commonly used methods for estimating spawning biomass (e.g. daily egg production method), against those that take advantage of developing methods (e.g. hydroacoustic), would be beneficial. To this end, active-acoustic data were collected from spawning aggregations of snapper in Cockburn Sound over two days in November 2016 to determine the packing density, vertical and horizontal distribution and length estimates of individuals (using a BioSonics DT-X single-beam echosounder at 38 and 120 kHz and a BlueView M900-2250 multibeam echosounder at 900 kHz). Length estimates were compared with historic fishery-independent length data. Acoustic data were analysed using Echoview software. Computed tomography scans of individual snapper were used to model the frequency-dependent acoustic backscatter and validate the BioSonics information from single targets. We approximated school shape and packing density using novel model approaches which can deliver estimates of school biomass, with accompanying error estimates. This study forms the first step towards an acoustic assessment of snapper in Cockburn Sound, which could be applied to other aggregations in Western Australia and elsewhere across its distribution

Ecological risk assessment for the Western Australian Large Pelagic Fish Resource

In December 2023, the Department of Primary Industries and Regional Development (DPIRD, the Department) convened an ecological risk assessment (ERA) of the fisheries that access the Statewide Large Pelagic Fish Resource (Resource). This Resource comprises a range of tropical and temperate species including mackerels, billfish, kingfish, cobia, mahi mahi and tunas. This document contains the background information used to support the ERA risk scoring process, scoring from the workshop and a summary of the workshop discussions that were relevant to the risk scoring. This includes an overview of Western Australian commercial fisheries that access the Resource, with a focus on the Mackerel Managed Fishery. This report also includes information about recreational and charter fisheries that access the Resource. ERAs are conducted by the Department as part of its Ecosystem Based Fisheries Management framework. Accordingly, the ERA will consider the potential ecological impacts of harvesting of the Resource. This includes impacts of fishing on all relevant retained and bycatch (non-retained) species, endangered, threatened and protected species, aquatic habitats and the broader environment. Risk scores were determined during the ERA workshop, based on available scientific information and expert knowledge. The assessment will conform to the AS/NZS ISO 31000 risk management standard, and to the methodology adopted by the Department, which uses a consequence-likelihood analysis for estimating risk. A broad range of stakeholders were invited to participate in the ERA workshop, including representatives of the commercial, recreational, and charter fishing sectors, State and Commonwealth Government agencies, the conservation sector, universities, and DPIRD staff including fisheries managers, scientists, compliance officers and biosecurity personnel. In this ERA, forty-one ecological components were scored for risk. The vast majority (39) of ecological components were evaluated as low or negligible risks, which do not require any specific control measures. There were 2 medium risks, which were assessed as acceptable under the current monitoring regime and control measures that will be in place over the next five years. No components were scored as high or severe risks. It is recommended that the risks be reviewed in five years

Development of techniques for the collection and culture of wild-caught fertilised snapper (Chrysophrys auratus) eggs for stock enhancement purposes

Restocking or stock enhancement programs have traditionally relied on captive broodstock to produce individuals for release into the wild. However, this is costly and may limit genetic diversity of the resulting progeny. If fertilised eggs could be collected from the wild and individuals reared for release, the genetic diversity of the released progeny may be improved and associated restocking/enhancement programs may become more cost-effective. Snapper (Chrysophrys auratus: Sparidae), is an iconic recreational and commercial fish species across Australia and New Zealand and has been subjected to overfishing in many locations. Enhancement programs may be useful for increasing biomass in some circumstances, but would require careful evaluation of advantages and disadvantages before commencement. This study developed and optimised egg collection methods for snapper from its wild spawning aggregations in Cockburn Sound, Western Australia, and developed effective otolith marking techniques that would enable future monitoring of released individuals. The study identified the optimum sea conditions for collecting large numbers ( \u3e 100,000) of eggs using plankton nets, in addition to the need for side-scan sonar to locate spawning aggregations, the distance from aggregations at which to sample and the water depth for plankton net tows. Large numbers of eggs collected in 2014 and 2015 were subsampled and visually screened for presence of snapper eggs using known egg diameters. Real-time PCR techniques validated visual identifications of snapper eggs and larvae, limiting accidental rearing of non-target species and reducing associated costs. Trials on larvae reared from these eggs, successfully determined appropriate alizarin complexone concentrations and immersion times for producing enduring marks on post-larvae otoliths. These marks remained visible in otoliths after 12 months, potentially allowing future monitoring of fish released into the wild. Delayed disinfection of eggs to the second day after capture resulted in improved egg viability. Following optimisation of collection and culture techniques, 208,000 larvae were stocked from a single sampling occasion in 2015, of which 19% survived to 55 days post hatch (dph). This survival rate is typical for snapper produced from captive broodstock. This study demonstrated that wild spawned snapper eggs can be captured and cultured in high numbers and future identification of recaptured released fish potentially conducted. An associated genetic study also demonstrated no loss of genetic diversity in cultured fish versus that of adults in the spawning aggregations. This technique has the potential to reduce both the cost of restocking/stock enhancement programs for snapper (and could be evaluated for other suitable aggregating species) and the risks of altering the genetic makeup of wild stocks

A comparison of the stock structures of two exploited demersal teleosts, employing complementary methods of otolith element analysis

Complementary methods of otolith element analysis (IRMS of stable isotopes and laser ablation ICP-MS of trace elements) were used to elucidate the stock structures in Western Australia of the exploited demersal West Australian dhufish Glaucosoma hebraicum and Snapper Pagrus auratus. Residency of adults during their most recent part of life and the existence of important nursery locations were investigated by analysing otolith margins and cores, respectively, to evaluate the applicability of current spatial management. Stable oxygen isotope ratios (18O/16O) in both margins and cores of G. hebraicum otoliths increased with latitude and thus decreasing mean annual water temperature. Analyses of δ18O, stable isotope composition (SI; δ18O, δ13C) and trace element composition (TE; 25Mg, 88Sr, 138Ba) in otolith margins of G. hebraicum from four management areas on the west coast of Australia indicated that adults were resident in each area. Analyses of elements in otolith cores demonstrated that, by the early juvenile stage (\u3c 1 year old), individuals will have recruited to the area where they will remain as adults. Analyses of δ18O and both SI and TE compositions in otolith margins of adult P. auratus indicated residency within each of three large bioregions (Gascoyne, GCB; West, WCB; South, SCB) along the west and south coasts of western Australia. As for G. hebraicum, the data also demonstrated residency at the finer scale, i.e. within the four management areas on the west coast. The lack of a conspicuous pattern in δ18O levels in P. auratus otolith cores implied that adults in each area recruited from a range of nurseries. Although both SI and TE composition demonstrated that there was substantial self-recruitment within the WCB and SCB and within two of the four areas of the WCB, stock(s) of P. auratus at the southern extent of the GCB are likely to be partially reliant on immigration. Elemental signatures in otoliths of G. hebraicum and P. auratus demonstrated that adults in each management area of the WCB could be treated as separate stocks. However, while recruitment of juvenile G. hebraicum to adult stocks would occur primarily from adjacent multiple nurseries within areas of the WCB, adult P. auratus in any one bioregion and at least two of the four areas within the WCB were derived from a range of nurseries, including across area and bioregion boundaries

Ecological risk assessment for the Western Australian Cephalopod Resource

On 27 October 2023, the Department of Primary Industries and Regional Development (DPIRD, Department) convened an ecological risk assessment (ERA) of the fisheries that access the statewide Cephalopod Resource (Resource), which comprises a range of octopus, squid and cuttlefish species. This document contains the background information used to support the ERA risk scoring process, and a summary of the workshop discussions that were relevant to the risk scoring. The background information includes an overview of Western Australian commercial fisheries that access the Resource, focusing primarily on the Octopus Interim Managed Fishery (OIMF), Cockburn Sound Line and Pot Managed Fishery (CSLPMF), South Coast Line and Fish Trap Managed Fishery (SCLFTMF), and commercial open-access fisheries (OAF) in each bioregion. This report also includes information about statewide recreational and charter fisheries that access the Resource. The Department conducts ERAs as part of its Ecosystem Based Fisheries Management (EBFM) framework. Accordingly, the ERA considered the potential ecological impacts of harvesting of the Resource. This includes impacts of fishing on all relevant retained and bycatch (non-retained) species, endangered, threatened and protected species, aquatic habitats and the broader environment. Risk scores were determined during the ERA workshop, based on available scientific information and expert knowledge. The assessment conformed to the AS/NZS ISO 31000 risk management standard, and to the methodology adopted by the Department, which uses a consequence-likelihood analysis for estimating risk. A broad range of stakeholders were invited to participate in the ERA workshop, including representatives of the commercial, recreational, and charter fishing sectors, State and Commonwealth Government agencies, the conservation sector, universities, and DPIRD staff including fisheries managers, scientists, compliance officers and biosecurity personnel. Outcomes and scoring from the workshop are summarised in this document. Thirty-eight ecological components were scored for risk, including individual components that were separated by bioregion or by fishery. The vast majority (32) of ecological components were evaluated as low or negligible risks, which do not require any specific control measures. There were 6 medium risks, which were assessed as acceptable under the current monitoring regime and control measures that will be in place over the next five years. No components were scored as high or severe risks. It is recommended that the risks be reviewed in five years