Mangrove Jack (Lutjanus argentimaculatus) are a long lived (>50 years), late maturing (~6 to 10 years) species that can grow to a large size (>1 metre). Their typical distribution in Australian waters extends from Perth, around the north of the continent to Sydney. Mangrove Jack spend several years as juveniles in freshwater and estuarine habitats before migrating to deeper, offshore waters as they near sexual maturity.

Mangrove Jack are popular amongst all fishing sectors; their aggressive feeding and tendency to aggregate (as both juveniles and adults) also makes them vulnerable to overfishing. Juvenile Mangrove Jack are primarily (but not exclusively) caught by Indigenous fishers, recreational fishers and charter boat clients around estuaries and inshore reefs, whereas adults are caught (occasionally in significant quantities) by offshore trawl operations to the west of Cape York.

The sustainability of Mangrove Jack is assessed under the national Status of Australian Fish Stocks (SAFS) reporting framework, which relies on an understanding of the stock structure of each focal species. Previous genetic analyses using mitochondrial and microsatellite markers suggest that Mangrove Jack form a single homogeneous stock in Australian waters. However, these analytical tools often lack the resolution necessary to detect fine-scale stock structure in larval dispersing fishes. This in turn compromises current stock assessment approaches for Mangrove Jack (undertaken at the jurisdictional or management unit level) as there may be a spatial mismatch between the area of the assessment unit/s and the true stock structure of this species; a situation confounded by a limited understanding of the dynamics of ontogenetic migration/connectivity in Mangrove Jack.

This being the case, there is a pressing need to examine the population structure and connectivity of Mangrove Jack across its Australian range. This will be achieved through a combination of cutting-edge genetic methods (i.e. single nucleotide polymorphisms), otolith micro-chemistry and parasite analyses, in order to address the national FRDC priority “Resolving stock uncertainty for priority species (including Mangrove Jack)”.

Commercial scallop is fished by dredging in 3 jurisdictions, with Tasmania (TSF) and Victoria currently classified as depleted. The 3rd jurisdiction, the BSCZSF, closes some scallop beds to fishing while the rest of the fishery remains open for harvesting. The closed beds and the TAC are informed by an annual dredge survey. These surveys also give an indication of recruitment within the fishery. However, the size selectivity of the dredges is not considered in this process, which may result in an under-estimation of recruitment. The need to minimise disturbance to juvenile beds to reduce mortality of small scallops through survey activities is also a consideration. Currently the only options for known juvenile scallop beds are to not survey them or to conduct a minimal number of dredge shots, noting that commercial dredges do not effectively sample juveniles. The TSF only opens a small area of the fishery following annual dredge surveys, with the remainder closed. However, the issue of the estimation of recruitment and sensitivity of juveniles to dredging during surveys and fishing is still relevant, as only those beds with > 80% legal sized scallops are opened. Comparison of TSF 2020 video survey results with dredge survey results demonstrated much greater size selectivity by scallop dredges for legal-sized scallops than was previously thought, such that relying on dredge surveys alone to inform management decisions may be jeopardising the sustainability of the fishery. Along with the need to define the size distribution of scallop beds more accurately within the fishing zones, both Tasmania and the Commonwealth have areas closed to scallop fishing that contain an unknown scallop biomass that may contribute to recruitment. AFMA and Tasmanian DPIPWE resource managers and industry members are committed to further investigating and optimising the use of towed video surveys to provide a survey method for both inshore and offshore waters to estimate both legal and sub-legal scallop density/biomass in fishery zones, as well as areas closed to dredging and known juvenile beds, which will in turn inform management decisions, such as area closures and setting of TACs, and contribute to more sustainable fisheries.

There is no current information on total recreational fishing effort or landings for Victorian fisheries and therefore no continuous time series on these variables, as is the case in most jurisdictions. This represent a key knowledge gap, and hence risk, for fisheries sustainability in the state and has resulted in several fisheries (i.e. those with significant recreational catch) being assessed as ‘Undefined’ in the most recent SAFS round.
In addition to the above, the Victorian Government has brought out several bay and inlet fisheries over the last two decades, meaning recreational catch is the most significant harvest component for most species/stocks. This also means that there is no longer commercial logbook data being obtained on which to base assessment of these species/stocks. As such, having recreational catch and effort information will enable more sophisticated population dynamic stock assessment models to be used for assessment purposes. Victoria possesses such a model that is parameterised for the Western Victorian Snapper Stock (WVSS), complete with management strategy evaluation, that cannot be used to inform decision making at present because the landings from the largest fleet (i.e. boat based recreational fishers) are currently unknown.
Recreational catch and effort information will be used for ongoing stock assessment to inform management advice to inform the following immediate, direct priorities: 1) WVSS harvest strategy, 2) rebuilding of the Gippsland Lakes black bream stock, 3) Corner Inlet Management Plan, and 4) assessment of the eastern Victorian snapper stock.

The lack of knowledge on fundamental fisheries biology, uncertainty in stock structure, population dynamics, and cross-sectoral harvest levels, means that current stock assessments are unequipped to reliably determine stock status or inform recommended biological catches (RBCs), and that management of the resource occurs within a high degree of uncertainty. These EXCEPTIONAL INCREASES IN HARVEST and UNCERTAINTY SURROUNDING SUITABLE RBCs create an URGENT NEED TO DEAL WITH THE SUBSTANTIAL KNOWLEDGE VACUUM FOR THIS RESOURCE. Without this improved knowledge, the reasonable assessment of the status of the resource, estimation of appropriate harvest levels, harvest strategy development, implementation of appropriate management, and informed decision making on how best to utilise the resource, will continue not to be possible. Furthermore, environmental variability and species-habitat-fishery interactions are likely to impact stock dynamics and biomass, which in turn affects the magnitude, profitability, and social outcomes derived from the resource. Thus, efficient exploitation and effective management of the resource within a harvest strategy framework cannot occur without: 1) spatial definition of likely management units (stock structure); 2) estimates of stock biomass within those units; 3) estimates of basal population parameters and some appreciation of the influence of environmental stochasticity on resource productivity; and, 4) an appreciation of resource access across sectors. There is likely potential for further development in this fishery, to satisfy growing markets for the species both locally and abroad, but this will never be realised until these information needs are met.

There is a need to increase economic growth of environmentally sustainable industries in northern Australia and this project aims to increase recreational billfish fisheries tourism and facilitate management of this emerging resource. The tourism industry in Australia including recreational fisheries and associated travel sectors have been severely impacted due to Covid-19. With an estimated economic value of $3185AUD per charter fishing trip, recreational billfish fisheries represent a high-value and sustainable option to help develop post-Covid-19 fisheries tourism in northern Australia.

There is an emerging recreational billfish fishery in Northern Territory waters but growth, participation and management of a sustainable fishery has been hampered by a lack of data and public awareness. Anecdotal evidence suggests that a recent increase in catches of sailfish and black marlin in waters off northern Australia may have been facilitated by the closure of Taiwanese Gillnet fisheries which operated in Australian waters between 1972 and 1986. However, there has been little scientific evaluation of past or current billfish fisheries resources in the region, and better quality fisheries data and information on the spatial distribution and seasonal movement patterns are required to guide development and management of sustainable fisheries. The catch-and-release billfish fisheries of northern Australia are likely to be sustainable but stocks are likely to be affected by fisheries in the broader Indo-Pacific region and further information is needed to inform assessments as part of the Status of Australian Fish Stocks Report. As is this a developing fishery there is a need to form a ground up educational programs on the best practices for responsible handling of billfish in the NT recreational fishery.