Gulf of Carpentaria Developmental Finfish Trawl Fishery : Maximum Sustainable Yield

The Gulf of Carpentaria Finfish Trawl Fishery operates under developmental permits and harvests five main tropical snapper species. The fishery operates in eastern Gulf of Carpentaria waters and is managed by Fisheries Queensland on behalf of the Queensland Fishery Joint Authority. For the years 2004–2014, the fishery Total Allowable Commercial Catch (TACC) was fixed at 1250 t and substantially under-filled. In 2011 new stock analyses were published for the fishery. Results were presented to industry including the estimated equilibrium maximum sustainable yield (MSY) of 450 t for east Gulf of Carpentaria waters. The MSY value represented the maximum average combined species harvest that can be taken long-term; combining MSY harvests of the five main species. For the 2015 calendar year, a revised 450 t harvest quota was set for Crimson Snapper, Saddletail Snapper, Red Emperor and other Emperor species; plus a tonnage allowance for other permitted species. The revised quota tonnage represented a considerable reduction from the 1250 t set in previous years. Industry raised questions about not understanding how the MSY was arrived at and why it was less than early 1990s yield estimates. The purpose of this report is to explain the MSY estimates for east Gulf of Carpentaria waters. The 450 t MSY represents at present the best estimate available and is consistent with pre-2011 estimates

Stout Whiting Fishery Summary : Queensland Total Allowable Catch for 2016

In Queensland, stout whiting are fished by Danish seine and fish otter-trawl methods between Sandy Cape and the Queensland-New South Wales border. The fishery is currently identified by a T4 symbol and is operated by two primary quota holders. Since 1997, T4 management has been informed by annual stock assessments in order to determine a total allowable commercial catch (TACC) quota. The TACC is assessed before the start of each fishing year using statistical methodologies. This includes evaluation of trends in fish catch-rates and catch-at-age frequencies against management reference points. The T4 stout whiting TACC for 2014 was adjusted down to 1150 t as a result of elevated estimates of fishing mortality and remained unchanged in 2015 (2013 TACC = 1350 t quota). Two T4 vessels fished for stout whiting in the 2015 fishing year, harvesting 663 t from Queensland waters. Annual T4 landings of stout whiting averaged about 713 t for the fishing years 2013–2015, with a maximum harvest in the last 10 fishing years of 1140 t and a maximum historical harvest of 2400 t in the 1995. Stout whiting catch rates from both Queensland and New South Wales were analysed for all vessels, areas and fishing gears. The 2015 catch rate index was equal to 0.85, down 15% compared to the 2010–2015 fishing year average (reference point =1). The stout whiting fish length and otolith weight frequencies indicated larger and older fish in the calendar year 2014. This data was translated to show improved measures of fish survival at about 38% per year and near the reference point of about 41%. Together, the stout whiting catch rate and survival indicators show the fishery was sustainable. Earlier population modelling conducted for the year 2013 also suggested the stock was sustainable, but the estimate was only marginally above the biomass for maximum sustainable yield. Irrespective, reasons for reduced catch rates should be examined further and interpreted with precaution, particularly given the TACC has been under-caught in many years. For setting of the 2016 TACC, alternate analyses and reference points were compared to address data uncertainties and provide options for quota change. The results were dependent on the stock indicator and harvest procedure used. Uncertainty in all TACC estimates should be considered as they were sensitive to the data inputs and assumptions. For the 2016 T4 fishing year, upper levels of harvest should be limited to 1000–1100 t following procedure equation 1, with target levels of harvest at 750–850 t for procedure equation 2. Use of these estimates to set TACC will depend on management and industry intentions

Stock assessment of Queensland east coast blue swimmer crab (Portunus armatus)

Blue swimmer crabs are widely distributed in Australia. They are found along the western coast of Australia, across Australia’s north and down the east coast to the New South Wales–Victoria border. This assessment of the north eastern Australian (Queensland) blue swimmer crab biological stock, informs the status of the stock and the harvest strategy development under Queensland’s Sustainable Fisheries Strategy. This stock assessment used a length-structured model with a monthly time step. Data inputs included total harvests, standardised catch rates, and carapace width size compositions. Model analyses suggested that exploitable (legal sized male) biomass fell to around 33 per cent of unfished biomass in 2018–19. The blue swimmer crab harvest control rule recommends an initial harvest limit of 129 t to begin rebuilding the stock to levels consistent with 60% of unfished biomass

Monitoring requirements for common coral trout

Some studies have suggested that in certain situations, there is a poor correlation between fishery catch rates for coral trout and the species abundance. Environmental factors, such as cyclones, can affect fishery catch rates for some time after the event and social learning results in lower catchability of fish. The actual state of the stock may be more stable than fishery catch rates indicate (Leigh et al., 2014). The uncertainty in the relationship between fishery catch rates and fish abundance means there is strong evidence, and need, to collect additional abundance data to support stock assessment, reference point (quota) management and harvest strategies. To date, the most informative indices of coral trout abundance were those taken from underwater visual surveys, as there was no reliance on fish taking bait or the fishery temporal-spatial patterns of fishing. The underwater visual surveys also measures an index of fish abundance that is not as sensitive to change in fish behaviour due to cyclones and social learning

Assessment of the barramundi (Lates calcarifer) fishery in the Southern Gulf of Carpentaria, Queensland, Australia.

Wild-capture barramundi (Lates calcarifer) forms the basis of important commercial, recreational and customary Indigenous fisheries in Queensland, with an estimated harvest of about 700 tonnes in 2015 (Saunders et al. 2016). For stock status assessment, barramundi in Queensland are considered to consist of seven genetically distinct populations. Within the Gulf of Carpentaria (GoC), there are two genetic stocks split at around 13⁰ S - a Northern Gulf of Carpentaria stock and a Southern Gulf of Carpentaria stock. The Gulf of Carpentaria Inshore Fin Fish Fishery harvests barramundi from both these stocks, but the current assessment focuses on the Southern Gulf of Carpentaria (Southern GoC) barramundi stock, which produces, on average, greater than 50% of the annual commercial harvest of barramundi in Queensland and was listed as transitional-depleting in the 2016 Status of Australian Fish Stocks report (Saunders et al. 2016)

Stock assessment of the Queensland Gulf of Carpentaria Spanish mackerel (Scomberomorus commerson) fishery

Spanish mackerel (Scomberomorus commerson) is a pelagic species that forms genetic populations (stocks) around northern Australia. For this stock assessment, we have investigated fish harvested from eastern waters of the Gulf of Carpentaria, Queensland. This stock assessment was set up as an age-structured model with a yearly time step and length-based selectivity. The annual data inputs included total fish harvest, standardised catch rates, length structures and conditional age at length data. The model used data from 1940 to 2018. The assessment suggested the stock in 2018 was between 30 and 40 per cent unfished spawning biomass. The recommended biological catch was estimated at 21 t, which is below the 2018 harvest of 181 t. This initial catch estimate aims to allow the stock to rebuild to the target 60 per cent spawning biomass. Smaller harvests are estimated at first to be taken in early years, which increase through time as the fish population builds higher

Stock assessment of the Queensland east coast common coral trout (Plectropomus leopardus) fishery

Common coral trout Plectropomus leopardus is an iconic fish of the Great Barrier Reef (GBR) and is the most important fish for the commercial fishery there. Most of the catch is exported live to Asia. This stock assessment was undertaken in response to falls in catch sizes and catch rates in recent years, in order to gauge the status of the stock. It is the first stock assessment ever conducted of coral trout on the GBR, and brings together a multitude of different data sources for the first time. The GBR is very large and was divided into a regional structure based on the Bioregions defined by expert committees appointed by the Great Barrier Reef Marine Park Authority (GBRMPA) as part of the 2004 rezoning of the GBR. The regional structure consists of six Regions, from the Far Northern Region in the north to the Swains and Capricorn–Bunker Regions in the south. Regions also closely follow the boundaries between Bioregions. Two of the northern Regions are split into Subregions on the basis of potential changes in fishing intensity between the Subregions; there are nine Subregions altogether, which include four Regions that are not split. Bioregions are split into Subbioregions along the Subregion boundaries. Finally, each Subbioregion is split into a “blue” population which is open to fishing and a “green” population which is closed to fishing. The fishery is unusual in that catch rates as an indicator of abundance of coral trout are heavily influenced by tropical cyclones. After a major cyclone, catch rates fall for two to three years, and rebound after that. This effect is well correlated with the times of occurrence of cyclones, and usually occurs in the same month that the cyclone strikes. However, statistical analyses correlating catch rates with cyclone wind energy did not provide significantly different catch rate trends. Alternative indicators of cyclone strength may explain more of the catch rate decline, and future work should investigate this. Another feature of catch rates is the phenomenon of social learning in coral trout populations, whereby when a population of coral trout is fished, individuals quickly learn not to take bait. Then the catch rate falls sharply even when the population size is still high. The social learning may take place by fish directly observing their fellows being hooked, or perhaps heeding a chemo-sensory cue emitted by fish that are hooked. As part of the assessment, analysis of data from replenishment closures of Boult Reef in the Capricorn–Bunker Region (closed 1983–86) and Bramble Reef in the Townsville Subregion (closed 1992–95) estimated a strong social learning effect. A major data source for the stock assessment was the large collection of underwater visual survey (UVS) data collected by divers who counted the coral trout that they sighted. This allowed estimation of the density of coral trout in the different Bioregions (expressed as a number of fish per hectare). Combined with mapping data of all the 3000 or so reefs making up the GBR, the UVS results provided direct estimates of the population size in each Subbioregion. A regional population dynamic model was developed to account for the intricacies of coral trout population dynamics and catch rates. Because the statistical analysis of catch rates did not attribute much of the decline to tropical cyclones, (and thereby implied “real” declines in biomass), and because in contrast the UVS data indicate relatively stable population sizes, model outputs were unduly influenced by the unlikely hypothesis that falling catch rates are real. The alternative hypothesis that UVS data are closer to the mark and declining catch rates are an artefact of spurious (e.g., cyclone impact) effects is much more probable. Judging by the population size estimates provided by the UVS data, there is no biological problem with the status of coral trout stocks. The estimate of the total number of Plectropomus leopardus on blue zones on the GBR in the mid-1980s (the time of the major UVS series) was 5.34 million legal-sized fish, or about 8400 t exploitable biomass, with an 2 additional 3350 t in green zones (using the current zoning which was introduced on 1 July 2004). For the offshore regions favoured by commercial fishers, the figure was about 4.90 million legal-sized fish in blue zones, or about 7700 t exploitable biomass. There is, however, an economic problem, as indicated by relatively low catch rates and anecdotal information provided by commercial fishers. The costs of fishing the GBR by hook and line (the only method compatible with the GBR’s high conservation status) are high, and commercial fishers are unable to operate profitably when catch rates are depressed (e.g., from a tropical cyclone). The economic problem is compounded by the effect of social learning in coral trout, whereby catch rates fall rapidly if fishers keep returning to the same fishing locations. In response, commercial fishers tend to spread out over the GBR, including the Far Northern and Swains Regions which are far from port and incur higher travel costs. The economic problem provides some logic to a reduction in the TACC. Such a reduction during good times, such as when the fishery is rebounding after a major tropical cyclone, could provide a net benefit to the fishery, as it would provide a margin of stock safety and make the fishery more economically robust by providing higher catch rates during subsequent periods of depressed catches. During hard times when catch rates are low (e.g., shortly after a major tropical cyclone), a change to the TACC would have little effect as even a reduced TACC would not come close to being filled. Quota adjustments based on catch rates should take account of long-term trends in order to mitigate variability and cyclone effects in data

Fishing power increases continue in Queensland's east coast trawl fishery, Australia

The Queensland east coast trawl fishery is by far the largest prawn and scallop otter trawl fleet in Australia in terms of number of vessels, with 504 vessels licensed to fish for species including tiger prawns, endeavour prawns, red spot king prawns, eastern king prawns and saucer scallops by the end of 2004. The vessel fleet has gradually upgraded characteristics such as engine power and use of propeller nozzles, quad nets, global positioning systems (GPS) and computer mapping software. These changes, together with the ever-changing profile of the fleet, were analysed by linear mixed models to quantify annual efficiency increases of an average vessel at catching prawns or scallops. The analyses included vessel characteristics (treated as fixed effects) and vessel identifier codes (treated as random effects). For the period from 1989 to 2004 the models estimated overall fishing power increases of 6% in the northern tiger, 6% in the northern endeavour, 12% in the southern tiger, 18% in the red spot king, 46% in the eastern king prawn and 15% in the saucer scallop sector. The results illustrate the importance of ongoing monitoring of vessel and fleet characteristics and the need to use this information to standardise catch rate indices used in stock assessment and management

Sustaining productivity of tropical red snappers using new monitoring and reference points

OBJECTIVES: 1. Analyse current monitoring and logbook data sets, as well as survey and other information,to establish whether these data provide sufficient power to develop critical indicators of fishery performance. 2. Provide a risk analysis that examines the use of age structure and catch rate information for development of critical indicators, and response rules for those criteria, in the absence of other fishery information. 3. Develop a monitoring program that uses commercial vessels from the fishery to provide independent data

Stock assessment of the Australian east coast spotted mackerel (Scomberomorus munroi) fishery 2018

Australian east coast spotted mackerel, Scomberomorus munroi, is a pelagic fish species harvested by commercial, charter and recreational fishers. It forms a single genetic stock in Queensland and New South Wales. The stock is shared with NSW although over 80 per cent of the harvest is from Queensland waters. Spotted mackerel exhibit schooling behaviours that make them susceptible to overfishing. The Queensland commercial line and net fishery operates under a quota system for spotted mackerel (140 tonnes total allowable commercial catch). Recent commercial harvest (2013–2018) was around 64 tonnes per year. Catch shares (in 2013–14) in Queensland were around 55 per cent commercial and 45 per cent recreational. The formal stock assessment was requested to update the status of the stock and inform fishery management agencies and stakeholders on estimates of sustainable harvest that will build and maintain the fishery in the long term. The 2018 stock assessment combined data in an annual age-structured population model tailored for the biology, management and fishing history of spotted mackerel. The age-structured population model analysed 252 scenarios based on different combinations of input data, including harvest histories, age structures, standardised catch rates and considered both high and low estimates of natural mortality. The assessment suggests that the spotted mackerel biomass in 2016–17 is between 40 and 60 per cent of unfished biomass (all sectors and jurisdictions). The assessment provides estimates of the maximum sustainable yield (MSY) and recommends a total allowable catch to rebuild the stock to the Sustainable Fisheries Strategy (SFS) longer term target of 60% unfished biomass (as a proxy for MEY) by 2027