Stock assessment of pelagic bait fishes in southern Queensland with special reference to pilchards (Sardinops sagax)

The pilchard fisheries of Australia expanded rapidly during the 1980s and 1990s and the need for biological information to facilitate ecologically sustainable development of the fisheries led to the initiation of projects funded by the Fisheries Research and Development Corporation (FRDC). The aims of the projects described for southern Queensland were: to examine the species composition of purse-seine catches; to describe the size structure of the species caught by purse-seining and determine the age-structure of the pilchard population; to identify the location and timing of clupeoid spawning; to estimate the spawning biomass of pilchards using the Daily Egg Production Method; to examine the potential impacts of a purse-seine fishery on populations of bait fish and on other stakeholders; to develop and assess methods for preventing the encirclement and mortality of dolphins in purse-seine nets and to examine the potential yield of a purse-seine fishery for pilchards

Performance of Queensland’s net-free zones

On 1 November 2015, three net-free zones (NFZs) were established in the Cairns, Mackay and Rockhampton regions. The objective of the NFZs is for recreational fishers to catch more and bigger fish, which will increase their enjoyment of recreational fishing in the region. If this occurs, fishers are likely to travel from further afield to fish NFZs, thereby supporting local businesses and tourism. To examine the impact of the NFZs on recreational fishing, surveys were undertaken at local boat ramps and tackle shops from 2015–18. These surveys examined: • if fishing effort has increased • whether important recreational fish species were larger and more commonly caught • if fishers travelled further to fish the NFZs • if recreational fishers’ satisfaction and expectations of fishing in NFZs have changed through time. The results of these surveys were compared to a combined set of reference areas (other areas in Queensland where NFZs were not introduced in November 2015) to assess the impacts of the NFZs relative to other trends in recreational fishing through time. The full benefits of NFZs on the number and size of fish caught by recreational fishers are likely to take time to emerge, however recreational fishers are now harvesting larger barred javelin in the Rockhampton NFZ compared to the reference areas, which have not changed. In 2016 and 2017 Barramundi kept by recreational fishers in the Rockhampton NFZ were also larger than the reference areas. The size or number of fish caught by recreational fishers has not increased in the Mackay or Cairns NFZs. More fishers are travelling further to fish the Rockhampton NFZ since it was created in November 2015. This is likely due to the high levels of community engagement and awareness in Rockhampton, with the council and local groups supporting and promoting the NFZ. The number of trailers counted at the boat ramps has remained steady at all NFZs and reference areas since the NFZs were implemented. Recreational fishers’ satisfaction with fishing in the NFZs is generally positive and appears to be increasing. Overall, fishing satisfaction over the previous 12 months was greater in 2018 than in 2015 or 2016. In Cairns and Rockhampton, satisfaction was similar between years, but in Mackay satisfaction was significantly greater in 2016 and 2018 than 2015. In 2018, recreational fishers in the NFZs were more satisfied with the following activities compared to 2015 and 2016: more exciting fights with fish; the number and size of fish caught; the quality of fishing in the area. Expectations varied depending on the NFZ and frequency of fishing. Interestingly, while catching a fish is important to recreational fishers, many people stated that it is not necessary for a satisfying fishing trip. Generally, the effects of NFZs have been positive for recreational fishing. The predicted flow-on benefits of NFZs (e.g. tourism) requires that fishers are satisfied with their fishing trips, which depends largely on them catching more targeted species. As NFZs age, they might produce stronger effects on recreational fishing catches, but these effects will vary between regions due to the area covered by the NFZ, environmental factors such as floods and drought, and the reproductive and migratory capabilities of the targeted fish and their prey. Monitoring the performance of NFZs will continue as part of Fisheries Queensland’s Fisheries Monitoring program

Fisheries long term monitoring program : summary of Spanish mackerel (Scomberomorus commerson) survey results: 2004–05

Spanish mackerel, Scomberomorus commerson, is an important commercial and recreational pelagic fish species. It has similar total landings for both of these sectors on the Queensland east coast. The majority of the commercial landings come from the Lucinda area, north of Townsville, whilst the bulk of recreational catch comes from south east Queensland (Bundaberg to the Gold Coast). A preliminary stock assessment of the east coast Spanish mackerel fishery suggested that the exploitable biomass in 2002 had declined to approximately 44% of the estimated unfished biomass (Welch et al. 2002). The stock assessment recommended that fishing effort should not be increased above the 2002 level. Following the assessment, Hoyle (2002) conducted a management strategy evaluation of the east coast Spanish mackerel stock. The management strategy evaluation outlined alternative management arrangements. It proposed alternative monitoring and assessment methods to improve the resolution and utility of the information being collected. Tobin and Mapleston (2004) identified that the biological characteristics of harvested Spanish mackerel on the east coast of Queensland varied between fishing sectors and coastal regions. They found that the landed catches from the recreational sector tended to be more diverse in size and age structure. Based on Tobin and Mapleston’s findings and a management strategy evaluation of the fishery (Hoyle 2003), it was concluded that the Department of Primary Industries and Fisheries’ Long Term Monitoring Program for Spanish mackerel, which commenced in 1999, was not representative of the entire Queensland fishery. In 2004, the Long Term Monitoring Program was expanded to collect representative length, sex, and age information from both the recreational and commercial catch of Spanish mackerel from four regions along the Queensland east coast. The program also collected information on the spatial and temporal distributions of spawning. The monitoring strategy was designed from recommendations made by Sumpton and O’Neil (2004). In the 2004–05 financial year, Spanish mackerel data were collected from Cairns to the New South Wales border from the commercial and recreational fishing sectors. These results for the Queensland east coast indicate: • the majority of Spanish mackerel collected in 2004–05 were between 800 and 1100 mm fork length • a higher proportion of the recreational catch was made up of relatively small (1200 mm fork length) Spanish mackerel compared to the commercial catch. However, the sample sizes of fish collected in the recreational and commercial sectors were not equal. • similar numbers of male and female Spanish mackerel were sampled during the 2004–05 season. • the majority of female fish with ovaries in spawning condition were collected between September and December 2004 • the 3% of pre-mature fish caught by the commercial fishing sector is under the 5% reference point recommended by the Australian Government Department of the Environment and Heritage. Future monitoring will focus on increasing the number of samples collected from the recreational sector across all regions. The data summarised in this report are the results from the first year of a revised monitoring program for Spanish mackerel. This information provides biological data suitable for the stock assessment of Spanish mackerel

Comparison of the spawning patterns and fisheries biology of the sardine, Sardinops sagax, in temperate South Australia and sub-tropical southern Queensland

South Australia is the centre of the Australian distribution of Sardinops sagax, whereas southern Queensland is the northeastern edge of its local range. In South Australia, eggs were collected during all months and the peak in abundance coincided with the upwelling period in summer–autumn (January–April). In contrast, eggs were collected from southern Queensland only during winter–spring (August–November), when water temperatures fell below 23 °C. In South Australia, eggs were found throughout shelf waters, whereas in southern Queensland most eggs were collected from a small area between Noosa Heads and Caloundra. The South Australian fishery was confined mainly to the waters of southern Spencer Gulf and the Coffin Bay Peninsula, and the Queensland fishery was centred on the area of high egg density. Catch rates in the South Australian fishery were high throughout the year, whereas low catch rates were recorded in southern Queensland outside the spawning season. In South Australia, 50% of males and females were mature at approximately 146 and 150 mm FL, respectively. Over 70% of fish in all size classes collected from southern Queensland were sexually mature. Fish less than 145 mm FL comprised over 30% of South Australian catch, but less than 3% of fish taken from southern Queensland. Evidence is consistent with the hypothesis that S. sagax is a widely distributed resident of South Australian waters, but only migrates into southern Queensland during winter–spring to spawn

Freshwater flows affect the year-class strength of barramundi Lates calcarifer in the Fitzroy River estuary, Central Queensland

The age-structure of the commercial catch of barramundi in the Fitzroy River estuary, central Queensland, was examined over fi ve consecutive years and used to estimate year-class strength (= index of recruitment). Barramundi year-class strength fl uctuated and was signifi cantly and positively correlated with freshwater flow and coastal rainfall in spring and summer. General linear models were used to identify relationships between year-class strength and freshwater variables, and explained between 85 and 90% of the variation in barramundi year-class strength. The results provide further evidence that recruitment variation in barramundi: (i) persists over time; and (ii) is signifi cantly correlated with the volume to freshwater flowing into the estuary. We reviewed the evidence in support of the three causal mechanisms currently proposed to explain the relationship between year-class strength and juvenile barramundi recruitment; and propose an additional mechanism, that of enhanced growth rates and thus increased survival of young-of-the-year. Freshwater flow is an important driver of barramundi recruitment, and reduction in flow, through water abstraction or climate change, will potentially reduce barramundi stock size available for human harvest. As such, fi shery stock assessments for barramundi should explicitly consider the impacts of variable flow on annual recruitment and stock dynamics

The hairpin structure of the (6)F1(1)F2(2)F2 fragment from human fibronectin enhances gelatin binding

The solution structure of the (6)F1(1)F2(2)F2 fragment from the gelatin-binding region of fibronectin has been determined (Protein Data Bank entry codes 1e88 and 1e8b). The structure reveals an extensive hydrophobic interface between the non-contiguous (6)F1 and (2)F2 modules. The buried surface area between (6)F1 and (2)F2 (∼870 Å(2)) is the largest intermodule interface seen in fibronectin to date. The dissection of (6)F1(1)F2(2)F2 into the (6)F1(1)F2 pair and (2)F2 results in near-complete loss of gelatin-binding activity. The hairpin topology of (6)F1(1)F2(2)F2 may facilitate intramolecular contact between the matrix assembly regions flanking the gelatin-binding domain. This is the first high-resolution study to reveal a compact, globular arrangement of modules in fibronectin. This arrangement is not consistent with the view that fibronectin is simply a linear ‘string of beads’

Freshwater-flow requirements of estuarine fisheries in tropical Australia: a review of the state of knowledge and application of a suggested approach

The freshwater-flow requirements of estuarine fisheries in tropical areas are reviewed, with reference to species important to fisheries in northern Australia. Fisheries production, in terms of catch, is often elevated during, or as a consequence of, years with higher river flow, but the causality of these relationships often remains unproven. Scientific information on the freshwater-flow requirements important to fisheries production is increasingly being sought during the planning, allocation and management of water resources within Australia and in other countries around the world. Frequently, such advice is based on the analysis of catch and freshwater flow (or rainfall), or on life-history information. Clarifying fisheries-specific goals of water management would assist in prioritising research into the freshwater-flow requirements of estuarine fisheries. A framework that integrates life-history information and correlative analyses is suggested to assist in understanding the freshwater-flow requirements of estuarine fisheries. The framework is also useful in identifying knowledge gaps and pertinent research questions. The approach is illustrated through its application to identifying key freshwater-flow events likely to be important for fisheries production in a dry tropical estuary in Queensland, Australia

Effects of freshwater flow on the year-class strength of a non-diadromous estuarine finfish, king threadfin (Polydactylus macrochir), in a dry-tropical estuary

The year-class strength of the commercial catch of king threadfin (Polydactylus macrochir (Gunther, 1876)) was correlated with freshwater flows into a dry-tropical estuary over five consecutive years. The year-class strength of king threadfin, a non-diadromous estuarine species, fluctuated and correlated significantly with freshwater flow and coastal rainfall in spring and summer; a result similar to that found for the catadromous barramundi (Lates calcarifer) within the same estuarine system. All sub-sets general linear models were used to screen relationships between year-class strength and freshwater variables. King threadfin spawn from spring to summer in north-eastern Australia, when hydrological conditions adjacent to estuaries have high salinities and are optimal for egg and post-larval survival. Young-of-the-year enter estuaries during the wet season, enabling them to take advantage of salinity gradients and the seasonal blooms in prey species such as Acetes spp. and juvenile penaeids that are accentuated in wet years. Freshwater flows in spring and summer are important drivers of the year-class strength of estuarine finfish, and reduction in these flows, through the development of water infrastructure and abstraction or long-term climate change, will potentially reduce the size of the population of estuarine fish available for human harvest