Search

Abstract: We used the Ecopath with Ecosim software to develop a trophic mass-balance model of the eastern Great Australian Bight ecosystem, off southern Australia. Results provide an ecosystem perspective of Australia''s largest fishery, the South Australian sardine fishery, by placing its establishment and growth in the context of other dynamic changes in the ecosystem, including: the development of other fisheries; changing abundances of apex predator populations and oceanographic change. We investigated the potential impacts of the sardine fishery on high tropic level predators, particularly land-breeding seals and seabirds which may be suitable ecological performance indicators of ecosystem health. Results indicate that despite the rapid growth of the sardine fishery since 1991, there has likely been a negligible fishery impact on other modelled groups, suggesting that current levels of fishing effort are not impacting negatively on the broader ecosystem structure and function in the eastern Great Australian Bight. Results highlight the importance of small pelagic fish to higher trophic levels, the trophic changes that have resulted from loss and recovery of apex predator populations, and the potential pivotal role of cephalopod biomass in regulating ‘bottom-up’ trophic processes. The ability to resolve and attribute potential impacts from multiple fisheries, other human impacts and ecological change in this poorly understood region is highlighted by the study, and will be critical to ensure future ecologically sustainable development within the region. [Copyright &y& Elsevier]

Helicopter-based shooting is an effective management tool for large vertebrate pest animals. However, animals in low-density populations and/or dense habitat can be difficult to locate visually. Thermal-imaging technology can increase detections in these conditions. We used thermal-imaging equipment with a specific helicopter crew configuration to assist in aerial culling for feral pigs (Sus scrofa) and fallow deer (Dama dama) in South Australia in 2021. Seventy-two percent of pigs and 53% of deer were first detected in dense canopy/tall forest habitat. Median time from the first impact shot to incapacitation was < 12 s. The culling rate (animals hour -1 ) doubled compared to visual shoots over the same populations and the wounding rate was zero resulting in a incapacitation efficiency of 100%. The crew configuration gave the shooter a wide field of view and the thermal operator behind the shooter provided essential support to find new and escaping animals, and to confirm species identification and successful removal. The crew configuration allowed for successful target acquisition and tracking, with reduced target escape. The approach can increase the efficiency of aerial culling, has the potential to increase the success of programs where eradication is a viable option, and can improve animal welfare outcomes by reducing wounding rates and the escape of target animals., (© 2023. Crown.)

Life-history characteristics of six tropical Lethrinus species sampled from the Great Barrier Reef World Heritage Area were compared. Two species groups were identified based on fork length (LF ): large species with maximum LF > 640 mm (longface emperor Lethrinus olivaceus, yellowlip emperor Lethrinus xanthochilus and spangled emperor Lethrinus nebulosus) and small species with maximum LF < 480 mm (Pacific yellowtail emperor Lethrinus atkinsoni, pink ear emperor Lethrinus lentjan and ornate emperor Lethrinus ornatus). Lifespan was not correlated with LF . Early growth for all species was rapid and similar during the first few years of life, but coefficients of the von Bertalanffy growth function varied considerably among species. Growth also differed between sexes for L. atkinsoni. Reproductive characteristics varied among species, with peak periods of spawning occurring in November to December for L. atkinsoni, July to August for L. nebulous, September to October for L. olivaceus and a protracted season for L. lentjan, although fewer samples were available for the last two species. Sex-specific LF and age distributions and gonad histology of L. lentjan were suggestive of a functional protogynous reproductive pattern, as observed in other lethrinids. Gonad histology indicated non-functional protogynous hermaphroditism for L. atkinsoni and L. nebulosus. The diversity of life histories among these closely related species emphasizes the difficulty in devising single management strategies appropriate for multi-species fisheries and illustrates the importance of understanding species-specific life histories to infer responses to exploitation., (© 2013 The Authors. Journal of Fish Biology © 2013 The Fisheries Society of the British Isles.)