Neil Loneragan

The brown-marbled grouper (Epinephelus fuscoguttatus), a high-value species in international trade, has experienced population declines due to intensive fishing. It is one of 12 grouper and snapper species prioritized for management in Saleh Bay, West Nusa Tenggara, Indonesia. This study analyzed catch data (2017–2022) and biological samples (2020–2021) to update key life history parameters, including natural mortality, von Bertalanffy growth parameters, asymptotic length, and size at maturity. Growth was estimated using an ELEFAN-optimized model applied to catch length–frequency data, while maturity was determined through macroscopic examination of gonads. The updated estimates (L50 = 488 mm for both sex; L95 = 568 mm for females and 616 mm for males) were incorporated into a length-based spawning potential ratio (SPR) assessment. Annual SPR values ranged from 0.13 to 0.28, substantially higher than previous estimates of 0.05–0.07, mainly due to the lower L50 used in this study. Despite this improvement, SPR values remain below the management target of 0.30 for groupers and snappers in Saleh Bay. Limited biological samples, particularly the scarcity of larger individuals and males, introduce uncertainty in the estimates. These findings emphasize the value of locally derived life history information and highlight the need for continued biological sampling to refine growth and reproductive parameters and support sustainable fisheries management.

Offshore wind farms (OWF) are rapidly emerging as essential infrastructure for transitioning to renewable energy, and this has been particularly important in the waters of China. To evaluate the impact of OWF construction, Ecopath models were developed for an OWF area and, separately, for a nearby control area, using biological and environmental survey data collected in 2022 and 2023. Functional groups were initially categorized into soft-substrate and hard-substrate (turbine monopiles) communities. The results showed that the colonization of turbine monopiles by sessile organisms significantly increased the productivity of most fish functional groups in the OWF area compared to the control. The OWF ecosystem exhibited higher trophic levels, especially for macroinvertebrates and fish, and a more complex food web with enhanced detritus flow than the control area. Mixed trophic impact analysis indicated a shift from a pelagic to a benthic-dominated system following OWF construction. Notably, detritus accounted for 52 % of total system throughput in the OWF area, compared to 38 % in the control area, highlighting a transition toward detritus-based energy flow. Furthermore, the OWF system showed significantly higher values for total system throughput, omnivory index, connectivity, Finn’s cycling index, and ascendency. Overall, the presence of the OWF resulted in significant changes in the trophic flow and system structure, creating a more complex, mature, and stable benthic-dominated ecosystem. These findings indicate that the establishment of OWF enhances both the structural composition and functional dynamics of surrounding marine ecosystems.

This feature reports on a roundtable session on aquaculture-aided fisheries enhancement, restoration, and conservation that was held at the 2024 Ninth World Fisheries Congress. The session aimed to foster constructive dialogue on the use of hatcheries and stocking programs for conservation purposes, a topic sometimes referred to as the “third rail” of fisheries management. The standing room-only session drew participants from around the world and a wide variety of aquaculture contexts. Using pre-session reflections, in-session discussions, and real-time feedback tools, the session encouraged open discussions on key challenges and promising practices and policies within ­aquaculture-aided enhancement, restoration, and conservation. Participants identified both established challenges and novel perspectives, particularly with respect to the sociocultural aspects of hatchery practices and the need for policies that acknowledge local contexts. The organizers considered the session to be a step forward in developing a robust and diverse community of practice interested in aquaculture-aided approaches.

Coastal environments and their associated biota provide numerous environmental, economic and societal services. Cockburn Sound, a temperate embayment on the lower west coast of Western Australia, is immensely important for the State and adjacent capital city of Perth. However, urbanisation and associated terrestrial and marine development has the potential to threaten this important ecosystem. This study collated published and unpublished data to review the current state of the ecological resources of Cockburn Sound and describe how they have changed over the past century. Post-WWII, the embayment began undergoing pronounced anthropogenic changes that limited oceanic water exchange, increased nutrient load, modified benthic habitats and increased fishing pressure. The most visual outcome of these changes was substantial eutrophication and the loss of 77% of seagrass habitats. However, the increased primary productivity from elevated nutrient inputs produced high commercial fishery yields of up to ~1,700 t in the early 1990s before improved wastewater regulation and restricted fishing access steadily reduced commercial catches to ~300 t in recent years. Despite substantial anthropogenic-induced changes, Cockburn Sound has remained a diverse and ecologically important area. For example, the embayment is a key spawning area for large aggregations of Snapper, is a breeding and feeding site for seventeen marine bird species (including Little Penguins) and, is frequented by numerous protected species such as pinnipeds, dolphins, and White and Grey Nurse sharks. In recent decades, numerous projects have been initiated to restore parts of Cockburn Sound with mixed success, including seagrass transplantation, deployment of artificial reefs and stocking of key fish species, mainly Snapper. Nevertheless, while still biodiverse, there are signs of considerable ecological stress from escalating anthropogenic pressures and the cumulative impacts of ongoing and future developments, including climate change, which may severely impact the functioning of this important ecosystem.

Cockburn Sound is one of the most intensively used marine areas in Western Australia and has a history of major industrial development and nutrient pollution. This has contributed to significant losses of seagrass meadows (∼80%) between the 1950s and early 2000s and declines in exploited fish species such as pink snapper (Chrysophrys auratus) and blue swimmer crab (Portunus armatus). However, Cockburn Sound remains highly valued by the community for its ecological, economic, and recreational attributes. In this study, we developed a quantitative ecosystem model using Ecopath with Ecosim software to identify ecological indicators for ecosystem performance and elucidate how the system functions, including: (1) biomass flow in the food web; (2) identifying keystone species; and (3) defining the ecological network. We defined 73 functional groups based on both local biological surveys from a major research program in 2021-22 and expert consultation. The model identified the ecological role of keystone groups defined as structuring species by processes associated with predation (top-down forces) with sharks, bottlenose dolphin (Tursiops truncates), Australian sea lion (Neophoca cinerea), and cormorants (Phalocrocorax spp.) as functionally important species in the system. The results from the mixed trophic impact (MTI) analysis indicated that commercial and recreational fisheries did not have a major impact on the biomass of fished species, but some indirect impacts were found between the squid jigging fishery and dolphins through shared food resources (squid). The ecological indicators generated in this study provide baseline information on the trophic structure, energetics, and function of the Cockburn Sound ecosystem, and can be used to inform managers on how the system may respond to stressors and disturbances e.g., infrastructure development and climate change, and be used in evaluating alternative management strategies. The Ecopath model highlighted the complexity of Cockburn Sound’s ecology, showing the role of higher and lower trophic groups in this food web. This is particularly important because understanding the processes and interactions within the system can support plans for conservation and management.
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This study estimated the growth of tagged, hatchery-reared Haliotis laevigata (Greenlip abalone) released (“seeded”) on artificial habitats (Abitats) in Flinders Bay, south-western Australia. It also evaluated a mark in the shell detected after transferring abalone from the hatchery to the ocean as a predictor of the size-at-release for the abalone. The research was carried out as part of commercial operations on the sea ranch which limited some of the data collected. A total of 117 tagged H. laevigata were released on the Abitats and harvested across three areas (lines). Growth in shell length (SL) was significantly slower on one line (1.96 mm month-1) than the others (2.33 mm month-1 and 2.44 mm month-1), possibly due to different pre-seeding histories. Slower growing abalone were retained in the hatchery for an additional 74 days compared to the faster growing abalone. However, growth in wet weight did not differ significantly among lines (2.22 g month-1). This study provides the first estimates of the different shell-length characteristics for juvenile abalone: the mean (± 1 SE) SL: shell width ratio was 1.31 ± 0.005 and the SL: shell depth ratio was 4.94 ± 0.057, much greater than these ratios for mature H. rubra in southern Australia. The hatchery mark at harvest was a significant linear predictor of the shell length at seeding and was still present in abalone at harvest size (~100 mm SL), providing a way of estimating growth in H. laevigata on the sea ranch without the need for tagging.

Amberjacks in the family Carangidae are large, carnivorous pelagic fish that are highly targeted by fisheries globally. Seriola lalandi and Seriola quinqueradidata co-occur seasonally in the northern Yellow Sea and are caught by recreational fishers. This study used stomach content analysis (SCA) and stable isotope analysis (SIA) of δ13C and δ15N from liver and muscle tissues to investigate the dietary composition (including ontogenetic shifts), trophic niche breadth and overlap of these two species. This combination of techniques provides information on immediate diet (SCA), and short-term (~3 months, liver SIA) and longer-term (~5-6 months, muscle SIA) trophic assimilation. Both Seriola species were carnivorous, mainly feeding on fish, particularly the anchovy Engraulis japonicus, as well as crustaceans and cephalopods. Their diet shifts to larger-sized fish prey (e.g. mackerel Scomber japonicus) with ontogeny. Differences in δ13C values of liver and muscle were detected for both species, and for δ15N values for S. lalandi. Interspecific differences in δ15N and δ13C values for muscle and δ15N for liver were detected but no differences in δ13C values for liver tissue. δ15N values for liver and muscle were correlated with fork length in both species, suggesting a shift to higher-trophic level prey with ontogeny. Seriola lalandi had a broader trophic niche than S. quinqueradidata, indicating that the former species had a higher trophic diversity. Isotopic niche overlap between species were greater for the shorter-term liver (0.81) than longer-term muscle (0.39), which might reflect different overwintering habitats for the species or temporal-spatially partitioning in their pelagic habitat use during their reproductive migration. The study facilitated a better understanding of the trophic dynamics of sympatric Seriola species and provides information for implementing ecosystem-based fisheries management for these highly targeted species.

Introduction
Over 100 years ago, McAtee (1912) set out to settle once and for all the debate on whether data on the contents of animal stomachs should be presented as percentage-by-bulk (the volume of each prey type; percentage volume or volumetric percentage) or numerically (based on counts of the number of individuals in each food type; numerical percentage). He didn’t succeed, with numerous other authors, including Pinkas et al. (1971) and Hart et al. (2002), also considering the question many years later. Indices combining multiple methods were proposed, while others argued strongly for presentation of the different methods individually to facilitate combining data across multiple studies in meta-analyses (Buckland et al. 2017). The story continues in Chapter 3, where the authors wrestle with the practical problems of identifying foods from stomach contents and quantifying the findings. The persistence of the debate confirms the ongoing interest in animal diets, acknowledging that there is still much discussion on how best to describe and quantify their important features. In this chapter we first outline the compelling reasons why it is important to study animal diets, grouping them under the themes of natural history, ecosystem function, food selection behaviour and practical applications. We then turn to the question of how to study animal diets, which is the primary focus of the book, explaining how the remaining chapters are structured to answer this question.

Quantifying Diets of Wildlife and Fish presents different techniques available to study animal diets. Ecologists determine animal diets to build natural history knowledge, test hypotheses in ecological theory and make informed management decisions for important ecosystems. Many researchers use techniques traditionally applied to the animals they study, rather than techniques with the greatest potential for the aims of each project. In an effort to encourage researchers to consider new approaches, this book focuses on the techniques, rather than on particular groups of organisms or specific environments.

With contributions from leading ecologists, chapters explore experimental design, observational techniques (including new technologies), stomach contents and faecal analysis, eDNA, tracers and stable isotopes. They also cover the latest multivariate methods of analyses suitable for describing animal diets and feeding relationships, as well as testing hypotheses relevant to ecological theory, environmental management and biological conservation. The expert knowledge provided will encourage readers to look beyond the boundaries of their specialties, assist in testing important hypotheses and provide insights into management problems. The examples in this book cover a range of vertebrates and invertebrates, as well as different environments, to open these methods up for novice ecologists and stimulate lateral thinking in more experienced researchers.