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.

Due to human activity, ecosystems are exceeding their ecological thresholds and shifting into undesired alternative stable states with new ecological configurations. Despite their purported ubiquity, it is uncertain whether estuaries can exist in multiple stable states. We use data from a 3.5-year study of invertebrate communities in an Australian estuary that is usually closed to the ocean to test for their existence. Sampling spanned a 1.5-year period of hypersalinity (>40 ppt) during a prolonged estuary closure, where salinity reached 122 ppt, and for 2 years during and after the estuary opened to the ocean when salinities were mesohaline (5–19 ppt). Two distinct community states occurred before and after the sandbar breached, with an intermediary period of invertebrate community impoverishment due to sediment scouring. During the closure, the community was simple (average of 1 taxa) and dominated by larvae of terrestrial insects, most notably the halotolerant, non-biting midge Tanytarsus barbitarsis. After opening, the richness and abundance of invertebrates increased (average of 4 taxa and 84 individuals 100 cm−2) as polychaetes, molluscs and crustaceans colonised the estuary, although recovery was incomplete according to previous species records. Duration of closure and salinity were the strongest drivers of composition. This study, together with evidence from the literature, suggests a salinity threshold of 60–65 ppt between states. These empirical data meet key criteria of alternative states, i.e. a clear transition between two distinct self-sustaining communities, indicating a regime shift triggered by an exogenous event. Our findings suggest that temporarily open and closed estuaries can exist in alternative stable states, with prolonged closures, hypersalinity, and sandbar breaching being key determinants of the switch between states. This situation may apply to other low-inflow estuarine systems, particularly in arid, semi-arid, or seasonally arid climates, and may become more frequent due to human-induced climate change.
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Small-scale tropical fisheries are complex systems that utilize multiple fishing gears to target various species. In this study, we investigated small-scale reef and demersal fisheries in Saleh Bay, Indonesia, using catch and effort data from 2016 to 2019, where 57.7 percent of the catch was grouper (serranids) and snapper (lutjanids). Despite the complexity (75 documented species and eight fishing methods), this fishery is characterized by the catches of four dominant species: leopard coral grouper (Plectropomus leopardus), orange-spotted-grouper (Epinephelus coioides), spotted coral grouper (P. maculatus), and malabar blood snapper (Lutjanus malabaricus). The species caught varied among fishing methods. Over 90% of the catch was attributed to three primary fishing methods: bottom longline, speargun, and handline. Multivariate analyses found that fishing depth, season, and/or year significantly influenced the catch composition for each of these fishing methods. Fishing activities exhibit a temporal pattern influenced by monsoonal seasons. Results also suggest that fishers employ specialized fishing tactics by targeting high-value species to maximize their profits. This study recommends a management strategy of focusing on monitoring and managing the three main fishing gears and four important species during their peak seasons to reduce some of the complexity and management costs.

Baited remote underwater video (BRUV), with its non-destructive nature and ease of replication, is an effective and widely used method to record the relative abundance and behavior of aquatic fauna. However, the effectiveness of BRUVs for investigating the structural and functional diversity of mobile fauna on artificial reefs has not been fully evaluated. In China artificial reefs form an important component of very extensive marine ranching systems along the coast. This study used BRUVs and baited fish traps (traps), a traditional and popular fishing gear in the coastal waters of northern China, over six months to quantify the mobile fauna around artificial reefs and adjacent natural substrate (“control”) and compared the richness, abundance, community composition and functional diversity of reefs and control areas and BRUVs and traps. A significantly greater number of species and relative abundance was recorded using BRUVs than traps. Significant differences in faunal composition were detected between the two methods (BRUVs, traps), the two habitats (artificial reef, control) and the seven sampling occasions. Measures of functional diversity were also all significantly higher using data derived from BRUVs than traps. The weighted average analysis of functional traits revealed that those related to feeding and space use were more diverse from BRUVs. These results indicate that BRUVs provided a more complete representation of the mobile fauna than traps and show great potential for fishery-independent monitoring of marine ranching in China.
•First use of baited remote underwater videos (BRUVs) for investigating the community dynamics of mobile fauna in China.•Higher number of species and relative abundance recorded on BRUVs than in fish traps.•Measures of community function: richness, evenness, and divergence were greater using BRUVs.•Broader range of functional traits and IUCN-listed threatened species recorded on BRUVs.