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Using estimates of the primary production required (PPR) to support fisheries catches (a measure of the footprint of fishing), we analyzed the geographical expansion of the global marine fisheries from 1950 to 2005. We used multiple threshold levels of PPR as percentage of local primary production to define 'fisheries exploitation' and applied them to the global dataset of spatially-explicit marine fisheries catches. This approach enabled us to assign exploitation status across a 0.5° latitude/longitude ocean grid system and trace the change in their status over the 56-year time period. This result highlights the global scale expansion in marine fisheries, from the coastal waters off North Atlantic and West Pacific to the waters in the Southern Hemisphere and into the high seas. The southward expansion of fisheries occurred at a rate of almost one degree latitude per year, with the greatest period of expansion occurring in the 1980s and early 1990s. By the mid 1990s, a third of the world's ocean, and two-thirds of continental shelves, were exploited at a level where PPR of fisheries exceed 10% of PP, leaving only unproductive waters of high seas, and relatively inaccessible waters in the Arctic and Antarctic as the last remaining 'frontiers.' The growth in marine fisheries catches for more than half a century was only made possible through exploitation of new fishing grounds. Their rapidly diminishing number indicates a global limit to growth and highlights the urgent need for a transition to sustainable fishing through reduction of PPR.

Swordfish ( Xiphias gladius ) are a widely distributed (45°N–45°S) large pelagic fish targeted by fisheries worldwide. Swordfish that occur at high latitudes tend to disproportionately be large adults, so their movements have implications for population dynamics and fisheries management. In the southwest Pacific, little is known about this subset of the stock and existing evidence suggests limited movement from the subtropics into cooler high latitude waters. Here, we capitalize on the recent emergence of a recreational swordfish fishery off temperate southeast Australia to characterize movements of swordfish caught in the fishery with pop-up satellite archival transmitting tags. Data were recovered from tags deployed for 56–250 days on 11 swordfish (50–350 kg) tagged between 38 and 43°S in the western Tasman Sea. Five swordfish entered the Coral Sea (< 30°S), with four reaching north to 11–24°S, up to 3275 km away from location of capture. Behavior modelling suggests these four individuals rapidly transited north until encountering 23–27 °C water, at which point they lingered in the area for several months, consistent with spawning-related partial migration. One migrating swordfish still carrying a tag after the spawning season returned to ~ 120 km of its release location, suggesting site fidelity. Movements toward the central south Pacific were confined to two individuals crossing 165°E. Swordfish predominantly underwent normal diel vertical migration, descending into the mesopelagic zone at dawn (median daytime depth 494.9 m, 95% CI 460.4–529.5 m). Light attenuation predicted daytime depth, with swordfish rising by up to 195 m in turbid water. At night, swordfish were deeper during the full moon, median night-time depth 45.8 m (37.8–55.5) m versus 18.0 m (14.9–21.8) m at new moon. Modelling fine-scale (10 min −1 ) swordfish depth revealed dynamic effects of moon phase varying predictably across time of night with implications for fisheries interactions. Studying highly migratory fishes near distribution limits allows characterization of the full range of movement phenotypes within a population, a key consideration for important fish stocks in changing oceans.

Catch-based fisheries data can mislead It is often claimed that industrial fisheries are 'fishing down marine food webs' by depleting top predators (such as tuna) before targeting their prey species (plankton feeders such as oysters and sardines). But new global data reveal little evidence for this pattern of sequential depletion, working downwards through the trophic levels of the marine ecosystem. Rather, comparison of model predictions of the widely adopted marine indicator, mean trophic level (MTL) derived from reported catches, with actual ecosystem MTL suggests that fishing has intensified throughout all levels of marine food webs. The trend can be masked by the use of data based on catches, and if we are to accurately monitor future fisheries collapses — and recoveries — we may need to shift focus from catch-based indicators to tracking true abundance trends using scientific surveys and models. The health of marine ecosystems is traditionally assessed by measuring the mean trophic level (MTL) of fishery catches. These authors model catch MTL and actual ecosystem MTL, and show that the former is not a good measure of the latter. They then show that MTLs have actually been increasing in recent years, but that fisheries are still at risk of collapse because all trophic levels have been similarly affected. Biodiversity indicators provide a vital window on the state of the planet, guiding policy development and management 1 , 2 . The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and plankton-feeders 3 , 4 , 5 . This indicator underpins reported trends in human impacts, declining when predators collapse (“fishing down marine food webs”) 3 and when low-trophic-level fisheries expand (“fishing through marine food webs”) 6 . The assumption is that catch MTL measures changes in ecosystem MTL and biodiversity 2 , 5 . Here we combine model predictions with global assessments of MTL from catches, trawl surveys and fisheries stock assessments 7 and find that catch MTL does not reliably predict changes in marine ecosystems. Instead, catch MTL trends often diverge from ecosystem MTL trends obtained from surveys and assessments. In contrast to previous findings of rapid declines in catch MTL 3 , we observe recent increases in catch, survey and assessment MTL. However, catches from most trophic levels are rising, which can intensify fishery collapses even when MTL trends are stable or increasing. To detect fishing impacts on marine biodiversity, we recommend greater efforts to measure true abundance trends for marine species, especially those most vulnerable to fishing.

Cephalopods, especially squids, are believed to have a structuring role in marine ecosystems as a link between different trophic levels, primarily due to their voracious prey consumption and high production rate. Cephalopod ecology, however, is still poorly understood as observational studies often give highly uncertain and variable results due to the peculiarities of cephalopod behaviour and biology, and their responsiveness to external drivers. This review evaluates our representation of cephalopods in ecosystem models and the insights given by these models on the role of cephalopods in our oceans. We examined ecosystem models from 13 regions to analyse the representation of cephalopods and compared their results to local trophic studies. Our analysis indicated that most ecosystem models inadequately include cephalopods in terms of model structure and parametrization; although some models still have the capacity to draw valuable conclusions regarding the impact and role of cephalopods within the system. Oceanic squid species have a major role linking trophic levels and food webs from different habitats. The importance of neritic species varies locally, but generally cephalopods have a substantial impact via their consumer role. To better understand the ecological role of cephalopods, improved representation of these species in ecosystem models is a critical requirement and could be achieved relatively easily to more accurately articulate the mechanisms regulating the ecological role of cephalopods.

The growing human population must be fed, but historic land-based systems struggle to meet expanding demand. Marine production supports some of the world’s poorest people but increasingly provides for the needs of the affluent, either directly by fishing or via fodder-based feeds for marine and terrestrial farming. Here we show the expanding footprint of humans to utilize global ocean productivity to feed themselves. Our results illustrate how incrementally each year, marine foods are sourced farther from where they are consumed and moreover, require an increasing proportion of the ocean’s primary productivity that underpins all marine life. Though mariculture supports increased consumption of seafood, it continues to require feeds based on fully exploited wild stocks. Here we examine the ocean’s ability to meet our future demands to 2100 and find that even with mariculture supplementing near-static wild catches our growing needs are unlikely to be met without significant changes. Global landings of wild-caught seafood have plateaued in recent years. Analysing trends in global fisheries catches, Watson et al. find that distance between sourcing and consumption has increased steadily since the 1950s, with ocean productivity unlikely to meet current consumption rates by 2100.

Recreational fisheries hold immense ecological, social, and economic value. The management of these fisheries is increasingly important as we move forward in the Anthropocene. Recreational fisheries managers face several challenges as fisheries often involve diverse social and ecological systems comprised of complex feedback and stakeholder motivations and needs. Here, we used a horizon scanning exercise to yield 100 research questions related to recreational fisheries science and management in the Anthropocene. Initial research questions (n = 205) were collected from recreational fisheries experts (i.e., stakeholders, managers, researchers) from various sectors (i.e., industry, government, NGOs) and geographic locations (14 countries: Australia, Brazil, Canada, Czech Republic, Germany, Italy, New Zealand, Norway, South Africa, Spain, Sweden, Switzerland, United Kingdom, USA). These questions were subsequently categorized, thematized, and refined by our authorship team, eventually yielding what we considered to be the top 100 research questions of relevance to management of recreational fisheries. The key themes include: human dimensions; bioeconomics; resource monitoring and data acquisition; governance; management—regulatory actions; management—stock and habitat enhancement; catch-and-release; impacts of recreational fisheries on populations, communities and ecosystems; threats and sustainability; and angler outreach, education and engagement. It is our intention that this comprehensive and forward-looking list will create a framework to guide future research within this field, and contribute to evidence-based recreational fisheries management and policy.

Abstract Fishing is one of the most sustained forms of human–wildlife interaction and can alter trait distributions through selective harvest and repeated disturbance. Such changes, whether plastic or evolutionary, may alter productivity, resilience, and recovery in exploited species. The sand flathead (Platycephalus bassensis), a benthic ambush predator with strong site fidelity, supports lutruwita (Tasmania’s) largest recreational fishery and is exposed to contrasting levels of fishing pressure across its range. In southern Tasmania, fishing mortality exceeds natural mortality more than fivefold and biomass has fallen below 20% of unfished levels, while northern regions remain comparatively lightly fished. This regional contrast offers a natural setting in which to investigate whether sustained harvest is associated with regional differences in physiology and behaviour, and whether such variation is more consistent with fishing pressure, environmental conditions, or their interaction. We compared mass-specific metabolic rate, boldness, and size-at-age between sand flathead from heavily and lightly fished regions. Metabolic rate was measured using intermittent flow-through respirometry, and boldness was quantified in a shuttlebox based on exploration latency and bait strikes. Fish from the heavily fished south exhibited smaller size-at-age, a 62% higher mean metabolic rate, and a transient post-capture elevated metabolic rate consistent with greater metabolic reactivity or stress responsiveness, whereas boldness did not differ between regions. Our findings align with other exploited systems and raise the possibility that trait diversity of sand flathead in southern regions of Tasmania have been shaped, at least in part, by fisheries selection. We discuss the relevance of these results for fisheries management and emphasize the importance of assessing trait variation in wild populations, where expression is likely shaped by the interactive effects of fishing pressure and local ecological conditions. Lay Summary We compared traits of sand flathead from heavily and lightly fished regions of Tasmania. Fish from heavily fished areas were smaller for their age and had higher metabolic rates, showing that fish populations can differ in growth and energy use across regions with contrasting fishing pressure.

Citizen science programs are effective methods to collect large volumes of data to assist researchers in monitoring ecological environments. As species shift their distributions globally due to climate change, the use of citizen science data to detect these shifts is increasing. Using targeted citizen science programs to collect data on these species could provide information on range edges to inform species distribution modelling. Currently, species distribution models (SDMs) often rely on large data repositories that may lack observations, and hence ability, to detect changes at the range edge. Here, we developed a SDM to compare traditional data repository observations with targeted citizen science data at the southern distribution limit of two recreationally important marine fish in Tasmania, Australia to investigate the potential change in spatial predictions at their range edge. The SDM using the targeted citizen science data in addition to traditional observation data improved the representation of species by 2.3 and 52.7% and increased the southern distribution of the species by 277 and 438 km, for snapper and King George whiting, respectively. Future (centred around 2050 under IPCC RCP 8.5) habitat suitability was predicted to increase more over the winter season, with implications for species overwintering and persistence of populations. The use of citizen science data allowed for the modelling of historical and future change for two range-extending species, an outcome possible due to the collaboration of two citizen science programs that collected observational data on the target species. Species range shifts will require ongoing monitoring and we have demonstrated that complimentary citizen science initiatives are effective in capturing occurrences of species at their range edge. Increasing collaboration between programs may further increase data collection efforts and provide the knowledge to create a hub for these data to be used more efficiently in the future.

Long-term shifts in environmental conditions driven by climate change are predicted to persistently modify the distribution of a multitude of species. These range shifts can have significant effects on the functioning of ecological communities. Ocean warming along the southeast coast of Australia has seen a polewards shift in the distribution of the long-spined sea urchin Centrostephanus rodgersii . Barren areas formed by the destructive overgrazing of kelp beds by invading C. rodgersii are associated with a dramatic loss of habitat, species diversity and productivity. The ongoing range expansion of C. rodgersii will further increase sea urchin densities along the south eastern coast of Tasmania, where ‘incipient’ barrens have started to appear. As restoration of sea urchin barrens over a large-scale is costly and hard to achieve, effective management needs to focus on preventing further formation of extensive barrens. This study examines whether systematic culling of C. rodgersii in spatially discrete areas is effective to control their abundance. We show that systematic culling was highly effective in significantly reducing the mean density and aggregation of urchins in a discrete area which persisted for at least 12 months. Notably, there was no significant difference in the reduction of urchin density and aggregation when plots were culled twice rather than once. There was however an edge effect indicating a slow incursion of urchins back into the treatment plots. We also show that divers follow a classic prey-predator interaction with culling efficiency increasing with urchin density. Ultimately our results demonstrate that systematic culling is an effective method for controlling urchin abundance in discrete areas. The high cost and logistical constraints limit the application of a culling programme over large areas of reef. Culling, therefore, needs to be considered along with other management measures to control the effects of overgrazing by urchins over large scales.

Habitat characteristics greatly influence the patterns of distribution and abundance in scallops, providing structure for the settlement of spat and influencing predation risk and rates of survival. Establishing scallop-habitat relationships is relevant to understanding the ecological processes that regulate scallop populations and to managing critical habitats. This information is particularly relevant for the D'Entrecasteaux Channel, south-eastern Tasmania (147.335 W, 43.220 S), a region that has supported significant but highly variable scallop production over many years, including protracted periods of stock collapse. Three species of scallops are present in the region; the commercial scallop Pecten fumatus, the queen scallop Equichlamys bifrons, and the doughboy scallop Mimachlamys asperrima. We used dive surveys and Generalized Additive Modelling to examine the relationship between the distribution and abundance patterns of each species and associated habitat characteristics. The aggregated distribution of each species could be predicted as a function of sediment type and species-specific habitat structural components. While P. fumatus was strongly associated with finer sediments and E. bifrons with coarse grain sediments, M. asperrima had a less selective association, possibly related to its ability to attach on a wide range of substrates. Other habitat characteristics explaining P. fumatus abundance were depth, Asterias amurensis abundance, shell and macroalgae cover. Equichlamys bifrons was strongly associated with macroalgae and seagrass cover, whereas M. asperrima abundance was greatly explained by sponge cover. The models define a set of relationships from which plausible hypotheses can be developed. We propose that these relationships are mediated by predation pressure as well as the specific behavioural characteristics of each species. The findings also highlight the specific habitat characteristics that are relevant for spatial management and habitat restoration plans.