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1. In response to multiple Stressors, coral reef health has declined in recent decades, with reefs exhibiting reduced living coral and structural complexity, and a concomitant rise in the dominance of algal resources. Reef degradation alters food availability and reduces the diversity and density of refuges for prey. These changes affect predator-prey interactions and can have cascading impacts on food webs and fisheries productivity. 2. We use a size-based ecosystem model of coral reefs that incorporates the influence of structural complexity, benthic primary production and detrital recycling to explore how predator-prey interactions and fisheries productivity respond to a gradient of reef degradation. 3. We show that fisheries productivity overall may be robust to initial stages of reef degradation because the benefits of increased resources outweigh the costs of moderate refuge decline. However, the assemblage composition and size structure of reef fish will differ on degraded reefs, with herbivores and invertivores contributing relatively more to productivity. 4. More significant losses of refuges associated with the erosion of structural complexity correspond to fisheries productivity losses of at least 35% compared to healthy reefs. 5. Synthesis and applications. Our model provides fisheries managers with quantitative predictions about how fisheries productivity may change in response to the ongoing degradation of coral reefs. We predict an initial increase in productivity at intermediate reef degradation, followed by a drastic decline when structural complexity is lost. We also capture subtle changes to potential catch composition and fish size, including increases in smaller herbivorous and invertivorous fish from degraded reefs, which will undoubtedly impact fisheries value. On the one hand, our results reassure for continued productivity in the short term, but on the other, we warn against complacency. Management must change to capture any potential benefits to fisheries, and long-term sustainability still depends on the maintenance of complex coral reef habitats.

This study investigated artisanal fishing activity near sea cages in Güllük Bay in the southeastern Aegean Sea based on dockside sampling with local fishermen. The daily fishing activity of bogue Boops boops gillnetters was randomly observed in the ports of Göltürkbükü, Gündoğan, Yalıkavak and Torba over two fishing seasons, from November to April 2018 and 2019. A total of 18,163 kg of fish were caught in 147 daily operations. The composition of catches from the bogue gillnet fishery comprised 48 species from 30 families, including both fish and invertebrates. B. boops was the most abundant species with 91.9% of the catch, followed by Diplodus annularis, Scomber colias, Trachurus trachurus, Pagellus acarne and Scomber scombrus. The ratio of total bycatch biomass to commercial target species was 1:0.09. The fork length (FL) and weight of the 536 sampled B. boops ranged between 25.5 ± 0.12 cm and 293.6 ± 3.87 g, respectively. The highest catch per unit effort (CPUE) of B. boops occurred in April and averaged 58.83 ± 11.47 kg/1000 m, likely due to an increased catch during its spawning migration to open sea areas in spring.

Long-term continuous datasets that record fishery catch are key to predicting and managing changes in fisheries. Unfortunately, long-term datasets are rare for recreational fisheries, which hinders our ability to understand long-term changes within these fisheries. Here we use several unconventional long-term datasets, including tournament and tagging program data, to assess changes in catch composition over time in the Australian east coast marlin fishery. We found significant changes to the species and size composition of species within the fishery over time. In the 1930s, catch was solely comprised of striped ( Kajikia audax ) and black ( Istiompax indica ) marlin. Black marlin proportionally dominated the fishery in the 1940s to 1980s, but the proportions of blue ( Makaira nigricans ) and striped marlin increased significantly from the 1980s until present. Currently, the fishery is comprised of primarily striped and black, and to a lesser extent blue marlin. Declines in the mean weight of black and striped marlin were also evident from the 1930s to 1980s. Technological advances improving offshore access may have driven changes in species composition. Our results demonstrate a potential change in technology and gear reshaping species composition within a fishery. This highlights how recreational fisheries, particularly those offshore, have changed with the technology over time, and the potential for future technological to dramatically alter recreational fisheries globally. Graphic abstract

Monitoring marine resource exploitation is a key activity in fisheries science and biodiversity conservation. Since research surveys are time consuming and costly, fishery-dependent data (i.e., derived directly from fishing vessels) are increasingly credited with a key role in expanding the reach of ocean monitoring. Fishing vessels may be seen as widely ranging data-collecting platforms, which could act as a fleet of sentinels for monitoring marine life, in particular exploited stocks. Here, we investigate the possibility of assessing catch composition of single hauls carried out by trawlers by applying DNA metabarcoding to the dense water draining from fishing nets just after the end of hauling operations (hereafter “slush”). We assess the performance of this approach in portraying β-diversity and examining the quantitative relationship between species abundances in the catch and DNA amount in the slush (read counts generated by amplicon sequencing). We demonstrate that the assemblages identified using DNA in the slush satisfactorily mirror those returned by visual inspection of net content (about 71% of species and 86% of families of fish) and detect a strong relationship between read counts and species abundances in the catch. We therefore argue that this approach could be upscaled to serve as a powerful source of information on the structure of demersal assemblages and the impact of fisheries.

Reef fisheries are multispecific and employ a variety of fishing gears across marine environments, even in remote areas. This intricate and multifaceted nature of reef fisheries is often overlooked in management strategies, leading to global management failures. In Brazil, information about reef fisheries is often scarce and scattered. This stems from inadequate policies and an unrecognized societal value of reef fisheries. Here, we combine nationwide reef fish landing data (1950–2015) with an extensive literature review on Brazilian reef fisheries. We explore temporal and spatial patterns in total landings, species traits, functional diversity and composition to understand the current scenario, identify drivers of change and highlight information gaps. Brazilian reef fisheries rapidly increased in landing volume, number of targeted species and exploited traits in the 1980’s, despite mainly targeting carnivorous fish (groupers, snappers, jacks and trevallies). Exploited functional space increased over time, mainly due to the incorporation of smaller and lower-trophic level species that gradually were added to the pool of fished species. Local and international markets have been the main drivers behind these patterns, while subsistence fishing is marginal. Lack of proper management and enforcement of existing regulations have led to population declines, dwindling total catches since the early 2000’s, and numerous threatened species. Artisanal fishing accounts for the majority of catches, raising concern on the social impacts of degraded reef fisheries. We highlight the urgent need for adequate fishing statistics, and the use/application of science-based management and policy actions to secure productive fisheries and healthy reef ecosystems in Brazil.

Structural habitats support high biodiversity by providing refuge, forage resources, and recruitment habitat that upwardly influence the broader faunal community structure. However, there are few system-wide studies that empirically measure communities before and after major shifts in habitat structure or availability, limiting our ability to predict the consequences of changes in structural habitat above local scales. We used the collapse of the Apalachicola Bay, Florida oyster population as a natural experiment to assess the impacts of estuary-wide structural habitat loss on the nekton community through long-term faunal monitoring data. Habitat losses of this magnitude are expected to decrease diversity and alter composition, so we expected to observe these changes in Apalachicola Bay after the oyster population collapse. We assessed changes in Gini-Simpson diversity and composition over a 21-year period encompassing the 2012 oyster collapse using generalized linear mixed models to account for confounding drivers. We surprisingly found no evidence that Gini-Simpson diversity or composition differed immediately before or following the collapse, which may be explained if estuarine fauna were able to effectively use other habitats. This suggests that proportional changes in diversity or composition from loss or gain of structural habitats cannot be assumed at the system-wide scale.

Population regulation is a central concept in ecology, yet in many cases its presence and the underlying mechanisms are difficult to demonstrate. The current paradigm maintains that marine fish populations are predominantly regulated by density‐dependent recruitment. While it is known that density‐dependent somatic growth can be present too, its general importance remains unknown and most practical applications neglect it. This study aimed to close this gap by for the first time quantifying and comparing density dependence in growth and recruitment over a large set of fish populations. We fitted density‐dependent models to time‐series data on population size, recruitment and age‐specific weight from commercially exploited fish populations in the Northeast Atlantic Ocean and the Baltic Sea. Data were standardized to enable a direct comparison within and among populations, and estimated parameters were used to quantify the impact of density regulation on population biomass. Statistically significant density dependence in recruitment was detected in a large proportion of populations (70%), whereas for density dependence in somatic growth the prevalence of density dependence depended heavily on the method (26% and 69%). Despite age‐dependent variability, the density dependence in recruitment was consistently stronger among age groups and between alternative approaches that use weight‐at‐age or weight increments to assess growth. Estimates of density‐dependent reduction in biomass underlined these results: 97% of populations with statistically significant parameters for growth and recruitment showed a larger impact of density‐dependent recruitment on population biomass. The results reaffirm the importance of density‐dependent recruitment in marine fishes, yet they also show that density dependence in somatic growth is not uncommon. Furthermore, the results are important from an applied perspective because density dependence in somatic growth affects productivity and catch composition, and therefore the benefits of maintaining fish populations at specific densities.

As species respond to warming water temperatures, fishers dependent upon such species are being compelled to make choices concerning harvest strategies. Should they “follow fish” to new fishing grounds? Should they change their mix of target species? Should they relocate their operations to new ports? We examined how fishing communities in the Northeast United States —a hotspot of recent warming—have already responded to documented shifts in the distribution and abundance of fluke, red and silver hake. We focused on groundfish trawl communities that historically targeted these species and examined their “at-sea” responses by combining qualitative interviews with quantitative analysis of fishing records and ecological surveys. Three distinct responses emerged: shifting fishing grounds, shifting target species, and shifting port of landing. Our research finds that following the fish is rare and only occurred in one of the assessed communities, the large trawler community of Beaufort, North Carolina. The more common response was a shift in target species and a change in catch composition. However, regulations and markets often constrained the ability to take advantage of a changing mix of species within fishing grounds. Indeed, the overall species diversity in catch has declined among all of our focal communities suggesting that communities have lost the ability to be flexible when it may be most needed as a response to climate change. Additionally, the high value of fluke and the need to land in southern states with higher quota allocations is likely a driver of the changing nature of “community” with increasing vessels landing outside their home port, especially when landing fluke. Our findings suggest that fidelity to historical fishing grounds combined with perceiving environmental change as non-permanent, predispose many fishers to trust in “cyclicality” and return of species over time. However, this strategy may make those communities unable or unwilling to “follow fish” more vulnerable to changes in distribution and abundance due to climate change. Our findings have the potential to directly inform resource management policies as well as more deliberate adaptations by communities themselves as they strive to address the imminent risks of climate change.

Recreational fishing is an increasingly popular leisure activity on a global scale, with catches that may surpass those of commercial fisheries. However, the lack of comprehensive and standardized data hinders accurate assessment of its ecological impact. This study investigates the species composition across three variables including fishing modalities (shore angling, boat angling, and spearfishing), zone and season along the NW Mediterranean coast. Species identification and number of individuals caught data were obtained through onsite surveys conducted between 2020 and 2023. The results reveal significant differences in catch composition among modalities, as well as across spatial and seasonal scales. However, modality exhibited the greatest differentiation in catch composition compared to the other two variables. Then, regarding modality, boat angling and spearfishing yield the highest catch rates but boat angling had the greatest number of species (i.e., 69). However, species composition characterized the catches of each modality. Specifically, Dicentrarchus labrax was more frequently fished by shore anglers, Loligo vulgaris by boat anglers, and Mullus surmuletus by spearfishers. Currently, there is a need to develop and reinforce marine recreational fisheries sustainable management practices at a regional scale. In the study area, our findings suggest that fishing modality is the main driver to consider when developing sustainable management strategies and the conservation of coastal marine biodiversity.