Improving understanding of the functional diversity of fisheries by exploring the influence of global catch reconstruction

Trait-based insights into sustainable fisheries: A four-decade perspective in Azores archipelago

The trait-based approach provides a powerful perspective for analyzing fisheries and their potential impact on marine ecological processes, offering crucial insights into sustainability and ecosystem functioning. This approach was applied to investigate trends in fish assemblages landed by both local and coastal fishing fleets in the Azores archipelago over the past four decades (1980s, 1990s, 2000s, and 2010s). A matrix of ten traits was built to assess functional redundancy (Fred), functional over-redundancy (FOve), and functional vulnerability (FVul) for the fish assemblages caught by every fishing fleet in each decade. The susceptibility of the Azorean fishery to negative impacts on ecosystem functioning was evidenced by low FRed (<1.5 species per functional entity) and high FVul (exceeding 70 %). However, there is reason for optimism, as temporal trends in the 2000s and 2010s showed an increase in FRed and FOve along with a significant decrease in FVul. These trends indicate the adaptation of the fishery to new target species and, notably, the effectiveness of local fish regulations in mitigating the impacts of targeting functionally important species, such as Elasmobranchii, over the past two decades. These regulations have played a pivotal role in preserving ecological functions within the ecosystem, as well as in managing the removal of high biomass of key important species (e.g., Trachurus picturatus, Pagellus bogaraveo, and Katsuwonus pelamis) from the ecosystem. This study contributes to understanding the delicate balance between fishing pressure, ecological resilience, and sustainable resource management in Azorean waters. It also highlights the importance of continued monitoring, adaptive management, and the enforcement of local fishing regulations to ensure the long-term health and sustainability of the fishery and the broader marine ecosystem.

Long term declines in the functional diversity of sharks in the coastal oceans of eastern Australia

Human impacts lead to widespread changes in the abundance, diversity and traits of shark assemblages, altering the functioning of coastal ecosystems. The functional consequences of shark declines are often poorly understood due to the absence of empirical data describing long-term change. We use data from the Queensland Shark Control Program in eastern Australia, which has deployed mesh nets and baited hooks across 80 beaches using standardised methodologies since 1962. We illustrate consistent declines in shark functional richness quantified using both ecological (e.g., feeding, habitat and movement) and morphological (e.g., size, morphology) traits, and this corresponds with declining ecological functioning. We demonstrate a community shift from targeted apex sharks to a greater functional richness of non-target species. Declines in apex shark functional richness and corresponding changes in non-target species may lead to an anthropogenically induced trophic cascade. We suggest that repairing diminished shark populations is crucial for the stability of coastal ecosystems.

Trade and foreign fishing mediate global marine nutrient supply

SignificanceThe world produces enough food to nourish the global population, but inequitable distribution of food means many people remain at risk for undernutrition. Attainment of Sustainable Development Goal 2 relies on greater attention to distribution processes that match food qualities with dietary deficiencies. We explore this in the context of fisheries. Foreign fishing and international trade divert nutrients caught in marine fisheries from nutrient-insecure toward nutrient-secure nations. Where nutrient-insecure countries do benefit from foreign fishing and trade, there tends to be high vulnerability to future changes in nutrient flows arising from changes to foreign fishing and trade. This research highlights the need for greater transparency around distribution of fish and for nutrition security to be considered more centrally in development of trade agreements.

Fish functional diversity as an indicator of resilience to industrial fishing in Patagonia Argentina

The relationship between fish functional diversity and fishing levels at which its baselines shift is important to identify the consequences of fishing in ecosystem functioning. For the first time, the authors of this study implemented a trait-based approach in the Argentine Patagonian Sea to identify the vulnerability and spatiotemporal changes in functional diversity of fish assemblages incidentally captured by a trawling fleet targeting the Argentine red shrimp Pleoticus muelleri (Spence Bate, 1888) between 2003 and 2014. The authors coupled seven fish trophic traits to a reconstructed fish assemblage for the study area and by-catch and evaluated changes in fish species richness and four complementary functional diversity measures (functional richness, redundancy, dispersion and community trait values) along with fishing intensity, temporal use, latitudinal location and depth of fishing grounds, and vessel length. Resident fishes larger than 30 cm in length, with depressed and fusiform bodies, intermediate to high trophic levels, and feeding in benthic, demersal and midwater areas were vulnerable to by-catch. In addition, fish assemblages exhibited a low functional trait redundancy, likely related to species influxes in a biogeographic ecotone with tropicalisation signs. Significant increases in fish trait richness and dispersion poleward and deep suggested new functional roles in these grounds, matching trends in community body size, reproductive load, maximum depth and trophic level. Finally, a temporal increase in fish species and functional trait removal in fishing grounds led to trait homogenisation since 2003. The authors identified that tipping points in temperate fish functional trait diversity showed the importance of trait-based approaches within ecosystem-based fisheries management.

Micronutrient supply from global marine fisheries under climate change and overfishing

Fish are rich in bioavailable micronutrients, such as zinc and iron, deficiencies of which are a global food security concern.^1,2 Global marine fisheries yields are threatened by climate change and overfishing,^3,4 yet understanding of how these stressors affect the nutrients available from fisheries is lacking.^5,6 Here, using global assessments of micronutrient content² and fisheries catch data,⁷ we investigate how the vulnerability status of marine fish species^8,9 may translate into vulnerability of micronutrient availability at scales of both individual species and entire fishery assemblages for 157 countries. We further quantify the micronutrient evenness of catches to identify countries where interventions can optimize micronutrient supply. Our global analysis, including >800 marine fish species, reveals that, at a species level, micronutrient availability and vulnerability to both climate change and overfishing varies greatly, with tropical species displaying a positive co-tolerance, indicating greater persistence to both stressors at a community level.¹⁰ Global fisheries catches had relatively low nutritional vulnerability to fishing. Catches with higher species richness tend to be nutrient dense and evenly distributed but are more vulnerable to climate change, with 40% of countries displaying high vulnerability. Countries with high prevalence of inadequate micronutrient intake tend to have the most nutrient-dense catches, but these same fisheries are highly vulnerable to climate change, with relatively lower capacity to adapt.¹¹ Our analysis highlights the need to consolidate fisheries, climate, and food policies to secure the sustainable contribution of fish-derived micronutrients to food and nutrition security.

Delineating reef fish trophic guilds with global gut content data synthesis and phylogeny

Understanding species' roles in food webs requires an accurate assessment of their trophic niche. However, it is challenging to delineate potential trophic interactions across an ecosystem, and a paucity of empirical information often leads to inconsistent definitions of trophic guilds based on expert opinion, especially when applied to hyperdiverse ecosystems. Using coral reef fishes as a model group, we show that experts disagree on the assignment of broad trophic guilds for more than 20% of species, which hampers comparability across studies. Here, we propose a quantitative, unbiased, and reproducible approach to define trophic guilds and apply recent advances in machine learning to predict probabilities of pairwise trophic interactions with high accuracy. We synthesize data from community-wide gut content analyses of tropical coral reef fishes worldwide, resulting in diet information from 13,961 individuals belonging to 615 reef fish. We then use network analysis to identify 8 trophic guilds and Bayesian phylogenetic modeling to show that trophic guilds can be predicted based on phylogeny and maximum body size. Finally, we use machine learning to test whether pairwise trophic interactions can be predicted with accuracy. Our models achieved a misclassification error of less than 5%, indicating that our approach results in a quantitative and reproducible trophic categorization scheme, as well as high-resolution probabilities of trophic interactions. By applying our framework to the most diverse vertebrate consumer group, we show that it can be applied to other organismal groups to advance reproducibility in trait-based ecology. Our work thus provides a viable approach to account for the complexity of predator-prey interactions in highly diverse ecosystems.

Global change in the functional diversity of marine fisheries exploitation over the past 65 years

Overexploitation is recognized as one of the main threats to global biodiversity. Here, we report a widespread change in the functional diversity of fisheries catches from the large marine ecosystems (LMEs) of the world over the past 65 years (1950 to 2014). The spatial and temporal trends of functional diversity exploited from the LMEs were calculated using global reconstructed marine fisheries catch data provided by the Sea Around Us initiative (including subsistence, artisanal, recreational, industrial fisheries, and discards) and functional trait data available in FishBase. Our analyses uncovered a substantial increase in the functional richness of both ray-finned fishes (80% of LMEs) and cartilaginous species (sharks and rays) (75% of LMESs), in line with an increase in the taxonomic richness, extracted from these ecosystems. The functional evenness and functional divergence of these catches have also altered substantially over the time span of this study, with considerable geographic variation in the patterns detected. These trends show that global fisheries are increasingly targeting species that play diverse roles within the marine ecosystem and underline the importance of incorporating functional diversity in ecosystem management.