Brobdingnagians and Goliaths: two forms of gigantism in fish.

Two forms of gigantism are differentiated in fish, Brobdingnagian and Goliathan gigantism, the former applying to populations whose individuals are all larger than is typical for the taxon, the latter to single individuals within a population. While Brobdingnagian gigantism is largely explained by various ecological and evolutionary rules, Goliathan gigantism is not. A mechanistic hypothesis is proposed which explains Goliathan gigantism in terms of the reduction of oxygen requirements of individual fish via moving to cooler temperatures and/or acquiring larger, more energy-dense prey, which enable them to get bigger, and, in the process, sometimes generate bimodal size distributions that may qualify as gradual forms between Goliathan and Brobdingnagian gigantism. This mechanism, which relies on the manner in which their gill surface area grows, is more likely to operate in fish that can get big in the first place than in fish that remain small.

Rapid growth in a large Cambrian apex predator.

Despite the importance of ontogenetic data on early diverging euarthropods to our understanding of the ecology and evolution of past life, the data are distinctly lacking, as reconstructing life histories of fossil animals is often challenging. Here we report the growth trajectory of frontal appendages of the apex predator Amplectobelua symbrachiata, one of the most common radiodont arthropods from the early Cambrian Chengjiang biota (c. 520 Ma) of China. Analysis of 432 specimens (9.1-137.1 mm length; 1.3-25.6 mm height) reveals that appendages grew isometrically, with an estimated maximum size of the whole animal of c. 90 cm. Individuals grew rapidly compared to extant arthropods, as assessed using the electronic length-frequency analysis (ELEFAN) approach. Therefore, we show that the Cambrian apex predator A. symbrachiata was an extremely fast-growing arthropod, with an unusual life history strategy that formed as part of the escalatory 'arms race' that shaped the Cambrian explosion over 500 Ma.

Fishery catch is affected by geographic expansion, fishing down food webs and climate change in Aotearoa, New Zealand.

Historical fishing effort has resulted, in many parts of the ocean, in increasing catches of smaller, lower trophic level species once larger higher trophic level species have been depleted. Concurrently, changes in the geographic distribution of marine species have been observed as species track their thermal affinity in line with ocean warming. However, geographic shifts in fisheries, including to deeper waters, may conceal the phenomenon of fishing down the food web and effects of climate warming on fish stocks. Fisheries-catch weighted metrics such as the Mean Trophic Level (MTL) and Mean Temperature of the Catch (MTC) are used to investigate these phenomena, although apparent trends of these metrics can be masked by the aforementioned geographic expansion and deepening of fisheries catch across large areas and time periods. We investigated instances of both fishing down trophic levels and climate-driven changes in the geographic distribution of fished species in New Zealand waters from 1950-2019, using the MTL and MTC. Thereafter, we corrected for the masking effect of the geographic expansion of fisheries within these indices by using the Fishing-in-Balance (FiB) index and the adapted Mean Trophic Level (aMTL) index. Our results document the offshore expansion of fisheries across the New Zealand Exclusive Economic Zone (EEZ) from 1950-2019, as well as the pervasiveness of fishing down within nearshore fishing stock assemblages. We also revealed the warming of the MTC for pelagic-associated fisheries, trends that were otherwise masked by the depth- and geographic expansion of New Zealand fisheries across the study period.

Comment on "Metabolic scaling is the product of life-history optimization".

White et al. (Science 377, p. 834-839, 2022) propose that reproduction reduces the somatic growth of animals. This contradicts the common observations that non-reproducing adults are not larger than those that reproduced as well as the very example the authors provide of a fish that reproduces while its growth continues to accelerate, which is common in larger fish.

Global Fisheries Science Documents Human Impacts on Oceans: The Sea Around Us Serves Civil Society in the Twenty-First Century.

Fishing provides the world with an important component of its food supply, but it also negatively impacts the biodiversity of marine and freshwater ecosystems, especially when industrial fishing is involved. To mitigate these impacts, civil society needs access to fisheries data (i.e., catches and catch-derived indicators of these impacts). Such data, however, must be more comprehensive than the official fisheries statistics supplied to the Food and Agriculture Organization of the United Nations (FAO) by its member countries, which shape public policy in spite of their deficiencies, notably underestimating small-scale fisheries. This article documents the creation, based on the geographically coarse FAO data, of a database and website (https://www.seaaroundus.org) that provides free reconstructed (i.e., corrected) catch data by ecosystem, country, species, gear type, commercial value, etc., to any interested person, along with catch-derived indicators from 1950 to the near present for the entire world.

Reimagining sustainable fisheries.

The current conception of sustainable fisheries focuses on single "stocks" targeted by industrial fisheries to supply growing global markets, including those for fishmeal. Sustainable fisheries should be reimagined to minimize exploitation and prioritize artisanal and subsistence fishing that feeds people.

A palaeothermometer of ancient Indigenous fisheries reveals increases in mean temperature of the catch over five millennia.

Climate change is altering the distribution and composition of marine fish populations globally, which presents substantial risks to the social and economic well-being of humanity. While deriving long-term climatic baselines is an essential step for detecting and attributing the magnitude of climate change and its impacts, these baselines tend to be limited to historical datasets and palaeoecological sediment records. Here, we develop a method for estimating the 'ancient Mean Temperature of the Catch' (aMTC) using Indigenous fisheries catch records from two archaeological sites in the northeast Pacific. Despite different catch compositions, we observe an increase in aMTC over a 5,000-year period at two contemporaneously occupied archaeological sites in southwestern British Columbia, Canada. We document cooler catches from 5,000 to 3,000 cal yr BP and comparatively warmer catches from 1,800 to 250 cal yr BP. These warmer temperatures are broadly consistent with palaeoceanographic sea surface temperature proxies from British Columbia and Alaska. Because this method requires converting measures of fish bones into estimates of fish size structure, abundance, biomass, and finally aMTC, opportunities exist to account for both variation and uncertainty at every step. Nevertheless, given that preindustrial fisheries data are ubiquitous in coastal archaeological sites, this method has the potential to be applied globally to broaden the temporal and geographic scale of ocean temperature baselines. Supplementary Information: The online version contains supplementary material available at 10.1007/s10641-022-01243-7.

Rebuilding fish biomass for the world's marine ecoregions under climate change.

Rebuilding overexploited marine populations is an important step to achieve the United Nations' Sustainable Development Goal 14-Life Below Water. Mitigating major human pressures is required to achieve rebuilding goals. Climate change is one such key pressure, impacting fish and invertebrate populations by changing their biomass and biogeography. Here, combining projection from a dynamic bioclimate envelope model with published estimates of status of exploited populations from a catch-based analysis, we analyze the effects of different global warming and fishing levels on biomass rebuilding for the exploited species in 226 marine ecoregions of the world. Fifty three percent (121) of the marine ecoregions have significant (at 5% level) relationship between biomass and global warming level. Without climate change and under a target fishing mortality rate relative to the level required for maximum sustainable yield of 0.75, we project biomass rebuilding of 1.7-2.7 times (interquartile range) of current (average 2014-2018) levels across marine ecoregions. When global warming level is at 1.5 and 2.6°C, respectively, such biomass rebuilding drops to 1.4-2.0 and 1.1-1.5 times of current levels, with 10% and 25% of the ecoregions showing no biomass rebuilding, respectively. Marine ecoregions where biomass rebuilding is largely impacted by climate change are in West Africa, the Indo-Pacific, the central and south Pacific, and the Eastern Tropical Pacific. Coastal communities in these ecoregions are highly dependent on fisheries for livelihoods and nutrition security. Lowering the targeted fishing level and keeping global warming below 1.5°C are projected to enable more climate-sensitive ecoregions to rebuild biomass. However, our findings also underscore the need to resolve trade-offs between climate-resilient biomass rebuilding and the high near-term demand for seafood to support the well-being of coastal communities across the tropics.

Juvenile-to-adult transition invariances in fishes: Perspectives on proximate and ultimate causation.

To bridge physiological and evolutionary perspectives on size at maturity in fishes, the authors focus on the approximately invariant ratio between the estimated oxygen supply at size at maturity (Qm ) relative to that at asymptotic size (Q∞ ) among species within a taxonomic group, and show how two important theories related to this phenomenon complement each other. Gill-oxygen limitation theory proposes a mechanistic basis for a universal oxygen supply-based threshold for maturation, which applies among and within species. On the contrary, the authors show that a generalisation of life-history theory for the invariance of size at maturity (Lm ) relative to asymptotic size (L∞ ) can provide an evolutionary rationale for an oxygen-limited maturation threshold (Qm /Q∞ ). Extending previous inter- and intraspecific analyses, the authors show that maturation invariances also occur in lake whitefish Coregonus clupeaformis (Mitchill 1818), but at both scales, theory seems to underestimate the value of the maturation threshold. They highlight some key uncertainties in the model that should be addressed to help resolve the mismatch.

The ratio of length at first maturity to maximum length across marine and freshwater fishes.

The prevailing determinant of maturation in fishes is thought to be a redirection of energy from growth to reproduction. Instead, the Gill Oxygen Limitation Theory predicts that maturation, and thus reproduction, is induced when a fish reaches a critical ratio of oxygen supply to demand (Qm /Qmaint ). The consistency of this critical ratio has been previously documented in many fishes, but a broader test was lacking. In this study, the authors assess if this critical ratio is consistent across 132 unique fish species, as measured by the slope of the relationship between Lmax D and Lm D , where Lmax is the maximum length reached in a given population, Lm is the mean size at first maturity in that population and D is a gill-related exponent which renders the Lmax D /Lm D ratio equivalent to the Qm /Qmaint ratio. The authors found that across all species, the Lmax D /Lm D ratio was 1.40 (95% c.i. 1.38-1.42), which was not significantly different from that previously estimated across other species groups (1.35, 95% c.i. 1.22-1.53), especially when phylogenetic relationships were considered (1.25, 95% Bayesian credible interval 1.09-1.40). The consistency of the Lmax D /Lm D ratio across taxa, which expresses the difference in metabolic rate at maturity and maximum size, suggests that the scaling of gill surface area is the factor that underlies this ratio, and which triggers the maturation in fishes.

The gill-oxygen limitation theory (GOLT) and its critics.

The gill-oxygen limitation theory (GOLT) provides mechanisms for key aspects of the biology (food conversion efficiency, growth and its response to temperature, the timing of maturation, and others) of water-breathing ectotherms (WBEs). The GOLT's basic tenet is that the surface area of the gills or other respiratory surfaces of WBE cannot, as two-dimensional structures, supply them with sufficient oxygen to keep up with the growth of their three-dimensional bodies. Thus, a lower relative oxygen supply induces sexual maturation, and later a slowing and cessation of growth, along with an increase of physiological processes relying on glycolytic enzymes and a declining role of oxidative enzymes. Because the "dimensional tension" underlying this argument is widely misunderstood, emphasis is given to a detailed refutation of objections to the GOLT. This theory still needs to be put on a solid quantitative basis, which will occur after the misconceptions surrounding it are put to rest.

Fisheries and Policy Implications for Human Nutrition.

PURPOSE OF REVIEW: This review brings together recent key research related to the role of fisheries as a source of nutrients to improve human health and discusses the implications of fisheries policy on food- and nutrient-security. RECENT FINDINGS: Recent studies highlight the critical role of fisheries to support human nutrition, describing the nutrient composition of hundreds of species of fish, the global distribution of these fish, and the strategic role of fisheries in addressing micronutrient deficiencies. In many developing regions and emerging economies, fisheries can address malnutrition with local supplies of critical nutrients such as fatty acids, zinc, iron, calcium, and vitamins, making these accessible to low-income populations. However, this local potential is jeopardized by overfishing, climate change, and international trade, which reduce the local availability of nutritious and affordable fish in low-income countries, where they are most needed. This calls for policy reforms that shift management focus of fisheries as a commodity provider to a domestic public health asset to ensure food- and nutrient-security.

COVID-19 provides an opportunity to advance a sustainable UK fisheries policy in a post-Brexit brave new world.

Brexit creates a systemic shock that provides a unique opportunity for the UK to implement a new sustainable Fisheries Policy to better manage the multiple stocks on which future fishers will depend on leaving the European Union. At the same time, the global slowdown of commercial fishing as a result of COVID-19 has reduced pressure on some threatened stocks to levels not seen since the Second World War. In combination, Brexit and the COVID-19 slowdown have created a unique opportunity to facilitate the recovery of a threatened resource. Nevertheless, challenges remain as fisheries represent only 0.12% of UK economic output, presenting a risk that opportunities for more sustainable management will be lost during wider trade negotiations. Reduced fishing pressure during the COVID-19 era will enable stocks an opportunity to recover if supported by a new UK Fisheries Policy that focuses on: (a) re-establishing the role of Maximum Sustainable Yield to set limits that enable the recovery of fish populations initiated during the COVID-19 era; (b) ensuring that catch targets are set with the aim to maintain biomass at 120% of that which will achieve Maximum Sustainable Yield; (c) improving coherent resource management that also considers the expensive use of carbon associated with unsustainable fishing, and the need to protect fish throughout their life-cycle; and (d) constructing and effectively enforcing protection of a resilient network of Marine Protected Areas despite potential protests from EU member states.

The urgent need for integrated science to fight COVID-19 pandemic and beyond.

The COVID-19 pandemic has become the leading societal concern. The pandemic has shown that the public health concern is not only a medical problem, but also affects society as a whole; so, it has also become the leading scientific concern. We discuss in this treatise the importance of bringing the world's scientists together to find effective solutions for controlling the pandemic. By applying novel research frameworks, interdisciplinary collaboration promises to manage the pandemic's consequences and prevent recurrences of similar pandemics.

Valuing invisible catches: Estimating the global contribution by women to small-scale marine capture fisheries production.

The role that women play in fisheries around the world is receiving increasing international attention yet the contributions by women to fisheries catches continues to be overlooked by society, industry and policy makers. Here, we address this lack of visibility with a global estimation of small-scale fisheries catches by women. Our estimates reveal that women participate in small-scale fishing activities in all regions of the world, with approximately 2.1 million (± 86,000) women accounting for roughly 11% (± 4%) of participants in small-scale fishing activities, i.e., catching roughly 2.9 million (± 835,000) tonnes per year of marine fish and invertebrates. The landed value of the catch by women is estimated at USD 5.6 billion (± 1.5 billion), with an economic impact of USD 14.8 billion per year (± 4 billion), which is equivalent to 25.6 billion real 2010 dollars (± 7.2 billion). These catches are mostly taken along the shoreline, on foot, or from small, non-motorized vessels using low-technology, low-emission gears in coastal waters. Catches taken by women are often for home consumption, and thus considered part of the subsistence sub-sector. However, in many contexts, women also sell a portion of their catch, generating income for themselves and their families. These findings underscore the significant role of women as direct producers in small-scale fisheries value chains, making visible contributions by women to food and livelihood security, globally.

A global dataset on subsidies to the fisheries sector.

This article contains data on subsidies provided to the fisheries sector by maritime countries. The dataset is the culmination of extensive data collection efforts using peer-reviewed and grey literature, national budgets, online databases, websites and other relevant sources (e.g. OECD, World Bank and WTO), in order to estimate the scope and magnitude of global fisheries subsidies. For subsidies where we found evidence of expenditure by a country, we record the total amount alongside the source references and refer to these as 'reported' data. Where evidence is found that a country provides a subsidy but no amount reported, we estimate using various approaches and refer to these as 'modeled' data. Where evidence exists that no subsidy is provided by a country we refer to these null values as 'not found evidence of subsidy'. All amounts were converted to constant 2018 USD using 2017 exchange rates and annual Consumer Price Index averages. The final dataset of 'reported', 'modeled' and 'not found' subsidies for 2018 consists of 13 subsidy types across 152 maritime countries. The dataset, first developed in the early 2000s, now forms part of the global fisheries management infrastructure and is a central tool used by WTO negotiators. The data we provide may be used to support local, regional and global fisheries management decision-making and may have further uses when analysed in combination with other fisheries related data. Interpretation of these data can be found in the associated research article titled "Updated estimates and analysis of global fisheries subsidies" [1].

Fishing through the Anthropocene.

Steneck and Pauly present an historical account of the growth of the fishing industry and an update on the status of fish populations today, using several case studies to highlight the complex and profound effects that fishing has on marine ecosystems.