Climate change drives poleward increases and equatorward declines in marine species

Marine environments have increased in temperature by an average of 1°C since preindustrial (1850) times [1]. Given that species ranges are closely allied to physiological thermal tolerances in marine organisms [2], it may therefore be expected that ocean warming would lead to abundance increases at poleward range edges, and abundance declines towards the equator [3]. Here we report a global analysis of abundance tends of 304 widely distributed marine species over the last century, across a range of taxonomic groups from phytoplankton to fish and marine mammals. Specifically, using a literature database we investigate the extent that the direction and strength of longterm species abundance changes depend on the sampled location within the latitudinal range of species. Our results show that abundance increases have been most prominent where sampling has taken place at the poleward edges of species ranges, while abundance declines have been most prominent where sampling has taken place at the equatorward edge of species ranges. These data provide evidence of omnipresent large-scale changes in abundance of marine species consistent with warming over the last century, and suggest that adaptation has not provided a buffer against the negative effects of warmer conditions at the equatorward extent of species ranges. On the basis of these results we suggest that projected sea temperature increases of up to 1.5°C over pre-industrial levels by 2050 [4] will continue to drive latitudinal abundance shifts in marine species, including those of importance for coastal livelihoods

Projected impacts of warming seas on commercially fished species at a biogeographic boundary of the European continental shelf

This is the final version. Available on open access from Wiley via the DOI in this recordProjecting the future effects of climate change on marine fished populations can help prepare the fishing industry and management systems for resulting ecological, social and economic changes. Generating projections using multiple climate scenarios can provide valuable insights for fisheries stakeholders regarding uncertainty arising from future climate data. Using a range of climate projections based on the Intergovernmental Panel on Climate Change A1B, RCP4.5 and RCP8.5 climate scenarios, we modelled abundance of eight commercially important bottom dwelling fish species across the Celtic Sea, English Channel and southern North Sea through the 21st century. This region spans a faunal boundary between cooler northern waters and warmer southern waters, where mean sea surface temperatures are projected to rise by 2 to 4°C by 2098. For each species, Generalized Additive Models were trained on spatially explicit abundance data from six surveys between 2001 and 2010. Annual and seasonal temperatures were key drivers of species abundance patterns. Models were used to project species abundance for each decade through to 2090. Projections suggest important future changes in the availability and catchability of fish species, with projected increases in abundance of red mullet Mullus surmuletus L., Dover sole Solea solea L., John dory Zeus faber L. and lemon sole Microstomus kitt L. and decreases in abundance of Atlantic cod Gadus morhua L., anglerfish Lophius piscatorius L. and megrim Lepidorhombus whiffiagonis L. European plaice Pleuronectes platessa L. appeared less affected by projected temperature changes. Most projected abundance responses were comparable among climate projections, but uncertainty in the rate and magnitude of changes often increased substantially beyond 2040. Synthesis and applications. These results indicate potential risks as well as some opportunities for demersal fisheries under climate change. These changes will challenge current management systems, with implications for decisions on target fishing mortality rates, fishing effort and allowable catches. Increasingly flexible and adaptive approaches that reduce climate impacts on species while also supporting industry adaptation are required.Centre for Environment, Fisheries and Aquaculture ScienceNatural Environment Research Council (NERC

Can we project changes in fish abundance and distribution in response to climate?

Large scale and long-term changes in fish abundance and distribution in response to climate change have been simulated using both statistical and process-based models. However, national and regional fisheries management requires also shorter term projections on smaller spatial scales, and these need to be validated against fisheries data. A 26-year time series of fish surveys with high spatial resolution in the North East Atlantic provides a unique opportunity to assess the ability of models to correctly simulate the changes in fish distribution and abundance that occurred in response to climate variability and change. We use a dynamic bioclimate envelope model forced by physical-biogeochemical output from eight ocean models to simulate changes in fish abundance and distribution at scales down to a spatial resolution of 0.5°. When comparing with these simulations with annual fish survey data, we found the largest differences at the 0.5° scale. Differences between fishery model runs driven by different biogeochemical models decrease dramatically when results are aggregated to larger scales (e.g. the whole North Sea), to total catches rather than individual species or when the ensemble mean instead of individual simulations are used. Recent improvements in the fidelity of biogeochemical models translate into lower error rates in the fisheries simulations. However, predictions based on different biogeochemical models are often more similar to each other than they are to the survey data, except for some pelagic species. We conclude that model results can be used to guide fisheries management at larger spatial scales, but more caution is needed at smaller scales

Fishing impacts on age structure may conceal environmental drivers of body size in exploited fish populations

Publication history: Accepted - 8 January 2023; Published - 11 February 2023.Using analysis of field survey size-at-age data, we examine responses of European plaice (Pleuronectes platessa) to spatial differences in environmental variables in the North Sea. Using available samples of plaice aged 1–7, northern and southern migrating groups of males and females grew differently. However, length-at-age growth patterns were not corroborated by complementary otolith-based estimates. Southern females and males were smaller than their northern counterparts until age 3. Southern males remained smaller up to age 7; by contrast southern and northern females reached similar size-at-age by year 4. Due to covariation, the influence of spatially variable environmental conditions was equivocal. However, temperature, depth, fishing pressure, phosphate levels, distance from shore, and conspecific density were all significant predictors of size for plaice aged 1–7. Our results suggest that fishing impacts on age structure limit the potential to examine the role of environmental variation on body size. For fish that rarely reach their full potential age and size, expected metabolic responses to warming may remain unexpressed, challenging predictions in a changing climate.This work was supported by a Natural Environment Research Council (NERC) NERC-Cefas CASE PhD Studentship (L.A.R.; NE/L501669/1), NERC KE Fellowship (S.D.S.; NE/J500616/2), and Cefas Seedcorn (E.H.)

Changes of potential catches for North-East Atlantic small pelagic fisheries under climate change scenarios

Small- and intermediate-size pelagic fisheries are highly impacted by environmental variability and climate change. Their wide geographical distribution and high mobility makes them more likely to shift their distribution under climate change. Here, we explore the potential impact of different climate change scenarios on the four main commercial pelagic species in the North-East Atlantic (NEA): Atlantic mackerel (Scomber scombrus), European sprat (Sprattus sprattus), Atlantic herring (Clupea harengus) and blue whiting (Micromesistius poutassou). We used a process-based fisheries model (SS-DBEM), where all the target species were exploited at their maximum sustainable yield (MSY), to project future potential catches under a high- and low-future-greenhouse-gas scenario (RCP 2.6 and 8.5, respectively). Two ocean biogeochemical models (GDFL and MEDUSA) were used to force the environmental conditions. Mackerel and sprat are projected to have increases in a potential catch under both scenarios. Herring and blue whiting are projected to increase under the RCP2.6, but future projections under RCP8.5 show mixed responses with decreases or no changes forecasted. Overall, the potential catch is projected to increase in the northern area of the NEA but is projected to decrease in the southern area. These projected changes are mainly driven by changes in temperature and primary production. Shifts in the distribution of pelagic resources may destabilize existing international agreements on sharing of straddling resources as exemplified by the dispute in sharing of quota for Atlantic mackerel. Novel climate-ready policy approaches considering full species distribution are needed to complement current stock-based approaches

Fishes in a changing world: learning from the past to promote sustainability of fish populations

Populations of fishes provide valuable services for billions of people, but face diverse and interacting threats that jeopardize their sustainability. Human population growth and intensifying resource use for food, water, energy and goods are compromising fish populations through a variety of mechanisms, including overfishing, habitat degradation and declines in water quality. The important challenges raised by these issues have been recognized and have led to considerable advances over past decades in managing and mitigating threats to fishes worldwide. In this review, we identify the major threats faced by fish populations alongside recent advances that are helping to address these issues. There are very significant efforts worldwide directed towards ensuring a sustainable future for the world's fishes and fisheries and those who rely on them. Although considerable challenges remain, by drawing attention to successful mitigation of threats to fish and fisheries we hope to provide the encouragement and direction that will allow these challenges to be overcome in the future