Species diversification under climate change

Warmer seas could mean rethinking the kind of fish we farm. Lynne Falconer reports on a new study on the implications of climate change for aquaculture.

Species diversification is often suggested as a potential climate adaptation option for the aquaculture sector. However, identifying suitable candidate species for aquaculture is complicated as there are many different factors that will influence the feasibility of production and commercial success. One of the deciding factors is whether the environmental conditions in a potential farming location will meet the requirements of a species, and species diversification strategies need to consider how environmental conditions at farming locations may change in the future.

Our new article, Diversification of marine aquaculture in Norway under climate change, published in Aquaculture, was a collaboration between researchers from the University of Stirling, Nofima, Akvaplan-niva, NIVA, Institute of Marine Research (IMR), Bjerknes Centre for Climate Research, and the Hellenic Centre for Marine Research (HCMR).

John Dory

In this study, we looked at how changing sea temperatures between 2020 and 2100 may affect marine aquaculture species diversification in Norway.

The study focused on sea-based production, and we used climate model projections of future sea temperatures under three climate scenarios (low emissions, intermediate emissions, high emissions) for 12 farm locations (three farms each in four areas of Norway: South, West, North, Arctic) and then evaluated the temperatures for 34 species (17 fish species, six bivalves, five crustaceans, three seaweeds, two echinoderms and one tunicate).

For each farming location, we classified the daily temperatures using a Challenging Conditions Index (CCI), based on known temperature tolerances for the 34 individual species. If the daily temperature was higher or lower than a threshold for that species, then it was considered challenging.

Challenging conditions are an indication that there may be adverse impacts, for example reduced growth or lower survivability. In some cases, depending on the knowledge and resources available for the species, it may be possible to address the challenging conditions with interventions such as changes in farm management practices, new feeding strategies or different technology.

Fish Farm

On the other hand, if appropriate interventions would not be possible and there would be unacceptable impacts on species’ health and farm production, then the challenging conditions will be a limiting factor for a species. In the article we also discuss the difficulties of determining and using thresholds, and the need for more studies and data, especially in the case of multiple stressors and combined effects (eg, temperature and a health challenge). For all aquaculture species, whether new or established, more work is required to understand species-specific tolerances to changing conditions and multiple stressors.

The model projections suggest that temperature changes will not be constant over time, so any species selected for aquaculture must be able to tolerate a range of temperature conditions, and species with narrower tolerance ranges may be more difficult to farm. Differences in the projected temperatures between the climate scenarios are more noticeable in the second half of the century.

Unsurprisingly, for species that prefer cold water, like witch flounder, spotted wolf-fish and snow crab, hot challenging days affected a higher proportion of the year in the South compared to the Arctic. For those warm-water species more commonly farmed in the Mediterranean (eg, European sea bass, gilthead seabream), the results suggest that cold temperatures would still be challenging for sea-based production for the rest of the century. For some species there would be both hot and cold challenging days depending on the time of year, and these would need different intervention strategies to adapt to.

Snow crab

It is not possible to suggest the “best suited” species based on this work alone, but the findings can contribute to discussions on species diversification and climate adaptation strategies within the aquaculture sector.

Establishing a new commercial aquaculture species takes time, effort, knowledge and resources. As a way of evaluating the aquaculture status of a species, the study introduced the Aquaculture Readiness Levels (ARL®). The ARL® comprise of 10 levels (Research 1-3, Development 4-6, Commercialisation 7 -9, Adaptation 10). Species such as John Dory and monkfish have low ARL® as these are not cultured at present and most of the knowledge on these species is from wild observations or fisheries studies. Even if conditions are suitable for these species, commercial aquaculture production could still be decades away and there may be other bottlenecks or limitations (eg, breeding, husbandry, nutrition).

In contrast, rainbow trout and Atlantic cod have a higher ARL® as these species are already farmed commercially. At higher ARL® levels there is more knowledge of that species and farming requirements but there will still be uncertainties about effects of climate change. All species should be aiming for ARL® 10, where climate action is embedded within production strategies.

Witch flounder

Climate action-oriented aquaculture is production that integrates adaptation practices and mitigation efforts that reduce greenhouse gas emissions. As conditions change, the level of knowledge and resources must be continually reviewed and enhanced to improve adaptive capacity across all parts of the aquaculture sector.

Although we focused on Norway, the study has relevance to other countries interested in species diversification. Species diversification takes time, effort and resources, and a range of stakeholders must also be involved in the decisions. Across the entire global aquaculture sector, industry, researchers, and policymakers must work together to ensure the necessary knowledge, experience and resources are available to support established and new species under climate change.

Spotted wolf-fish

This work was funded by the UK Research and Innovation Future Leaders Fellowship (MR/V021613/1), the Norwegian Research Council (No 194050, Insight), and ArcticHub (European Union Horizon 2020 research and innovation programme under grant agreement No 869580).

The research article was published in Aquaculture (www.sciencedirect.com/journal/aquaculture) .

Diversification of marine aquaculture in Norway under climate change. Aquaculture, 593: 741350 2024. (Falconer, L, Sparboe, L O, Dale, T, Hjøllo, S S, Stavrakidis-Zachou, O, Bergh, Ø, James, P, Papandroulakis, N, Puvanendran, V, Siikavuopio, S I, Hansen, Ø J & Ytteborg, E.