Insight into real-world complexities is required to enable effective response from the aquaculture sector to climate change

This study demonstrates how a comprehensive knowledge base can be used by the aquaculture industry, researchers, and policymakers as a foundation for more targeted and detailed climate change impact analysis, risk assessments and adaptation planning. Atlantic salmon (Salmo salar) production in Norway was used as a case study and to illustrate the need to consider impacts from multiple stressors across different production stages and the wider supply chain. Based on literature searches and industry news, a total of 45 impacts and 101 adaptation responses were identified. Almost all impacts were linked to multiple climate stressors, and many adaptation responses can be used for a range of impacts. Based on the research, a move towards more targeted and detailed assessments is recommended. This can be facilitated through a strong knowledge base, further research to address complexities, and better communication between all stakeholders. The results also demonstrate the need for more climate change research that reflects the challenges that the aquaculture sector faces, where multiple stressors and the range of impacts across production stages and the wider supply chain are included. Highlighting the wide range of stressors, impacts and adaptation responses provides a more holistic understanding of the real-world complexities that aquaculture producers face. This again could facilitate adoption of more effective responses to climate change needed to maintain or increase production sustainably

Climate change with increasing seawater temperature will challenge the health of farmed Atlantic Cod (Gadus morhua L.)

Aquaculture is one of the fastest growing food production sectors in the world and further expansion is expected throughout the 21st century. However, climate change is threatening the development of the sector and action is needed to prepare the industry for the coming challenges. Using downscaled temperature projections based on the Intergovernmental Panel on Climate Change (IPCC) climate projection (Shared Socioeconomic Pathway, SSP2-4.5), we analysed potential future temperatures at a selected Atlantic cod (Gadus morhua L.) farm site in Northern Norway. Results showed that the farming area may experience increased temperatures the next 10–15 years, including more days with temperatures above 17°C. Based on the predicted future conditions, we designed a study with Atlantic cod (Gadus morhua L.) to evaluate effects from high temperature alone and in combination with Fransicella noatunensis infection. Fish were kept at 12°C and 17°C for eight weeks and samples of skin and spleen collected at different timepoints were analysed with transcriptomics, histology, scanning electron microscopy and immunohistochemistry. Results showed that high temperature had a stronger effect on the barrier functions of skin than the infection. Increased temperature induced gene expression changes in skin and spleen, heat shock protein 47 and cold inducible RNA binding protein were identified as potential gene markers for thermal stress. The effect of bacterial challenge was small at 12°C. At high temperature, the development of severe pathology in spleen coincided with a significant decrease of immunoglobulins transcripts, which contrasted with the activation of multiple immune genes. In addition, we used an in vitro model of skin biopsies and scale explants exposed to hydrogen peroxide (H2O2) to assess the effects of thermal and oxidative stress. High temperature and H2O2 reduced proliferation and migration of keratocytes, and increased expression of stress markers, and compounding effects were observed with combined stressors. Results suggest that the projected increased seawater temperature will pose a significant threat to Norwegian cod farming, affecting various biological processes and making fish more vulnerable to stressors and pathogens. Cod farming needs high attention to temperature changes, and special precautions should be taken if the temperature increases beyond cods’ thermal optimum

Development of the Synarcual in the Elephant Sharks (Holocephali; Chondrichthyes): Implications for Vertebral Formation and Fusion

The synarcual is a structure incorporating multiple elements of two or more anterior vertebrae of the axial skeleton, forming immediately posterior to the cranium. It has been convergently acquired in the fossil group ‘Placodermi’, in Chondrichthyes (Holocephali, Batoidea), within the teleost group Syngnathiformes, and to varying degrees in a range of mammalian taxa. In addition, cervical vertebral fusion presents as an abnormal pathology in a variety of human disorders. Vertebrae develop from axially arranged somites, so that fusion could result from a failure of somite segmentation early in development, or from later heterotopic development of intervertebral bone or cartilage. Examination of early developmental stages indicates that in the Batoidea and the ‘Placodermi’, individual vertebrae developed normally and only later become incorporated into the synarcual, implying regular somite segmenta- tion and vertebral development. Here we show that in the holocephalan Callorhinchus milii, uniform and regular vertebral segmentation also occurs, with anterior individual vertebra developing separately with subsequent fusion into a synarcual. Vertebral elements forming directly behind the synarcual continue to be incorporated into the synarcual through growth. This appears to be a common pattern through the Vertebrata. Research into human disor- ders, presenting as cervical fusion at birth, focuses on gene misexpression studies in humans and other mammals such as the mouse. However, in chondrichthyans, vertebral fusion represents the normal morphology, moreover, taxa such Leucoraja (Batoidea) and Callorhinchus (Holocephali) are increasingly used as laboratory animals, and the Callor- hinchus genome has been sequenced and is available for study. Our observations on synarcual development in three major groups of early jawed vertebrates indicate that fusion involves heterotopic cartilage and perichondral bone/mineralised cartilage developing outside the regular skeleton. We suggest that chondrichthyans have potential as ideal extant models for identifying the genes involved in these processes, for application to human skeletal heterotopic disorders

The importance of calibrating climate change projections to local conditions at aquaculture sites

Future climate projections are usually only available at global or coarse scale and the focus is often on long-term global or regional averages. Though useful to analyse general trends and identify potential risks and opportunities internationally, these resolutions are unable to capture the complexity of coastal areas where aquaculture is located, and poorly represent the environmental variabilities to which cultured organisms are subjected. Consequently, most aquaculture planning and management decisions require information at a much finer scale. If climate projections do not adequately represent conditions experienced at aquaculture sites, potential impacts could be missed, adaptation strategies may be inappropriate, and time and resources could be spent implementing ineffective measures. To demonstrate this, we focus on sea temperature and the production of Atlantic salmon (Salmo salar) in Norway, the world's leading salmon producer and a country with a latitudinal range that exemplifies the challenges related to generalization of farming practises. The results show that if coarse resolution climate model temperatures were used directly, then impacts on salmon culture could be severely over or underestimated. For overlapping reference periods, the average daily modelled temperatures at selected sites frequently differed by several degrees, with the largest differences being over 6 °C, when compared to daily average farm measurements. This has serious biological and economic implications as potential risks to production could be underestimated unless corrected. Here two bias-correction techniques were used to calibrate the climate projections to farm scale and shown to more accurately reflect the conditions experienced. The calibrated future projections for RCP4.5 suggest increased temperatures at all sites may require adjustments to existing farm management practices, but the nature and severity of the impact will vary with location. Our research clearly shows that local scale conditions must be considered, using locally resolved climate projections, to develop meaningful adaptation plans to meet the growing demand for seafood in a changing climate.publishedVersio

The importance of calibrating climate change projections to local conditions at aquaculture sites

Future climate projections are usually only available at global or coarse scale and the focus is often on long-term global or regional averages. Though useful to analyse general trends and identify potential risks and opportunities internationally, these resolutions are unable to capture the complexity of coastal areas where aquaculture is located, and poorly represent the environmental variabilities to which cultured organisms are subjected. Consequently, most aquaculture planning and management decisions require information at a much finer scale. If climate projections do not adequately represent conditions experienced at aquaculture sites, potential impacts could be missed, adaptation strategies may be inappropriate, and time and resources could be spent implementing ineffective measures. To demonstrate this, we focus on sea temperature and the production of Atlantic salmon (Salmo salar) in Norway, the world's leading salmon producer and a country with a latitudinal range that exemplifies the challenges related to generalization of farming practises. The results show that if coarse resolution climate model temperatures were used directly, then impacts on salmon culture could be severely over or underestimated. For overlapping reference periods, the average daily modelled temperatures at selected sites frequently differed by several degrees, with the largest differences being over 6 °C, when compared to daily average farm measurements. This has serious biological and economic implications as potential risks to production could be underestimated unless corrected. Here two bias-correction techniques were used to calibrate the climate projections to farm scale and shown to more accurately reflect the conditions experienced. The calibrated future projections for RCP4.5 suggest increased temperatures at all sites may require adjustments to existing farm management practices, but the nature and severity of the impact will vary with location. Our research clearly shows that local scale conditions must be considered, using locally resolved climate projections, to develop meaningful adaptation plans to meet the growing demand for seafood in a changing climate

Insight into real-world complexities is required to enable effective response from the aquaculture sector to climate change

This study demonstrates how a comprehensive knowledge base can be used by the aquaculture industry, researchers, and policymakers as a foundation for more targeted and detailed climate change impact analysis, risk assessments and adaptation planning. Atlantic salmon (Salmo salar) production in Norway was used as a case study and to illustrate the need to consider impacts from multiple stressors across different production stages and the wider supply chain. Based on literature searches and industry news, a total of 45 impacts and 101 adaptation responses were identified. Almost all impacts were linked to multiple climate stressors, and many adaptation responses can be used for a range of impacts. Based on the research, a move towards more targeted and detailed assessments is recommended. This can be facilitated through a strong knowledge base, further research to address complexities, and better communication between all stakeholders. The results also demonstrate the need for more climate change research that reflects the challenges that the aquaculture sector faces, where multiple stressors and the range of impacts across production stages and the wider supply chain are included. Highlighting the wide range of stressors, impacts and adaptation responses provides a more holistic understanding of the real-world complexities that aquaculture producers face. This again could facilitate adoption of more effective responses to climate change needed to maintain or increase production sustainably