Understanding the Impact of Temperature on Salmon Health and Development
A Scientific Study Uncovers Surprising Results – In a recent trial conducted by researchers at Nofima, the significant role of temperature in the health and growth of Atlantic salmon was explored. While the fish developed as predicted at various temperatures during their rearing process, an unexpected outcome emerged upon transferring them to seawater.
The Role of Temperature in Fish Biology
The primary objective of this study was to investigate how varying temperatures affect salmon health and development throughout their lifecycle. Temperature serves as a crucial regulator in fish biology, influencing their behavior, physiology, health, welfare, and growth. Prior to smoltification — the process that prepares salmon for life in seawater — temperature is an effective management tool for controlling growth rates.
Recently, there have been rising concerns about potentially excessive temperatures during the rearing process. Adverse outcomes, such as compromised heart health and poor performance in fast-growing juvenile salmon (parr), have led to increased scrutiny from the Norwegian aquaculture industry.
The Need for Long-term Data
Driven by these concerns, Nofima scientists initiated a long-term study to explore the ramifications of temperature from the smolt phase to harvest. “There was a lack of long-term experiments assessing the effects of temperature from smolt to harvest,” noted researcher Anja Striberny. “We needed to determine whether elevated temperatures early in life would influence later growth and health among salmon.”
Trial Overview
This groundbreaking experiment took place at Nofima’s aquaculture research station in Sunndalsøra, situated on Norway’s west coast. The facility is equipped for varied trials on both small and large salmon in diverse environmental conditions.
Researchers monitored Atlantic salmon from an initial weight of 10 grams, tracking their development up to the smolt stage (approximately 200 grams). Groups of fish were reared at temperatures of 8, 12, or 14 degrees Celsius using both flow-through and recirculating aquaculture systems (RAS). After smoltification, the fish were transferred to seawater at Gildeskål in Northern Norway for continuous monitoring of health and welfare.
Key Findings from the Study
The majority of results aligned with expectations:
- All fish exhibited good seawater tolerance.
- Changes in photoperiod significantly influenced smolt development, indicating that light exposure may play a more critical role than temperature in this process.
- High survival rates in seawater were observed among all groups.
- As anticipated, fish reared at higher temperatures were significantly larger at the time of seawater transfer, with the 14°C group averaging 140 grams compared to just 70 grams for the 8°C group.
Nevertheless, researchers were surprised to find that fish from the higher temperature group continued to grow at a faster rate during their time in seawater. The cause of this phenomenon remains unclear — whether it results from enhanced growth rates during smolt production or simply a higher body weight at the time of transfer.
While growth and survival rates are critical metrics, the team is also examining tissue samples to assess more subtle, or “invisible,” effects. Their preliminary analysis suggests minor differences in welfare indicators; however, notable concerns include a trend towards mild cataract development and smaller heart sizes in fish that experienced higher temperatures.
Contextualizing the Results
This research was funded by the Norwegian Seafood Research Fund (FHF), and Sven Martin Jørgensen, Head of Research, emphasizes the importance of contextualizing these findings. “It is vital to compile results from various projects to offer the aquaculture industry updated insights regarding optimal early production conditions for achieving the best possible health and performance in farmed salmon.”
Moreover, the scientists explored how initial rearing conditions could affect the final product. Interestingly, the groups reared at 12 and 14 degrees displayed a higher proportion of fish with superior quality, including a trend towards more vibrant fillet coloration.
Conclusions and Considerations
In conclusion, this study shows that rearing salmon at temperatures up to 14 degrees is largely unproblematic and may even yield positive long-term performance outcomes. However, Striberny cautions against the assumption that higher temperatures will automatically lead to rapid growth: “In this trial, we manipulated temperature only, maintaining density and water quality within recommended levels. Altering these parameters could yield different results.”
This pivotal research, part of the Temp-Intens project, was conducted in collaboration with several esteemed institutions, including the Arctic University of Norway (UiT), University of Bergen (UiB), Norwegian University of Science and Technology (NTNU), Mowi, Grieg Seafood, and Cermaq.
Image credit: Anja Striberny, Nofima
