News & Views Research
Light and density adjustments reduce lumpfish aggressiveness: study

Researchers have found that hatcheries can reduce lumpfish aggressiveness toward younger lumpfish by altering light conditions and fish densities inside tanks.  

“Lumpfish are crucial in addressing the high demand for cleaner fish in salmonid farming, but their aggressive behaviour, including cannibalism, poses a challenge,” said station scientist Elizabeth Fairchild, a research associate professor with UNH’s College of Life Sciences and Agriculture (COLSA). “Understanding the factors that exacerbate lumpfish aggression, and providing guidelines for mitigating this behaviour to aquaculturists, are essential for increasing hatchery production and rearing efficiency.” 

The researchers at the University of New Hampshire and the New Hampshire Agricultural Experiment Station, found that especially for smaller lumpfish, instances of tail fin nipping as a sign of aggression lessened when the fish had 12 hours of light followed by 12 hours of dark (versus constant light) and when the density of fish was reduced.

These management conditions become less influential as lumpfish grow larger, allowing for more flexibility in rearing practices, said Fairchild. However, further research is needed to explore the long-term impacts of these conditions and to develop comprehensive guidelines for lumpfish rearing. 

The researchers said that integrating lumpfish, a cleaner fish that feeds on sea lice off salmon, into aquaculture farms is a sustainable mitigation strategy. The most impactful species, Lepeophtheirus salmonis, can cost an estimated $1.3 million per farm over a two-year production cycle in sea lice infestation management. 

Fairchild and her co-authors, Brittany Jellison, an assistant professor in UNH’s biological sciences department, and Shelby Perry, a master of science student in COLSA’s marine biology program published their research in the North American Journal of Aquaculture. 

The current mitigation methods for sea lice, including waterjets, hot water showers and other mechanical and thermal treatments, aren’t fully effective and can harm the fish, resulting in lower growth and survival rates for the salmon.  

Perry said finding the best environmental conditions for lumpfish development is crucial, as it enhances their effectiveness as cleaner fish in aquaculture settings.

“By adopting these recommendations, fish farmers can improve lumpfish hatchery production, reduce juvenile mortality and enhance the sustainability of salmonid farming through effective sea lice management,” she said. “And increasing aquaculture sustainability and efficiency is vital to meeting the future demand for animal protein, as well as protecting the planet we live on.”