Mucosal defences of salmonids in complex RAS environments

Area of Science:

• Aquatic immunology
• Fish health management
• Aquaculture systems

Background:

• Mucosal barriers are crucial primary defences for fish against environmental challenges.
• Intensive aquaculture, especially recirculating aquaculture systems (RAS), subjects fish to unique pressures.
• Understanding RAS impacts on mucosal immunity is vital for fish welfare.

Purpose of the Study:

• To review current knowledge on environmental variables in RAS and their effects on fish mucosal defences.
• To identify knowledge gaps regarding RAS impacts on salmonid mucosal immunity.
• To highlight the need for functional immunological assessments in RAS-reared fish.

Main Methods:

• Literature review consolidating studies on RAS environmental variables and fish mucosal defences.
• Focus on salmonid species and mucosal organs (skin, gills, gut, olfactory).
• Evaluation of existing histological data and identification of limitations.

Main Results:

• RAS environments present physical, chemical, and microbial challenges to fish mucosal surfaces.
• Impacts of RAS parameters on overall fish health are partially documented, but specific mucosal health consequences are unclear.
• Most research focuses on gill defences, with limited data on other mucosal sites and functional immunological insights.

Conclusions:

• Optimizing RAS production requires a deeper understanding of how the environment affects mucosal barriers.
• Mucosal surfaces offer insights into rearing conditions and are key to fish health and welfare in aquaculture.
• Functional immunological studies are needed to complement histological data for a comprehensive understanding of RAS impacts.