Biological Control (Cleaner Fish)

Biological control deploys cleaner fish species — primarily ballan wrasse (Labrus bergylta) and lumpfish (Cyclopterus lumpus) — inside salmon cages to graze on fouling organisms growing on the net mesh. The cleaner fish pick at hydroids, barnacles, tunicates, and algae, providing a continuous low-level cleaning action that slows fouling accumulation between mechanical cleaning cycles. Stocking densities typically range from 2-5% of the salmon population, adjusted for cage volume and expected fouling pressure.

This approach carries strong environmental credentials: no chemicals, no mechanical abrasion, and it doubles as a sea lice management tool since wrasse and lumpfish also consume lice stages from salmon skin. In practice, though, results are inconsistent. Lumpfish feed actively in cold water (below 12 degrees C) but become sluggish in warmer months when fouling peaks. Wrasse do the opposite — they feed well in summer but enter torpor during winter. Mortality rates for stocked cleaner fish remain high, often 30-50% per production cycle, raising both cost and animal welfare concerns that have drawn attention from marine biology researchers.

Farms using biological control almost always pair it with at least one other method. The comparison tool shows how cleaner fish complement mechanical cleaning or silicone coatings in different seasonal windows. For operations evaluating whether the investment in cleaner fish husbandry makes financial sense, the cost calculator factors in stocking, mortality replacement, and supplemental feeding costs. Further background on fouling species that cleaner fish target effectively is available in the FAQ section.