The use of lumpfish as cleanerfish for salmonid aquaculture is a novelty and as a result, many aspects of lumpfish culture have yet to be perfected. Studies addressing juvenile stocking density and tank modifications to optimize growth and functionality, areas that may improve fish production, are foci of on-going research at the University of New Hampshire Coastal Marine Laboratory.
Juvenile lumpfish can be cultured at high densities compared to many other species, however, the optimal stocking density is unknown. Because lumpfish have ventral suckers and adhere to any smooth surface, growers often use available surface area as a way to calculate the amount of fish to stock into a system. However, lumpfish are cannibalistic so overstocking a tank may prove counterproductive for operations. Using common garden experiments with 3-liter tanks as experimental units, we are testing various densities ( 10-40 g/L) with age-0 fish. Growth rate, survival, and aggressive behaviors are the metrics being used to identify best stocking densities for small lumpfish.
Lumpfish will stick to any available smooth surface, including the tank bottom, making routine tank cleaning and waste removal difficult, often resulting in many fish being siphoned off of the bottom inadvertently. Further, while live feed is not necessary from a fish developmental standpoint and, on one hand, Artemia replacement diets may simplify larval rearing, their use requires increased tank cleaning during a fragile ontogenetic period. With those limitations in mind, a series of tank modifications are being evaluated to improve lumpfish rearing tanks using colors, textures, lighting, and drainage options to increase fish survival yet aid in waste removal. Growth and mortality rates as well as behavioral metrics (tank location preference) and scalability are being used to identify which tank modifications show the most promise for commercial production of lumpfish.
The outcome from these experiments will result in greater and more profitable lumpfish production in hatcheries and grow-out facilities to support cleanerfish use in salmonid farms.