Farming of juvenile Lumpfish (Cyclopterus lumpus). Growth pattern, anesthetic protocol, and salinity tolerance.
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- Institutt for biologi 
Sea lice (Lepeophtheirus salmonis) infestation is currently one of the biggest challenges within the Norwegian Atlantic salmon (Salmo salar) industry, causing major expenses and limiting further production growth. Traditional chemical delousing methods have lost efficiency, and the use of cleaner fish has thus increased accordingly. As the use of wild caught wrasse (Labridae) do not seem to be a sustainable solution, farming of cleaner fish has been initiated, and the production of lumpfish (Cyclopterus lumpus) has increased tremendously over the last few years. Periodically high mortalities of farmed juvenile lumpfish demonstrate the need for a better understanding of the species biology and physiology. The present work has established a growth pattern relation between body weight and body length, body height, and skull height. Further studies revealed large individual variations in body weight within farming tanks indicating the need for adjusting or developing present rearing routines. The results also indicated that pelagic (swimming) lumpfish were larger than the juveniles attached to the walls and bottom of the farming tanks. Mortality and the substantial presence of tail damages on both the dead and live lumpfish indicate stress, also suggesting that current rearing conditions are suboptimal. Such conditions could also be related to light conditions varying in both production hall and farming tanks. The anesthetic chemicals tested induced surgical anesthesia of lumpfish fries within (the preferred) 3-5 minutes at concentrations of 18 mg/L (Aqui-S), 37,5 mg/L (Benzoak), and 60 mg/L (buffered MS-222). Aqui-S had low safety margin and was therefore not considered suitable for prolonged exposures, while the fish made a rapid recovery from both Benzoak and MS-222, even after 20 minutes of exposure. Changes in exposure temperature impacted on lumpfish anesthesia, and increased temperature (18oC) delayed recovery time. Results from physiological studies demonstrate that the lumpfish fries and juveniles exhibit a significant capacity to withstand reduced environmental salinity. This lumpfish euryhalinity may be exploited by rearing lumpfish in brackish water (which could reduce the animals osmoregulatory costs), and should also be tested as prophylaxis or treatment against presence of infective/parasitic stenohaline organisms.