What to feed a marine wolf?

The spotted wolffish feeds on bottom-dwelling organisms like echinoderms, mollusks, and crustaceans. Its natural diet is varied, rich in easily digestible protein and low in lipids. In aquaculture, wolffish are typically fed commercial fish feeds. Are there better ways to feed a marine wolf?

Commercial fish feeds are mainly based on fishmeal and fish oil. They are high in fat and contain few plant-based ingredients. Like many marine species, spotted wolffish are evolutionarily adapted to ingesting large meals and require prolonged digestion times. This is mainly due to slow gastric emptying, as their natural prey—fish and crustaceans—have lots of bones and shells, which disintegrate slowly. In aquaculture, accelerating growth at all life stages is crucial for economic success; it can take up to four years for wolffish to reach a market size of 3-4 kg. Therefore, improving feed efficiency and understanding the nutritional needs of the species are key areas of focus.

Larvae

Spotted wolffish larvae are about 20–25 mm long when they hatch, with only a small yolk reserve remaining, and may begin feeding almost immediately after hatching. Formulated dry feed has most frequently been used as the weaning diet for wolffish. However, variable survival rates during the first 50 days post-hatch, often due to failure to initiate feeding, have posed a challenge. New research is now focused on identifying optimal start-feeding protocols for spotted wolffish larvae.

In a pilot study, we tested two experimental weaning diets for the first 20 days post-hatch—cryopreserved copepods (Calanus spp.) and live cryopreserved nauplii of Semibalanus balanoides (which reactivate after cryopreservation). We used a commercial formulated feed as a control. Larvae fed copepods and Balanus nauplii increased their survival rates from 18% (with formulated feed) to 35% and 45%, respectively. These findings will be further explored and verified in an upcoming project financed by the Mabit-programme in 2025.

Juveniles

Few studies have examined the growth performance of juvenile spotted wolffish in relation to diet, and the commercially available diets for this species have remained unchanged for years. Recent unpublished findings in cod suggest that partially replacing fish meal with crab meal may have beneficial effects on feed intake and gut health by prolonging the gastrointestinal passage rate and increasing nutrient digestibility. A six-month growth experiment testing a standardised commercial diet versus diets with 5% and 15% crab meal added showed similarly high growth rates in all three groups. However, the underlying digestive mechanisms involved—such as gastrointestinal passage rate, enzyme activity, and biochemical and histological indicators—have not yet been analysed.  

Broodstock

The diet of broodstock and the nutrients that parents invest in their offspring are critical for successful reproduction. These nutrients, which include vitamins, proteins, and lipids, are transferred into the egg and sperm cells to support the developing embryos until they can feed on their own after hatching. An experimental broodstock diet, closely resembling the species’ natural diet, was formulated with low lipid content (10–12%) and highly digestible protein sources (krill, squid, and mussel meal). The effect of this diet on egg, sperm, and larval quality, was compared with that of a standard commercial diet (18% fat, with fishmeal as the main protein source). Larvae from parents fed the low-fat diet increased their 50-day survival rates from 35% to 58%. This increased survival was correlated with the lipid composition of the unfertilised eggs.

These findings demonstrate the potential for continuous improvement in commercial culture across all life stages of spotted wolffish. Akvaplan-niva has been working on spotted wolffish R&D since the mid-1990s. At our research station, we maintain a standing broodstock for research activities and to supply the emerging industry with eggs and juveniles. The industry is now on the verge of scaling up commercial production, and the R&D sector in northern Norway will continue to play an important role in closing research gaps to establish farmed wolffish as a profitable and competitive seafood product for Norway.