Introduction
Burbot (Lota lota) gains attention in European intensive coldwater aquaculture due to its delicate
white fillets, high nutritional value comparable to its relative, Atlantic cod, and valuable by_products
such as liver, roe, and skin. Burbot exhibits environmental requirements similar to those of trout and
achieves comparable growth rates, while demonstrating greater hardiness and lower disease
susceptibility than other salmonids. These characteristics position burbot as a promising candidate
for diversifying inland freshwater aquaculture (Oliver et al., 2024). Since 2012, commercial hatcheries
have emerged in Belgium and Germany and fingerling availability is no longer a bottleneck. Although
burbot aquaculture remains in its early stages, Oliver et al. (2024) indicate that culture methods are
now adequate for commercial production. However, no studies have been conducted on the long
term effects of feeding levels on growth of juvenile burbot weighing over 30 g (Trejchel et al., 2014).
The aim of this study is to determine the effect of feeding levels on growth, condition and body
composition of growing juvenile to subadult burbot in RAS to identify the true optimal feeding level.
Materials and methods
In 15 cylindrical 120 L tanks, 60 fish were stocked per tank, of which 32 were individually PIT-tagged.
The fish had an average individual body weight of 34.66 ± 7.24 g. All tanks were connected to a single
intensive RAS, and the temperature was maintained at 15 °C. Five treatments, each in triplicate, were
assigned feeding levels ranging from 0.75 to 2.15% of biomass per day. Fish were fed a commercial
diet (Protec, 3 mm, Skretting) using automatic feeders.
Every three weeks, all fish were sedated and sampled. Of each PIT_tagged fish, body weight and length
were recorded. Specific growth rate (SGR), thermal growth coeficient (TGC) and Fulton’s condition
factor (K) were calculated. Total biomass per tank was measured to determine daily feed rations for
each treatment and to calculate the biological feed conversion ratio (FCRb). After the final sampling in
week 15, whole-body proximate composition was determined for six randomly selected pooled fish
per tank. In addition, the viscerosomatic index (VSI), hepatosomatic index (HSI), and Carcass Yield
were measured in eight randomly selected individual fish per tank.
Results and discussion
SGR and TGC increase with feeding level but level off from 1.45% feeding level, while FCRb steadily
increases with further increasing feeding level. Therefore, the optimal feeding level is around 1.45%
body weight per day, where SGR is near maximal and FCRb remains relatively efficient. A feeding level
of 1.10% will result in a more efficient FCRb with only a minor reduction in growth (Figure 1). Fulton’s
condition factor (K) was lower in only the 0.75% feed level treatment (Table 1). Hepatosomatic Index
(HSI) was significantly higher in the 1.45%, 1.80% and 2.15% feeding level treatments compared to
0.75%, while no statistic differences could be shown for Carcass Yield (data not shown).
Acknowledgment
This research was funded by the European Union & the Flemish government through the ‘European
Maritime, Fisheries and Aquaculture Fund (EMFAF)’ & ‘het Financieringsinstrument voor de Vlaamse
Visserij en Aquacultuursector (FIVA)’ grant for the AquaPlanner project.
References
Oliver, L.P., Myrick, C.A., Fornshell, G., Cain, K.D. (2024) Life history and aquaculture methods for burbot (Lota
Lota). Reviews in Fisheries Science & Aquaculture, Vol 32(2), 369-386,
https://doi.org/10.1080/23308249.2024.2308917
Trejchel, K., Żarski, D., Palińska-Żarska, K., Krejszeff, S., Dryl, B., Dakowski, K., Kucharczyk, D. (2014)
Determination of the optimal feeding rate and light regime conditions in juvenile burbot, Lota lota (L.) under
intensive aquaculture. Aquacult Int, Vol (22), 195–203, https://doi.org/10.1007/s10499-013-9670-5