Frontiers in Marine Science (Oct 2015)
Marking of burbot Lota lota (L.) juveniles using commercial feed as a vector of fluorochrome application
Abstract
The effectiveness of restocking is an important element of sustainable fishery. In restocking programmes, where larvae and juveniles are used mass marking is carried out with non-toxic dyes such as fluorochromes transferred into the fish body by immersion or with feed. The experiment was carried out to assess the possibility of using commercial feed supplemented Alizarin Red S (ARS) as an alternative non-invasive method for the mass marking of burbot fry. Fish of an average body weight of 1.8 (± 0.2) g were reared in separated 10 dm3 tanks and fed for 10 days with extruded feed supplemented ARS in six concentrations, i.e. 0 (control), 20, 40, 60, 80 and 100 g fluorochrome per kg of feed at a daily dose of 5% of biomass. During the next 15 days fish were fed commercial feed without ARS. After 25 days of rearing 30 individuals were sampled from each group, euthanized and total length and wet body weight of each fish were determined. Next, the sampled fish were preserved in 70% ethyl alcohol. Then otoliths were excised from the fish and analysed under a fluorescence microscope to identify fluorescent tags. Marked individuals were identified in each analysed group provided with feed supplemented ARS. The highest rate of marked fish (100%) was found in the group that received 40 g ARS per kg of feed, and the lowest (73.3%) in the group that received 60 g ARS per kg of feed. Supplementation of feed with ARS had no negative effect on the survival rate and growth parameters (mean body weight and total body length) of burbot. The results suggest that ARS applied in commercial feed (40 g/kg for about 7-10 days) is an effective method for marking burbot fry and can be recommended in fishery practice.
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