Feeding behaviour and growth of lumpfish (Cyclopterus lumpus L.) fed with feed blocks

Abstract

The aim of this project was to investigate if lumpfish can be fed using specially designed feed blocks instead of regular fish feed pellets. Two studies were performed. In Part I different designs of feed blocks were introduced and fish observed with underwater cameras to record feeding behaviour. Results indicate that lumpfish require feed blocks with grooves in order to graze from them and that the acclimation period is relatively short (2–4 hr) before the fish will use them as a feed source. In the second part of the project two duplicate groups of lumpfish with an initial mean (±SD) weight of 125.4 ± 45.7 g were individually weighed and randomly distributed into six 3.5 m3 circular flow‐through tanks with 45 fish in each tank. Fish in three tanks were fed using feed blocks with grooves and fish in three tanks were fed using a regular commercially available lumpfish extruded feed. Both groups received a daily feeding rate of 2% body/weight. From day 14 onwards, fish fed with marine pelleted feed had a significantly higher mean weight compared to fish fed with feed blocks. Although not significant, the condition factor was higher in the feed block group during the study period. Results from this study show that lumpfish will readily graze from feed blocks if they are presented in a way that allows them to do. In addition, the acclimation period required before the fish will utilize them appears to be short thus potentially allowing for their use in commercial salmon cages.

Comparison of diet composition, feeding, growth and health of lumpfish ( Cyclopterus lumpus L.) fed either feed blocks or pelleted commercial feed

“…Consequently, the objective of the study is to help develop an optimal feeding strategy to maintain healthy lumpfish populations in the hatchery as well as in commercial salmon cages. Based on the positive effect of feed blocks in earlier studies in lumpfish (Imsland, Reynolds, Jonassen, Hangstad, Jónsdóttir, et al, ) and wrasse (Leclercq et al, ) we predict that use of feed blocks will have lead to improved growth, lower prevalence of cataract and improved gut health in juvenile lumpfish.…”

“…The health status of the fish was assessed immediately prior to transfer to Gifas, Inndyr, Nordland, Norway in early January 2017. For further details about the experimental fish see Imsland, Reynolds, Jonassen, Hangstad, Jónsdóttir, et al ().…”

“…This present study is a continuation of studies designed to assess the use of feed blocks for lumpfish populations (Imsland, Reynolds, Jonassen, Hangstad, Jónsdóttir, et al, ). The first study focused on feed block design and deployment to optimize lumpfish, utilizing them as a food source (Imsland, Reynolds, Jonassen, Hangstad, Jónsdóttir, et al, ), while effect on growth and welfare remains to be investigated.…”

“…Feed blocks have been used in salmon cages stocked with wrasse species (Leclercq et al, ) and can be positioned in areas of the cage where the wrasse will be in closer proximity to the salmon thus potentially enhancing grazing potential. In an earlier study (Imsland, Reynolds, Jonassen, Hangstad, Jónsdóttir, et al, ) investigated if lumpfish could be fed using feed blocks and what design of the feed block would facilitate optimal feeding. Results from the study of Imsland, Reynolds, Jonassen, Hangstad, Jónsdóttir, et al () show that lumpfish will readily graze from feed blocks if they are presented in a way that allows them to (feed blocks with grooves).…”

“…In an earlier study (Imsland, Reynolds, Jonassen, Hangstad, Jónsdóttir, et al, ) investigated if lumpfish could be fed using feed blocks and what design of the feed block would facilitate optimal feeding. Results from the study of Imsland, Reynolds, Jonassen, Hangstad, Jónsdóttir, et al () show that lumpfish will readily graze from feed blocks if they are presented in a way that allows them to (feed blocks with grooves). In addition, the acclimation period required before the fish will utilize them appears to relatively short, thus potentially allowing for their use in commercial salmon cages.…”