Is Habituation Measurable in Lumpfish Cyclopterus lumpus When Used as Cleaner Fish in Atlantic Salmon Salmo salar Aquaculture?

Abstract

To investigate how lumpfish interact in Atlantic salmon aquaculture, physiological stress responses and changes in behaviour were analysed in experienced and naive lumpfish. Experienced lumpfish (30.2 ± 7.93 g, mean ± SD) coexisted with a commercial scale production unit of Atlantic salmon (1258.5 ± 152.12 g) for 30 to 60 days, while naive lumpfish (38.2 ± 12.37 g) were kept with conspecifics only. Ten trials from each background were tested. For each trial, 10 lumpfish were tagged and transferred to a video monitored experimental tank (2 × 2 × 0.7 m). In each trial, swimming behaviour was mapped for all lumpfish every 60 s in 20 min, 10 min before, and 10 min after the introduction of four Atlantic salmon. Naive lumpfish expressed significantly increased burst swimming activity and maintained longer interspecific distance to Atlantic salmon in comparison with experienced fish. In addition, mean plasma cortisol levels were significantly elevated in naive fish after exposure to Atlantic salmon. We argue that naive lumpfish expressed innate physiological and behavioural stress responses during first encounter with Atlantic salmon, while reduced responses in experienced individuals indicated habituation. The effect from behavioural and physiological stress in newly deployed naive lumpfish–before and during habituation–should be taken account for when lumpfish are introduced in commercial sea cages to improve welfare for the species. In addition, we suggest that habituation could be applicable during the rearing phase to moderate the transition from a simple tank environment with conspecifics only to interspecies interaction with Atlantic salmon in sea cages.

Tag use to monitor fish behaviour in aquaculture: a review of benefits, problems and solutions

“…2013; Staven et al . 2019). PIT tags were used for identification of individuals, but also used in combination with PIT antennae to register activity of individuals relating to a behaviour (e.g.…”

“…24% of studies that internally implanted telemetry, DST or PIT tags also externally attached non-electronic external marker tags (*External marker tags = coloured tag, Floy, T-bar, numbered Peterson's discs + opercular loop tag FT4) to the same fish to allow researchers to identify tagged individuals for the purpose of tag retrieval or monitoring tagged individuals via video or direct observation. Three studies used only external marker tags as a method to observe individuals for data collection and did not use an accompanying electronic recording tag (Laursen et al 2011;Bui et al 2013;Staven et al 2019). PIT tags were used for identification of individuals, but also used in combination with PIT antennae to register activity of individuals relating to a behaviour (e.g.…”

Personality profiling may help select better cleaner fish for sea-lice control in salmon farming

“…Environmental enrichment can modify risk-taking behaviours in fish very rapidly (Roberts et al, 2011;Roberts et al, 2014) and this could perhaps be used to suppress fear and enhance cleaning behaviour in lumpfish. For example, feeding sea-lice and live prey to lumpfish prior to cage deployment was found to promote subsequent delousing behaviour (Imsland et al, 2019a), and previous exposure to salmon may also reduce stress and improve cohabitation (Staven et al, 2019). In general, intensive fish farming seems to modify fish behaviours in predictable ways, by altering patterns of gene expression in the fish brain that can be targeted by selective breeding (Rodriguez-Barreto et al, 2019).…”

Timing is everything: Survival of Atlantic salmon Salmo salar postsmolts during events of high salmon lice densities

“…To cope with the problems created by lice, various chemical, mechanical/thermal and biological treatments have been, and are still used to delouse fish in aquaculture (particularly in the period where wild fish smolts migrate from the rivers). However, all delousing methods have their limitations; chemical treatments have become less efficient due to resistance (Aaen, Helgesen, Bakke, Kaur, & Horsberg, 2015) and may also pollute the environment, mechanical/thermal and biological treatment has unresolved animal welfare issues as well as increased risk of escapes (both of salmonids and cleaner fish; Brooker et al, 2018; Bui, Oppedal, Sievers, & Dempster, 2019; Overton et al, 2019; Staven et al, 2019). Thus, lice persist as a core challenge for the interaction between aquaculture and wild salmonids.…”