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Ben Whittaker on personality profiling for lumpfish
Lumpfi sh with personality
Profi ling the behaviour of individual fi sh gives a clue as to why some are better at tackling sea lice than others
BY BEN WHITTAKER
LUMPFISH are deployed into salmon farms to help control outbreaks of sea lice, but just how eff ec� ve these cleaner fi sh are in preven� ng parasites from infec� ng salmon is a ma� er of ongoing debate.
While research has found salmon from cages stocked with lumpfi sh have infec� on rates 60–100% � mes lower than salmon from cages without lumpfi sh, dietary analysis has revealed that the vast majority of lumpfi sh in cages do not eat sea lice. Furthermore, recent reviews have cri� cised the high level of varia� on in parasite control between farms stocked with cleaner fi sh and note that behavioural interac� ons between lumpfi sh and salmon are very rarely documented. Understanding this high varia� on in cleaning behaviour may help unlock the full poten� al of lumpfi sh as cleaner fi sh, leading to more sustainable and effi cient methods of controlling sea lice in aquaculture.
There are many reasons why some lumpfi sh might be be� er suited to cleaning salmon than others. Gene� c background, health and welfare, and the environment in which fi sh are raised are all thought to contribute towards the behaviour of cleaner fi sh in farms. However, diff erences in the psychology of individuals may be an overlooked factor infl uencing varia� on in cleaner fi sh performance.
Researchers from the Centre for Sustainable Aqua� c Research at Swansea University developed a series of behavioural tests to measure personality diff erences across a cohort of lumpfi sh. This included tests to record ac� vity levels, how individuals coped with stress, their willingness to take risks and aggression levels, and to compare how social each individual was within the cohort. Tests were repeated twice to check that behavioural responses were consistent and the scores were then used to build an individual personality profi le for each lumpfi sh.
The lumpfi sh were then introduced into a tank containing 10 Atlan� c salmon smolts and an observer watched to record how the two species interacted. These interac� ons included co-opera� ve behaviours that would be benefi cial for cleaning in a farm environment, such as lumpfi sh moving closer to visually inspect salmon. Antagonis� c behaviours were also recorded to give context on interac� ons that are not desirable in farms – for example, lumpfi sh causing salmon to fl ee.
The results showed that a majority of lumpfi sh ignored salmon. However, individuals that scored higher for “bold and non-aggressive” personality traits spent longer � me periods engaging in co-opera� ve behaviours, while individuals that scored higher for “ac� ve and social” personality traits displayed more antagonis� c behaviour. This suggests that the individual personality of a lumpfi sh aff ects how it will interact with salmon, and therefore how eff ec� ve it will be at removing sea lice.
These fi ndings may account for the high varia� on detected by previous studies in sea lice consump� on and cleaning effi ciency of lumpfi sh.
Above: Ben Whi� aker Below: Lumpfi sh at CSAR Opposite: Novel lumpfi sh test, CSAR
Perhaps only a small number of individuals are cleaning sea lice from salmon and therefore they have a dispropor� onate eff ect on parasite control in farms. These personality tests provide a tool for iden� fying produc� ve individuals and give insight into the psychology of these so-called “elite” lumpfi sh.
However, the research also raises two important ques� ons: how can the effi ciency of elite lumpfi sh be harnessed in farms, and what can be done with the non-cleaning individuals?
Ongoing research collabora� on between the University of Guelph and Fisheries and Oceans Canada aim to adapt these new personality tests for a commercial scale, screening behaviour of greater numbers of lumpfi sh at faster rates than has previously been possible. Not only will this help iden� fy elite lumpfi sh to be deployed into Canadian salmon farms, but gene� c research on the heritability of these behavioural traits might inform selec� ve breeding programmes to domes� cate lumpfi sh stocks. Results from the Canadian lumpfi sh can also be compared to the Bri� sh study to assess whether behavioural diff erences exist between dis� nct geographic popula� ons across the Atlan� c.
It is es� mated that more than 50 million lumpfi sh are produced by hatcheries each year, yet moun� ng evidence suggests the majority of these are not eff ec� ve cleaner fi sh. Further research is needed to be� er understand why so many individuals do not clean and what steps can be taken to improve their produc� vity in farms. For example, will raising lumpfi sh with new diets, tank enrichment or environmental condi� ons aff ect their personality and therefore cleaning ability? Could elite cleaners be used as teaching aids to demonstrate desired behaviours to their non-cleaning counterparts? Will non-cleaners feed on net bio-foul and thereby help maintain farm equipment?
It is hoped that by further developing behavioural tools, research can empower hatcheries to produce higher-quality cleaner fi sh and reduce the need for produc� on in mass quan� � es. Not only would this be more economic and sustainable for the industry, but it will help create condi� ons that benefi t the health and welfare of cleaner fi sh and salmon alike. Aquaculture research has tradi� onally focused on fi sh physiology in order to maximise growth rates and increase yields, but this study demonstrates that shi� ing perspec� ve to focus on fi sh psychology may provide new avenues for improvement and success. Ben Whitt aker is a Postdoctoral Fellow at the Department of Integrati ve Biology, University of Guelph, Canada.
Details of the research can be found online in Applied Animal Behaviour Science, October 2021 (“Personality profi ling may help select bett er cleaner fi sh for sea-lice control in salmon farming”, Benjamin Alexander Whitt aker, Sofi a Consuegra and Carlos Garcia de Leaniz). FF
Lumpfi sh: they do make a difference
“It works! Lumpfi sh can signifi cantly lower sea lice infesta� on in large-scale salmon farming”. Biology Open, September 2018 (Albert Kjartan Dagbjartarson Imsland et al), details a study into the eff ec� veness of lumpfi sh as cleaners in salmon farming. Lumpfi sh were introduced into sea cages alongside Atlan� c salmon, while other cages contained only salmon, as a control. The researchers found that the presence of lumpfi sh was associated with lower numbers of parasites, including female sea lice L. salmonis), and there was also an inverse correla� on between the density of lumpfi sh in the cage and the recorded levels of sea lice. Another study (Kirs� n Eliasen et al, Aquaculture, March 2018) indicates, however, that the appe� te of lumpfi sh for ea� ng sea lice depends on what other food sources are available. When zooplankton are plen� ful, lumpfi sh consume sea lice less readily, so their eff ec� veness as cleaner fi sh is likely to be seasonal as the numbers of zooplankton rise and fall.
