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First feeding behavior: A potential tool to select robust trout for organic aquaculture

Gesto, Manuel (2016) First feeding behavior: A potential tool to select robust trout for organic aquaculture. [Fødesøgnings adfærd som et muligt redskab til at udvælge robuste ørreder til økologisk akvakultur.] ICROFS News, 13 October 2016, pp. 1-2.

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Summary

In wild salmonid fish, individual behavioural traits have been suggested to be coupled with the timing of fry emergence form gravel spawning nests, in such a way that early emerging fish have shown to be more aggressive and to have a higher probability to become socially dominant than those fish emerging at a later stage. Besides aggression and dominance, other behavioural and metabolic traits such as boldness, metabolic rate or growth had also been coupled to emergence time. Altogether, early- and late-emerging fish have traits resembling those of proactive and reactive stress coping styles, respectively. Proactive fish are considered to be more resilient to stress. However, it is currently unclear if that coupling is maintained in farmed fish populations, which showed no consistent evidence of a clear relation between emergence time and stress coping style. In this study, fish were hatched and larvae were fractionated according their emergence time (Early fraction: first 20 % of fish to emerge; Intermediate fraction: mid 20 %; Late fraction: last 20 %). Several months later, the resilience against a mild stressor (30 min of high stocking density), along with the stress habituation ability was investigated in 5 g fish from the different fractions. Results showed that fish from different fractions played a similar neuroendocrine response to a novel stressor. Interestingly, the capacity of habituation to stress was however better in the fish from the early emergence fraction, which showed no cortisol response to the stressor after being exposed daily for 15 days to another mild acute stressor (1.5 min of air exposure). These results demonstrate that at least some behavioural differences related to emergence time exist in a domesticated trout population. The aquaculture related implications of these stress resilience differences are currently under study.

Summary translation

Adfærdsmæssige træk hos laksefisk i naturen menes at være koblet til tidspunktet for fiskeynglens opstigning fra gydegruset/”reden” for at søge føde på en sådan måde, at tidligt opstigende fisk har vist sig at være mere aggressive og have større sandsynlighed for at blive socialt dominante i forhold til fisk, der stiger op på et senere tidspunkt. Ud over aggression og dominans, er adfærdsmæssige og metabolske egenskaber også blevet forbundet med tidspunktet for fødesøgning, f. eks. dristighed, stofskifte eller vækst. Samlet set har fisk der udviser henholdsvis tidlig og sen fødesøgning egenskaber, som svarer til fisk med henholdsvis proaktiv og reaktiv stress håndtering. Proaktive fisk anses for mere robuste/fleksible overfor stress. Det er imidlertid uklart hvorvidt denne kobling knitter sig til opdrættede fiskebestande. I dette studium blev nyklækkede fiskeyngel fraktioneret i forhold til deres swim-up adfærd (tidlig fraktion var de første 20 %, som svømmede op; en intermediær tidlig grupppe på 20 %, dernæst en mellemgruppe på 20 %; en intermediær sen gruppe på 20 % og til sidst den sene fraktion på 20 %. Kun 3 grupper blev anvendt i de videre forsøg (tidlig, mellem og sen). Nogle måneder senere blev 5 grams fisk fra alle grupper testet for robusthed i forhold til en mild stressor (30 min. ved høj tæthed). Resultaterne viste, at fisk fra forskellige fraktioner udviste samme neuroendocrine
respons. Men fisk i den tidlige fraktion udviste bedre tilpasning til stress, hvilket blev udtrykt ved manglende cortisol response overfor stresspåvirkningen efter daglig (15 dage) eksponering til en anden mild akut stressor (1.5 min lufteksponering). Disse resultater viser, at der i hvert fald er nogen adfærdsmæssige forskelle i forhold til swim-up adfærd i ørredbestande. Hvad dette betyder i praktisk ørredopdræt undersøges.

EPrint Type:Newspaper or magazine article
Keywords:Robust trout, first feeding behavior, selection, swim-up
Subjects: Animal husbandry > Feeding and growth
Animal husbandry > Health and welfare
Knowledge management > Research methodology and philosophy
Research affiliation: Denmark > Organic RDD 2 > RobustFish
Deposited By: Jokumsen, Senior Advisory Scientist Alfred
ID Code:30760
Deposited On:08 Dec 2016 09:57
Last Modified:08 Dec 2016 09:57
Document Language:English
Status:Published
Refereed:Not peer-reviewed

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