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Emergence time and skin melanin spot patterns do not correlate with growth performance, social competitive ability or stress response in farmed rainbow trout

Gesto, Manuel; Skov, Peter V. and Jokumsen, Alfred (2017) Emergence time and skin melanin spot patterns do not correlate with growth performance, social competitive ability or stress response in farmed rainbow trout. [Initiel fødesøgningsadfærd (tidspunkt) og hud melanin pletter korrellerer ikke med vækst, sociale kompetitive egenskaber eller stress respons hos opdrættet regnbueørred.] Frontiers in Neuroscience, 11, pp. 1-10.

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Online at: http://journal.frontiersin.org/article/10.3389/fnins.2017.00319/full

Summary

In wild salmonid fish, specific individual behavioral traits have been correlated with the timing of fry emergence from their gravel spawning nests; Early emerging fish display more aggressive behavior and have a higher probability of becoming socially dominant, compared to fish that emerge at a later stage. Apart from aggression and dominance, other behavioral and metabolic traits, such as boldness, metabolic rate, or growth, have also been linked to emergence time. Altogether, the traits of early- and late-emerging fish resemble those of the proactive and reactive stress-coping style, respectively. As proactive fish are considered more resilient to stress, it may be desirable to select these for aquaculture production. However, it is currently unclear to what extent the link between emergence time and stress-coping styles is maintained in the selective breeding of farmed fish. In the present study, eyed eggs from a commercial supplier were hatched, and larvae fractionated according to their emergence time. Later on, juvenile fish from different emergence fractions were subjected to a stress challenge and also tested to evaluate their competitive ability for food. Beyond some slight dissimilarities in the acute stress responses, emergence fraction displayed no correlation with growth rates, or the ability to compete for feed. Within the whole group of fish utilized in the experiments, no relationship between skin melanin spot pattern and growth performance, stress response intensity, or competitive ability was found. Altogether, the differences in physiological traits related to emergence time were not as strong as those found in earlier studies. It is hypothesized, that the origin and degree of domestication of the fish might be partly responsible for this. The predictive value of skin spots or emergence time to infer the fish stress coping style in farmed fish is also discussed.

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 knytter 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). Samlet set var korellationerne mellem fysiologiske træk og initial fødesøgningsadfærd ikke så udtalte som fundet i andre studier. Dette kan måske hænge sammen med fiskenes oprindelse og graden domesticering. Værdien af hudpletter eller initiel fødesøgningsadfærd i forhold til håndtering af stress hos opdrætsfisk bliver diskuteret.

EPrint Type:Journal paper
Keywords:stress-coping style; emergence time; rainbow trout; skin pigmentation; dominance; growth;
Subjects: Animal husbandry > Production systems
Animal husbandry > Breeding and genetics
Animal husbandry > Health and welfare
Animal husbandry > Production systems > Aquaculture
Research affiliation: Denmark > Organic RDD 2 > RobustFish
DOI:10.3389/fnins.2017.00319
Deposited By: Jokumsen, Senior Advisory Scientist Alfred
ID Code:31479
Deposited On:26 May 2017 09:16
Last Modified:25 Sep 2017 13:34
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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