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Costs and benefits of farming fish with selected behavioural and physiological traits

Skov, Peter Vilhelm; Gregersen, Joao de Jesus and Jokumsen, Alfred (2015) Costs and benefits of farming fish with selected behavioural and physiological traits. [Omkostninger og fordele ved opdræt af økologiske fisk med udvalgte adfærds og fysiologiske træk.] Paper at: Aquaculture 2015 – Cutting Edge Science in Aquaculture, Montpellier, France, 23-26 August 2015.

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Summary

The timing with which salmonid larvae emerge from their gravel nests is considered to be associated with a particular suite of behavioural and physiological traits. In aquaculture, traits of interest to production include aggressiveness, dominance and resilience to stress. The earliest emerging fraction is generally considered to possess these traits, and fish in this fraction may be perceived as being more robust. It is speculated that there may be advantages to selectively farm fish that are more robust, particularly if feed utilization is improved and disease is less prevalent. In the present study a series of experiments were performed, with the purpose of characterising behavioural, metabolic and production related traits in rainbow trout juveniles.
Three batches of 3.000 eggs were hatched and sorted into 5 fractions of 20%. The early (0-20%), middle (40-60%), and late (80-100%) fractions were retained and maintained on
commercial diets. Feed conversion was assessed on groups fed fixed rations, during a period when fish grew from approximately 12 to 50 grams. This revealed no significant differences in feed conversion between the three fractions. To determine if the different fractions could be characterised by distinct behavioural responses to stress, a second experiment was performed in which the response to a startle was quantified in behavioural arenas. Early emerging fractions had a significantly higher fraction of fish to re-appear, and tended to take shorter time to do so.
Resting oxygen consumption revealed no differences in standard or maximum metabolic rate, but the early emerging fraction had significantly lower post-stress oxygen consumption and shorter recovery times. When fasted for 10 days, the early fraction lost significantly more body mass, whereas the middle fraction gained significantly more weight during re-feeding. This was observed in individual experiments, as well as in group experiments under heavily restrictive feeding regimes.

Summary translation

Tidspunktet for hvornår lakse- og ørred yngel stiger op (swim-up) fra deres skjul i gruset i bunden af vandløb antages at være forbundet med adfærdsmæssige og fysiologiske træk. I praktisk akvakultur er de mest interessante egenskaber aggressivitet, dominans og robusthed for stress. Eksperimenterne viste at swim-up fraktionerne (tidlig-mellem-sen) adskilte sig i forhold til visse adfærds og fysiologiske egenskaber men ikke i andre.
”Tidlig swim-up” fraktionerne var mere robuste; de viste mere udfarende adfærd og ”kom sig” hurtigere efter at være blevet stresset sammenlignet med ”mellem” og ”sen” swim-up fractionerne.
Der var ingen væsentlige forskelle i de udførte stofskifte målinger mellem grupperne. Dog viste ”tidlig swim-up” lavere ilt-gæld efter stress, ligesom disse grupper hurtigere var tilbage på standardstofskifte.
“Tidlig swim-up” havde et lavere cortisol respons efter stress ved lav vandstand, mens mobilisering af glykogen depoter ikke var væsentlig forskellig mellem grupperne.
”Tidlig swim-up” grupperne havde det største vægttab efter 10 dages sult, som formentlig hang sammen med det generelt højere aktivitets niveau. ”Mellem-grupperne” var de mest sult-tolerante, og var de hurtigste til at indhente vægttab ved genoptagelse af fodring. ”Tidlig-swim-up” grupper viste således ikke umiddelbart nogen konkurrencemæssig fordel under restriktiv fodring, hvor mellem-grupperne tilsyneladende klarede sig bedst.
“Mellem swim-up” grupperne syntes således i denne forsøgsserie at have de bedste produktionsmæssige egenskaber.

EPrint Type:Conference paper, poster, etc.
Type of presentation:Paper
Keywords:Robustness, Metabolism, Behaviour, Growth, trout
Subjects: Animal husbandry > Feeding and growth
Animal husbandry > Health and welfare
Research affiliation: Denmark > Organic RDD 2 > RobustFish
Deposited By: Jokumsen, Senior Advisory Scientist Alfred
ID Code:29294
Deposited On:30 Sep 2015 12:05
Last Modified:30 Sep 2015 12:06
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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