Survival of brown trout fry in nature: effects of activity, body size and starvation
Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
The first year of life is one of the main survival bottlenecks for many fish species. Individual traits affecting survival can be morphological, physiological or behavioural. Body size, growth rate and activity have all been found to affect fitness in different organisms. However, the effects of these traits on fitness in natural conditions and for underyearlings are poorly investigated. In this study we attempted to induce compensatory growth in laboratory conditions in natural populations of brown trout fry (Salmo trutta). It was performed by exposing the fry to a period of restricted resources followed by a period of refeeding. Two behavioural trials were conducted on each individual where activity level was scored. All fish were subsequently released in their native stream and recaptured after a month to check for survival. We found that high individual activity level in an open field context increased the probability of survival under natural conditions. The importance of body size for survival decreased over time, and thus, with fish size. Full compensation was detected in body condition, while only partly compensation in weight and no compensation in length were detected during the experimental periods. Our results suggest that a brown trout fry’s individual activity level is repeatable and can be an important trait for selection in nature. The instable interactions between activity and life-history traits indicate environmental effects on these interactions. Furthermore, if body size is not the only trait affecting survival, compensation in body structures may not be a fast response to increase fitness after a period of growth depression.
Place, publisher, year, edition, pages
2014. , 33 p.
Brown trout, fry, activity, survival, body size, compensatory growth, starvation
IdentifiersURN: urn:nbn:se:liu:diva-109488ISRN: LiTH-IFM- Ex--14/2902--SEOAI: oai:DiVA.org:liu-109488DiVA: diva2:739190
Subject / course
2014-05-23, Schrödinger, Linköpings Universitet, Linköping, 11:19 (English)
Johnsson, Jörgen, ProfessorHargeby, Anders, Universitetslektor
Bergman, Karl-Olof, Docent