The effect of extreme northerly climatic conditions on the life history of the minnow, Phoxinus phoxinus (L.)

• Published in: Journal of Fish Biology
• Main Author: Mills, C. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1988
• Subjects: Arctic; Utsjoki; Lapland
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.1988.tb05498.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.1988.tb05498.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.1988.tb05498.x

Over its exceptionally wide geographical range the minnow displays a remarkable variability in its life history. In southern England many fish mature after one year and few fish survive to their third birthday. Very few fish spawned for more than one season but a 65‐mm female is estimated to spawn up to 3172 eggs over the extended spawning season. In the River Utsjoki in Finnish Lapland maturity was strongly size‐dependent and delayed until the fish reached 5, 6 or even 7 years of age, with a maximum age of 13 years at a length of only 75 mm. Unlike some other small‐sized species in unproductive environments, individual females continued to spawn successive clutches of eggs though over a much shorter spawning season. The maximum estimated egg production was 824 for a 65‐mm fish. Temperature had a strong direct or indirect effect on growth, with significantly lower growth increments in cold summers. At a second Arctic site in eastern Lapland growth rates were higher and maturity earlier, yet clutch size was greatly reduced with a seasonal fecundity estimate of only 314. There were only small differences in size of eggs or larvae between the populations. Evidence from other species indicates that most of the observed changes over the range of the minnow are phenotypic responses to the contrasting environments. However, the different strategies displayed at the two Arctic sites could represent the results of selection for differences in pre‐ and post‐reproductive survival.