Determinants of individual reproductive success in a natural pike (Esox lucius L.) population: a DNA-based parentage assignment approach

MSc thesis

Investigating the factors affecting variation in individual reproductive success is a key element for understanding selective pressures driving adaptation and evolution of fish. It is often assumed that larger, and hence older, individuals have higher relative reproductive fitness compared to small fish. This could result from the positive relationship between size and absolute fecundity and may be also facilitated by non-genetic age- and size-dependent parental effects on egg quality and offspring survival. However, detailed knowledge confirming these hypotheses is lacking for most fish populations in the wild. In the present study, the relative reproductive success (RRS) was estimated for an exhaustive sample of sexually mature male and female pike (Esox lucius L.) in a natural, unexploited population inhabiting a small lake in Brandenburg, Germany. In total, 215 viable offspring were sampled in summer and autumn 2008 and assigned by multilocus microsatellite genotype-based parentage assignment to 341 potential adults of the spawning population in spring 2008. It was found that 43.2 % of all sampled mature females and 21.5 % of all mature males recruited at least one viable young-of-the-year (YOY) to the population. The average (± SD) RRS was 1.0 ± 2.33 for male and 1.0 ± 1.45 for female pike. The spawning time extended from March, 25, to May, 01, 2008, as revealed by micostructure analysis of the YOY otoliths and there was a clear trend for large and old pike spawning earlier in the season than smaller fish. Relative reproductive success was not significantly related to size of either males or females, but there was a trend for larger males exhibiting higher RRS. There was no evidence for reproductive senescence for very old and large spawners. Interestingly, the RRS of females was positively related to fast early juvenile growth. Correspondingly, directional natural selection for fast juvenile growth was found in the present study, and there was also a non-significant trend for stabilizing selection on this trait. This finding suggest that female pike of either higher competitive ability or greater risk-taking behaviour during the juvenile period or those genetically predisposed for fast growth exhibit fitness advantages by showing superior reproductive success later in life. This study extends the already known selection for fast growth to increase chances of survival in this strongly cannibalistic species by a novel finding about the importance of fast early growth for reproductive fitness in pike. Therefore, any ecological or human-induced influence on growth of pike might have fitness consequences and may therefore also affect population dynamics.

Pagel, T. (2009). Determinants of individual reproductive success in a natural pike (Esox lucius L.) population: a DNA-based parentage assignment approach. Master Thesis, Humboldt-Universität zu Berlin / Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB) in Berlin


Published : 2009
Appeared in : Master Thesis, Humboldt-Universität zu Berlin / Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB) in Berlin