Effect of parental phenotype on dispersal, growth and maturation of offspring in wild masu salmon
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Feb 07, 2020 version files 38.27 KB
Abstract
- Offspring traits are influenced by complex interactions between parent phenotypes. However, ecological studies of these effects in animals living in their natural environment have tended to be more focussed on maternal than paternal influences.
- In this study, we investigated the effects of both parental phenotypes on offspring natal dispersal patterns, growth and early sexual maturity in masu salmon living in natural streams.
- We used wild-caught parental fish in a half-sib mating design that allowed comparison of offspring from males of two different life-history types (fast-growing precocious (sneaker) males that had spent their entire lives in only freshwater and slow-growing anadromous males that had migrated to the sea as juveniles and returned to fresh water to spawn at maturity). These males were mated with anadromous females and the eggs planted in natural streams in three years.
- Natal dispersal distance/direction depended on offspring sex and paternal life history: female offspring moved further downstream than males, whilst amongst males the offspring of precocious fathers tended to remain further upstream than those of anadromous sires. There was a maternal effect on offspring growth, with larger eggs resulting in larger offspring at least until these became precociously mature at the end of the first summer. However, while faster growing male offspring were more likely to become precociously mature and the incidence of male precocious maturity differed among families, there was no evidence that the threshold size for precocious maturation was influenced by whether the father had himself been precocious.
- We conclude that, although the dispersal of young salmon was significantly influenced by both paternal and maternal effects, their growth rate and divergence in life history types were mainly environmentally driven. The results suggest that in the natural environment, sex-specific dispersal patterns dependent on the life history of the sire can alter levels of competition faced by offspring, making it more difficult to detect other parental effects on offspring performance.