title: Do stocked hatchery-reared juveniles ecologically suppress wild juveniles in Salvelinus leucomaenis?
abstract: The dominancy of semi-wild and hatchery-reared white-spotted charr Salvelinus leucomaenis juveniles was evaluated using pair-wise enclosure tests and field stocking tests. The semi-wild S. leucomaenis originated in a hatchery, being stocked into the test stream as eyed-eggs. In the pair-wise enclosure test, the semi-wild S. leucomaenis dominated the hatchery S. leucomaenis that were of a similar standard length (L(S) ). The semi-wild S. leucomaenis were subordinate to hatchery S. leucomaenis that were > 11% larger in LS . In the field stocking test, the abundance and growth of semi-wild S. leucomaenis was decreased in the presence of larger hatchery S. leucomaenis (14% larger LS ). Taken together, these results suggest that larger hatchery S. leucomaenis ecologically suppress the smaller semi-wild S. leucomaenis. Salvelinus leucomaenis juveniles that are stocked with the intention of supplementing natural populations should be < 10% larger than their wild counterparts at the time of stocking to minimize their competitive advantage. The semi-wild and hatchery S. leucomaenis used in both tests were genetically similar individuals, suggesting that the differences are due to the early rearing environment of either a natural stream or hatchery. The hatchery S. leucomaenis have lower levels of aggression as a result of selection in the hatchery rearing environment. Rearing in a natural stream from the eyed-egg stage is likely to increase their lowered aggression.
authors.affiliation: National Research Institute of Aquaculture, Fisheries Research Agency, 2482-3, Chugushi, Nikko, Tochigi, 321-1661, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakamura
authors.forename: T
authors.initials: T
authors.lastname: Doi
mesh_terms: D000374:Aggression; D000818:Animals; D017756:Aquaculture; D001522:Behavior, Animal; D049628:Body Size; D004291:Dominance-Subordination; D004777:Environment; D005398:Fisheries; D014337:Trout / Q000502:physiology*
keywords: competition; enhancement; interaction; stocking; white-spotted charr