Early Growth and Quality of Chum Salmon (Oncorhynchus keta) Produced in Keeper Channels and Gravel Incubators

Publisher Website
Google Scholar
Abstract
Chum larvae were incubated in 2 types of incubation system-a pilot Japanese-style hatchery (JSH) and a set of deep-gravel incubators (box)-at 2 levels of flow, and 2 or 3 levels of egg density. Following voluntary emergence, fish were reared in tanks on an OMP [Oregon Moist Pellets] diet and their growth rates compared. Initially, fry from both systems were of the same average size, but the JSH fish emerged 6 days earlier than the box fish and at a stage of development 6 days less advanced. At the end of 8 wk, all JSH groups were significantly longer than the box groups; the most extreme groups averaged 63.4 and 59.2 mm, respectively. Not only the JSH fish kept their 6-day lead in additional growth, but they also grew significantly faster (calculated average rates were 3.553 and 3.217 mm/wk in the above groups). A previous assessment of fry quality had rated the JSH fry inferior to the box fry on the basis of 4 criteria (efficiency of yolk conversion, size and stage of development at emergence, and time of emergence). In this test, JSH fry rated superior in terms of final size and rate of growth achieved during 8 wk following emergence. Difficulties with simplistic quality criteria and how such criteria relate to fitness are discussed.