On the Mokelumne, we predict a mix of age 1 smolts and residents if freshwater survival is low to medium, all residents if freshwater survival is high, and all age 1 smolts if freshwater survival is size-dependent.
To summarize, it appears that American River fish can readily reach a size associated with high probability of surviving emigration as age 1 smolts (Fig. 8A).
If YOY cannot mature and spawn at age 1, we always predict age 1 smolts unless emigrant survival is low and freshwater survival is high, in which case we predict all fish mature and become freshwater residents.
The overall egg to hatchery 1+ smolt survival rate was estimated at 72.3% (9115 S1 smolts released/12 606 initial eyed eggs).
On this basis it was assumed that egg to smolt survival rates per group were identical in all groups and the number of ranched smolts per experimental group was therefore estimated by multiplying the number of initial (hatchery-retained) eyed eggs per group (Table 1) by the overall egg to S1 smolt survival rate (9115 S1 smolts ÷ 12 606 eggs = 0.723).
A total of 173 524 smolt and 221 981 fry were stocked in the Malbaie River from 1998 to 2002, whereas 243 fish caught at the dam originated from the hatchery and 493 were wild-born fish (Table 1).
But as the tugboat Umatilla made its way down the Snake the other day, pushing a barge loaded, by the government's count, with 254,317 smolts, corps biologists said they were still gathering data on whether barging contributed to a much higher rate of what they termed "delayed mortality" among salmon transported that way.
The short Bundorragha, only a mile and a half long before it empties into the sea, already had a small wild salmon run, and Mantle decided to supplement it with a hatchery, which releases 50,000 smolts each year, of which perhaps 1,500 return as adults after one or two years at sea.
The trial took place in 24 net pens (5×5×6 m), each with an adaptive feeding system and each pen receiving 800 , 70g, S1/2 smolts.
In addition, the facility described here was required to produce 480 000 smolts annually, to provide sufficient research fish in the institution.
In Abernathy Creek in southwest Washington, Kennedy et al. [49] similarly observed more F1 smolts than backcrosses and no steelhead backcrosses.
