*U.S. Dept Commerce/NOAA/NMFS/NWFSC/Publications*

----

**NOAA F/NWC-187 - Status and Future of Spring Chinook Salmon in the Columbia River Basin—Conservation and Enhancement**
**EVALUATION OF OUTMIGRATION PERFORMANCE AND SMOLT-TO-ADULTSURVIVAL OF SURYEARLING SPRING CHINOOK SALMON SMOLTS**
Richard W. Carmichael and Rhine T. Messmer

Oregon Department of Fish and WildlifeBadgley Hall, Eastern Oregon State CollegeLa Grande, Oregon 97504

The spring chinook salmon (
Oncorhynchus tshawytscha
) hatchery program in the Grande Ronde Basin is inadequate to provide adult returns capable of meeting broodstock, supplementation, and harvest objectives (Carmichael at al. 1986). There we not enough facilities in northeastern Oregon to expand yearling smolt production. Water sources suitable for siting new facilities are very limited because of severe winter conditions and summer flows and temperatures. To meet the long-term adult escapement goals, production of spring chinook smolts may be needed from well-water facilities such as Irrigon Hatchery. Well-water facilities generally have temperature regimes suitable for production of subyearling spring chinook smolts. There are obvious economic and hatchery production benefits associated with releases of subyearling smolts. For these reasons we began an evaluation of production and release of subyearling smolts. We chose Irrigon Hatchery as the incubation and rearing site because it theoretically has suitable water temperatures to produce a 23-g smolt for release in May of the first rearing year.

Our specific objectives were 1) to assess and compare outmigration performance of subyearling and yearling smolts and 2) to determine smolt-to-adult survival and benefits to hatcheries for subyearling smolts. Rapid River stock eggs were obtained from Idaho in 1986, 1987, and 1988. Eggs used for subyearling production were transported to Irrigon Hatchery for incubation and rearing. Eggs were incubated at a constant temperature of 11.20C. Replicate groups of approximately 40,000 were marked Ad+CWT and replicates of 20,000 were cold branded. In all 3 years, fish were transported to Lookingglass Hatchery the first week of May and were held for approximately 2 weeks before release. Mean length, mean weight, and visual index of smolting were determined just prior to release. Yearling smolts were produced at Lookingglass Hatchery under the standard production program and were marked and branded as described for the subyearling smolts.

Branded fish were recovered and enumerated at Lower Granite Dam as part of the Smolt Monitoring Program. Migration success was determined as the percentage of branded fish released that were estimated to have passed Lower Granite Dam. Migration success, duration, and rate were determined for both subyearling and yearling smolts. Yearling smolts were released only in 1988 and 1989 so no comparisons for 1987 releases could be made. In both 1988 and 1989, he yearling smolts were released 43 days earlier than the subyearling smolts. We used comparisons between yearling and subyearling smolts only as ma index of success because of the differences in release time and size.

We were unable to achieve the target release size of 23 g in 1987, 1988, or 1989. This was attributed to reduced growth in April that resulted from handling for marking and branding purposes (
Fig. 1
). Subyearling smolts were released in mid-May each year with a mean fork length range of 102-107 min and a mew. weight range of 12.5-15.0 g (
Table 1
). Yearling smolts were released earlier at a larger size in both 1988 and 1989 (
Table 1
). Migration success of yearling smolts was slightly better in 1988; however, in 1989, the migration success of subyearling smolts was over two times better than the yearling molts. We did observe differences in migration rate and duration between yearling and subyearling smolts. The length of time from release to migration completion was substantially longer for subyearling smolts and the migration rate of subyearling molts was slower (
Fig. 2
).
Table l. Release information for Rapid River stock subyearling and yearling spring chinook molts released from Lookingglass Hatchery. Standard deviation is presented in parentheses.
Age at release, brood yearsRelease dateMean fork length (mm)Mean weight (g)Yearling19861 April 1988125 (6.2)23.0 (4.6)19873 April 1989123 (9.2)22.4 (6.1)Subyearling198620 May 1987102(6.0)12.6(5.4)198713 May 1988107(6.2)15.0(3.0)198815 May 1989102(6.1)12.5 (2.3)

We observed significant shifts in the length frequency and mew, length of subyearling smolts from the time of release to time of recapture at Lower Granite Dam. (
Fig. 3
). This length shift was in part a result of growth; the length of many migrants recovered at Lower Granite Dam was greater than the length of the largest fish at release. Zaugg et al. (1986) reported significant mean-length shifts for 0-age spring chinook that were released from Little White Salmon Hatchery and recaptured in the Columbia River; however, the magnitude of change was much less than that which we observed.

The outmigration, performance of subyearling molts indicates good potential for success of this rearing-release strategy (
Fig. 4
). However, the true measure of success is survival to adulthood. Preliminary information regarding smolt-to-adult survival is not encouraging. One-ocean (age 2) and two-ocean. (age 3) adults from 1986-brood releases should have returned in 1988 and 1989, respectively. Them were no hatchery recoveries of any marked adults from subyearling smolt releases in either year. Lindsay at al. (1989) observed good outmigration success and poor smolt-to-adult survival for subyearling smolts released in the Deschutes River. We are unsure of what the adult age composition will be for subyearling smolt returns; however, if adults produced from 0-age smolts return at the normal total age, the majority of adults produced from the first releases in 1987 will return in 1990.
**References**
Carmichael, R. W., R. Boyce, and J. Johnson. 1986. Grande Ronde River spring chinook production report (US v. Oregon), 36 p. Oregon Department of Fish and Wildlife, P.O. Box 59, Portland, OR 97207.
Lindsay, R. B., B. C. Jonasson, R. K Schroeder, and B. C. Cates. 1989. Spring chinook salmon in the Deschutes River, Oregon. Oregon Department of Fish and Wildlife, Information Report 89-4:1.92. (Available from Oregon Department of Fish and Wildlife, P.O. Box 59, Portland, OR 97207.)
Zaugg, W. S., J. E. Bodle, J. E. Manning and E. Wold. 1986. Smolt transformation and seaward migration in 0-age progeny of adult spring chinook salmon (*Oncorhynchus tshawytscha*) matured early with photoperiod control. Can. J. Fish. Aquat. Sci. 43:885-888.
**QUESTIONS AND ANSWERS**
Q:
What were the weights after recapture at Lower Granite Dam, given the shift in the mean length?

A:
The mean was 20 g.

Q:
Given that them is spill at the dams in mid-April, it is likely that yon missed this for the May release; what is the success of subyearlings in passing the dam?

A:
There are some data for passage through the lower dams, but few at McNary Dam. Most subyearlings are probably barged from Lower Granite Dam. With the PIT tags it can be seen that some wild fish migrate late. The Grande Ronde wild fish are like the subyearlings, migrating in mid-May to late June.

Comment:
The wild fish from the Tucannon River us the same as the subyearling May release.

Q:
Did you record PIT tags at Lower Granite Dam? Did you get length/frequency data?

A:
Fish were tagged from trap boxes in the Grande Ronde and at Lookingglass Hatchery. These PIT-tagged fish were passively monitored at Lower Granite Dam, so there were no length data. But from two sources they are reported as 90-110 mm and 102 mm.

Q:
Regarding the 0-age fish from Little White Salmon River—do the adults return as falls or springs?

A:
It is typical that they return as springs.

Comment:
They also have a traditionally low harvest rate.

Q:
What about fishing pressures?

A:
The ocean catch is very little; also the in-river catch is small.

Q:
Since there is concern about genetic maintenance, are particular characters selected?

A:
We are not doing major selection for this group. If selection pressures are different from those in yearlings, we do not know what the effects would be. We do not believe that there would be genetic differences between the two.

Q:
What about looking at subyearling and yearling smolt indices in Idaho?

A:
This had been planned for the past year, but we could not get eggs from Idaho. We only had visual observations on smolting. Similar percentages appeared to be "smolty" between yearlings and subyearlings, which has also been noted in unsuccessful subyearlings and yearlings.

Q:
What has been done regarding size and age relationships?

A:
We have looked at gill Na
+
-K
+
 ATPase in yearlings and subyearlings. In subyearlings, although there
are not extensive indications of smoltification, there are some indications, and that is the essential factor. Smoltification develops more at release.

Q:
Regarding freeze-brand data, did differences in the quality of brands affect these data?

A:
This is possible, but we did have retention of marked groups and quality control, particularly in the yearling and subyearlings, since they were branded at different times.

Comment:
We don't know yet how to supplement with yearlings, let alone subyearlings.

Q:
Then is a lot of growth after release. Have you looked at outmigration timing between the time of release and time of recapture, particularly in regard to ecological competition with wild fish? This looks like it might happen also with the Leavenworth fish.

A:
No, we don't know the effects of this; it would be difficult to assess. One could look at food and spatial overlaps—it could be important.

Q:
Are you convinced that there is growth, or might only the bigger fish get to Lower Granite Dam?

A:
We believe that it is mostly growth, since we see larger fish than at release; it is not just migration success.

Comment:
We see no differences between mark quality and recovery. 0-age fish have most of their rearing in the mainstem. Regarding the summer and fail fish, there are not many of each at the same time. I would expect some competition with the resident non-salmonid fishes.

Q:
Why did you use Carson stock instead of a mid-Columbia stock?

A:
That was the only hatchery stock available.

Figure 1. Monthly growth and temperature profile for spring chinook subyearling smolts reared at Irrigon Hatchery, 1986-88 broods.
Figure 2. Comparison of migration timing and duration past Lower Granite Dam of yearling and subyearling spring chinook smolts released from Lookingglass Hatchery in 1988 and 1989.
img src="messfig3.jpg" width="500" height="1023" alt="Figure 3" />
Figure 3. Length frequency distribution (fork length) at release from Lookingglass Hatchery and at time of recapture at Lower Granite Dam for spring chinook subyearling smolts of the 1986, 1987, and 1988 broods.
Figure 4. Comparison of passage indices (% of release) at Lower Granite Dam between yearling and subyearling spring chinook smolts released from Lookingglass Hatchery in 1988 and 1989.
Table of Contents