Comparing spawning time and egg quality of trout in cold creek water vs warmer spring water

Lower temperatures mean slower development, but temperatures below 4.5ºC/40ºF have detrimental effects on development while temperatures below 13ºC/55.5ºF reduce the percentage of "eyed" (the beginnings of eye development can be seen) salmon.

This experiment is to determine if placing brood-stock (separated males and females) in cold water will effect egg quality vs those in warmer water.

250, 3 year old, Winthrop strain rainbow trout were held in two outdoor raceways measuring 1.8m x 18m x 0.6m (6ft x 60ft x 2ft). All trout(s) had been raised in spring water and both raceways were initially filled with spring water. In September, one raceway had creek water introduced while the other remained at 10ºC/50ºF. Water inflow was about 570L/m (150gal/min). There were weekly checks in December and artificially spawned. (The first batch of eggs was discarded due to believed error in the artificial spawning process.) On each spawning day, 9 to 18 females were spawned separately and fertilized with sperm from separate males. If additional females were spawned, eggs from 3 fish were pooled and fertilized with sperm from two males. Water for the eggs was supplied at about 19L/m (5gal/m). Formulin fungus control was applied for 15 minutes daily in a 1:600 concentration. When the eggs eyed, they were counted and the dead eggs were removed.

Table:   Spring water at 10ºC (50ºF) versus Bridger Creek at (ranging from 2ºC (35ºF) to 14ºC (57ºF))

Water       Weight            Fecundity           Weight     Eyed
Source        of        ------------------------  per 1000   Eggs
           Female(kg)   Eggs per      Eggs per     (g)a      (%)
                         female       kg/female
--------------------------------------------------------------------
Spring       1.99b        2992          1527        75        86
Creek        1.75         3094          1793a       72        86

Key:
a = Data for all fished, pooled.
b = Value significantly higher (P < 0.05) than the other value in the same column.

Fish in spring water were spawned from December 12th, 1977 to February 9th, 1978. Fish in creek water were spawned from March 29th, 1978 to April 20th, 1978. (When fish in creek water were ready to spawn, the water temperature was about 7ºC (45ºF) and rising rapidly. The water then became heavily silted was was replaced by spring water.

A total of 39 females were spawned from creek water, and 6 females from spring water. Fish in creek water were significantly smaller than those in sprint water due to a slower metabolism and less food intake. The weight of the gross number of eggs between both groups was about the same; there were more creek salmon eggs, but they were of lower weight.

Conclusion:
Winthrop strains (and maybe other winter/fall strains) can be held in cold water to delay spawning with no noticeable effect in egg quality. Also, domestic fish strains that spawn in early winter can spawn during the usual spring times when released into the wild.