17450

2002-031-00 PI SPRING CHINOOK GROWTH RATE MODULATION

6/1/2004

5/31/2006

157. Collect/Generate/Validate Field and Lab Data

Work Element Usage Report

E: 157 - Growth rate modulation experiment

E. The purpose of this WE (objective) is to conduct a second iteration of an experiment (in 1.4m diameter outdoor tanks) to examine the effect of growth rate modulation on the incidence of age 1+ precocious male maturation in Yakima hatchery spring Chinook. This experiment will test the following null hypothesis:
H0: Growth modulation has no effect on physiological development or incidence of precocious male maturation of supplementation hatchery spring Chinook.
In 2002-2003 we conducted and completed a growth rate modulation experiment in 1.4 m experimental circular tanks at the Cle Elum Supplementation and Research Facility aimed at reducing precocious male maturation rates in the Yakima spring Chinook stock. Results indicated that manipulating growth rate could alter the rate of precocious maturation. The highest growth group (High summer/High autumn growth) had 69% male maturity while the lowest growth group (Low summer/Low autumn growth) had 42% maturity. The maturity level of BY 2001 production fish sampled during pathology screening was approximately 60%. In other years the production fish have been as low as 40%. The Cle Elum facility is currently rearing 50% of its production fish under the normal rearing regime with a target weight of approximately 15 grams at tagging in mid-to late October and 50% of its production fish similar to the LL group with a size of approximately 10 grams by mid-October to try and reduce precocious maturity while maintaining a large enough fish to tag in October (see Objective 4).
Obviously, reducing the maturation rate by 40% in the production fish by rearing them smaller this year is a step in the right direction, but our goal is to determine if it is possible to rear Yakima spring Chinook to have a male precocity rate more in line with that of the wild fish (approximately 5-10%). A new modified growth modulation experiment for BY 2003 was initiated in 2004 as outlined below and will be completed in 2005:
BY 2003 Growth Modulation Experiment
Analysis of data from our BY 2001 experiment suggests that adjustment of pond timing (to an earlier date) and reduction in dietary lipid content may further reduce the level of precocious male maturation in the Yakima population. This will involve production of a low fat experimental diet for these fish at our research facility (our resident fish nutritionists have significant experience with formulation of experimental diets). Treatments would be developed to investigate the interaction between early and late (current) pond timing and dietary lipid content on precocious male maturation. Treatments will include fish ponded in early March on high (current commercial diet) and low fat diets and fish ponded in mid- April (current production time) on high and low fat diets in a 2x2 factorial design with 4 replicates per treatment. The treatments will all be grown to a comparable size of 10 grams (the programs minimal size for tagging) by October 15.
Throughout the experimental period fish from each treatment, wild fish captured by electroshock technique near the town of Cle Elum, and the representative production fish will be sacrificed to monitor physiology of the fish. We will measure the following parameters approximately monthly: weight, length, general smolt appearance, visual gonadal development, plasma insulin-like growth factor-I and whole body lipid (indicators of energetics and growth status). In June of 2005 the remaining fish (approximately 200/tank) will be sacrificed and visually assessed for gender and incidence of male maturation (among males) to determine the percent maturity in each of the four treatments.
5000 BY 2003 eggs were collected from broodstock throughout the adult run (50 eggs from multiple pairs). Approximately 300 randomly selected fish per tank in 16 tanks will be ponded. Half of the eggs are being incubated at elevated temperature (8 C) in a separate egg stack to induce ponding in early March rather than mid-April. The other half of the egg lot is being incubated with the production eggs at 5C. After ponding all fish will be fed commercial starter feed. After a few weeks experimental feeds will be used (4 tanks low fat, 4 tanks high fat). In April the same process will be repeated with the late emerging groups (4 tanks low fat, 4 tanks high fat). The four treatments are designated Early /High, Early /Low, Late /High, Late /Low. These fish will be reared throughout the early summer of 2005 and monitored monthly for physiological parameters including size, gender, growth regulating and reproductive hormones and gill Na+/K+-ATPase activity as a metric of smolt development. They will be compared with elecroshock collected wild and production hatchery spring Chinook.
Expectations: The expectations from this experiment are that fish ponded at the normal April ponding date and fed a high fat commercial diet will be most similar to the current small production fish and have precocious male maturation rates in excess of 40%. These same fish on a low fat diet may have lower rates of precocity. Previous work by Silverstein et al. (1998) has suggested that precocity can be modulated in spring Chinook by lowering dietary lipid levels. The fish ponded earlier may be able to obtain sufficient body size for tagging via a longer growth period but able to have slow autumn growth rate to prevent excessive precocious male development. Finally, the fourth treatment group includes both early pond timing and a low fat diet because this group most closely matches the growth and energetic stores of wild fish that have lower precocious maturation rates. Since this fourth group involves the most significant and expensive alterations in hatchery practice (altered incubation and feed quality) we believe it is important to explore the other less invasive hatchery alterations outlined above before changing protocols at the production scale.

Results from this experimetn will be used to further modify the programmatic decisions regarding growth of supplementation hatchery fish at the Yakima and other hatcheries throughtout the Columbia River basin and will be published in a peer reivewed journal.

$95,000

51.26%

06/01/2005

04/30/2006

06/18/2006

Concluded

n/a

n/a

Recurring