Monster Seminar JAM - The reproductive behavior and breeding success of hatchery and wild spring Chinook salmon spawning in an artificial stream
Dr. Steve Schroder, Washington Department of Fish and Wildlife
Hatcheries have the potential to be important agents of salmonid conservation because of their capacity to enhance survival during incubation and freshwater rearing. Artificial culture, however, is known to affect age at maturity, morphology, physiology, and behavior in salmonids. A key question is will such changes deleteriously impact hatchery fish when they reproduce under natural conditions. We compared the reproductive behavior and breeding success of hatchery and wild spring Chinook salmon spawning in an artificial stream. Hatchery and wild females had comparable egg retention rates and no differences were seen in their spawning ground longevity, in-stream distribution patterns, digging behavior and redd tenure. Yet, egg-to-fry survival rates in wild females were 6% higher than those achieved by hatchery fish. Subtle inequalities in redd abandonment, choice of redd locations, and egg burial efficiency appear to be responsible. The effects of body weight, spawning ground longevity, agonism, courting frequency, and mate number on breeding success in four and five-yr-old hatchery and wild males were evaluated. Neither hatchery nor wild males exhibited a preference for females based on their origin. Wild males had higher attack rates and greater social dominance than hatchery fish. These disparities occurred because wild males were typically 9% larger than hatchery males. Despite observed differences in agonism and social status, DNA-based pedigree analyses showed that four and five yr-old hatchery and wild males had comparable breeding success values. We also examined the effect of age at maturity on male breeding success. On average, four and five yr-old anadromous males produced 89%, jacks (three-yr-old anadromous males) 3.2%, yearling precocious 7.4%, and sub-yearling precocious males 0.8% of the fry that were sampled from seven separate test groups. These percentages remained stable even though the proportion of four and five year-old males ranged from 48% to 87.5% and tertiary sex ratios varied from 1.4 to 2.4 males per female. Consequently, in our experimental setting a single generation of hatchery exposure had a low impact on the reproductive behavior and breeding success of spring Chinook salmon.
Date and Time:
June 3, 2010,
11:00 am - 12:00 pm