Barry A. Berejikian

Evidence for morphometric differentiation of wild and captively reared adult coho salmon : a geometric analysis

As part of a comprehensive genetic evaluation of reproduction in naturally spawning coho salmon, Oncorhynchus kisutch, we examined morphometric variation in captively reared and wild adults from Hood Canal, Washington (U.S.A.) for evidence of differentiation between these groups. We collected captively reared fish as parr from two stocks and reared to adulthood at a freshwater hatchery, maturing in 1995 and 1996; we sampled closely size-matched wild fish as they returned to a neighboring stream in both years. Multivariate analysis of shape variation by Procrustes coordinates, visualized by thin-plate splines, indicated that the captively reared adults were differentiated from the wild fish by sharply reduced sexual dimorphism as well as smaller heads and less hooked snouts, increased trunk depth, larger caudal peduncles, shorter dorsal fins, larger hindbodies and a reduction in body streamlining. The differences between the captively reared and wild fish were similar to but more pronounced than some differences previously reported between hatchery and wild coho salmon. The magnitude and pattern of differences suggested that at least some of them were environmentally induced. Shape variation showed an allometric relationship with variation in body (measured as centroid) size. Morphometric variation was a poor correlate of most spawning behaviors. Nevertheless, our results suggest that the morphometric consequences of captive rearing for mate selection and reproductive activity of spawning fish may limit its effectiveness as a restorative tool.

Reproductive behavioral interactions between wild and captively reared coho salmon (Oncorhynchus kisutch)

Captive rearing is an evolving strategy for restoring depleted salmon populations; it involves capturing wild juvenile salmon from natural streams, rearing them in captivity to adulthood, and then releasing them as adults back into their natal streams to spawn naturally. The conservation benefit of captive rearing is that it bypasses the typically high smolt-to-adult mortality experienced by wild populations, but its success as a restoration strategy depends upon the ability of captively reared salmon to spawn and reproduce in natural streams. In an experimental channel, wild males dominated captively reared males of similar size in 86% of spawning events. Both wild and captively reared females attacked captively reared males more frequently than wild males, indicating a preference for wild over captively reared males, although the interplay between male dominance and female mate choice was unclear. Wild females established nesting territories earlier and constructed more nests per individual than captively reared females of similar size, suggesting a competitive advantage for wild females. Nevertheless, captively reared coho salmon demonstrated the full range of behaviors shown by wild coho salmon of both sexes and the ability to spawn naturally.

Competitive Differences between Newly Emerged Offspring of Captive-Reared and Wild Coho Salmon

Abstract We investigated competition among newly emerged fry from captive-reared and wild female coho salmon Oncorhynchus kisutch by conducting dominance challenges and growth and survival experiments in laboratory stream channels. Newly emerged fry from captive-reared females won a significant majority (72.7%) of dyadic dominance challenges against fry from wild females. In a growth and survival experiment conducted from emergence to 30 d postemergence, fewer captive brood fry died of apparent starvation when food was limited than wild fry, further suggesting a competitive advantage for the captive brood fry. All fry used in the study were paternal half-sibs, so observed differences between captive brood and wild fry were attributed to the maternal parent. We hypothesize that fry coloration resulting from differences in egg color between wild and captive-reared females may have influenced the observed competitive asymmetries. If so, such differences might be ameliorated by changes in husbandry practices ...

Reproductive Behavior and Breeding Success of Captively Reared Chinook Salmon

Abstract Release of captively reared adults is one of several strategies currently being used to maintain imperiled populations of chinook salmon Oncorhynchus tshawytscha in the Pacific Northwest. This study evaluated the breeding behavior and success of captively reared chinook salmon released at maturity into a controlled-flow stream channel. Female egg deposition was 49.5%, which is much lower than that reported for wild populations, but egg-to-fry survival was 62.5%. Females abandoned 40% of the nests they constructed, and males were often absent during the females nest construction. The underlying causes of these presumed behavioral deficiencies might have limited the breeding success of the population. The efficacy of adult release strategies should be assessed within the context of other potential release options, keeping in mind the objectives of the individual program. Under current culture practices, the reproductive success of captively reared chinook salmon that are released as adults may be ...

Breeding Structure of Steelhead Inferred from Patterns of Genetic Relatedness among Nests

Abstract Ten polymorphic microsatellite loci were used to infer kinship among steelhead Oncorhynchus mykiss sampled from nest sites in the Hamma Hamma River, Washington. Fertilized eggs were removed from 8 of 11 redds (i.e., individual nests within redds) surveyed in 1998, tagged with unique identifiers, and reared until adulthood as part of a conservation program. On average, individuals sampled from the same redd were more closely related than individuals sampled from different redds, and a tree generated from the pairwise relatedness estimates shows clear clustering of individuals by redd. Despite this general pattern, there was substantial overlap in the pairwise relatedness estimates within and among most redds. Of the eight redds, seven contained more than four alleles at a minimum of one locus and five contained more than six alleles, indicating that most redds were the result of matings by more than a single pair of parents. In total, the eight redds were created by a minimum of 21 parents, which ...

Development of natural growth regimes for hatchery-reared steelhead to reduce residualism, fitness loss, and negative ecological interactions

Wild steelhead (Oncorhynchus mykiss) typically spend two or more years in freshwater before migrating to sea, but hatchery steelhead are almost ubiquitously released as yearlings. Their large size at release coupled with life history pathways that include both male and female maturation in freshwater present ecological risks different from those posed by hatchery populations of Pacific salmon. Yearling hatchery reared steelhead that fail to attain minimum thresholds for smoltification or exceed thresholds for male maturation tend to ‘residualize’ (i.e., remain in freshwater). Residuals pose ecological risks including size-biased interference competition and predation on juvenile salmon and trout. Three hatchery populations of steelhead in Hood Canal, WA were reared under growth regimes designed to produce a more natural age at smoltification (age-2) to aid in rebuilding their respective natural populations. Mean smolt sizes and size variability at age-2 were within the range of wild smolts for two of the three populations. The third population reared at a different facility under similar temperatures exhibited high growth rate variability and high male maturation rates (20% of all released fish). Experimentally comparing age-1 and age-2 smolt programs will help identify optimal rearing strategies to reduce the genetic risk of domestication selection and reduce residualism rates and associated negative ecological effects on natural populations. Investigations of Winthrop National Fish Hatchery summer-run steelhead will measure a) selection on correlated behavioral traits (‘behavioral syndromes’), b) degree of smoltification, c) changes in hormones that regulate gonad growth at key developmental stages, and d) conduct extensive post-release monitoring of fish reared under each growth regime.

Evaluation of a New Coded Electromyogram Transmitter for Studying Swimming Behavior and Energetics in Fish

Abstract A new coded electromyogram (CEMG) transmitter was recently introduced to the market to allow broader application and greater flexibility of configurations than the conventional noncoded version. CEMG transmitters were implanted into 20 steelhead Oncorhynchus mykiss and calibrated to swimming speed in a respirometer to determine the relationship between swimming speed and the output of the transmitters and also to determine how the output of a single transmitter varied when implanted in multiple fish. Linear regression models showed a strong positive relationship between the output from CEMG transmitters and swimming speed. However, grouping signals from multiple transmitters produced a less accurate relationship between CEMG output and swimming speed than using signals from individual transmitters. The results, therefore, do not suggest that the CEMG transmitters acted similarly in all fish. Calibration data from one transmitter were not readily transferable among multiple fish implanted with the...

Spawning by Female Chinook Salmon Can Be Detected by Electromyogram Telemetry

Abstract New methods to detect spawning of anadromous salmonids in their natural environment are needed to improve understanding of breeding behavior patterns, natural selection on reproductive traits (e.g., spawn timing), and interactions between artificially propagated and wild fish. We implanted maturing female Chinook salmon Oncorhynchus tshawytscha with coded electromyogram (CEMG) transmitters and continuously recorded spawning activity to develop an algorithm capable of accurately detecting spawning events from CEMG data. Marked increases in female digging frequencies immediately after spawning (cover digging) strongly correlated with CEMG values. The algorithm detected averages of 65% and 86% of the actual spawning events in 2003 and 2004, respectively. The algorithm accurately detected zero spawning events for the two female salmon that did not spawn. The presence of CEMG transmitters did not affect the digging frequency, number of nests constructed, or the reproductive life span of implanted fish...

The Effects of Exercise on Behavior and Reproductive Success of Captively Reared Steelhead

Abstract Steelhead Oncorhynchus mykiss collected as eyed eggs from the Hamma Hamma River, Washington, and reared in high (∼1 body length/s) or low current velocity (∼0.25 body lengths/s) were tested for differences in reproductive behavior in both an experimental spawning channel and their natal river. We conducted continuous (24-h/d) behavioral observations in the spawning channel and applied DNA pedigree analyses to explain the variation in individual reproductive success. Female steelhead reared in high and low current velocities did not exhibit differences in reproductive behavior in the spawning channel, but females reared in low current velocity were more frequently observed constructing nests in the Hamma Hamma River. Males reared in low-velocity tanks were more frequently observed courting females in the spawning channel and in the river. A pedigree analysis revealed no significant differences in reproductive success between the rearing treatments. Male reproductive success in the spawning channel...

Male size effects on fertilization success: lack of evidence in chinook salmon spawning under experimental conditions

SynopsisAnadromous salmonid females exhibit indicators of mate choice based on male size. Direct benefits to females of mating with larger males have not been identified for semelparous Pacific salmon, Oncorhynchus spp. We tested the null hypothesis that females forced to spawn naturally in a stream channel and artificially (gametes removed manually) with males about half their body mass would experience egg fertilization rates similar to that of females forced to spawn with males of about equal mass. Fertilization rates did not differ significantly between large- and small-male pairs. The fertilization rates were also very similar for eggs deposited naturally and those that we fertilized artificially. Therefore, fertilization success does not appear to be the mechanism responsible for female mate choice based on male size. Benefits of females mating with larger males probably have only indirect (i.e., genetic) benefits to a female’s offspring, as suggested by previous authors.