Conservation Hatchery Research Articles

Stress Responses in Pallid Sturgeon Following Three Simulated Hatchery Stressors

AbstractBecause sturgeon populations are in critical decline, many species are artificially propagated in hatcheries with the goal of increasing wild stocks. Capture, transport, handling, confinement, and environmental fluctuations are just a few of the possible stressors Pallid Sturgeon Scaphirhynchus albus can be exposed to in conservation hatcheries. The objectives of the present study were to elucidate the effects of acute exposure to high ammonia concentrations, low dissolved oxygen (DO) concentrations, and crowding on stress responses in Pallid Sturgeon, quantified by changes in plasma cortisol and glucose. Exposure to un‐ionized ammonia‐nitrogen concentrations of 0.6 mg/L for 24 h resulted in no significant (P > 0.05) change in plasma cortisol concentrations, suggesting these fish do not perceive the buildup of toxins. Exposure to 2 mg/L DO over a 0.5‐h period resulted in a significant (P < 0.05) increase in plasma cortisol concentrations during the low DO challenge, with levels decreasing (P > 0.05) within 30 min of recovery and returning to prestress levels within 2.5 h of recovery. Plasma cortisol concentrations increased (P < 0.05) within 0.25 h of crowding and remained elevated after 0.5 h of crowding. Removal of the crowding stressor did not result (P > 0.05) in decreased circulating cortisol within 30 min. Regardless of the stressor, Pallid Sturgeon plasma glucose levels were unaffected (P > 0.05). As such, glucose does not appear to be a reliable indicator of stress in Pallid Sturgeon. Defining the effects of stress on Pallid Sturgeon physiology is a critical first step toward understanding how stress affects fish health and well being and optimization of propagation practices.

Survival and Growth of Lake Sturgeon during Early Life Stages as a Function of Rearing Environment

AbstractThe need for hatchery programs to reflect the latest scientific knowledge is critical for understudied groups with unique ecologies such as Acipenseriform species, including Lake Sturgeon Acipenser fulvescens. In order to address uncertainties regarding the efficacy of Lake Sturgeon culture techniques, we quantified and compared growth and survival at the egg, larval, and juvenile life history stages as a function of hatchery rearing environment over 2 years (two cohorts). Furthermore, we evaluated growth and survival of juveniles produced from three methods of progeny collection including direct gamete takes, collection of naturally spawned eggs from the stream substrate, and collection of larvae dispersing downstream from the spawning grounds. Progeny from each collection method were evenly divided between a streamside hatchery on the natal river and a traditional hatchery. Progeny reared at the streamside hatchery experienced a natural temperature regime and were exposed to natal water only filtered to remove larger sediments. We found that daily survival at the egg stage varied as a function of hatchery environment, duration of incubation, and maternal sources. Microbial infection during incubation contributed significantly to mortality, was higher, and occurred earlier in the incubation period at the streamside hatchery than at the traditional hatchery. Hatching rate was significantly higher at the streamside hatchery in 2006 than at the traditional hatchery. Daily survival at the larval stage was high at both hatcheries but was significantly higher at the streamside hatchery in 2006. Importantly, survival of progeny collected as dispersing larvae was significantly lower during the first week of rearing in both hatchery environments and years. Growth rates at the juvenile stage were comparable between hatcheries and inter‐individual variation in growth increased through the rearing period in both years. Natural temperature regimes resulted in variable egg incubation time and concomitant variation in larval size at hatch that extended into the juvenile stage. Results indicate conservation hatchery programs that incorporate rearing environments reflective of natural conditions can increase phenotypic variation in stocked progeny without compromising survival in the hatchery.

Variation in the Early Marine Survival and Behavior of Natural and Hatchery-Reared Hood Canal Steelhead

BackgroundHatchery-induced selection and direct effects of the culture environment can both cause captively bred fish populations to survive at low rates and behave unnaturally in the wild. New approaches to fish rearing in conservation hatcheries seek to reduce hatchery-induced selection, maintain genetic resources, and improve the survival of released fish.Methodology/Principal FindingsThis study used acoustic telemetry to compare three years of early marine survival estimates for two wild steelhead populations to survival of two populations raised at two different conservation hatcheries located within the Hood Canal watershed. Steelhead smolts from one conservation hatchery survived with probabilities similar to the two wild populations (freshwater: 95.8–96.9%, early marine: 10.0–15.9%), while smolts from the other conservation hatchery exhibited reduced freshwater and early marine survival (freshwater: 50.2–58.7%, early marine: 2.6–5.1%). Freshwater and marine travel rates did not differ significantly between wild and hatchery individuals from the same stock, though hatchery smolts did display reduced migration ranges within Hood Canal. Between-hatchery differences in rearing density and vessel geometry likely affected survival and behavior after release and contributed to greater variation between hatcheries than between wild populations.Conclusions/SignificanceOur results suggest that hatchery-reared smolts can achieve early marine survival rates similar to wild smolt survival rates, and that migration performance of hatchery-reared steelhead can vary substantially depending on the environmental conditions and practices employed during captivity.

Evaluating the Performance of Captive Breeding Techniques for Conservation Hatcheries: A Case Study of the Delta Smelt Captive Breeding Program

The delta smelt, an endangered fish species endemic to the San Francisco Bay-Delta, California, United States, was recently brought into captivity for species preservation. This study retrospectively evaluates the implementation of a genetic management plan for the captive delta smelt population. The captive genetic management plan entails tagging fish, molecular data collection, pedigree reconstruction, relatedness estimation, and recommending fish crosses annually in an effort to minimize the average coancestry in the population and limit inbreeding. We employed 12 microsatellite DNA markers to examine temporal genetic diversity in consecutive, discrete generations to determine the effects of intensive genetic management on the population and to quantify the amount of wild genetic diversity present within each captive generation. Wild fish are incorporated into the captive population each generation to minimize genetic drift, and 91% of the original founders are still represented in the F(3) generation. The average mean kinship in the third generation in captivity was 0.0035. There was no evidence of significant genetic divergence of the captive population from the wild population. The results of this study yield management insights into the practical application of genetic management plans for captive populations and conservation hatcheries, in an attempt to preserve the genetic integrity of endangered species.

Effectiveness and Trade‐Offs Associated with Hydraulic Egg Collections from Natural Salmon and Steelhead Redds for Conservation Hatchery Programs

AbstractMaintaining a large genetically effective number of breeders (Nb) in supplemented salmon populations is considered vital to their long‐term sustainability, yet may be difficult to consistently achieve in practice, especially in conservation hatchery programs that require small numbers of eggs for captive rearing. We evaluated efforts to hydraulically collect eggs from naturally produced redds, as implemented by conservation hatchery programs for Endangered Species Act listed populations of Snake River Chinook salmon Oncorhynchus tshawytscha and Hood Canal steelhead O. mykiss; we then compared the estimated Nb represented in the hydraulically collected captive populations with the Nb obtained by the more conventional approach (i.e., adult collection and artificial spawning). Egg collection goals in the steelhead and Chinook salmon conservation hatchery programs were met in most cases and were never exceeded. The embryo viability and egg‐to‐fry survival consistently exceeded 90% and were no less than would be expected through artificial spawning. Demographic estimates suggested that a greater Nb in the captive population would be obtained by hydraulic redd sampling than by artificial spawning of captured adults to produce a specific, limited number of eggs. Hydraulic redd sampling allows sexual selection to occur naturally on the spawning grounds and does not require barrier weirs, handling of adults, or the removal of a female's entire fecundity from natural production. The high rate of survival to emergence for hydraulically collected eggs (>95%) suggests that eggs are not damaged by the collection process, but the fate of uncollected eggs that are disturbed during the process is unknown. Hydraulic redd sampling requires fairly frequent redd surveys to time collections at the proper stage of embryonic development, and access to some redds in remote areas can be difficult. Hydraulic sampling of eyed eggs appears to have largely accomplished the goals of these small‐ to moderately‐sized conservation hatchery programs.

The effect of a supplementation program on the genetic and life history characteristics of an Oncorhynchus mykiss population

Conservation hatcheries, which supplement natural populations by removing adults or embryos from the natural environment and rearing and releasing parr, smolts, or adults back into their natal or ancestral streams, are increasingly being used to avoid extinction of localized populations of Pacific salmonids. We collected data before and during a steelhead ( Oncorhynchus mykiss ) supplementation program to investigate the effect that the program has had on the population’s genetic diversity and effective population size and any changes to an important life history trait (residency or anadromy). We found that supplementation did not cause substantial changes in the genetic diversity or effective size of the population, most likely because a large proportion of all of the steelhead redds in the river each year were sampled to create the supplementation broodstock. Our data also showed that the captively reared fish released as adults successfully produced parr. Furthermore, we found that during supplementation, there was an increase in the proportion of O. mykiss with anadromous ancestry vs. resident ancestry.

Ecotype Distinctions among Steelhead in Hood River, Oregon, Allow Real‐Time Genetic Assignment of Conservation Broodstocks

AbstractEfforts to rehabilitate threatened summer‐run (SR) and winter‐run (WR) populations of steelhead Oncorhynchus mykiss in the Hood River, Oregon, include operation of two conservation hatchery programs. Annual collection of discrete broodstocks relies on identification of SR and WR fish based on return time, reproductive state, and other physical and behavioral characteristics. An increased likelihood of misidentification occurs in the spring, when SR and WR return times overlap. The resulting interbreeding between ecotypes in the hatchery imposes serious genetic risks to wild SR and WR steelhead populations. We characterized life history differences between Hood River SR and WR steelhead and evaluated genetic structure using a suite of microsatellite loci. Significant differences in life history, including age at return and fork length, were corroborated by spatially influenced genetic structure among SR and WR fish; SR fish spawn in the west fork of the Hood River, while WR fish spawn in the east and middle forks. Temporal and spatial distinctions persist among Hood River steelhead ecotypes despite past operation of segregated hatchery programs utilizing out‐of‐basin stocks. We evaluated the feasibility of using real‐time genetic assignment tests to differentiate SR from WR among candidate broodstock fish captured downstream of spawning grounds. Among adult steelhead of known origin, we observed 91.5% assignment accuracy for WR fish and 77.7% accuracy for SR fish. A rapid‐response protocol was subsequently developed that provides hatchery managers with genetic assignment of broodstock to ecotypes within 24 h after interrogation of returning fish.

Genetic Evaluation of a Conservation Hatchery Program for Reintroduction of Sicklefin Redhorse Moxostoma sp. in the Tuckasegee River, North Carolina

AbstractRestoration and reintroduction efforts for the sicklefin redhorse Moxostoma sp. have been initiated by state, tribal, and federal agencies owing to the limited geographic distribution of this species and threats associated with the physical alteration of its habitat. A critical component of a successful reintroduction is that the source and recipient populations have similar genetic resources and life history patterns. We used 10 microsatellite loci to estimate and compare indices of genetic diversity between the Little Tennessee River population of wild adults and the hatchery broodstock being used for initial reintroduction efforts. We also compared relatedness values for the broodstock used for restoration efforts. There were no significant differences between hatchery broodstock and wild adults with respect to average gene diversity, but the average number of alleles for each brood year was significantly less than that for wild adults. While this trend persisted when the 2007 and 2008 brood years (combined) were compared with wild adults, the reduction was not significant. Finally, all hatchery crosses were among unrelated individuals. Our results highlight the importance of using genetic information to assist restoration and reintroduction efforts.

Macro- and microparasite infection profiles of hatchery fish before and after release from a conservation hatchery (steelhead trout, Oncorhynchus mykiss)

Conservation hatcheries are becoming a tool in rebuilding salmonid populations, but their contributions are strongly debated. Most studies focus on genetic, morphological, and behavioural, issues and less is known of the importance of infectious agents. The Living Gene Bank (LGB) program of the British Columbia Ministry of the Environment is a recent effort to restore collapsed steelhead trout (Oncorhynchus mykiss) populations on the east coast of Vancouver Island. Our study describes the change in macro- and microparasitic profiles of LGB-hatchery-produced juveniles after they leave the hatchery and enter the natural river environment and also compares them with a limited wild smolt sample. We found that the hatchery was successful in raising parr free of infectious agents, but once introduced into the river environment, the hatchery fish quickly took on a diverse profile of infectious agents. The high numbers of fish released from the hatchery and the existence of hatchery fish that stay in the river as residents increased the number of fish in the system with sub-clinical levels of infection. An ecological understanding of the role resident hatchery fish play in the spatial distribution of infectious agents as well as the temporal and seasonal variations in infectious agent prevalence and diversity will be important in determining the net effect of the LGB conservation hatchery on the wild population.

Induced Spawning, Artificial Fertilization, and Egg Incubation Techniques for Green Sturgeon

AbstractEstablishment of hatchery breeding techniques for the threatened green sturgeonAcipenser medirostrisis important for research and conservation hatcheries. Injections of either gonadotropin‐releasing hormone analog (GnRHa) or GnRHa plus domperidone were used to induce ovulation in 13 female Klamath River green sturgeon and to induce spermiation in 19 males. Ovulated eggs were either rinsed in water or not rinsed before fertilization, and the eggs were fertilized with different milt dilutions and for different lengths of time. After fertilization, eggs either were allowed to adhere to the bottom of glass dishes or were silted for 1 h and then incubated in McDonald or upwelling jars. All broodfish ovulated or spermiated in all hormonal treatments, and the best treatment was GnRHa injected alone in a single dose of 10 μg/kg for males or in a 1‐μg/kg priming dose and a 19‐μg/kg resolving dose for females. Females were held at 12–13°C, and ovulation was observed 14 ± 3 h (mean ± SD) after the second injection. Domperidone was not required for successful ovulation and appeared to reduce the adhesion of ovulated eggs. From 49,000 to 115,000 eggs were collected from each female, and from 30 to 300 mL of milt were collected from each male. Sperm cell concentrations in milt ranged from 2.9 × 108to 5.4 × 109sperm/mL, and the sperm exhibited 90–100% motility for up to 5 min. In all experiments, egg rinsing improved fertilization success by 5–12%. Embryo survival to neurulation in the McDonald jars was lower (5–32%) than that in the upwelling incubators (60–82%). Green sturgeon eggs were sensitive to the high‐impact rolling action at the bottom of the McDonald jars, probably due to the large egg diameter (mean ± SD = 4.33 ± 0.14 mm) and thinner chorion (42 ± 4 μm) relative to eggs of white sturgeonA. transmontanus(diameter = 3.79 ± 0.03 mm; chorion thickness = 115 ± 6 μm).

Comparison of Female Reproductive Traits and Progeny of First‐Generation Hatchery and Wild Upper Yakima River Spring Chinook Salmon

AbstractHatchery and wild female spring Chinook salmon Oncorhynchus tshawytscha from the upper Yakima River were compared to determine whether their reproductive traits had diverged after a single generation of artificial propagation. Fecundity, relative fecundity, individual egg mass, and total gamete mass were all significantly correlated with body length, while reproductive effort (gonadosomatic index) was not. Regressions of trait versus body length often differed significantly among brood years. Hatchery spring Chinook salmon were significantly smaller than wild females over the four brood years examined. After brood year and body length (when necessary) were accounted for, wild females had an average of 8.8% more total gamete mass, 0.8% more individual egg mass, 7.7% greater fecundity, and 0.8% greater reproductive effort than hatchery females. Relative fecundity (the number of eggs per centimeter of body length) was on average 1.3% greater in hatchery females. We also compared body size at yolk absorption and egg‐to‐fry survival of the progeny from hatchery‐by‐hatchery and wild‐by‐wild matings. After differences in egg size were accounted for, hatchery fry were on average 1.0% heavier than wild fry. Egg‐to‐fry survival rates varied among years, with no consistent difference between hatchery and wild fry. The relationships between reproductive traits and body length were not significantly altered by a single generation of hatchery exposure. However, because hatchery females had smaller body sizes, the distributions of linked traits, such as total gamete mass and fecundity, differed by as much as 0.6 SD, probably resulting in some fitness loss. Our data support the idea that a single generation of state‐of‐the‐art conservation hatchery propagation can produce fish with reproductive traits similar to those of wild fish, given comparable body size.

Effects of the rearing environment on average behaviour and behavioural variation in steelhead

In the context of conservation hatcheries that seek to bolster wild populations by releasing captively‐reared fishes into the wild, steelhead Oncorhynchus mykiss were used to test the hypothesis that naturalistic rearing environments promote adaptive behaviour that might otherwise not develop in typical hatchery environments. When comparisons were made among fish reared in barren, structured or structurally variable environments (i.e. the location of the structure was repositioned every 2–3 days), structure in the rearing environment increased future exploratory behaviour, but only if the structure was stable. Under conditions of high perceived predation risk, the fish no longer exhibited increased exploratory behaviour, suggesting that it is expressed in an adaptive, context‐dependant manner. Another concern with hatcheries is that relaxed selection over multiple generations in captivity can increase maladaptive behavioural variation. Compared to rearing in hatchery‐typical barren environments, rearing in structured‐stable environments decreased behavioural variation. This effect, which occurred during development and did not involve selection, demonstrates a different mechanism for change in behavioural variation in captivity. These experiments show that effects of structure and structural stability occur at the level of both average behaviour and behavioural variation, and suggest that these effects should be considered when fishes are reared in hatcheries for later release into the wild.

Increases in steelhead (Oncorhynchus mykiss) redd abundance resulting from two conservation hatchery strategies in the Hamma Hamma River, Washington

Conservation hatcheries for anadromous salmonids that aim to increase production and minimizing genetic, ecological, and demographic risks have not been experimentally tested for their ability to increase number of adults spawning in the natural environment. The conservation hatchery program for steelhead (i.e., sea-run rainbow trout, Oncorhynchus mykiss) evaluated in this study caused an increase in the number of redds in the supplemented Hamma Hamma River compared with the presupplementation period. Three control populations (nonsupplemented) either remained stable or declined over the same period. The increase in redds from hatchery-produced spawners did not reduce the redd production from natural-origin spawners. The strategy of rearing and releasing adult steelhead accounted for the greatest proportion of redd abundance increases. Environmentally induced differences in spawn timing between the adult release group and anadromous adults of hatchery and natural origin may explain why the adult release group and anadromous adults assortatively formed pairing combinations on the spawning grounds. Although captively reared adults produced the majority of redds in years they were released in substantial numbers, uncertainty regarding the relative reproductive success of this strategy suggests caution in recommending one strategy over the other. A demographic boost to the naturally spawning population was effected while managing to minimize negative ecological consequences.

The influence of family-correlated survival onNb/Nfor progeny from integrated multi- and single-generation hatchery stocks of coho salmon (Oncorhynchus kisutch)

There exist surprisingly few data on the final variance and mean of family sizes for hatchery-born fish at the adult stage. Thus, it is difficult to predict, for a conservation hatchery operation that minimizes the variance in progeny number, how much lower the true effective population size (Ne) of a cohort of hatchery-born adults will be than Nepredicted simply by the number of parents that produced them. We used parentage analysis to estimate the survival and Nefor two integrated stocks of hatchery coho salmon (Oncorhynchus kisutch). One hatchery is a multigeneration stock obtained by spawning 70% hatchery with 30% naturally reproducing fish, whereas the second is a single-generation stock derived from naturally reproducing coho. There was no significant difference in average overall survival between stocks, but observed Newas significantly less than expected for each stock. Family-correlated survival contributed to roughly a 20% reduction in Neover the freshwater and marine life stages. This reduction is similar to previous estimates and suggests a value that can be used when estimating the effective number of hatchery parents in applications of the Ryman–Laikre formula (at least for programs such as ours that attempt to equalize sex ratios and family sizes).

Evaluation of lethal and non‐lethal sampling methods for the detection of white sturgeon iridovirus infection in white sturgeon, Acipenser transmontanus (Richardson)

Pectoral fin tissue of white sturgeon was investigated as a potential non-lethal sample source for the detection of white sturgeon iridovirus (WSIV) infection. Histopathology and polymerase chain reaction (PCR) results using fin tissue were compared with the standard lethal histopathology sampling method that utilizes head tissue. Tissues for each of the three sampling methods were collected weekly for 8 weeks from individual sturgeon undergoing an experimental cohabitation challenge with fish infected with the Abernathy isolate of WSIV. Non-lethal fin histopathological evaluation did not reveal infection during the first 3 weeks of sampling, while non-lethal PCR and the lethal method were variable. However, all three sampling methods were equally capable of identifying infection from 4 to 8 weeks post-exposure. Of the survivors tested, all were negative by PCR and the lethal method, and only one fish was identified as being positive by non-lethal fin histopathology. In another experiment, all three sampling methods were applied to asymptomatic WSIV carriers in a case study conducted at the Kootenai Tribal Sturgeon Conservation Hatchery. Results showed that both lethal and non-lethal fin histopathology were equally effective in detecting infection, but PCR was unable to identify this strain of WSIV. Depending on the virus isolate, these results suggest that non-lethal sampling of fin tissue (histopathology or PCR) is comparable with the lethal sampling method at identifying WSIV infection once infection is established, and under certain circumstances may provide an alternative to lethal sampling.

The impact of repeat spawning of males on effective number of breeders in hatchery operations

In conservation hatcheries, typically a great emphasis is placed on maximizing the effective number of breeders through spawning an appropriate number of spawners, spawning equal numbers of males and females when possible, and by mating either in a single-pair or factorial fashion. A commonly encountered problem, especially in small operations with anadromous salmonids, is a shortage of males at some point during the season, so that some males need to be spawned multiple times. This has an impact on the genetically effective number of breeders, and the commonly used equations for effective number are not applicable. In this paper I derive a relatively simple equation for effective number of breeders when some males are multiply spawned but reproductive contribution within spawning classes are equal: N b , m ≈ N tot − 1 / μ t ∑ i = 1 k − 1 ∑ j = i + 1 k N i N j ( i − j ) 2 ( ∑ i = 1 k i N i ) 2 + 1 , where i is the number of times a male is spawned, N i the number of males spawned i times, and μ t the mean gametic contribution. I also derive an equation that allows relaxation of the assumption of equal contribution within classes. I then develop a number of simple and accurate approximations for the effective number of breeders. The equations can be applied to any situation in which there are discrete spawning classes in which the average reproductive contribution of any one class can be expressed as a multiple of that of another class.

Genetic Diversity in Steelhead before and after Conservation Hatchery Operation in a Coastal, Boreal River

AbstractAllelic variation at 10 DNA microsatellite loci was assayed in scale samples of steelhead Oncorhynchus mykiss (n = 333) collected between 1976 and 2003 from the lower main stem of the Kitimat River, British Columbia. Our objectives were to (1) investigate the genetic diversity of wild steelhead populations in the river before hatchery stocking began in 1984 (baseline samples: 1976–1977, 1983–1984; n = 145) and (2) assess the potential genetic impacts of interbreeding of returning hatchery adult fish with wild spawners over almost 20 years of large‐scale hatchery operation (1987–2003; n = 188). The annual target number of wild broodstock adults used for hatchery production was 40 (20 of each sex) but varied from 9 to 39 among years. The level of population subdivision (ϑ) among Kitimat River samples was low (0.004) and not significantly different from 0. Tests of ϑ between prehatchery and posthatchery operation indicated no significant changes. Similar results were obtained using other measures of genetic differentiation (principal components analysis of microsatellite allele frequencies and Cavalli‐Sforza genetic distance). Our data, however, did indicate a slight but significant reduction in allelic richness after hatchery stocking. Pairwise tests for genetic differentiation among samples from different year‐classes were nonsignificant. We conclude that for the current management regime there is little apparent impact of hatchery practices on either the genetic structure or variation within the lower main‐stem Kitimat River steelhead, but there may be a reduction in rare alleles. The practice of using substantial numbers of wild fish and multiple year‐classes in the hatchery may have minimized genetic changes via genetic drift.

Rearing in Enriched Hatchery Tanks Improves Dorsal Fin Quality of Juvenile Steelhead

AbstractThe present study compared the dorsal fin condition of juvenile steelhead Oncorhynchus mykiss reared in conventional hatchery tanks, enriched hatchery tanks (i.e., with the addition of submerged structure, overhead cover, and underwater feeders), and a natural stream to determine whether structural enrichment would reduce dorsal fin erosion in hatchery‐reared fish. Dorsal fin height at 27 d postemergence did not differ significantly between the two hatchery rearing treatments. Steelhead reared in the conventional tanks had dorsal fins 78% as long as steelhead reared in enriched tanks and in the natural stream at 50 d postemergence (P < 0.05) and 45–55% as long at 64 d postemergence (P < 0.05). Variation in fin length did not substantially affect the ability to achieve dominance in agonistic contests for feeding territories; fish with longer dorsal fins won approximately 57% of contests against fish with fins that were 25% shorter on average. Rearing methods (such as structural enrichment), that simultaneously improve several attributes of juvenile salmonid morphology, physiology, or behavior may be important in the development of conservation hatchery rearing strategies.

Genetic and demographic implications of aquaculture in white sturgeon (Acipenser transmontanus) conservation

This study uses a genetic individual-based model of white sturgeon (Acipenser transmontanus) populations in a river to examine the genetic and demographic trade-offs associated with operating a conservation hatchery. Simulation experiments evaluated three management practices: (i) setting quotas to equalize family contributions in an effort to prevent genetic swamping, (ii) an adaptive management scheme that interrupts stocking when introgression exceeds a specified threshold, and (iii) alternative broodstock selection strategies that influence domestication. The first set of simulations, designed to evaluate equalizing the genetic contribution of families, did not show the genetic benefits expected. The second set of simulations showed that simulated adaptive management was not successful in controlling introgression over the long term, especially with uncertain feedback. The third set of simulations compared the effects of three alternative broodstock selection strategies on domestication for hypothetical traits controlling early density-dependent survival. Simulated aquaculture selected for a density-tolerant phenotype when broodstock were taken from a genetically connected population. Using broodstock from an isolated population (i.e., above an upstream barrier or in a different watershed) was more effective at preventing domestication than using wild broodstock from a connected population.

Potential benefits of a conservation hatchery program for supplementing Oregon coast coho salmon (Oncorhynchus kisutch) populations: a stochastic model investigation

This study developed a stochastic life cycle model to simulate idealized supplementation strategies to investigate the following question: under what circumstances could hatchery fish stocking contribute to the recovery of Oregon coast coho salmon (Oncorhynchus kisutch)? Simulations were used to find a solution space, defined by the attributes of wild and hatchery-bred salmon, their offspring, and their environments, where hatchery fish could supplement natural production without further depressing it until natural or human factors restricting production were relieved. These simulations suggest that short-duration, tightly controlled, low-intensity conservation hatchery programs designed to minimize genetic and ecological risks may yield minor short-term increases in adult coho salmon abundance while posing significant ecological and genetic risks. No solution space was found that indicated clear long-term benefits from such a supplementation program. Of all the management actions modeled, habitat restoration offered by far the largest and only permanent gains in coho salmon abundance while posing no genetic or ecological risk to the fish. The modeled benefits of habitat restoration were significant regardless of assumptions made about the fitness of hatchery fish and their offspring.