Hatchery Trout Research Articles

Survival and Dispersal of Hatchery Triploid Rainbow Trout in an Idaho River

AbstractHatchery rainbow trout Oncorhynchus mykiss of catchable size (hereafter, “catchables”) are commonly released into streams to improve angler catch and harvest rates, but returns are often less than 50% and the fate of unharvested catchables is largely unknown, especially for sterilized hatchery trout. The survival and dispersal of triploid catchables were investigated using snorkel and telemetry techniques to quantify the persistence and dispersal of catchables stocked three times during the summer of 2006 (June, July, and August) into an Idaho river in which a minimum length regulation precluded harvest. Counts of catchables stocked with T‐bar tags (n = 900) and catchables emitting active radio transmitter codes (n = 54) steadily declined throughout the three observation periods. Dispersal of T‐bar‐tagged catchables 30 d poststocking was generally downstream of the stocking point (median dispersal = 100 m). The median values of the maximum known downstream and upstream dispersal distances for catchables with radio transmitters were 5.0 and 1.2 km from the stocking point, respectively. Only four transmitter‐implanted catchables were still alive on November 1, when the study ended. On average, 85% of catchables with radio transmitters were presumed dead at 30 d poststocking (average persistence = 14.3 d). A similar rate of decline was observed for T‐bar‐tagged catchables. Managers wishing to maximize return‐to‐creel rates of sterile catchables in lotic systems might do so by limiting stocking events to within 3 weeks of expected needs and limiting the stocking locations to within 1 km of areas frequented by anglers.

Mechanical control of Ichthyophthirius multifiliis Fouquet, 1876 (Ciliophora) in a rainbow trout hatchery

Ichthyophthirius multifiliis, more commonly known as ‘white spot’ is recognised as one of the most pathogenic diseases of wild and cultured freshwater fish. In trout hatchery systems infections can quickly establish and result in high mortality if left unregulated. Current control centres around the use of regular bath treatments with formalin, however, treatments are not always effective and are labour intensive. Environmentally safe, non-chemical alternatives are required. This paper describes the performance of a mechanical system developed to remove cysts from commercial trout raceways. The system consists of two parts: a specially designed suction head connected to a pump that is used to vacuum the bottom of hatchery raceways, and a low-adhesion polymer raceway lining. Following tests on a series of potential linings, the most efficacious product in preventing settlement of cysts was used to line three raceways in a commercial rainbow trout ( Oncorhynchus mykiss) hatchery. Over a period of three months, lined raceways were vacuumed on a daily basis. The three control raceways were maintained according to the farms normal husbandry procedures. Approximately thirty fish were sampled from each raceway at fortnightly intervals, and the abundance of the parasite in each raceway determined. The mechanical system led to a significant reduction in the abundance of the parasite in the test raceways, with a mean abundance of 361.88 ± 260.75 parasites per fish in control raceways compared with 1.64 ± 1.59 parasites per fish in the test raceways at the peak of the infection. Additionally fish survival was significantly higher in test raceways over control, with a mean of 84.5% of the stock surviving in the test raceways compared with only 70.6% in the controls by trial end.

Migration performance of wild and hatchery sea trout ( Salmo trutta L.) smolts—Implications for compensatory hatchery programs

Migration success of hatchery-reared and wild sea trout smolts through the lower stretches and the estuary of a Baltic Sea river were studied. During 3 years, wild and hatchery trout smolts were implanted with acoustic transmitters and released 14 km upstream from the river mouth. In order to monitor their out-migration pattern, acoustic receivers were deployed along the migratory route. Data on number of fish detected and date and time of detections were analysed and the migratory performance of wild and hatchery-reared fish was compared. A significantly higher proportion of wild fish (80%) successfully migrated to the coast compared to fish of hatchery origin (27.5%) and migration was faster in wild smolts. Hatchery fish were larger and had a higher condition factor and lipid concentrations, which are proposed as possible reasons for the poorer migratory performance of the hatchery-reared fish.

Sixty years of anthropogenic pressure: a spatio‐temporal genetic analysis of brown trout populations subject to stocking and population declines

Analyses of historical samples can provide invaluable information on changes to the genetic composition of natural populations resulting from human activities. Here, we analyse 21 microsatellite loci in historical (archived scales from 1927 to 1956) and contemporary samples of brown trout (Salmo trutta) from six neighbouring rivers in Denmark, to compare the genetic structure of wild populations before and after population declines and stocking with nonlocal strains of hatchery trout. We show that all populations have been strongly affected by stocking, with admixture proportions ranging from 14 to 64%. Historical population genetic structure was characterized by isolation by distance and by positive correlations between historical effective population sizes and habitat area within river systems. Contemporary population genetic structure still showed isolation by distance, but also reflected differences among populations in hatchery trout admixture proportions. Despite significant changes to the genetic composition within populations over time, dispersal rates among populations were roughly similar before and after stocking. We also assessed whether population declines or introgression by hatchery strain trout should be the most significant conservation concern in this system. Based on theoretical considerations, we argue that population declines have had limited negative effects for the persistence of adaptive variation, but admixture with hatchery trout may have resulted in reduced local adaptation. Collectively, our study demonstrates the usefulness of analysing historical samples for identifying the most important consequences of human activities on the genetic structure of wild populations.

Tales from scales: old DNA yields insights into contemporary evolutionary processes affecting fishes

Salmon and trout populations are suffering declines in abundance and diversity over much of their range around the Atlantic and Pacific rims as a consequence of many factors. One method of dealing with the decline has been to produce them in hatcheries but the wisdom of this approach has been hotly debated (e.g. Hilborn & Winton 1993; Waples 1999; Brannon et al. 2004). One concern is that domesticated hatchery strains will interbreed with locally adapted wild fish; but how do we study the genetic effects if the introgression might have occurred in the past? Hansen (2002) used DNA isolated from archived scales from brown trout, Salmo trutta (Fig. 1), to show that domesticated trout had, to varying degrees, genetically introgressed with wild, native trout in two Danish rivers. Extending that study, Hansen et al. (2009) have examined DNA from brown trout scales in six Danish rivers collected during historical (1927-1956) and contemporary (2000-2006) periods and from two hatchery source populations, to assess the effects of stocking nonlocal strains of hatchery trout and declining abundance on genetic diversity. Using 21 microsatellite loci, they revealed that genetic change occurred between the historic and contemporary time periods. Many populations appeared to have some low level of introgression from hatchery stocks and two populations apparently experienced high levels of introgression. Hansen et al. (2009) also showed that population structure persists in contemporary populations despite apparent admixture and migration among populations, providing evidence that the locally adapted populations have struggled against and, to some extent, resisted being overwhelmed by repeated introductions of and interbreeding with non-native, hatchery-produced conspecifics.

Competition between hatchery‐raised and wild brown trout Salmo trutta in enclosures – do hatchery releases have negative effects on wild populations?

Abstract – We compared the growth and prey consumption of juvenile hatchery and wild brown trout of similar genetic origin in 12 wire mesh cages in a natural river in North‐Eastern Finland. Wild trout started feeding shortly after the start of the experiment, and clearly earlier than novel hatchery trout, but ate less in the presence of hatchery trout. When accompanied with wild trout, novel hatchery trout started to feed earlier, consumed more live prey, and lost less weight than when in allopatry. Hatchery trout grew more slowly than wild trout. To our knowledge, this is the first study to show that hatchery trout benefit from the presence of wild, experienced trout in a complex semi‐natural environment. However, our results also indicate that the benefits to hatchery fish are not transferred to wild fish, and ultimately that care should be exercised in management actions when using hatchery trout to supplement wild populations. On the other hand survival potential of the novel hatchery brown trout could be better in the wild when also undomesticated trout are present.

The study of complex chemical effects of Aquagerm (Germicide) on pH of water, saprolegnia fungus, streptococcus bacteria and behavioral change of Rainbow trout.

A highly specific and multipotential disinfectant, Aquagerm, was designed for using in aquatic farms by Research Group of Fazel Derakhshan Company (Tehran, Iran). Its effect on water pH, survival rate and behavior changes of fish as well as therapeutic effects on saprolegniasis and sterptococcosis were studied. This disinfectant reduced water pH to 2-4 units below the basal level at 1?100 and 1?200 dilutions during 30min of treatment. However, by 1?2000 and 1?2500 dilutions, pH reduction was only one unit at the same period. Interestingly, at recent dilutions pH was in optimum range which is suitable for cultivation. Furthermore, 1?2000 and 1?2500 dilutions did not cause any disorder in fish survival and behavior. This compound has bacteriostatic effect on Saprolegnia spp. in fish hatcheries. Our investigation showed that 1?2000 and 1?2500 dilutions made 82- 85 % survival of eggs in rainbow trout hatcheries. However, these dilutions were not suitable ones for reducing Streptococcus spp. to 108 bacteria per milliliter. It should be mentioned that these dilutions are too high for being used at farm condition.

Stable isotope tracing of trout hatchery carbon to sediments and foodwebs of limestone spring creeks

Limestone springs support productive ecosystems and fisheries, yet aquaculture may modify or impair these ecosystems. We determined trout hatchery organic contribution to spring creek sediments and foodwebs with natural abundance stable isotope methods. Hatchery feed, waste, and trout were significantly enriched in δ 13C relative to autotrophs and wild fish. Spring creek sediments were enriched in δ 13C toward the hatchery endmember relative to reference streams without hatcheries and relative to a larger larger-order, spring-influenced stream. Contribution of hatchery C to spring creek sediments was greatest during March and associated with greatest sediment %C. Contribution of hatchery C to pollution-tolerant isopod diet was 39–51% in a stream receiving limestone spring water via hatchery effluent. Isopods of one spring creek also relied on hatchery-derived C within one month of hatchery closure. Four years later, less pollution pollution-tolerant amphipods dominated and consumed non-vascular over vascular autotrophs (86%). Isopods of a second spring creek with an active hatchery did not appear to be using hatchery matter directly, but were enriched in δ 34S relative to a spring creek tributary with no hatchery influence. Isopods in both of these streams were relatively enriched in δ 15N, indicating general nutrient enrichment from surrounding agricultural land use. The contribution of hatchery vs. wild fish in diet of herons and egrets was traced with δ 13C of guano. These birds were strongly dependent on stocked trout in a spring creek with a recently closed state trout hatchery, and also near another large, state-run hatchery. Heron dependence on hatchery fish in the spring creek decreased with time since hatchery closure. Use of stable isotope natural abundance techniques in karst spring creeks can reveal stream impairment due to aquaculture, specific C sources to bio-indicating consumers, losses of farmed fish to predation, and potential exposure of higher order consumers to contaminants associated with aquaculture.

Isolation of 15 single nucleotide polymorphisms from coastal steelhead, Oncorhynchus mykiss (Salmonidae)

We describe 15 single nucleotide polymorphisms (SNPs) isolated in coastal California populations of steelhead (Oncorhynchus mykiss). SNP loci were developed using a 'gene-targeted' approach, which involved the development of primers from functional genes in O. mykiss that were deposited in GenBank or in the published literature. These markers show a wide range of variability in three coastal steelhead populations, and will be useful in population genetic studies and in pedigree reconstruction. Potential applications include evaluation of population structure, introgression between native and hatchery trout, and evaluating reproductive success.

A genetically distinct wild redband trout (Oncorhynchus mykiss gairdneri) population in Crane Prairie Reservoir, Oregon, persists despite extensive stocking of hatchery rainbow trout (O. m. irideus)

Crane Prairie Reservoir in the upper Deschutes River Basin has historically supported a wild population of migratory Deschutes River redband trout. Owing to its status as a premier destination for recreational angling in Oregon, the reservoir has been stocked with domesticated hatchery rainbow trout since 1955. In recent years the wild redband trout population has experienced a substantial decline. Effects on productivity related to genetic interaction with naturally spawning hatchery-origin fish (fitness risks) have not been determined. The species Oncorhynchus mykiss has been characterized with substantial genetic diversity throughout the Deschutes River Basin that further heightens the challenge of identifying specific conservation needs of wild populations. A conservation plan for Crane Prairie wild redband trout requires a better understanding of the natural reproductive success of out-of-basin hatchery trout in the reservoir tributaries, and the similarity between Crane Prairie redband trout with other extant redband trout populations in the basin. Using a suite of 17 microsatellite nuclear DNA markers, we evaluated the genetic structure among Crane Prairie Reservoir redband trout, hatchery rainbow trout, and two adjacent populations of redband trout from within the Upper Deschutes River Basin. We observed significant heterogeneity between the hatchery and wild Crane Prairie populations that may reflect differences in life histories, differential productivity and assortative mating. The genetic distinctions observed among the three redband trout populations suggest restricted gene flow and genetic drift within the upper basin. Temporally stratified sampling and larger numbers of samples will be necessary to confirm these conclusions.

Efficiency of Trout Raceway Quiescent Zones in Controlling Suspended Solids

AbstractBest management practice for effluent control of trout hatchery discharges calls for separation of cleaning waste by collection in quiescent zones (QZs) at the end of each raceway. The efficiency of QZs in trapping solid waste over a range of fish densities, water velocities, and QZ areas, measured by overflow rate (OFR), were studied. Solids retention in the QZs was negligible at velocities of 2.0 and 4.4 cm/s (regardless of fish density) and at a fish density of 40 kg/m3 (regardless of velocity). Solids collection efficiency was affected more by OFR and fish density than by velocity. At OFRs of 0.5 and 1.0 cm/s, solids collection was significantly better at a fish density of 160 kg/m3 than at a density of 80 kg/m3. At a density of 80 kg/m3, solids retention was better at an OFR of 0.5 cm/s than at an OFR of 1.0 cm/s. Solids retention was not affected by OFR at a fish density of 160 kg/m3. Velocities in the range of 2.4–3.4 cm/s did not affect solids collection efficiency at either fish density. Thus, optimum conditions for solids collection in trout raceway QZs were 2.4–3.4‐cm/s velocity and (1) a fish density of 160 kg/m3 at an OFR of 0.5 or 1.0 cm/s or (2) a density of 80 kg/m3 at an OFR of 0.5 cm/s. Under these conditions, up to 20% of the total solids load was collected in the raceway QZs. Although this value is lower than expected based on the literature, actual solids levels were less than 5 mg/L and solids concentrations in the effluents of downstream units of serial raceways were not additive.

Variation in reproductive success and effective number of breeders in a hatchery population of steelhead trout (Oncorhynchus mykiss): examination by microsatellite-based parentage analysis

Conservation programs that release captive-bred individuals into the wild to mix with naturally produced individuals are an increasingly common method of supporting or enhancing weak or reduced populations that otherwise may not be self-sustaining. Captive and supportive breeding can be important conservation tools for species with small or declining populations; however, in the case of hatcheries producing salmonid fishes, detailed evaluation of spawning programs is rare. We examined variation in reproductive success, measured by adult offspring production, from three parental generations of hatchery-bred steelhead trout (Oncorhynchus mykiss) using an exclusion-based method of genetic parentage assignment. Reproductive success varied greatly among individuals (especially males) and was correlated with fecundity and maternal spawning date. Estimates of egg to smolt survival for the population as a whole among years ranged from 64% to 95%, marine survival ranged from 0.32% to 2.30%, and the number of adults produced per female ranged from 0 to 18 and the number of adults produced per male ranged from 0 to 32. The effective number of breeders ranged from 11% to 31% of the census population size for that brood year. These ratios fell within estimates from estimates of Ne/N in chinook (O. tshawytscha) and rainbow trout (O. mykiss) hatchery populations.

Characteristics of the hatchery-reared Black Sea salmon Salmo trutta labrax

For conserving the unique representative of salmonids—the Black Sea salmon Salmo trutta labrax—its hatchery rearing was initiated in 1998 at the Adler trout hatchery farm (Northern Caucasia). Fish were kept in concrete tanks. The comparative assessment of hatchery-reared fish and salmon from natural populations revealed their similarity by dates of the onset of smoltification, ratio of spawners maturing at different ages, and the weight, sizes, and fecundity of females. The quality of sexual products and progeny obtained from spawners of the initial brood stock was high. The data obtained indicate that the method of hatchery rearing the Black Sea salmon is promising.

Use of Immunohistochemical and PCR Methods in Diagnosis of Infectious Haematopoietic Necrosis Disease in Some Rainbow Trout Hatcheries in Iran

The aim of this research was investigation on infection in reproducing and breeding centers of Rainbow trout in Iran by infectious Necrosis haematpoietic virus. We collected 100 samples from 100 reproducing and breeding centers of Rainbow trout of the Iran that showed clinical sings or were healthy in appearance in larva stage and finger link. Samples were tested by immunohistochemistry and Nested-PCR methods. By immunohistochemistry methods 35 samples and by PCR 43 samples were positive. There were 38 samples with clinical symptoms of Infectious Haematpoietic Necrosis. The results of this study show the dispersion of Infectious hematopoietic necrosis virus in some reproducing and breeding centers of Rainbow trout in the Iran. Also the result of two methods had acceptable overlapping.

Evidence for reduced genetic variation in severely deformed juvenile salmonids

Inbreeding is one of the factors that can result in high infant mortality. In many species, however, mortality at early life stages is very difficult to observe in the wild and estimates from later life stages may therefore underestimate the effects of reduced genetic variability on fitness. Using microsatellites, we compared the amount of genetic variation in severely deformed fry of Lake Saimaa salmon (Atlantic salmon, Salmo salar) and brown trout (Salmo trutta) hatchery brood stocks with normal fry from the same brood stocks. We observed significantly lower standardized heterozygosity and higher internal relatedness values for deformed fry of both species compared with normal fry. Our results suggest that (i) inbreeding can be an important factor causing severe deformities in juvenile salmonids and (ii) high mortality of severely deformed low heterozygosity individuals in early life stages may partly explain why some studies exploring heterozygosity–fitness correlations fail to find any association. An important direction for future research on this topic will be to compare the results of experiments conducted in captivity with those of similar experiments conducted in wild or semi-wild conditions, as such studies would help to better understand the direct relevance of research conducted in captivity with respect to the conservation of wild populations.

No difference in survival, growth and morphology between offspring of wild‐born, hatchery and hybrid brown trout (Salmo trutta)

Abstract – We studied survival, growth and morphological characters in the offspring of native hatchery and wild‐born anadromous brown trout (Salmo trutta) and their hybrids (wild‐born female × hatchery male and wild‐born male × hatchery female) in a 1‐year field experiment. We also conducted laboratory studies where we examined social interactions between the offspring of the same hatchery and wild‐born trout. All offspring were raised in a hatchery and nose tagged before being released into the stream. In total, 1125 individuals were released into the stream (1999) and a total of 614 individuals were recovered (2000). We found no differences in growth and survival between the offspring of hatchery, wild‐born and hybrid trout. Morphology was also similar among groups, where only 38% females and 36% males were classified into the right category, which were only 12% better than random classification. In the laboratory experiment, we compared only the offspring of hatchery and wild‐born trout with respect to growth, dominance, aggressiveness, feeding and activity. We found small differences between the offspring of hatchery and wild‐born fish with respect to growth but this effect was not found in the field experiment. Our result suggests that the offspring of hatchery trout and hybrids between hatchery and wild‐born trout performed equally well to the offspring of wild‐born trout.

Routine Use of Sterile Fish in Salmonid Sport Fisheries

Since 1997, Idaho Department of Fish and Game hatchery and research personnel have worked cooperatively to develop a sterile trout program with the primary goals of protecting the genetic integrity of native stocks while continuing to supply hatchery-reared trout for harvest-oriented anglers. Results of recent field evaluations of sterile rainbow trout (Oncorhynchus mykiss) demonstrate that they provide recreational fisheries of equal or superior quality to normal diploid fish when stocked as catchables in streams or as fingerlings in productive lentic systems. Our preliminary evaluations suggest that use of sterile trout in high mountain lakes may require stocking adjustments or may eventually prove problematic because of lower survival rates. Sterile trout eggs can be readily purchased from commercial sources or produced from agency broodstocks with nominal equipment and manpower costs. To gain a better understanding of sterile fish use by other agencies, we conducted a U.S. state phone survey during 2005, and posed questions to fisheries administrators regarding their stocking practices. Officials from 10 states indicated that they had ongoing programs for sterilizing hatchery salmonids. Eight of these programs were located in the western United States, while only two occurred east of the Mississippi River. The presence of native species either listed under the Endangered Species Act or petitioned to be listed has greatly influenced agency interest in sterile fish programs. Regardless of native species status, we believe that expansion of sterile hatchery trout programs can improve conservation and management programs in other states. Despite our obvious enthusiasm for use of sterile trout in recreational fisheries, they are not a panacea, and we call for additional evaluations with normal diploid trout in states developing such programs.

Introgression variability among Iberian brown trout Evolutionary Significant Units: the influence of local management and environmental features

Summary1. A comprehensive analysis was carried out on the effects of stocking on the genetic structure of Iberian brown trout evolutionary lineages. Introgression and genetic diversity were estimated from allozyme results of 307 populations based on own data (180) and available literature (127). Stocking records, angling regulations and environmental features related to hatchery trout performance were also analysed to determine the underlying mechanisms of the introgression effects.2. Fifty per cent of analysed populations showed introgression by genes of hatchery origin. The mean introgression estimated by the single locus approach was 0.134. An increment of both heterozygosity and polymorphism was observed when introgression increased in stream‐dwelling populations, which could finally produce a homogenisation of the genetic structure of populations and a decrease of the species’ genetic diversity.3. Introgression rate varied among Iberian evolutionary lineages (Evolutionary Significant Units), and was correlated with the stocking effort, except for the North Atlantic basins. The lack of adaptations for migratory behaviour in hatchery trout could explain the low impact of stocking in North Atlantic rivers where anadromous populations occur.4. Angling regulation did not seem to influence the survival of hatchery trout. Introgression tends to be higher in heavily stocked localities with fertile waters and stable discharge, which may favour the performance of hatchery trout.5. Trout management must be based on increasing population size by means of habitat improvement and sustainability of naturally reproducing wild stocks through appropriate angling regulations.

The Early History of Fisheries Management in Michigan

The culture and stocking of fish in North America began in the last half of the nineteenth century. Fish culture was seen as a way to bolster the realized decline of fish populations, but also as a way to introduce new species thought to be desirable to all waters. A private brook trout hatchery was started in Clarkston, Michigan in 1867, and the state of Michigan built their first hatchery in Pokagon in 1873. The enthusiasm for stocking was eventually tempered with the realization that more knowledge was needed about the life history requirements of the fishes and the waters where they lived. Regulation of the fisheries had also begun. In 1920, Carl L. Hubbs, who became a noted ichthyologist, was hired at the University of Michigan. In 1930, he founded the Institute for Fisheries Research. The founding of the institute was a pivotal point in the development of fisheries management. In the next 15 years in Michigan, essentially all of the concepts of fisheries management were put into practice and evaluation was done. In 1935, Hubbs hired Albert S. Hazzard to be a full-time director of the institute. Hazzard had a Ph.D. in zoology from Cornell University and had worked as an aquatic biologist for the U.S. Bureau of Fisheries in the western United States. The third key person responsible for the advances in fisheries in Michigan was Fred A. Westerman, chief of the Michigan Department of Conservation, Fisheries Division, from 1925–1959. Westerman, who had little education beyond high school and grew up in the Michigan hatchery system, provided agency support. Hubbs assembled a group of bright graduate students, and this trio of leaders in 1930–45 utilized the students to do pioneering work in the field of fisheries management. They used an inventory of streams and lakes to determine suitable management methods, developed and evaluated lake and stream improvement methods, used the creel census to measure game fish yield, analyzed stream and lake fish populations, determined the success of different methods of planting, and initiated studies of fish migration, growth rates, food habits, fish predators, use of the piscicide rotenone, spawning habits of the common fishes, and relationships of principal game and forage fishes.

Genetic Analysis of Wild Lake Trout Embryos Recovered from Lake Michigan

AbstractThe Mid‐Lake Reef Complex (MLRC) is a large area of deep reefs that separate the two main basins of Lake Michigan. In an attempt to evaluate which of several strains of lake trout Salvelinus namaycush stocked in Lake Michigan are actively spawning at the MLRC, eggs that had been deposited by spawning lake trout were collected at three sites on East Reef. These eggs were incubated and shown to be viable and capable of developing to the emergent fry stage. The samples were genotyped at four microsatellite loci, and a proportional admixture analysis was performed to estimate the genetic contribution of the four predominant lake trout hatchery strains used to stock the MLRC. These estimates were then compared with the abundance of each strain stocked since 1985. The point admixture estimates indicated unequal spawning success among strains in the wild. Specifically, the Seneca Lake strain appeared to be the most successful, while the Lewis Lake strain was the least successful and may not be spawning in the wild. The implications for conservation management are also discussed.