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| Author | : Leandro Anibal Becker |
| Publisher | : |
| Total Pages | : |
| Release | : 2011 |
| Genre | : Aquaculture |
| ISBN | : |
| Author | : Shawn Richard Garner |
| Publisher | : |
| Total Pages | : 148 |
| Release | : 2009 |
| Genre | : Pacific salmon |
| ISBN | : 9780494542897 |
Understanding natural breeding in Pacific salmon may offer insights for the management of these economically and culturally important fishes. I examined mating patterns by allowing Chinook salmon ( Oncorhynchus tshawytscha ) to breed in experimental stream channels, and used genetic analyses to determine reproductive success for each fish. Phenotypic characteristics including body size and colouration had mixed effects on reproductive success, and were generally more important for reproductive success in males than females. Mating patterns were also affected by the genes of the major histocompatibility complex (MHC), as females mated with males that significantly increased the genetic diversity of their offspring at the MHC class IIB locus. Behavioural observations of spawning fish revealed that females directed aggression at more MHC similar males than expected by chance, providing a possible mechanism of female choice. However, male harassment of MHC similar females appeared to interfere with female mating preferences, as females that were the target of high levels of male aggression had lower than expected MHC diversity in their offspring. The potential for female skin carotenoid displays to be used in mate choice was examined by measuring carotenoid and retinoid concentrations in the skin, eggs, flesh and plasma of Chinook salmon. Skin and egg carotenoid concentrations were not correlated, which suggests that skin carotenoids do not advertise egg carotenoid resources to males, but may instead contribute to cryptic female colouration. The behavioural observations of spawning fish provided evidence for egg cannibalism, which contradicts the longstanding belief that Pacific salmon cease feeding when they return to fresh water to spawn. Analysis of stomach contents showed that multiple species of Pacific salmon consumed eggs during spawning, and feeding trials confirmed that mature fish could digest eggs. The final chapter compares hormone concentrations and behaviour in juvenile Chinook salmon produced by natural and hatchery breeding. Differences in the rearing environment affected cortisol concentrations and feeding rates, whereas androgen concentrations and aggression appeared to differ based on the breeding method itself. Together these findings suggest that natural breeding has important applications for managing Pacific salmon in the wild and in aquaculture.
| Author | : Roy E. Beaty |
| Publisher | : |
| Total Pages | : 540 |
| Release | : 1992 |
| Genre | : Chinook salmon |
| ISBN | : |
The average size and age of chinook salmon (Oncorhynchus tshawytscha) caught in commercial fisheries along the Pacific Coast of North America have decreased substantially in this century. These declines might be caused in part by changes in size and age at maturity within the stocks contributing to those fisheries. Upriver Brights (Brights), a stock of fall chinook salmon in the Columbia River, are one of those stocks. The purposes of this study were to (1) determine if average size and age at maturity of Brights have declined, (2) gain a better understanding of the factors that may contribute to such declines, and (3) describe potential consequences of these changes. Data from in-river fisheries suggest that the average weight of mature Brights returning to the Columbia River has decreased approximately 2.7 kg since the 1910s, an average rate of about 0.1 lb·yr−1 (45 g·yr−1). Most of the potential biases in these data tend to make this estimate conservative. Insufficient data were available to describe changes in average age at maturity. There are many potential causes for the decline in average size of mature Brights, including factors that affect very early life stages. Other researchers have determined that size at maturity appears to be highly influenced by inheritance, gender, and growth rate. I describe how maternal size can influence -- through time of spawning, choice of spawning site, and egg size -- the viability of the young, which carry the dam's genes for size. The size-related ability to produce viable offspring may have been changed by modifications in the environment. Very little is known about how changes in the natural environment for spawning, incubation, and rearing may have contributed to a decline in average size at maturity. Artificial propagation and rearing, such as at Priest Rapids Hatchery, seems to produce adult Brights that are smaller, younger, and more likely to be male than their natural counterparts. The net result is that the average hatchery fish may have only about 0.80 of the reproductive potential of the average natural fish. Changes in growth conditions in the ocean probably did not contribute to the change in size, although the ocean fisheries of Southeast Alaska and British Columbia appear to select, in the genetic sense, against large size and old age in Brights. Since 1978, in-river commercial fisheries have caught larger Brights and a higher proportion of females than are found in the escapement of the Priest Rapids Hatchery component of the stock, but the fisheries impact the two sexes differently by taking the larger males and the smaller females. The effect on the natural component may differ because of their apparently larger average size. I found no evidence that larger fish or more females were caught when 8-in. minimum restrictions were in effect on gillnet mesh size relative to periods when mesh size was not restricted. Impounding the mainstem during the last 50+ yr may have removed obstacles to migration (e.g., Celilo Falls) that selected for large size in Brights, but that hypothesis could not be tested. The perserverance of larger and older phenotypes in the Bright stock suggests that countervailing selection -- perhaps during spawning, incubation, and/or early rearing -- may have resisted the effects of a century of size- and age-selective fisheries. That resistance, however, may reduce the productivity of the stock. Declines in average size and age at maturity can have undesireable consequences. Lower average size means less biomass landed and lower commercial value. Lower average fecundity and a diminished ability to reproduce in some environments are also expected. Loss of size and age classes may reduce the ability of the stock to adapt to environmental variations. These results are relevant to several management practices. A holistic approach to fishery management issues is necessary to avoid erroneous conclusions based on narrow perspectives. Measuring reproductive potential of the catch and escapement would be superior to the conventional practice of simply counting numbers of fish. Many aspects of artificial propagation can be improved, including broodstock aquisition, mating regimes, and rearing practices. Stock abundance is a major factor in determining the effect of many management practices on the stock. In general, fisheries managers must be mindful that they manage very complex natural systems.
| Author | : John Fosnick |
| Publisher | : |
| Total Pages | : 282 |
| Release | : 1994 |
| Genre | : Chinook salmon |
| ISBN | : |
| Author | : Julia R. Unrein |
| Publisher | : |
| Total Pages | : 96 |
| Release | : 2015 |
| Genre | : Chinook salmon |
| ISBN | : |
Juvenile Chinook salmon (Oncorhynchus tshawytscha) exhibit an array of life history tactics in Oregon's Willamette River Basin, yet we do not know to what extent it is driven by phenotypic plasticity or whether it is predetermined and how conditions in the early rearing environment may affect phenotype expression. We have found hatchery-origin fry sort themselves into distinct surface and bottom oriented phenotypes within days of first feeding and this orientation persists after separation. Surface and bottom phenotypes demonstrated differences in head and body morphology at 2 months post-swim up across three brood years (BY). The surface phenotype exhibits a shorter head and deeper body compared to bottom phenotype. The BY 2012 surface phenotype spent 3 times longer, on average, interacting with their mirror image in an open arena than the bottom phenotype. Tests conducted with BY 2013 fish indicated that bottom-oriented fish engaged in swimming-against-mirror behavior 5 times more than the surface phenotype when the mirror was near gravel refuge. After 8 months of rearing, the BY 2012 surface phenotype was 10% larger than bottom fish and morphometric differences persisted. Surface and bottom phenotypes from BY 2013, were reared under two temperatures and as either separate or combined phenotype groups. The two phenotypes grew at the same rate at 12°C, irrespective of separate or combined rearing, but at 7°C surface fish were significantly larger than bottom fish after three months until temperatures increased after which the two phenotypes converged. While equal in size, the morphologies of the BY 2013 orientation phenotypes were consistent with previous findings. These differences seen in body shape between the surface and bottom oriented groups are similar to differences exhibited between wild subyearling and yearling life history types in the basin. Such phenotypic differences may offer potential for predicting juvenile life history trajectory early in life.
| Author | : |
| Publisher | : |
| Total Pages | : 624 |
| Release | : 2013 |
| Genre | : Aquatic sciences |
| ISBN | : |
| Author | : Crystal R. Hackmann |
| Publisher | : |
| Total Pages | : 184 |
| Release | : 2005 |
| Genre | : Chinook salmon |
| ISBN | : |
Estuaries provide juvenile salmonids with highly productive feeding grounds, refugia from tidal fluctuations and predators, and acclimation areas for smoltification. However, these dynamic, fluctuating salinity environments may also be physiologically stressful to growing juvenile fish. In order to evaluate the costs and benefits of estuarine marshes to juvenile Chinook salmon, I observed habitat use, diet, and growth of fish in the Nehalem Estuary on the Oregon coast. I also examined physiological costs associated with salmon living in fluctuating salinities and growth rates in laboratory experiments. I collected growth, diet and osmoregulation information from juvenile Chinook salmon in three tidal marsh sites in the Nehalem Bay and from juveniles in the Nehalem River. Stomach contents indicated that a high proportion of the diet is derived from terrestrial prey. These allochthonous prey resources likely become available during the flood stages of tidal cycles when drift, emergent and terrestrial insects would become available from the grasses surrounding the water. This field study confirmed that juvenile Chinook salmon utilized fluctuating salinity habitats to feed on a wide range of items including terrestrial-derived resources. Although field studies indicate that fish in estuarine habitats grow well and have access to quality prey resources, experimental manipulations of salinities were used to quantify the physiological costs of residing in the freshwater-saltwater transitional zone. In the laboratory, I designed an experiment to investigate the physiological responses to fluctuating salinities. Experimental treatments consisted of freshwater (FW), saltwater (SW) (22-25%o); and a fluctuating salinity (SW/FW) (2 - 25%o). These treatments were based on typical salinity fluctuations found in estuarine habitats. I measured length, weight, plasma electrolytes and cortisol concentrations for indications of growth and osmoregulatory function. The fluctuating salinity treatment had a negative effect on growth rate and initial osmoregulatory ability when compared with constant freshwater and saltwater treatments. The results indicated that fluctuating salinities had a small but marginally significant reduction in growth rate, possibly due to the additional energetic requirements of switching between hyper- and hypo-osmoregulation. However, 24-hour saltwater challenge results indicated that all fish were capable of osmoregulating in full-strength seawater. In a second experiment, I manipulated feed consumption rates of juvenile spring Chinook salmon to investigate the effects of variable growth rates on osmoregulatory ability and to test the validity of RNA:DNA ratios as indication of recent growth. The treatments consisted of three different feeding rates: three tanks of fish fed 0.7 5% (LOW) body weight; three tanks fed 3% (HIGH) body weight; and three tanks were fasted (NONE) during the experiment. These laboratory results showed a significant difference in the osmoregulatory ability of the NONE treatment compared to the LOW and HIGH treatments which indicates that a reduction in caloric intake significantly effected osmoregulatory capabilities during a 24 hour saltwater challenge. Furthermore, this suggests that there is a minimum energetic requirement in order to maintain proper ion- and osmoregulation in marine conditions. Estuarine marshes have the potential to provide productive feeding grounds with sufficient prey input from terrestrial systems. However, utilization of these marshes in sub-optimal conditions could alter behavior or impair physiological condition of juvenile Chinook salmon prior to their seaward migration by providing insufficient prey resources in a potentially stressful, fluctuating environment. Therefore, the physiological costs associated with estuarine habitat use should be well understood in order to aid future restoration planning.
| Author | : Maria Elena Lang Wessel |
| Publisher | : |
| Total Pages | : 166 |
| Release | : 2004 |
| Genre | : Chinook salmon |
| ISBN | : |
"Hatcheries play an important role in the enhancement of Pacific salmon (genus Oncorhynchus) as a resource, but genetic and phenotypic divergence trom wild populations may occur as a result of founder effects, genetic drift and/or domestication. In this study, agonistic behavior, ability to establish dominance, and morphology were compared among juveniles of chinook salmon (Oncorhynchus tshawytscha) that have experienced five generations of hatchery ranching culture, juveniles derived trom the wild founding stock, and second generation hybrids of the two lines. The parent generation of all lines was cultured in the same hatchery environment as the juveniles tested. Behavioral observations were conducted in replicate artificial stream tanks; hatchery and hybrid fish were significantly more aggressive than wild derived fish. No difference was detected in the ability of fish lines to win dyadic dominance contests. Thin-plate spline analysis was used to characterize morphometric variation; hatchery and wild derived juveniles differed significantly. Canonical discriminant analysis correctly classified 88% of hatchery fish and 90% of wild derived fish. Morphologically, hybrid fish were significantly different trom both hatchery and wild derived fish. These results suggest that the differences observed between lines are genetic in origin although the sources of the divergence were not conclusively identified"--Leaf iii.
| Author | : Madilyn Marisa Gamble |
| Publisher | : |
| Total Pages | : 93 |
| Release | : 2016 |
| Genre | : Chinook salmon |
| ISBN | : |
Body size, mediated through biotic and abiotic factors affecting growth, is fundamental in determining survival as larger animals are usually less vulnerable to predation, starvation, and extreme environmental conditions (Peterson & Wroblewski 1984; Sogard 1997). Size-selective mortality is a prevalent force regulating marine survival for many anadromous salmonid species, including ESA-listed Chinook salmon (Oncorhynchus tshawytscha) in Puget Sound, WA. The “critical size – critical period” hypothesis suggests that marine survival of anadromous Pacific Salmon (Oncorhynchus spp.) is controlled by two size-selective survival bottlenecks – one during the first marine summer and another during the first marine winter (Beamish and Mahnken 2001). Previous research has indicated a strong positive relationship between the size of juvenile ESA-listed Chinook salmon (O. tshawytscha) in Puget Sound and their survival to adulthood, indicating that early marine growth drives survival (Duffy 2009). Before investigating the drivers of early marine growth, however, it is imperative to understand whether size-selective mortality occurs prior to July in Puget Sound. If so, we may be able to augment marine survival by directing conservation and restoration efforts toward the habitats or regions of Puget Sound where size-selective mortality occurs. Additionally, we must account for any size-selective mortality in estimating early marine growth, as observed weight in July would reflect an artificially inflated “apparent” growth if smaller individuals were experiencing disproportionately high mortality. In this study, we repeatedly sampled nine stocks of both wild and hatchery-origin sub-yearling Chinook salmon during their outmigration into and rearing in Puget Sound. We used scale morphometrics to determine if size-selective mortality is affecting sub-yearling Chinook salmon during their first marine summer rearing in Puget Sound, and if so, where and when that size-selective mortality occurs. We found no evidence of size-selective mortality occurring between habitats or between sampling periods within habitats, suggesting that weight of juvenile Chinook as measured in July is representative of early marine growth and that size-selective mortality occurs later in the summer or outside Puget Sound during the first marine winter. We then focused on understanding differences in growth rates across time, among habitats, and among stocks of juvenile Chinook salmon, and used bioenergetic models to determine the relative influence of prey quality, prey availability, and temperature on early marine growth rates We found that sub-yearling Chinook were larger and grew faster in offshore than in nearshore habitats, and that this difference in growth rate was likely due to differences in prey availability and may have been exacerbated by higher nearshore temperatures. The results of this study can be used to direct restoration and conservation efforts aimed at supporting early marine growth of juvenile Chinook in Puget Sound, and can augment our understanding of distribution patterns and feeding behaviors of Pacific salmon during critical growth periods.
| Author | : Pascale A. L. Goertler |
| Publisher | : |
| Total Pages | : 91 |
| Release | : 2014 |
| Genre | : |
| ISBN | : |
For many fish and wildlife species, a mosaic of available habitats is required to complete their life cycle, and is considered necessary to ensure population stability and persistence. Particularly for young animals, nursery habitats provide opportunities for rapid growth and high survival during this vulnerable life stage. My thesis focuses on juvenile Chinook salmon (Oncorhynchus tshawytscha) and their use of estuarine wetlands as nursery habitat. Estuaries are highly productive systems representing a mosaic of habitats connecting rivers to the sea, and freshwater tidal estuaries provide abundant prey communities, shade, refuge from predation and transitional habitat for the osmoregulatory changes experienced by anadromous fishes. I will be discussing the freshwater tidal wetland habitat use of juvenile Chinook salmon in the Columbia River estuary, which are listed under the Endangered Species Act. I used otolith microstructural growth estimates and prey consumption to measure rearing habitat quality. This sampling effort was designed to target as much genetic diversity as possible, and individual assignment to regional stocks of origin was used to describe the diversity of juvenile Chinook salmon groups inhabiting the estuary. Diversity is important for resilience, and in salmon biocomplexity within fish stocks has been shown to ensure collective productivity despite environmental change. However much of the research which links diversity to resilience in salmon has focused on the adult portion of the life cycle and many resource management policies oversimplify juvenile life history diversity. When this oversimplification of juvenile life history diversity is applied to salmon conservation it may be ignoring critical indicators for stability. Therefore in addition to genetic diversity I also explore methods for better defining juvenile life history diversity and its application in salmon management, such as permitting requirements, habitat restoration, hydropower practices and hatchery management. This study addresses how juvenile salmon growth changes among a range of wetland habitats in the freshwater tidal portion of the Columbia River estuary and how growth variation describes and contributes to life history diversity. To do this, I incorporated otolith microstructure, individual assignment to regional stock of origin, GIS habitat mapping and diet composition, in three habitats (mainstem river, tributary confluence and backwater channel) along ~130 km of the upper estuary. For my first chapter I employed a generalized linear model (GLM) to test three hypotheses: juvenile Chinook growth was best explained by (1) temporal factors, (2) habitat use, or (3) demographic characteristics, such as stock of origin or the timing of seaward migration. I found that variation in growth was best explained by habitat type and an interaction between fork length and month of capture. Juvenile Chinook salmon grew faster in backwater channel habitat and later in the summer. I also found that mid-summer and late summer/fall subyearlings had the highest estuarine growth rates. When compared to other studies in the basin these juvenile Chinook grew on average 0.23, 0.11-0.43 mm/d in the freshwater tidal estuary, similar to estimates in the brackish estuary, but ~4 times slower than those in the plume and upstream reservoirs. However, survival studies from the system elucidated a possible tradeoff between growth and survival in the Columbia River basin. These findings present a unique example of the complexity in understanding the influences of the many processes that generate variation in growth rate for juvenile anadromous fish inhabiting estuaries. In my second chapter, I used otolith microstructure and growth trends produced in a dynamic factor analysis (DFA, a multivariate time series method only recently being used in fisheries) to identify the life history variation in juvenile Chinook salmon caught in the Columbia River estuary over a two-year period (2010-2012). I used genetic assignment to stock of origin and capture location and date with growth trajectories, as a proxy for habitat transitions, to reconstruct life history types. DFA estimated four to five growth trends were present in juvenile Chinook salmon caught in the Columbia River estuary, diversity currently being simplified in many management practices. Regional stocks and habitats did not display divergent growth histories, but the marked hatchery fish did ordinate very similarly in the trend loadings from the DFA analysis, suggesting that hatchery fish may not experience the same breadth of growth variability as wild fish. I was not able to quantify juvenile life history diversity, and juvenile Chinook life history diversity remains difficult to catalog and integrate into species conservation and habitat restoration for resource management. However, by expanding our understanding of how juvenile Chinook salmon experience their freshwater rearing environment we improve our capacity to conserve and manage salmon populations. The findings from my thesis provide the necessary information for a restoration framework to link habitat features with salmon management goals, such as juvenile growth, wild and genetic origin and life history diversity.
