Variability in the Energy Density of Prey and Its Consequences for Growth in Juvenile Chinook Salmon PDF Download

Author: Jacob Daniel Cole Weil
Publisher:
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Category :
Languages : en
Pages :

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Understanding how energy flows through ecosystems reveals underlying ecological patterns that can drive processes such as growth and survival of organisms. To understand how energy is transferred through organisms, the energy content or energy density (ED) of both consumers and prey must be determined. To facilitate the ease of ED measurement across taxa, I developed a model to estimate the ED of organisms using percent ash-free dry weight (AFDW). Using data obtained from 11 studies with broad taxonomic, temporal and spatial coverage, I compared common predictors of ED using linear models. AFDW was determined to be the superior predictor of ED relative to previous metrics and was predictive for a broad range of taxonomic groups including aquatic invertebrates, aquatic vertebrates, aquatic plants and terrestrial invertebrates. This AFDW model enables measurement of ED with minimal cost and time investment, which allows ED to be more readily determined for diverse taxa. Next, I applied the AFDW method to the diet of a pelagic consumer, juvenile Chinook Salmon, to determine the effect of variable prey ED on growth. In 2017, I collected monthly zooplankton and fish samples of known importance in the diet of juvenile Chinook Salmon to look for fine-scale taxonomic, temporal and spatial differences in ED. Decapod zoeae and megalopae differed significantly from each other and showed family level variability in ED. Amphipods also showed significant species-level variability in ED. Temporal differences were observed, but did not reveal a consistent pattern among groups. Spatial variability was not significant. Using bioenergetics models, growth of juvenile Chinook Salmon was predicted to be greater when using fine-scale ED estimates. This difference was not substantial on average, but in some cases represented more than a two-fold difference in growth between coarse- and fine-scale estimates. These results suggest the need for higher resolution diet ED data when determining growth projections for juvenile Chinook Salmon. With the aid of the AFDW model presented in this thesis, the effort required to obtain these data is greatly reduced.

Author: Marisa Norma Chantal Litz
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 203

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The early marine phase following freshwater emigration has been identified as a critical period in salmonid (Oncorhynchus spp.) life history, characterized by high but variable mortality. Consistent with the “growth-mortality” and “bigger-is-better” hypotheses, at least some of the mortality during the critical period appears to be size-dependent – with smaller or slower growing individuals less likely to survive than larger, faster growing conspecifics. Size and growth are flexible morphological traits that vary with prey availability, yet there is incomplete information on the temporal and spatial match/mismatch between juvenile salmonids and their marine prey in the Northern California Current Ecosystem. This work addressed a gap in the understanding of seasonal variability in prey community composition, abundance, and quality during early marine residence. Three studies were conducted using a population of subyearling (age-0) Chinook salmon (O. tshawytscha) from the upper Columbia River in order to evaluate the effects of prey on salmon growth, biochemistry, and performance. The first was a laboratory study that tested for growth rate and swimming speed differences in salmon reared on three treatment diets followed by three fasting treatments to assess the effects of variability in summer diet quality and winter diet quantity. Significant differences in growth were detected among fasting treatments but not diet treatments. Also, larger salmon with more storage lipids swam faster than smaller leaner fish following fasting, indirectly supporting the notion that growth during the critical period provides a carryover benefit important for overwinter survival. Salmon fatty acids and bulk stable isotopes of carbon and nitrogen were measured throughout the experiment to provide estimates of turnover and incorporation rates. The next study was a longitudinal field study that measured variation in salmon size and prey field community throughout the early ocean period (May – September) over two years of high marine survival (2011 and 2012) to better understand the relationship between prey community composition and salmon growth. Maximum growth rates were associated with high biomass of northern anchovy (Engraulis mordax) which peaked in abundance at different times in each year. The final bioenergetics modeling study combined data from the laboratory and field studies to evaluate the relative importance of prey availability, prey energy density, and temperature on salmon growth. Variation in feeding rate was related most with growth rate variability and least with prey energy density. Throughout their range, subyearlings can grow at high rates in the ocean (>2% body weight per day) by consuming both invertebrate and marine fish prey. However, when marine fish prey are highly abundant they likely provide an energetic advantage over invertebrate prey by reducing overall foraging costs. Quantifying the abundance, size, diet, and distribution of juvenile salmonids relative to their prey field throughout early ocean residence will contribute to a better understanding of seasonal differences in trophic interactions that are associated with differences in annual growth and survival rates. Moreover, an integrated approach that combines sampling of prey with measurements of predator growth, diet, fatty acids, and stable isotopes provides a useful framework for assessing trophic dynamics and evaluating the effects of climate variability and change on predator and prey communities.

Author: Aaron David
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 105

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During the transition of juveniles from fresh water to estuarine and coastal environments, the survival of Pacific salmon (Oncorhynchus spp.) can be strongly size-selective and cohort abundance is partly determined. Because the quantity and quality of food consumed influence juvenile salmon growth, high rates of prey and energy acquisition during estuarine residence are important for survival. Human activities may have affected the foraging performance of juvenile salmon in estuaries by reducing the area of wetlands and by altering the abundance of conspecifics. To improve our understanding of the effects of wetland loss and conspecific density on juvenile salmon foraging performance and diet composition in estuaries, I assembled Chinook salmon (O. tshawytscha) diet and density data from nine U.S. Pacific Northwest estuaries across a gradient of wetland loss. We evaluated the influence of wetland loss and conspecific density on juvenile Chinook salmon instantaneous ration and energy ration, two measures of foraging performance, and whether the effect of density varied among estuaries with different levels of wetland loss. We also assessed the influence of wetland loss and three other covariates on salmon diet composition. There was no evidence of a direct effect of wetland loss on juvenile salmon foraging performance, but wetland loss mediated the effect of conspecific density on salmon foraging performance and altered salmon diet composition. These results suggest that habitat loss can interact with conspecific density to constrain the foraging performance of juvenile fishes, and ultimately their growth, during a life-history stage when survival is positively correlated with growth and size. I also evaluated whether restoring tidal flow to previously diked estuarine wetlands also restores foraging and growth opportunities for juvenile Chinook salmon. Several studies have assessed the value of restored tidal wetlands for juvenile salmon, but few have used integrative measures of salmon physiological performance, such as habitat-specific growth potential, to evaluate restoration. Our study took place in the Nisqually River delta, where recent dike removals restored tidal flow to 364 ha of marsh, the largest tidal marsh restoration in the Pacific Northwest. To compare Chinook salmon foraging performance and growth potential in two restored and two reference marshes over three years post-restoration, we sampled fish assemblages, water temperatures, and juvenile Chinook salmon diet composition and consumption rates, and used these data as inputs to a bioenergetics model. We found that juvenile Chinook salmon foraging performance and growth potential were similar between the restored and reference marshes. However, densities of Chinook salmon were significantly lower in the restored marshes and growth potential was more variable in the restored marshes due to their more variable and warmer (2?? C) water temperatures compared to the reference marshes. These results indicate that some but not all ecosystem attributes that are important to juvenile salmon rapidly recover following large-scale tidal marsh restoration.

Author: Melanie Jeanne Davis
Publisher:
ISBN:
Category :
Languages : en
Pages : 228

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A complex mosaic of estuarine habitats is postulated to bolster the growth and survival of juvenile Chinook salmon by diversifying the availability and configuration of prey and refugia. Consequently, efforts are underway along the North American Pacific Coast to return modified coastal ecosystems to historical or near-historical conditions, but restoring habitats are often more sensitive to anthropogenic or climate-mediated disturbance than relict (unaltered) habitats. Estuaries are expected to experience longer inundation durations as sea-levels rise, leading to reductions in intertidal emergent marshes, mudflats, and eelgrass beds. Furthermore, rising ocean temperatures may have metabolic consequences for fall-run populations of Chinook salmon, which tend to out-migrate during the spring and summer. Extensive monitoring programs have allowed managers to assess the initial benefits of management efforts (including restoration) for juvenile salmon at local and regional scales, but at present they have limited options for predicting and responding to the concurrent effects of climate change in restoring and relict coastal ecosystems. For my dissertation I addressed this gap in knowledge using a comprehensive monitoring dataset from the restoring Nisqually River Delta in southern Puget Sound, Washington. I focused on the following questions: 1) How do juvenile Chinook salmon prey consumption and dietary energy density vary throughout a mosaic of estuarine habitats, and is this variation related to differences in physiological condition? 2) How do among-habitat differences in thermal regime and prey consumption affect the bioenergetic growth potential of juvenile Chinook salmon? 3) How will shifts in the estuarine habitat mosaic vary under different sea-level rise and management scenarios? and 4) How will these climate- and management-mediated shifts in the estuarine habitat mosaic impact habitat quality for juvenile Chinook salmon? To address the first question, I used stomach content and stable isotope analyses to analyze the diets of wild and hatchery Chinook salmon captured in different estuarine habitats during the out-migration season (March-July of 2014 and 2015). I also linked measures of stomach fullness and dietary energy density to body condition. To address the second question, I used a bioenergetics model to determine how among-habitat differences in water temperature and diet might affect juvenile Chinook salmon growth. To address the third question, I designed and calibrated a marsh accretion model and decision support tool using post-restoration monitoring data sets and spatial coverages. Finally, to address the fourth question, I combined output from the marsh accretion model, a hydrological model, and measurements of prey availability into a spatially explicit version of the bioenergetics model to assess the habitat quality and growth rate potential of the entire estuarine habitat mosaic under different sea-level rise and management scenarios. When considered in tandem, these chapters represent a novel approach to habitat management. Assessments of juvenile salmon diet and physiology, marsh accretion models, and bioenergetics models have been independently implemented along the Pacific Coast, but the amalgamation of all three approaches into a single, spatially explicit analysis represents a novel and significant contribution to the scientific literature. In conducting these analyses for the Nisqually River Delta, some major themes emerged regarding the importance and vulnerability of specific habitats. An integrative diet analysis using stomach contents and stable isotopes found distinct dietary niches between wild and hatchery Chinook salmon. Wild fish were more likely to utilize the freshwater tidal forested and transitional brackish marsh habitats along the main stem river, where energy-rich insect drift made up most of their dietary biomass. The availability and consumption of insect prey resulted in distinct benefits to body condition and growth, as determined by direct physiological measurements and output from the habitat-specific bioenergetics model. These findings highlight the importance of freshwater and brackish emergent marsh habitats with overhanging vegetation, which can regulate water temperatures and supply insect drift. Unfortunately, freshwater tidal forests, brackish marshes, and low and high elevation emergent salt marshes are highly vulnerable to sea-level rise, especially when geological and anthropogenic features limit sediment accretion or lateral expansion. When spatial layers from the marsh accretion model were incorporated into the spatially explicit version of the bioenergetics model, output indicated that loss of low and high salt marsh reduced the amount of prey available for juvenile salmon, thus decreasing modeled growth rate potential. In all, these findings highlight the importance of preserving the estuarine habitat mosaic for out-migrating juvenile salmon, especially as tidal regimes and ocean temperatures continue to shift through time.

Author: Sean Eugene Burril
Publisher:
ISBN:
Category : Chum salmon
Languages : en
Pages : 152

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"Juvenile chum salmon from Kuskokwim Bay were sampled for patterns in diet and energy density in 2003 and 2004. Comparisons were made interannually, seasonally, between juvenile size classes, and between sailinity ranges. Sampling was conducted using a modified Kvichak Trawl. Bomb calorimetry was used to obtain energy density values. Feeding success and feeding intensity increased with fish size and season, and was highest in waters with moderate salinity. Feeding success and intensity were lowest for smaller juvenile chum salmon collected early in the season in water with low salinity. Prey composition was similar in both years, but varied with fish size, salinity ranges, and sampling weeks. Calanoid copepods and insects combined made up >50% of all prey items consumed and >80% of the overall prey biomass for all size classes, salinity ranges, and weeks. Feeding by juvenile chum salmon in Kuskokwim Bay appeared to be opportunistic. In 2003, no significant differences in energy density were found. In 2004, energy density decreased significantly from mid-May to mid-June and with increasing fish size. Decreasing energy density with season and size suggests that juvenile chum salmon were allocating the majority of their energy towards growth and smoltification, rather than lipid storage. Results from this study indicate that Kuskokwim bay may provide a suboptimal estuarine rearing habitat for juvenile chum salmon. If seasonally increasing energy demands are not balanced by an increasing food supply, the severe implications potentially include declines in growth rates and possibly overall survival probability of chum salmon juveniles in Kuskokwim Bay"--Leaf iii.

Author: A.T. Riddick
Publisher: Geological Society of London
ISBN: 1862396876
Category : Science
Languages : en
Pages : 274

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The discipline of Integrated Environmental Modelling (IEM) has developed in order to solve complex environmental problems, for example understanding the impacts of climate change on the physical environment. IEM provides methods to fuse or link models together, this in turn requires facilities to make models discoverable and also to make the outputs of modelling easily visualized. The vision and challenges for IEM going forward are summarized by leading proponents. Several case studies describe the application of model fusion to a range of real-world problems including integrating groundwater and recharge models within the UK Environment Agency, and the development of ‘catastrophe’ models to predict better the impact of natural hazards. Communicating modelling results to end users who are often not specialist modellers is also an emerging area of research addressed within the volume. Also included are papers that highlight current developments of the technology platforms underpinning model fusion.

Author: Katherine Rose Middleton
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Evidence suggests that the variability in recruitment of adult Pacific salmon is related to smolt survival during the first ocean year. Specifically, the first few weeks and first marine winter may be two critical periods of high mortality during early marine life. Mortality during early marine residency has been attributed to predation and size-dependent factors while high mortality during the first winter may be due to energy deficits and failure to reach a certain size by the end of the growing season. My study assessed factors influencing overwinter mortality and early marine growth in juvenile Chinook salmon (Oncorhynchus tshawytscha) from Marble River, Quatsino Sound, British Columbia. Juvenile salmon were collected during November 2005 and 2006 (fall) and March 2006 and 2007(winter). Mortality rates over the first winter derived from catch per unit effort across seasons ranged between 80-90% in all years. These are the first estimations of overwinter mortality in juvenile Pacific salmon. Fish size distributions showed no evidence of size-selective overwinter mortality between fall and winter fish in either 2005-2006 or 2006-2007. Otolith microstructure analyses showed no significant difference in circulus increment widths during the first four weeks after marine entry. Similarities in increment width indicated that early marine growth did not differ between fall and winter fish during early marine residency in 2006. These observations show that the high overwinter mortality rates of juvenile Chinook salmon in Quatsino Sound are not size-dependent. Total plankton biomass was significantly lower in the winter season but size distribution, gut fullness and energy density data did not show evidence of starvation. No correlation was found between early marine growth, size, energy accumulation and high mortality in Marble River juvenile Chinook salmon during their first ocean winter in Quatsino Sound. Possible factors influencing these high mortality rates may include non size-selective predation, disease, local environmental influences or an as yet unknown source. Future work should continue to focus on understanding the relationship between early marine survival and adult recruitment. The expansion of growth comparisons geographically and chronologically while determining the effects of predatory mortality on juvenile Chinook salmon along the north Pacific continental shelf and beyond are imperative to fully understanding this complex marine life stage.

Author: Crystal R. Hackmann
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 184

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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: Alisa J. Bieber
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 208

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Author: William Duguid
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Fisheries oceanography often aims to link large scale atmospheric and oceanic processes to variability and trends in the productivity of economically and ecologically valuable fish species. Declines in productivity of multiple species of Pacific Salmon (genus Oncorhynchus) in recent decades have spurred the search for a 'smoking gun;' an explanation that could explain trends in productivity across populations, regions and species. Despite extensive investment of research effort and funding, such an explanation remains elusive. The lack of a unifying explanation for declining productivity of Pacific Salmon may be due to the spatial and temporal complexity of their interactions with the marine environment. This complexity has historically been understudied, in part due to logistical limitations of research on Pacific Salmon at sea. This dissertation reports the results of a detailed study of how juvenile Chinook Salmon O. tshawytscha interact with marine habitats during their first summer and fall at sea. I first developed and validated a novel, hook and line-based method of sampling juvenile Chinook Salmon (microtrolling). I then reviewed and empirically compared methods (insulin like growth factor-1 concentration, RNA to DNA ratio, and scale circulus spacing) for indexing growth rate of juvenile salmon sampled in the ocean, a variable which is hypothesized to be related to subsequent survival. I integrated microtrolling with small vessel oceanography to relate distribution, diet, size and growth of juvenile Chinook Salmon to local scale variation in water column properties (stratification) and zooplankton community composition and abundance for five sites in the Southern Gulf Islands of the Salish Sea during a single summer (2015). While both stratification and zooplankton abundance and composition varied between sites, I failed to find support for the hypothesis that juvenile salmon distribution and growth was positively related to water column stratification at fine spatial scales. Juvenile Chinook Salmon were larger and faster growing where juvenile Pacific Herring Clupea pallasii were important in their diets, suggesting that Pacific Herring may play an important role in structuring the ecology of juvenile Chinook Salmon at sea. I built on 2015 results to conduct a detailed case study of juvenile Chinook Salmon ecology at two sites in the Southern Gulf Islands: Sansum Narrows and Maple Bay. Juvenile Chinook Salmon were consistently larger, more piscivorous, and faster growing at Sansum Narrows than Maple Bay across two years (2015 and 2016) despite lower zooplankton abundance at Sansum Narrows. Hydroacoustic surveys in September 2017 confirmed prior qualitative observations of elevated occurrence of forage fish schools (likely age-0 Pacific Herring) at Sansum Narrows, and a novel, mobile acoustic tag tracking survey suggested that fish tagged at Sansum Narrows may co-locate with juvenile Pacific Herring over the tidal cycle. By relating a scale circulus spacing-based growth index to reconstructed size intervals I found that juvenile Chinook Salmon at Sansum Narrows had been faster growing that those at Maple Bay before the transition to piscivory, and perhaps before migration to the ocean. These results suggest that intrinsic growth potential, or growth conditions during freshwater rearing or the transition to marine residence, interact with fine-scale structure in marine habitats to regulate growth potential of juvenile Chinook Salmon at sea. These factors also likely interact with the basin and interannual scale processes that have received extensive study as regulators of marine survival of juvenile Pacific salmon. These complex interactions should be taken into account when designing or interpreting studies to determine factors limiting productivity of Pacific Salmon populations.