<p> Stocking of trout into naturally fishless water bodies in the mountains of western North America has reduced populations of many native species in those systems, with benthic aquatic invertebrates being particularly impacted. Although bats are known consumers of emergent aquatic insects, almost no studies have focused on how changes to these prey populations at lakes subsequent to trout stocking could affect them. This study assessed bat activity, foraging activity, and foraging rate at nine feature-matched pairs of stocked and unstocked high elevation lakes in the central Sierra Nevada mountains in an effort to determine which provide higher quality foraging habitat for bats. Bats in the 25 kHz and 50 kHz echolocation call categories showed little to no behavioral change between lakes with trout and lakes without. In contrast, bats in the 40 kHz group had higher levels of activity at stocked lakes, which may indicate that at those lakes bats are consuming numerous small insects. If this is the case, it could represent a cost to those bats due to the lower energetic return of small prey items compared to the preferred prey species. </p>

<p> Chinook salmon (<i>Oncorhynchus tshawytscha</i>) are critical to subsistence and commerce in the Yukon River basin, but several recent years of low abundance have forced devastating fishery closures and raised urgent questions about causes of the decline. The Chena River subpopulation in interior Alaska has experienced a decline similar to that of the broader population. To evaluate possible factors affecting Chena River Chinook salmon productivity, I analyzed both population data and the behavior of individual fish during the summer they spend as fry drift feeding in the river. Using a stereo pair of high definition video cameras, I recorded the fine-scale behavior of schools of juvenile Chinook salmon associated with woody debris along the margins of the Chena River. I developed a software program called VidSync that recorded 3-D measurements with sub-millimeter accuracy and provided a streamlined workflow for the measurement of several thousand 3-D points of behavioral data (Chapter 1). Juvenile Chinook salmon spent 91% of their foraging attempts investigating and rejecting debris rather than capturing prey, which affects their energy intake rate and makes foraging attempt rate an unreliable indicator of foraging success (Chapter 2). Even though Chinook salmon were schooling, some were highly territorial within their 3-D school configurations, and many others maintained exclusive space-use behaviors consistent with the population regulatory effects of territoriality observed in other salmonids (Chapter 3). Finally, a twenty-year population time series from the Chena River and neighboring Salcha River contained evidence for negative density dependence and a strong negative effect of sustained high summer stream discharge on productivity (Chapter 4). The observed territoriality may explain the population's density dependence, and the effect of debris on foraging efficiency represents one of many potential mechanisms behind the negative effect of high stream discharge. In combination, these findings contribute to a statistically and mechanistically plausible explanation for the recent decline in Chena River Chinook salmon. If they are, in fact, major causes of the decline (other causes cannot be ruled out), then we can be tentatively hopeful that the population may be experiencing a natural lull in abundance from which a recovery is possible. </p>

<p> People engaged in small-scale and commercial oyster aquaculture in Southern Maryland negotiate bundled regimes of value in creating a sense of locality through their interactions with oysters. These regimes of value are oysters as food, oysters as agents of ecological restoration, and oysters as a signifier of cultural heritage. The degree to which each regime is valued in relation to the others is highly variable between individuals and contexts. The sense of locality that they produce is constructed against the backdrop of perceived failures of government to adequately protect the resources of the Chesapeake Bay and the livelihoods that depend upon it. Oyster aquaculture has become seen as a way to sustainably revitalize Maryland's oyster industry while directly contributing to the restoration of the Chesapeake Bay's ecosystems. </p>

<p> The Nushagak River, Bristol Bay, Alaska, supports one of the largest wild sockeye salmon (<i>Oncorhynchus nerka</i>) runs in the state and also supports overlapping runs of chum (<i>O. keta</i>) and Chinook (<i>O. tshawytscha</i>) salmon. Each summer, the Alaska Department of Fish and Game deploys dual-frequency identification sonar (DIDSON) on the river to enumerate salmon to monitor escapement goals; however, salmon behavior and spawning run characteristics at the site are not incorporated into management. We investigated the feasibility of using Nushagak River DIDSON data from 2008-2011 to identify trends in run timing and compare passage rates to local environmental conditions, including tide, light intensity, and water temperature. We also used spatial analysis to examine aggregation behavior of salmon at the DIDSON site at multiple distance scales. Between all four years, run timing only varied within a few days (&lt; 1 week), regardless of water temperature. In 2009 and 2011, more salmon passed upriver during slack and ebb tides than during flood tide. Salmon were never completely spatially random, and distance scales of aggregation behavior were influenced by run period and photo period. When examining all factors together, the interaction between salmon density and run period affected distance at maximum aggregation. This research used hydroacoustics for a multi-level approach to investigating spatiotemporal patterns of Pacific salmon relative to environmental factors during their spawning migration and may help refine in-season monitoring and management of the fishery.</p>

Abstract not available.

Much remains unknown about the physiological effects of prolonged dietary carbohydrates on carnivorous fish such as rainbow trout, Oncorhynchus mykiss. In this thesis, the long-term effects of carbohydrates on trout glucose regulation are investigated by characterizing the metabolite profiles of fish fed with or without carbohydrates. Two groups of fish were maintained on either carbohydrate-rich (HC, 32.9% of diet by weight) or deficient (LC, 1% of diet by weight) diets for a six-month period. Plasma, liver and muscle tissue samples were assayed for various metabolites. Intravenous glucose tolerance tests were performed in each group and showed no significant differences in glucose tolerance. Continuous tracer infusion was used to measure glucose turnover in each group to determine whether changes in glucose concentration in response to a glucose load were due to changes in rates of glucose appearance (Ra), disappearance (Rd) or both. This research has demonstrated that rainbow trout can acclimate to high carbohydrate diets and modify several physiological parameters and biochemical pathways to both utilize and store newly available energy provided in the form of dietary glucose. (Abstract shortened by UMI.)

This paper presents a model for the evaluation of coastal zone sites in conjunction with supporting decision making on the use of potential sites for aquaculture as well as other site activities including commercial fisheries, and as reserves for natural resources. The decision support model captures site specific data in the form of a geographical information system that overlays selected geographical regions with natural resource dynamics, habitat, commercial activities including aquaculture, and influence plumes including toxicology. Descriptive data for selected regions including system overlays and interactions are then evaluated to provide input to a multicriteria analysis that positions decision makers with respect to the relative importance of resources, habitat, commercial activities, and influence plumes. The model compares alternative evaluations of selected regions among diverse users., as well as providing a group decision evaluation procedure to assist in coastal zonal governance decision makers such as the awarding of fish farm site applications. The model is applied to the coastal zone of Grand Manan Island, New Brunswick situated in the Bay of Fundy.

Attempts to use stable isotope carbon (delta13C) and nitrogen (delta15N) ratios to construct trophic positions and track mercury biomagnification in zooplankton and 13 fish species from a coastal food web of the Gulf of Oman illustrated some potential differences in this environment compared to the aquatic ecosystem of the northern hemisphere. Due to the large difference in delta13C values (3.4&permil;) between zooplankton planktivorous fish species (S. crumenophthalmus, S. longiceps and R. kanagurta), zooplankton would seem to not be the primary diet of these fish species as commonly described in literature. Total mercury (T-Hg) concentrations of zooplankton were very low (range 0.010 to 0.037 mug&middot;g-1, N = 27) with a mean methyl mercury (MeHg) of 0.001 mug&middot;g-1 (range 1-19%, N = 5). The lowest T-Hg (0.003 mug&middot;g-1) was found in planktivore (S. longiceps) and the highest was 0.760 mug&middot;g -1 in predator shark (R. acutus) with average MeHg for all fish of 72% (range: 33-100%, N = 150). Using 15 N as indicator of trophic position, neither total mercury (T-Hg) nor methyl mercury (MeHg) were found to biomagnify. Regression slopes were 0.08 and 0.05 for T-Hg and MeHg respectively as a function of delta15 N. This indicates that biomagnification was lower in this tropical ocean compared to that found in freshwater and marine ecosystems of the arctic and temperate zones. Methyl mercury levels in the fish species commonly consumed are low and intake calculations showed that individuals can safely consume fish.

The mineralocorticoid receptor (MR) was recently cloned from two fish species, Haplochromis burtoni (H. burtoni; hbMR) and rainbow trout (Oncorhynchus mykiss; rtMR). The objectives of the present study were to detect MR protein expression in rainbow trout ionoregulatory tissues, namely the gill and kidney, as well as to use the mammalian MR agonist aldosterone to selectively target and activate the rainbow trout MR to observe its effects on renal and branchial ionic regulation. Through immunohistochemistry and Western blot analysis using a heterologous antibody, MR protein expression was detected at the gill. Immunohistochemical analysis and flow cytometry data indicated that there was a high degree of colocalization of the rtMR to Na+-K+-ATPase rich cells at the gill, supporting the hypothesis that the rtMR is involved in branchial ionic regulation. Additionally, acute aldosterone treatment, but not cortisol treatment, stimulated a decrease in urine flow rate (UFR) and urinary sodium excretion at 1.5 h post-injection. The decrease in UFR occurred without any change in glomerular filtration rate (GFR), suggesting that the aldosterone-induced decrease in UFR was the result of increased tubular reabsorption of water, which in turn was presumably stimulated by enhanced Na+ reabsorption. The results of this study support the hypothesis that the rtMR is involved in renal and branchial ionic regulation and help to clarify the mechanisms through which corticosteroid-mediated ionic regulation occurs in euryhaline teleosts.

alpha1-Adrenoceptors (alpha1-ARs) are members of the G-protein coupled receptor superfamily of membrane proteins that mediate the actions of the endogenous catecholamines, adrenaline and noradrenaline. alpha 1-ARs are the prime mediators of vascular smooth muscle contraction and hypertrophic growth, and play a key role in the regulation of arterial blood pressure. Four weeks of high-salt diet (11% NaCl) significantly increased blood pressure (37.1%). An average two-fold decrease in alpha1D-AR mRNA expression was observed in the DA, ABA and EBA in high-salt diet fed trout. The chronically hypertensive fish exhibited a blunted vascular response to hypercapnia and exogenous catecholamines. These results suggest either a lowered vascular response capacity or that alpha1D-AR down-regulation occurred in high-salt diet fed fish as a consequence of the elevated blood pressure. The alpha1D-AR is, at least in part, involved in salt-induced high blood pressure in rainbow trout. This study is the first to characterize the alpha1-AR gene family at molecular level in any fish species, and provides the first evidence for a link between alpha1-ARs and salt-induced high blood pressure.