A two year study was initiated in 1973 to examine effects of substantial (3.8 fold; from a 1962-66 mean of 39 million to about 150 million in 1973 and 1974) increases in sockeye (Oncorhynchus nerka) Walbaum) fry numbers on zooplankton abundance in Babine Lake. Several lake areas and stationsware sampled for zooplankton bimonthly from May to October during 1973 and 1974 and compared to data gathered between 1958 and 1962 prior to a large scale enhancement program for sockeye stocks. Zooplankton biomass had decreased up to 70% in some areas of the lake during 1973, but only 40% in 1974. Decreases in numbers were also evident. Although seasonal changes in fry diet followed changes in zooplankton species abundance, feeding was selective. The less abundant but larger forms, Daphnia and Heterocope together comprised 70% of the diet during summer, while Cyclops and Diaptomus formed the bulk (87%) of the diet in late fall. Significant decreases in Daphnia and Diaptomus abundance and increases in nauplii-early copepodite abundance had occurred by 1973. The increased 1974 zooplankton abundance relative to 1973 was attributed to decreased mid-summer fry numbers in the lake. Field data suggested low Diaptomus numbers contributed to much higher fry mortality (about double in 1974) compared to 1973. An experimental study of species selectivity by sockeye fry indicated that they selected Cyclops and Diaptomus adults. The larger copepods, Heterocope and Epischura, were rejected by fry encountering zooplankton for the first time. Copepodites and nauplii were rejected, but less so when preferred prey were scarce. Prey activity, in my experiments, could not be used to predict predation vulnerability and hence the species selectivity displayed by the fry. Light and temperature had little effect on Cyclops, Dlaptomus and Heterocope activity. / Science, Faculty of / Zoology, Department of / Graduate

This study was conducted to satisfy three objectives. The first was to provide a detailed description of the differences between the prey contents of rainbow trout (Salmo qairdneri) and kokanee (Oncorhynchus nerka) compared either to each other or to the prey contents of the natural environment. The second was to determine how elements of anatomy, physiology and behaviour interact to promote the acquisition of species specific diets by trout and kokanee. The third was to precisely identify the foraging strategies of the two predators by assessing how different anatomical and behavioural characteristics serve as interrelated adaptations that suit each species to effectively use a specific habitat-prey complex. Matched samples of trout and kokanee from Marion Lake exhibit only modest A dietary overlap (mean of C λ = .462, range.136 to .881). Although kokanee appear to track the environmental abundance of prey more closely than trout, both predators exhibit pronounced patterns of "density independent" acquisition of prey from the total complex of prey that is apparently available in the lake. To test hypotheses about the factors that control these dietary patterns, I conducted a series of studies concerning where trout and kokanee choose to forage, when they choose to forage, how they search for prey, how they attack prey, and how experience in encountering various prey alters the predator's foraging behaviour. Temporal segregation of trout and kokanee foraging activities is not well-developed under field conditions and appears unlikely to promote strong patterns of food-resource partitioning. By contrast, spatial segregation is well-developed and clearly plays a major role in promoting the acquisition of relatively large numbers of nearshore benthic prey ( eg. planorbid snails or odonates ) by trout and of relatively large numbers of offshore, water-column prey ( eg. chironomid pupae ) by kokanee. Close inspection of the details of predator and prey distributions indicates that many aspects of food-resource partitioning are not logical outcomes of spatial segregation. Differences in predator search-techniques do not determine the presence or absence of various prey types in predator diets, however, differences in predator search behaviours do bias them to obtain different quantities of particular classes of prey. Kokanee search procedures allow them to detect prey in both exposed and concealed locations while trout detect only exposed prey. While searching for benthic or lake-surface prey, kokanee maintain search positions which allow them to detect prey of smaller sizes than trout. This clearly favours the trend for kokanee to include greater quantities of small prey (eg. Hyalella sp.) in their diets than trout. Differences in search procedures do not explain why kokanee obtain a greater proportion of their diet than trout from small zooplankton (≤ 1 mm ) in late summer or why kokanee seldom exploit any of the relatively large ( > 4 mm ), armoured prey that are common in the diet of similar sized trout. Differences in both behavioural and morphological characteristics involved in the attack phase of foraging by trout and kokanee serve as the basis for explanations of a number of differences between the diets of free-ranging predators. These differences include: the greater utilization of aerial prey by trout, the inclusion of large numbers of copepods in the diet of kokanee but not of trout, the generally greater utilization of zooplankton by kokanee compared to trout, and the relative-scarcity of large ( > 4 mm ), armoured prey, in the diet of kokanee. A series of laboratory experiments was used to examine the extent to which short term experience might influence food-resource partitioning by trout and kokanee. These experiments offered convincing evidence that differential effects of experience will amplify the trends in resource partitioning already set in motion by differences in habitat selection, search procedures, and attack procedures. I argue that the morphological and behavioural traits that control food "selection" by trout and kokanee in Marion Lake are a consequence of the evolution of mutually exclusive foraging strategies. Trout are portrayed as D-strategists that concentrate on relatively large, dispersed prey for the bulk of their energy requirements. Adaptations which enable trout to differentially exploit large prey include: procedures for area-extensive search; a predisposition to attack relatively large, armoured-prey; large mouth-size; and persistent responses to opportunities to attack large prey. An inability to sustain high attack rates on small prey ( < 1 mm ) at high density ( 35 per liter ) and a tendency to ignore or reject such prey suggest that trout are not well-adapted to exploit relatively small, morphologically-uniform,prey. Kokanee are portrayed as C-strategists which concentrate on relatively small, contagiously-distributed prey for the bulk of their energy requirements. Adaptations which enable kokanee to differentially exploit small prey include: procedures for area-intensive search; a predisposition to attack relatively small, morphologically-uniform prey; small mouth-size; well-developed gill-rakers; and an ability to sustain high attack rates on small planktonic prey. Low ingestion success with a variety of large benthic prey and a tendency to ignore or reject such prey under laboratory conditions where they serve as the sole source of food are evidence that kokanee are not well adapted to exploit large, armoured-prey. Adaptations associated with the search, capture, manipulation and ingestion phases of the foraging cycle appear in each instance to be evolutionary responses to specific features of a given habitat-prey complex. C-selected or D-selected foraging strategies appear to be mutually exclusive evolutionary avenues down which trout and kokanee have been directed by the fundamental nature of a given habitat-prey complex. / Science, Faculty of / Zoology, Department of / Graduate

In many rivers, dams have interrupted the connectivity of migration routes for fish. While fishways can provide access between downstream and upstream habitats, it is important that passage can occur with minimal delay, energy expenditure, and physiological stress. The research presented here is based on investigations into fishway attraction and passage for the Gates Creek sockeye salmon (Oncorhynchus nerka, Walbaum) stock at the Seton River dam in British Columbia. The first part of this thesis examined the effect of changes in water discharge from the dam on the relationship between the physiological condition of sockeye and their behaviour in approaching the fishway entrance. Fish were caught and non-lethally biopsied under three normal operating discharge conditions at Seton River dam, and subsets of sampled fish were implanted with radio transmitters and released downstream of the dam. Indices of physiological stress and exhaustive exercise (e.g. plasma cortisol, glucose, lactate, osmolality and hematocrit) did not differ among the water discharge levels that were examined. Fish delayed in the tailrace below the fishway entrance significantly longer under intermediate discharge (19.9 h @ 12.7 m³s‾¹) than either the high discharge (9.3 h @ 15.8 m³s‾¹), or the low discharge (7.0 h @11.0 m³s‾¹;) conditions (P = 0.022, and P = 0.015, respectively). Delay time was similar under high and low discharge conditions (P = 0.617), and passage success was found to be independent of discharge (P = 0.356). The second part of this thesis investigated how prior physiological condition and subsequent swimming energetics and behaviours effected fishway passage success. Fish were captured and biopsied, before being implanted with electromyogram (EMG) transmitters and released near the downstream entrance of the fishway. Very few differences existed between successful and unsuccessful fish in body size, initial plasma physiology and energy state, and mean swim speed and energy use during passage. However, plasma Na+ concentration was significantly lower in unsuccessful fish (P = 0.022), which is suggestive of a depressed ionic state for unsuccessful fish. Generally, fish did not employ burst swimming during successful or failed attempts at passage, indicating that failure was probably not related to metabolic acidosis.

Recent advances in otolith microchemistry have established that trace element composition can be used to chemically reconstruct fish life history and serve as a stock identification tool. In modern fisheries practices, these two applications are especially pertinent to wild salmon populations, which are difficult to track over large spatial scales and nearly impossible to identify in mixed populations. This project has applied a novel method using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to anadromous sockeye salmon (Oncorhynchus nerka) otoliths from four separate watersheds in Sitka, Alaska. Spatial distributions of Li, Mg, Mn, Zn, Sr, and Ba were determined via continuous lateral ablation scans across the diameter of transversely sectioned sagittal otoliths. Time-series data generated from line scan analysis were used to chemically reconstruct sockeye life history, and examine elemental signatures in the core, freshwater, and marine growth regions of otoliths for stock identification purposes. Chemical profiles of life history showed that Sr, Ba, and to a lesser degree Mg, reflected ambient chemistry, and were effective for tracking sockeye migration from fresh to marine water. Manganese was also effective for determining migration to fresh and marine water; however, it is believed that diet more than ambient chemistry is the factor controlling uptake. Elements such as Zn and Li provided information related to fish physiology, such as growth and changes in osmoregulation during transitions from low to high salinity environments. Results also showed that several elements were either enriched or depleted in the core of sockeye otoliths. Maternal investments and spatial differences in crystal structure are believed to significantly affect element uptake in otoliths during incubation and early development. Elemental signatures in the otolith core may therefore be inaccurate as an indicator of stock origin. This problem was investigated by isolating core, freshwater, and marine signatures and evaluating individually their ability to correctly classify sockeye otoliths to their natal watersheds using step-wise discriminant function analysis. This demonstrated that freshwater signatures provided the greatest accuracy (91%) for stock ID. Core signatures, which have been used in past stock ID studies, showed poor classification results (68%) for sockeye salmon otoliths. Trace element signatures from the marine growth regions of sockeye otoliths displayed the poorest classification accuracy (52.5%) of the three growth regions. Thus, freshwater signatures are the most effective tool for identifying the origin of wild salmon, even when they far removed from their natal watersheds.

In many rivers, dams have interrupted the connectivity of migration routes for fish. While fishways can provide access between downstream and upstream habitats, it is important that passage can occur with minimal delay, energy expenditure, and physiological stress. The research presented here is based on investigations into fishway attraction and passage for the Gates Creek sockeye salmon (Oncorhynchus nerka, Walbaum) stock at the Seton River dam in British Columbia. The first part of this thesis examined the effect of changes in water discharge from the dam on the relationship between the physiological condition of sockeye and their behaviour in approaching the fishway entrance. Fish were caught and non-lethally biopsied under three normal operating discharge conditions at Seton River dam, and subsets of sampled fish were implanted with radio transmitters and released downstream of the dam. Indices of physiological stress and exhaustive exercise (e.g. plasma cortisol, glucose, lactate, osmolality and hematocrit) did not differ among the water discharge levels that were examined. Fish delayed in the tailrace below the fishway entrance significantly longer under intermediate discharge (19.9 h @ 12.7 m³s‾¹) than either the high discharge (9.3 h @ 15.8 m³s‾¹), or the low discharge (7.0 h @11.0 m³s‾¹;) conditions (P = 0.022, and P = 0.015, respectively). Delay time was similar under high and low discharge conditions (P = 0.617), and passage success was found to be independent of discharge (P = 0.356). The second part of this thesis investigated how prior physiological condition and subsequent swimming energetics and behaviours effected fishway passage success. Fish were captured and biopsied, before being implanted with electromyogram (EMG) transmitters and released near the downstream entrance of the fishway. Very few differences existed between successful and unsuccessful fish in body size, initial plasma physiology and energy state, and mean swim speed and energy use during passage. However, plasma Na+ concentration was significantly lower in unsuccessful fish (P = 0.022), which is suggestive of a depressed ionic state for unsuccessful fish. Generally, fish did not employ burst swimming during successful or failed attempts at passage, indicating that failure was probably not related to metabolic acidosis.

Thesis (M.E.S.)--Evergreen State College, 2008. / "June, 2008." Title from title screen (viewed 4/8/2010). Includes bibliographical references.

In many rivers, dams have interrupted the connectivity of migration routes for fish. While fishways can provide access between downstream and upstream habitats, it is important that passage can occur with minimal delay, energy expenditure, and physiological stress. The research presented here is based on investigations into fishway attraction and passage for the Gates Creek sockeye salmon (Oncorhynchus nerka, Walbaum) stock at the Seton River dam in British Columbia. The first part of this thesis examined the effect of changes in water discharge from the dam on the relationship between the physiological condition of sockeye and their behaviour in approaching the fishway entrance. Fish were caught and non-lethally biopsied under three normal operating discharge conditions at Seton River dam, and subsets of sampled fish were implanted with radio transmitters and released downstream of the dam. Indices of physiological stress and exhaustive exercise (e.g. plasma cortisol, glucose, lactate, osmolality and hematocrit) did not differ among the water discharge levels that were examined. Fish delayed in the tailrace below the fishway entrance significantly longer under intermediate discharge (19.9 h @ 12.7 m³s‾¹) than either the high discharge (9.3 h @ 15.8 m³s‾¹), or the low discharge (7.0 h @11.0 m³s‾¹;) conditions (P = 0.022, and P = 0.015, respectively). Delay time was similar under high and low discharge conditions (P = 0.617), and passage success was found to be independent of discharge (P = 0.356). The second part of this thesis investigated how prior physiological condition and subsequent swimming energetics and behaviours effected fishway passage success. Fish were captured and biopsied, before being implanted with electromyogram (EMG) transmitters and released near the downstream entrance of the fishway. Very few differences existed between successful and unsuccessful fish in body size, initial plasma physiology and energy state, and mean swim speed and energy use during passage. However, plasma Na+ concentration was significantly lower in unsuccessful fish (P = 0.022), which is suggestive of a depressed ionic state for unsuccessful fish. Generally, fish did not employ burst swimming during successful or failed attempts at passage, indicating that failure was probably not related to metabolic acidosis. / Forestry, Faculty of / Graduate