Browsing University of Alaska Fairbanks by Subject "Fishes"
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Feeding and growth of seasonal cohorts of larval walleye pollock (Theragra chalcogramma) in Auke Bay, AlaskaLarval walleye pollock, Theragra chalcogramma (Pallas), typically occur in the water column in synchrony with peak densities of prey. A primary objective of this investigation was to examine and compare growth rates of larval pollock. The growth rate of a synchronous cohort (hatched 10-14 May, 1986) was found to be significantly higher (P<0.05) than that of an earlier cohort (hatched 15-19 April, 1986) . Synchronous cohorts are larvae that occur simultaneously with the maximum densities of herbivorous copepods. Growth rates were determined by otolith analysis. Prey densities and water temperature were implicated as causes of the observed differences in growth. Prey densities were approximately 3 times higher for the synchronous cohort than the early cohort. Additionally, the early cohort experienced water temperatures 2-3°C colder than the synchronous cohort. Results suggest that synchronous larval walleye pollock have higher growth rates and may have higher survival rates.
The feeding ecology of chum salmon fry (Oncorhynchus keta) in northern Prince William Sound, AlaskaA two year study of the feeding ecology of early outmigrating chum salmon fry, Oncorhynchus keta, in northern Prince William Sound, Alaska, demonstrated harpacticoid copepods and chironomid insects to be dominant food taxa with calanoid copepods, polychaete larvae, cladocerans and cirripeds also contributing. Examination of the IRI (Index of Relative Importance) values for harpacticoids and insects revealed fluctuating seasonal patterns. Low IRI values for harpacticoids and/or insects coincided with higher IRI values for calanoids, polychaetes, cladocerans and cirripeds. ANOVA analyses and t-tests results on stomach contents demonstrated spatiotemporal variations in diet. Early outmigrating chum fry inhabited tidal mudflats, rocky beaches and vertical rocky outcrops where harpacticoids and insects were prevalent. CTD data and plankton tows indicated that tidal advection supplied pelagic prey from Unakwik Inlet to Jonah Bay. Fluctuating IRI values by prey taxa suggest an opportunistic rather than selective feeding behavior for chum fry based on prey availability.
One health toxicology: expanding perspectives and methods to assess environmental contaminantsThe discipline of One Health is founded on the principal that environmental health, animal health, and human health are interconnected. Although the field has been largely focused on zoonotic diseases, examining concepts such as toxicology under a One Health lens can offer a more holistic and preventative approach to research and implementation and, in particular, how fish-based diets may be involved with One Health outcomes. Here we present three general case studies that demonstrate new approaches to investigating One Health toxicology. In Chapter One we show how Arctic canids can be used as environmental sentinels for human health. We discuss three separate canid studies; in the first we find that Arctic foxes can act as sentinels of Arctic contaminants due to their foraging plasticity, in the second we examine the use of fish-fed sled dogs as a model for the effects of a fish-based diet on contaminants exposure and gene transcription, and in the third we develop the sled dog as a model for particulate matter air pollution in the Fairbanks North Star Borough. In Chapter Two we utilize the Steller sea lion, a nonmodel organism, as a sentinel for the effects of fish-based diet mercury exposure induced whole-genome changes in gene transcription (RNA-Seq). Using newly developed informatics tools we assemble a de novo transcriptome and examine large scale changes in gene expression related to mercury exposure and other One Health uses. This approach is extremely adaptable and has the potential to be applied across numerous non-model organisms and contaminants. We also applied a microbial mining algorithm to our RNA-Seq data and found evidence for a hemotropic Mycoplasma spp. in one of our samples. In Chapter Three we examine sources of mercury exposure for pregnant women from La Paz, Baja California Sur, Mexico. We found mercury concentrations to be generally low among the examined fish species and staple foods. While typical dietary assessments rely on recall surveys and questionnaires, we found that examining chemical biomarkers of diet including stable isotopes of carbon and nitrogen are critical in dietary risk assessment. Taken together these three investigations offer valuable lessons and techniques which can be applied to the field of One Health toxicology; especially to those fish diet based systems.
Winter habitat of arctic grayling in an interior Alaska streamPlacer mining and the lack of information on winter ecology of Arctic grayling Thymallus arcticus. has raised concern for this popular sportfish. A study was designed to validate aerial radio telemetry data and to locate and describe overwinter areas (OWA) of Arctic grayling in Beaver Creek, Alaska. Reliance on aerial data alone resulted in overestimation of survival and misidentification of 14 of 26 designated OWAs. Twenty-one Arctic grayling were tracked downstream 12-58 km to 12 OWAs spanning a 31-km section of Beaver Creek. Radio-tagged and untagged Arctic grayling occupied areas with ice thickness of 0.4-1.4 m overlying 0.06-0.52 m of water, flowing at 0.03-0.56 m/s. During winter, discharge, cross-sectional area, velocities, and water width in four OWAs decreased until late March; then, cross-sectional area increased due to an increase in discharge that pushed the ice upward. Adult Arctic grayling overwintered downstream of habitat disturbances, and occupied much shallower winter habitats than expected.