Thesis (M.S.)--Georgia Southern University, 2008. / "A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science." Directed by Christopher P. Cutler. ETD. INDEX WORDS: Aquaporin, Aquaglyceroporin, Osmoregulation, Water Homeostasis, Elasmobranch, Biological Transport, Molecular Sequence, Sequence Homology, Kidney, Rectal Gland Includes bibliographical references (p. 116-120) and appendices.

As the requirements for vitamin “A” increased during World War II, the livers from the Pacific coast dog-fish (Squalua suckleyi) and the soup-fin shark (Galeorhinus galeua) became one of the principal sources of vitamin "A". Under the pressure of a high and increasing fishing intensity, the catch of these two sharks in British Columbia has dropped greatly during the years following 1944. Changes in the availability or relative abundance of the dog-fish and soup-fin shark caught in Hecate strait and the dog-fish caught off Barkley sound on the west coast of Vancouver island were determined from the analysis of the-individual tally slips or fish receipts of each fishermen's landing of the livers from these two sharks caught by sunken gill-nets. Methods employed in the analysis of the data to determine the availability, included the analysis of the total landings of the livers from each area under investigation; the average boat catches per month; and average boat catches per trip per month. The method of link relatives is used in the analysis and the catch per unit of effort off Barkley sound is determined. The availability or relative abundance of the dog-fish in Hecate strait was found to decline from 1943 to 1945 with a slight increase during 1946. The availability of the soup-fin shark was found to decline greatly from 1944 to 1946. In the year 1946, the soup-fin shark fishery in Hecate strait was almost a failure. The decline in the availability of the dog-fish and the drop in the average vitamin “A” per gram of liver oil is closely related to the removal or possible depletion of the older age classes from the population. On the west coast of Vancouver island, off Barkley sound the index of return per unit of effort (one sunken gill-net 75 fathoms long fishing over a period of 24 hours) indicated that the availability of the dog-fish has increased in each year since 1944. The sunken gill-nets (7 inch stretched mesh) were found to select; dog-fish greater than 76 cm. in length. Small dog-fish of no commercial value (less than 76 cm.) tend to pass through the meshes. / Science, Faculty of / Zoology, Department of / Graduate

Elasmobranchs (sharks, skates, and rays) are a primarily carnivorous group of vertebrates that consume very few carbohydrates and have little reliance on glucose as an oxidative fuel, the one exception being the rectal gland. This has led to a dearth of information on glucose transport and metabolism in these fish, as well as the presumption of glucose intolerance. Given their location on the evolutionary tree however, understanding these aspects of their physiology could provide valuable insights into the evolution of glucose homeostasis in vertebrates. In this thesis, the presence of glucose transporters in an elasmobranch was determined and factors regulating their expression were investigated in the North Pacific spiny dogfish (Squalus suckleyi). In particular, the presence of a putative GLUT4 transporter, which was previously thought to have been lost in these fish, was established and its mRNA levels were shown to be upregulated by feeding (intestine, liver, and muscle), glucose injections (liver and muscle), and insulin injections (muscle). These findings, along with that of increases in muscle glycogen synthase mRNA levels and muscle and liver glycogen content, indicate a potentially conserved mechanism for glucose homeostasis in vertebrates, and argue against glucose intolerance in elasmobranchs. In contrast to the other tissues examined, there was a decrease in glut4 mRNA levels within the rectal gland in response to natural feeding, a factor known to activate the gland, suggesting mRNA storage for rapid protein synthesis upon activation. A similar trend was also shown for sglt1 in the rectal gland, and the ability of GLUT and SGLT inhibitors to prevent chloride secretion solidified the importance of glucose uptake for gland function. The exogenous factor of salinity was also investigated and high levels of glut mRNA were observed within the rectal glands of low salinity-acclimated fish relative to control and high salinity fish, reiterating the idea of mRNA storage when the gland is expected to be inactive. Taken together, the results of this thesis demonstrate that glucose is an important fuel in the dogfish (and likely other elasmobranchs) and that the dogfish is fully capable of regulating its storage and circulation, contrary to prior beliefs.

No description available.

No description available.

Thesis (Ph.D.) -- University of Rhode Island, 2008. / Typescript. Includes bibliographical references (leaves 170-184).

This study examines the spatial and temporal distribution and life history of the "offshore" component of the Northeastern Pacific spiny dogfish (Squalus acanthias) population. Distribution was examined in relation to latitude, depth, the Columbia River plume and large-scale climate changes. Fishery and survey data indicate that the Northeastern Pacific spiny dogfish population has a broad range along the Washington and Oregon coasts, with the highest abundance occurring off the northern Washington and central Oregon coasts. Catches, however, were patchy throughout the 37-year period of available survey data. In terms of depth, the greatest abundances of spiny dogfish were captured in shallow waters (55-184 m). An examination of the influence of the Columbia River plume using a generalized additive model (GAM) indicated that the fish were influenced significantly by the salinity, chlorophyll and surface temperature patterns associated with the plume, preferring the oceanic zone to the plume zone. In contrast, there was no indication that the catch-per-unit-effort of spiny dogfish was influenced by the Pacific Decadal Oscillation (PDO) or the El-Niño (ENSO) over 24-year period of the National Marine Fisheries (NMFS) triennial shelf groundfish survey (1977-2001). The multi-cohort age structure of the population, due to the spiny dogfish's late age at maturity and long lifespan, as well as the low fecundity make it difficult to detect the loss of a single cohort or two when examining abundance trends. Moreover, effects on abundance may be time-lagged, especially if, as is likely, the youngest cohort(s) is the most vulnerable life stage. Their absence would not become evident until they were large enough to have been captured by the survey gear. Sensitive abundance data and/or age-structured data would be needed to identify a pattern. I quantified the age, maturation and fecundity of the spiny dogfish and use these data to develop an age-structured matrix model to examine the sensitivity of the population's growth rate to changes in mortality (i.e. fishing). Female spiny dogfish in this population have an average age at 50% maturity of 28 years and males 20 years. Average length at 50% maturity was 85.0 cm for females and 71.5 cm for males. Female fecundity was extremely low, averaging eight pups per clutch biennially and ranging from four to 14. The number of pups increased with length, but not age. Using these data, a deterministic, female-based model was developed. Asymptotic population growth rate (λ) was determined to be very low, 1.01, and comparable to population growth rates calculated for "coastal" populations. When fishing mortality was incorporated into the model, the fishery was only sustainable when exploitation was low and strict size limits enforced. When fecundity was doubled, the population growth rate increased from 1% to 3% per year. This 33% increase in population growth was equivalent to the effect of a decrease in the age at first maturity of three years. Given that responses to changes in population demographics through shifts in fecundity or spawning frequency are likely constrained, responses would then seem likely to involve changes in age at maturity. These life history traits translate into a low potential population growth and as a consequence high susceptibility to overfishing. My findings indicate that the Northeastern Pacific spiny dogfish are relatively slow growing, late to mature, and have low fecundity and a patchy distribution, with large catches occurring off the northern Washington and central Oregon coasts in shallow waters (55-184 m). These life history traits and distributional patterns are useful in the development of population models to predict responses to environmental fluctuations or increased mortality and thus the management of the population. It is evident from my findings that periodic monitoring is necessary to track possible catch declines off the northern Washington and central Oregon coasts and prevent collapse of the population should it be targeted by a fishery and overfishing occur. / Graduation date: 2005

Afhandling - Copenhagen. / Summary in English and Danish. Bibliography: p. [131]-134.

Afhandling - Copenhagen. / Summary in English and Danish. Bibliography: p. [131]-134.

Thesis (M.Sc.)--Acadia University, 1998. / Includes bibliographical references (leaves 40-50). Also available on the Internet via the World Wide Web.