Thesis (PH. D.)--University of Michigan, 1941. / Reprinted from Papers of the Michigan academy of science, arts, and letters, vol. XXVIII, 1942. Published 1943. Literature cited: p. 308-312.

[No abstract available] / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--University of Michigan, 1924. / Thesis note on label mounted on t.p. Bibliography: p. 67-71.

Inaug.-diss.--Bern. / "Literatur-verzeichnis": p. 5-[7].

Thesis (Ph. D.)--University of Michigan, 1924. / Thesis note on label mounted on t.p. Bibliography: p. 67-71.

Criteria for interpretation of scales of steelhead (Salmo gairdneri gairdneri) and for their use in back calculation of early life history were established. With these criteria, features of the life history of 784 steelhead from the anglers' catches of the Chilliwack River, B. C. were studied. Age composition of adult steelhead runs from 1948 to 1953 was uniform except for the suggestion of a slightly dominant year class, represented as 4 year old fish in 1950, 5 year old fish in 1951 and 6 year old fish in 1952. There was no suggestion that fish of any particular age, life history, sex or length tend to return as adults at any particular season of the year. The age and size of smolts at migration is variable, with the majority however in the 2 and 3 year age groups and ranging in size from 15 to 20 cms. Smolt migration usually occurs in March, with a small proportion of late migrants in August. Spawning frequency of adults was reviewed. Females generally spawn at an earlier age and more frequently than males. It is concluded that the variability in the life history of the steelhead acts as a safeguard in its conservation. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 101-112).

This study was designed to provide information about the juvenile life history of coho salmon, Oncorhynchus kisutch, in the Tenmile Lakes in Oregon by 1) classifying scales of spawning fish and outgoing smolts (1+), 2) assessing the contribution of juvenile life history types to the returns of adults (3₂) and jacks (2₂), and 3) comparing growth rates and survival of different types. Scales of outmigrating smolts from one brood year, jacks from two brood years, and scales of adults from four brood years were classified into juvenile life histories and examined for several scale characters. A linear discriminant function analysis was used to show the separation of the types and to determine the most distinguishing scale characters. Length of smolts at ocean entry back-calculated from scales of jacks and adults was compared with the length of the observed group of emigrating smolts. Based on variation in numbers and spacing of circuli and the size of the freshwater scale zone, believed to represent different residence time in the tributaries and the lakes, four types of juvenile life histories were defined. Fish classified as type 1, stream-reared, are believed to have reared in the tributaries until migrating as smolts in the following year. Type 2, stream-lake-reared, fish are thought to have reared in the tributaries for almost a year but then moved down to the lakes, where rearing continued until smolt migration in spring. Type 3, stream-lake- reared, are believed to have reared for a short time in the tributaries, then moved down to the lakes sometime in their first year of life. Rearing continued in the lakes until spring of the following year. Type 4, lake-reared, are thought to have moved down to the lakes shortly after emergence from the gravel, where they reared until migrating as smolts in the following spring. Scales of smolts, jacks, and adults were sorted into these four types. Presently, coho salmon fry and yearlings appear to be moving out of tributaries in late spring and from March to beginning of May, respectively. Migration of smolts out of the lake system to the ocean occurs mostly within the month of May. Recent habitat surveys show that dramatic seasonal changes occur in use of rearing habitat by juvenile coho salmon in the Tenmile Lakes tributaries from summer to winter. In winter juveniles appear to be using more low gradient, low velocity, off-channel areas than in summer. Fish of type 4 represented 90%, 43%, and 74% of the returns of adults in 1957- 58, 1963-64, and 1971-72, respectively, and 90% of the returns of jacks in 1962-63 and 1970-71. However, no type 4 fish was represented in the returns of adults in 1985-86, whereas type 1 fish represented 89% of the returns. Type 4 appeared to have grown better in fresh water, reached a larger size at outmigration, and have a greater relative survival than fish of type 2, when compared among the observed group of smolts, returning jacks, and adults. The large proportion of the escapement returning as jacks for some of the years may indicate good growing condition for juvenile coho salmon in fresh water. According to the classification of jack scales a large proportion of fish returning as jacks were lake-reared and were found to be larger at migration to ocean than fish returning as adults. This may suggest that fish that reared well in the lakes and reached a large size at outmigration had the tendency to mature early and return as jacks. Based on the analysis of scales, lake-reared juvenile coho salmon formerly contributed well to adult returns. The former high returns of jacks and adults reflect the importance of the lake habitat for the coho salmon populations of this system. In order to enhance this stock to a higher level, management strategies should be focused on making the lake habitat available to juvenile coho salmon for at least some part of their freshwater life. / Graduation date: 1992

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 97-105). Also available on the World Wide Web.

The mucus coat on the skin and gill of fishes serves a variety of protective functions including lubrication of the body surface, prevention of infection, and deterrence of parasites. Since mucus secretion in some teleosts appears to be controlled by the osmoregulatory hormones, prolactin and Cortisol, it was thought that the mucus coat may participate in teleost hydromineral balance. The primary objective of this study was to -examine the possible role of mucus in-osmoregulation of Leptocottus arma- tus Girard 1854 (Teleostei, Cottidae) and to relate these findings to the -endocrine control of mucus secretion. Whereas Leptocottus skin includes three types of secretory cells (eosinophilic granular, goblet, and cuticle-secreting cells) , the gill epithelium -has only goblet cells. Of ten cottid species examined histochemically, only seawater sculpins produce neutral mucins, while fresh water, seawater, and euryhaline species produce acidic mucins. Leptocottus primarily secretes a sialoglycoprotein, though sulphated mucins are present in gill goblet cells and the cuticle-secreting cells. The granular cells produce a tryptophan-rich basic protein. - Hypophysectomy or seawater adaptation reduce the number of gill goblet cells, compared to respective sham-operated or 5% seawater-acclimated controls. Ovine prolactin treatment of hypophysectomized fish prevented this decrease. In seawater-acclimated Leptocottus prolactin injections increase the number of gill mucus cells, while Cortisol injections of 5% "seawater-adapted fish had the opposite effect. The cuticle-secreting cells were most active in 5% seawater-adapted fish and this state was maintained by prolactin. A moderately active state was typical of seawater-adapted fish and this condition could be maintained by Cortisol or ovine growth hormone. The lowest activity of the cuticle-secreting cells occurred in hypophysectomized fish. Though prolactin and Cortisol appear to control the gill goblet cells and the cuticle-secreting cells, neither hy-pophysectomy nor treatment with prolactin or Cortisol significantly affected the skin goblet cells. The mucus coat appears incapable of reducing integumental permeability through steric interference of diffusion or through Donnan exclusion of ions from the mucus coat. Further, it is argued that enhancement of unstirred layers by mucus could not significantly affect hydromineral balance. Instead, alterations of the mucus coat with environmental salinity may be associated with the lubricating properties of mucus. Leptocottus mucus is a viscous non-newtonian fluid when concentrated but is an efficient lubricant when dilute. Seawater-adapted Leptocottus produce a more efficient lubricating mucus than do 5% seawater-acclimated fish; this effect appears to involve the cuticle-secreting cells. In an associated study I showed that the skin of the goby Gillichthys mirabilis participates actively in osmoregulation through extra-renal ion excretion. Thus the effects of prolactin and Cortisol may be primarily to control active transport in the skin. / Science, Faculty of / Zoology, Department of / Graduate