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Glaciated areas offer a unique opportunity to study the dispersal of animals . During glaciation the fauna of glaciated areas was either destroyed or forced into ungla iated refugia. ..When the icesheets retreated the glaciated regions were open to reinvasion.

No description available.

Glaciated areas offer a unique opportunity to study the dispersal of animals. During glaciation the fauna of glaciated areas was either destroyed or forced into unglaciated refugia. When the icesheets retreated the glaciated regions were open to reinvasion. [...]

Nine series of vertically-stratified zooplankton tows were made with a closing net at a single station in southern Kaneohe Bay, Oahu, Hawaii, between 31 August 1973 and 11 April 1974. Sampling periods occupied from 12 to 26 hours, with tows usually taken at about 3 m intervals between the surface and a maximum depth of 10 m. A total of 21,254 fish larvae of 49 kinds was collected. Six species were abundant: Foa brachygrammus, Omobranchus elongatus, Callionymus decoratus, Caranx mate, Stolephorus purpureus, and Abudefduf abdominalis. Blennius sp. and Gnathanodon speciosus were commonly taken in small numbers. These common larvae displayed five "distribution patterns: 1. F. brachygrammus and the smallest S. purpureus were most abundant near the surface at night and at depths below 4 m during the day; 2. C. mate and G. speciosus were dispersed throughout the water column at night and usually most abundant between 5 m and 6 m depth during the day; 3. Blennius sp., o. elongatus, and A. abdominalis were dispersed throughout the water column at night and concentrated near the surface during the day; 4. the larger ~. purpureus maintained a level of maximum abundance below 6 m day and night; 5. C. decoratus was taken at all depths at all times. Patterns 1, 2, and 3 are shown to be light-related. Pattern 4 is shown to be partially attributable to avoidance of the towed net by S. purpureus larvae larger than about 6mm, and a feeding-related migration is proposed to account for pattern 5. The observed patterns are analogous to those shown for fish larvae in the open ocean on scales of from 50 m to 200 m. It is proposed that Kaneohe Bay represents a vertically compressed ocean with respect to the vertical distribution of fish larvae. / Typescript. Bibliography: leaves 130-134.

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Demographic characteristics of juvenile Dover sole (Microstomus pacificus) were examined in relation to physical and biotic factors to develop a hypothesis explaining annual variations in recruitment. Surveys were conducted along the Oregon continental shelf at depths between 50-400 m bimonthly during 1989 and annually (in March) between 1990 and 1993. To determine settlement timing, growth, and mortality, daily growth increments were validated, as was position of the first post-settlement annulus. A method of estimating precision of otolith elemental composition with the electron microprobe was developed; otolith microstructure and microchemistry were used to identify a landmark associated with settlement. Mean density of 0-group settlers varied annually, with 1989 and 1990 high, 1991 and 1992 low, and 1993 intermediate. 0-group abundance was correlated with fall offshore divergence one year before settlement and with southward geostrophic velocity during the summer before settlement. These conditions may be related to production of prey available to pelagic larvae. Density of 0-group Dover sole was highest between 100-119 m, but deeper areas were also utilized in years of highest abundance. Density was not correlated with spawning stock biomass or density of older juveniles. It was correlated with rex sole (Glyptocephalus [Errex] zachirus) density. Growth rate was positively correlated with mean April-October upwelling and was not related to density or mortality of Dover sole. First-year mortality was positively correlated with early settlement of 0-group larvae, possibly due to an advantage of settling and migrating to the primary nursery area well in advance of the spring transition. A multiple regression model predicting density of 1-group Dover sole from three physical environmental factors was applied to an independent time series of Dover sole "age-5" recruitment estimates (Turnock and Methot 1992). The model was a poor predictor of annual recruitment to fisheries but a good predictor of trends based on five-year running averages. Results suggest that multi-year trends in Dover sole recruitment to fisheries can be explained by a small set of density-independent physical factors. / Graduation date: 1995

The Sultanate of Oman has 1700 km of coastline extending from the Arabian Gulf south to the Arabian Sea. The demersal fish distributions and assemblages have not previously been well defined. In winter, variations in the oceanography of the area are minimal. In summer, however, the Arabian Sea is strongly influenced by the southwest monsoon. For this study the continental shelf off Oman was divided into eight regional areas and research trawl data on the distribution of demersal fish assemblages was studied using two forms of multivariate statistical analysis: two-way indicator species analysis and detrended correspondence analysis. The study was carried out to examine the influence on the species assemblages of geographical zonation, seasonal variation, and factors such as depth, time of day, and distance from untrawlable ground. There was seasonal variation in the fish assemblages and this variation was greatly influenced by the summer monsoon. Within each regional area depth appeared to be the major factor determining species distribution. In addition to the multivariate analyses, univariate techniques were applied to the catch rate data for forty commercial species to study in detail the influence of time of day and distance from untrawlable ground, factors which could potentially influence stock assessment estimates of fish biomass. Because the data were highly unbalanced, they were analyzed using General Linear Model with five factors, two continuous variables, and ten interaction terms to examine variation in the log-transformed catch rates. The factors time of day and distance from untrawlable ground, in combination with other factors, had significant effects on the catch rates for half of the species. / Graduation date: 1995

Resident rocky-shore fishes were quantitatively sampled and visually censused on islands and mainlands in the Gulf of California. Patterns of biogeographic distribution were investigated in relation to the MacArthur-Wilson model of island biogeography, the lottery hypothesis of reef fish community structure. Analyses of the collections show regular patterns of distribution and relative abundance of rocky-shore fishes. Most of the variation in species number and species diversity is explained by latitude and the associated gradient of physical and oceanographic parameters. The correlation of species number and diversity is higher for island than for mainland samples. The best graphical (numerical clustering) evidence of distinct biogeographic regions in the Gulf is obtained using a similarity measure which includes proportional abundance of species (Horn's measure). Groups corresponded to upper, central, and lower Gulf areas. Greater species number, biomass, and numerical (H'(n)) and biomass (H'(b)) species diversity on islands is paralleled by greater water clarity and volume of ocean near collecting sites. This is true for the entire Gulf, the central Gulf, and for Isla San Pedro Nolasco versus the adjacent mainland rocky shoreline in the central Gulf. Community differences between island and mainland areas were greatest in the upper Gulf. 'Gamma' diversity, a proposed measure of community variance (site to site species turnover within habitats) is highest for mainlands and lowest for islands indicating more predictable community species composition on islands. Visual censuses show a good species-area curve for patch reefs and very small nearshore islands and lower species turnover in more exposed near shore habitats. There is a trend toward smaller body size of fishes on islands and an increase in body size with latitude. It is suggested that both phenomena are the result of thermally regulated growth rather than genetic population differences. High endemism in the resident rocky-shore community (the small sedentary, blennioid and gobioid fishes) is attributed to their relatively poorer means of dispersal (demersal eggs and short-lived pelagic larvae) as compared to the more mobile larger resident reef fishes with greater means of dispersal (pelagic eggs and long-lived pelagic larvae). Insular biogeographic processes in marine reef habitats are mediated by physical and biological oceanographic conditions and processes. Distance appears to be no significant barrier to dispersal for Gulf rocky-shore fishes. Immigration rates may be high in rocky habitats in general, but in inshore mainland areas physical and biological disturbance suggest higher extinction rates and consequent lower diversities. The results of these studies do not agree well with either the MacArthur-Wilson model of island biogeography or the lottery hypothesis of reef fish community structure, however, disturbance does seem to play some role in regulating diversity. Considering dispersal and colonization, oceanographic conditions (e.g., water quality, current patterns) may be important ecological factors that influence the evolution of this community.

This thesis explored the influence of fish behavior and distribution on the accuracy and precision of quantitative estimates of fish biomass and abundance as assessed by hydroacoustic techniques. Rainbow smelt (Osmerus mordax), a pelagic fish known to undertake diel vertical migrations and to exhibit changes in aggregation intensity associated with these movements was used as the model species for this study. The diel vertical migrations of smelt resulted in their potential inaccessibility to the acoustic gear. To obviate this problem a model of the diel migration of smelt based on observations of their behavioral responses to ambient light and water temperatures, was developed and used to time acoustic estimates of fish biomass and abundance to periods when they were unbiased by inaccessibility. Acoustic surveys were then conducted to evaluate the direct influence of fish aggregation on estimates of fish abundance, and to examine the effect of changes in fish distributions on the statistical validity of acoustic analyses. Comparative acoustic surveys, conducted when fish were schooled and dispersed, showed abundance was underestimated by up to 50% when schooling prevailed. The influence of changes in the level of fish patchiness, induced by diel schooling, on the statistical precision of acoustic estimates of abundance and biomass was found to be insignificant. Cluster sampling, a robust approach to the inherent problems of transect sampling created by autocorrelated data series was applied to acoustic data for the first time and its effectiveness was assessed. Cluster sampling yielded estimates of biomass and of abundance that were more precise than were estimates based on the traditional approach of analyzing complete transects.