Thesis (M.S.) in Marine Biology--University of Maine, 2002. / Includes vita. Bibliography: leaves 61-69.

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A considerable number of littoral and shallow water marine molluscs from the West Indian region and other areas reached Europe during the second half of the eighteenth and first half of the nineteenth century. These were, in many cases, brought by travelers and navigators and later described by European naturalists. Outstanding among these were Jean B. Lamarck, Carl von Linnaeus, J. F. Gmelin and Alcide d'Orbigny. Although they reported many species from the Lesser Antilles, very few are recorded from Barbados. [...]

Northern fringe populations generally have low amounts of genetic variation and inhabit habitats where specific adaptations are needed. On the Swedish west coast, the natterjack toad (Bufo calamita) inhabits skerry islands. I have examined: I) adaptation to two environmental stressors in this habitat; II) the genetic population structure within the skerry habitat; III) the effects of neutral genetic variation, selection and genetic drift on trait divergence within the skerry habitat; and IV) the effects of genetic variation on fitness under three thermal conditions of varying stressfulness. V) I have also studied the impact of putative local adaptations on the Scandinavian green toad (Bufo viridis) conservation programme. The results suggest that the skerry natterjack toads are locally adapted to the desiccation risk in their habitat. However, despite inhabiting a more saline habitat, they had a lower salinity tolerance when compared to their conspecifics in the more general habitat. The lowered salinity tolerance is most likely explained by the presence of negative genetic correlations between salinity tolerance and desiccation avoidance and suggests that the occurrence of multiple environmental stressors may constrain adaptation. Within the skerry habitat, the toads exhibited a strong population structure with populations differing in their levels of genetic variation. Moreover, within the skerry habitat, the results suggest uniform selection pressures. However, correlations between trait values and neutral genetic variation suggest that inbreeding depression may affect trait values and thus potentially constrain adaptation. In the natterjack toad, fitness costs associated with lack of genetic variation were only present under benign conditions and not under more natural conditions. This suggests that environmental stress masks inbreeding depression in these traits under natural conditions. In the study regarding the Scandinavian green toads, I found that one population inhabiting a saline habitat had a higher salinity tolerance than other populations in less saline habitats. This suggests the presence of local adaptation, which should be acknowledged in the green toad conservation programme. Several of the northern fringe populations of toads fulfill the criteria of being Evolutionary Significant Units and their conservation thus should be prioritized.

Pacific salmon (Oncorhynchus spp.) are key elements of ecological systems, and play an important role in the cultural foundation of human societies. All species of wild salmon face multiple, simultaneous threats, with habitat degradation likely playing a key role in survival. Open net-pen salmon farms can degrade important nursery marine habitat for wild juvenile salmon by disrupting natural salmonid host-parasite dynamics. The first two chapters in this thesis examine louse parasitism of wild juvenile chum (Oncorhynchus keta), pink (O. gorbuscha), and sockeye salmon (O. nerka) in relation to their marine migration past salmon farms. I compare sites of low and high exposure to salmon farms, and include two areas without farms on British Columbia’s central and north coasts to assess baseline infection levels. Louse prevalence and abundance were lowest and most similar to natural baseline levels at low exposure sites, and highest at high exposure sites in all farm regions. A significantly greater proportion of the lice infecting juvenile chum and pink salmon were Lepeophtheirus salmonis at high exposure sites. Caligus clemensi was the principal louse species infecting all juveniles in areas without salmon farms, and at low exposure sites within salmon farm regions; C. clemensi was also the dominant louse to infect juvenile sockeye that migrated past farms. Mixed-effects modelling results showed that exposure to salmon farms was the most consistent factor to explain the variation in louse infection levels, and support my hypothesis that salmon farms are a major source of sea lice on juvenile wild salmon in regions with salmon farms. I discovered that juvenile sockeye at one particular location within the Georgia Strait hosted unusually high lice levels; this location was situated at a distance from salmon farms, but near a farm salmon processing facility. Upon further investigation, I found live sea lice, Lepeophtheirus salmonis, mucus, and fish tissue in effluent discharged from the processing facility. Sea lice transmitted from this source may pose a threat to wild salmon populations, and the release of potentially untreated offal, including blood water, is of considerable concern. These results form the third chapter in my thesis. Given the challenges facing juvenile salmon in general, and sockeye from the Fraser River in particular (i.e., 2009 was the lowest return on record), and because poor habitat conditions within Georgia Strait are considered the major cause of the recent decline in Fraser River sockeye, this raises the question as to whether food limitations are a factor. The final chapter in my thesis examines the prey assemblage, diet composition, and foraging selectivity of juvenile sockeye, and investigates whether food limitations can be detected during early migration through Georgia Strait. Juvenile sockeye demonstrated high prey diversity, with preference for particular prey. Prey were more concentrated in the north, which may help explain migratory behavior of juveniles through the study region, and temporal similarities in sockeye foraging success may reflect short-term food resource stability. Moreover, I could not find evidence of food limitations that might suggest juvenile sockeye were strongly food deprived during the years of this study. Finally, my thesis explores how best to conserve salmon populations given the multitude of stressors. Because stressors often interact to produce compound effects and unpredictable results, ranking the overall threats in order of severity may not be useful. Instead, the most successful ranking system may be in terms of reducing harm where possible. For juvenile salmon during their early marine migration, risks posed by salmon farms can be more easily mitigated than the far-reaching effects on ocean productivity of climate change and ocean acidification, or predator removal. I recommend we begin here. / Graduate

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Typescript (photocopy) / Bibliography: leaves 163-177. / Microfiche. / xi, 177 leaves, bound ill., maps 29 cm

Lingula is one of the most morphologlcally conservative genera known. Thls brachiopod has remained essentially unmodified for 350-400 mllllon years (Hyman, 1959. Paine, 1963). It is one of the oldest, if not the oldest, llvlng animal genus wlth a fossil record, and is well represented in the geologic column from the Ordovician. Deposits containing Lingula are thought to have been formed in a shallow, warm, sea water environment (Weller, 1957, Cloud, 1948). Their fossil remains occur on all continents (except possibly Africa) in most kinds of sedimentary facies, but most frequently ln black-shales and related sediments (Moore, Lalioker and Fisher, 1952). [...] This investigation, which extended from June 1967 to February 1969, deals with the distribution, limiting factors, interspecific interactions, feeding, growth and other aspects of the life history of Lingula reevii in the southern sector of Kaneohe Bay. The main objectives were 1) to understand the ecological position of Lingula reevii, especially with respect to limiting factors, interspecific interactions, distributional pattern and growth and 2) to use this ecological information as an aid in the understanding of the ancient environments in which Lingula is found as a fossil. / Typescript. Bibliography: leaves 48-49.

Typescript. Bibliography: leaves 46-47.

The chaetognath Sagitta enflata dominates the standing stock of macrozooplankton,and of planktonic carnivores, in the southern basin of Kaneohe Bay. During 1973-74, sampling with vertical net hauls showed no horizontal patchiness in the population. The abundance varied temporally, mainly over periods of months; shorter-term variations were similar to those expected between replicate hauls. Between 1968-69 and 1973-74, both the stock and the dominance of Sagitta in the community increased; both may be related to enrichment of the basin with sewage. Individual Sagitta eat an average of seven prey items per animal per day. The ration in terms of nitrogen or other weight measures varies with animal length, larger Sagitta ingesting more material each day, but smaller Sagitta ingesting a larger fraction of their own body weight daily. Sagitta's predation has little impact on the prey populations, other than Oikopleura, which is the main food of larger Sagitta. Sagitta excretes ammonium and phosphate at rates roughly similar to other zooplankton of similar size. When feeding is prevented during excretion experiments, the specific excretion rates decrease rapidly with time, approaching those observed in laboratory-starved animals. Like other zooplankton, Sagitta has higher N/P ratios in its body tissue than its prey; its soluble excreta thus have a still lower ratio. Despite its abundance and dominance of macroplankton stock, Sagitta is only a minor contributor to nutrient regeneration in the southern basin, which is to be expected, based on its trophic position. The population's rates of growth and mortality were considerably higher than the net change in the stock during most periods analyzed. The instantaneous rates of birth and death are strongly correlated, suggesting a feedback mechanism regulating the population. The population incorporates carbon at about 1% of the rate of primary production in the basin. This is consistent with ecological efficiencies of 10% at each of the two steps froln producers to herbivores to Sagitta's position as the dominant primary carnivore among the plankton. Most of Sagitta's production is probably consumed by predators in the southern basin. The major predator may be nehu, a fish taken for tuna bait from this and other nearby environments. With the planned diversion of sewage from the basin, it is likely that both the stock and the dominance of Sagitta in the southern basin will decrease. / Thesis for the degree of Master of Science (University of Hawaii at Manoa). Typescript. Bibliography: leaves 140-147.