This study investigates the life cycle of Sphaerospora truttae, a myxozoan parasite of the Atlantic salmon, using molecular methods based on the 185 rONA. DNA sequencing showed that the 185 rONA of S. truttae differs substantially from the sequence obtained from its proposed alternate actinosporean life cycle stage, Echinactinomyxon type 5. With more than 90% sequence identity Echinactinomyxon type 5 is closely related to Myxobolus portucalensis whereas S. truttae with an extraordinary long 185 sequence (2541 bp), with inserts in the variable regions of the gene, does not relate closely to any myxozoans. On the basis of the obtained sequence for S. truttae, a single round nested peR assay was developed which allows low-level detection and specific identification of S. truttae in all life cycle stages. Furthermore, two of the primers from the peR assay were successfully used on tissue sections in an optimised in situ hybridisation (ISH) protocol. ISH experimentally identified the gills as the predominant entry locus of S. trottse into the fish host and it detected the spatiotemporal migration of the parasite via the vascular system into the target organ, the kidney. The ISH protocol and the peR assay were also used to screen oligochaetes and other co-occurring invertebrates for S. truttae infection but an alternate host for S. truttse could not be identified. However, 12 actinosporean stages were found and they were characterized on the basis of their 185 rONA, together with 9 further myxosporean species from wild fish in the same riverine habitat. Three actinosporeans were found to be genetically identical with three myxosporeans (Myxidium truttae, Chloromyxum truttse and Chloromyxum sp.) and thus represent alternate life cycle stages of these species. Phlyogenetic analysis of the myxozoans identified a very basal position of S. truttae and S. elegans, as a sister group to the marine species. All other species were nested in the freshwater clades and clustered according to host tissue localization, but independent from host species or myxozoan spore taxonomy.

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No description available.

Understanding how energy flows through ecosystems reveals underlying ecological patterns that can drive processes such as growth and survival of organisms. To understand how energy is transferred through organisms, the energy content or energy density (ED) of both consumers and prey must be determined. To facilitate the ease of ED measurement across taxa, I developed a model to estimate the ED of organisms using percent ash-free dry weight (AFDW). Using data obtained from 11 studies with broad taxonomic, temporal and spatial coverage, I compared common predictors of ED using linear models. AFDW was determined to be the superior predictor of ED relative to previous metrics and was predictive for a broad range of taxonomic groups including aquatic invertebrates, aquatic vertebrates, aquatic plants and terrestrial invertebrates. This AFDW model enables measurement of ED with minimal cost and time investment, which allows ED to be more readily determined for diverse taxa. Next, I applied the AFDW method to the diet of a pelagic consumer, juvenile Chinook Salmon, to determine the effect of variable prey ED on growth. In 2017, I collected monthly zooplankton and fish samples of known importance in the diet of juvenile Chinook Salmon to look for fine-scale taxonomic, temporal and spatial differences in ED. Decapod zoeae and megalopae differed significantly from each other and showed family level variability in ED. Amphipods also showed significant species-level variability in ED. Temporal differences were observed, but did not reveal a consistent pattern among groups. Spatial variability was not significant. Using bioenergetics models, growth of juvenile Chinook Salmon was predicted to be greater when using fine-scale ED estimates. This difference was not substantial on average, but in some cases represented more than a two-fold difference in growth between coarse- and fine-scale estimates. These results suggest the need for higher resolution diet ED data when determining growth projections for juvenile Chinook Salmon. With the aid of the AFDW model presented in this thesis, the effort required to obtain these data is greatly reduced. / Graduate / 2020-03-25

An oral Vibrio vaccine for salmonids was developed. The vaccine was produced by spray coating lyophilized formalin-killed whole cells of Vibrio anguillarum (VA LS 1- 74) onto non-pareil sugar beads. Then methacrylic acrylic acid copolymer (Eudragit L-30D) was applied as an enteric protective coating. Using x-ray radiographic techniques, it was found that large particles (> 1.1 mm) remain in the fish stomach for more than 2 hours before they would enter the pyloric caeca. The pyloric sphincter which has an opening of 0.94 mm, acts as barrier to prevent the passage of large food particles in the stomach to the pyloric caeca. Based on this information non-pareil sugar beads of 18-20 mesh or smaller should be used as the vaccine carriers. A 15% (w/w) Eudragit L-30D coating is needed to provide enteric protection of the vaccine loaded sugar beads of 18-20 mesh size. Lower levels of coating resulted in the bead breaking down in the stomach and releasing contents prior to entering the pyloric caeca. Since the lymphoid tissues are diffuse throughout the whole GI tract, it may not be necessary to target a vaccine to deliver antigens to a specific area of the intestinal tract, but only protect the antigens from gastric fluids. In vitro dissolution studies indicate that 10% VA LS 1- 74 loading was sufficient for rapid vaccine release (42% released in 30 minutes) and a 15% Eudragit L-30D coating was suitable for providing protection against stomach acid. The vaccine product used in vivo studies contained 10% VA LS 1- 74 and 15% Eudragit L-30D on non-pareil sugar seeds of 18-20 mesh size. Coho salmon were given the vaccine orally, and 30 days afterward a live challenge test was performed. There was no significant difference in the survival rates in a live bacteria challenge test with the positive control (83.3%) and test (80.3%) groups. Both had higher survival rates than the no vaccine fed control group. The serum and mucosal antibody levels to Vibrio were significantly higher (p<0.01) in the test group (19700 units/ml) than the other two groups (2530 units/ml in the positive control group and 617 units/ml in the negative control group). The antibody titer appears to be a better indicator for vaccine efficacy than survival rate of live bacteria challenge tests. The oral Vibrio vaccine developed is effective, and the technique to protect the antigen can be applied to other antigens or proteins for oral delivery producing an economical pathway for mass vaccination of fish. / Graduation date: 1991

The research involved development of two ecological simulation models to explain the complex dimensionality of chinook salmon (Oncorhynchus tshawytscha) life history structure (represented by the age composition of the spawning stock) and management difficulties entailed in the complexity. Since different sizes of chinook salmon are thought to adapt differently to heterogeneous habitats, age composition of the spawning stock is determined by characteristics of the habitats of the substocks. Numerical properties of substocks result from the incorporation of individual spawners in different age classes and each substock performs differently because their age compositions are distinctive. A stock or population consists of substocks whose age compositions are concordant with their habitats. The productive capacity of a population will result from the incorporation of substocks. If habitat structures of streams are different, the age and size compositions and productive capacity of the populations may differ. Selective harvesting affects spawners in different ways, so that age compositions must be deformed differently by fishing pressure. Once the age composition deviates from the natural age composition, the productivity of the population will decrease. Population dynamics are strongly correlated with substock structure which is determined by habitat structure in a stream system. Hierarchical population structure make fisheries management difficult and requires not only quantitative but also qualitative analysis on the populations in relation to habitat classification. / Graduation date: 1990

The impacts that environmental factors brought to the population of the Formosan landlocked salmon are discussed in this paper and the evidence results indicate that the air temperature and typhoon have taken negative effect during past 15 years. Under the population simulations, without considering the environmental factors, it is clear that the population growth rate tends towards a steady state in the long run. On the contrary, the population would be in decline or suffer the extermination while we consider those factors.

Rapid advances in the aquaculture industry pose an environmental challenge that is generated by outbreeding between escaped domesticated and wild individuals. Given that escapees genetically differ from wild individuals because of domestication and possibly by ancestry, periodic domesticated-wild outbreeding has the potential to influence fitness-related traits in wild populations. In Atlantic salmon (Salmo salar), the understanding of mechanisms and direction of domesticated influences are especially important because of the conservation concerns associated with many wild populations, notably in the southern parts of their North Atlantic range. My thesis investigates domestication-induced, genetically based changes during the parr stage by assessing growth, parr maturity and survival under predation for three salmon strains differing in their history of domestication, as examined in two semi-natural environments (predator present, absent). Growth and size-at-age increased with increasing generations of domestication, yet male parr maturation probability declined. Survival under gape-limited predation increased with domestication-conveyed increases in size and growth rate. Domesticated but not wild individuals exhibited stress-resistant growth in the presence of a predator. To assess mechanism and magnitudes of trait changes resulting from domesticated-wild outbreeding, a domesticated strain was crossed with a wild population (up to third-generation hybrids) and outbreeding effects were studied for different life stages, several controlled environmental laboratory conditions, and traits. Life stages included the developmental periods between egg and fry, and between immature and adult post smolts. Traits assessed included survival, yolk conversion efficiency, size-at-age, maturation probability, growth rate, mRNA transcript levels and their environmental plasticity. For many traits, both additive and non-additive genetic components in the between-population genetic architecture were revealed by cross means analyses. Furthermore, maternal outbreeding effects on early life stages were present. Altogether the results indicate that constant outbreeding effects of escapees on wild populations will increase present growth rates during all life stages and decrease early maturation probabilities for male parr and post-smolts, but by unpredictable magnitudes across hybrid generations. Maternally controlled co-adapted traits might be disrupted in hybrid mothers. Further, mixed-origin individuals might be temporarily at an advantage relative to wild individuals because of size and growth advantages and these might accelerate a wild genotypes displacement.

A luminescence-based detection system was developed to study changes in the survival and activity of cells following release from moribund and dead fish. <I>A.salmonicida</I> was chromosomally marked with the genes encoding bacterial luciferase, originally isolated from <I>Vibrio harveyi</I>. Characterisation of the growth and luminescence of the <I>lux</I>-marked strain demonstrated that light was directly proportional to cell biomass concentration during logarithmic growth. The survival of <I>lux</I>-marked and wild type <I>A.salmonicida</I> strains was investigated in sterile sea water at 4°C. The number of culturable cells declined rapidly, but the total number of cells remained relatively constant, suggesting <I>A. salmonicida</I> entered a nonculturable state. The survival of <I>lux</I>-marked <I>A. salmonicida</I> did not significantly differ from that of the wild type strain. A small number of cells remained culturable throughout starvation experiments and luminometry confirmed that the <I>lux</I>-marked cells were metabolically active, possibly surviving by cryptic growth. The viability of putative dormant cells could not be established since these cells could not be reactivated following the addition of a range of substrates. The <I>lux</I>-marked <I>A.salmonicida</I> strain was pathogenic only when injected at high doses. This poor virulence was probably due to loss of the proteinaceous A-layer which is responsible for hydrophobic cell interactions and cell defence against lytic agents. This prevented further studies aimed at determining the virulence of nonculturable cells using this strain. Preliminary experiments indicated the potential of the <I>lux</I>-marked system for studying vertical transmission of <I>A. salmonicida</I>. The main sites for attachment of the <I>lux</I>-marked strain were the gill and skin/mucus regions. Identical results were obtained using a wild type <I>virulent A. salmonicida</I> strain, but significantly higher numbers of cells were recovered from fish tissue.

The use of automated salmon processing equipment in a factory has been shown to cause occupational asthma in the workforce by the generation of respirable aerosol contaminated with salmon protein. The affected individuals develop asthmatic symptoms and signs three weeks to three months after exposure. The diagnosis is made by clinical history, pulmonary function tests and the detection of specific serological markers. Affected individuals should be removed from exposure to aerosol to prevent the development of chronic asthma. A cross sectional survey demonstrated a prevalence rate of 8% in the exposed workforce. A nested case control study described the attributes of the cases. The chances of becoming a case were greatly increased by being a smoker [OR = 10.9] and less by being atopic [OR = 1.9]. Environmental hygiene measures to reduce aerosol from the gutting machines will reduce the problem but continued health surveillance of an exposed workforce is recommended to detect clinical and serological markers of disease.