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Crosses were made between a stock of summer steelhead (Salmo gairdneri) known to be resistant to infection by Ceratomyxa shasta and stocks of summer steelhead known to be susceptible. Ceratomyxosis, the disease caused by C. shasta was initiated by exposure to Willamette River water. I found that the crosses were intermediate in susceptibility to ceratomyxosis relative to the parental stocks. There was no difference in susceptibility to ceratomyxosis between reciprocal crosses of the same stocks. Persistence of moderate susceptibility in the F₂ generation of experimental stock crosses and examples from both wild and hatchery stocks of mixed ancestry indicate long term disease problems may result from introductions of less adapted, foreign stocks. / Graduation date: 1987

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Lam Chu-Wah. / Thesis (M.Comm.)--Chinese University of Hong Kong, 1968. / Includes bibliographical references (leaves 97-99).

Chau Wing-sze. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 238-262). / Abstracts in English and Chinese. / Abstract (in English) --- p.i / Abstract (in Chinese) --- p.iv / Acknowledgement --- p.vi / Contents --- p.ix / List of Figures --- p.xv / List of Tables --- p.xvi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Introduction of samples --- p.2 / Chapter 1.3 --- Flavor of Chinese salted-dried fish --- p.4 / Chapter 1.4 --- Objectives of the study --- p.5 / Chapter 2. --- Literature review --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Volatile compounds in fresh fish --- p.8 / Chapter 2.2.1 --- Groups of volatile compounds --- p.9 / Chapter 2.2.2 --- Variation in fresh fish flavor --- p.12 / Chapter 2.2.2.1 --- Intrinsic factor --- p.12 / Chapter 2.2.2.2 --- Environmental factors --- p.15 / Chapter 2.2.2.3 --- Post harvest conditions --- p.16 / Chapter 2.3 --- Fish preservation --- p.17 / Chapter 2.3.1 --- Preservation methods --- p.18 / Chapter 2.3.1.1 --- Drying --- p.19 / Chapter 2.3.1.2 --- Salting --- p.19 / Chapter 2.3.1.3 --- Fermentation --- p.21 / Chapter 2.3.2 --- Theory of drying and salting --- p.21 / Chapter 2.3.3 --- Different protocols in the world --- p.23 / Chapter 2.3.3.1 --- European methods --- p.24 / Chapter 2.3.3.2 --- Southeast Asian methods --- p.25 / Chapter 2.3.3.3 --- Thai methods --- p.27 / Chapter 2.3.3.4 --- Chinese method --- p.28 / Chapter 2.3.3.5 --- Local method --- p.29 / Chapter 2.3.4 --- Consumption procedures --- p.31 / Chapter 2.3.5 --- Advantages of drying besides preservation --- p.31 / Chapter 2.3.5.1 --- Convenience in transportation --- p.32 / Chapter 2.3.5.2 --- Flavorization --- p.32 / Chapter 2.3.5.3 --- Nutritional values --- p.33 / Chapter 2.4 --- Flavor of salted-dried fish --- p.34 / Chapter 2.4.1 --- Taste of salted-dried fish --- p.35 / Chapter 2.4.2 --- Aroma of salted-dried fish --- p.35 / Chapter 2.4.3 --- Flavor of Chinese salted-dried fish --- p.37 / Chapter 2.4.4 --- Parameters affect the flavor and quality of salted-dried fish --- p.38 / Chapter 2.4.4.1 --- Freshness --- p.38 / Chapter 2.4.4.2 --- Temperature --- p.39 / Chapter 2.4.4.3 --- Post harvest freezing and thawing --- p.40 / Chapter 2.4.4.4 --- Gutting --- p.42 / Chapter 2.4.4.5 --- Salt quality --- p.43 / Chapter 2.5 --- Biological deterioration in salted fish --- p.46 / Chapter 2.6 --- Salted-dried fish in Hong Kong --- p.47 / Chapter 3. --- Materials and methods --- p.55 / Chapter 3.1 --- Materials --- p.55 / Chapter 3.1.1 --- Abbreviation of names of samples --- p.55 / Chapter 3.1.2 --- Handling of samples --- p.56 / Chapter 3.2 --- Method --- p.58 / Chapter 3.2.1 --- Modified Simultaneous steam distillation-solvent extraction (SDE)-Steaming --- p.58 / Chapter 3.2.2 --- Concentration --- p.59 / Chapter 3.2.3 --- Gas chromatography-mass spectrometry (GC-MS) --- p.59 / Chapter 3.2.4 --- Compound identification --- p.60 / Chapter 3.2.5 --- Quantification of compounds --- p.60 / Chapter 3.2.6 --- Moisture analysis --- p.62 / Chapter 3.2.7 --- Texture analysis --- p.62 / Chapter 3.2.8 --- Statistical analysis --- p.63 / Chapter 3.2.9 --- OAV calculation --- p.64 / Chapter 4. --- Results and Discussion --- p.66 / Chapter 4.1 --- Threadfin --- p.66 / Chapter 4.1.1 --- Overall description of volatile compounds in salted-dried threadfin --- p.66 / Chapter 4.1.2 --- Characteristic compounds in delayed (D) groups of samples --- p.68 / Chapter 4.1.3 --- Characteristic compounds in regular (R) groups of samples --- p.70 / Chapter 4.1.4 --- Common compounds found in the eight groups of samples --- p.71 / Chapter 4.1.5 --- Comparison of common compounds among individual groups of salted-dried fish --- p.78 / Chapter 4.1.5.1 --- Comparison between delayed and regular salting methods --- p.78 / Chapter 4.1.5.2 --- Comparison between locations of purchase --- p.80 / Chapter 4.1.5.3 --- Comparison between samples from different years (2000 and 2001) --- p.81 / Chapter 4.1.6 --- Exclusive compounds found in delayed salted (D) or regular salted (R) fish --- p.83 / Chapter 4.1.7 --- Conclusion of threadfin --- p.84 / Chapter 4.2 --- White herring --- p.85 / Chapter 4.2.1 --- Overall description of volatile compounds in salted-dried white herring --- p.85 / Chapter 4.2.2 --- Characteristic compounds in delayed (D) groups of samples --- p.87 / Chapter 4.2.3 --- Characteristic compounds in regular (R) groups of samples --- p.88 / Chapter 4.2.4 --- Common compounds found in the eight groups of samples --- p.89 / Chapter 4.2.5 --- Comparison of common compounds among individual groups --- p.94 / Chapter 4.2.5.1 --- Comparison between delayed and regular salting methods --- p.94 / Chapter 4.2.5.2 --- Comparison between locations of purchase --- p.96 / Chapter 4.2.5.3 --- Comparison between samples from different years --- p.97 / Chapter 4.2.6 --- Conclusion of white herring --- p.98 / Chapter 4.3 --- Pawak croaker --- p.100 / Chapter 4.3.1 --- Overall description of volatile compounds in salted-dried pawak croaker --- p.100 / Chapter 4.3.2 --- Characteristic compounds in delayed (D) groups of samples --- p.102 / Chapter 4.3.3 --- Characteristic compounds in regular (R) groups of samples --- p.105 / Chapter 4.3.4 --- Common compounds found in the eight groups of samples --- p.106 / Chapter 4.3.5 --- Comparison of common compounds among individual groups of salted-dried fish --- p.111 / Chapter 4.3.5.1 --- Comparison between delayed and regular salting methods --- p.111 / Chapter 4.3.5.2 --- Comparison between locations of purchase --- p.114 / Chapter 4.3.5.3 --- Comparison between two batches of samples from different years --- p.115 / Chapter 4.3.5.4 --- Characteristic compounds of pawak croaker --- p.117 / Chapter 4.3.6 --- Conclusion of pawak croaker --- p.118 / Chapter 4.4 --- Overall comparison of compounds of the three species --- p.120 / Chapter 4.4.1 --- Introduction --- p.120 / Chapter 4.4.2 --- Comparison of three species of fishes --- p.121 / Chapter 4.4.2.1 --- Delayed- and regular- smell contributors --- p.122 / Chapter 4.4.3 --- The difference among the groups of fishes --- p.123 / Chapter 4.4.3.1 --- Effect of different body compositions of fishes --- p.124 / Chapter 4.4.3.1.1 --- Lipid originated volatile aldehydes --- p.125 / Chapter 4.4.4 --- Common compounds detected in all three species of salted-dried fishes --- p.126 / Chapter 4.4.4.1 --- Compounds with high calculated aroma values (OAV) --- p.127 / Chapter 4.4.4.2 --- Compounds with low calculated aroma values (OAV) --- p.130 / Chapter 4.4.5 --- Effect of treatment methods --- p.132 / Chapter 4.4.6 --- Effect of locations of collection of samples on the composition --- p.134 / Chapter 4.4.7 --- Effect of time of collection of samples on the composition --- p.135 / Chapter 4.4.8 --- Characteristic compounds found only in one species --- p.135 / Chapter 4.4.8.1 --- Characteristic compounds of threadfin --- p.136 / Chapter 4.4.8.2 --- Characteristic compounds of white herring --- p.136 / Chapter 4.4.8.3 --- Characteristic compounds of pawak croaker --- p.138 / Chapter 4.5 --- Texture --- p.139 / Chapter 4.5.1 --- Introduction --- p.139 / Chapter 4.5.2 --- Results and Discussion --- p.141 / Chapter 4.5.2.1 --- Comparison between regular and delayed salted-dried fishes --- p.141 / Chapter 4.5.2.1.1 --- Effects of enzymatic reaction --- p.141 / Chapter 4.5.2.1.2 --- Effects of fermentation --- p.142 / Chapter 4.5.2.1.3 --- Frozen period before regular salting --- p.143 / Chapter 4.5.2.2 --- Comparison between raw and steamed salted-dried fishes --- p.145 / Chapter 4.5.2.3 --- Moisture content of salted-dried fishes --- p.146 / Chapter 4.5.3 --- Conclusion --- p.147 / Chapter 5. --- Conclusion and Significance --- p.233 / Chapter 5.1 --- General conclusion --- p.233 / Chapter 5.2 --- Significance of the study --- p.235 / References --- p.238 / Appendix I --- p.263 / Appendix II --- p.264

University of Technology, Sydney. Faculty of Science. / In the last 100 years there have been dramatic declines in the range and abundance of native freshwater fish in south-eastern Australia. These declines have been attributed to habitat loss and degradation (including river regulation, water quality, erosion/siltation, instream cover and riparian vegetation), alien fish species, overfishing, and the obstruction of fish passage. In south-eastern Australia there are 86 species of freshwater fish and 36 of these have some migratory component of their life history that requires free passage along streams. The migrations of these fish in this region have been inhibited or prevented by the existence of more than 1500 dams and weirs. To mitigate this impact there are only 69 fishways. Most of these fishways are based on designs suitable for the swimming ability and behaviour of salmonids from the Northern Hemisphere. There are, however, no native salmonids in Australia. I assessed one of these salmonid fishways, at Euston on the Murray River, for its suitability for passing native fish. Fish were trapped at the top and bottom of the fishway over eight paired days. Although this fishway has one of the lowest slopes of the older fishways, and therefore potentially one of the easiest to ascend, very few of the fish that entered the fishway could get to the top. For example, 777 +/- 238 [x +/- s.e.] golden perch (Macquaria ambigua) per day entered the fishway but only 4 +/- 2 per day were collected at the top of the fishway. This and other data highlighted two points: i) the ineffectiveness of the salmonid-type fishways for native fish; and ii) assessing fishways by counting fish at the top only, although widely used throughout the world, is insufficient to assess the performance of a fishway. Counts of fish from the top of a fishway can, however, be useful to monitor fish populations over time. An excellent example of this is provided by long-term monitoring of the Euston fishway, which shows massive declines in the upstream movements of silver perch (Bidyanus bidyanus), Murray cod (Maccullochella peelii peelii) and Macquarie perch (Macquaria australasica) between 1940-45 and 1987-90, indicating corresponding declines in the populations of these species. The failure of salmonid fishways for non-salmonid fishes has been a common experience throughout the world. It stems partly from a lack of knowledge of the migratory patterns of non-salmonid fish, and from a lack of quantitative experimental research into the swimming ability and behaviour of these fish in fishways. To redress this situation for south-eastern Australia, I tested fish in experimental fishways in a hydraulics laboratory. The fishway design tested was the vertical-slot fishway, which is a pool-type fishway where water flows between each pool via a vertical slot. The design was considered to potentially suit the hydrology of Australian rivers and the behaviour of native fish. For these experiments I selected fish species and life stages representative of the migratory fish fauna of the two major drainages of south-eastern Australia. For the south-eastern coastal rivers I chose juvenile Australian bass (Macquaria novemaculeata)[mean lengths of 40, 64 and 93 mm] and barramundi (Lates calcarifer) [43 mm]. These two species are catadromous, with the adults migrating downstream to the estuary to breed and the juveniles migrating upstream. For the large inland Murray-Darling river system I chose adult golden perch (Macquaria ambigua) [441 mm] and silver perch(Bidyanus bidyanus) [258 mm]. At the beginning of this study, adults of these two species were considered to be the main life stage migrating upstream. In the laboratory experiments fish were tested at different water velocities and probit analysis was applied to the proportion of fish that negotiated these velocities. I used this approach to produce values which I called the NV90 and the NV95, which are the maximum water velocities that 90% and 95% of the fish could negotiate in the fishway. For bass, barramundi and golden perch these values ranged from 0.7 to 1.8 m s-1. These values are well below the standard maximum water velocity for salmonid fishways of 2.4 m s-l. The silver perch results were too variable to analyse. The data obtained from the laboratory experiments were used by water resource agencies to build eight new vertical-slot fishways in coastal and inland rivers of southeastern Australia. One of the largest of these new fishways was at Torrumbarry Weir on the Murray River, which consists of 38 pools, each 3 m long, ascending a 6.5 m high weir. The fishway, if successful, would provide access to 350 km of habitat above the weir. To determine whether or not the fishway was successful in passing native migratory fish it was assessed for 2.5 years by: i) sampling monthly above and below the fishway with a standard set of independent, replicated nets; and ii) sampling within the fishway. The netting showed that there were major aggregations of migratory fish below the weir when the fishway was not operational. However, when the fishway was completed and operational, 13 months after the commencement of sampling, there were no further major aggregations of migratory fish below the weir. These data, combined with high numbers of fish successfully ascending the fishway, indicated the success of this vertical-slot fishway design. It was estimated that from February 1991 to June 1993 20,7 14 native fish and 16,595 alien fish (all carp [Cyprinus carpio]) had successfully ascended the fishway. Sampling at the top and bottom of the fishway showed that the fishway passed almost all the species and sizes classes of native migratory fish, except for Australian smelt (Retropinna semoni). The latter is a small species 15 to 40 mm long that only entered the lower few pools of the fishway. The widespread distribution of this species indicates the migration is facultative. Experiments within the fishway showed that the laboratory experiments had underestimated swimming ability. However, it was discovered that fish still needed over 1.5 hours to ascend the full length of the fishway. In addition, some species only migrated upstream during daylight and if their ascent of the fishway was not completed in daylight the fish moved back down the fishway. I concluded that the original water velocity criterion from the laboratory experiments was appropriate and that future fishways need to consider ascent time and fishway length as well as water velocity. I also concluded that it is more difficult to obtain realistic results from 'off-site' experiments, where fish are transported to a laboratory or other facility, than from in situ experiments where naturally migrating fish are used and are not handled until the end of the experiment. Sampling at Torrumbarry Weir provided detailed information on the biology of the migratory fish species, which is essential to designing effective fishways. Carp(Cyprinus carpio), an introduced or alien species, and bony herring were newly identified as migratory, and golden perch and silver perch were confirmed as migratory. A major finding was that 95% of golden perch and 87% of silver perch moving upstream were immature fish. Previously the upstream movement of immature fish in this river system was considered insignificant. Fortunately the conservative water velocities in the Torrumbarry fishway accommodated these smaller fish(approximately 100 to 300 mm in length). The reason for the large numbers of immature fish migrating upstream is not clear, but it may be to optimise feeding, enhance colonisation, or to compensate for the downstream drift of the pelagic eggs and larvae. Migration of all species was seasonal. Spring, summer and early autumn were the main periods of upstream movement for native fish, and carp moved upstream in spring and early summer. Migration of carp was stimulated by rising water temperature only, but golden perch and silver perch were stimulated to move upstream by small changes in river levels. This small scale variation in streamflow is frequently suppressed by river regulation, and this is likely to have contributed to the significant decrease in the numbers of migrating native fish. Upstream migration of all species often occurred during low flows, as well as higher flows. This also occurs in coastal rivers of southeastern Australia. For both the coastal and inland rivers of this region it will be important to design fishways and environmental flow releases to accommodate this aspect of fish migration and the often semi-arid hydrology of these streams. Golden perch and silver perch were aged using sagittal otoliths and validated using known-age fish. The data showed that the immature fish were all over one year old, suggesting that younger fish are not migrating upstream. More research is needed to determine the location and habitats of the less than one year old fish. Ageing and examination of gonads indicated the size and age at maturity for these fish. This suggested that minimum size limits currently used to regulate the recreational fishery are not allowing fish to reach maturity. Golden perch and silver perch were found to be long-lived fish, up to 26 and 27 years respectively. Interestingly, samples of these two species from other rivers within the Murray-Darling river system show that the maximum sizes of these fish can vary significantly between rivers, suggesting that the ecology of different rivers within this large river system varies considerably. The development of fishways for non-salmonid fishes throughout the world has frequently met with failure. From the work in the present study and from reviewing other work I suggest there are five steps for the development of effective fishways. 1. Determine which fish species are migratory: - it is important to identify the smallest and largest fish that are migratory, as this affects the initial choice of the size of the fishway to test. 2. Test fish in an experimental fishway: - in situ experiments are recommended; - avoid handling of fish before and during experiments. 3 Design the fishway: - first decide on the location of the fishway entrance; - extrapolate research results with caution; - do not reduce pool sizes from the experimental model; - avoid tunnels; - design the fishway to operate over the full range of flows during which fish migrate. 4. Link the fishway with the operation of the dam or weir: - maintain flow and temperature regimes that stimulate migration; - manage flow releases over the spillway to guide fish to the fishway entrance. 5. Assess the fishway: - use quantitative and relevant performance criteria to assess the fishway and not only counts of fish from the top of the fishway. The most common strategy in the past has been to design the fishway and ignore steps 1, 2, 4 and 5. With fishways being increasingly recognised as important tools in the rehabilitation of aquatic biota in temperate river systems, and as a potential tool in the development of water resources in tropical rivers, it is essential that they are appropriately designed, constructed, and assessed. Otherwise the mistakes of the past will very likely be repeated.

Numerous natural and anthropogenic chemicals interact with endocrine systems of animals. The most widely studied of these endocrine active chemicals (EACs) are estrogen receptor agonists and antagonists. Because of the many important roles of estrogens in animals, xenoestrogens have the potential to impact environmental health. It has been proposed that xenoestrogen contaminants are responsible for recent increases in estrogen dependent human diseases and sexual and developmental abnormalities in wildlife. Aquatic species are particularly susceptible to persistent EACs that accumulate in sediments and biomagnify along trophic levels. Rainbow trout, Oncorhynchus mykiss, commonly used in biomedical research and as a sentinel species, was chosen as a model for studying mechanisms of xenoestrogen activity. The aims of this research were to assess the estrogenic activity of individual persistent, organic contaminants and simple mixtures in vivo. Emphasis was placed on determining the potential for xenoestrogens to alter sexual development or to induce sexually dimorphic biochemical responses. Gonadal abnormalities in trout exposed as embryos to the xenoestrogen o,p'-DDE showed that xenobiotics can affect trout sexual development. However, the absence of endocrine disruption by low doses of o,p'-DDE, by the xenoestrogens chlordecone and octylphenol, or by the anti-androgen p,p'-DDE, suggested that lethality is likely to precede endocrine disruption in highly exposed, feral salmonid populations. Sexually distinct responses in immature trout were documented with respect to vitellogenin induction (2 to 4 fold higher in females) and cytochrome P450 expression. Sex differences occurred only when doses of estrogens or xenoestrogens were below levels that cause maximal estrogenic responses. Evidence suggests that estrogen regulation may be fundamentally different in immature males and females, which may have implications for natural populations exposed to xenoestrogens. Vitellogenin induction and P450 modulation were responsive to mixtures of estrogens and xenoestrogens in a manner suggestive of additive activation of estrogen receptors. Cytochrome P450 dependent induction of lauric acid hydroxylation was observed for the first time in trout, in response to tamoxifen and mixtures of tamoxifen and 17��-estradiol. The estrogenic activity of tamoxifen and 4-hydroxy-2',4',6'-trichlorobiphenyl were greater in vivo than what was predicted by in vitro studies, which emphasized the need for mechanism based investigations of xenoestrogens in whole organisms. / Graduation date: 1999