Zhou Liran. / "June 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 182-216). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The fish ear contains three dense, bony bodies (otoliths) surrounded by fluid (the endolymph) and tissue. Under acoustic stimulation, the surrounding fluid and tissues oscillate relative to the otoliths, stimulating the endolymph as well as the array of hair cell cilia adjacent to the otolith and embedded in tissue. It is believed that the hair cell cilia move with the surrounding fluid. This doctoral thesis studied the steady streaming (i.e., time-independent) component of the acoustically induced fluid motion inside of the fish ear to determine how the hair cell cilia displacements due to the steady streaming could provide acoustically relevant information to the fish. This research characterizes the fluid flow around oscillating model otoliths, namely spheroids, grooved spheroids, and a 350% scale model of a cod saccular otolith. This study models the otolithic endorgan as an oscillating body in a Newtonian fluid. The model ignores the surrounding tissues and assumes that the hair cell cilia move like the surrounding fluid. Particle pathline visualizations and particle-image velocimetry (PIV) are used to characterize the flow fields at various oscillation orientations, frequencies and amplitudes. These data are used to determine the location of the stagnation points on the body surface and at the boundaries of the inner rotating region of the flow. Studies are also conducted on bodies sinusoidally oscillated at both a single frequency and two (simultaneous) frequencies along the same direction. Both the steady streaming flow patterns and velocity fields are found to contain acoustically relevant information, but given the very small displacements associated with these flows, it is unclear if the steady streaming flows can be sensed by the fish ear.

Made available in DSpace on 2014-08-13T14:50:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-27Bitstream added on 2014-08-13T18:00:58Z : No. of bitstreams: 1 000749629.pdf: 355801 bytes, checksum: 450e3ee8006d369b7cc1b731da7c1dfe (MD5) / Algumas espécies de peixe supostamente produzem e armazenam em células localizadas na epiderme (células ‘club’) substância de alarme que quando liberada na água induz respostas defensivas em coespecíficos. A substância de alarme não é secretada e só é liberada na água na ocorrência de um ataque de um predador que leva a injúria física da epiderme. Em situações de ameaça, ajustes fisiológicos são necessários para o organismo lidar com essa situação aversiva (resposta de estresse). Até o momento, as evidências sobre os efeitos da substância de alarme nas respostas de estresse em peixes permitem apenas uma restrita generalização, visto que poucas espécies foram avaliadas e tal estímulo pode induzir resposta primária e secundária de estresse ou não. No presente estudo, mostramos que a substância de alarme induz resposta primária de estresse, no que tange aumento na frequência ventilatória e nos níveis de cortisol, mas não secundária (aumento de glicose), divergindo das respostas de estresse em relação à substância de alarme relatadas. Isso sugere que esse fenômeno em peixes é espécie-específico

Orientador: Rodrigo Egydio Barreto / Banca: Augusto Barbosa Júnior / Banca: Gilso Luiz Volpato / Banca: Percília Cardoso Gianquinto / Banca: Tânia Marcia Costa / Resumo: Algumas espécies de peixe supostamente produzem e armazenam em células localizadas na epiderme (células 'club') substância de alarme que quando liberada na água induz respostas defensivas em coespecíficos. A substância de alarme não é secretada e só é liberada na água na ocorrência de um ataque de um predador que leva a injúria física da epiderme. Em situações de ameaça, ajustes fisiológicos são necessários para o organismo lidar com essa situação aversiva (resposta de estresse). Até o momento, as evidências sobre os efeitos da substância de alarme nas respostas de estresse em peixes permitem apenas uma restrita generalização, visto que poucas espécies foram avaliadas e tal estímulo pode induzir resposta primária e secundária de estresse ou não. No presente estudo, mostramos que a substância de alarme induz resposta primária de estresse, no que tange aumento na frequência ventilatória e nos níveis de cortisol, mas não secundária (aumento de glicose), divergindo das respostas de estresse em relação à substância de alarme relatadas. Isso sugere que esse fenômeno em peixes é espécie-específico / Abstract: Not available / Mestre

M.Sc. (Zoology) / Please refer to full text to view abstract

Studies were undertaken to determine the cardiac and ventilatory responses of restrained and unrestrained rainbow trout (Salmo gairdneri) to changes in inspired oxygen and carbon dioxide tensions. The role of blood oxygen carrying capacity in the control of ventilation was investigated, as well as the location and innervation of oxygen receptors activated by hypoxia. Ventilation volume (Vg) was measured directly in restrained fish using a ventilation chamber that separated inspired from expired water, the latter being collected in a graduated cylinder. In receptor localization experiments a wooden tongue depressor held vertically in the buccal cavity in the median plane divided water flows to the gills on each side of the fish. Thus, one set of gills could be irrigated with hyperoxic water to maintain arterial oxygen tension, while hypoxic water was passed over the other set of gills. Blood samples were obtained from cannulae implanted in both the dorsal aorta and right common cardinal vein. Vg increased in hypercapnea (inspired CO₂ tension (PICO₂) 0.5-2.0 kPa) due to increased "stroke volume (frequency remained constant), with higher levels of Vg recorded at higher C0₂ tensions. In fish exposed to PICO₂ levels of 0.5 and 0.9 kPa, raising the inspired oxygen tension (PIO₂) to 60.4 kPa eliminated the ventilatory response to hypercapnea. Hyperoxia had little or no effect on ventilatory responses to (PICO₂) levels of 1.5 and 2.0 kPa. Ventilation volume was inversely related to blood oxygen content (CaO₂) in trout. CaO₂ decreased and Vg increased during hypercapnea (PICO₂ 0.8 kPa), hypoxia (PIO₂12.4 kPa) and anaemia (haematocrit reduced from 22.3% to 14.3%), while CaO₂ increased and Vg decreased during hyperoxic hypercapnea (PIO₂ 60.4 kPa, PICO₂ 0.8 kPa). Increased Vg during hypercapnea is attributed to hypoxaemia produced by Bohr and Root off-shifts which result from increased blood CO₂ tension and reduced blood pH. Oxygen uptake remained constant during all experimental trials, indicating that the manoeuvre of increasing Vg is effective in relieving adverse effects of hypoxaemia. The significance of elevated Vg as a short-term adaptation to hypoxaemia is discussed, Heart rate decreased and ventilation increased in unrestrained fish exposed to gradual hypoxia (PIO₂ decreased from 20 kPa to 4 kPa) at 7°C and 16°C. The initial heart rate of fish acclimated to 16°C was higher than that of the 7°C group, but at the lowest level of PIO₂, heart rates of both groups dropped to the same level. Thus, the cardiac chronotropic response to hypoxia in trout is temperature independent. Receptors causing hypoxic bradycardia are located in the dorsal region of the first gill arch. Hypoxic bradycardia was eliminated by removing the first gill arch, or by sectioning the branches of cranial nerves IX and X innervating the arch. Blood flow through the arch does not appear to be necessary for this response, since ligation of the arch at its ventral insertion on the body wall did not affect hypoxic bradycardia. The pseudobranch has no role in cardiac control since interrupting the flow of blood through, and deafferentation of, the pseudobranch had no effect on the cardiac response to hypoxia. The biological significance of hypoxic bradycardia, and ventilatory-circulatory interaction during hypoxia, are discussed. Ventilatory responses to hypercapnea and hypoxia were unchanged after bilateral section of the nerves to the first gill arch. Receptors in the first gill arch thus have no role in control of ventilation during either hypercapnea or hypoxia. Possible locations for receptors responsible for control of ventilation are discussed. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

The construction of the Katse dam was completed in 1996. The dam started filling in 1995 and reached full capacity in early 1998. It forms part of Phase 1A of the Lesotho Highlands Water Project (LHWP). The main aim of the project is to provide revenue to Lesotho, by transferring water from the catchment of the Senqu (Orange) River in Lesotho to South Africa’s major industrial and population centres. During the implementation of the project, an estimated 130 people were displaced. However, the most serious impact has been the loss of the traditional way of life in the form of arable and grazing land as a consequence of inundation. One of the obligations of the project is to ensure that the standard of living of those affected by the project is not impaired. The Lesotho Highlands Development Authority identified a number of rural development projects, which included fisheries development. This study is an integral part of fisheries development in Lesotho. The aim of this study was to gain an understanding of the biology and the demographics of the fish species in the lake. This information would serve as the basis for the development of a management plan for the sustainable utilisation of the fisheries resources. To achieve this aim, the following specific objectives were addressed: 1. Investigation of the biology of the three principal species. 2. Description of the key population parameters (growth, mortality & recruitment). 3. Investigation of the distribution and relative abundance of the three species. The three principal species in the Katse dam are rainbow trout, Oncorhynchus mykiss, and the two cyprinids, Barbus aeneus and Labeo capensis. Sectioned otoliths were used to age O. mykiss while both otoliths and scales were used to age B. aeneus and L. capensis. Marginal zone analysis revealed that slow growth was experienced in winter for the three species. The maximum-recorded age for both B. aeneus and L. capensis was 12 years while O. mykiss reached 4 years. There was no significant difference in growth rates of the different sexes and growth was best described by the 3 parameter Von-Bertalanfy growth model as Lt = 603[1-e⁻°·¹⁵⁽t ⁺ °·°³⁾] for B. aeneus, Lt = 526[1-e⁻°·²¹⁽t ⁺ °·⁹⁾] for O. mykiss and Lt = 521[1-e⁻°·¹⁷⁽t ⁺ °·²¹⁾] for L.capensis. Male and female O. mykiss attained 50% sexual maturity (Lm₅₀) at 235 and 275mm FL, respectively. There was no difference in Lm₅₀ for male and female B. aeneus and L. capensis. B. aeneus reached sexual maturity at 285mm FL while L. capensis reached sexual maturity at 244mm. Both cyprinid species spawned in summer (November to January) while O. mykiss spawned in winter (May to August). The mean total mortality rate (Z) estimated from catch curves and Butterworth et al (1989) equation was 0.72 yr⁻¹ for B. aeneus, 0.62 yr⁻¹ for L. capensis and 1.32 yr⁻¹ for O. mykiss. The estimate of natural mortality was 0.41 yr⁻¹ for both B. aeneus and L. capensis and 0.81yr⁻¹ for O. mykiss.

Fisheries management regulations for dusky kob Argyrosomus japonicus, an important commercial and recreational fisheries species, have failed and the stock is considered collapsed. It is important to take an ecosystems approach to management which includes understanding the effect of environmental factors on recruitment, abundance and distribution. The distribution of early juveniles (20-150 mm TL) in the wild appears to be restricted to the upper reaches of estuaries at salinities below 5 psu. Food availability could not explain the distribution of early juveniles. The aim of this study was to investigate the role of salinity on the distribution of early juvenile dusky kob (<150 mm TL) by examining physiological responses of juveniles exposed to a range of salinities under laboratory conditions. The hypothesis was that the physiological functioning of early juveniles would be optimised at the reduced salinities which they naturally occur at. The objectives of this study were to investigate the effect of salinity on: i) plasma osmolality; ii) growth, food conversion ratio and condition factor; and iii) gill histology with emphasis on chloride cell size and number. A preliminary study was undertaken to determine whether the use of 2-phenoxyethanol had an effect on plasma osmolality. Juveniles pithed prior to blood sampling were used as the control. Plasma osmolality was not affected by exposure or duration of exposure (2, 4, 6, 8, 10 min) to 2-phenoxyethanol. The ability of teleosts to regulate plasma osmolality over a wide range of salinities indicates their degree of ‘physiological euryhalinity’. Plasma osmolality of juveniles exposed to 5, 12 and 35 psu was measured every two weeks over a total of six weeks. Although juveniles were able to regulate plasma osmolality over the duration of the experiment, plasma osmolality at 5 and 12 psu was significantly lower than in fish maintained at 35 psu. Growth is used as an indicator of the relative energy used for osmoregulation at different salinities, as the energy used for osmoregulation becomes unavailable for growth. A nineweek growth experiment was conducted on juveniles exposed to 5, 12 and 35 psu. Juveniles grew and survived at all three salinities. However, growth of juveniles at 5 psu was significantly lower than at 12 and 35 psu. Other than a significantly greater weight gain at 35 psu relative to 12 psu, there was no significant difference in specific growth and length gain between juveniles at 12 and 35 psu. Food conversion ratio and condition factor at 12 and 35 psu were not significantly different, but food conversion ratio and condition factor at 5 psu was significantly greater and lower than at 35 psu respectively. In fish, gills are considered the major organ involved in osmoregulation. Within the gills, chloride cells are the predominant site of ion exchange which is driven by the Na⁺, K⁺- ATPase enzyme. Gill samples of juveniles exposed to 5, 12 and 35 psu for six weeks were examined histologically using light microscopy. Chloride cells of juveniles maintained at 5 psu were significantly more abundant than in juveniles at 12 and 35 psu. Chloride cells of juveniles at 5 psu were significantly larger than in juveniles kept at 12 psu, but not significantly different to those of juveniles kept at 35 psu. The ability of the juvenile fish to regulate plasma osmolality indicates that they are 'physiologically euryhaline', but the reduced growth and proliferation of chloride cells at 5 psu suggests that energy expenditure for osmoregulation is increased at hypoosmotic salinities. Salinity induced physiological responses could therefore not explain the natural distribution of early juvenile dusky kob and it is proposed that other environmental factors (e.g. temperature) are also important. It is also hypothesised that the high conductivity of an estuary in South Africa, to which our understanding is limited, may negate the effect of reduced salinity. Although freshwater input into estuaries is an important factor, further investigations to explain the distribution and abundance of early juveniles is required to make management recommendations. Dusky kob is also becoming an increasingly popular aquaculture species in South Africa. In this regard, early juvenile dusky kob can be grown at salinities as low as 12 psu without negatively affecting growth and production.

To contribute to the understanding of the invasion biology of common carp Cyprinus carpio in southern Africa, this thesis investigated the life history, relative abundance, long-term population demographics and trophic niche utilisations of non-native common carp C. carpio in relation to two endemic cyprinids, Orange River mudfish Labeo capensis and smallmouth yellowfish Labeobarbus aeneus in South Africa‟s largest impoundment, Lake Gariep. The growth zone deposition rates in astericus otoliths of the three species were validated as biannual for C. carpio and as annual for L. capensis and L. aeneus, which allowed for reliable estimation of lengths-at-age upon which growth, age-at-maturity and mortality rates could be estimated. Cyprinus carpio exhibited fast growth, matured relatively early at two years of age and attained a maximum age of seven years. Labeo capensis grew significantly slower, but attained older ages of up to 12 years. Females showed notably delayed maturation at approximately six years of age. The life history parameter estimates for L. aeneus were similar to those of L. capensis. These species-specific life history characteristics contributed to a substantially higher population growth potential of C. carpio compared to L. capensis and L. aeneus. Delta-lognormal and delta-gamma Generalized Linear Models (GLMs) were used to analyse patterns of relative abundance of L. capensis, L. aeneus and C. carpio. The application of these GLMs was necessary to account for large proportions of zeros and strong skewness in the catch-per-unit-effort (CPUE) from experimental gillnet and fisheries-dependent angler surveys. Confidence intervals around predicted abundance indices were obtained through the development of a generalised parametric bootstrap procedure. The resulting standardised abundance indices were coupled with results from analysis of stable isotope ratios of fish tissues and potential food resources and revealed that C. carpio was mainly confined to soft-bottom habitats, where it predominantly foraged on benthic invertebrates. Labeo capensis was abundant in a wide range of benthic habitats and was consumed basal food resources such as detritus. Labeobarbus aeneus was found to feed mostly on pelagic zooplankton. There were no significant interspecific differences in trophic niche space, suggesting limited resource competition among the three species. Standardised historical and contemporary gillnet CPUE data indicated slow population growth rates of L. capensis and L. aeneus during the first ten years postimpoundment, but showed high biomass levels some four decades after impoundment. These results could be corroborated by stochastic age-structured production model (ASPM) simulations. In contrast to the two endemic species, the gillnet CPUE of C. carpio showed a clear „boom and bust‟ pattern, which, based on ASPM simulations, could be best explained by increased food availability during the first five years postimpoundment, followed by suboptimal conditions thereafter. Together, these results provided evidence that the establishment of the C. carpio population did not prevent the slow but successful long-term establishment of the two large endemic cyprinids. Both endemic fishes revealed specialised feeding within the impoundment.