Tuna fisheries in the coastal states of the West Indian Ocean (WIO) have been at the centre of the social, economic and political development of the region. Their significance in creating employment, providing food, and generating revenue for the people in the region cannot be overemphasized. To be able to derive full benefits from the tuna resources in the WIO, the coastal states will have to devise an efficient management strategy, not individually, but collectively. Currently, there is no such management structure in the region to accomplish this goal. This study is, therefore, an attempt to find some solution to this important issue, and to propose a suitable management framework that would guarantee an efficient and profitable tuna resource management mechanism in the region. To tackle this task, data were collected through documentary statistical sources as well as by the use of questionnaires. Information was received from many fisheries organisations, as well as from other international fishing institutions. The results show that there is an urgent need for a regional organisation to manage tuna resources in the WIO, in order to avoid overfishing and stock depletion which will have adverse consequences on the economic and development prospects of both the coastal states and distant water fishing nations (DWFNs) operating in the region. This study recommended the establishment of a "Regional Organisation for the Management of Tuna in the West Indian Ocean" (ROMTWIO) using a contingency-political model in recognition of the need for a systems organisational structure that reflects the political elements in the region. The organisation should address the issues of joint co-operation in self-determination and self-management of tuna resources in the region within the remit of existing international laws, and in recognition of the significant role other international bodies can play in the realisation of the benefits of a common tuna resources for all.

This study of the fish and fishery of Stocks Reservoir, Lancashire, is the result of contract work undertaken by the researcher for North West Water (NWW). In an attempt to describe the location of the study, relevant information covering the catchment, local geology, reservoir construction and flora and fauna is included.The Authority's remit suggested a study of three facets of the catchment, namely, a study of the native fish populations, a monitoring of the recently opened fishery and an analysis of operational filter plate impingement.In order to minimise disturbance of the sport fishery, native fish population work was necessarily limited to the reservoir's three major afferent streams, the River Hodder, Hasgill Beck and Bottoms Beck.As a preliminary measure of tributary stream status, a simple invertebrate site study was undertaken by the researcher in 1985.Fish population work based on catch per unit effort (CPUE) was pursued in the spring, summer and winter of 1985, 1986 and 1987 at 8 sites, employing D. C. electric fishing equipment, whilst Carle and Strub's (1978) MWL Method was adopted for population estimations. The validity of the electric fishing survey and age determination are discussed in the text.The native species of brown trout, bullhead, stone loach and minnow were encountered, as was the introduced rainbow trout. Species densities and the population structure of the native brown trout were examined in detail for each survey site. The River Hodder was revealed to be the least populous tributary, whilst Hasgill Beck exhibited the greatest fish densities. Spawning migrations of native brown trout were evident, with fry recruitment at its optimum at site 4 on Hasgill Beck and site 8 on Bottoms Beck. The waterfall on Bottoms Beck might well have precluded upstream access to the head waters of this tributary. Observed mean brown trout length for age data were similar to those recorded by authors researching other upland stream locations.The history of Stocks Reservoir as a sport fishery is outlined prior to the present leaseholder's opening of the reservoir as a day ticket fly fishery for the 1985 season. The water was stocked predominantly with rainbow trout, together with some brook trout and brown trout before fishing commenced.The present study covering the seasons 1985 to 1987 was based primarily on data abstracted from catch return forms, which displayed a notably high rate of submission, and stocking consent data provided by NWW. The validity of return form data is discussed.Over the three seasons studied, angler patronage was observed to decline by 16%, whilst the number of fish caught and taken also declined by 34.8% and 20.5% respectively. Angler success was similarly observed to decline in accord with the decrease in patronage and catches. Interestingly, there was an increased reliance on introductions of rainbow trout over the period, including larger fish, and by 1987 a cessation in the stocking of other trout species.From correlations observed between environmental parameters and angler patronage, anglers appeared to prefer fishing in dry, sunny conditions, but decreases in angler success occurred during periods of increased water turbidity. Such declines in success also displayed congruity with decreases in angler patronage.From a comparison undertaken with a cross-section of English and Welsh stillwater trout fisheries, Stocks Reservoir was judged to rate poorly, returning the lowest performance data in the upland stocked category.An examination of the stomach and hind gut contents of 127 rainbow trout, 7 brook trout and 8 brown trout caught by anglers, was undertaken in the 1985 and 1986 seasons, and was compared with the reservoir fauna data of Mills, M. L. (1971).A description of the water treatment plant and its operation is delineated, and a pertinent collection of fish impingement and screening literature is included.Impingement data were collated from lst March 1985 to 31st December 1987 from routine and emergency cleaning of the filter plates. After storage in a freezer, the thawed fish were examined chronologically, identified, measured and weighed. During the examinations a random sample of stomach and hind guts was procured, and scales from brown trout were removed for possible future reference.The total annual impingement was observed to vary considerably, although brown trout habitually exhibited the greatest losses, comprising 71%, 64% and 89% of fish impinged annually. Of the introduced species, rainbow trout and brook trout, brook trout were the more susceptible to impingement, but remarkably few rainbow trout were lost considering the number stocked.Rainbow trout and brook trout of medium (150mm to 300mm) and large (>300mm) length classes were impinged, whereas many smaller (<150mm) brown trout were lost, a phenomenon concurrent with the recruitment of juvenile stream fish to the reservoir population.Brown trout in particular exhibited an annual dissimilarity in rates of impingement, probably suggesting that seasonal migration was not causative of their increased impingement.Impingement of rainbow trout showed limited correlation with environmental parameters. In 1985 and 1986, increased impingement of both brown trout and brook trout was significantly correlated with low reservoir levels, and to some extent might be linked to rising values of water turbidity.The collecting of stomach and hind gut samples from impinged fish was discontinued after 1985 because of problems in collection associated with delays in sampling and probable regurgitation of stomach contents. The problem of eye fluke infestation in impinged fish was noted and enumerated as sampling progressed.A brief discussion of further routes of operational fish loss from the reservoir is included.

In Taiwan, the history of aquaculture spans over three hundred years and the breakthroughs in the artificial propagation of finfish and shrimp effectively reduced the industries' reliance on wild fry, thereby stabilizing commercial operations and overcoming the barriers for expansion. Taiwan is located very close to Japan, one of the biggest seafood importers in the world, which has also benefited the development of aquaculture. However, the growing problems of water pollution and the increasingly high environmental costs generated by aquaculture ventures have made Taiwan experience a declining trend in recent years. To overcome those constraints, three main areas are described, which then form the basis of this study. (1). Adjustment of existing production practices - Milkfish culture, one of the most vulnerable sectors suffering from price fluctuation is used as an example to understand both the production cost, market attributes and the ways in which impacts of variations between production and price can be reduced. (2). Improving existing systems - One of the methods to reduce the use of underground water is to use super intensive culture in which high densities are stable and water use minimised, and has been tried in Taiwan for eels. However, the cost and benefits must be evaluated and as most eel products are exported to the Japanese market, it is very important to examine the comparative advantages against other countries. (3). Develop new systems- One of the solutions to the constraints of land-based aquaculture in Taiwan is to develop seawater-based cage culture. This has been developed in a limited degree in Ping-Tong and Pen-Hu counties but the feasibility and profitability have not been investigated. Based on 274 milkfish farms, 63 traditional eel farms, 5 intensive eel farms, 22 cage culture farms and 133 consumers from different zones, constituted the primary data, which combined with other secondary data constructed this investigation. The milkfish sector was not economically sound. Farm size in the categories of 4-<5 ha could appear to be more profitable. Cold weather and unstable in price made this industry more risky. The price was very unstable and strongly correlated to seasonal variation of production. The various forms of average financial appraisal have shown that intensive eel culture has a slight advantage over traditional eel culture. However, traditional eel culture has a higher distribution and the financial advantage of intensive culture is primarily due to the cheaper eel seed. The mass production of eel from China has caused Taiwan to lose the comparative advantage in roasted eel for the Japanese market. Cage culture is a new aquaculture venture in Taiwan. The structure of cages, feed and other facilities still need to be improved. Although Dumerils's Amberjack (Seriola dumerili) and red porgy (Pagrus major) can make higher profits than other species, fish farmers still have great expectation for cobia (Rachycentron canadus). As Taiwan's market is not big enough, there is great hope that the Japanese market can be developed and cobia can become a candidate for sashimi (raw fish). For sustainable development, aquaculture must be economically viable, ecologically sound and socially acceptable. To attain these goals, production and marketing groups, and production area were suggested. Proper administration and management could help the industry to be sustainable.

The fact that fish possess a sense of smell has been known for some time. Fabricus (1780) described how lampreys and sharks would follow rotting meat and Mono, (1744) demonstrated that fish would react to a worm in the water and show adaptation to its odour. Bateson (1890) showed feeding responses in both elasmobranchs and teleosts to hidden food and juices squeezed through cloth. These reactions are present in both seeing and blind fish. Copeland (1912)and Parker (1914) shoved that dogfish were able to localize hidden food by olfaction, thus proving that it could be a directional sense. Initially the study of chemosense had been performed by observing the occurrence of a definite feeding reaction either as a result of detecting food odour or to extend the type of stimulus studied when the reaction had been conditioned to another stimulus (Göz, 1941; Teichmann, 1959). Conditioning is a long process and requires a suitably hardy species. In many cases where a stimulus not connected with feeding is used to condition a feeding reaction we may learn of sensory acuity in absolute terms but nothing of the natural use of the reaction. To examine more subtle reactions to stimuli. especially those not related to feeding, specialized apparatus had to be developed. This allowed workers to look at how a response would be used by the fish in nature. As well as showing reactions to food and prey organisms fish have been shown to use olfaction in social behaviour both with other species and conspecifics of both sexes. Göz (1941) managed to condition a single, blinded, minnow Phoxinus phoxinus to show a feeding reaction to the odour of another fish species Ictalurus nebulosus not the prey of the minnow. This took many weeks using even the easily-trained minnow. Because of the difficulties and limitations many workers have adopted more direct approaches, Wrede (1932) found blinded minnows (a shoaling species) preferred to visit a compartment in an aquarium where the odour of a conspecific lingered rather than a control compartment. Hemmings (1966a) used a more complex preference trough derived from that of Shelford and Allee (1914) and found that the shoaling, freshwater roach (Rutilus rutilus) showed a preference for the end which had the odour of other roach. By analysis of movement in the trough he showed that this preference was due to increased turning rate. Investigating these pheromones in char, D6ving, Nordeng and Oakley (1974) used electrophysiological methods, recording electrical impulses from the olfactory tract, and found the char was able to identify racial differences in this social identifier. Doving,Enger and Nordeng (1973) proposed a component of mucus to be the pheromone. Interest in amino acids as a possible stimulus to feeding in marine organisms began when Steven (1959) found that glutamic acid produced a feeding reaction in two species of tropical marine fish. Case and (iwilliam (1961) found that a range of amino acids would stimulate a blinded crab to feed when applied to the cheiae This reaction was confirmed electrophysiologically on isolated dactyl preparations, responses being obtained from the dactyl receptors to a range of amino acids. Many workers including Hara et al (1973), Hashimoto et al (1968), Haynes et al (1967) and Suzuki and Tucker (1971) have found similar reactions from the olfactory nerves of teleosts. The long, easily accessible olfactory tract in some teleost species makes them ideal subjects for electrophysiological investigation. The technique of monitoring nerve impulses enables a large number of amino acids to be rapidly tested; the thresholds obtained however may not be those which will stimulate a feeding reaction and hardy species are needed. Most work on chemosense in teleosts has been performed on adult and juvenile fish; this is not surprising since rearing beyond the non-feeding yolk sac stage of many important marine species has only been successful in the last decade. The histology and morphology of the development of the olfactory system has also received little study since Holm (1894) described this process in Salmo salar. He showed that in Salmo salar, which took 90 days from fertilization to hatch, there was no nervous connection between epithelium and brain at 60 days post fertilization but one was found at 83 days post fertilization. The olfactory nerve appeared as the groove closed. Attention has been drawn to this lack of knowledge by Hasler (1957), Johnson and Brown (1962) and Branson (1963). In many of the teleosts so far studied the olfactory system is undergoing development not only for the whole of larval life but beyond into juvenile development. Larval development is a valuable time to study this, and indeed any organ system, since it is changing in physical structure, increasing in complexity and possibly changing in acuity and function. The role of a larva can be in many cases to give the early stages of an organism a different ecological niche from the adult, preventing intraspecific predation and competition for food. Therefore its senses may be used for different purposes to the adult, (for example the use of chemosense and touch in the settlement of Balanus nauplii (Crisp, 1974) a system obviously of no use to the adult). In the case of a nektonic shoaling fish such as the herring with a planktonic non-shoaling larva, there would be a possibility of larvae dispersing over a large area prior to onset of shoaling behaviour. There would obviously be some value in keeping larvae together in loose groups and it is likely chemosense may play some part in this. Aggregations of planktonic marine organisms are a well documented phenomena (Barnes and Marshall, 1951; Weibe & Holland, 1968) from the longevity of these aggregations it seems unlikely that this is caused by physical boundaries of water parcels. It seems possible that chemosense acts to keep aggregations intact and in some organisms is retained in adult shoaling life, perhaps to maintain aggregations when the shoals disperse at night (Harden-Jones, 1962). Feeding patterns in larvae and adults can also differ; for example herring and plaice larvae will snap at food organisms in the water column, taking selected individual prey; in the case of herring almost stalking. As adults, herring mainly feed by filtering, although evidence from other filter feeding fish suggest a proportion of particulate feeding will also occur depending on prey size and density (O'Connell, 1972), and plaice move along the sea bed eating epibenthic organisms, mollusc siphons and sedentary worms, Both modes of feeding require good vision. Newly hatched herring (Blaxter and Jones, 1967) and plaice (Blaxter, 1968a) have very different eyes from the adult, the eye developing throughout larval life. In Sardinops caerulea, Schwassmann (1965), the eye is a very rudimentary structure when feeding begins. Although the feeding act is visual, the volume which can be searched using sight alone is small (in herring 0.3- 2.0 litres per hour and in plaice 0.1-1.8 litres per hour (Blaxter and Staines, 1971). It seems possible that olfaction could assist in the search for food either by directionally guiding the fish larva to a concentration of food organisms or restricting energy-requiring searching behaviour to periods when food organisms can be detected by presence of their odour. With these possibilities in mind the outline of study below was adopted.

Aquaculture, as an aquatic based economic activity, has risen from relative obscurity to a position of global recognition in just over two decades, and is forecast to become increasingly important in the next century. This growth, however, has been accompanied by increasing concerns over the environmental and social costs associated with the exploitation of the natural resource base on which it depends. This occurs in the broader context of increasing awareness of the finite capacity of the global system, and the need for development of more sustainable resource management regimes. The objective of the study is to examine if and how 'sustainability' can be brought into assessment for aquaculture development. The main concepts of sustainability are discussed, and key issues for assessment identified. The range of impacts associated with aquaculture development is reviewed, and broad categories of sectoral sustainability indicators proposed. Specific issues and assessment approaches are examined in three case studies, focusing on environment interactions, resource use assessment, and the rural development context, respectively. There follows a structured analysis of applicability of selected generic appraisal methods, concluding that while all may contribute, none is sufficiently broad to account for all sustainability perspectives. A more comprehensive framework for the assessment is therefore proposed, by which sustainability features of any system can be described, potential indicators and methods of assessment identified, and results communicated to the decision making process. This does not offer a definitive judgement on sustainability, but presents an holistic view, allowing explicit recognition of trade-offs involved between conflicting sustainability objectives. It is concluded that sufficient information is available for this approach to be developed and applied on a wider basis. Constraints to more sustainable development relate more to the social, political and economic environment than to problems of uncertainty in forecasting biological and physical systems.

Interpreting data gathered from field studies that investigate the effect of pollution on fish parasites is complicated by the presence of multiple parasite species and mixed pollutant loads. The aim of this study was, therefore, to use controlled experimental studies to assess the impact of a single heavy metal, cadmium, on selected species of the monogenean genera, Dactylogyrus Diesing, 1850 and Gyrodactylus von Nordmann, 1832 and on their hosts, Cyprinus carpio L. and Poecilia reticulata (Peters). The first host-monogenean system investigated was the gill fluke Dactylogyrus extensus Mueller & Van Cleave, 1932 and its host C. carpio; the second system, Gyrodactylus - P. reticulata, involved individual investigations on Gyrodactylus turnbulli Harris, 1986 and G. bullatarudis Turnbull, 1956. Independent investigations of parasite biology and host responses were undertaken in order to elucidate host-parasite interactions in the presence of cadmium. The maximum permitted level of cadmium in controlled freshwater sources is set at 5μg/l by EEC Directive 76/464/EEC and experiments were carried out using this concentration and the higher, but environmentally realistic, levels of 20-50μg/l. For the first time it has been demonstrated that Dactylogyrus extensus exposed to 5μg/l cadmium show a subtle enhancement in the in vitro rate of oviposition and a statistically significant enhancement in their in vivo rate of oviposition after 9-10 days exposure. The effect of cadmium on egg production by D. extensus and on selected aspects of the innate immune response of C. carpio were investigated in separate experiments. Although run independently of each other, the sample times of both experiments were the same. It was found that the treatment in which the rate of oviposition by the parasite was greatest, was the treatment, where at the same sample point, the phagocytic activity of C. carpio was greatest. Exposure of D. extensus to the higher level of 30μg/l cadmium, also enhanced egg production after 9 days, but, 14-30 days exposure resulted in a lower rate of oviposition than that recorded in control parasites, suggesting that cadmium may directly, as well as indirectly, influence the reproductive biology of this parasite species. The hatching of D. extensus eggs was similarly affected by cadmium exposure, with those produced and incubated in 5μg/l cadmium demonstrating a statistically significant more rapid hatch rate than the controls, while those produced and incubated at the higher concentration (30μg/l) showed a statistically significant slower rate of hatch than the controls. Exposure of adult D. extensus to cadmium concentrations ranging from 5 to 3,400μg/l in vitro resulted in an enhancement of survival above the controls. Only at 13,100μg/l cadmium was there a statistically significant reduction in survival and in vitro egg production. Atomic adsorption spectrometry demonstrated that D. extensus is a net accumulator of cadmium, with the concentration of cadmium accumulated by the parasite, increasing with increasing exposure concentrations. The degree of cadmium accumulation in C. carpio organs was in the order of gills > kidney > liver > muscle=spleen. Even at 5μg/l, the level of cadmium detected in the muscle (ca. 0.2μg/g) exceeded the permitted level in food fish (0.05 mg/kg (μg/g), after only 9 days exposure. The haematological and immunological responses of C. carpio exposed to 5μg/l cadmium showed only subtle differences from the control fish, with these differences being most marked in the early stages of the trial (days 9-14). By the end of the trial there was little difference in the responses of these fish from the controls, suggesting that carp can adapt to low-level cadmium exposure. Cadmium at 50μg/l resulted in exaggerated alterations to the immune responses of carp, with statistically higher cortisol levels, phagocytic activity of kidney phagocytes, granulocyte number and significant lymphopenia, at days 6 to 14 of the trial. Several of these changes are indicative of a typical stress response. The respiratory burst and phagocytosis of kidney phagocytes in C. carpio appear to be linked to the level of cortisol, with both factors increasing as cortisol levels fall, suggesting that the effects of cadmium on the immune system may be mediated to some extent via the production of corticosteroids. Cadmium at concentrations below the permitted maximum caused statistically significant increases in the population size of both Gyrodactylus bullatarudis Turnbull, 1956 and G. turnbulli Harris, 1986 on P. reticulata. Statistically significant differences in the population size of G. turnbulli were also recorded between male and female P. reticulata. Exposing P. reticulata to 5μg/l cadmium resulted in little difference in the respiratory burst of kidney phagocytes and the production of myeloperoxidase when compared to the same parameters in control fish. The phagocytic activity of these fish was, however, consistently elevated above the controls. Exposure to 20μg/l cadmium resulted in a further enhancement of both phagocytosis and respiratory burst in P. reticulata. Unlike, C. carpio, no adaptation to cadmium exposure was observed in P. reticulata within a 30-day period. During the trial, subtle differences in the innate immune parameters of male and female guppies also emerged. None of the three innate immune parameters investigated, i. e. phagocytic activity, respiratory burst and myeloperoxidase production, appeared to correlate to the observed differences in the population growth of G. turnbulli. The finding that cadmium at levels below its permitted maximum can significantly increase numbers of Gyrodactylus spp. to the detriment of P. reticulata, suggests that the water quality guidelines, with regard to the permitted concentration of this metal, should be reviewed. This study has provided the first information on the effects of low concentrations of cadmium on selected monogenean parasites and their hosts and has been the first to attempt to elucidate host-parasite interactions in the presence of this metal. The study has provided a range of interesting findings and has offered several avenues for further investigations into a complex field of research that is still in its infancy.

Thesis (M. S. - Soil, Water, and Environmental Science)--University of Arizona, 2003. / Includes bibliographical references (leaves 99-102).

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 5 uppsatser.

Thèse (M.Sc.)--Université Laval, 2008. / Bibliogr.: f. 51-55. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 98-104). Also available via the Internet.