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Research Doctorate - Doctor of Philosophy (PhD) / Shrimp farming and capture fishery are two of the major industries of Can Gio district, Ho Chi Minh City, southern Vietnam. These industries have recently developed and contributed to the improvement of local economy. However, they have also raised environmental concerns regarding water pollution and fish stock depletion. The negative impacts of shrimp farm effluents on the water quality of mainstream rivers and fish communities have not been studied in Can Gio. Additionally, there is a lack of research on the influence of the current fisheries management on environmental protection and fish conservation in this district. The goal of this study was to address key issues in fisheries management in Can Gio in regard to the impacts of wastewater from shrimp farming on the water quality of mainstream rivers that affect the local fish communities, and the influence of improper fishing practices that lead to the depletion of local fish stocks. This study also aimed to propose strategies to improve the local fisheries management for more environmentally responsible productions. Two mainstream surveys were developed to obtain data, i.e. environmental surveys for the assessment of water quality and pollution impacts on fish communities; and people interviews for the examination of fisheries management related to shrimp farming and fishing practices. The findings were used as a baseline to develop appropriate strategies for improving the management in terms of promoting sustainable productions both in shrimp farming and capture fishery industries and protecting the environment. This study found that shrimp farming, especially intensive farms have contributed to water pollution in mainstream rivers in Can Gio, and in turn the water pollution has adversely affected the local fish communities. The waters adjacent to the intensive farms were contaminated with high concentrations of organic matter. The number of fish species reduced and tolerant species appeared at higher proportions in these areas. Many improper practices in shrimp farming and fishing as well as weaknesses in government management were addressed to be the key issues leading to environmental pollution and fish depletion. The proposed strategies focused on improving the management at both government and community levels. Promoting community-based management was suggested as a key to the success in fisheries management in Can Gio.

This study examines the biology of the venus tuskfish Choerodon venustus from the southern Great Barrier Reef to enable better-informed management decisions. Venus tuskfish are taken almost exclusively by line fishing. The size of the catch is uncertain, but the annual Queensland commercial catch is probably about 30 t and the recreational catch much greater than this (possibly ca. 300 t). The species is not the primary target of fishers and can be regarded as by-catch taken while targeting other species. However C. venustus is the second or third most commonly retained species in the study area. Venus tuskfish are taken in habitats associated with coral and other reefs across a depth range from 5 m to 90 m. The species is a benthic predator, taking molluscs, echinoderms, annelids, arthropods, and fish (in decreasing order of importance). Feeding intensity was greatest in summer. There was evidence of complex feeding behaviours and a dominance hierarchy amongst feeding fish that may result in large males being more susceptible to fishing. The species is slow growing and long lived. Up to 38 bands were observed on the opercular bones of C. venustus. Back-calculation methods yielded von Bertalanffy growth parameters of L¥ =669 mm, K = 0.09 and t0 = -3.89. Male fish appear to grow faster than females. This may be related either to faster growing fish becoming males, growth acceleration following sex reversal, or both. Selective removal of faster growing males in heavily fished locations may result in a greater proportion of slower growing females in the remaining population. iv Choerodon venustus is a protogynous hermaphrodite; the proportion of males increases as the fish increase in size, transitional fish exist and remnant female tissue was evident in testes. The species is a serial spawner with an extended breeding season perhaps peaking in autumn and around the new and full moon. Females mature between 200 and 250 mm forklength (LCF). Venus tuskfish display sexually dimorphic colouration and appear to have a socio-sexual group structure. Fish occur in extended groups with several large males associated with a larger number of smaller females. Multiple sex-reversals may occur in the groups perhaps in response to the loss of the larger males. Large females produce over 100,000 eggs in the ovaries. The number of eggs released at each spawning is unknown. There is a direct cubic relationship between length and the weight of female gonads. Large females over 500 mm LCF are capable of producing over 20 times the number of eggs of small mature females (around 250 mm LCF). The locations sampled showed marked differences in fishing effort. The Capricorn Bunker Group was subject to much higher fishing effort than the Swains Reefs. Estimates of fishing mortality reflected this trend. Line fishing selects large male fish. The heavily fished Masthead Island had smaller males, females and transitional fish. Fish below 300 mm LCF were not captured efficiently. Venus tuskfish may be capable of modifying their life cycle in response to increased fishing mortality. Sex reversal may be related to the absence of large males in social groups. Hence sex ratio remains constant between fished and unfished locations. In heavily fished populations, females are smaller and consequently produce fewer eggs. Modeling suggests unfished areas may have a potential fecundity over six times that of those heavily exploited. Choerodon venustus are severely impacted by barotrauma during capture, and few captured and released fish are likely to survive. There are special challenges in managing venus tuskfish including: · Their status as a largely bycatch species; · The poor survival of released fish due to barotrauma; · A lack of good measures of catch and effort caused by inconsistent naming of the species and inherent errors in current data collection methods; · Their extended spawning period and likely widespread spawning sites and · The need to support group fecundity by protecting larger fish. A combination of a series of fish reserves, raising the minimum legal size to 36 cm TL, effective catch limits and an effective education program are likely to support the sustainability of the fishery.

The Japanese colonial fisheries authorities of pre-war Taiwan played an important role in the diffusion of offshore and distant water fishing methods. Two of the main fisheries in post-war Taiwan, the longline and trawl fisheries, were introduced from Japan during the pre-war period. Although Taiwan’s fishing industry was devastated in the course of World War Two, with financial aid from the international community and the government’s policy guidance, it was revived in a comparatively brief period of time. Fishing vessels from Taiwan, especially Kaohsiung, soon became, once again, a common sight in the waters of Southeast Asia. The first part of thesis traces the pre-war historical background, the government’s post-war policy guidance and the birth of Taiwan’s offshore and distant water fishing industry in Southeast Asia after World War Two. After the Chinese communists came to power in 1949 Taiwan’s fishing communities were placed under the strict surveillance of the Kuomintang authorities out of consideration for national security. The Taiwanese Government and the military adopted a variety of measures to control and regulate the development of the fishing communities. Also, the people in the fishing industry did their best to cope with the Government intervention. To safeguard their onshore business interests, Kaohsiung’s fishing companies also put considerable energy and effort into dealing with local shipyards, ice-manufacturers, and other fishing ancillary industries. Vessel owners developed industry partnership with those who were cooperative, and either avoided or boycotted those who were viewed as a potential nemesis. With a view to analysing the interactions between the fishing industry, the Government, the military, and key ancillary industries, the second part of the thesis focuses upon the history of Taiwan’s post-war fishing industry from the perspective of the national-industrial level. The development of Kaohsiung’s fishing industry was also deeply affected by ethnic factors. Siao Liouciou fishers were solely dedicated to the longline fishing method; Shandong people preferred to be involved in pair-trawl fishing. The final part of the thesis further narrows down the scope of the history of Taiwan’s fishing industry to the local level context of the fishing communities. The histories of six fishing companies are used to compare the cultures and management styles of the trawling and longlining fisheries. Finally, the fishers’ daily lives in the waters of Southeast Asia, and the culture and routine practices of Kaohsiung’s fishing communities are explored in depth.

Research Doctorate - Doctor of Philosophy (PhD) / Shrimp farming and capture fishery are two of the major industries of Can Gio district, Ho Chi Minh City, southern Vietnam. These industries have recently developed and contributed to the improvement of local economy. However, they have also raised environmental concerns regarding water pollution and fish stock depletion. The negative impacts of shrimp farm effluents on the water quality of mainstream rivers and fish communities have not been studied in Can Gio. Additionally, there is a lack of research on the influence of the current fisheries management on environmental protection and fish conservation in this district. The goal of this study was to address key issues in fisheries management in Can Gio in regard to the impacts of wastewater from shrimp farming on the water quality of mainstream rivers that affect the local fish communities, and the influence of improper fishing practices that lead to the depletion of local fish stocks. This study also aimed to propose strategies to improve the local fisheries management for more environmentally responsible productions. Two mainstream surveys were developed to obtain data, i.e. environmental surveys for the assessment of water quality and pollution impacts on fish communities; and people interviews for the examination of fisheries management related to shrimp farming and fishing practices. The findings were used as a baseline to develop appropriate strategies for improving the management in terms of promoting sustainable productions both in shrimp farming and capture fishery industries and protecting the environment. This study found that shrimp farming, especially intensive farms have contributed to water pollution in mainstream rivers in Can Gio, and in turn the water pollution has adversely affected the local fish communities. The waters adjacent to the intensive farms were contaminated with high concentrations of organic matter. The number of fish species reduced and tolerant species appeared at higher proportions in these areas. Many improper practices in shrimp farming and fishing as well as weaknesses in government management were addressed to be the key issues leading to environmental pollution and fish depletion. The proposed strategies focused on improving the management at both government and community levels. Promoting community-based management was suggested as a key to the success in fisheries management in Can Gio.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: George R. Parsons, College of Marine & Earth Studies. Includes bibliographical references.