Wai Lung Cheung


Relevant Degree Programs


Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - Nov 2020)
Global seafood production from mariculture: current status, trends and its future under climate change (2020)

Mariculture is growing rapidly over the last three decades at an average rate of about 3.7% per year from 2001 to 2010. However, questions about mariculture sustainable development are uncertain because of diverse environmental challenges and concerns that the sector faces. Changing ocean conditions such as temperature, acidity, oxygen level and primary production can affect mariculture production, directly and indirectly, particularly the open and semi-open ocean farming operations. This dissertation aims to understand climate change impact on future seafood production from mariculture. Firstly, I update the existing Global Mariculture Database (GMD) with recent mariculture production and create a farm-gate price database to match the production data. I show that global mariculture production in 2015 was 27.6 million tonnes, with a farm-gate value of USD 85 billion. Secondly, I develop quantitative models to predict the present-day global suitable marine area for mariculture. The results show that total suitable mariculture area for the 102 farmed species is 72 million km²: 66 million km², 39 million km² and 31 million km² for finfish, crustaceans and mollusc respectively. Thirdly, I predict climate change impact on suitable marine areas and diversity. Results show that climate change may lead to a substantial redistribution of mariculture species richness, with large decline in potential farm species richness in the tropical to sub-tropical regions. Fourthly, I predict global mariculture production potential (MPP) under climate change. Results suggest that global mariculture production potential will decrease substantially by 16% in the 2050s relative to 2020s under the business as usual scenario. Finally, I develop a set of shared socioeconomic pathways for mariculture to assess the plausible future scenarios for sustainable mariculture under global change. The results highlight that future mariculture development and sustainability will depend on the efficiency of four domains; science and technology; society; governance and economics.Overall, the dissertation shows that climate change is a major threat to seafood production from mariculture. Climate change effect will depend on the species that are farmed, their locations and the farming operation/technology employed. Future research on the sustainable development pathway for mariculture should further expand on socio-economic modelling and projections.

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Shedding light on the future of caribbean coral reefs under climate change (2020)

Coral reefs are important ecologically and socially but are threatened by local human impacts and future global climate change. Effective management promotes climate resilience but must take into account the unique multi-scale characteristics of coral reef ecosystems. This dissertation assessed historic trends in coral reef fish assemblages across the Caribbean, to determine the impacts of climate change and role of key environmental drivers in shaping these trends and investigated the influence of these drivers on future reef fish biodiversity. Firstly, using ecosystem indicators, I analyzed historical fisheries catches to assess the potential effects of ocean warming and habitat availability on Caribbean reef fish assemblages. I found that changes in community assemblages were higher than global average for all tropical fisheries and could be explained by increases in sea surface temperature and fishing effects. A negative interaction between reef habitats in each country and sea surface temperature in relation to changes in catch composition, suggesting that habitats may reduce the sensitivity of fish communities to warming. Secondly, using species distribution models, I projected changes in coral reefs under climate change in terms of their morphological complexity. Results showed that under a no-mitigation scenario reef complexity declines significantly, with the most morphologically complex species, Acropora sp., showing northward shifts in relative prevalence. Finally, I conducted multi-scale comparisons of the influence of reef complexity with other environmental variables on current and future Caribbean reef fish biodiversity. Reef fishes showed an affinity for higher temperatures, primary productivity and lower dissolved oxygen at the global scale, but tended toward more alkaline areas hosting reefs, with species showing mixed affinities toward dissolved oxygen. Regional models projected more rapid declines in biodiversity, though declines from global models were larger. Global and regional models projected similar magnitudes of range expansion, though invasions were projected mainly in higher latitudes for global models while regional models projected invasions in lower latitudes around reef-associated areas. Overall, my thesis provides new knowledge for climate-resilient conservation planning by highlighting the utility of multi-scale approaches and the role coral reef habitats may play in protecting reef fish assemblages against the impacts of climate change.

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Master's Student Supervision (2010 - 2018)
Scenarios for Coastal First Nations' Fisheries under Climate Change: Impacts, Resilience and Adaptation Potential (2014)

Recent studies have demonstrated ways in which climate-related shifts in the distribution and relative abundance of marine species are expected to alter the dynamics and catch potential of global fisheries. While these studies focus on assessing impacts to commercial fisheries, few efforts have been made to quantitatively project impacts to small-scale fisheries that are economically, socially and culturally important to many coastal communities. This study uses a dynamic bioclimate envelope model to project scenarios of climate-related changes in the relative abundance, distribution and richness of 98 exploited marine fishes and invertebrates that are of commercial and cultural importance to First Nations in coastal British Columbia, Canada. Declines in relative abundance are projected for most of the sampled species (n = 84 to 95; x̅ = -15.0% to -20.8%) under both the lower and upper scenarios of climate change, with poleward range shifts occurring at a mean rate of 2.9 and 4.5 kilometres decade-1 for fishes and 2.7 to 3.4 kilometres decade-1 for invertebrates within BC’s exclusive economic zone. While cumulative declines in catch potential are projected to occur coastwide (-4.5 to -10.7%), estimates suggest a strong positive correlation between relative catch potential and latitude, with First Nations’ territories along the north and central coasts experiencing less severe declines than those to the south. Furthermore, a strong negative correlation is projected between latitude and the number of species exhibiting declining abundance. These trends are shown to be robust to alternative species distribution models, and highlight key management challenges that are likely to be encountered under climate change. Drawing from an interdisciplinary literature review of First Nations’ traditional fisheries management strategies and historical responses to changes in the availability of aquatic resources, a scenario-based framework is applied to explore climate-resilient pathways for First Nations’ fisheries given quantitative projections. Findings suggest that joint-management frameworks incorporating First Nations’ traditional ecological knowledge could aid in offsetting impacts and developing site-specific mitigation and adaptation strategies. This interdisciplinary framework thereby facilitates proactive discussions of potential mitigation and adaptation strategies deriving from local fishers’ knowledge that could be used to respond to a range of climate change scenarios.

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