UBC Theses and Dissertations

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UBC Theses and Dissertations

Effects of seaweed farming on tropical shallow coral ecosystems Hehre, Edward James III


Seascapes are being transformed by human activities through a variety of spatially extensive extractive uses. This industrialization has the potential to radically alter the ecology of our oceans. Through focused ecosystem-based management of already degraded systems, it may be possible to create novel ecosystems that maximize benefits for humans, while increasing the diversity and abundance of dependent communities. In this thesis I examine seaweed farming on degraded coral reef ecosystems in order to examine 1) the relationship between seaweed farms and rabbitfish production globally, 2) the relationship between seaweed farms established on shallow coral reef ecosystems and fish assemblage composition, and 3) the diet composition of herbivorous fish in relation to the presence of seaweed farms. I found a correlation between seaweed farming and catches of rabbitfish (family Siganidae), implying farms may drive herbivorous fish catch in Southeast Asia. However, within regions, I found little evidence of increased abundance, biomass, and size of rabbitfish in areas with farms relative to those without. Therefore, the addition of farmed seaweeds was unlikely to subsidize rabbitfish diets, but replaced wild seaweeds removed by farmers. Investigation of seaweed farming activities on coral reef fish assemblages found farms negatively impacted diversity, abundance, and total biomass even in locations subject to blast fishing. These results have significant implications for the management of shallow coral ecosystems. Traditionally, areas of human use within seascapes are divided into distinct categories of use vs. wilderness. Increasingly seascapes have become patchworks of human use, and their impacts may result in different ecological functions. The designation of an area for restoration, protection, or a particular use must be based on several factors including the potential for the activity to alter ecosystem function as well as its ecological context. A novel ecosystems approach to degraded shallow coral reef ecosystems would dictate further human activities within radically altered systems account for both the current ecological function and the entire range of options for further use rather than only focusing on use and impacts solely in terms of traditional restoration.

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