- Title
- Inshore benthic communities of the Port Elizabeth abalone ranching concession area
- Creator
- Moriarty, Lauren Alethea
- Subject
- Aquaculture
- Subject
- Abalone industry -- South Africa -- Port Elizabeth
- Subject
- Abalone culture -- South Africa -- Port Elizabeth
- Subject
- Abalone populations -- South Africa -- Port Elizabeth
- Subject
- Poaching -- South Africa -- Port Elizabeth
- Date Issued
- 2019
- Date
- 2019
- Type
- Thesis
- Type
- Masters
- Type
- MSc
- Identifier
- http://hdl.handle.net/10948/41975
- Identifier
- vital:36614
- Description
- Abalone poaching in the Eastern Cape leading to resource depletion has resulted in the suspension of any commercial or recreational exploitation of abalone in the area. Abalone ranching trial projects have been initiated to help improve the natural stocks and potentially provide commercial yields. While seeding started in deeper water (5 – 10 m), improved abalone growth performance has been found in the shallower areas. This has resulted in the seeding effort being moved to these shallower sites (< 5m). An ecological survey of the baseline conditions of these shallow benthic areas is a requirement of the abalone ranching permit conditions (Permit No.: 1503759), aimed at detecting any impact that seeding may have on the benthic community. In addition to providing benchmark data for monitoring, the shallow benthic community (< 6m) in the Port Elizabeth ranching concession area has not been well described in terms of the requirements for abalone ranching. Information on the benthic communities in this area is limited to research on the substrate types and communities in deeper water (> 5m). This study aimed to address this information gap. Dive surveys were conducted along 10 m long transects (~3 reps) at three depth zones (<1m; 1-2m; > 2m) for four sites along the span of the ranching concession area. Similar assessments were done at a seeded site at the Noordhoek Ski Boat Club and an unseeded site at the Willows area, in order to reveal whether seeding had any impact on the benthic community. Images from a GoPro mounted in the centre of a framer unit (0.5 m2) were taken every 0.5 m along the transect. Macroalgal and macrofaunal cover was determined from these images, and the benthic community characterised from these data. Seaweed samples were taken for species identification. In the four baseline sites, sampling was done at three depth zones to note any changes with a depth gradient, both in terms of substrate type, as well as community composition. There was a notable trend with substrate type having a significant influence (P<0.05) on the community structure. Seaweed communities were dominated by Plocamium corallorhiza and coralline turf based on substrate types. There was also a significant relationship (P<0.05) between substrate type, dominant seaweed species and abalone presence. A Canonical Correspondence Analysis (CCA) of the community data suggested that the benthic community does not change significantly along the distance of coastline sampled. A hierarchical cluster analysis of Bray-Curtis dissimilarity for transect data also suggested that the four sites do not represent ecologically dissimilar communities. A similar analysis showed that abalone seeding had to date not altered the benthic community in shallow seeded areas from the community described for shallow unseeded areas. The study was used to describe the baseline benthic community in areas west of Cape Recife, examine the natural variability along the coast, and determine whether there are relationships between the benthic community composition and emergent abalone abundance. This information will be useful in selection of habitats for abalone seeding in the future. It is important that monitoring and surveying of the study area are to be continued in so allowing for long term data collection which will help in making informed decisions as well as documenting the impact in seeded areas when compared to unseeded areas.
- Format
- vii, 74 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Lauren Alethea Moriarty.pdf | 1 MB | Adobe Acrobat PDF | View Details Download |