1. WALLACE RESOURCE LIBRARY
Module 05 – Natural Resource Use and Sustainability
D01 – Identifying overfishing on Indonesian coral reefs

2. Anthropogenic impacts
Reefs are threatened in a number of ways
Destructive fishing: techniques that destroy the reef structure as collateral damage
Pollution:
Increased nutrients can lead to phase shifts, and can increase coral disease
Coral mining:
Destroys the physical structure of the reef and reduces coastal protection from reefs
Overfishing:
Removing fish above a sustainable level, removes key species from the reef
Anthropogenic impacts
Anthropogenic basically means “caused by man”, and is commonly used when talking about the environment. These are all examples of anthropogenic threats to coral reefs and their fisheries.
These are the main impacts which are classed as being anthropogenic. You will see later that another group of threats, often called “natural threats” could also easily be attributed to human activities, but less directly. The threats on this slide are directly caused by humans, and will be discussed in more detail on the next few slides.
It is important to realise that any one particular reef can be affected by all these threats at the same time, or by a selection of them. In cases where a reef is more remote and there is no local human population, there may be no anthropogenic impacts at all (like the Palmyra Atoll example, although now research is being carried out there more regularly, there is a chance of diver damage and pollution from boats).
Tourism:
Coastal development can cause pollution and sedimentation, while diver/anchor damage
destroys reefs
Invasive species:
Species introduced to an
area can have devastating ecological impacts

3. Overfishing
You can remove fish without significantly damaging the ecosystem
The highest amount of fishing pressure a coral reef can cope with is called the MAXIMUM SUSTAINABLE YIELD (MSY)
Fishing below this will allow stocks to continually recover, and the reef will remain stable
This figure illustrates a standard effort-yield relationship for a semi-renewable food source. To begin with, the more effort that is put into fishing (by effort we mean time, size of net, number of fishermen etc.) the more fish will be caught, and this is why the graph begins with a positive relationship, and if effort is kept at this level you could continue catching that many fish indefinitely (providing there is no serious impact on the reef from elsewhere). However, eventually the amount of effort being put into fishing is so great that fish are being removed faster than they can replenish themselves. At this point the fishery will begin to decline and if the effort does not decrease, fish catches will grow smaller and smaller until they disappear completely, and this is known as unsustainable exploitation. The highest amount of effort which can be put into fishing without exceeding the potential for replenishment is the ideal effort, and the amount of fish caught at this point is knows as the Maximum Sustainable Yield (MSY).
Fishing above MSY is known as overfishing and will mean fish stocks decline until the system collapses

4. Fish fences
Fish fences are one of many ways fishermen remove fish from coral reefs (a gear type).
It is funnel shaped, made of bamboo and netting, and the opening faces the shore.
Many fish migrate between the shallow water and the reef – fish fences trap these migrating species as the tide goes out.

5. Tasks for this data set
You have catch data from fish fences around Kaledupa Island in the Wakatobi Marine National Park, Indonesia, in 2005 and 2011
You need to use this data to see how catches have changed between 2005 and 2011, as well as how effort has also changed
This data will be used to estimate the level of sustainability of reef fisheries around Kaledupa

6. Research questions
How have catches from fish fences changed between 2005 and 2011 in the Wakatobi Marine National Park?
What does the data tell us about the sustainability of coral reef fisheries in the Wakatobi Marine National Park?

7. Summary conclusions
The data demonstrates an increase in fish fence effort, but a decrease in the catch per unit effort and an increase in the proportion of fish caught as juveniles. These changes were shown to be statistically significant using t-tests.
The change in fish catches demonstrated by fish fences around Kaledupa Island indicates a high level of overfishing/overexploitation. Removal rates are clearly higher than the rate of replenishment, and MSY has been severely exceeded.