What is an artificial reef and why are we developing and using one?

The artificial reef project has been ongoing since March 2017. It is a long-term project with the aim to successfully create reefs that increase biodiversity in the surrounding waters.

The project is still in its experimental stage, but the long-term aim is that when the experimental phase is completed, this knowledge will be used to design and install a series of artificial reefs on Lipsi island – within the Aegean Marine Life Sanctuary. The current experimental reefs are located in sites that are now deemed unsuitable due to their exposure level.

Currently, the reef is waiting to be relocated to a more sheltered location. Before the reef is relocated we are carrying out fish census surveys and camera surveys in the area to assess the level of fish present at “time zero” so we can have comparable data to assess the change in fish abundance and biodiversity in the area after the reef has been relocated there.

Figure 1. Free diver inspecting sea floor.

How we are monitoring the new reef location?

It is important to get to know our new site well enough before the reef is relocated to it. For this purpose, we are conducting surveys in the area and collecting data. For the fish surveys, three transects are carried out at 15m in length and all fish seen directly below the snorkeler are counted. The survey team consists of two to three people, one of which keeps track of the distance and gathers video of the benthic habitat along each transect. This is done, so that later the footage can be evaluated and the substrate noted as a percentage, i.e. SG – seagrass, S – sand and R – rocks. The rest of the team counts the fish seen along the transect and then an average is taken, if the numbers differ.

Figure 2. Diagram of the transects done. Arrows show direction of travel.

Figure 3.

Results:

Another type of survey is also conducted at the site. A camera is placed in the exact location that the reef will be put and left for 20-30 minutes. The footage is watched and the fish species are identified and recorded. This method allows us to get a closer look at the fish without having to worry about startling them or being limited by our lung capacity. This helps us to identify them later, without having to worry about making the wrong call on a species when identifying in the field.

Figure 4. Snorkeler placing a weighted buoy on location.

The first method provides information about how many fish are generally in the area at different times of day and different weather conditions. It showed that there are usually fish present in the area before the reef is implemented and that most of them are found in the transect that is closest to the shore. This is an important result because once the reef is implemented this will be used to determine how effective it is. If the fish count in the area increases and if more fish are observed in the transects farther from the shore, then the project is effective.

To do this properly, however, the area needs to be monitored over a long period of time in order to be able to account for the fish recruitment that occurs in the spring and not to attribute it to the reef.

The second type of survey that is conducted on the artificial reef site aims to provide footage of the fish found around the spot. This method allows for a long observation of a given part of the area without the complications that come with SCUBA diving and the fact that fish gets startled by divers. The footage allowed us to identify about ten different species around the artificial reef site, the most common of which are Coris julis, Chromis chromis and Diplodus vulgaris.

This information is important, as the reef has not been implemented on that spot yet and changes can be made to the design in order to accommodate the local fish species as well as possible.

Viktor Evtimov
BSc. In Biological Sciences
Drexel University