Habitat Map

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Falmouth 2017 - Group 12 7TITLE

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Background Information for Habitat Mapping

South of Pennance Point and North of Newporth Head, between the bay at Maenport, 4 parallel survey lines were analysed using a side-scan sonar onboard the MTS Xplorer. Survey lines were 100m apart, with a 25m overlap, and took about 10 minutes to survey each line. Before we surveyed the area, we looked on the Fal and Helford Marine Special Area of Conservation (SAC) map, which showed that our survey area was not a SAC and therefore we would be able to take a grab sample at any point of interest.

We were also able to make some preliminary observations, based on the lack of habitat variety present. For example it would be most likely we would find a sandy substrate and a low species abundance.

Below are the exact locations and relevant information related to the survey lines.

Along the survey lines we looked at the side-scan sonar trace. If any anomalies or changes in the trace were observed e.g. a boats wake, they were recorded on the trace so we could know what was habitat and what was an anomaly. This allowed an accurate transfer of data onto the habitat map.

We found 2 major points of interest on the trace. At each location we used an underwater camera attached to a plastic board and cable to look at the seabed to see if there were any live species. The boat was drifting at ½ knot. Our observations were predominately dead bivalves, starfish, chlorophyta algae and dead maerl. These observations were taken while we watched the video in live time.

A limitation to our data collection was that our video recording was corrupted when put onto the DVD, and therefore we found it difficult to get images of our species observations. However as we made some quick notes during the video this limitation was partially overcome. location data of video’s 1 and 2 were then lost so locations of those are only approximates.

After the first video, we decided there was enough evidence and interest to take a Van Veen grab. This grab was taken at the location seen in the table above. The grab sample was then sieved and we were able to make more observations about the species in the area.

In the lab our observations were then manipulated, calculating the towfish height and slant range correction for bedforms observed on the trace, and for anomalies recorded. We later created a colour coded habitat map (see top of page).