Survey of slender naiad, Najas flexilis, in Loch of Butterstone and Loch of Craiglush

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Method steps

1. Loch of Butterstone Slender Naiad bed was divided up into 5 areas, according to the perceived densities of the plant, for quadrat sampling by different divers. Five random quadrats were recorded in areas 1, 4 and 5, and 20 random quadrats in areas 2 and 3. The number of quadrats in each area was determined by the time available. As underwater visibility was only a few centimetres, the quadrats were placed by the diver hovering above the loch bed, unable to see the vegetation, and dropping the quadrat. The bright white colour of the quadrat aided its relocation. Loch of Craiglush was surveyed on 3 and 4 July 1997. With reasonable underwater visibility of approximately 1 m, the reconnaissance snorkel was completed in just over half a day. A team of four surveyors snorkelled around the whole perimeter of the loch, duck diving to depths of up to 5 m. Due to the restricted nature of the Slender Naiad bed and the clumped distribution of the plant in natural breaks in the vegetation, the method selected for detailed survey was a plant count along a series of parallel belt transects. The area was first delineated by sub-aqua divers swimming along the outermost edges. 3 m canes with plastic marker buoys were placed regularly in the bottom mud along the perimeter. Dive weights attached to buoys were used in deeper water. Four transects were laid, running along the length of the bed. One diver swam the length of each transect and recorded details from a band 1m wide, along either side of the transect (an arm's length). Each 100 m transect thus covered 200 m2.