Planet WGSW-24010 User Manual page 55

cover (4.5.5). On the standard sheet (Appendix 5), enter the appropriate Species Cover Value
(SCV) next to each macrophyte species and the overall percentage cover estimate.
4.5.3 Sampling aids
It is important that the bed of channel is clearly visible, to enable accurate assessment of the
species present and their abundance. In circumstances where the bed is not clearly visible due
to deep or turbid water, or due to reflections from the water surface, observation of submerged
species can be aided and errors reduced by the use of a glass-bottom bucket, an underwater TV
camera and/or a grapnel (Appendix 4), as described below.
Gener al guidance
For wadeable surveys, it is strongly recommended that a glass-bottom bucket is used to aid
observation of macrophytes. A grapnel may be used to retrieve submerged macrophytes for
identification from small areas of deep water, if necessary.
At deep-water sites where it is not possible to see the river bed unaided and for surveys by boat,
an underwater TV camera or a glass-bottom bucket must be used to locate the position and assess
the abundance of any macrophytes which cannot be seen from the surface. Use a grapnel to
retrieve submerged macrophytes for identification. Binoculars can also be useful to scan the
margins so that species present in small quantities, particularly if amongst a large stand of other
macrophytes, will not be missed.
In deep and or turbid water the estimates of percentage cover for submerged species may have
to be based entirely on observations from a underwater camera and/or glass-bottom bucket.
Submerged species present in very small amounts may still be missed if the water is turbid.
If the underwater camera and/or glass-bottom bucket is used for a survey at a particular site, then
it must also be used at any other site with which this is being compared.
Where visibility is severely impaired, use an alternative site or survey length if possible.
Otherwise use the same surveyor for sites which are to be compared. If clarity is poor, direct
comparisons of overall percentage cover and submerged species percentage cover should be
treated with extreme caution if used at all.
Under water TV camer a
When using an underwater camera it is possible to see an area of approximately 1–2m wide with
reasonable clarity in very turbid water. During the survey the camera should be used every few
metres across the deep section of the river channel, as necessary. The boat must be rowed very
slowly to ensure stability of the camera and accurate identification of submerged species. It is
recommended that an estimate of the abundance of each species is made for each traverse of the
river and the abundance estimates for that area combined to give a total estimate of percentage
cover in the whole survey area.
The camera unit incorporates a light source which can help visibility in deep/turbid sites, but this
should be used with care as it uses much more power so the battery time is greatly reduced. The
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