Fish surveys are often conducted by SCUBA divers or snorkellers. A study in the journal Environmental monitoring and assessment has found that these surveys may be inherently inaccurate as snorkellers frighten away the fish they are supposed to be counting.

Researchers from at the University of Victoria, Canada, used an underwater video camera to assess how fish abundance, family richness and community composition were affected by snorkellers and divers on a coral reef in Thailand. They found that snorkellers significantly disturbed the fish they were supposed to be recording. The SCUBA divers didn’t provoke the same disturbance. However, only 6 divers were involved in the study so the results are not conclusive.

The researchers suggest that the use of a stationary video camera may help cross-check data that is collected by divers and snorkellers to assess the true family composition and document the presence of rare and easily disturbed species.

Journal Reference:
Environ Monit Assess. 2009 Apr 8

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