The Diver Effect in Underwater Visual Censuses
Author Information
Author(s): Dickens Luke C., Goatley Christopher H. R., Tanner Jennifer K., Bellwood David R.
Primary Institution: Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University
Hypothesis
The study aims to quantify the relative diver effects on reef fish abundance during underwater visual censuses.
Conclusion
The presence of SCUBA divers significantly decreases the recorded abundance of reef fish, with an overall reduction of 52%.
Supporting Evidence
- The diver effect resulted in a 52% decrease in the mean number of individuals recorded.
- Counts were significantly lower in immediate return transects compared to fixed distance transects.
- Statistical significance was observed in all families except for the Serranidae after Bonferroni correction.
Takeaway
When divers are present, fish tend to hide, making it hard to count them accurately. This study shows that divers can reduce fish counts by more than half.
Methodology
The study used underwater visual census techniques at three sites on the Great Barrier Reef, comparing fish counts with and without divers present.
Potential Biases
The diver effect may lead to underestimations of fish abundance due to fish avoidance behavior.
Limitations
The study only recorded visible fish, potentially missing species that avoid divers entirely.
Participant Demographics
The study focused on reef fish assemblages, specifically seven key coral reef fish taxa.
Statistical Information
P-Value
<0.001
Statistical Significance
p<0.05
Digital Object Identifier (DOI)
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