The effects of an underwater fish observation technique on stream macroinvertebrates at two spatial scales. Petty, J. and Grossman, G. Ecology of Freshwater Fish, 2000.
The effects of an underwater fish observation technique on stream macroinvertebrates at two spatial scales. [pdf]Paper  abstract   bibtex   
We examined the effects of snorkeling, a commonly used fish observation technique, on the distribution and abundance of benthic macroinvertebrates at both the reach (i.e. 10 m) and patch scale (i.e., \textless 1 m) within a southern Appalachian stream (North Carolina, USA). At the reach scale, we quantified increases in macroinvertebrate drift rates associated with snorkeling and used these values to calculate the percentage of the macrobenthos that drifted out of snorkeled reaches. We also used a simple decay model of macroinvertebrate drift to quantify patch scale effects of snorkeling. The model incorporated size specific macroinvertebrate settling rates to estimate the total number of benthic macroinvertebrates that enter the drift in response to snorkeling disturbance. We found that snorkeling consistently produced significant increases in the number of drifting macroinvertebrates. Nevertheless, these increases comprised a very small percentage (\textless1%) of the total number of organisms in the benthos, suggesting that snorkeling probably did not strongly affect macroinvertebrate assemblages at either the reach or patch scale. However, our analyses also indicated that snorkeling had a disproportionate response to snorkeling) relative to other macroinvertebrate taxa. Consequently, the micro distribution of early instar mayflies may have been altered within snorkeled reaches. We conclude that snorkeling related disturbance to the benthos should have minimal effect on the behavior and distribution of most stream fishes at either the reach or patch scale. However, because snorkeling may influence the behavior of fishes that depend on early instar mayflies as a primary food source.
@article{petty_effects_2000,
	title = {The effects of an underwater fish observation technique on stream macroinvertebrates at two spatial scales.},
	volume = {9},
	url = {http://cwt33.ecology.uga.edu/publications/1251.pdf},
	abstract = {We examined the effects of snorkeling, a commonly used fish observation technique, on the distribution and abundance of benthic macroinvertebrates at both the reach (i.e. 10 m) and patch scale (i.e., {\textless} 1 m) within a southern Appalachian stream (North Carolina, USA). At the reach scale, we quantified increases in macroinvertebrate drift rates associated with snorkeling and used these values to calculate the percentage of the macrobenthos that drifted out of snorkeled reaches. We also used a simple decay model of macroinvertebrate drift to quantify patch scale effects of snorkeling. The model incorporated size specific macroinvertebrate settling rates to estimate the total number of benthic macroinvertebrates that enter the drift in response to snorkeling disturbance.  We found that snorkeling consistently produced significant increases in the number of drifting macroinvertebrates. Nevertheless, these increases comprised a very small percentage ({\textless}1\%) of the total number of organisms in the benthos, suggesting that snorkeling probably did not strongly affect macroinvertebrate assemblages at either the reach or patch scale.  However, our analyses also indicated that snorkeling had a disproportionate response to snorkeling) relative to other macroinvertebrate taxa.  Consequently, the micro distribution of early instar mayflies may have been altered within snorkeled reaches. We conclude that snorkeling related disturbance to the benthos should have minimal effect on the behavior and distribution of most stream fishes at either the reach or patch scale. However, because snorkeling may influence the behavior of fishes that depend on early instar mayflies as a primary food source.},
	journal = {Ecology of Freshwater Fish},
	author = {Petty, J.T. and Grossman, G.D.},
	year = {2000},
	keywords = {CWT}
}
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