Behavioral Drift

Discussion in 'Fly Fishing Entomology' started by Teenage Entomologist, Apr 7, 2014.

  1. Don't know if any of you know this already( I didn't). Learned this unique fact from well known Mike Mercer at the only prentation he does once a year. Aquatic insects, at a certain time if the day or night, stop their wandering of the river bottom and most insects of that species let go and float downstream to look for more food, mainly Mayflies and a few other migrational insects like Stoneflies, Midges,ect. It is called Behavioral drift. So if one area in a river didn't have that many insects other insects would float downstream to re-occupy that area. This is important for a fish because all of a sudden after slurping a few insects here and there, these trout see a food truck float right in front of them, and that=chow time! Just some cool info. Tight Lines, Kaden S.
    plaegreid likes this.
  2. Hi TE,
    And adult aquatic insects from flowing water generally fly upstream to lay eggs. [Although, to be honest, this is received wisdom. I haven't read actual studies that have documented this behavioral pattern. If anyone knows of any actual studies, please chime in.] The idea is that there will be fewer competitors for the newly hatched larvae upstream. Essentially, the highest percentage of the youngest stages of an insect should be found at the upstream end of a species range and the highest percentage of pre-emergence insects should be at the downstream end of a species range within a river / river system.
  3. Kaden-

    It is my belief is that mayfly behavioral drift is primarily a nocturnal activity, as that significantly reduces chance encounter with predators.
    Teenage Entomologist likes this.
  4. Steve-
    Here is a link to one such study.
    plaegreid likes this.
  5. Hi Taxon,

    Excellent. Thank you for sharing that study.


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