Observations on Fishless Streams

Every so often I find a stretch of stream that is fishless or nearly so.

The last time it happened was my snorkling last saturday where it took me quite a while to find that darter (and a school of minnow fry who did not come out on camera well). Mind you I saw kits if geographic oddities their (strange triangular ridges and pits, a few very deep holes carved into the sediment by current who I feared exploring as I couldn't see in them, and feared coming face to face with a snapping turtle or beaver). This was odd, as in the past this spot has large schools of minnows.

Seems most fishless or nearly so streams have the following in common.

1. Sand or silt bottom

2. relatively shallow on average (waist deep or less, usually knee deep or less, not counting holes).

3. Low diversity of insect life, or if present mainly large carnivorous insects like dragonfly larva and hellgrammites.

4. A lack of green vegetation, most cover is wood or stone based,

5. A lack of habitat diversity, very few transitions from sand to stone or from bare to vegetated.

Mind you not every fishless or nearly so stretch of stream fits this (Pond brook was rich in insects and rocky), but I find many of them have these in common. Not sure if any of these observations matter to the state of the fish their.

Open habitats in streams with no "architecture" like woody debris are avoided by many fish, because predatory fishes or birds can grab you. Even heavy current can count as a form of architecture.

I have a hard time finding fishless sites that have either not suffered a drought or chemical spill recently. Lack of structure is not optimal but once you have more than a foot of depth the more flexible species will be there if they can reach it.

Low abundance of insects; then look to see if they represent species that are drought tolerant.

I have some funky fishless coal stripper pits loads with damselfly nymphs swimming in water column like fish which is case where fish could not get past water fall needed to get in.

Open habitats in streams with no "architecture" like woody debris are avoided by many fish, because predatory fishes or birds can grab you. Even heavy current can count as a form of architecture.

Their was a fallen log with a deep hole under it, and a couple fallen trees, but no fish near them.

I doubt drought or chemicals have anything to do with it. The streams were rural and not near industrial sites, and I know from a fishing trip a couple weeks before some spots up and down stream from here had fish, (*in fact, the only spot like this I could possibly link to environmental stress is a fishless spot on my trip to Pittsbirg a couple years ago near a logging area),

As for drought, their have been evening thunderstorms every couple days, a couple weeks ago we had flood water from a tropical storm (waters finally dropped when I went out), and this week more flood waters again from intense rain.

I have a hard time finding fishless sites that have either not suffered a drought or chemical spill recently. Lack of structure is not optimal but once you have more than a foot of depth the more flexible species will be there if they can reach it.

Low abundance of insects; then look to see if they represent species that are drought tolerant.

I have some funky fishless coal stripper pits loads with damselfly nymphs swimming in water column like fish which is case where fish could not get past water fall needed to get in.

There was a log with a hole underneath it? I can almost guarantee there were fish in there, not necessarily easy to see.