Pond Boss Forums INTRO Questions & Observations fish gate

I have recently built a pond and stocked it with fish. I'm concerned that when a flood finally comes that my fish my be washed over my spillway. Does anyone have any suggestion on how to build a fish gate to keep my fish from being swept out of the pond? Is expanded metal the best material? How large of openings should the metal or mesh have to allow debris to pass through but not fish? Any suggestions would be appreciated. Thanks
fowlball

Fowlball:

This topic has been discussed before so there should be a number of comments and hopeully links to the previous info.

What species do you have now or plan to add later? There are major differences on how different fish behave in a major runoff event. Grasscarp, for example, are famous for seeking running water and leaving ponds in such occurences. Some other large fish have been reported to hunker down on the bottom and rarely get lost. Hopefully someone will know what to expect for the species you have.

Be aware that once your fish population is established, runoff loss of small fish has little or no impact. I know right now, after stocking, each and every one seems precious. It will be a lot easier to see a lost fish (whether swept away, bad hooked, heron kill, or miscellaneous floater) after they start spawning their own replacements. Retention of your big fish and non-spawners (e.g. Grass carp, HSB) will be what you want to worry about.

It is much more important to ensure whatever spillway fish screen you end up using doesn't trap debris, block the spillway, and cause a dam washout than it is to save a number of fish. Have 20% of your fish wash downstream - that's bad. Have your dam washout - that's clearly a lot worse. So a knowledge (or at least a prediction) of what size runoffs you will get over the course of a year (or several years) should be important input into the screen design. So is what kind of debris may float into the pond from the watershed. Are there woods with lots of leaves and branches? Cropfields with cornstalks or wheat stubble? Immaculate manicured lawns with floating patio furniture? A marina? These questions may indicate what kind of debris could end up clogging your screen and influence your design.

Consider a design which would allow you to change to hole size later on if you want to - perhaps a permanent framework you attach hogpanels (larger holes) or fish/snow fence (different small hole sizes available) to.

FWIW, here is the one article I have a link for on spillway fences: Langston U Spillway Fence Article

Pay close attention to Theo's warning. New dams need time to settle. The spillway is there for a reason and shouldn't be obstructed in any way. For the most part, fish try to travel upstream. Yeah, you might lose a couple of your new babies, but it shouldn't be a real problem.

If you get some grass carp, they will try to escape downstream. They are about the only ones that could be a problem. Especially at $15 each. BTW, when do you expect to get enough rain to be a problem? Most spillways can be considered pretty low mileage and I figured the hill country was about as dry as the rest of the state.

fowlball,

I've found a technique that works for me...it was first suggested to me by Todd Overton a few years back.

Materials: discards of stock panels, steel posts, and twist ties.

American Fence has a store in Austin and is a good source for the panels. They usually have lots of 3 and 4 foot leftover sections (leftover from custom gate building). They cost only a couple of dollars apiece. Be sure to get the narrow gapped sizes and if not those then double up on the sections. Buy as many sections as you need to cover the gap, but usually three or four sections will cover. Drive 5 foot steel posts spread apart to support the panels. Attach the panels to the posts with twist ties.

This technique is inexpensive, easy to install, and very effective, especially on grass carp. Make no mistake, grass carp will look for moving water and a way out of any pond. This technique has never produced clogging problems with it either....but it helps to have a relatively clean pond.

If you do a search, you can find some pictures I posted of these gates in the past.

I suggest no spillway screening unless you have grass carp. If your pond has adequate bottom structure and cover for fish, there is no need for a screen. If the pond was designed properly, to accomodate a hundred year flood, a screen isn't necessary.
If you have grass carp, consider screening downstream, away from the spillway, if possible. If not, absolutely do not have the top of your screen higher than the lowest point of your dam.