Herbicides offer quick results,
but if the underlying cause of the problem is not corrected, plant growth will reoccur. Grass carp offer an option for controlling most rooted aquatic plants, but if over- stocked these fi sh can completely clean out a pond and leave no feed- ing or refuge areas for forage fi sh. Before choosing between grass
carp, herbicides and other control options, pond owners should read these fact sheets available through Oklahoma Cooperative Extension Service offi ces: • SRAC-360, Aquatic Weed Man-
agement — Control Methods • SRAC-361, Aquatic Weed Man-
agement — Herbicides • CR-9202, Grass Carp for Pond
Weed Management
Fish kills When large numbers of fish
show up dead within the period of a day, a fi sh kill has occurred. Smaller numbers of fi sh dying over a period of several days indicates a disease-related problem. Oxygen depletion is the lead-
ing cause of fi sh kills in Oklahoma ponds. Because low-oxygen kills are usually sudden and massive, many pond owners mistakenly jump to the conclusion that a pesticide must be responsible. These signs point to low oxygen as the cause of a fi sh kill: • Fish gulping at the water’s
surface • Bass die fi rst • Large fi sh die before small fi sh
of the same species • Pond water changes color • Light scum or a fi lm is visible
on the water If you see fi sh gulping at the sur-
face and not too many have died, it may be practical to try saving the rest by aerating the water. This can
50 The Cattleman May 2013
Two reasons pond plants get out of control:
Shallow areas Too many nutrients µ
be done by backing a boat into the water and running the outboard motor with the propeller near the surface to maximize splashing. A pump can be set up to allow
water to cascade over boards or a roll of fencing to break it up into as many drops as possible. Some pond owners report success in us- ing a tractor-mounted bush hog to aerate the pond. Aeration should continue at least until fi sh are no longer at the surface and possibly for as long as several days to allow oxygen levels to recover. Pesticides do occasionally cause
fi sh kills. Some or all of the follow- ing signs can indicate a pesticide fi sh kill: • Dead animals other than fi sh • Small fi sh die sooner than large
ones
• Fish swimming convulsively • Fish with fi ns fl ared out Testing for pesticides is expen-
sive and will not certify that re- maining fi sh are safe to eat. A short list of the names of suspected pesti- cides is needed if testing fees are to be kept affordable. If you believe the expense is justifi ed, collect samples as soon as possible for testing. Most labs require at least a gal-
lon of pond water in clean glass jars. Since waxy lid liners can con- taminate samples, place aluminum foil over the mouth of the container
before screwing on the lid. Water samples must be kept under refrig- eration. Fish or other animals should
be wrapped in aluminum foil and frozen. Labels, written in pencil and list-
ing date, time and place collected, and your name and phone number, should be securely attached to jars and placed inside the wrappings around the animals. Contact the Oklahoma Department of Health Water Quality Lab at 405-271-5240 for advice on pesticide testing. In Texas, the Texas A&M Soil, Water and Forage Testing Lab can have the samples reviewed by an Extension Fisheries Specialist. Visit soiltest-
ing.tamu.edu for more information If the fi sh kill is in public waters,
contact your local game ranger for an on-site inspection.
Muddy water Before attempting to clear muddy
water, determine if any areas are actively eroding in the pond wa- tershed or the pond itself that will continue to muddy the pond. Your county Natural Resource Conser- vation Service (NRCS) offi ce is an excellent source of practical advice on controlling erosion. If it is not practical to stop the
erosion, then a check dam built above the pond may still be able to keep the pond clear by allow- ing sediment to settle before water enters the pond. Muddy water can be of 2 differ-
ent types. To determine which type you have, fi ll a glass jar with pond water and allow it to sit undisturbed for 1 week. If the sediment collects at the bottom and the water above it is fairly clear, then it is settleable by gravity. If it does not, the particles are chemically suspended. If your sample is settleable by
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