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Fish
kills can also result from heavy infestations. In the late summer and
fall, the algae will die. As it decomposes, oxygen is consumed by the
decomposing microorganisms so much so that oxygen can be depleted from
the pond to the point fish don’t have enough to live.
Filamentous
algae are among the most common weed problems in Alabama ponds and,
unfortunately, are also among the most difficult to control. Control
methods are limited compared to those for other aquatic weeds.
Fertilizing the pond early, before there is a problem may
prevent the spread of the algae into deep water.
As
many pond owners know, fertilization of ponds is necessary for maximum
fish production. Fertilization increases phytoplankton, plant-like
organisms that are the foundation of the food chain in ponds sustaining
all higher organisms (i.e. fish). Fertilization can increase fish
poundage (both numbers and size of fish) by as much as threefold. The
extra phytoplankton can also shade out and help to limit the growth of
filamentous algae and other aquatic weeds. Pond owners should aim to
have enough phytoplankton to create 18-24 inches of water clarity. Water
clarity can be determined by attaching a coffee can lid, pie plate or
some other light-colored shiny object to a pole or line, lowering it
into the water and measuring the depth at which the object disappears.
Note
that not all ponds need fertilization and fertilizing a pond already
rich in nutrients can be harmful and may even cause a fish kill. Also,
if you already have a problem with filamentous algae or some other
aquatic weed, do not fertilize the pond because it will only make your
weed problem worse. If you do not yet have a weed problem and plan to
fertilize your pond, you should do it now.
What
if you already have a problem with filamentous algae? If you’re
willing to put up with the nuisance for a month or so, the best strategy
may be to wait it out. Many species of filamentous algae only grow in
spring and will begin to disappear in late May and June.
If
you’re not lucky enough to have one of these types, herbicides will
most likely be required for effective control. Unfortunately, the
herbicides most widely used to control algae contain copper as an active
ingredient, which can be toxic to fish especially when the pond water
has low alkalinity. Before using these herbicides, you should have your
water alkalinity tested and consult with a professional.
Grass
carp may also help to limit the algae. However, filamentous algae are
among the least preferred foods of grass carp. Only at very high
stocking rates and when the carp have eliminated virtually all other
foods, will they begin to control the algae. Again, herbicides will
likely be required.
Along
with weeds and grasses, fire ants also took advantage of dry pond banks
and bottoms last year and can cause problems in refilling fish ponds. As
the colonies are flooded, the ants escape to the surface and form
floating rafts on the pond surface and may build a new nest if they
drift to shore. Fish in the pond, especially bluegill (bream), will eat
the floating ants which can kill the fish if they eat enough of them.
This also occurs when ant colonies swarm during spring reproduction and
spent winged-males or drones fall onto pond surfaces.
Controlling
fire ants on pond edges will not only reduce the likelihood of swarms
falling into the water, but also make fishing the pond a more pleasant
experience. Although countless home remedies exist, insecticides are the
best bet when it comes to controlling fire ants. However, care must be
taken when controlling fire ants around fish ponds because insecticides
can be extremely toxic to fish. Absolutely no insecticides should be
applied to an area of the pond that will flood upon refilling.
On
the banks, baits should be used instead of other insecticides because
baits contain far less active ingredients. To minimize runoff, apply the
bait when the ants are actively foraging so they will collect the bait
particles quickly. To determine if ants are foraging, sprinkle a
teaspoon of bait approximately five feet from a mound. If you do not see
ants collecting the bait within ten minutes, it is not a good time to
apply the bait. It is also a good idea not to apply the bait if foliage
is wet or rain is likely to occur soon after treatment.
Because
of the reduced water levels and crowding created by the 2007 drought,
many ponds will have too few bluegills relative to bass. In other words,
these ponds are out of balance. If you are catching large, healthy
bluegills that are few in number and large numbers of small, skinny
bass, your pond is most likely "bass crowded."
Why
did the drought reduce bluegill numbers so much more than bass numbers?
There are two reasons why and both are related to the positions of the
two species in the food chain. Bluegill can be thought of as being in
the middle and adult bass can be thought of as being at the top of the
food chain. Because bluegills are lower on the food chain, their
production is affected by the reduction in microorganisms forming the
basis of the food chain sooner. Also, the bluegills were crowded in with
the top predator on the food chain, adult bass feeding almost
exclusively on small bluegill, with nowhere to hide.
To
remedy the situation, you will need to remove 20-25 lbs. of bass per
acre in fertilized ponds, and ten lbs. per acre in unfertilized ponds.
Although you can, and should, harvest bass throughout the year, it is
important to start the process now so bluegill can begin to build up
their populations. Target bass less than 14 inches for harvest, but
larger bass can be taken. Bluegill production and growth can be enhanced
by fertilizing your pond and supplemental feeding with floating catfish
food.
If
you have any questions about managing your pond, contact your county
extension office.
Patrick
Cook is a Regional Extension Agent with Alabama Cooperative Extension
System’s Forestry, Wildlife & Natural Resources division. |
