As
the weather warms in the spring and early summer, some pond
problems become more likely. Dissolved oxygen problems are
the most common, particularly during cloudy and rainy weather
that follows a warm period. In early spring, deep ponds
(more than 7 feet) can experience “turnover”
when a cold rain or cold wind causes the surface water to
mix with the bottom layer of oxygen-poor water. The mixed
water contains too little dissolved oxygen for fish to survive.
Pond
owners who notice dying fish often suspect poisoning from
drifting agricultural chemicals or from some other activity
on neighboring property. While possible, fish kills from
chemical poisoning are rare.
In almost every case, fish kills in both private and public
lakes are due to dissolved oxygen depletion (hypoxia). One
characteristic that differentiates hypoxia from any other
problem is that a hypoxia fish kill usually results in the
loss of the bigger fish first. A problem from a toxin will
affect the smaller animals first.
Good
pond design and management can minimize the chances for
hypoxic events. An excellent information source is the handbook
Management of Recreational and Farm Ponds in Louisiana.
This comprehensive manual was out of print, but was recently
updated and reprinted in a cooperative effort of the LSU
AgCenter, Louisiana Sea Grant, Louisiana Department of Wildlife
and Fisheries and Sport Fish Restoration. A copy of the
manual is available at www.lsuagcenter.com/en/crops%5Flivestock/aquaculture/recreational%5Fponds/
or you can request it from your parish AgCenter office.
Another
common pond problem at this time of year is the formation
of floating “scums.”
The
good news is that these often arise from the breakdown of
troublesome matted algae. In south Louisiana, filamentous
algae grow in shallow pond areas during the winter. People
sometimes describe the mats of fine, green threadlike growth
as “moss.” In most ponds, these algae decline
as the water warms, and the dead vegetation may produce
a floating scum.
Except
for the most severe cases, no remedial action is needed.
In a few weeks, the natural breakdown process will be complete.
Back
to Top |
