acre to the pond itself are generally cons idered hazardous. And the pois on, once introduced, is
hard to get rid of. One pond that had been treated with DDT to remove unwante d s hiners
remained s o pois onous through re peated drainings and flus hings that it killed 94 per cent of the
s unfis h with which it was later s tocked. Appare ntly the chemical remained in the mud of the
pond bottom.
Conditions are evidently no better now than when the mode rn ins ecticides firs t came into us e.
The Oklahoma Wildlife Cons ervation Departme nt s tated in 1961 that reports of fis h los s es in
farm ponds and s mall lakes had been coming in at the rate of at leas t one a week, and that s uch
reports were increas ing. The conditions us ually res pons ible for thes e los ses in Oklahoma were
those made familiar by repetition over the years: the application of insecticides to crops, a
heavy rain, and pois on was hed into the ponds. In s ome parts of the world the c ultivation of fis h
in ponds provides an indis pens able s ource of food. In s uch places the use of insecticides
without regard for the effects on fis h creates immediate proble ms. In Rhodes ia, for example,
the y oung of a n i mp o rtant f ood fis h, the Kafue brea m, are killed by expos ure to only 0.04 pa rts
per million of DDT in shallow pools. Even s maller dos es of many othe r ins ecticides would be
lethal. The shallow waters in which these fish live are favorable mosquito-breeding places. T he
problem of controlling mosquitoes and at the same time conserving a fish important in the
Central African diet has obviously not been solved satisfactorily.
Milkfish farming in the Philippines, China, Vietnam, Thailand, Indonesia, and India faces a
similar problem. The milkfish is cultivated in shallow ponds along the coasts of these countries.
Schools of young s uddenly appear in the coas tal waters (from no one knows where) and are
s cooped up and placed in impoundme nts , whe re the y complete their growth. So important is
this fish as a source of animal protein for the rice-eating millions of Southeast Asia and India
that the Pacific Science Congres s has recommended an international effort to s earch for the
now unknown s pawning grounds , in order to develop the farming of thes e fis h on a mass ive
s cale. Yet s praying has been permitte d to caus e heavy loss es in exis ting impoundments. In the
Philippines aerial s praying for mos quito control has cos t pond owne rs dearly. In one s uch pond
containing 120,000 milkfis h, more than half the fis h died after a s pray plane had pass ed over, in
s pite of des perate efforts by the owne r to dilute the pois on by flooding the pond.
One of the mos t s pectacular fis h kills of recent years occurred in the Colorado River below
Aus tin, Texas, in 1961. Shortly after daylight on Sunday morning, January 15, dead fis h
appeared in the new Town Lake in Aus tin and in the river for a distance of about 5 miles below
the lake. None had been s een the day before. On Monday there were reports of dead fish 50
miles downstream. By this time it was clear that a wave of some poisonous substance was
movi ng down in the river water. By January 21, fish were being killed 100 miles downstream
near La Grange, and a week later the chemicals were doing their lethal work 200 miles below
Aus tin. During the las t week of January the locks on the Intracoas tal Waterway were clos ed to
exclude the toxic waters from Matagorda Bay and divert them into the Gulf of Mexico.
Meanwhile, investigators in Austin noticed an odor ass ociated with the ins ecticides chlordane
and toxaphe ne. It was es pecially s trong in the dis charge from one of the s torm s ewers. This
s ewer had in the pas t been as s ociated with trouble from industrial wastes, and when officers of
the Texas Game and Fis h Commission followed it back from the lake, they noticed an odor like
that of benzene hexachloride at all openings as far back as a feeder line from a chemical plant.
Among the major products of this plant were DDT, benzene hexachloride, chlorda ne, and
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