being sought as helpful tools for many types 
of pest control. 
During the early 1900's, strychnine was 
supplemented by other vertebrate poison-bait 
formulations containing phosphorus, arsenic, 
mercury, and barium carbonate; two burrow 
fumigants, carbon bisulfide, and calcium cya- 
nide were also in common use. In the 1930's, 
these were augmented by thallium sulfate, red 
squill, and zinc phosphide. A shortage of 
rodenticides during World War II set the stage 
for the discovery and development of numerous 
synthetic pesticides, including antu (alpha- 
naphthyl thiourea), sodium mono fluoroacetate 
(1080), and the anticoagulant rodenticides 
(warfarin, pival, fumarin, etc.). 
Several nonlethal chemical formulations for 
alleviating animal damage were developed 
during the latter period. These include a variety 
of rodent, rabbit, dog, cat, and deer repellants, 
as well as several bird deterrents. Aside from 
explosive gases used in mechanical scare 
devices, the repellent properties of these 
chemicals are based on objectionable taste or 
odor, unnatural color, or skin-irritation char- 
acteristics, 
In more recent years the spectrum of re- 
search has been further broadened, and cur- 
rent screening programs encompass a search 
for compounds that produce numerous types 
of biological activities, including systemic 
chemicals to alter the palatability of plants as 
wildlife foods, either as repellents or attract- 
ants. The research also includes studies of 
chemosterilants and stupefactants. 
AQUATIC VERTEBRATES 
About 50 years ago, the need to control 
undesirable fish in sport fishery waters began 
to be recognized. The needs defined by Smith 
(1950) are to rehabilitate habitats for more 
desirable species either by destroying entire 
fish populations or by selectively removing 
undesirable species, to control diseases and 
parasites by killing fish that are disease 
carriers in hatchery water supplies, and to 
generally or selectively destroy diseased or 
parasitized populations in natural waters. 
Prevost (1960) stated that the rehabilitation 
of waters by poisoning fish is the best avail- 
30 
able tool. In a more recent and excellent 
summary, Hooper et al, (1964) concluded that 
the rehabilitation of trout lakes is sound man- 
agement where fishing pressure is moderate 
to heavy and chances of contamination are low. 
They added, however, that more research is 
necessary before the total reclamation of 
warm waters will give predictable results, 
Copper sulfate was the first material used 
in sport fishery management, Titcomb (1914) 
employed it to reclaim lakes, and although the 
chemical killed fish food organisms and 
aquatic plants as well as fish, it continued in 
small-scale use until derris root (rotenone) 
was introduced in 1934 (more than a thousand 
years after its utility was known to primitive 
man), As a result of trials in Michigan and 
New Hampshire, derris rapidly gained favor 
as a tool for rehabilitating lakes and streams. 
By 1949, 34 States and Canadian Provinces 
were using it (Solman, 1950), Some disad- 
vantages of the powdered derris root were 
overcome by using emulsifiable and synergized 
preparations. The search for better toxicants 
has continued, however, because rotenone is 
considered to be expensive and inefficient in 
some situations. 
Cresol was introduced in 1941 as an agent 
for collecting fish (Embody et al., 1941), DDT 
was tested as a fish toxicant in lakes in 1947, 
but it was not considered as effective as 
rotenone. Calcium hypochlorite has had some 
use since 1947 in eradicating fishfrom domes- 
tic water supplies because of the ease of 
neutralizing it with sodium thiosulfate. 
Toxaphene became competitive with rotenone 
in 1948 because of its extreme toxicity to 
fish and its economy. Its hazards to other life 
and long persistence in water, however, caused 
the Bureau of Sport Fisheries and Wildlife 
and several States to discontinue its further 
use in 1963, Endrin was tested on fish in 1952 
and was first applied as a general toxicant in 
lakes in 1958. Some successful applications 
were made in Asia against trash fish, and 
Sreenivasan and Natarajan (1962) concluded 
that it is the most powerful fish toxicant 
known. However, because of its high toxicity 
to other vertebrates, long persistence, and 
tendency to concentrate in tissues of higher 
animals, this chemical is not satisfactory for 
use in fish control, 
