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trawling. Isaac and Kidd (1953) and Barraclough and Johnson (1956, 1960) 
report on mid-water trawl design. Baldwin (1961) presents a design for a 
trawl to use from small boats. 
Plankton nets are useful for catching larval fishes. The one metre 
stramin net will catch the adults of small species. Throw nets are valuable in 
certain situations. 
Hook and Line 
The ancient art of fishing with hook and line may be employed with 
profit. Angling with various lures or bait from boat, shore, or through 
ice is too well known to require description. Baited set lines may be floated 
at the surface, at mid-depths, or on the bottom. 
Explosives 
Under certain conditions, explosives, such as dynamite, may prove 
suitable. In using dynamite the cap and fuse should be sealed into the stick 
with heavy grease. Hubbs and Rechnitzer (1952) and Ferguson (1962) 
discuss effects of explosives on fish life. Schwartz (1961) provides a biblio- 
graphy on the subject. In general, explosives kill only fishes with gas 
bladders or fishes close to the explosion. As only some of the killed fishes 
float, it is necessary to make arrangements to collect those specimens that 
sink to the bottom. Naturally due precautions should be taken, legal 
requirements should be followed, and public relations should be considered 
in the use of explosives. 
Ichlhycides 
Numerous substances toxic to fishes may be employed in collecting. 
Rotenone, harmless to man or livestock, under proper concentrations is 
perhaps the best. It is prepared from derris, cube, and timbo root (chemical 
formula C 2 3H 2 20 6 ) together with a dispersing agent. In using the powdered 
form it is generally mixed with water into a liquid or paste before dispersal. 
The emulsified form is ready to use. The concentration employed depends 
on the temperature, water quality, and so on. It may be from .5 to 1 part 
per million by weight, but the instructions supplied should be followed. 
In streams it is applied for a period of about 15 minutes so that fish down- 
stream are exposed continuously. A net is stretched across the river 
downstream. It should be applied just above a point where it will be diluted 
below T toxic level by the confluence of a tributary. Rotenone, unlike the more 
dangerous toxaphene, breaks down fairly readily. Quantities should be 
carefully calculated on volume flow. 
Ichthycides may also be employed on lake or sea shores ; in small embay- 
ments; in reed patches, tide pools, coral reefs; underwater with plastic bags 
or squeeze bottles; and even in surf. 
Other ichthycides — copper sulphate, lime, formalin, and so on — may be 
employed in restricted situations such as pools. Many native peoples know 
of local plants that will drug or kill fishes. 
In all ichthycide operations it must be remembered that water is a 
common resource of all. It should not be applied in sport fishing waters, 
nor in drinking or swimming water, and never in waters with rare or endemic 
organisms. 
Scuba 
Scuba gear is of great value in collecting and observing fish. With 
foam rubber suits, one may enter even Arctic or Antarctic waters. Useful 
