NO. 6 MYERS AND WADE: NEW WEST COAST FISHES 155 



British Guiana, with native hiari poison, is a compeHing illustration, not 

 only of the previously unsuspected richness of a great tropical fresh-water 

 fish fauna, but also of the comparative ineffectiveness of other types of 

 collecting. When similar methods have been used in a number of selected 

 small streams in tropical Africa, Asia, and the Malay Archipelago, we 

 shall for the first time begin to know the real extent of the fish faunas of 

 those areas. The senior author has used commercial timbo in South 

 American streams with results comparable to those of Eigenmann. The 

 liquid-mud solution is poured into a small brook one-half kilometer or 

 more above the place where a fine meshed minnow seine is staked across 

 the stream, care being used to select a good location where fish habitats of 

 as many types as possible occur (riffles, holes, gravel or stone bottom, 

 weeds, deep pools). The bottom of the net must be sunk into the gravel or 

 held down by stones, so that no fishes can escape beneath it. The amount 

 of poison used depends entirely upon the current and size of the stream, 

 and must be determined by experiment. Two pounds of dust suffices 

 for the average lowland brook of medium flow and size (5 to 15 feet in 

 width and 6 inches to 3 feet depth). A man must be present at the seine 

 and another must patrol the banks and pools, armed with a long-handled 

 fine-meshed dipnet, to catch fishes not carried downstream and to watch 

 for the tiny species which are often not over an inch in length when adult. 

 Fishing must be carried on as long as dead fishes continue to appear (2 to 

 4 hours). Dr. Hubbs has used derris successfully on open lake shores 

 where snags make seining impossible, by surrounding an area with a long 

 seine and mixing poison into the enclosed area. Vestal (1942) has 

 described the poisoning of an entire lake in the mountains of California 

 (an occasion at which the senior author was present), when it was con- 

 sidered desirable to remove all the existing fishes before introducing 

 certain game species. 



Naturally, fish poisons, even those not dangerous to man or domestic 

 animals, should be used with circumspection and with due regard to local 

 laws, many of which forbid the use of any fish poison. In many places, 

 the rarity or restricted range of certain species may contra-indicate the use 

 of such wholesale collecting methods. However, in great tropical river 

 systems, or on the open shores of the ocean, the occasional poisoning of a 

 restricted area by an ichthyologist will seldom have any effect on the 

 fauna as a whole, and the scientific results far outweigh the dangers. 



