450 U. S. BUREAU OF FISHERIES 



large area was covered and a large amount of work accomplished in 

 the short time from January 26 to March 11. 



Dr. Clark particularly desired to obtain an identified series of 

 the more common local species of fishes for the laboratory collection, 

 principally for use in determining the species from which parasites 

 are obtained for study from time to time by the staff helminthologist, 

 Dr. Aurel O. Foster. As many species as possible were collected 

 and later identified in Washington. Representatives of 97 more 

 or less common species have been sent to the Gorgas Memorial 

 Laboratory. Many more species were obtained wliich recjuire further 

 study for exact determination. In the laboratory in Washington 

 Dr. Hildebrand was assisted by Louella E. Cable. 



The time chosen for the investigation was particularly auspicious 

 because the Gatun Locks were dewatered, giving the investigators 

 not only an op])ortunity to "gather" fish on the bottom, but also to 

 see and study the fauna present in the locks. The two species of 

 fish present in great abundance in the two lower levels of the locks 

 were the "blue jack'', Caranx hippos, and the "bony fish", Flops 

 saurus. Other species present in these levels of the locks were the 

 tarpon, several species of snappers, a few groupers, and a consider- 

 able variety of less common and smaller fish and minnows. The 

 upper chamber of the locks, in w-hich the water is quite fresh at all 

 times, contained only a few large tarpons, a few^ marine mojarr.as, 

 Gcrres pJumieri^ a few anchovies, and several small fresh-water 

 fishes. 



It is often asked wlietlier the locks are a passageway for fish. It 

 is understood, of course, that strictly marine fishes, even though they 

 should succeed in passing through the locks could not endure the 

 fresh water of Lake Gatun. Plowever, there are some species that 

 are able to pass from salt to fresh water and vice versa without evil 

 effects. Among these is the tarpon, noAv a regular inhabitant of 

 Lake Gatun. It also occurs in Miraflores Lake, which it could reach 

 only by passing through Culebra Cut and the locks at Pedro Miguel. 

 A special effort was made to determine whether this fish breeds in 

 one of these fresh-water lakes or adjacent arms and streams. How- 

 ever, no evidence indicating that breeding is taking place in fresh 

 water was secured. It seems probable, therefore, that the locks are 

 used as a passageway by the tarpon, and very j)robably by a few 

 other species. 



LTpon the request of Col O. G. Brown, chief health officer of the 

 Panama Canal, inspections were made of a large area of Gatun Lake, 

 where a very profuse growth of Chara occurs, which at low water 

 stages, as during the dry season, forms a very bothersome breeding 

 area for mosquitoes. The situation, however, did not seem to be 

 one that would lend itself to control by the use of fish. 



Collections also were made at the Pearl Islands where local sports- 

 men maintain a fishing club, and where very excellent sport fishing 

 is to be had. Small shoi-e fishes w^ere extremely scarce at the time 

 the collections were made but a short distance offshore fishes were 

 abundant and several species that apparently are new were obtained 

 by trolling. Much more work is required to determine all the species 

 secured there. 



