QQ U. S. BUREAU OF FISHERIES 



MUSSEL PROPAGATION 



The previous plantings of fresh- water mussels reported last year 

 have been followed and extended. The observations to date show 

 much better survival of the yellow sand shells than of the muckets. 

 This may be due in part to the fact that the yellow sand shells grow 

 much faster than the muckets and were more readily found. Even 

 local mussel diggers who had not been ap])rised of the plants remarked 

 on the increase in young yellow sand shells in the localities where 

 plants had been made. 



The program of plantings as previously outlined will be continued 

 during the next 3 years, i, e., until a 5-year planting has been com- 

 pleted. At that time complete returns concerning the success of the 

 restocking program will be available. Because an objection was raised 

 by some of the manufacturers to the planting of yellow sand shells, 

 fewer of that species were planted last year, but in view of the greater 

 survival of yellow sand shells as noted above equal numbers of sand 

 shells and muckets will be planted during the 1938 restocking. 



ICHTHYOLOGICAL INVESTIGATIONS 



Fishes of the Ca7ial Zone and Pmimna. — Investigations on the 

 Canal Zone and in Panama, begun in 1935, were continued in 1937 in 

 cooperation with the Gorgas Memorial Laboratory and the Panama 

 Canal by Dr. Samuel F. Hildebrand. A period of 3 months was 

 spent in the field. During this time the locks at the Pacific end of the 

 Canal were un watered, and collections of fish were made (as in the 

 locks at the Atlantic end in 1935) . A study of the specimens and data 

 is under way to determine to what extent the Panama Canal and the 

 locks are used as passageways for fishes. Marine fishes have invaded 

 the fresh water of the Canal to a surprising degree, and at least one 

 species has crossed from the Atlantic to the Pacific. 



A study of the feasibility of attempting further introductions of 

 American food and game fishes in Gatun Lake (earlier attempts hav- 

 ing failed) was made upon the request of the Panama Canal Govern- 

 ment. It was decided that previous attempts to introduce fry had 

 failed because of the great abundance of small native predatory fishes. 

 It was therefore recommended that in the future the fish be reared 

 to a length of six inches or more before liberation. Extreme caution 

 must be exercised in the choice of species, because it is highly necessary 

 to conserve the native mosquito-eating top minnows, important in the 

 control of malaria. 



General collections of fishes were made in various sections of Pan- 

 ama, both in fresh and salt Avater. The study of the fresh water 

 material, which is nearly complete, has resulted in the discovery of 

 several new species and has demonstrated that the fresh water fishes 

 of the Atlantic and Pacific slopes have intermingled in the Canal to 

 some extent and that limited hybridizing of very closely related 

 species has taken place. 



Ainerican Anchovies. — The study of the American anchovies under- 

 taken by Dr. Hildebrand more than a year ago was continued as 

 other duties perm'itted. Observations on Atlantic coast species of 

 both North and South America are nearing completion. A few Pacific 

 coast species, closely related to Atlantic species, also were studied. 



