36 REPORT OF THE COMMISSIONER OF FISHERIES. 
ice to the oyster fishery may be expected in the future. This has been 
brought about by the establishment of several new positions carrying 
salaries that will attract and retain competent assistants. 
Meantime the Bureau has sought to attack such problems of oyster 
culture as were adapted to its means and facilities. Encouraging 
progress has been made in studies of the propagation of oysters, the 
nutrition of oysters, and the occurrence of phenomena of “ greening” 
and “‘green gill.” In the study of “green gill” the results have been 
of unusual interest and value. While no method of controlling the 
“oreen gill”? has been determined, it seems well established that the 
green color is due to the presence of a particular diatom, one of the 
minute floating plants that form a large element of the food supply 
of oysters. This particular species of diatom is known as Navweula 
ostrearia, and is identical with the form which is abundant in the 
region of Marennes, France, and which gives to the oysters of that 
region .the peculiar color and flavor which are so highly esteemed. 
It is not yet ascertained what are the causes of the peculiar abun- 
dance of this form in certain years and in certain localities, but when 
it is known to the public that the occurrence of “green gill” merely 
means that the oysters have attained a condition that is so highly 
esteemed in the markets of Europe much should be done to dispel 
the present prejudice which occasionally causes great financial loss 
to our planters. Instead of being dreaded or a cause of pecuniary 
loss, the ‘‘green gill’? may be welcomed as giving the opportunity to 
supply a superior article at perhaps a premium in price. These state- 
ments do not apply to the oysters which are marked by greening of 
the entire body owing to the presence of certain mineral salts in the 
water. This is a distinct condition not easily confused with the 
well-known “green gill.” 
The problems of oyster culture on the Pacific coast, where an indus- 
try of great possibilities is contending against peculiar natural diffi- 
culties, have received recognition, although not as yet In a manner 
commensurate with the actual needs. Some support has been given 
to investigations being pursued in Puget Sound, and the progress 
attained has been such as to justify the Bureau at the close of the 
fiscal year in arranging ‘to extend a substantially increased measure 
of financial aid. 
The remarkable growth of the blue-crab fishery during recent years 
has made protective action seem imperative, and the Bureau has 
been repeatedly importuned for counsel as to the propriety and 
effectiveness of specific measures proposed and for information regard- 
ing the habits and life history of the crab. Since the blue crab is 
migratory, passing at different stages of its life cycle from the waters 
of one State into those of another and going from the bays to the 
ocean and back, the Federal Government is the only agency which 
can properly and effectively complete the necessary investigations. 
The result of careful attention to the matter has been to perfect before 
the close of the year an arrangement under which competent services 
are secured for attacking the study in a thorough manner. 
