XLIV REPORT OF COMMISSIONER OF FISH AND FISHERIES*/ 
and perhaps in density, poisoned waters, excess of sediment, unusuaf 
storms, accumulations of shore ice, diseases, etc. 
The deterioration in the inshore fisheries of New England and in the' 
shad, salmon, and whitefish fisheries appears to have been the result 
principally of human agencies; if not in all cases directly, yet through 
the destruction of the food on which the several species lived. The 
naturally poisoned waters of the Gulf of Mexico have caused much in- 
jury, and physical disturbances along the inner edge of the Gulf Stream 
have been known to practically exterminate an abundant species.. 
The oyster- grounds of southern New England and New York suffer 
severely through the depredations of drills and starfishes, and epidem- 
ics of disease are not uncommon among the food-fishes of the interior 
lakes. 
Precise methods of investigation are, therefore, necessary to deter- 
mine the actual cause of decrease and to furnish the proper informa- 
tion on which remedial measures may be based. The character of 
these inquiries must vary with that of the fishing-grounds, and in ac 
cordance with the habits of the several species whicli are concerned. 
The remedies may be effected in two general ways — by legislation or 
by artificial propagation. A judicious protection of the grounds might 
in many cases be sufficient, but the laws hitherto enacted have not gen- 
erally been very beneficial, owing partly to their inefficiency and partly 
to the careless manner in which they have been enforced. Fish-culture 
has, however, proved a very effective means for improving the con- 
dition of many depleted grounds, and its utility has long ceased to be 
problematical. 
THE INCREASE AND DISSEMINATION OF FISHES. 
The objects of fish-culture are, first, the maintenance or increase of 
existing fisheries, and second, the formation of new fisheries. The 
former relates chiefly to depleted grounds, the latter to grounds which 
have never been sufficiently productive. In order to carry out these 
purposes effectively the aid of science must be invoked, and its assist- 
ance is required in nearly every step taken. The actual operations of 
propagation, the collecting and patching of the eggs, and the rearing 
and distribution of the embryos are dependent for their success upon 
the close observance of natural laws. It is essential to know the breed- 
ing habits of the species, the spawning places and seasons, the charac- 
ter and number of the eggs, tbe manner in which the latter can be 
fecundated and incubated artificially, the duration of the period of in- 
cubation, the developmental history of the embryo and the length of 
time it should be kept in captivity, the kind of food adapted to the 
young, and the proper localities for its planting, where it may find 
nourishment and freedom from its enemies. 
In case the object of propagation is to replenish depleted grounds 
with a species native to them, the chief precaution to be taken is to 
