XLII REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
acteristics and conditions. The most important grounds, however, are 
located in the seas, in the lower courses of the large rivers, and in the 
great lakes, some fishes living upon the bottom and others at or near 
the surface. Assuming the bottom grounds to be most typical, we may 
summarize as follows the principal information essential to the fisher- 
men which can be gained by proper scientific observations: The posi- 
tion, extent, and outline of the grounds ; the depth of water upon them 
and the character of the bottom ; the kinds of useful fishes which in- 
habit each, and their abundance, size, and utility; their breeding and 
feeding habits, affecting, to some extent, their quality for food at differ- 
ent times; their migratory habits, which explain the periodic shifting 
of the grounds from one locality to another; the character and abun- 
dance of the food, and certain physical conditions upon which the per- 
manence of the grounds depends; the distance of the grounds from 
markets and the meteorological characteristics of the region, as deter- 
mining the period and duration of the fishing season and suggesting 
the character of fishing vessels to be employed; the kinds of bait best 
suited to each fishery and the -places where sufficient quantities maybe 
obtained. 
These inquiries belong to three different branches of research — hy- 
drography, physics, and biology, although the two former may, in a 
measure, be combined. Hydrography, in its limited sense, deals with 
the topography of the bottom, the depth of water, and other matters 
upon which the charting of the grounds is based. Work of this char- 
acter is performed by the Coast Survey and Hydrographic Office for 
the benefit of commerce, but the requirements of the fisheries in this 
respect have not been fully met by their investigations, necessitating 
that the Fish Commission vessels be well equipped for the same serv- 
ice. The physical observations relate to the temperature and density 
of the water, the character, direction, and force of currents, and to 
atmospheric conditions and other kindred subjects. These matters, in 
conjunction with hydrographic features, determine the limits of faunas, 
and thereby the distribution of useful as well as other fishes; they 
also regulate the movements of migratory species and the methods of 
the fishermen. The inquiries regarding them are most important with 
respect to the more active pelagic species, such as the mackerel, blue- 
fish, and menhaden, and the anadromous species, like the shad and 
salmon, but they are essential to the solution of all fishery problems, 
whether these relate to the oyster beds between tides or to the greatest 
depths frequented by food-fishes, to the river systems or to the lakes and 
seacoasts. The biological investigations have reference to the products 
of the grounds and make known the different economic species which 
inhabit each region, their abundance, the purposes for which they can be 
utilized, and the seasons during which they may be found. The charac- 
ter and amount of the lower forms of life existing in each locality indi- 
cate the permanence of the grounds, and to a great extent the kinds of 
