162 BULLETIN OF THE BUREAU OF FISHERIES. 
There is no evidence whatever for distribution in accordance with temperature 
within the narrow limits of the present region. Most of the species taken in the dredge 
are ones which have a more or less extended northerly as well as southerly range along 
the coast, and it so happens that Pholis gunnelus, the only strictly northern species 
which was dredged with any frequency, was taken at scattered stations throughout 
most of the Sound, but was not recorded from its western end. It is quite likely that 
the local distribution of this fish is limited by the character of the bottom (by preference 
stony) and by the occurrence of certain alge. Those fishes which are recorded with 
greatest frequency at the western end of the Sound are mainly species of flounders and 
skates, which occur predominantly on sandy bottoms. Of the five species thus restricted 
(Raja erinacea, Lophopsetta maculata, Paralichthys oblongus, and, to a less extent, Para- 
lichthys dentatus and Pseudopleuronectes americanus), two are predominantly southward 
ranging, while the other three have ranges which extend about equallv in both directions. 
Thus the character of the bottom in this western area of Vineyard Sound is doubtless 
responsible directly or indirectly for the distribution of these fishes. The case is quite 
different from that of many other organisms which have been considered by us, whose 
presence near the open end of the Sound is to be explained by reference to the lower 
water temperature which obtains there. 
Even if we had a full and accurate knowledge of the local distribution of these 
various fishes, we should hardly expect to find the same dependence upon temperature 
conditions as was found in the case of some other organisms. Since fishes are free to 
move from place to place according to their needs, they are not subject to the constant 
influence of any set of conditions acting throughout the entire life cycle, as is the case 
with fixed or slowly moving organisms. It may well be (see pp. 175-177) that the restrict- 
ing effects of a colder or warmer environment in relation to distribution depend in many 
instances upon its action during the reproductive period alone, and that the adult 
organism itself might be able to thrive under conditions unfavorable to its early develop- 
ment or to its reproductive activity. Indeed it is likely that such a possibility is often 
realized in the case of animals having sufficient powers of locomotion. And it is perhaps 
among the fishes themselves, many of which migrate to warmer waters for the purposes 
of reproduction, that the best examples may be found. 
The distribution of most fishes within the narrow limits of such a region as the pres- 
ent one is doubtless determined chiefly by the occurrence of their food supply. This we 
may say with a high degree of probability, although we may not be able to determine 
many definite cases of correlation between the occurrence of particular species of fishes 
and the particular organisms which serve as their food. In the case of such predom- 
inantly bottom dwelling species as the flounders and the skates, it seems very probable 
that the character of the bottom is an independent factor in determining distribution. 
Such fishes require beds of comparatively clear sand, upon which they rest or under 
which they may find concealment. 
