220 
FOREST AND STREAM 
May, 1919 
THE COLORS OF FISHES 
THAT THE VARIED COLORS OF FISHES SERVE A 
USEFUL PURPOSE IS A REASONABLE HYPOTHESIS 
A FRIEND of the 
writer, interest- 
ed in the colora- 
tion of fishes, has 
asked that he place 
on record a sketch 
of his knowledge and 
i n t e r p retation of 
their coloration. In 
discussing their colors, it is a convenience 
to divide fishes into several groups. 
1. Free-swimming fishes are those 
which spend the greater part of their 
lives moving actively about in the water 
not far from the surface, approaching 
the bottom or floating weed or other float- 
ing objects comparatively rarely or by 
chance. 
2. Bottom and weed fishes are those 
which spend much of their lives near the 
bottom or close to or among floating weed 
and other objects. 
3. Reef fishes are those which spend 
the greater part of their lives moving ac- 
tively in the water, near, or among, the 
intricacies of tropical reefs. 
4. Deep-water fishes are those found 
at considerable depths. 
The colors of free-swimming fishes are 
mostly simple, white beneath, silvery on 
the sides, bluish, greenish or brownish 
above, sometimes more or less mottled 
(Mackerel). 
The colors of bottom and weed fishes 
are more strongly, often intricately, 
marked, generally neutral in tone, paler 
below. 
The colors of reef fishes are the bright- 
est, most contrasted, their markings often 
bold and bizarre. 
Deep water fishes can not be so suc- 
cessfully generalized as to color, but 
among them we find three types which 
are sufficiently prevalent to be worthy 
of discussion, a red type, and one in 
which almost the entire fish is of a dark 
lustrous silver, at moderate depths; and 
a black t 3 T)e in greater depths. 
In the free-swimming group there 
doubtless is a correspondence between the 
color of the upper parts of the fish, and 
that of the water in which it swims. 
Some persons will claim that there is 
little variation in the color of water. 
Such, however, is not the writer’s experi- 
ence. The water of ponds and bays is 
variously brovra ; that of moderate depths 
on continental shelves (off New York, 
Nevirfoundland Banks, North Sea, be- 
tween the Falkland Islands and South 
America), sea-green; that of the deep- 
sea in general (Gulf Stream, Trade-wind 
belts of all oceans, etc.), strong blue, 
etc. This color is what one sees by look- 
ing directly down into the water, not the 
surface color, due more or less to reflec- 
tion, and which varies with weather con- 
ditions. Looked at at the proper angle 
in the right weather the deep sea and a 
muddy pond give the same bright blue 
surface color. 
By JOHN T. NICHOLS 
In general free-swimming fishes from 
brovra waters are brownish above in life 
(Minnows) ; those from green waters, 
green; from blue waters, blue. There is 
a particularly close correspondence be- 
tween the blue of certain off-shore fishes 
(Flying fish, etc.) and that of the water 
in which they are found. 
Conspicuousness is unquestionably a 
detriment to free-swimming fishes. They 
continually prey on, or are preyed upon 
by, quick-sighted fishes or other crea- 
tures; often they both prey and are 
preyed on. Pretty surely their colors 
tend in the main to render them incon- 
spicious — the white of their underparts 
against the bright lower side of the sea 
surface, the brown, green or blue of their 
backs as the case may be, seen from above 
against the corresponding sea color. As 
compared with one of their number dead 
and lying on its back or side, their in- 
conspicuousness often verges on the in- 
visible. That their colors are always 
those that give them the lowest visibility 
is, however, not true. For instance, the 
adult dolphin is more or less bright yel- 
low behind and below, just in that quar- 
ter where a fish is most open to attack. 
As a correlation we may note that the 
size and speed of the dolphin are such 
as to render it practically immune from 
attack, and that the yellow should enable 
these fish, which hunt wide stretches of 
blue water by sight in small schools, 
more readily to keep together. If one 
wished to paint a conspicuous mark in 
this blue water, yellow would perhaps 
be the best color to use. 
T he majority of species, certainly in 
temperate seas, belong to the second 
group of bottom or weed fishes. It 
is in this group that we find species whose 
colors match their surroundings so won- 
derfully that even the most sceptical 
naturalists will admit that they are pro- 
tectively — that is, concealingly — colored. 
Notable examples are the gulf-weed fish, 
found only in the drifting gulf weed, 
and the flounders which lie on the bot- 
tom. The fact of concealing coloration 
here is obvious. 
I am of the opinion that throughout 
this group the colors of the majority of 
the various species tend to conceal them, 
or that they set limits to the conspicu- 
ousness of each. It is sometimes argued 
that when two species of animals with 
the same habits on the same territory are 
differently colored they cannot both be 
concealingly colored. In fact, this is a 
favorite formula 
with those who ar- 
gue against wide ex- 
istence of concealing 
colorations among 
animals. Its weak- 
ness as an argument 
is two-fold. First, 
the habits of no two 
species are exactly alike, or even those 
of the two sexes, or of the young and 
old. Second, concealing coloration is a 
relative matter. With a given environ- 
ment and habits, a single color and pat- 
tern very likely gives the lowest visibility, 
but several different colors and patterns 
may give a sufficiently low visibility for 
the needs of the animal. 
Compared to those of group two, the 
boldly colored reef fishes (Group 3) have 
a high visibility. This statement is 
based on not inconsiderable personal ob- 
servation, and agrees with the observa- 
tions of most naturalists. The reefs and 
their agility enable them to flaunt with 
impunity colors which would be disas- 
trous to other fishes.’ 
T he colors of deep water fishes are 
the most puzzling, perhaps because 
we know least of the habits of this 
group and the conditions under which 
they live. In the deep shadows of the 
ocean depths lighted only by flashes of 
phosphorescence, the frequent black 
fishes would be expected to have a low 
visibility. The red species common in 
intermediate regions where little day- 
light penetrates would also have a low 
visibility, though conspicious at the 
surface, because the light must pene- 
trate so broad a belt of the green or blue 
water before reaching them. It is pos- 
sible that a concealing value accounts for 
the hlack and the red. It is possible that 
the fish obtains physiological benefit from 
the absorption by its body of the faint 
light, an absorption facilitated by these 
colors. The silvery species differ from 
silvery surface fishes in the lack of white 
in the silver, and comparative absence of 
dark backs. Some of the Lantern fishes, 
small silvery, deep-water species which 
come to the surface at night, have scales 
so burnished that the fish form almost 
perfect mirrors. They have a very low 
visibility at night. 
Any naturalist with a wide experience 
of fishes in different habitats will, I 
think, see the force of the grouping pre- 
sented above and agree in the main with 
the generalizations. Of course there are 
exceptions and special cases which it does 
not cover. There is a certain type of 
large-eyed, nocturnal red fish found on 
the reefs which one might readily class 
with the conspicuous diurnal species, 
some of which are red. Most of these 
^ See Reigjard Pub. Tortugas Lab., Carnegie 
Inst., Wash., 2. 1908, 257-326. Nichols, Am. ^fus. 
Journal, Dec.. 1916. 507-511. 
(CONTINTTED ON PAGE 243) 
