THE PROBLEM OF BRIGHT-COLORED FISHES 



511 



In the same region among the Poma- 

 centrids, the sergeant major, Ahudrfduf 

 saxatilis, is everywhere common, a \ellow 

 fish with vertical bUick cross bars. x\t 

 Porto Rico anotlier Ahudcfduf occurs 

 commonly with it, which may be recog- 

 nized by an equally bold but quite 

 dissimilar color pattern. Unfortunately, 

 the writer in a recent visit to that island 

 was able to obtain only the very young 

 of the second species, the identity of 

 which cannot be satisfactorily deter- 

 mined; but larger ones were seen. 

 Relatives of Abudefduf, one or more 

 brightly colored members of the genus 

 Eupomaccntrus, are always present. The 

 commonest one has striking yellow and 

 blue color contrasts. Several butterfly 

 fish {Chwiodon) are characteristic of the 

 same waters, readily differentiated from 

 one another by the bold bars and eye- 

 like spots which characterize their vari- 

 ous patterns; and among the most 

 striking of our American fishes are mem- 

 bers of the same family, the long-finned 

 blue and yellow angel fish Angclichthys, 

 and Holacanthus tricolor, bright yellow 

 or orange with a jet black center. Three 

 species of blue angel fish [Angelichthys), 



recognizable by color differences, have 

 recently been found at Key West. 



In the writer's opinion it is of value to 

 each species to possess some distinctive 

 badge or uniform separating it from its 

 neighbors, and this accounts in part for 

 the bright colors. For the rest, the 

 security which the innumerable crags 

 and crevices of the reef afford, makes it 

 possible for reef fishes to flaunt in safety 

 banners which, if shown in the open, 

 would but court destruction. Professor 

 Reighard has called attention to this 

 latter fact in speaking of the bright 

 colors of reef fishes as " immunity colora- 

 tion." The case is not unlike that of 

 gaudy tropical birds which can vanish 

 among the dense foliage whenever their 

 splendor attracts unfavorable notice. 

 In conclusion, the bright colors of reef 

 fishes are believed to be of value to them 

 for differentiation and recognition pur- 

 poses. As in the past, it is easy to ad- 

 vance theories to explain, but it still 

 remains for any one to gather sufficient 

 proof on the subject to convince not only 

 himself, but also others. This would 

 seem an interesting field for some in- 

 vestigator at a marine biological station. 



The sergeant fish (Abudefduf saralilis) is readily recognized on the reef by its bold black and yellow bars, and 

 is one of the most abundant tropical fishes. The very young, no larger than one's finger nail, and looking precisely 

 like the adults, can be found in numbers swimming in shallow rock pools left by the tide 



