STUDYING THE HABITS OF FISHES. III9 



become readily habituated to the presence of the observer. In addition to these 

 advantages the habits of fishes are of more interest during the breeding season 

 than at other times, and a knowledge of them is of the greatest consequence from 

 the practical standpoint. At other seasons many fishes are in water so deep 

 that they can not well be observed; or they are in other ways inaccessible. 

 Nevertheless, in so far as fish are accessible outside of the breeding season, the 

 principles that have been discussed in the preceding paragraphs may be applied. 



Not only is it possible to observe the breeding habits of fishes in the field, but 

 in the case of many species the breeding continues when the fish are confined in 

 aquaria. In this respect there is a very great difference in species. In spite of 

 repeated efforts I have never succeeded in observing any part of the breeding 

 habits of dogfish (Amia) when the fish were under the least restraint. Dogfish 

 that I confined in inclosures of netting on the natural spawning grounds refused 

 to breed, even when the inclosures were 4 square rods in area. The Michigan 

 grayling in its native waters did not breed, in the experience of the Michigan 

 Fish Commission, when confined in a portion of the stream separated from the 

 remainder by gratings at its ends, even when the part of the stream available for 

 the fish was many rods in length. On the other hand, I have observed in 

 aquaria the breeding operations of Lampetra wilderi, Catostomus commersonii, 

 Semotilus atromaculatus , Rhinichthys atronasus, and Eupomotis gibbosus. It is 

 well known that the European sticklebacks breed readily in aquaria, although I 

 have never succeeded with our American Eucalia. Undoubtedly the most 

 noteworthy work in observing the breeding habits of fish in aquaria was that of 

 Carbonnier (1869, 1870, 1872, 1872a, 1874, 1875, 1876, 1876a, 18766, 1879, 1881) 

 at the aquarium of the Trocadero in Paris. A number of Indian, Chinese, and 

 other exotic fishes bred there as though under no restraint. 



To secure apparently normal breeding of fish in confinement the temperature 

 of the water and the food of the fish must be regulated so as to be as nearly as 

 possible that of the natural environment. Such regulation can be accomplished 

 only approximately, so that the breeding habits of fishes in confinement are 

 probably not quite normal. For this reason it is best to make observations on 

 fish in their native waters wherever this is possible and to resort to fish in 

 aquaria only when no other method is available, or for special purposes. 



MEANS AND DEVICES FOR OBSERVATION. 



Note-taking materials. — For taking notes the writer prefers the aluminum 

 notebook covers, within which loose leaves of note paper are held by a spring. In 

 addition to the well-known advantages of the loose-leaf system, the aluminum 

 covers afford a hard surface for writing, and they keep the note paper from 

 becoming crumpled in the pocket or wet by perspiration. Thus they are prefer- 

 able for all sorts of field notes, but are of especial use about water, since they 

 protect the notes from wetting. A fountain pen filled with a thin carbon ink 

 affords a permanent and legible writing. 



