186 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



sojourn.^" Tlie place wliere fisli are found may be considered by itself^ 

 or as a basis for dividing the fish into different groups. With regard to 

 the former we can distinguish between the uninterrupted and a more or 

 less accidental or periodical, that is, occasionally interrui)ted occurrence 

 of fish. The periods may be daily, yearly, or extend to a longer space 

 of time. With regard to the second point, the fish may be divided in the 

 different groups mentioned below, using as a basis either the character of 

 the water where the fish are found, on the geographical location, or the 

 degree of regularity with which fish make their appearance, the extent 

 of time and space of their periodical appearance, and the greater or less 

 stability as to their i^lace of sojourn. It will be clear, however, that 

 these groups cannot always be distinctly defined, bat that the lines of 

 demarcation are often somewhat vague, especially between the sub- 

 divisions coming under one and the same head. 



A. — With regard to tee character of the vi^ater, fish may 



BE DIVIDED 



1. as to the saltness of the water ^ into 

 a. fresh- water fish, and 



1). salt-water fish (or sea-fish). 



Between these two groups there is, however, a sort of neutral 

 territory, some kinds of fish living in either water. There are 

 also some "sea-fish" which ascend the rivers for the purpose 

 of spawning, their young ones returning to the sea (so-called 

 '-'' anadroms^'') in order to grow to maturity, or in order to satisfy 

 their craving for food, in which case the fish which have grown 

 to matmity in fresh water go into the sea for the purpose of 

 spawning (so-called '■'■'katadroms''''). 



2. as to its degree of agitation (flowing or stagnant water), into 



a. river or brook fish, and 



b. sea or lake fish. 



Among the lake-fish there are likewise some which occasion- 

 ally go up into the rivers. 



B.— With regard to the geographical location, pish may be 



DIVIDED 



1. with regard to their horizontal distribution, into 



a. littoral or coast fish,^i that is, fish which always stay near the coast, 



b. pelagian or sea fish, that is, fish which always, or at least the 

 greater portion of the year, live in the ojien sea. 



"> An entirely diiferent subject, foreign to my present investigation, is the question 

 of the general geographical distribution of fish over the globe, and their geological 

 distribution throughout the ages. 



*' J". S. Lorenz, Phisil-alische Vehaltnissc und TertheUung dtr Organismcn im Quarner- 

 iscTien GoJ/c. Vienna, 1863, p. 332. 



