4 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



preparation of this book would have been out of 

 the question without their help. 



Finally, we have ourselves gathered a large 

 body of data as to distribution, habits, spawning 

 seasons, and like matters, through many years, 

 at many localities, both inshore and on the offshore 

 banks. 



USE OF THE KEYS 



The various fins and other structures mentioned 

 in the keys are named in the accompanying out- 

 lines of a haddock and of a typical shark (fig. 1). 

 A simple way to explain the use of the keys is to 

 use the haddock as an example, running it down 

 with the illustration at hand for reference. 



Turning to Key A (p. 5), we find that our fish 

 fits the second alternative under section 1, since 

 it has bony jaws and pectoral fins, and is not 

 shaped like an eel. This refers us to section 3. 



There being only one gill opening on each side, 

 we go from section 3 to section 5. As our fish 

 does not have a tubular snout section 5 refers us 

 to section 6, and this in turn to section 7, since 

 neither the upper jaw nor the lower is greatly 



1st Dorsal Fin 



prolonged. Since the body is not square-cut close 

 behind the dorsal and anal fins, but has a definite 

 tail part, we proceed from section 7 to section 8, 

 and from section 8 to section 11, for our fish has 

 no sucking plate or disc, either on top of the head, 

 or on the chest. Section 11 refers us in turn to 

 section 12 because the tail fin is nearly symmetri- 

 cal in outline. The anal fin being clearly and 

 definitely separated from the caudal fin, we go 

 from section 12 to section 13; and from section 13 

 to section 14, for our fish does not have any evi- 

 dent light-producing ("luminescent") spots either 

 on its sides or on its head. Our fish does not 

 have a fleshy fin or flap either in front of the ordi- 

 nary dorsal fins or behind them, but all of its 

 dorsal fins are supported by rays that are visible if 

 held against the light. Consequently, we proceed 

 from section 14 to section 18, and this refers us 

 to section 22, there being no flaps or tags of skin 

 on the sides of the head." Our fish obviously 

 does not lie flat on one side, i. e., it is not one of 

 the flat fishes, which brings us to section 23, and 



n There is a barbel on its chin, but this is very different in appearance from 

 the skin flaps around the jaws that are characteristic of the few species that 

 fall under the first, alternative of section 18. 



2nd Dorsal 

 Fin 1 



Baibel 



Ventral fin tst.Ana.lfin 



Figure 1.— Diagrams of a haddock (below) and of a typical shark (above) with terms used in the keys and descriptions. 



