10 



BULLETIN or THE BUREAU OF FISHERIES 



USE OF THE KEYS 



The various fins and other structures mentioned in the keys are named in the 

 accompanying outline of a haddock, and the simplest way to explain the use of the 

 keys is to use that species as an example, running it down with the outline at hand 

 for reference. 



1 stioisai f iTi Jl 2Tii(lorsd fiu 



Baibel 



• ?'' 2nd. Anal fin 



tstAna-lfin. 



Ventral fin 



Fig. 1.— Diagram of a haddock, explainmg terms used in key 



Turning to section 1, Key A (p. 11), the fish in question evidently fits the 

 second alternative, for it has bony jaws and pectoral fins and is not formed like an 

 eel, which refers us to section 3. As our fish does not have a tubular snout this 

 leads us to section 4, and this in turn to section 5, since neither jaw is greatly pro- 

 longed. There being only one gill opening on each side we go from section 5 to 

 section 7, and from section 7 to section 8, for there is a distinct tail. Since the fish 

 has no sucking plate on the top of the head this leads to section 11, and this in turn 

 to section 12 because the tail fin is nearly symmetrical in outline. Since the fish is 

 not clothed in an armor of bony plates we are referred by the second alternative of 

 section 12 to section 13. In our specimen the anal fin is clearly separated from the 

 caudal, and section 13 therefore refers us to section 14. As all the fins are supported 

 by rays we must go on to section 15, and from there to section IS as there are no 

 fleshy flaps or tags on the sides of the head.'* Our fish does not lie fiat on one side 

 (that is, it is a round, not a flat fish) and therefore it fits the second alternative under 

 section 18, which refers it to section 19, and as there is more than one separate 

 dorsal fin, this leads to Key F, page 13. 



As we have already determined, all the dorsal fins have soft rays, and since there 

 are no spines in any of the fins (a fact easily determined by feeling them) , this sends 

 us to the key to the cod and silver hake families (p. 385). Turning to the first 

 section of the latter we find that the fish fits the first alternative (3 dorsal fins and 

 2 anals), which refers it to section 2, and here the black lateral line and the dark 

 blotch on each shoulder name it a haddock. 



Any other Gulf of Maine species is to be named in the same way, starting 

 with section 1, Key A, and following through the appropriate alternatives as they 

 refer it from section to section. 



* There is a barbel on the chin but this is very different in appearance from the skin flaps around the 3aws characteristic of 

 the few species that fall under the first alternative. 



