420 



BULLETIN OF THE BUREAU OF FISHERIES 



Nigripinnis has also a much longer maxillary, a somewhat longer head relatively, 

 and is more pigmented, especially on the paired fins, than the herring. The ven- 

 trals, particularly, are darker in nigripinnis. 



Discussions of the differences between nigripinnis and johannas, cdpenae, zeni- 

 thicus, and reighardi are found on pages 352, 365, 389, and 402. 



GEOGRAPHICAL DISTRIBUTION 



My data on the occurrence of the blackfin in Lake Michigan are given in Table 

 40 and are shown platted on the chart in Figure 4. There are 20 records, all but 5 

 of them from personal observation on the commercial catches of the chub nets. A 

 few individuals have been taken out of most of the ports visited, and the data indi- 

 cate that the species may be found, at least occasionally, throughout the lake at 

 suitable depths. 



BATHYMETRIC DISTRIBUTION 



The data in the aforementioned table are derived almost exclusively from an 

 examination of the catches of the 2% to 2% inch chub nets and from the testimony 

 of fishermen. They show the blackfin to have been taken at depths of 30 to 90 

 fathoms. With the exception of the two lifts out of Michigan City on September 3 

 and October 11, 1920, in 30 to 40 fathoms (records 10 and 11), no individuals oc- 

 curred in about 12 catches examined from nets lifted out of less than 40 fathoms, 

 not including the sets on the spawning grounds of zenithicus and hoyi. None ever 

 have been seen by me from either the 4 or 43^ inch trout and whitefish nets or the 

 13^-inch bait nets set usually at depths of less than 50 fathoms. (See p. 354.) The 

 testimony of the fishermen, who undoubtedly know the blackfin, establishes its habitat 

 in the deeper waters of the lake, and it is probable that the blackfin does not range 

 outside of the 30-fathom contour. The outer limit of its range is not known. 



RELATIVE ABUNDANCE 



My observations on the abundance of the blackfin were made during the summer 

 and fall of 1920 and in the summer of 1923 from an examination of the catches of 

 the 2^2 to 2% inch chub nets. Few chubs of any kind were taken in 1920. (See 

 p. 354.) The fishermen, moreover, are unanimous in the opinion that blackfins are 

 taken commonly only in nets of 3-inch or larger mesh, so that my observations show 

 nothing conclusive on the present abundance of this species. (The small fish appar- 

 ently do not consort with the largest ones and apparently not even with the other 

 chubs. This does not seem to be true of the species in Lake Huron.) In each 

 of the lifts made out of the following ports a few specimens were taken: Out 

 of Washington Harbor, Wis., on August 19, 1920, 20 miles E. ]/ 2 N. of Rock 

 Island in 71 to 90 fathoms (record 1); out of Sturgeon Bay, Wis., on August 23, 

 1920, 12 miles E. by S. of the ship-channel mouth in 60 to 70 fathoms (record 2); 

 out of Port Washington, Wis., on September 25, 1920, 18 miles E. Y 2 S. in 65 to 48 

 fathoms, and on May 26, 1922, 24 miles E. by N.in 60 to 80 fathoms (records 3 and 

 4); out of Milwaukee, Wis., on March 24, 1919, in 50 fathoms, and on September 

 23, 1920, 27 miles ESE. in 60 fathoms (records 5 and 6); out of Michigan City, Ind., 

 on September 3, 1920, and on October 11, 1920, 22 miles NW. by N. y 2 N. and 20 



