424 



BULLETIN OF THE BUREAU OF FISHERIES 



Georgian Bay. — Records 23 to 28 show the blackfin to occur with the other 

 chubs in Georgian Bay at depths similar to those in which it occurs in Lake Huron. 



From these data the conclusion may be reached that the blackfin occurs in the 

 deeper waters of Lake Huron and Georgian Bay. 



BATHYMETRIC DISTRIBUTION 



There are no records of the occurrence of the blackfin in any of the net lifts 

 examined by me from less than 35 fathoms. (See p. 374.) At depths of 35 to 100 

 fathoms it has been found by the chub nets. No catches were seen from more than 

 100 fathoms, but it is likely that the blackfin does occur beyond this limit, inasmuch 

 as record 20 shows a huge haul of chubs from 80 to 100 fathoms, most of which were 

 blackfins. 



RELATIVE ABUNDANCE 



At Cheboygan, Mich., on July 21, 1917, at Rogers, Mich., on July 24, 1917, 

 and at Harbor Beach, Mich., on October 27, 1917 (records 1, 2, and 22), the speci- 

 mens collected were the only ones seen. At all these ports the fishermen distinguish 

 the blackfins from the other chubs, and all agree that the species is met rarely in 

 their waters. On September 28 and 29, 1917, at Cheboygan, and on October 14, 

 1917, at Rogers, on the spawning grounds of zenithicus no blackfins were seen. Off 

 Alpena, Mich., the tugs brought in blackfins more or less abundantly. From the 

 center of the lake northeast of the can buoy, in 60 to 80 fathoms, on September 10, 

 1917 (record 5), September 14, 1917 (record 7), and September 17, 1917 (record 8); 

 August 30, 1919, 18 miles N. by E. y 2 E. from Thunder Bay Island (record 14); 

 September 3, 1919, 28 miles E. 34 S. from the can buoy in 60 to 64 fathoms (record 

 15); in 60 to 70 fathoms on August 7, 1920, 19 miles NE. K N-, on June 30, 1923, 

 17 miles NE. by N. % N., and on July 7, 1923, 13 miles NE. Y 2 N. of Thunder 

 Bay Island (records 16, 18, and 21), blackfins comprised 5 to 24 per cent of the catches. 

 From the center of the lake east of the can buoy in 65 to 80 fathoms on September 

 7, 1917 (record 4), September 12, 1917 (record 6), September 21, 1917 (record 9), 

 September 24, 1917 (record 10), September 26, 1917 (record 11), October 17, 1917 

 (record 12), and October 20, 1917 (record 13), blackfins comprised 30 to 63 per cent 

 of the catches. Three lifts made in 1923 — on June 28, 19 miles northeast of Thun- 

 der Bay Island in 60 to 70 fathoms; July 2, 20 miles E. by N. of the can buoy in 60 

 to 70 fathoms; and on July 5, 18 miles NE. % E. of Thunder Bay Island in 80 to 

 100 fathoms (records 17, 19, and 20), all lifts of over a ton — contained 75 to 90 

 per cent of blackfins. In Georgian Bay at Lions Head, Ontario, on July 30, 1919, 

 only a straggler appeared in the haul made 21 miles east of Surprise Shoal in 60 

 fathoms (record 23). On October 6, 1919, off White Bluff in 70 fathoms most 

 of the fish in a lift of 425 pounds were blackfins (record 24). On July 28, 1919, in 

 a gang lifted off Cape Croker from 52 fathoms four blackfins were taken (record 26). 



From all these data it appears that the blackfin is found in varying numbers 

 in the chub lifts made at depths of 35 to 100 fathoms. Neither the 43^-inch, 

 inch, nor the special 2%-inch nets (see p. 374) have revealed it in less than 35 fathoms. 

 From 35 to 50 fathoms few are taken in the chub lifts. The greatest proportion 



