132 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



D H I J K 



J I L 



10 IS 20 



TEMPERATURE (°c) 



10 IS 20 



10 15 20 



15 20 25 



Figure 17. — Relation between temperature and vertical distribution of lake herring July 19-27, 1952. See figure 1 for 

 locations of stations. The full width of the panel for each station represents 100 percent. 



Table 43. — Length of lake herring taken in oblique sets of gill nets, by depth and season, 1952 

 12-inch-mesh gill nets, all stations combined. Length in inches] 



seasonal character of the fishery. Nearly half 

 (47.2 percent) of the commercial catch is made 

 during the fourth quarter of the year (fall) and 

 a fourth (24.4 percent) during the first quarter 

 (winter). (See table 2.) Production is much 

 lower in the spring (19.5 percent) and summer 

 quarters (8.9 percent). 



Principal gear for taking lake herring are 

 pound nets which fish from the surface to the 

 bottom and are seldom set at depths greater than 

 35 to 40 feet, and gill nets which are set on the 

 bottom at all depths but are effective only 6 to 1 1 

 feet above the bottom.'^ Thus, pound nets can 

 take herring only when the fish are in the shallower 

 inshore waters and gill nets can capture them only 

 when the fish are near the bottom. From figures 

 15 and 16 it may be seen that in June and July 



" In State of Michigan waters gill nets may not be more than 11 feet deep 

 (distance from float line to lead line) ; In Wisconsin the greatest depth allowed 

 (stated In numbers of meshes) is about 6 feet. 



most herring were in water too deep to be taken by 

 pound nets. The same condition most probably 

 held in August, September, and even early 

 October. During the same period the lake 

 herring should have been available to gill nets set 

 in deeper water. Examination of the nets as they 

 were lifted from oblique sets revealed, however, 

 that most of the herring taken in the bottom 15- 

 foot stratum were caught in the upper half of the 

 net section. Because the fish are some 6 to 8 feet 

 above the bottom, commercial fishing with gill nets 

 during the summer period is not productive. The 

 distribution pattern in which some, and at times 

 most, lake herring are above the bottom and out- 

 side the 30- to 40-foot contour provides them a 

 considerable degree of protection from commercial 

 exploitation. In view of the relative inefficiency 

 of present fishing gear, the probability of depletion 

 by the present fishery is small. 



