92 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 4. — Lake herring taken in experimental gill nets 

 in 1952 



' Weight and sex data lacking for some May collections. 

 2 See figure 1 for location. 



Total length (tip of the snout to the end of the 

 tail, lobes compressed) was recorded to the nearest 

 0.1 inch. Weights measured on a spring scale, 

 with 18-ounce capacity, were recorded to the 

 nearest 0.1 ounce. All lengths are given in inches 

 and weights in ounces unless otherwise stated. 



Samples from the commercial fishery were cap- 

 tured in standard fishing gear designed primarily 

 for lake herring. Netting of pound nets used in 

 the lake herring (and smelt, Osmerus mordax) 

 fishery customarily has meshes (in the pot) of 

 1)4 to 2 inches, extension measure as manufactured. 

 Nets of these mesh sizes are capable of capturing 

 lake herring smaller than any taken from them 

 during this study. Consequently, mesh size need 

 not be considered as a selective factor in the treat- 

 ment of samples from pound nets. Most small- 

 mesh gill nets used in the Green Bay herring 

 fishery have a mesh size of 2% inches (allowable 

 range 2)^ to 2% inches, depending on season, loca- 

 tion, and conditions) extension measure. One col- 

 lection in southern Green Bay was taken from a 

 2)Mnch-mesh gUl net on November 11, 1951. 

 Experimental gill nets used to collect lake herring 

 in the summer and fall of 1952 are described in 

 Vertical Distribution in Green Bay (p. 128). All 

 experimental gill nets were fished from the Service's 

 research vessel Cisco. 



Analyses and discussions in this report include 

 all data that are believed pertinent to the solution 

 of each particular problem. The exclusion of data 

 of doubtful value in some instances causes dis- 

 crepancies in the number of specimens listed in 

 diff'erent tables. Whenever the excluded data 



are extensive or may influence results under alter- 

 nate considerations, the reason for their omission 

 is given. All collections of data used in this report 

 are either taken from the entire catch of a net or 

 are random samples unless otherwise stated. 



EXAMINATION OF SCALES 



Scales for age and growth analysis were taken 

 when possible from the left side of the body in the 

 area just above the lateral line and below the in- 

 sertion of the dorsal fin. Van Oosten (1929, p. 274) 

 stated that this area was selected "* * * after a 

 careful examination had shown that its scales were 

 less variable in shape and size, when compared 

 one with another, than those of other parts of the 

 body." Since the scales of lake herring are loosely 

 attached and are frequently lost in nature, a liberal 

 sample was taken to ensure the inclusion of non- 

 regenerated scales. The scales from each fish were 

 placed in an envelope on which were recorded the 

 species, locality, date, length, weight, sex, condi- 

 tion of sex organs, gear, and name of collector. 

 The "key" scales required to establish the body- 

 scale relation were removed from approximately 

 the center of the area from which routine samples 

 were taken. The location was the same as that 

 used by Van Oosten — the fourth row above the 

 lateral line and immediately below the base of the 

 first ray of the dorsal fin. 



Some scales were mounted on glass slides in a 

 glycerin-gelatin medium. Plastic impressions 

 were made of the others. Each slide carried three 

 or four scales of normal shape and without evi- 

 dence of regeneration. The label on the slide 

 bore the data shown on the envelope from which 

 the scales were taken. Plastic impressions of 

 scales were made by placing six or eight dry, 

 uncleaned scales sculptured side down on a 1- 

 by 3-inch strip of cellulose acetate bearing a 

 serial number corresponding to that on the scale 

 envelope. A second plastic strip was placed 

 over the scales and the two strips were passed 

 through a roller press set at the crushing pressure 

 of cellulose acetate. (See Smith 1954.) The sec- 

 ond strip of plastic holds the scales in position and 

 ensures an even impression which produces a 

 light, clear image. The numbered plastic strips 

 bearing scale impressions were returned to the 

 envelope and thus were not separated from the 

 original data. 



