JONES: niKFKKKNCKS IN I,AK\AI, IIKKKINC CKOW'I'II 



hatched later. Intercepts were not compared since 

 the data sets did not contain any larvae with fewer 

 than seven increments and inferences outside the 

 range of the data should not be drawn. 



1976-77 Study 



A frequency plot of hatching dates for the Gulf of 

 Maine stations is shown in Figure 1 for age esti- 

 mated on the assumption of daily ring deposition and 



in Figure 2 for age estimated on the assumption that 

 deposition was daily or as little as one ring every 

 other day. 



Differences in length-at-increment count between 

 early- and late-hatched larvae was striking (Table 2). 

 Regression plots are shown in Figure 3. Analysis of 

 the data confirmed that the length-at-count data 

 were modeled more accurately by two different 

 regression lines (P < 0.01) and that the slopes of 

 these two regressions were significantly different (P 



LARVAL HERRING 



1976-1977 STUDY 



15-1 



UJ 



< 

 > 



% 10 



GC 



UJ 



m 



z 



o^ 



SEPT 1 



1 

 SEPT 1 



"^ 



OCT 1 



NOV 



OCT 



NOV 1 



DEC 1 



DATE OF HATCHING 



Figure 1 . - Frequency of Atlantic herring hatching during the 1976-77 study. Upper scale gives the day of hatch based on 

 the Lough et al. (1982) aging method, or, as discussed in the text. Lower scale gives the day of hatch based on Townsend 

 and Graham's (1981 ) aging method as discussed in the te.xt. Arrow indicates division point between early- and late-hatched 

 classification. 



Table 2. — Regression analysis of 1976-77 Gulf of Maine Atlantic herring data. 



et al. 1982.) 



(Data from Lough 



Data were classified Into early- and late-hatched larvae. These two groups were compared 

 by fitting ordinary least squares regression lines to 1) all the data within the two classifications, 

 and 2) using only lengths from larvae with 60 or fewer increment counts. Slopes and intercepts 

 were compared between early versus late for each group. 



291 



