556 



Fishery Bulletin 91(3). 1993 



tn 



c 

 « 



D 

 O 



I 

 O 



O 



700 



600 



500 



400 



300 - 



200 



100 



Figure 2 



Mean catch at age of Georges Bank haddock Melanogrammus aegleftnus, 

 1982-1988, based on different levels of aggregation in the age-length key. 

 Unpooled commercial refers to quarterly age-length keys derived solely 

 from commercial samples. Pooled commercial refers to age-length keys 

 derived solely from commercial samples, but with quarter- 1 and quarter-2 

 data pooled into a single age-length key Pooled and unpooled commercial 

 and survey refer to the same levels of temporal aggregation as above 

 but include age-at-length data obtained from fish collected in the NEFSC 

 bottom trawl surveys. Vertical lines indicate 2 SE of the mean catch 

 at age. 



I unpooled commercial 



| pooled commercial 



J unpooled commercial and survey 



J pooled commercial and survey 



Figure 3 



Mean coefficient of variation of estimates of catch at age for Georges Bank 

 haddock Melanogrammus aeglefinus, 1982-1988, based on different levels 

 of aggregation in the age-length key. Symbol definitions as in Figure 2. 



Literature cited 



Azarovitz, T. R. 



1981. A brief historical review of the Woods 

 Hole Laboratory trawl survey time 

 series. In W. G. Doubleday and D. Rivard 

 (eds.), p. 62-67. Canadian Spec. Publ. 

 Fish. Aquat. Sci. 58. 



Bennett, B. M., and P. Hsu. 



1960. On the power function of the exact 

 test for the 2x2 contingency table. Bio- 

 metrika 47:393-397. 

 Bishop, Y. M. M., S. E. Fienberg, and P. W. 

 Holland. 



1975. Discrete multivariate analysis: 

 theory and practice. MIT Press, Cam- 

 bridge, MA. 

 Clark, S. H., W. J. Overholtz, and R. C. 

 Hennemuth. 



1982. Review and assessment of the 

 Georges Bank and Gulf of Maine haddock 

 fishery. J. Northwest Atl. Fish. Sci. 3:1- 

 27. 



Cochran, W. G. 



1952. The x 2 test of goodness of fit. Annals 

 of Mathematical Statistics 23:315-345. 

 D'Agostino, R. B., W. Chase, and A. Belanger. 

 1988. The appropriateness of some com- 

 mon procedures for testing the equality 

 of two independent binomial popula- 

 tions. Am. Statistician 42:198-202. 

 Gavaris, S., and C. A. Gavaris. 



1983. Estimation of catch at age and its 

 variance for groundfish stocks in the New- 

 foundland region, p. 178-182. In W. G. 

 Doubleday and D. Rivard (eds.). Sampling 

 commercial catches of marine fish and 

 invertebrates. Canadian Spec. Publ. 

 Fish. Aquat. Sci. 66. 



Gavaris, S., and L. Van Eeckhaute. 



1990. Assessment of haddock on Eastern 

 Georges Bank. Canadian Atl. Fish. Sci. 

 Advisory Comm. Res. Doc. 90/86, 37 p. 

 Grosslein, M. D. 



1969. Groundfish survey program of BCF 

 Woods Hole. Commer. Fish. Rev. 31:22- 

 30. 

 Haberman, S. J. 



1988. A warning on the use of Chi-squared 

 statistics with frequency tables with small 

 expected cell counts. J. Am. Statistical 

 Assoc. 83:555-560. 

 Hennemuth, R. C. 



1965. Homogeneity of age-length frequen- 

 cies among months and quarters of the 

 year for haddock caught on Georges Bank, 

 1962. Int. Comm. Northwest Atl. Fish. 

 Res. Bull. 2:76-76. 



