HADDOCK FROM GEORGES AND BROWNS BANKS 



185 



After this report was begun, the Albatross III 

 completed its 1950 summer census on Browns 

 Bank and there became available a means of 

 testing this hypothesis: If true, the 3- and 4- 

 year-ohls taken in 1950, rather than the 2- and 

 3-year-olds in 1949, might be found to be smaller 

 than expected. To investigate this, we com- 

 l)uted the average size at each age of all haddock 

 from which scales were taken on Browns Bank 

 in 1950. These average lengths in centimeters 

 are as follows: 



Areraee Number 



Imfflh included 



1-year-olds 19.3 43 



2- year-olds 26. 3 141 



3-year-olds 31.5 122 



4-year-olds 38. 5 1 64 



5-year-olds 48. 1 80 



6-year-olds 51.4 162 



7-year-olds 55. 1 117 



If these values are plotted it can be seen that 

 the points for 3- and 4-year-olds do fall below 

 the general trend. Thus it appears that the 1946 

 and 1947 year classes actually had smaller at- 

 tained sizes, and this appears to be a reasonable 

 explanation for not obtaining a smooth growth 

 curve from the 1949 collection of data on Browns 

 Bank. 



A completely chance sampling of a homogeneous 

 population in nature is difficult to obtain, but we 

 believe that our sampling was sufficiently repre- 

 sentative to confirm the differences described here. 

 Fii-st, the haddock were caught over several 

 hundred square miles of Georges Bank and over 

 about 100 square miles of Browns Bank. Such 

 large areas were not covered thoroughly, of course, 

 but the net was set at random within them. Sec- 

 ond, the same otter-trawl net was used on the two 

 banks and it should have sampled similarly the 

 same-size fish on the two banks and unquestionably 

 should have made no selection of different ages 

 at the same size. Third, from extensive (un- 

 published) studies of the catch of the commercial 

 fleet on Georges Bank we know that haddock 

 from different parts of Georges Bank grow at 

 rather similar rates. The other possible objection 

 to the tests of significance concerns the "normal- 

 ity" of the size distributions for various ages. 



Inspection of figure ^indicates that all curves are 

 close to normal except the flat-topped one for 2- 

 year-old haddock from Browns Bank; even this 

 one instance of kurtosis should have little effect 

 on the tests of significance. 



SUMMARY 



The haddock on Georges anri Browns Banks 

 grow at different rates. One-year-old haddock 

 averaged 22.7 centimeters on Georges Bank as 

 compared with 17.9 centimeters on Browns; 2- 

 year-olds averaged 36.6 on Georges, 22.4 on 

 Browns; 3-year-olds were 43.2 on Georges, 30.6 

 on Browns; 4-year-olds were 49.4, and 41.1; and 

 5-year-olds were 52.4, and 46.4. This difference 

 indicates that hereditary or ecological condi- 

 tions governing growth are different in the two 

 areas and that important intermigrations of the 

 bottom-dwelling stages of haddock do not occur. 

 As a consequence, we need not expect the stocks 

 to fluctuate simultaneously and we should con- 

 tinue to collect and to analyze separately for the 

 two areas the statistics of landings, age, growth, 

 abundance, and other biological data. 



LITERATURE CITED 



Herrinoton, William C. 



1944. Factors controlling population size. Trans. Ninth 

 Am. Wildlife Conf., pp. 250-263. 

 Needler, a. W. H. 



1930. The migrations of haddock and the interrelation- 

 ships of haddock populations in North American 

 waters. Cont. Can. Biol, and Fish., N. S., vol. 6, 

 No. 10, pp. 241-314. 



ROUNSEFELL, GeORGE A. 



1942. Field experiments in selecting the most efficient 

 tag for use in haddock studies. Trans. Amer. Fish 

 Soc, vol. 71, pp. 228-235. 



SCHROEDER, WlLLI.^M C. 



1942. Results of haddock tagging in the Gulf of Maine 

 from 1923 to 1932. Ssars Foundation: Journal 

 Marine Research, vol. 5, No. 1, pp. 1-19. 

 Vl.\dykov, Vadim D. 



1935. Haddock races along the North American Coast. 

 Biol. Bd. Can. Prog. Report, No. 14, pp. 3-7. 

 Walford, Lionel A. 



1938. Effect of currents on distribution and survival of 

 the eggs and larvae of the haddock (Melanogrammus 

 aeglefinus) on Georges Bank. U. S. Bureau of Fisher- 

 ies Bull. 29, 73 pp. 



U. S. GOVERNMENT PfilKTING OFFICE O — 1952 



