Table 13 . - -Age at maturity for haddock in various geographic areas 



The division of haddock into 1-2 year and 3-9+ year age groups roughly separates 

 these haddock into immature and mature or spawning fish. Thus the age-depth dis- 

 tribution found on the basis of this grouping results from a spawning migration. 



It may be stated, then, that the mature haddock seek shoaler water during the 

 spawning season than during the summer months. That depth is a factor of prime 

 importance in the determination of spawning location is well known and the depth 

 limits of spawning are similar for the various banks. Bigelow and Welsh (1929) state 

 that the important spawning grounds in the Gulf of Maine are all shoaler than 75 

 fathoms, with 15 to 20 fathoms as the upper limit and 100 fathoms as the lower limit 

 of any considerable spawning. They also note that no haddock spawn m the deep 

 basin of the Gulf of Maine (depth zone IV) . Schmidt (1909) and Raitt (1936), using 

 data based on egg distribMion, give 27-109 fathoms as the depth range of spawning 

 for European haddock. Thompson (1929A) from observations on egg distriijufion 

 gives 44-82 fathoms as the range of spawning depth of Icelandic haddock. 'Needier 

 (1930) from information based onflie commercial catch, states that in early spring 

 haddock are caught m abundance in water less than 25 fathoms, and as summer 

 proceeds these fish withdraw to somewhat deeper water. Thompson (1929B) 

 demonstrated that North Sea haddock congregate into spawning and feeding concentra- 

 tions during the spring and summer months and the depth distribution of these two 

 concentrations is seen to be similar to the spring and summer depth distribution 

 observed on Georges Bank. 



It is apparent then that it is a spawning migration to shoaler water that is the 

 cause of the change in the depth distribution of haddock during the spring. TTie depth 

 distribution of Georges Bank haddock during both spring and summer is similar to 



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