From the catch per tow and percentage age composition data (figs. 2 and 4) 

 it is seen that 1946, 1948, and 1950 were years m which spawning was relatively 

 successful. The effect that these years of successful spawning have on the catches 

 of the following years is exemplified by the effect that the 1948 year class had on 

 the catch per tow data for 1949 and 1950. The success of the 1948 and 1950 year 

 classes has been further substantiated by the landing of the commercial fleet (Schuck 

 and Clark, 1950). These two year classes have been the mainstays of the haddock 

 fishery during recent years. It is thus evident that census surveys such asflhose 

 conducted with the Albatross III d uring 1948 to 1950 can be very useful in predicting 

 the commercial catch several years in advance. 



Moa:tality rates can also be estimated from surveys of this kind. However, 

 it must be emphasized that these rates are based on an extremely limited sample and 

 as pointed out by Rounsefell and Everhart (p . 15, par. L-9, 1953), it is unsafe to draw 

 any conclusions from them without further verification. In table 2 are presented the 

 mortalities in percentage for various age fish, based on the catch per tow data for 

 1949 and 1950. 



The indicated mortality rate is higher in l-to-4-year-old fish than in 5-to-8- 

 year-old fish. Zero-ring fish were not included because of inadequate sampling, but 

 natural mortality probably makes up a large proportion of the total mortality of these 

 recently spawned fish which occur generally in areas outside those fished extensively 

 by the commercial fleet and are also not retained by the commercial-size gear. The 

 commercial fleet begin catching haddock during their second year (one -year -olds) 

 and one and two-year-old fish make up the bulk of the fish discarded at sea. Thus 

 fishing mortality appears to be an important factor in the depletion of even these 

 younger fish. Young fish occur in large concentrations and in the same locations as 

 the older fish and it is this combination of availability and large numbers that most 

 likely accounts for their high mortality rates . 



Commercial catch records indicate that older haddock (5 years) tend to move 

 to deeper water off the northern edge of Georges Bank where fishing intensity is much 

 less, which fact might explain the decrease in mortality rate of these fish. This 

 movement of older fish into deeper water will be discussed further when the distribu- 

 tion in relation to depth zones is considered. 



Althou^ these mortality rates are based on only 2 -years data, and subject 

 to numerous errors, indications are that of a sample of 100 one-year-old fish 

 only 5 of these survive to be 3 -year olds. Having an accurate knowledge of these 

 mortality rates and their relation to changes in fishing effort, it should be possible 

 by using a similar sampling technique to predict the numbers of marketable fish 

 available in future years from a sample of one-year-old fish. An even better method 



10 



