Van Eeckhaute et a\ Movements of Melanogrammus aeglefmus determined from a population model 



673 



Figure 8 



Relative abundance of haddock on the Canadian side of 5Zj,m by age group from 

 the NMFS spring survey. Ratios were determined as abundance on Canadian side 

 to total abundance in 5Zjm. 



which was first instituted in 1970 by the Interna- 

 tional Commission for the Northwest Atlantic Fish- 

 eries and which was retained by both countries fol- 

 lowing extension of jurisdiction in 1977 (Halliday, 

 1988). The closure, which was put into effect from 

 March to April during 1970-71, was extended to in- 

 clude May in 1972 and at that time an exemption for 

 hook fisheries was introduced. In 1987 the United 

 States extended the period to include February and 

 in 1993, it was further extended to include January 

 through June. The Canadian bottom trawl fishery 

 has traditionally had limited activity during Janu- 

 ary and February except during 1991-93. Since 1985, 

 when Canada and the United States have conducted 

 haddock fisheries only on their respective sides of 



the ICJ line, the U.S. monthly catch of haddock in 

 unit areas 5Zj,m (Fig. 9) generally have increased 

 from January to June, but a sharp decline in land- 

 ings occurred in July and the months following. Ca- 

 nadian landings peaked in June and July, the first 

 two months following the spawning closure period, 

 and decreased gradually to November 



The 6-month net migration rates calculated for three 

 age groups (age 1, ages 2 and 3 combined, and ages 4 to 

 8 combined) displayed a persistent seasonal pattern 

 indicating net movement towards the U.S. side between 

 October and April followed by a return to the Cana- 

 dian side between April and October (Fig. 10). Age-1 

 haddock had the greatest net migration rate to the 

 Canadian side from April to September but also the 



