NOTE Lang et al.: Use of otolith microstructure in resolving first year growth and spawning seasonality of Urophyas tenuis l 7 I 



demersal habitat (Hunt, 1982) or during the first 

 winter when the fish are about six months of age 

 (Clay and Clay, 1991). 



The hyaline check observed on white hake otoliths 

 is probably analogous to checks that have been docu- 

 mented on the otoliths of other gadoid species such 

 as Barents Sea cod, Gadus callarias (Trout, 1954); 

 silver hake, Merluccius bilinea/is (Hunt, 1980; Dery, 

 1988a); and red hake, Urophycis chuss (Dery, 1988b). 

 Timing of the check on silver hake otoliths was re- 

 solved by Nichy (1969), whose back-calculated 

 lengths at the time of check formation corresponded 

 well with the size at which silver hake become dem- 

 ersal. A similar check on the otoliths of capelin, 

 Mallotus villosus, was also shown to be formed when 

 the fish undergoes metamorphosis (Bailey et al., 

 1977). These studies support the assumption that the 

 first hyaline zone observed on white hake otoliths is 

 a check, probably formed when pelagic juveniles 

 settle into a demersal lifestyle. To date, however, 

 there has been no direct determination of the timing 

 of this check. 



The objectives of this study are to determine the 

 timing and nature of the check on white hake otoliths, 

 to estimate the daily growth rates of juvenile white 

 hake, and to estimate spawning dates of these juve- 



niles in order to evaluate Fahay and Abie's (1989) 

 theory that there are two distinct spawning stocks 

 of white hake in the Gulf of Maine-Georges Bank 

 region. 



Methods 



Juvenile white hake were obtained from archived 

 specimens collected from several locations off the 

 northeast coast of the United States throughout the 

 mid-Atlantic Bight, Georges Bank, and Gulf of Maine 

 (Fig. 1). Collection dates ranged from June 1986 

 through September 1992. Sampling gears that suc- 

 cessfully captured white hake included MOCNESS 

 (multiple opening-closing net and environmental sens- 

 ing system), otter trawl, and beach seine (Table 1). 



In the laboratory, fish were measured to the near- 

 est 0.1 mm TL and all otoliths were removed. Sagittae 

 were stored whole and dry and were examined with 

 a dissecting microscope for the presence of hyaline 

 zones. Each pair of lapilli and asterisci were mounted 

 whole on glass slides and examined with a compound 

 microscope to enumerate daily rings. Both the 

 sagittae and asterisci of the juveniles were irregu- 

 larly shaped and difficult to age. Lapilli, which had 



38 



74 



72 



~^ 



'•vK &i 



Geo-e!!^' 



50 fm 



Figure 1 



Locations of juvenile white hake, Urophycis tenuis, samples by year of collection 



