MUSICK: SEASONAL DISTRIBUTION OF SIBLING HAKES 



GULF OF MAINE 



SUMMER 

 n- 709 



,^^. 



WINTER 

 n:976 



25 



3 4 5 6 7 a 9 '0' I 12 13 14 3 4 5 6 7 8 9 10 M I2 13 14 15 2 J 4 5 6 7 



SOUTHERN NEW ENGLAND 



j t*^ 



^ 



4 5 6 7 8 9 <0 I) [2 13 14 15 16 



4 S 6 7 a 9 O II 12 1314 15 



TEMPERATURE (°C) 



nil 



S456789I0I 



Figure 14. — Seasonal catch per tow of mature Urophycis 

 chuss off southern New England and the Gulf of Maine. 

 Abundance data are stratified by temperature intervals of one 

 degree (C). The total number of individuals captured during 

 each season = n. The number of stations occupied at each 

 temperature is indicated above each respective histogram bar. 



(Edwards, 1958a; Edwards and Lawday, 1960) 

 and increased in abundance until August. Thus 

 mature U. chuss are abundant in the summer at 

 depths less than 30 fm. The Albatross IV survey 

 data (Figure 13) which show highest values of 

 abundance in strata 60 fm and deeper are 

 probably not indicative of the true summer dis- 

 tribution off/, chuss. Both the industrial fishery 

 and region of greatest abundance in the Albatross 

 IV survey are in the southwestern section of the 

 Gulf, but the fishery and survey data were taken 

 at different depths. Additional evidence that U. 

 chuss congregate in the summer at depths less 

 than 30 fm comes from Bigelow and Schroeder 

 (1953). They noted that U. chuss spawns in the 

 Gulf in the summer and that most eggs and larvae 

 have been collected close to shore. Water tem- 

 peratures inshore are comparable to those that 

 occur in known offshore spawning areas of U. 

 chuss off southern New England (5°-10°C). Similar 

 temperatures also occur in deeper waters of the 

 Gulf, but young U. chuss spawned in such areas 

 would have little chance of finding Placopecten 

 for shelter after descending because Placopecten 

 is restricted to shoal areas of the Gulf (Dow and 

 Baird, 1960). Therefore, there may be selection 



for inshore spawning in the Gulf of Maine. 



During the fall (Figure 15), mature U. chuss 

 were dispersed over the entire survey area, but 

 the original data (Musick, 1969) show that most 

 individuals longer than 32 cm had moved into 

 water deeper than 60 fm. The winter distribution 

 pattern of mature U. chuss (Figure 16) shows that 

 a very strong offshore movement occurred in water 

 deeper than 60 fm, in the Gulf of Maine, and off 

 southern New England. The fish were most 

 heavily concentrated along the edge of the conti- 

 nental slope from the southwest part of Georges 

 Bank to Hudson Canyon. Edwards et al. (1962) 

 reported U. chuss to be most abundant in winter 

 between 100 and 250 fm in their study area south 

 of Nantucket. In addition, Edwards et al. (1962) 

 found that U. chuss were "most abundant where 

 the water temperature was between 47°F (8.3°C) 

 and 50°F (10.0°C)," values which are within the 

 range which adult hake were most abundant in 

 the present study (5-12°C). 



Juvenile and immature U. chuss occurred with- 

 in a narrower temperature range than the adults. 

 However, the latter were more concentrated 

 within relatively narrow temperature limits. 

 This implies that although adults may tolerate 

 a wider range, they may prefer a narrower range 

 than young fish do or, at least, are more mobile 

 and can undertake longer and faster seasonal 

 migrations, thus remaining within relatively nar- 

 rower temperature limits throughout the year. 

 Such behavior might allow the fish to maintain 

 an optimal thermal environment for gonadal 

 development, spawning, and feeding during 

 various times of the year. 



Figure 15. — Distribution and abundance of mature Urophycis 

 chuss during the fall. Abundance in each sampling stratum is 

 indicated on a log scale. 



489 



