Creaser and Perkins: Distribution, food, and abundance of Pomatomus saltatrix 



497 



reader using a compound microscope with transmit- 

 ted polarized light at 100-200x. Counts were rarely 

 accomplished in a straight line; it was usually nec- 

 essary to traverse the otolith in either a general dor- 

 sal or ventral direction to complete a count because 

 daily growth rings in many portions of the otolith 

 are obscure. Each counting pathway was usually dif- 

 ferent. The criterion of Nyman and Conover (1988) 

 was used: if one of three counts differed by >10%, an 

 additional count was performed and the value that 

 differed by >10% was discarded. The mean of the 

 three remaining counts was recorded. Dates of first 

 ring deposition for juvenile bluefish collected from 

 all sources were backcalculated from the number of 

 growth increments counted. 



Estimates of swimming speed and swimming 

 distance 



The distance juvenile bluefish were capable of swim- 

 ming per day was calculated from estimates of the 

 average body length during migration and the rela- 

 tionship between swimming speed and average body 

 length. Average body length was equal to one-half 

 the mean size of fish collected during a 2-week pe- 

 riod immediately following first appearance at a sam- 

 pling site minus 2 mm, the size at hatching (Deuel 

 et al., 1966). The swimming speed for fish such as 

 salmon, cod, and herring is about three times the 

 body length/sec for fish measuring 10-100 mm 

 (Harden Jones, 1968). Juvenile bluefish measuring 

 155-213 mm TL swam at speeds averaging 94 mm/ 

 sec at 20°C and 180-260 mm/sec when cooler water 

 was added (Olla et al., 1985). We estimated swim- 

 ming speed of juvenile bluefish at no more than 2 

 body length/sec. 



The mean size of juvenile bluefish collected from 

 the Marsh River during a 2-week period immediately 

 following their first appearance in 1990 and 1991 was 

 108 mm FL (n = 17) and 101 mm FL (/i=19). Total 

 growth between hatching and appearance at the col- 

 lection site in 1990 was 106 mm ( 108 mm minus 2 

 mm [the size at hatching]) and in 1991, 99 mm. The 

 average size of the fish during this migration would 

 be one-half these values or 53 and 50 mm. Swim- 

 ming distances per day during migrations in 1990 

 and 1991 were 53 mm x 2 (twice the body length) = 

 106 mm/sec (9.16 km/day) and 50 mm x 2 = 100 mm/ 

 sec (8.64 km/day). Similarly, the mean size of juve- 

 nile bluefish collected from Sagadahoc Bay during 

 August 1990 was 48 mm FL (n=29). The swimming 

 distance per day was therefore 23 mm x 2 = 46 mm/ 

 sec (3.97 km/day). 



The shortest distances between the northern por- 

 tions of the spawning grounds in the South Atlantic 



Bight to the collection site in the Marsh River and 

 the Middle Atlantic Bight to the collection site in 

 Sagadahoc Bay were estimated at 1350 km and 425 

 km respectively. 



Statistical analysis 



The relationship between fork length and the num- 

 ber of daily rings for juvenile bluefish captured in 

 Maine during 1990-91 was described by linear re- 

 gressions, whereXis the log 10 of fork length and Y is 

 the number of daily rings. Slopes were then compared 

 with ANCOVA. The curvilinear relationship of the 

 same data from Maine (1990-91) and New York 

 (1985-86) was described by quadratic equations, 

 where X is fork length and Y is number of daily rings. 

 The relationship of fork length to growth rate for 

 combined data from Maine was described by a lin- 

 ear regression, where X is the fork length and Y is 

 the rate of growth. 



Results and discussion 



Records of juvenile bluefish from the coast 

 of Maine 



Most records of juvenile bluefish were from south- 

 western Maine (York, Cumberland, Sagadahoc, and 

 Lincoln counties) during the months of July, August, 

 and September (Table 1). Fish varied in size from 37 

 to 197 mm FL (39-218 mm TL) from both oceanic 

 and estuarine environments. Atlantic puffins 

 (Fratercula arctica ar-ctica ), Arctic terns (Sterna para- 

 dioaea ), and roseate terns (Sterna dougallu dougalli) 

 were reported as feeding on young-of-year bluefish 

 in July near Matinicus Rock and Seal Island (Knox 

 County). 3 These observations indicated that juvenile 

 bluefish occur in the offshore waters of Maine prior 

 to their usual appearance inshore during August- 

 September. Clark ( 1973 ) observed that juvenile blue- 

 fish remain where salinities are high when they first 

 arrive, and later, as summer progresses, they pen- 

 etrate into estuaries. Little Kennebec Bay (Table 1, 

 No. 28) is the most northeast location where the cap- 

 ture of juvenile bluefish was confirmed. Three juve- 

 nile bluefish were among 1,000 age-1 Atlantic her- 

 ring, Clupea harengus, tagged at this location on 25 

 August 1983 (Creaser and Libby, 1986). 



Young-of-year (YOY) bluefish may be more abun- 

 dant northeast of Boothbay Harbor than suggested 

 by Table 1. The scarcity of information from this area 



3 Kress, S. Cornell Univ. Ornithology Lab, Ithaca, NY. Personal 

 commun, January 1991. 



