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



503 



michogs, Fundulus heteroclitus, and unidentified fish 

 remains (Tables 2 and 3). Other authors reported that 

 a significant portion of the juvenile bluefish diet con- 

 sists of shrimp (Linton, 1905; Wilk, 1977; Friedland 

 et al., 1988), clupeids (Hildebrand and Schroeder, 

 1928; Greeley, 1939; Grant, 1962; Richards, 1976; 

 Naughton and Saloman, 1984), Atlantic silversides 

 (Hildebrand and Schroeder, 1928; Greeley, 1939; 

 Grant, 1962; Lassiter, 1962; Wilk, 1977; Friedland 

 et al., 1988), and cyprinodontids (Greeley, 1939; 

 Grant, 1962; Wilk, 1977). Prey of minor importance 

 included Argulus sp., Corophium sp., Rhithro- 

 panopus harrisii, unidentified Crustacea and isopods, 

 zoea of Majidae sp., polychaete remains, unidenti- 

 fied Hymenoptera, and both leafy and woody plant ma- 

 terial (Table 2). Estuaries in Maine are probably 

 seasonal nursery grounds where high prey densities 

 and warm water temperatures result in rapid growth. 

 During 1990 and 1991, 13.42% and 3.33% of the 

 fish collected in the Marsh River and 26.47% (1991) 

 of the fish collected in Merepoint Bay possessed 

 empty stomachs (Tables 2 and 3). With the excep- 

 tion of the 16% estimate reported by Grant (1962), 

 who also used gill nets, the percent of empty stom- 

 achs reported by several investigators varied between 

 30 and 87%. Perhaps the low incidence of empty stom- 

 achs reported in our studies resulted from the use of 

 gill nets, which constrict the gills and esophagus thus 

 reducing the possibility of regurgitation. 



An analysis of daily growth increments 

 on otoliths 



Growth increments on the otoliths of many species 

 of juvenile fishes, including bluefish, are produced 

 on a daily basis as long as growing conditions are 

 adequate (Nyman and Conover, 1988). Bluefish col- 

 lected from the Marsh River displayed 94-200 

 (1 = 126) and 97-176 ( .v=134) daily growth incre- 

 ments during 1990 and 1991, respectively. Fish col- 

 lected from Sagadahoc Bay (1990) displayed 58-93 

 (v=66) daily growth increments, and fish collected 

 from Merepoint Bay (1991) displayed 125-146 

 ( ,v=134) daily growth increments. First ring deposi- 

 tion occurs approximately 2—4 days after spawning 

 (Nyman and Conover, 1988) so these daily growth 

 increments correspond to a total of approximately 

 129 days (Marsh River, 1990), 137 days (Marsh River, 

 1991), 69 days (Sagadahoc Bay, 1990), and 137 days 

 (Merepoint Bay, 1991) of growth after spawning. 



Spawning occurs somewhere along the Atlantic 

 coast during practically every month of the year 

 (Table 4). Several "seasonal" periods of significant 

 spawning are evident. Major spawning periods oc- 

 cur during the "spring" (March-May) in the South 



Atlantic Bight and "summer" (May-September) in 

 the Middle Atlantic Bight. A minor "fall-winter" 

 (Kendall and Walford, 1979) and perhaps "summer- 

 fall" (Collins and Stender, 1987) spawning period also 

 occurs in the South Atlantic Bight. 



It is unlikely that juvenile bluefish captured in the 

 Marsh River during the spring and in Sagadahoc Bay 

 during the summer originated from the major spring 

 spawning in the South Atlantic Bight or the major 

 summer spawning in the Middle Atlantic Bight. Most 

 juvenile bluefish from the Marsh River originated 

 from a spring spawning during March-May (Fig. 3, 

 A and B). Conservative estimates of the time required 

 to swim from the northern portion of the spawning 

 ground in the South Atlantic Bight to the collection 

 site in the Marsh River during 1990 and 1991 would 

 equal 147 days (1350 km + 9.16 km/day) and 156 

 days (1350 km * 8.64 km/day), respectively. These 

 estimates of swimming time exceed the known ages 

 of juvenile bluefish derived from daily ring counts 

 (129 days, 1990; 137 days, 1991) even before addi- 

 tional time from physical and biological factors are 

 considered. These factors include 1) swimming into 

 the current from Cape Hatteras to Southwestern 

 Maine (Bumpus and Lauzier, 1965), 2) the possibil- 

 ity that swimming speed is less than twice the body 

 length, 3) decreased swimming speed at night (Olla 

 et al., 1985), and 4) feeding behavior which results 

 in nonlinear movement. 



Juvenile bluefish from Sagadahoc Bay originated 

 from a summer spawning which occurred mainly 

 during June (Fig. 3C). A conservative estimate of the 

 time required to swim from the northern portion of 

 the spawning ground in the Middle Atlantic Bight to 

 the collection site in Sagadahoc Bay during 1990 

 would equal 107 days (425 km + 3.97 km/day). This 

 estimate greatly exceeds the known age of the fish 

 (69 days). The estimate of swimming time is in- 

 creased further when physical and biological factors 

 that impede swimming are considered. 



We believe that juvenile bluefish collected from the 

 Marsh River and Sagadahoc Bay may be derived from 

 unknown spawning areas closer to Maine. Lyman 

 ( 1974) stated that "some of their spawning grounds 

 are known but many remain to be discovered along 

 much of the northeast coast." It is also possible that 

 both major spawning areas known to exist in the 

 South and Middle Atlantic Bights, have extended 

 northward. Another possibility is that "larval trans- 

 port mechanisms and spawning periodicities for blue- 

 fish are considerably more complex than previously 

 believed" (Powles, 1981). 



The relationship between the log 10 of the fork 

 length and the number of daily rings for 1990 and 

 1991 data is shown in Figure 4. The range of fish 



