BERRIEN: EGGS AND LARVAE OF SCOMBER 



where they were taken suggests that their dis- 

 tribution extended beyond the continental shelf. 



Scomber j'aponicus, Larva Distributions 



Larval S.japonicus were caught on five cruises, 

 during January, February, April, May, and July. 

 They were most abundant during the same two 

 cruises on which eggs were taken (January- 

 February 1968 and May 1967). During January- 

 February 1968, larvae were caught from off New 

 River to off Palm Beach (Figure 12). During May 

 1967, larvae were found from off New River to 

 Ponce de Leon Inlet, Fla. (Figure 13). In addition 

 to those plotted, there were single occurrences of 

 S.japonicus larvae on three other crusies during: 

 April 1966, off Currituck Beach; May 1966, off 

 Cape Hatteras, N.C.; and July 1967, off St. Lucie 

 Inlet. 



Larvae were found slightly farther inshore than 

 were the eggs, in waters as shallow as 25 m, but 

 were generally over the outer half of the continen- 

 tal shelf. Larvae apparently occurred beyond shelf 

 waters, for they were caught at the edge of the 

 shelf on almost two-thirds of all the transects on 

 which they were taken. 



Scomber Japonicus larvae taken during the 

 January-February 1968 cruise ranged from 2.5 to 

 11.5 mm long. The modal length, 4.0 to 4.9 mm, for 

 this cruise was made up of larvae from both areas 

 of concentration, on the Brunswick, Ga., and Cape 

 Canaveral transects. Larvae caught during May 

 1967 ranged from 2.8 to 20.5 mm long. There were 

 two modal length intervals during this cruise; lar- 

 vae composing the first, at 4.0 to 5.9 mm, were 

 largely from the Cape Lookout transect while 

 those of the second, at 8.0 to 8.9 mm, were from 

 both the Cape Romaine, N.C., and Brunswick 

 transects. No latitudinal size progression was ob- 

 served in the data, as seen in S. scombrus data 

 from June. Spawning appears to occur simulta- 

 neously from North Carolina to Florida, and to 

 extend over at least 7 mo (January to July). 



Scomber japonicus. Temperature vs. 

 Egg and Larva Occurrences 



During January-February the surface 

 isotherms roughly paralleled the shoreline south 



I of Cape Hatteras, with higher temperatures found 

 offshore (Figure 10). Therefore, the generally 

 offshore distributions of S.japonicus eggs and lar- 



I vae mentioned previously were also correlated 



with the upper temperatures sampled on this 

 cruise. Larvae were found over a greater range of 

 surface temperature (18.5° to 24.7°C) Than were 

 the eggs (20.4° to 23.2°C) in January-February. 



Surface temperature conditions during May 

 were different from those of the January-February 

 cruise. During May many surface isotherms ex- 

 tended across the shelf (Figure 11), especially 

 within the temperature range at which most eggs 

 and larvae of this species were found (approxi- 

 mately 21° to 24°C). However, the distributions of 

 eggs and larvae were similar on this cruise to 

 those from the January-February cruise, i.e., re- 

 stricted to the outer half of the shelf waters. Eggs 

 were found within approximately the same sur- 

 face temperature range as larvae during this 

 cruise, 21.3° to 25.4°C for eggs and 21.3° to 24.2°C 

 for larvae. Including all occurrences of S. 

 japonicus eggs and larvae, on five cruises, the 

 ranges of surface temperatures encountered were 

 20.4° to 25.4°C for eggs and 16.0° to 29.4°C for 

 larvae. 



DISCUSSION 



Scomber scombrus spawns from Cape Hatteras 

 to the Gulf of St. Lawrence. Spawning progresses 

 northeastward along the coast as the adults mi- 

 grate during spring and early summer. Within the 

 survey area, most spawning takes place over the 

 shoreward half of the continental shelf, with small 

 numbers of eggs occurring out to and possibly 

 beyond, the edge of the continental shelf. Surface 

 temperatures associated with spawning (egg oc- 

 currences) range from about 7° to 16°C. In com- 

 parison, the majority of S.japonicus spawn south 

 of Cape Hatteras; the southern extent of spawning 

 is unknown, but it extends at least as far south as 

 Key Biscayne, Fla. Spawning by this species may 

 occur north of Cape Hatteras but farther offshore 

 than sampling was conducted, possibly in Slope 

 Water or the shoreward edge of the Gulf Stream. 

 The spawning season extends at least from mid- 

 winter to early summer south of Cape Hatteras. 

 Unlike S. scombrus, if S . japonicus undertakes a 

 spawning migration it has not been described. 

 Spawning occurs predominantly over the outer 

 half of the continental shelf, and probably beyond. 

 Surface temperatures associated with S. 

 japonicus spawning in the western North Atlantic 

 Ocean vary from about 20° to 25°C. 



Scomber japonicus eggs were associated with 

 generally higher temperatures (20° to 25°C) 



111 



