STUDIES ON THE STRIPED BASS OF THE ATLANTIC COAST 19 



In 1938 the first spawning striped bass were taken at Weldon on April 11, and by 

 May 10 spawning was apparently completed and the fish had left this locality. This 

 was an unusually early and short spawning season, probably due to the abnormally 

 high temperatures during this time. From April 29 to May 11 the water temperature 

 averaged well over 70° F. (21.11° C.) and at one time reached 77° F. (25.0° C). 

 During the spawning season it is a quite common occurrence to see the so-called 

 "rock-fights" described by Worth (1903), and well known to local fishermen on the 

 Roanoke River. These consist of a great number of small males, 1-3 pounds in 

 weight, and apparently only a single female, appearing on the surface and causing a 

 tremendous commotion by splashing about and creating general confusion. Tbe 

 activity is said to be so great that the fish often injure one another quite seriously, 

 and fishermen who catch striped bass when they are "in fight" attest to this fact and 

 to the number of small males, 10-50 as a rule, that take part in such a display with a 

 single female of from 4-50 pounds. Whether or not this is actually part of the spawn- 

 ing act or a form of courtship does not seem to be definitely established, but general 

 opinion favors the former view. There can be little doubt that the spawning fish at 

 Weldon are composed mainly of males, the females probably never making up as much 

 as 10 percent of the population. In May 1938 the examination of 127 individuals 

 taken at Weldon showed but 6 of them to be females, and much the same sex ratio 

 was found to obtain farther down the Roanoke River at Jamesville, N. C, at the 

 same time. 



There is no reason to doubt the accuracy of Worth's estimates of the number of 

 eggs produced by a single female striped bass. Records kept at the hatchery at 

 Weldon during 1928, 1929, 1931, 1932, 1937, and 1938, show that the number of 

 eggs per female varied from 11,000 to 1,215,000 in a total of 111 individuals examined 

 in this time. The majority of these fish yielded from 100,000 to 700,000 eggs each. 

 Unfortunately the weights of the individual fish on which these counts were made 

 were not taken, but a single female weighing 4% pounds, taken at Weldon on May 4, 

 1938, produced 265,000 eggs. 



The eggs of the striped bass average about 1.10-1.35 mm. in diameter when they 

 become fully ripe, and at the time that they are extruded into the water. During 

 the first hour after fertilization the vitelline membrane expands tremendously, thus 

 creating a large perivitelline space. Measurements on a series of 50 eggs that were 

 preserved 1 hour after fertilization in a solution of 7 percent formaldehyde gave an 

 average measurement of 3.63 mm. in diameter, the extremes being 3.24 and 3.95 

 mm. Eggs similarly preserved at longer time-intervals after fertilization showed the 

 same general measurements. So far as one can judge from preserved specimens, the 

 description given by Bigelow and Welsh (loc. cit.) of the eggs as being semibuoyant 

 fits perfectly. These eggs are undoubtedly swept far downstream by the strong 

 current, and the protection against injury by jarring afforded by the large perivitelline 

 space is probably of no small consequence in the survival of the developing embryos. 

 The speed of development and the time to hatching is of course dependent on tem- 

 perature. At 71°-72° F. (21.7°-22.2° C.) hatching occurs in about 30 hours, while 

 at 58°-60° F. (14.4°-15.6° C.) hatching normally takes place in about 70-74 hours. 

 In view of the fast current in the Roanoke River, and the rate at which the developing 

 eggs are carried downstream, it is reasonable to assume that hatching probably does 

 not take place until they are close to the mouth of the river or even in Albemarle 

 Sound. Figure 12 shows the different stages of development of striped bass eggs and 

 larvae that were reared in the hatchery at Weldon, N. C. These eggs were fertilized 

 artificially and held at a temperature of 70°- 72° F. (21.1°-22.2° C). The photo- 

 graphs of the eggs were taken from above looking down. A side, view would in reality 

 show that the yolk, with the developing embryo and oil globule, lies at the lower 

 pole of the whole egg as it floats normally in the water. The single large oil globule 

 which is imbedded in the surface of the yolk always lies uppermost, and the blastodisc 

 appears on the side of the yolk in an area that is approximately at a 90° angle with 

 the oil globule— not just opposite the oil globule on the lower pole as Wilson (1891) 

 has shown for the sea bass ("Serranus atrarius" — Wilson, loc. cit., now called Cen- 

 tropistes striatus). Hatchine occurred in 30 hours in the lot under observation, and 

 it will be seen in figure 12 (F) that 6% clays later the yolk sac was almost completely 

 absorbed. 



