STUDIES ON THE STRIPED BASS OF THE ATLANTIC COAST 21 



Such a disproportionate number of females to males is of course most unusual, 

 and it seems unlikely that this condition prevails among the total population of the 

 Atlantic coast. The examination of 29 small bass from Delaware Bay in November 

 1937 showed approximately 45 percent were males. A sample of 126 bass ranging 

 in size from 21 to 42% cm., from Albemarle Sound, N. C, in March and April 1938 

 was composed of 31.7 percent male fish. There is also evidence that the composition 

 of the spawning populations of striped bass is predominantly male (p. 19). A 

 theoretical explanation of the strikingly low percentage of males in northern waters 

 is included in the section under migrations (p. 44). 



In studies of the age at maturity, miscroscopic examination of the gonads pre- 

 sented the most plausible method of procedure in northern waters. The fact that 

 ripe 8 individuals were not available in Connecticut precluded the possibility of 

 studying the age groups making up a spawning population. Gonads from 109 female 

 striped bass ranging in size from 32 to 110 cm. were collected at various intervals 

 from April through November 1936 and 1937. Of these, 46 were fixed in Bouin's 

 fluid and slices from the anterior, middle, and posterior region of each one were cleared 

 in toluene. 9 These were sectioned, stained with Delafield's hematoxylin and eosin, 

 and mounted. Samples of up to 50 ova from each of the three regions of the gonads 

 from which slices were taken were then measured by means of an ocular micrometer. 

 It was soon found that samples from the anterior, middle, and posterior parts of each 

 ovaiy contained eggs of the same general sizes, and that there was no significant 

 difference between the ova of these regions, no matter at what stage of development the 

 gonads were. Thereafter only sections from the middle of each ovary were studied. 

 The remaining 63 ovaries from striped bass collected from April through November 

 1936 and 1937 were preserved in a solution of 10 percent commercial formalin and 

 water. Slices from the middle of each one of these gonads were then macerated 

 mechanically, until the eggs either floated free or could be easily teased from the 

 surrounding epithelium. Samples of up to 50 ova from each ovary were then meas- 

 ured under a dissecting microscope by means of an ocular micrometer. The measure- 

 ments on the eggs from 109 ovaries by these 2 methods gave comparable results 

 throughout. 



A study of the measurements of the eggs from striped bass of different sizes almost 

 immediately revealed that there were two easily distinguishable types of ovaries. 

 (See fig. 13.) The first type had eggs whose diameters consistently averaged 0.07 

 mm. There were occasionally eggs as large as 0.18 mm. in diameter, but more com- 

 monly the largest eggs measured 0.11 mm. The second type contained eggs of two 

 definite size categories; there were small eggs of the same size as all those that were 

 seen in the first type of ovary, averaging 0.07 mm. in diameter, and there were large 

 eggs averaging 0.216 mm. in diameter or greater, the extreme size that has been 

 encountered being 0.576 mm. It is a reasonable assumption, especially in view ol 

 Scoficld's (1931) work, that those ovaries containing only small eggs represent im- 

 mature fish, and that those ovaries having eggs of both small and large size come 

 from fish that are mature, in the sense that the large eggs are those that will be pro- 

 duced the following spawning season. A possible criticism of this assumption is that 

 part of the material examined might have been composed of ovaries from fish that 

 had just completed spawning, and that such ovaries might, therefore, contain only 

 eggs of the small size. On the basis of the distinction between mature and immature 

 individuals proposed above, these fish would then be considered immature, a conclu- 

 sion that would be entirely erroneous. There is no evidence, however, that ovaries 

 from fish that had completed spawning immediately before were included in the 

 material. It has already been pointed out that spawning individuals were not found 

 in the waters from which this material was collected, and it is most unlikely that 

 any freshly spawned bass were studied for the purpose of determining the age of ma- 

 turity. Moreover, by far the greater part of the collection of gonads of striped bass 

 of different sizes took place in the summer and fall, by which time spawning is known 

 to be long since past. Another possible criticism of this method of determining the 

 age at maturity of striped bass is that some of the material may have come from fish 

 that were not spawning the following year, for this species is not necessarily an annual 



8 The word "ripe" is used throughout to connote flowing milt or eggs. 



' Oil of wintergreen and other clearing agents were also used at first, but in general toluene gave the most satisfactory results. 



