26 U. S. BUREAU OF FISHERIES 
inches, measured to the fork of the tail (approximately 17% inches 
over all), would lead to greater yields and larger profits from each 
brood, whether large or small. The number of fish reaching spawning 
size would also be increased. 
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Shad.—In marked contrast to the striped bass, the principal prob- 
lem in shad conservation is maintenance of an adequate spawning 
reserve. Although pollution and obstruction of rivers have doubtless 
contributed to failure of reproduction, the decline in yield of more 
than 80 percent during the present century has not been limited to 
polluted or obstructed streams. On the contrary, some almost un- 
polluted rivers, such as the Edisto River in South Carolina, have been 
severely depleted and a fine recovery has been observed in the pol- 
luted Hudson River. This recovery is attributed to regulations 
limiting fishing to 4 nights a week and closing spawning areas to 
fishing. 
In order to extend to other localities the benefits of the experience 
in the Hudson it is necessary to know the approximate spawning 
escapement there and to devise means of matching it substantially 
elsewhere. 
Studies in 1988 indicate that the fishery removed somewhat more 
than 50 percent of the run. Of 196 shad tagged in Sandy Hook Bay 
in April, 53 percent were taken during the season in the river. Since 
tagging experiments usually underestimate fishing intensity it is 
probable that the fishery removed somewhat more than the indicated 
percentage. 
As a check on the estimate of fishing mortality by tagging experi- 
ments, scales were examined for spawning marks in 1938 to estimate 
the percentage of that year’s catch contributed by fish which had 
escaped the fishery in 1987. On the basis of the reported catch in 
1937, and assuming a fishing mortality of 60 percent, approximately 
1,667,000 fish should have entered the river in 1937. Of these, about 
1,000,000 were caught and 667,000 escaped. Assuming 10 percent 
mortality among these after they left the river, about 600,000 would 
be expected to return in 1938. From preliminary estimates of the 
catch in 1938 it appears that the total run to the river was about 
1,250,000 fish. Of these about 600,000, or 48 percent, would be “re- 
peaters” or fish which had escaped the fishery and which had spawned 
in 1937. Forty-six percent of the scales collected in 1938 bore spawn- 
ing marks indicating that they had spawned in 1987, certainly in 
very good agreement with the expectation from the above estimate. 
Similar collections of scales have been made in other rivers where 
depletion is greater. As might be expected, the percentage of scales 
having spawning marks is much lower, but, until records of the catch 
for 1937 and 1938 are available, the percentage escapement in 1937 
cannot be estimated. : 
Because of the importance of reproduction in shad conservation a 
careful ecological study of the early life history is being made by 
John C. Pearson and Louella Cable. In 1938 intensive work was done 
m the Edisto River in South Carolina and it is expected that these 
studies will be extended to other rivers in 1939. In these studies 
especial attention is being paid to estimating rates of mortality at 
various stages in the early hfe history, at various levels of abundance 
of young, and under various conditions of temperature and volume 
