476 U. S. BUEEAU OP FISHERIES 



DlFFICULTIEa ENCOUNTERED IN COLLECTING EGGS 



A peculiar characteristic of the shad is that fish in prime spawning 

 condition are rarely taken by any form of fishing appliance except 

 between the hours of 4 and 10 o'clock p. m. Eggs in fish taken dur- 

 ing the morning hours seldom are sufficiently advanced to respond 

 to artificial treatment, and fish taken after 10 p. m. are usually 

 spent or partially so. 



As a riile, the best eggs are secured from the gill nets. Eggs from 

 fish taken in the large seines usually are of an inferior quality, but 

 those from the smaller seins, which are landed very soon after the 

 fish have been surrounded, are of a better grade. The eggs from 

 fish held in pound nets for several hours are valueless for artificial 

 propagation, since shad die very soon after captm'e and the eggs 

 rarely are susceptible of fertilization longer than 20 minutes after 

 the fish have been taken from the water. This peculiaiity is, per- 

 haps, one of the most deterrent factors against large egg collections. 



Gill nets are most effective at night and are customarily lifted dur- 

 ing the last stages of the ebb tide and the beginning of the flood. 

 Therefore, while other conditions may be favorable, but few eggs are 

 obtained unless the proper stage of the tide coincides with the 

 spawning hours of the fish, since at other times they are not in good 

 condition for stripping. 



A scarcity of male fish toward the end of the season often cuts 

 short operations when eggs are plentiful. Unsuccessful attempts 

 have been made to capture the males at such times by using gill nets 

 having a mesh smaller than that in the nets used by the market 

 fishermen. Attempts have been made, also, to pen the adults, but 

 without success, as the fish become diseased and their eggs spoil 

 within them. 



CLIMATIC CONDITIONS AND EGG COLLECTIONS 



During their migration up the rivers to the spawning grounds 

 shad are very responsive to climatic conditions. During a very 

 warm season the fish attain spawning condition earlier than under 

 normal conditions, while an unusually cold season will have the 

 opposite effect. A water temperature of 80° has been known to 

 result fatally to shad eggs, not only to those under incubation but 

 also to the eggs in the parent fish. The same eft'cct will be produced 

 by an abnormally low water temperature or sudden fluctuation in 

 either direction. 



Early in March the mean water temperature of the Potomac 

 Iliver at Bryans Point, Md., is normally between 36° and 40°; by 

 the middle of April, when the spawning season usually opens, it is 

 between 52° and 58°; and by the close of the spawning period, at 

 the end of May, the average is from 65° to 70°. Freshets, unusual 

 turbidity of water, and the direction and velocity of the wind all are 

 influential factors in the movements of shad. 



STRIPPING AND FERTILIZING THE EGGS 



In stripping the eggs tlie sliad is lifted with the right hnnd and 

 jaught above the tail with the left. All shmc and loose scales are 

 removed by going over the fish two or three times in quick succession 



