EEPEODUCTION OF THE SHAD. 605 



has been already said in regard to the influences of temperature in determining the movements of 

 these fishes. 



Causes infltjencikg- the rate of motement vf eiters. — The rate and duration of the 

 movement of Shad in our rivers are influenced by various causes. If, in consequence of warm 

 rains at the river's source, the temperature of the water becomes suitable to the Shad at an earlier 

 date than usual, then their np-ward movement takes place very rapidly, and, we may say, tumult- 

 uously, the great schools of fish crowding in and moving up all at once, so as to produce what is 

 termed a " glut." If, however, the temperature of the river rises by insensible degrees with the 

 advance of the season, then the upward movement begins when the water temperature of the river 

 has passed above that of the sea, and takes place gradually, the rate of movement in such cases 

 being slow and the period prolonged. Again, when the Shad have entered the rivers, the temper- 

 ature conditions being such as to determine a rapid ujiward movement, yet should the fish en- 

 counter floods and consequent muddy waters, their upward movement is arrested, the schools back 

 down before the flood, and if this condition be prolonged, may be driven entirely out of the river. 

 In short, fluctuations in the river temperature have corresponding iufluences upon the shad move- 

 meuts; any sudden change, whether to a higher or lower temperature, ai)i)arently arresting their 

 upward course for a time, and sometimes even determining a retrograde movement. 



Many of the anomalies which perplex fishermen in the course of their work may be explained 

 by the varying movements of the fish, as controlled by the water temperature in the rivers. We 

 find, for example, that while at a particular seine-shore, during one season, a very large catch 

 is made, yet in the following season, although the general run of. fish in the river has not dimin- 

 ished, the fishery in the same locality may prove a failure. If we suppose a seine to sweep the 

 flats at the month of such a stream as the Occoquan Creek,' and if we further suppose that the 

 river waters in the channel are colder than, or as cold as, the waters of the Chesapeake Bay, the 

 Shad in their movement up the river would avoid the main current, and would slowly work their 

 way up along the shores and over the flats, where the temperature of the waters will be found to 

 be, under such circumstances, several degrees warmer than in the channel. Such a season would 

 be profitable to a seine sweeping the flats. Again, if the waters in the main channel of the river 

 were of suitable temperature, then the tipward movement of the Shad would take place in the 

 channel and not along the flats. Under such circumstances a "channel seine," e. g., that of the 

 "White House," would make a very large catch, whilst a seine hauled over the flats, as on the 

 Pamunkey shore, would probably find very indifferent fishing. 



Eeprodtjction. — The age at which the Shad reaches maturity and becomes capable of repro- 

 ducing is not definitely determined; it is generally held by fish-culturists, however, that the female 

 Shad attains this condition when three or four years old. The period of maturity for the male, if 

 the relative size of the two sexes be taken as an indication, is much earlier than for the female. 

 Males, or " Buck Shad," weighing less than one and a half pounds (numbers of which always accom- 

 pany the schools of larger fish), are found to be milters, and at the shad-hatching stations — 

 especially during the earlier part of the season — the spawn-takers are frequently compelled to have 

 recourse to these fish in order to get the milt necessary for the fertilization of the eggs. These fish 

 cannot be more than two years of age. It appears that the first part of the run of fish up the rivers 

 consists almost entirely of males, which precede the females by several days. The records of the 

 fishing shores agree with this statement, their main catch in the earlier part of the season being 

 composed of "bucks," with a very sparing intermixture of "roe Shad," which latter, in their turn, 



'A tributary of the Potomac Eiver. 



