SHAD FISHERIES OF THE ATLANTIC COAST. 109 



in the Sacramento River it was supposed that they would return only 

 to that stream, but they have since appeared in many of the Pacific 

 coast waters in which they had not been indigenous and had never 

 been planted. 



Those who believe that shad return to the identical river in which 

 they were spawned refer to the numerous instances in which the fish- 

 eries of a certain river have decreased after the shad have been 

 excluded, by means of dams, from the spawning areas in that stream. 

 But those decreases appear to be due rather to the general depletion of 

 shad in that coastal area. For instance, the Merriinac Eiver was 

 obstructed in 1848 by a dam at Lawrence, 25 miles from the sea, yet shad 

 were caught in considerable abundance below that dam for a period 

 of thirty years thereafter, and the decrease in the Merrimac appears 

 to be merely an incident of the decrease on the New England coast. 

 This decrease is apparent in Casco Bay, where neither obstructions nor 

 spawning-grounds have ever existed. Comparatively few shad ascend 

 the Savannah or the Pee Dee as far as the spawning-grounds, yet the 

 fisheries of those streams appear to be holding their own among the 

 rivers of the South Atlantic States. 



It is well known that in their passage through the coastal waters 

 shad pursue certain well-defined paths, which, however, may be varied 

 by unusual conditions of temperature or currents. Thus, in passing up 

 the lower end of Chesapeake Bay shad usually crowd the western shore, 

 and are caught in immense numbers in the pound nets set there, while 

 the nets on the opposite shore take very few, this being due to their 

 following the thread of fresh water entering from the western side of 

 the bay. Yet during certain seasons, when quantities of cold water are 

 flowing down the Virginia rivers, or during the prevalence of northwest 

 winds, shad are caught in considerable abundance on the eastern shore 

 of Virginia and those nets on the western shore take comparatively 

 few. In entering Connecticut River, shad appear to follow the shore 

 west of the mouth of that stream, where they are caught in consider- 

 able numbers for a distance of 10 or 15 miles, yet they are rarely caught 

 on the shore immediately east of the river. In this instance they are 

 attracted by fresh water flowing from the Connecticut, which appears 

 to pursue a southwesterly course immediately on leaving that river. 



After entering the estuaries the rate and course of the shad move- 

 ment up the rivers are influenced by various causes, which are thus 

 described by the late Commissioner McDonald : 



If, in consequence of warm rains at the river source, the temperature of the water 

 becomes suitable to the shad at an earlier date than usual, then their upward move- 

 ment takes place very rapidly, and, we may say, tumultuously, the great schools of 

 fish crowding in aud moving up all at once, so as to produce what is termed a "glut." 

 If, however, the temperature of the water rises by insensible degrees with the 

 advance of the season, then the upward movement begins when the water temper- 

 ature of the river has passed above that of the sea, and takes place gradually, the 

 rate of movement iu such cases being slow and the period prolonged. Again, when 

 the shad have entered the rivers, the temperature conditions being such as to deier- 



