110 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



iniue a rapid upward movement, yet should the fish encounter Hoods and consequent 

 muddy waters, their upward movement is arrested, the schools back down before 

 the Hood, and, if this condition is prolonged, may be driven entirely out of the 

 river. In short, fluctuations in the river temperature have corresponding inilueuces 

 upon the shad movements; any sudden change, whether to a higher or lower tem- 

 perature, apparently arrests their upward course for a time, and sometimes even 

 determines a retrograde movement. Many of the anomalies which perplex fisher- 

 men 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 the fishery in the same locality may prove a failure, although 

 the general run of fish in the river has not diminished. If we suppose a seine to 

 sweep the flats at the mouth of such a stream as the Occoquan Creek (a tributary 

 of the Potomac River), 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 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 upward movement of the shad would take place in the channel and not 

 along the flats. Under such circumstances a channel seine would make a very large 

 catch, while a seine hauled over the flats would probably find very indifferent 

 fishing. 



In their migrations up the rivers sbad ascend the stream until the 

 volume of the water forming the channel of the river becomes quite 

 inconsiderable, or, as is more frequently the case, until their move- 

 ments are arrested by impassable falls, dams, or other obstructions. 

 However, a discussion of the limit of their range in the rivers is 

 reserved for a special chapter. 



RANGE OF SHAD IN THE RIVERS. 



In considering the limit of shad range in the rivers the principal 

 points to be kept in view are the size of the stream, uniformity of slope, 

 and its freedom from dams and other obstructions. No river on the 

 Atlantic seaboard appears too long for shad to ascend to its head- 

 waters, provided they meet with nothing to bar their progress. At 

 present they ascend the St. Johns, in Florida, a distance approximating 

 375 miles; the Altamaha 300 miles; the Santee 272 miles; the Neuse 

 270 miles, and the Delaware River a distance of 240 miles from the 

 sea. However, these distances do not equal the extreme ranges in the 

 early part of the present century. Then shad ascended the Savannah 

 to Tallulah Falls, a distance of 384 miles, instead of 209 miles as at 

 present. They ran up the Pee Dee to Wilkesboro, a range of 451 

 miles, whereas the present limit on that river is Grassy Island, 242 

 miles from the sea, and only one shad was reported from that point in 

 1896. On dames River the former run was 350 miles in length, while 

 the preseut limit is at Bosher's Dam, 120 miles. Bat the greatest 

 decrease exists in Susquehanna River, in which shad formerly ascended 

 to Binghamtou, 318 miles from the mouth and 513 miles by water- 

 course from the sea, whereas at present they do not appear to pass 

 beyond Clark's Ferry, 84 miles from the mouth of the river. 



