434 



SCIENCE. 



[Vol. VI., No. 145. 



based upon the fluctuations of catch in a single 

 river are necessarily fallacious, since such fluctua- 

 tions are due to local causes. So far as the shad 

 is concerned, all the rivers draining into the 

 Atlantic between Cape Cod and the capes of the 

 Chesapeake, and the submerged continental bor- 

 ders lying between the coast line and the Gulf 

 Stream, constitute a single zoological province, 

 within the limits of which the migrations of the 

 shad are confined. 



In February and March, when their migrations 

 into continental waters begin, the direction of their 

 movements is largely determined by temperature 

 conditions existing in the area in which they are. 

 The principal migration may be into the Chesa- 

 peake, or it may be up the coast into the Delaware, 

 the Hudson, and the Connecticut ; but in either 

 case the aggregate catch will furnish a just meas- 

 ure of increase or decrease. A comparison of the 

 statistics of the fisheries for 1880 and 1885 (see 

 table I.) shows a gain of nearly eight per cent in 

 the aggregate catch. The significance of this, as 

 showing the value and necessity of artificial propa- 

 gation, will be better appreciated by considering 

 the adverse conditions under wliich it has been 

 accomplished : — 



1. Access to suitable spawning grounds in fresh 

 water is a physiological necessity. 



2. Access in sufficient numbers to compensate 

 by natural reproduction, waste by casualty or cap- 

 ture, is necessary to prevent the eventual destruc- 

 tion of our shad fisheries if we rely upon natural 

 rei)roduction solely. 



3. Existing adverse conditions limit natui'al re- 

 production, so that we cannot depend upon it to 

 keep up supply. 



(a) Dams in our rivers have curtailed the spawn- 

 ing areas to less than half of what they formerly 

 w^ere. 



(b) The spawning grounds still accessible have 

 been destroyed by the pollution of the waters, 

 which are thus rendered unfit to sustaia the deli- 

 cate embryo shad. 



(c) The change in the location of the fishing 

 grounds, and the increasing proportion of shad 

 taken year by year outside of the mouths of the 

 rivers, or in the rivers before they have reached 

 spawning groimds, has so reduced natural repro- 

 duction as to render it an insignificant factor in 

 keeping up supply. 



Under such conditions, the spawning area being 

 limited, and the shad excluded from fresh water, 

 without artificial propagation, the shad must soon 

 be exterminated, or there must at least be such 

 reduction as to render the fisheries unprofitable. 

 Such a crisis was fast approaching in 1879, when 

 the fish commission began the work of shad propa- 



gation. The work of artificial propagation has not 

 only held the balance even, but resulted in a slight 

 increase. 



Colonel McDonald deprecated the methods em- 

 ployed in shad fishing, especially the use of pound 

 nets. In the Connecticut River, where pound 

 nets are used, the greater part of the catch is taken 

 in salt water. In the Hudson, since the laws of 

 New York do not permit fishing with pound nets, 

 the river is not obstructed to the same extent as 

 the Connecticut. In the Delaware, where an 

 increase is shown, there are no pound nets. In 

 the Chesapeake and its tributaries, with a decrease 

 of 21 per cent, 713,000 of the shad caught this 

 year, or more than one-half of the whole catch, 

 were caught in the salt water of the bay. The 

 pound nets begin at the capes, and extend to the 

 mouth of the Potomac. Prior to 1871 the shad 

 were taken entirely in fresh water, but now over 

 one-half are caught in salt water. In the Potomac 

 River nearly one-half of the catch is made 

 in water where the fish cannot spawn. In the 

 Rappahannock one-half the catch is in brackish 

 water. In the York River the catch is practically 

 below Gloucester Point. In the James River there 

 are no pound nets, and in that river is an increase 

 in the catch. While the fisheries in the Chesapeake 

 Bay and its tributaries, as a whole, have fallen off 

 21 per cent, the decrease in the catch in certain 

 rivers is much greater. The catch in the Susque- 

 hanna m 1880 was 614,000, against 212,000 in 

 1885 ; and in the Potomac, 552,857 in 1880, against 

 157,697 in 1885. The reason of this is obvious. In 

 1871 there were no pound nets in Chesapeake Bay, 

 and no shad were taken until they entered fresh 

 water. Gilling was not prosecuted so low down 

 the river as now. In 1880 there were in Chesa- 

 peake Bay 180 pound nets set in the track fol- 

 lowed by the shad along the western shore, and 

 through these the shad had to run a gauntlet up 

 to the mouths of the rivers. Now there are 1,000 

 pound nets, occupying the western shores of the 

 bay, and excluding the fish from the fresh water. 

 The effect of the salt-water fishery is to diminish 

 natural reproduction, and to invoke artificial propa- 

 gation as a necessary aid to the fisheries. If all 

 shad were excluded from our rivers for three or 

 four years, without artificial propagation, the spe- 

 cies would be exterminated. Taking aU the facts 

 into consideration, and the inadequacy of natural 

 reproduction to supply the annual loss, we must 

 credit artificial reproduction not only with having 

 maintained the fisheries where they were, but with 

 an increase which repays ten times the cost of the 

 work of shad propagation, as carried on by the 

 U. S. fish commission and those of the several 

 states. 



