FISHERY BULLETIN: VOL. 74, NO. 2 



den 1974). The catches in these two periods are so 

 similar that it would appear that the Lackawax- 

 en Dam had little effect on abundance. The chief 

 spawning grounds may have been located even 

 further downstream than Lackawaxen, however, 

 because Abbott (1868) stated that shad were sel- 

 dom plentiful upstream from Delaware Water 

 Gap, and this is supported by Smiley 's (1884) 

 statement that no shad were seen farther up- 

 stream than Milford for 25 yr prior to 1872. Shad 

 were abundant at that time (Slack 1874). 



Spawning grounds could have extended 

 downstream to about Marcus Hook, because shad 

 spawn in fresh water (Prince 1907; Leach 1925; 

 Hildebrand and Schroeder 1928; Massmann 

 1952). Consideration of preferred spawning and 

 nursery habitat and Delaware River morphology 

 suggests that tidal water was historically impor- 

 tant: the existence of an extensive tidal nursery 

 (and spawning area) immediately downstream 

 from extensive excellent spawning grounds was 

 probably important to the former abundance of 

 Delaware River shad (Chittenden 1973b). How- 

 ever, the contemporary literature conflicts on the 

 importance of the tidal Delaware (Pennsylvania 

 1897; discussion session after Meehan 1907; New 

 Jersey 1916). 



The potential importance of the tidal Delaware 

 can be judged by comparison with other rivers. 

 Hudson River runs are entirely produced in tidal 

 water, because a dam constructed in 1840 at Troy, 

 N.Y. (Cheney 1896), blocks passage of shad to 

 nontidal water. Annual Hudson River landings 

 were 2-4 million pounds from 1936 to 1949 and 

 catches of about 5 million pounds have been re- 

 ported (Talbot 1954). Migration of shad in the 

 Potomac River is blocked by Great Falls, 16 km 

 upstream from tidal water, so that most fish are 

 probably from tidal spawning. Spawning grounds 

 in several Virginia rivers are in tidal waters 

 (Massmann 1952). Therefore, it appears that tidal 

 spawning was once very important in the Dela- 

 ware River, in agreement with Walford [a 1951 

 memorandum cited by Mansueti and Kolb (1953)] 

 who stated that the principal spawning area once 

 was probably a short distance above Gloucester, 

 N.J. (km 30). 



The area near Hancock apparently became an 

 increasingly important spawning area — but 

 eventually for reduced numbers of fish — as the 

 Delaware River shad runs declined. Many fish 

 again moved upstream into the East Branch after 

 installation of the Lackawaxen fishway in 1890 



(Bean 1892, 1903). Landings from 1904 to 1913, in 

 general, were only about 3-5 million pounds and 

 consistently have been much less than 0.5 million 

 pounds since 1920 (Sykes and Lehman 1957; 

 Chittenden 1974). In spite of this great decline, 

 many shad (240-350/seine haul) were captured at 

 Hancock until 1915 (Bishop 1936). Catches near 

 Hancock gradually declined after 1915, and a 

 shad fishing club captured only 60-75 fish annu- 

 ally after 1920 and less than 12 in some years 

 (Greeley 1936; Bishop 1936). 



Many tributaries, particularly in the tidal 

 area, may have been used for spawning and as 

 nurseries; but their historical importance is not 

 clear. Adults entered many tributaries near 

 Philadelphia (Meehan 1896; Stevenson 1899). 

 The Lehigh and Schuylkill rivers were once fa- 

 mous shad streams (Gay 1892; Meehan 1896), al- 

 though dams were constructed after 1820 and 

 prevented access to these streams. 



Recent Spawning and Nursery Areas 



With the probable exception of the most grossly 

 polluted tidal areas, recent spawning and nursery 

 areas have extended throughout fresh water of 

 the Delaware and into the East and West 

 branches. In general, nurseries must be at or 

 downstream of spawning grounds, because the 

 young begin to disperse downstream upon trans- 

 formation from the post-larval stage — if not 

 sooner (Chittenden 1969). 



The chief spawning grounds and nurseries now 

 extend no farther downstream than Belvidere. 

 Gonad condition, the presence of few adults after 

 mid-May, and the location of the chief nurseries, 

 especially during early July, indicate that very 

 little spawning occurs as far downstream as 

 Lambertville. The Delaware between Belvidere 

 and Philadelphia probably now serves as a nur- 

 sery primarily due to downstream dispersal of the 

 young. The importance of spawning grounds and 

 nurseries now increases proceeding upstream 

 from Belvidere towards Hancock. The most im- 

 portant spawning grounds and nurseries are lo- 

 cated from about Port Jervis to Hancock and ex- 

 tend into the lower East Branch. 



Tidal water near Philadelphia is no longer 

 suitable as a nursery and probably not for spawn- 

 ing. Although conditions vary slightly between 

 years, in general, the minimum daily dissolved 

 oxygen is at or near mg/liter from about mid- 

 May through early December in the 66-km 



348 



