FISHERY BULLETIN: VOL. 80, NO. 2 



Bay, 53 in the lower tidal river, and 9 in the 

 upper tidal river. A total of 64 specimens were 

 captured in commercially fished gill nets, most 

 as a bycatch of operations for American shad, 

 and weakfish, Cynoscion regalis. The remaining 

 66 specimens were taken incidental to various 

 fishery and ecological investigations; 23 by 4.9 m 

 bottom trawl, 17 by 9.1 m bottom trawl, 12 by 

 experimental gill net, 9 at industrial cooling 

 water intakes, 1 by 4.9 m surface trawl, 1 by hook 

 and line, and 3 were dead on the water's surface 

 or on shore. 



In Delaware Bay Atlantic sturgeon were taken 

 from March through November (Fig. 2). Catch 

 was greatest during March through May 

 (14-23/mo), low during July through August 

 (1/mo), and increased somewhat during Septem- 

 ber through November (2 or 3). The spring peak 

 was composed largely of specimens captured in 

 1979 and 1980 by the cooperating commercial 

 gill netters who logged incidental Atlantic 

 sturgeon captures while fishing shallow waters 

 off of Kitts Hummock (river km 41) and Port 

 Mahon (river km 47), Del., in 1979 and Pickering 

 Beach (river km 44), Del., in 1980. Their records 

 reflect 27 specimens taken during 20 April-14 

 May 1979 and 8 during 24 March-22 April 1980. 

 Additionally, all 18 Atlantic sturgeon reported 

 from Delaware Bay by Dovel (1979) were taken 

 during March-May (see Table 1). Although this 

 abundance pattern may be biased by the greater 

 fishing effort expended during spring relative to 

 other seasons, essentially all other commercial 

 gill netters interviewed reported the highest 

 frequency of incidental sturgeon capture during 

 spring. Most Atlantic sturgeon taken in the gill 

 net fishery are apparently below marketable size 

 and are released. Records indicate that survival 

 in gill nets was very high if the nets were tended 

 daily. 



In the lower tidal river Atlantic sturgeon were 

 taken from February through September and in 

 December (Fig. 2); most during July (16), al- 

 though moderate numbers (6-10) were taken 

 from April through August. Eleven specimens 

 were taken in late July and early August 1968, by 

 two part-time commercial gill netters purposely 

 fishing for Atlantic sturgeon. These men fished, 

 typically for a 2-wk period in summer, between 

 Delaware City (river km 98) and Liston Point 

 (river km 77), Del., during the late 1940's through 

 the early 1970's. They employed essentially 

 traditional methods, as described by Cobb 

 (1900), and drifted 9 X 572 m, 28 cm cotton mesh 



10 





 20 



10 



K 

 Ul 

 CD 



I 



z 



25 



15 



UPPER TIDAL 

 RIVER (n = 7) 



I 1 



LOWER TIDAL 

 RIVER (n=53) 



-1 1 1 1 1 I r- 



DELAWARE BAY 

 (n = 63) 



J F M ' A ' M 



MONTHS 



Figure 2.— Number of Atlantic sturgeon captured monthly in 

 three regions of the Delaware River estuary, 1958-80. 



gill nets along the bottom from about 1 h before 

 to about 1 h after low tide (Beck 2 ). These were, to 

 the best of our knowledge, the last successful 

 commercial efforts directed specifically at 

 Atlantic sturgeon. Although the above men- 

 tioned 11 specimens are the only quantitative 

 accounting of their catch available, anecdotal 

 accounts indicate considerable success with as 

 many as 191 specimens taken in a 2-wk period 

 (Beck 1973). 



In the upper tidal river, Atlantic sturgeon 

 were captured in June (1), August (4), and 

 September (2) (Fig. 2). Only one specimen was 

 taken in the Wilmington, Del., to Philadelphia, 

 Pa. (river km 114-170), reach. In this region 

 mean dissolved oxygen concentrations approach 

 zero during summer and are typically below 5 

 ppm during May through October (Freiders- 

 dorff et al. 1978). This fish was taken sometime 

 during October-December 1975, when oxygen 

 concentration was considerably higher. 



Available data showed that Atlantic sturgeon 

 occurred over a wide range of water temper- 

 ature (0.5°-28.1°C) and salinity (0.0-29.0 V..). The 

 varying availability of temperature and salinity 

 data by region, however, precludes further dis- 

 cussion. Values were available for 62% of the 

 specimens captured in the lower tidal river but 



-Robert A. Beck, Department of Natural Resources and 

 Environmental Control Divisionof Fish and Wildlife, P.O. Box 

 1401, Dover, DF 19901, pers. commun. December 1978. 



340 



