CHAPTER 16 



near Monmouth Beach in early July to Atlantic City by 

 late July. 



In late June 1976, dissolved oxygen (DO.) concentra- 

 tions in bottom waters were almost depleted («1.() ml/1) 

 from the Bight Apex region off Asbury Park south to 

 Barnegat Inlet (fig. 16-1). By September, D.O. concen- 

 trations in the northern portion of this area were again 

 generally from 1 to 2 ml/1. During July and August the 

 region of low D.O. concentration (« 2.0 ml/1) appeared 

 to shift south, within a 6,200-km- area extending 10 to 120 

 km offshore between Barnegat Inlet and the Delaware- 

 Maryland boundary. Bottom waters in much of this area 

 (1,500 km") had no D.O. in September, and hydrogen 

 sulfide was observed at some locations. 



EFFECTS ON BIOTA 



Surf clams, ocean quahogs, finfishes, lobsters, and sea 

 scallops (in decreasing order of resource loss) were the 

 commercial species most affected. There were minor mor- 

 talities of demersal fishes, but the greatest economic ef- 

 fects on finfish commercial catch resulted from movement 

 of these organisms away from their normal geographic 

 locations. Thus, they were not readily available to the 

 commercial fishery. 



Estimated economic impacts of the mass mortalities 

 were considerable. Actual losses to fishing, processing, 

 and marketing industries were about $7.9 million during 

 1976, and estimated losses of the resource were about 

 $62.5 million (ch. 14). Until stocks are replenished 

 through recruitment, which may take 7 years or more for 

 surf clams, potential losses to the surf clam industry could 

 exceed $550 million. Immediate losses to the sport fishery 

 were estimated to be $3.7 million. However, recreational 

 fishing for summer flounder was excellent in New Jersey, 

 where this species was confined to the estuaries and im- 

 mediate coastal area by oxygen-depleted water offshore 

 (ch. 11, pt. 1). 



Surf clams off New Jersey were affected more than other 

 molluscan species. Their distribution coincided with the 

 oxygen-depleted bottom waters where they were sub- 

 jected to low D.O. levels and hydrogen sulfide poisoning 

 (ch. 11, pt. 1). More than 60 percent of the New Jersey 

 surf clam biomass was lost. Mortalities of up to 85 percent 

 were estimated for the most severely impacted area. Total 

 surf clam biomass loss from 1976 levels was estimated at 

 1.8 X lOM. 



Ocean quahogs and sea scallops off New Jersey had 

 considerably less losses than surf clams. About 6 percent 

 of the ocean quahog resource and 10 percent of the sea 

 scallop resource were lost. Both occur seaward of the area 

 most severely affected by low D.O. The reported (ch. 11, 



pt. 1) increase in 1976 sea scallop landings over 1975 is 

 attributed to greater interest in sea scallops, brought about 

 in part by their use as an alternative to the severely af- 

 fected surf clam resource. 



The 1976 mass mortalities in the New York Bight com- 

 monly were misnamed a fishkill, but few adult finfishes 

 were killed. The greatest effect on adult finfishes was to 

 disrupt normal migration routes and change locations of 

 occurrence (ch. 13). Few live or dead finfishes were taken 

 during trawling surveys in waters having extremely low 

 D.O. (<0.4 ml/1), and these waters were repopulated soon 

 after replenishment of oxygen. 



That finfishes avoided areas of low dissolved oxygen is 

 best documented by tagging surveys of bluefish (ch. 13). 

 Their northward migration inshore (schools of 0.5- to 1.4- 

 kg bluefish) and offshore (schools of 2.7- to 6.8-kg blue- 

 fish) occurred normally in 1976, but the midshelf migration 

 (schools of 1.4- to 5.4-kg bluefish), which should have 

 traversed the anoxic region, apparently did not occur. 

 Bluefish in this size class remained near the Delmarva 

 Peninsula, south of the area of low D.O. Also, the unu- 

 sually good fishing for summer flounder along the New 

 Jersey coast (noted previously) apparently resulted when 

 these fish avoided waters of low D.O. offshore. Perhaps 

 the most significant impact of oxygen depletion on finfish 

 populations (and the most difficult to document) was re- 

 duced spawning and mortalities of eggs and larvae in af- 

 fected areas. 



American lobster catches for northern New Jersey de- 

 clined in 1976 and are believed to be the result of oxygen- 

 depleted bottom waters. It is difficult to assess the relative 

 importance of lobster mortalities and disruption of their 

 annual offshore to inshore summer migration. Lethargic 

 and dead lobsters were found near wreck sites. To survive, 

 lobsters require D.O. concentrations of at least 0.3 to 0.4 

 ml/1 (Azarovitz et al. ch. 13). 



Finfishes, lobsters, and crabs are now found in the Bight 

 regions that had low D.O. concentrations in 1976, but the 

 affected benthic ecosystem had not totally recovered by 

 summer 1977 (ch. 12). Certain opportunistic organisms, 

 such as the tube-dwelling polychaetes Polydora socialis 

 and Spiophanes bombyx, have been observed, as have 

 abundant Asabellides oculala. The latter is not usually 

 identified as an opportunistic organism, but such a role 

 has been suggested. Encouraging signs are the recoloni- 

 zation by juvenile surf clams and sand dollars observed 

 off Atlantic City in 1977 (Steimie and Radosh, ch. 12) and 

 the cumaceans, amphipods, and isopods observed in 1978 

 (Reid and Radosh 1979). In 1978, a year when D.O. con- 

 centrations were relatively high, juvenile surf clams were 

 dense (10 per m") in the spring but much less dense in 

 July. 



337 



