NOAA PROFESSIONAL PAPER II 



METHODS 



Commercial hydraulic dredges, scallop dredges, and 

 otter trawls were used to sample the bivalves. Table 11.1-1 

 lists the dates, vessels, affiliations, and types of gear used 

 to collect the clams and scallops. 



Stress in and deaths of bivalves could be recognized 

 visually. Divers saw clams lying on the bottom, and scal- 

 lops gaping. Gaped bivalves were also collected in dredges 

 and trawls. The gaped bivalves were extremely lethargic. 



The bivalves killed by the oxygen depletion event could 

 be easily recognized. Some had meats attached to their 

 valves. With most, however, only paired valves remained. 

 The outer surfaces were at least partially blackened, and 

 the inner surfaces were white and did not contain fouling 

 organisms. A few of the collected bivalves had died before 

 the event. Surf clams and sea scallops did not have black- 

 ened valves and most contained fouling organisms. Ocean 

 quahogs had a brown scum on the inner surface of their 

 valves. 



The catch and percentage of live and dead clams or 

 scallops (mortality ratios) were recorded by dredge tow 

 and by specific depth ranges and plotted on charts. The 

 bottom area sampled by the dredge during one tow was 

 divided into the total area being sampled to obtain the 

 total number of sampling units. The number of clams or 

 scallops in the total area then was estimated by multiplying 

 the mean catch per tow by the number of sampling units. 

 For determining clam biomass, estimates of total clam 

 numbers were converted to meat weights; only total num- 

 bers of scallops in each area were compared. 



EARLY REPORTS AND INTERVIEWS 



The first signs of stress and mortality of surf clams were 

 reported by scuba divers in New Jersey on July 4, 1976. 

 One diver saw surf clams lying on the bottom off Man- 

 asquan Inlet. Twenty days later (July 24, 1976). another 

 scuba diver saw 1 live clam and 24 dead ones lying on the 

 bottom 6 km northeast of Absecon Inlet. The observations 

 of surf clams lying on the bottom were unusual, because 

 the clam is normally embedded (Ropes and Merrill 1973). 



Otter trawl vessels working off New Jersey provided 

 observations on stress and mortality of clams and scallops. 

 On July 9, 1976, a vessel sampled two sites. Dead clams 

 were found at a site 17 km east of Belmar, but no clams 

 were collected at the second site. 



On July 13 and 15, 1976, a vessel reported gaping surf 

 clams in four tows 19 and 28 km east of Ship Bottom, 

 Barnegat Inlet, and Bayhead. 



On July 20 and 21, 1976, a vessel sampled two sites 18.5 

 km east of Bayhead and Barnegat Inlet. Dead surf clams. 



paired valves, clam meats, and live clams were in the 

 catch. The paired valves of one sea scallop were taken in 

 the sample off Bayhead. 



On July 28 and 30, 1976, a vessel sampled three sites 

 east of Manasquan Inlet and Barnegat Inlet. Dead sea 

 scallops were found east of Manasquan Inlet; dead surf 

 clams, paired valves, and gaping live clams were found 

 east of Barnegat Inlet. Separated meats were in the trawl 

 netting. 



Samples from surf clam dredges were observed for sur- 

 vival, stress, and death of benthic epifauna and infauna. 

 On July 9, 1976, three locations 4 to 11 km east of Bar- 

 negat Inlet were sampled. Gaping clams were collected 

 at one location. On July 28, 1976, a commercial surf clam 

 vessel dredged at four sites from Seaside Park to Barnegat 

 Inlet 5 to 11 km offshore and where the captain had found 

 extensive mortalities a week earlier. Clam mortalities 

 were U) to 56 percent. 



Surf clam fisherman reported clam mortalities from 

 Manasquan Inlet to Ocean City, N.J., during July 12 to 

 August 26, 1976. 



ASSESSMENT SURVEYS 



During August 6-17, 1976, observations of stress and 

 mortality in surf clams and sea scallops were provided 

 from otter trawl samples for finfish (Northeast Fisheries 

 Center 1976b). Samples were taken at 97 stations from 

 Sandy Hook, N.J., to off Assateague Island, Md., from 

 nearshore to 117 km offshore at depths of 7 to 66 m. 

 Stressed and dead surf clams were collected at 28 stations 

 off Barnegat Inlet, Little Egg Inlet, and Townsend Inlet 

 about 5 to 60 km from shore at 14 to 38 m. Most surf 

 clams collected were dead (59.99?-), although the remain- 

 ing live clams (40.1%) were obviously lying on the bottom. 

 The meat of one sea scallop was collected 46 km east of 

 Barnegat Inlet at 37 m, and two dead scallops with meats 

 and three paired shells were found 54 km east of Beach 

 Haven Inlet at 35 m. 



During September 28 to October 18, 1976, observations 

 of stress and mortality of surf clams, ocean quahogs, and 

 sea scallops were again obtained from otter trawl samples 

 for finfish (Northeast Fisheries Center 1976c). Samples 

 were taken at 179 stations from Martha'a Vineyard, 

 Mass., to Cape Hatteras, N.C.. at 16 to 365 m. Of 39 

 stations off the New Jersey coast, stress and mortality in 

 surf clams and ocean quahogs were recorded at only 4 

 stations. Stressed sea scallops were found at a station east 

 of Asbury Park at 40 m. 



During December 5-21, 1976, stressed and dead surf 

 clams, ocean quahogs, and sea scallops continued to be 

 collected in otter trawl samples for finfish (Northeast Fish- 

 eries Center 1976d). Samples were taken at 45 stations off 



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