the same sample. Averaged over all stations sampled, pollock embryos showed 

 46 percent mortality or moribundity, with cod embryos running about 20 per- 

 centage points less. These observed mortalities need to be evaluated 

 against the high levels of naturally occurring egg mortality. Efforts are 

 now underway to assess the impact of these mortalities on the cod and pollock 

 stocks of the Georges Bank-Nantucket Shoals area. Results from laboratory 

 studies conducted jointly with EPA, Narragansett , and Dr. Walter Kuhnhold, 

 visiting scientist with NMFS from the University of Kiel, Federal Republic of 

 Germany, have shown that No. 6 fuel oil will cause mortalities and retarded 

 development of cod eggs at concentrations between 100 and 500 parts per 

 billion. They also report that dying eggs sink to the bottom, indicating 

 that survey collection of moribund eggs may be seriously underestimating 

 actual population mortalities. 



Zooplankton food of larval and adult fish was also contaminated with 

 Avgo Mevahant oil. Copepods were observed with oil on feeding appendages, in 

 alimentary tracts, and on the surface of the body. In addition, oil similar 

 to Argo Merchant oil was in alimentary tracts and fecal pellets of those 

 species collected within and adjacent to the spill area, indicating an im- 

 portant contaminant pathway from the spill into the food web of Nantucket 

 Shoals. Oil ingested by copepods could be concentrated as it moves through 

 the food web as fecal pellets from contaminated zooplankton are ingested by 

 filter feeders, or if zooplankton containing oil are eaten directly by preda- 

 tors including larval and adult fish. Argo Merahant oil is persisting in the 

 food web; as recently as February 23 1977, copepods were collected which, 

 under microscopic examination, contained petroleum residues. 



Substantially smaller numbers (80% less) of larval sand launce at sta- 

 tions sampled within the spill zone, compared to outside the zone, may have 

 been caused by the toxic effects of oil. Although not a commercially impor- 

 tant species at this time, the sand launce is an important food of fish, 

 including cod, haddock, pollock, and hake. It is also eaten in large quanti- 

 ties by whales and porpoises. The effect of these lower numbers of larvae on 

 the production of sand launce in the Nantucket Shoals and Georges Bank area 

 is presently under study by NMFS scientists of the Northeast Fisheries Cen- 

 ter. 



Scientists of NMFS working at the Milford Laboratory detected imbalances 

 in the normal physiological responses of mussels and scallops collected from 

 the waters contaminated with oil. Respiration rates were lower than in 

 samples collected outside of the spill zone. Also, the ionic balance of 

 blood serum is blackback and yellowtail flounders was lower than in control 

 specimens collected from outside the spill area. 



It is not possible at this time to extrapolate from the oil-caused 

 mortalities and sublethal effects observed to the impact on the productivity 

 of the Nantucket Shoals-Georges Bank ecosystem. Additional sampling and 

 experimentation over the next year is required for an adequate assessment of 

 damage . 



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