the spill area. The reasons for the decrease are not clear, but the analysts 

 assume that the decrease In population may be associated with the negative 

 impact of the oil on the viability of larvae. Samples collected from this 

 area during the second Betccuave II cruise, DE 77-1, will be examined to 

 corroborate this assumption. The sand launce, while not important in the 

 commerical fishery, is a key species in the ecosystem. It is the basic food 

 of predatory fish, including cod, haddock, silver hake, as well as marine 

 mammals, including porpoises and whales. Little can be said about the other 

 species as they occurred in very low numbers ( 15 per station) over the 

 entire survey area. 



The most notable change was in the decrease of sand launce larvae at 

 Stations 7 and 8 within the spill zone. This decline in abundance may have 

 been related to Argo Mer>ohant oil contamination. Additional sampling of the 

 area will be conducted to assess sand launce stocks in an effort to estimate 

 the range of "normal" variation in population distribution and abundance. 

 Also, mortality among pollock eggs was increased significantly in the area of 

 the spill, as evidence by the large numbers of moribund embryos in eggs con- 

 taminated with oil. Cod mortality occurred but was lower. Studies are 

 underway to obtain estimates of the extent of mortality inflicted on the 

 populations of both cod and pollock stocks by the Argo Merchant oil. 



4.1.3 Genetic Studies 



These studies were contributed by A. Longwell of NMFS, NEFC, Milford, 

 Connecticut and are based on samples collected on the first cruise of the 

 Delaware II, DE 76-13. 



It has been demonstrated In the laboratory that compounds extracted from 

 oil films are toxic to fish larvae and to the early developmental stages of 

 planktonic fish eggs. Failure in the past to establish detrimental effects 

 of oil spills in the field may be attributable to the lack of sufficient, 

 appropriate field tests that might be conducted quickly and cheaply enough 

 when the need arises, as well as to the fortunate resiliency of the ecosys- 

 tem. However, extrapolation of laboratory data to the field without ade- 

 quate field testing can be done only with the utmost caution. 



Toxicity of oil components will, of course, vary according to the 

 developmental stages of the eggs at exposure. That there are sublethal 

 effects which lead to later mortality of the fish eggs is evident from the 

 published literature on experimental studies. Teratogenic effects (deform- 

 ities) are common in oil toxicity tests. 



Aromatic hydrocarbons are highly soluble in lipid material as present in 

 the yolky contents of fish eggs. Polynuclear aromatic hydrocarbons can act 

 both as carcinogens and mutagens. Benzene, the most abundant aromatic com- 

 pound in crude oil, has been proved mutagenic in a number of published gene- 

 tic tests on organisms other than fish. Concentration of such hydrocarbons 

 in the fatty material of spawned eggs may, accordingly, well provoke both 

 cytotoxicity and mutagenicity to the chromosome apparatus in the critical 

 early development stages of planktonic or demersal fish eggs. Their absorp- 

 tion through the membrances of planktonic fish eggs spawned in the vicinity 



103 



