34 



Fishery Bulletin 88(1), 1990 



Figure 4 



Walleye pollock embryos exposed to water-soluble fraction (3.6 ppm 

 in the embryo shown) of Cook Inlet crude oil developed abnormal 

 vesicles (arrow) along the ventral surface, usually posterior near the 

 blastopore. 



abnormalities was also high (r = 0.99). Median concen- 

 trations causing abnormalities at hatch ranged from 

 1.6 ±0.2 to 2.1 + 0.6 ppm (Table 8). 



Deformed larvae did not recover from their abnor- 

 malities in clean water. In many cases the abnormalities 

 became more pronounced as developing structures 

 failed to form properly: 21 days after hatch a few 



abnormal larvae were still alive, but most (88%) had 

 died (control mortality was 10%). 



Discussion 



Early embryonic development, as indicated by differ- 

 ences in blastopore diameters, was delayed by exposure 

 to WSF, but the timing of hatch was not affected. 

 Developmental stages (Yusa 1954) of controls and 

 treated embryos were similar at all times except dur- 

 ing blastopore closure. In other studies involving WSF 

 tests of crude oils (Venezuelan, Iranian, Libyan), devel- 

 opment of cod Gadus morhua embryos slowed, depend- 

 ing on concentration (Kiihnhold 1974). 



Genetic differences or differences in WSF prepara- 

 tions may account for the greater sensitivity observed 

 in 1983 than in 1982. The WSF contained a higher pro- 

 portion of diaromatic compounds in 1983 than in 1982, 

 and diaromatics are generally more toxic than mono- 

 aromaties (Rice et al. 1977). However, these sensitivity 

 differences were only in magnitude of response; basic 

 response patterns were the same. 



Increased metabolic demand may explain the ob- 

 served reductions in yolk sizes of newly hatched larvae 

 exposed to WSF during embryonic development. Yolk 

 size was negatively correlated with concentration in 

 both treatments, and yolk sizes tended to be smaller 

 in embryos exposed for the longest period of time (0-21 

 day treatment), suggesting increased consumption of 

 yolk and elevated metabolism. Linden (1978) also con- 

 cluded that shorter lengths of larval Baltic herring 

 Clupea harenguf! membras at hatching probably re- 

 sulted from increased energy demands during exposure 

 to the WSF of several oils. Other researchers have 

 measured increases in metabolic rate directlv: for 



