at 500 ppb sink to the bottom of the test jars prior to dying. This phenom- 

 enon is due to loss of osmoregulation in the embryonic organism. Some eggs 

 may actually sink to the bottom several days before dying. It was also 

 observed that the development was greatly delayed in the higher concentra- 

 tions, and that the heart beat was greatly reduced. From the beginning of 

 regular heart muscle contractions to hatching, the frequency normally in- 

 creased from about 30 to 70 beats per minute in untreated eggs, while the 

 treated eggs showed a decrease in frequency of heart beat to less than 20 

 beats per minute with very irregular muscle contractions. Anderson et al. 

 (1976) have indicated that the heart beat rate can also serve as a sensitive 

 indicator for sublethal effects. This was evident in the eggs exposed to the 

 intermediate concentration (100 ppb) , which in some cases showed no sign of 

 developmental delay or abnormalities, but did have reduced heart beats. Ten 

 ppb does not appear to increase embryo mortality or alter hatching rates. 



Further evaluation of the data should clarify the relationship between 

 hatching and survival rates of larvae and embryonic heart beat frequency. 



4.1.5 Food Habits 



This section was contributed by R.. Langton and R. Bowman of NMFS, NEFC, 

 Woods Hole, Massachusetts, and is based on samples collected from both 

 Delaware II cruises (DE 76-13 and DE 77-01). 



Stomachs were collected from fish caught with an otter trawl during the 

 Delaware II cruises 76-13 and 77-01 (Figure 4-8; Table 4-5 and Table VII-17 

 in Appendix VII). The fish stomachs were excised aboard the ship, labeled 

 according to species, length, and station, and preserved in 10% formalin. A 

 total of 305 stomachs were collected from the 16 different species of fish. 



At the NEFC laboratory. Woods Hole, the preserved stomachs were opened 

 and the contents washed onto a 0.25-millimeter mesh screen. The various food 

 organisms were manually sorted, identified to the lowest taxa possible (with 

 a dissecting microscope when necessary), and damp-dried on bibulous paper. 

 Each taxonomlcally distinct group was weighed to the nearest 0.01 gram on a 

 Mettler balance immediately after being dried. Parasites in the stomach were 

 included as part of the stomach contents. Food items of little dietary 

 significance or those that were unidentifiable because of the degree of 

 digestion were classified as miscellaneous. 



For the purpose of analysis all information was pooled by species, 

 regardless of size, for comparison with existing food habits data. Data for 

 each predator are presented as a percentage of the total stomach contents 

 weight and as mean weight per stomach. The mean weight per stomach was 

 calculated by dividing the total stomach contents weight by the total number 

 of stomachs examined. 



The food habits of six species of fish were investigated following the 

 first Delaware II cruise, DE 76-13, and are summarized in Table VII-18 in 

 Appendix VII. The same six species plus an additional 10 were sampled during 

 the second Delaware II cruise, DE 77-01 (Table VII-19 in Appendix VII). The 

 food habits of the six co-occurring species were generally similar between 



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