MacGREGOR: AMOUNT AND PROPORTIONS OF DDT 



specimens of the myctophid fish, S. leucopsarus, 

 that had been sorted from the plankton collec- 

 tions, were selected for this study to give best areal 

 and temporal coverage. 



Initially a few plankton samples, which were 

 available in much greater quantity, were tested 

 for pesticides. However, the plankton species 

 composition varied in time and with locality, and 

 it was felt that the samples might not be compara- 

 ble. The plankton samples also appeared to con- 

 tain both Aroclor 1242^ and Aroclor 1254 (poly- 

 chlorinated biphenyls (PCB) manufactured by 

 Monsanto Corporation) while the myctophids 

 generally contained only Aroclor 1254 in quan- 

 tity. Plankton samples can include man-produced 

 debris that contains relatively large amounts of 

 CHC or other organic chemicals which interfere 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



with analysis, while individual myctophids are 

 relatively free of such material. Myctophids do not 

 undergo any more horizontal movement than 

 other plankton organisms, and, if they use their 

 motility at all, at least in the coastal waters, it is 

 probably to maintain position over the deeper ba- 

 sins. In addition, they tend to contain more pes- 

 ticide than the invertebrate constituents of the 

 plankton with which they are taken, and they are 

 convenient material to work with. 



The myctophids tested for pesticide residues 

 ranged in standard length (SL) from 14 to 77 mm. 

 They are apparently short-lived fish. Fish of the 

 year can be followed through their first year and 

 into their second by length-frequency distribu- 

 tions (Figure 1). Most of the myctophids tested 

 appeared to be comparable in DDT content to 

 other fish taken at the same time and place, but 

 the amounts in smaller fish were erratic. Some 



10 



20 I 



o 



LU 



60 



70 



80 



:? 



h 





f T T r r T 1 



:7 



' " ' I ' ' ' ' I ' ' ' 



] 



h 



1 1 1 1 1 1 1 1 1 



r 

 ] 



? 



1 1 1 1 1 1 1 



m 



J 

 1 



I 



T 



? 



I 1 1 1 1 



J" 



50 50 5 10 5 50 50 50 50 50 50 50 5 



NUMBER OF FISH BY MONTH 

 MAY JUNE JULY AUG. SEPT. OCT NOV. DEC. JAN. FEB. MAR. APR. 



Figure 1. — Length-frequency distribution of Stenobrachius leucopsarus by month. Shaded area is entering year class. 



279 



