30 U. S. BUKEAU OF FISHERIES. 



The contents of 48 stomachs of fishes taken in ponds and streams in 

 northern New Jersey reported in Table 4 (p. 29) agree fairly well 

 with Pearse's statement. Chironomid larvae constituted the largest 

 single item, or about 33 per cent; other insect remains, 11 per 

 cent; crustaceans (with the exception of a few isopods, all ento- 

 mostracans), 19 per cent; miscellaneous animal remains, 13 per cent; 

 and plant remains, mostly filamentous algse, organic ooze, and 

 debris, 20 per cent. A single Culex fifiens larva was found in 

 each of two stomachs, two in another, and an Anopheles larva in 

 still another. Three of these fish came from Oakes', the other 

 from Vanderbilt's Pond. All of these were taken in September, 

 and it is of interest to compare conditions in the three ponds 

 selected for illustration, from two of which they came. All are 

 located on Third River, a tributary of the Passaic, in a series of 

 which Oakes' is ih^ uppermost and Vanderbilt's the lowermost. 



Oakes' Pond in large part was heavily grown to aquatic and emer- 

 gent vegetation, particularly at the much silted-up head, and at the 

 time of the author's visits was so bad a breeding place of Culex pipiens 

 and Anopheles that the Essex County Mosquito Commission had 

 declared it a nuisance and was cooperating with the owners in 

 revising its shores and channel. Small fishes were found in mod- 

 erate numbers, the species collected being roach, translucent killifish, 

 young carp, and chub sucker. Eoach were most plentiful. The 

 point at which those reported upon were taken is a bit of open 

 shelving beach free of vegetation. On each side of this was a zone 

 of Elodea extending continuously as a barrier a few feet from the 

 shore. In the space behind the Elodea was a growth of emergent 

 plants chiefly composed of Sagittaria, Pontoderia, Polygonum, 

 sedges, and grasses of varying density. Here Culex pipiens and 

 Anopheles were found generally in numbers varying from place to 

 place. No larvae were found in the open space at the beach. Of 

 22 killies (Table 4, No. 18906b) examined at least three had eaten 

 mosquito larvae, which they must have secured behind the Elodea 

 barrier. The principal food was chironomid larvae, aggregating 

 about 60 per cent of the total contents. It should be noted that none 

 of the young roach which were taken at the same place and time 

 were found to contain mosquito larvae. 



Davies' Pond, lying next below Oakes', is generally similar but 

 v^as noted to differ in the following respects : It was less filled with 

 silt, and the vegetation, though similar, was less dense. On one 

 side it was heavily shaded by a wood of large trees, and the bank 

 here was fairlj^- steep with little marginal or emergent vegetation. 

 On the other side, which was also shaded but less densely, the water 

 was very shallow, with the Elodea zone sparse and far out. There 

 was consequently a broad inner zone of open water nearly free from 

 vegetation in which killifishes were seen in large numbers and some 

 collected (Table 4, Nos. 18906m and 18906p). At all points around 

 the shore this species was encountered in large schools, and it was 

 practically the only species of small fish present. Personally the 

 author failed to find a single mosquito larva in this pond, and Mr. 

 Brooks stated that the inspectors always reported practically no 

 breeding here. 



Vanderbilt's, the next pond below, is a larger body of water, which 

 has a bad reputation among the Essex County inspectors as a source 



