urxrtDIj. r \J\JLJ c\i^LJ r iJiJL/ii'^ \^r i irvui i o ^-^i- rv i L.i-vi'^ 1 1*^ & v^nivyv/xv 



Figure 2. — Bottom water tempera- 

 tures at Station 2, Haverstraw Bay 

 (mile point 37.5). 



M 



M J J 

 MONTHS 



N 



Table l. — Mean monthly bottom dissolved oxygen and salinity 

 measurements at Station 2, Haverstraw Bay (mile point 37.5) 

 1973-75. 



Dissolved oxygen (mg/l) 



Salinity (%«) 



average number of food items per stomach (Table 

 4), with feeding greatest during May, June, Oc- 

 tober, and November, and lowest during July- 

 September. Feeding also decreased during De- 

 cember. Growth of the 1974 year class paralleled 

 seasonal alterations in If (Figure 3). 



The trends of the above parameters suggested 

 that seasonally fluctuating environmental vari- 

 ables (e.g., temperature and dissolved oxygen) 

 might be affecting feeding intensity and, there- 

 fore, growth. Statistical tests to discriminate the 



Ranking dominant food items by importance 

 (Table 2) revealed two distinct dietary regimes: a 

 May-June diet of copepods and a July-December 

 diet of amphipods, mysids, and isopods. The simi- 

 larity index for consecutive months emphasized 

 this shift by a markedly low value (39%) for 

 June-July compared with a range of 54-80% for 

 other months. 



Pooling June and July fish by 10-mm length 

 intervals indicated that copepod importance de- 

 creased and that of amphipods increased as mean 

 length increased. At 90 mm, transition to an 

 amphipod-dominated diet was complete (Table 3). 



A seasonal feeding cycle was distinguished by 

 trends in If, percentage of empty stomachs, and 



Figure 3. — Index of fullness (If) and growth of juvenile Atlantic 

 tomcod, Haverstraw Bay, June-December 1974. 



91 



