FISHERY BULLETIN: VOL. 76, NO. 1 



.44 

 PCCKSKILL 



STONY 

 POINT 



Figure l. — Sampling stations, depths, and collection methods 

 for Atlantic tomcod, Haverstraw Bay 1973-75. Numbers along 

 river indicate mile points above the Manhattan Battery. Station 

 1: 6.7 m; trawl, epibenthic sled. Station 2: 12.2 m; epibenthic 

 sled. Station 3: 7.6 m; trawl. Station 4: 3.0 m; epibenthic sled. 

 Station 5: 18.3 m; trawl, epibenthic sled. Station 6: 16.8 m; 

 epibenthic sled. Station 7: 13.7 m; trawl, epibenthic sled. 



Bottom temperature (Figure 2), dissolved oxy- 

 gen, and salinity (Table 1) were measured at sta- 

 tion 2 (depth 12.2 m). 



Fish were preserved in 5% (epibenthic sled col- 

 lections) or 10% (trawl collections) buffered For- 

 malin.^ Total length of each fish was measured to 

 the nearest millimeter. Fish >50 mm were 

 weighed to the nearest 0.1 g; fish <50 mm were 

 weighed to the nearest 0.01 g. Stomachs were re- 

 moved and transferred to a 70% solution of eth- 



anol prior to analysis. One everted fish stomach, 

 indicative of regurgitation, was excluded. Food 

 organisms were identified, counted, and the entire 

 contents, excluding obvious nonfood items (e.g., 

 pebbles), of 401 stomachs were dried to a constant 

 weight at 103°C. 



Only postlarval juveniles were studied; the dis- 

 tinction between larval and juvenile tomcod was 

 the completed differentiation of the fins (Balon 

 1975). Lower limits of adult fin ray counts were 

 taken from Bigelow and Schroeder (1953). Appli- 

 cation of this criterion showed that a total body 

 length of 25 mm represented the lower size limit of 

 juveniles. During 1973, young-of-the-year were 

 distinguished from yearlings by examination of 

 length-frequency histograms of larger sample 

 sizes of tomcod (Lawleretal. see footnote 6; Lawler 

 et al.^°). Fish collected during November and De- 

 cember 1973, 148 and 160 mm, respectively, were 

 considered to represent upper size limits of 

 young-of-the-year. All fish collected during 1974 

 and December 1975 were condsidered young-of- 

 the-year. 



Stomach content data were pooled by month and 

 quantitative results for each taxon calculated as 

 percent occurrence, percent composition, and im- 

 portance (Windell 1971): 



Importance = / (% composition) (% occurrence). 



Percent relative importance was calculated by 

 summing importance values at the lowest 

 taxonomic level and dividing individual impor- 

 tance values by that sum. A modified similarity 

 index (Windell 1971) was then calculated to com- 

 pare monthly changes in percent relative impor- 

 tance of various food items, at the lowest compara- 

 ble taxonomic level. Consecutive months were 

 compared by selecting the lesser of two relative 

 importance values for each food item and then 

 summing them. This sum is the index of similarity 

 and it may range from to 100%. 



An index of fullness ilf) (Nikolsky 1963; Windell 

 1971), indicative of feeding intensity, was calcu- 

 lated for each fish: 



// 



stomach content biomass (g* x 10^ 

 weight (g) of fish 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



'"Lawler, Matusky and Skelly Engineers. 1974. 1973 Hudson 

 River aquatic ecology studies: Bowline Point and Lovett Gen- 

 erating Stations. Prepared for Orange and Rockland Utilities, 

 Inc. 



90 



