JUDKINS ET AL.: ZOOPLANKTON IN THE NEW YORK BIGHT 



Table l. — Zooplankton sampling data for the New York Bight region. 1974-75. Net mesh aperatures and mouth diameters indicated by 

 letters: A. 333 ;um, 60 cm; B, 253 ^cm (February 1975 only) or 223 /Am, 20 cm. For station locations see Figure 1. 



'Maximum sample depth - 200 m, 



or more individuals were counted. Abundances of 

 taxa within individual samples and related data 

 are available in a data report ( Judkins^) and from 

 the senior author. In our treatment of the cross- 

 shelf distribution of zooplankton, we divided the 

 study region into two sectors of equal area, an 

 onshore zone shoreward of the 50 m depth contour 

 and an offshore zone seaward of that contour. Each 

 sector contained 10 zooplankton grid stations 

 (Figure 1). This division yielded approximately 

 equal numbers of onshore and offshore samples 

 and provided an easy test for cross-shelf differ- 

 ences in species abundances. 



In Tables 2 and 3, we list abundances as both 

 concentrations (numbers/cubic meter) and stand- 

 ing stocks ( numbers/square meter ). We calculated 

 concentrations primarily for comparison with the 

 historical data which have been reported almost 

 exclusively in that manner. However, it would be 

 an error to compare concentrations from different 

 locations in the New York Bight because of the 

 wide range of depths of stations and the vertical 

 stratification of zooplankton. Estimates of 

 numbers/cubic meter from oblique tows are aver- 

 age values for the entire water column, and these 

 would be adequate for comparisons of tows from 

 different depths only if zooplankton were evenly 

 distributed throughout the water column. How- 

 ever, if a species is restricted to a narrow depth 

 stratum, then its concentration would be underes- 



^Judkins, D. C. Zooplankton sampling program and da- 

 ta. In E. Wold (editor), Atlantic coastal experiment survey 

 cruises (July 1974-September 1975) data report Vol. 2. Zoo- 

 plankton and ichthyoplankton, p. 2-129. BNL 24771. Brookha- 

 ven National Laboratory, Upton. N.Y, 



timated by deeper tows relative to shallower ones 

 (Peterson and Miller 1977). Vertically discrete 

 samples show that most species in the New York 

 Bight are concentrated in the upper 20 to 30 m 

 ( Judkins unpubl. data). To avoid underestimating 

 species abundances in samples that extended 

 below about 30 m, we calculated standing stocks 

 and were then able to obtain mean values for com- 

 binations of tows from different depths and to test 

 for significant differences between these means. 



RESULTS 



Frequency of Occurrence of 

 Zooplankton Taxa 



We identified 88 copepod species, 10 chaetog- 

 nath species, and 26 other holo- and meroplank- 

 tonic taxa (Table 4). By season, 100 taxa occurred 

 in samples taken in autumn (September- 

 November) 1974, 68 in samples from winter to 

 spring (February-May) 1975, and 91 in samples 

 from summer (June-September) 1975. 



These taxa can be grouped on the basis of sea- 

 sonal and cross-shelf patterns in occurrence. The 

 taxa in one group occurred commonly during all 

 seasons and included the copepods Centropages 

 typiciis. Pseudocalanus sp. .Calanus finmarchicus, 

 Paracalanus parvus, Oithona atlantica, Metridia 

 lucens, and Clausocalanus pergens, the chaetog- 

 naths Sagitta elegans and S. serratodentata, and 

 pteropods, appendicularians, medusae, poly- 

 chaete larvae, bivalve veligers, and euphausiid 

 furcilia and calyptopsis stages (Table 4). The 

 copepod O. similis was uncommon only during au- 



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