FISHERY BULLETIN: VOL, 77. NO. 3 



Table 2.— Mean abundance (no. Im', no. Im'. and percent total no. /m^), frequency of occurrence (% of 

 samples), average rank, and dominance of the 20 most abundant zooplankton taxa in the New York 

 Bight, September 1974-September 1975. Taxa ranked within each sample on basis of number per 

 square meter 1 1 = most abundant, ties averaged ); ranks for each taxon averaged over all samples (n = 

 178 for chaetognaths. n = 183 for copepods and others). Dominance: proportion of samples in which 

 taxon was among those making up SOT of the individuals; summation in each sample was begun with 

 the most abundant species (Fager and McGowan 1963). 



Taxa 



Pseudocafanus sp 



Reropods 



Centropages typicus 



Paracalanus parvus 



Penilia avirostns 



Temora longicornis 



Calanus ftnmarchicus 



Olthona similis 



Appendicularians 



Gastropod veligers 



Evadne spp 



Doliolids 



Methdia lucens 



Plutei 



O atlantica 



Clausocatanus pergens 



Medusae 



Acartie tonsa 



Sagitta elegans 



Polychaete larvae 

 Total copepods 

 Total chaetognaths 

 Total "others" 

 Grand total 



no.'m^ 



Aburidance 

 no ;m^ 



Frequency 



25.566 



25.532 



25.135 



15.342 



14.613 



11.365 



11.245 



8.293 



7.076 



4.833 



3,901 



3,600 



2.498 



2.239 



1.979 



1.821 



1.419 



1.345 



1.311 



926 



114.383 



2.222 



67.769 



184,174 



521 



479 



655 



312 



454 



373 



146 



146 



126 



113 



91 



90 



21 



51 



22 



16 



27 



43 



26 



20 



2.406 



43 



1.511 



3.960 



138 

 13 8 

 136 

 83 

 79 

 62 

 6 1 

 4 5 

 3,8 

 2 6 

 2 1 

 20 

 1 4 

 1 2 

 1 1 

 1 

 08 

 07 

 07 

 05 

 62 

 1 2 

 36 8 



tumn 1974, and that may have been due simply to 

 escapement of this small-bodied species through 

 the coarse-mesh (333 fxm) net used then. Metridia 

 lucens, C. pergens, and euphausiid calyptopsis and 

 furcilia stages were generally common only 

 offshore, but all others in this group tended to be 

 common throughout the Bight. 



A number of taxa were common only during 

 portions of the year. The oceanic copepod 

 Calocalanus tenuis, cladocerans of the genus 

 Evadne, hyperiid amphipods, and doliolids were 

 common in autumn 1974 and again in summer 

 1975 but were uncommon during the intervening 

 winter-spring period (Table 4). The neretic 

 copepod Temora longicornis, ectoproct larvae, and 

 copepod nauplii occurred commonly during au- 

 tumn 1974 and winter-spring 1975 but were un- 

 common during summer 1975. The cold-water 

 oceanic copepod Pleuromamma borealis occurred 

 commonly only during the winter-spring period 

 and then only offshore. Another oceanic copepod 

 characteristic of warmer waters, Mecynocera 

 clausi, was common offshore during winter-spring 

 and summer 1975. Gastropod veligers were com- 

 mon both onshore and offshore during 1975 but 

 were uncommon throughout the Bight in 1974. A 

 large group of taxa were common only during au- 



tumn 1974. This assemblage consisted of copepods 

 Candacia armata, Oncaea venusta, Acartia tonsa, 

 A. danae, Nannocalanus minor, Centropages 

 bradyi, Rhincalanus nasutus, Eucalanus sewelli, 

 Paracalanus aculeatus, Clausocalanus furcatus, 

 C.jobei, Corycaeus clausi, C. speciosus, Temora 

 stylifera, Scolecithrix danae, and Oithona plumi- 

 fera, the chaetognath Sagitta enflata, the clado- 

 ceran Penilia avirostris, echinoderm plutei, and 

 siphonophores (Table 4). With the exception of the 

 coastal-estuarine species A. tonsa and P. aviros- 

 tris (and probably most of the plutei), members of 

 this group typically inhabit the slope region and 

 adjoining warm oceanic waters (Grice and Hart 

 1962; Owre and Foyo 1967; Bowman 1971). 



The majority of copepods (61) and chaetognaths 

 (7) were uncommon or rare in our samples, and 

 most of these (43) were recorded most frequently 

 or exclusively in autumn 1974 and/or summer 

 1975. Some of these rare and uncommon species 

 are coastal-estuarine forms (e.g., Centropages 

 hamatus, Acartia longiremis, A. hudsonica, 

 Paracalanus crassirostris, Tortanus discaudatus, 

 Labidocera aestiva, Anomolocera opalus, Sagitta 

 hispida) and a few inhabit boreal offshore waters 

 (e.g., Calanus helgolandicus, Heterorhahdus 

 norvegicus), but the majority typically have 



672 



