Table 2. — Partial listing of invertebrates from otter trawl samples off Point Lay, Alaska. 



CLASS 

 Subclass 



(It'nus species 



CLASS 

 Subclass 



(reniis species 



GASTROPODA 



Biiccintim sclarifnrme Mtiller 



Mnrgarilnpsis prihiloffensis (Dall) 



Dendrunotiis dalli Bergh 

 BIVALVIA 



Miisculus discnrs (Linnaeus) 



Yoldia scissiifata Dall 



Serripcs f^roenlandicus (Bru^gen) 



Mya truncata Linnaeus 

 MALACOSTRACA 

 Mysidacea 



\fysis oculata and/or M. litoralis 



Neomysis rayii (Murdock) 

 Isopoda 



Tecticeps alaskensis Richardson 



Synidotea hicuspida (Owen) 

 Amphipoda 



Anonyx nugax (Phipps) 



Tryphosa sp. 



Acanthostepheia behringiensis (Lockington) 

 Paroediceros lynceus (M. Sars) 



I'rotomcdia fiisctntn Kriiiyer 

 Ischynn-crus latipes Krsiyer 

 /. mvfialaps Sars 



Kriclhonius difformis M. Kdwarris 

 E. tolli Bruggen 

 I'leustt's pnntipta (Krv^yer) 

 Rhocotrnpis actiU'ata (LepechinI 

 DiiHchia spinnssisma Krrfyer 

 Decapoda 



Pandcitus utmiurus Stimpson 

 Eualus fahricii (Kr»(yer) 

 E. naimardii (M. Edwards) 

 l.ehheus gnienlandicus (.). C. Fahricius) 

 Spinontncaris phippsii (Krtlyer) 

 Arnis lar (Owen) 

 Sclerocran^on horeas (P)iippsl 

 llyos coarctcUus Leach 

 Pniiurus tri^imnvheirus (Stimpson) 

 ASCIDIACEA 



BoUenia ovifera (Linnaeus) 



though the resulting catches should be considered only as 

 semiquantitative, they do provide indicators of the kinds 

 and general quantities of midwater invertebrates present 

 in the southeastern Chukchi Sea. 



The terms mesoplankton, macroplankton, micronek- 

 ton, and benthos may be applied to various grouping of 

 invertebrates collected with the Isaacs-Kidd midwater 

 trawl in the Chukchi Sea during WEBSEC-70. None of 

 the terms are precisely defined, but they provide criteria 

 for evaluation of catches by those who may wish to com- 

 pare the species and quantities reported in Appendix 

 Table 2 with other sets of data. 



Mesoplankters are zooplankters quantitatively retain- 

 ed by a 0.2-mm mesh net and having a total body length 

 less than 10 mm. Large mesoplankters are those with a 

 body length greater than 1 mm. The midwater trawl used 

 during WEBSEC-70 did not quantitatively retain large 

 mesoplankters, as evidenced by the low frequency and 

 small numbers of copepods Calanus finmarchicus s.l. 

 and Eucalanus bungii and the chaetognath Sagitta 

 elegans in the catches. These mesoplankters were widely 

 distributed and abundant in plankton samples taken 

 with a 0.57-mm mesh plankton net during the same 

 cruise (Wing 1974). 



Animals of the macroplankton and micronekton are 

 large enough to be identified with the naked eye. There is 

 no upper size limit and the lower size limit (5-10 mm 

 long) is dependent on the taxa involved and the knowl- 

 edge of the researcher. Animals of the micronekton are 

 10-100 mm long and can swim well enough to avoid stan- 

 dard 1-m plankton nets. Because the swimming ability of 

 crustaceans, cephalopods, and fishes increases with size, 

 macroplankton and micronekton are not precisely defin- 

 ed or clearly separable categories. Within the size range 

 of macroplankton and micronekton, the midwater trawl 

 used during WEBSEC-70 would collect quantitatively 



only the large scyphomedusans and the hydromedtisan 

 Cuspidella mertensii. Although herding occurs, much of 

 the macroplankton and micronekton passes through the 

 6- and .38-mm meshes at the front of the net. Many of the 

 hydromedusan Aglantha digitale, the euphausiids, and 

 the mysids undoubtedly passed through the net, al- 

 though these were the most abundant organisms in the 

 catches (Appendix Table 2). The retention of 

 macroplankton- and micronekton-sized medusans, 

 amphipods, mysids, euphausiids, and shrimps by the 

 midwater trawl used during WEBSEC-70 indicates that 

 they were quite abundant and important in the trophic 

 structure of the area but does not measure their abun- 

 dance. 



Many of the species collected by the midwater trawl in 

 the Chukchi Sea are considered to be benthic animals, 

 i.e., they live on (epibenthos), in (endobenthos), or just 

 off (hyperbenthos) the bottom. Many of the benthic 

 animals, especially polychaetes, mysids, cumaceans, 

 gammarid amphipods, and shrimps, may leave the bot- 

 tom at night and become part of the macroplankton and 

 micronekton. Except for stations 8 and 14 (Table 1), all 

 sampling was at night: consequently some benthic 

 animals were well represented in the collection. 



The shallowness of the area (22-54 m) sampled by 

 WEBSEC-70 contributed to the occurrence of benthic 

 animals in the midwater trawl catches. Benthic animals, 

 which rise off bottom at night, are likely to contribute 

 more to the macroplankton and micronekton in shallow 

 waters than in deeper waters. Additionally, wave-in- 

 duced turbulence and ice rafting may have placed in sus- 

 pension some endobenthos (i.e., benthic snails, sipun- 

 culids, and echiuroids), which would not normally be off 

 bottom. The net struck bottom only on station 88. 

 Samples from that station contained two species of snails 

 (Margarites sp. and Natica clausa), a clam {Nucuia 



