Pelagic Amphipod Crustaceans from the Southeastern Bering Sea, 



June 1971 



GERALD A. SANGER' 



ABSTRACT 



Fourteen species of pelagic amphipods were present in zooplankton samples collected from the 

 southeastern Bering Sea in June 1971. Paralhemisto pacifica strongly dominated relative abundance 

 (68-96%) and was present in numbers up to an estimated 2,755/1,000 m^ of water. Primno macropa was 

 the only other species present in all hauls and ranged from 4 to 27% in relative abundance. Cyphocaris 

 challengeri was present in numbers up to 48/1,000 m^ during night hauls, but only one animal was taken 

 in all daylight hauls. Hyperia medusarum was present in 14 (82%) of the hauls but accounted for less than 

 1% of the total numbers. 



A presumed diurnal vertical migration was evidenced for Primno macropa, Cyphocaris challengeri, 

 and possibly for Scina rattrayi, Hyperoche medusarum, and Hyperia medusarum. 



The occurrence of Scina stebbingi. S. rattrayi, Vibilia caeca (?), Paraphronima crassipes, Phronima 

 sedentaria, and Primno macropa extended their known ranges in the Bering Sea eastward, and the 

 occurrence of Cyphocaris anonyx represents a new record for the Bering Sea. 



INTRODUCTION 



Cruise K71-3 of the RV George B. Kelez (North- 

 west Fisheries Center, National Marine Fisheries 

 Service, Seattle, Wash.) was conducted in the south- 

 eastern Bering Sea from 21 May through 1 1 June 1971. 

 One objective of the cruise was to survey the diurnal 

 variation in kinds of zooplankton occurring in the 

 upper layers of this biologically little-known area. To 

 this end, a series of 18 hauls was made at a floating 

 position-reference buoy (see below) over a 30-hr 

 period on 8-9 June (Fig. 1). 



This report lists the species of amphipod crusta- 

 ceans collected and discusses aspects of their diurnal 

 variation in numbers and occurrence during the 30-hr 

 period. A few selected amphipods collected by the 

 International North Pacific Halibut Commission east 

 of the K71-3 cruise area in July 1971 are also noted and 

 briefly discussed. 



METHODS 



A transponding telemetering buoy, attached to a 

 parachute drogue at a 10-m depth, was released on 8 

 June to provide a reference point for monitoring vari- 

 ous oceanographic parameters of the same parcel of 

 water in real time. Zooplankton samples were col- 

 lected with a "bongo" net array, which consisted of 

 two 60-cm (mouth diameter) and two 20-cm frames, 

 one each equipped with nets of 0.333-mm and 



'Northwest Fisheries Center. National Marine Fisheries Service. 

 NOAA. 2725 Montlake Boulevard East, Seattle. WA 98112; pres- 

 ent address: Marine Mammal Division. Northwest Fisheries 

 Center. National Marine Fisheries Service, NOAA. Naval Support 

 Activity, Bldg. 192. Seattle. WA 98115. 



0.505-mm mesh. A 122-cm Braincon® V-fm depressor 

 was used, and TSK* flowmeters were mounted out- 

 side the array and in the mouth of its 60-cm, 0.333-mm 

 mesh net. Towing depths were monitored with a 

 model 1170 Benthos* time-depth recorder. 



Tows were oblique between the surface and a nomi- 

 nal maximum depth of 200 m. Towings were at speeds 



5 4* N 



5 3*N 



Figure I. — Southeastern Bering Sea. showing the extent of drift of 

 the 10-m parachute drogue between 0700 on 8 June and 1300 on 9 June 

 197 1 . Repetitive bongo net hauls were made at the drogue throughout . 



