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A series of zooplankton samples was obtained by high-speed sampling at the surface, in the Bering Sea and northern North Pacific during the cruise of the Oshoro Maru from June to August 1960. The average biomass of the zooplankton in all the samples was 390 g/1,000 m3 wet weight. Very high values were obtained in the northern part of the Gulf of Alaska (1,169 g/ 1,000 m3) and off the south of the Aleutian Islands (888 g/1,000 m3). Thirty-nine species of copepods were identified from the samples. The area investigated could be divided into three regions by the composition of copepods : 1) the cold offshore water region characterized by Calanus plumchrus-C. cristatus population, 2) the warm offshore water associated with Calanus pacificus and several warm oceanic species, 3) the neritic water mass represented by Pseudocalanus minutusAcartia longiremis population. The relationships between the total numbers of zooplankton and phytoplankton suggest that in the offshore region the phytoplankton population is grazed down by zooplankton within a considerably short period, resulting in the poor standing crops, while sufficient phytoplankton standing crops are available in the neritic region because of less active feeding of the neritic consumer. Introduction Knowledge of distribution of zooplankton, particularly on copepods, in the northern region of the North Pacific and the Bering Sea has increased considerably in recent years through the contributions made by JOHNSON (1953), ANRAKU (1954), BRODSKY (1955, 1959), MINODA (1958), MARUMO et al. (1960), and MCALLISTER (1961). The Oshoro Maru of Hokkaido University made a cruise to and from Juneau, Seattle from June 6 to August 29, 1960, and on this cruise zooplankton was collected by several methods including high-speed sampling. The author had an opportunity to join the cruise and to process the high-speed samples. This report deals with the zooplankton, mainly copepods, in the high-speed samples, in an attempt to picture the distribution of zooplankton in the surface water of the Bering Sea and northern North Pacific. The hydrographic and some of the biological data on the cruise have been published in the " Data Record of Oceanographic Observations and Exploratory Fishing " No. 5 (Hokkaido University, 1961). Methods of sampling and processing Because of lack of the ship's facilities and shortage of time due to the multiple purposes of the cruise, only simple gear was available for sampling. The sampler used was an Underway Plankton Catcher, Model V (MOTODA, 1959; OMORI, 1961). This consisted of a head piece with a frontal opening, 7 cm in diameter, and a cylindrical case, 120 cm long and 15 cm in diameter. A filtering net was mounted in the cylindrical case. It was made of bolting silk cloth, GG 54 (0.33 mm mesh openings), and 40 cm long, tapering from 14 cm to 4 cm in diameter. A RGS flow-meter was mounted inside the case at the posterior end. The sampler was towed for 30 minutes at a speed of 7-9 knots behind the ship, at a depth of about 2 meters. The sampler was shot about one hour after sunset while the ship was underway, except in 12 cases in which the * Received Nov . 28, 1964 Contribution No. 41 from the Ocean Research Institute, University of Tokyo ** Ocean Research Institute , University of Tokyo

nihon kaiyo gakkaishi/nihon kaiyou gakkaishi

The Distribution of Zooplankton in the Bering Sea and Northern North Pacific, as Observed by High-Speed Sampling of the Surface Waters, with Special Reference to the Copepods