. Commercial fisheries review. Fisheries; Fish trade. 50 WET WEIGHT IN GRAMS 170* 175' laO' 175° 170° ^5° ::y r^ < ALASKA 1 1} \ Li '\. . v £ââ â '. Fig. 3 - Vertical distribution of biomass at 25-m. depth intervals at three stations, during the day and at i catches in a 3-foot Isaacs-Kidd midwater trawl. ight, as deter ed by the narrow spacing of circuli on the scales suggests little growth. The narrow spacing during winter is significant. It permits us to ascertain the age of the salmon by counting year-marks, which are analogous to the rings in a cross-section of a tree trunk (fig. 4
. Commercial fisheries review. Fisheries; Fish trade. 50 WET WEIGHT IN GRAMS 170* 175' laO' 175° 170° ^5° ::y r^ < ALASKA 1 1} \ Li '\. . v £ââ â '. Fig. 3 - Vertical distribution of biomass at 25-m. depth intervals at three stations, during the day and at i catches in a 3-foot Isaacs-Kidd midwater trawl. ight, as deter ed by the narrow spacing of circuli on the scales suggests little growth. The narrow spacing during winter is significant. It permits us to ascertain the age of the salmon by counting year-marks, which are analogous to the rings in a cross-section of a tree trunk (fig. 4). Study Biomasses of Environmental Waters We are completing biological studies along a line of stations south of Adak Island to as- certain if the various environmental waters, such as the Alaskan Stream and the Subarctic Current, and the Ridge Area which separates these two systems, have characteristic bio- masses. It appears that the phytoplankton bloom is greatest inshore in early spring-- but that the standing stock of zooplankton is greatest in the Ridge Area. This has been interpreted to mean that grazing by large numbers of zooplankton in offshore areas prevents the standing stock of phytoplankton (as indicated by the nutrients) to attain its immense potential. Extensive grazing in turn seriously restricts the potential plankton pro- duction in the Subarctic Region. Further estimates of potential primary production are being made on the basis of cloud cover data obtained from ESSA satellite photographs. Monthly averages of daily cloud cover indicate that previous estimates based upon sporadic ship reports are not represen- tative; thus values of incident radiation, cor- rected for shielding by clouds, are in error. Production of phytoplankton is directly re- lated to incident radiation. Even though zoo- plankton cropping may exist, knowledge of areas of minimum cloud cover in spring could possibly denote areas of high primary pro- duction and, therefore, poss
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