CCAMLR

Aim of this document is to supply a short information of chlorophyll distribution patterns around the South Shetland Islands in the Antarctic survey of R/V the Kaiyo Maru from 13 December 1990 to 11 January 1991 (Leg I) and from 16 January to 11 February 1991 (Leg II). In the north of Livingston Island, high chlorophyll a concentration and low POC/chlorophyll a ratio in Leg II and low chlorophyll a concentration in Leg I suggest that phytoplankton bloom occurred in this area for about one month.

This document submits the basic information on the hydrographic flux in Statistical Area 58. Those are surface geostrophic flow in the whole of Statistical Area 58, and vertical distributions of geostrophic flow along 37° E, 75° E,114° E and 155° E.

A theoretical prolate spheroid liquid model is applied to predict the target strength (TS) of krill. Scattering patterns are shown to demonstrate orientation dependence of krill TS. Length-to- wavelength ratio (L/λ) dependencies of reduced (normalized by body length squared) target strength are shown for some orientation distributions. The results can explain well-organized experimental results. The variability of the TS of krill is large where L/λ is larger than unity. Therefore, a frequency around 70 kHz is superior to 120 kHz which are ordinarily used for krill surveys.

Data from the Eduardo L Holmberg FIBEX survey have been re-examined for incorporation into the BIOMASS Database in the approved standardised format. The results indicate the krill were concentrated to the western end of the South Orkney Islands. Density values are consistent with those from other FIBEX surveys.

A numerical model is being developed for assessment of Euphausia superba in Antarctic Ocean, which consists of:
(1)calculation of three dimensional current field using CCSR version (developed by Dr. Yamanaka of Center of Climate System Research, University of Tokyo) of the three dimensional primitive equation for the ocean circulation developed originally at the GFDL, Princeton, NJ,
(2)calculation of spatial distribution of DIN (Dissolved Inorganic Nitrogen)
(3)calculation of spatial distribution of DON (Dissolved Organic Nitrogen),
(4)calculation of spatial distribution of Chl.a and
(5)calculation of spatial distributiion of Euphausia superba.
Our model will be capable of calculating the detailed spatial distribution of Euphausia superba by dividing the Antarctic Ocean into many grid points. It also takes into consideration the effects of fisheris.

Biogenic silica (BSi), lithogenic silica (LSi), particulate organic carbon (POC) and nitrogen (PON), and chlorophyll a (Chl a) were measured in the surface waters (

Distribution and abundance of salps were studied near the South Shetland Islands during summer 1990/1991. Total salp biomass ranged between 0.1 and 2021.3 mg WW∙m-3 and was nearly equal to krill biomass in the area. Two species; Salpa thompsoni and Ihlea racovitzai were found, and the former was dominant. Horizontal distribution of salps and krill did not overlap. Krill occurred abundantly at the high-chlorophyll a area, in contrast, salps exhibited high biomass in the area of low chlorophyll a concentration

Food habits of the southern baleen whales were reviewed being based on the published and unpublished data since 1946. Past geographical distributions of the krill in the whales stomach revealed that the frequency occurrence by krill size showed that the large krill(>50mm) occurs more frequently in the whaling Areas II and III, then the size comes medium (40-50mm) in the Areas IV and V, and finally small krill (

A simple deterministic model is described which models the behaviour of the krill fishery in Subarea 48.1 and estimates the effort applied and the catch of krill in fine-scale squares. Parameters for the model are calculated from data reported to CCAMLR by Chile over the period 1989 to 1992. The distribution of catches predicted by the model, which is restricted to the months December to March, compare favourably with the general distribution of catches in Subarea 48.1. A number of management scenarios are considered, which involve closures (i) of a zone 50 km offshore from the South Shetland Islands, and (ii) of zones 100 km around Livingston and Elephant Islands. The model predicts that the management option of closing the zones around Livingston and Elephant Islands in alternate years would result in an average yearly catch similar to that at present, although the catch is much more concentrated in foraging areas of land-based predators in alternate years under this scenario.