CCAMLR

For three austral spring and summer field seasons, 1994-97, the Antarctic Site Inventory project has collected data and information about Antarctic Peninsula visitor sites. These data and information are intended to assist in establishing baselines for: future environmental assessments under the soon-to-be-effective Antarctic Environmental Protocol; designing future monitoring programmes to detect changes in fauna, flora, and other major features at these sites; and how best to minimize potential adverse impacts of human visitor activity. CEMP Standard Methods were relied upon in establishing the project's methodology, particularly with respect to counting penguin nests and chicks. At each site, investigators attempt to select and establish prospective control (seldom disturbed) colonies and experimental (frequently disturbed) colonies to census. The intent is to repeat censuses regularly both near and far from landing beaches where visitors access a site, allowing comparisons over time between areas that have much human activity and those without such activity. A power analysis indicates the Inventory's methodology fully conforms with sampling strategies recommended by the CEMP working Group, enabling the Inventory to detect a 10% or 20% change in a parameter with a significance level as. 01 and a statistical power P (= 1-ß) ≥ 0.8.

Data on salp by-catch and green krill were analyzed based on Logbook data of Japanese krill trawlers. Inter-annual and seasonal variability of the timing, duration and strength of salp bloom were indicated. Salp by-catch and occurrence of green krill seemed to show reverse correlation, implying the competition for phytoplankton between krill and salps.

This paper summarizes Japanese krill catch data during austral summer in 1995/96 season. Main fishing grounds were persistently formed in the north of Livingston Island throughout the season. CPUE in December was high but from January through June CPUE was comparable to the value of Livingston area in the previous fishing season. From January through early May, modal size of krill differed between shelf area and slope/outer shelf area. However, from mid-May through late June, no difference in length frequency was observed, and showed only single component with modal size of 47-48mm.

Proportional recruit indices and CPUE in Subarea 48.1 (Antarctic Peninsula region) from 1980 through 1996 were calculated based on the log book data from Japanese commercial krill trawlers. Proportional recruits calculated from fisheries data showed similarity with those from scientific data (Siegel et al., 1997), and showed close relationship to sea ice indices. CPUE (catch/towing volume) in Livingston area showed a decreasing trend during the study period. Alternation of operational strategy in relation to the product quality and decrease of krill density in the areas were considered as the possible reasons. On the other hand, CPUE in Elephant area showed greater inter-annual variation without any trend.

Results from two net surveys in the Elephant Island area during January-March indicated moderate krill abundance and lower recruitment success of the 1995/96 year class relative to that of 1994/95. These occurred after a relatively early 1996 spawning season that theoretically should have promoted good krill recruitment. However winter 1996 was characterized by slightly below average winter 1996 sea-ice conditions. These observations strongly suggest that winter sea-ice extent greatly affects larval survival and recruitment even when krill spawning is relatively early. Salp abundance values during March Survey D were second only to those observed during February-March 1993 and, like 1993, resulted from massive population growth during summer. This bloom, as those in previous "salp years", followed a winter with relatively low sea-ice development. The other zooplankton collected included a diverse taxonomic assemblage. Copepods, salps, and postlarval Thysanoessa macrura were the numerical dominants during both surveys. Day-night catch differences and interspecific relationships among various zooplankton taxa observed during January-February Survey A are described here.

Data from 1995-1997 US Antarctic Marine Living Resources (AMLR) Program surveys in the Elephant Island area are examined to determine the level of sampling effort required to adequately assess the (1) abundance and demographic structure of Antarctic krill and (2) relative abundance and interspecific relations of krill, salps and other macrozooplankton taxa in the Elephant Island area during summer months. Both parametric and nonparametric techniques are used. Between-survey and between-year comparisons are made to examine possible changes in sampling adequacy resulting from ecological changes operating on seasonal and interannual time scales. The results of these analyses indicate that minimal efforts such as 8 station transects are generally unreliable. Results from most analyses indicate that the data from at least 55 stations are required to adequately estimate krill, salp, and other zooplankton abundance, describe krill length-frequency and maturity stage composition, and assess the abundance relations of krill, salps, and other zooplankton taxa in the Elephant Island area.

Exploratory fisheries for Dissostichus spp. have been operating in these regions for a number of consecutive years with the tagging of toothfish a prerequisite for the legal fishery. This paper presents a detailed study of the catch and effort trends in Divisions 58.4.1 and 58.4.2 and examines 4 assessment methods based on comparative CPUE trends, local depletions, a constant recruitment model and mark recapture data.

Detailed review on the food and feeding of Antarctic fish