AMLR 2006 Weekly Report No. 7
1. The R/V Yuhzmorgeologiya is currently about 30 nautical miles north of the Antarctic Peninsula’s Joinville Island, conducting a bottom trawl survey of demersal finfish biomass, composition, distribution, and demographics. Other activities include additional finfish research, characterization of benthic invertebrate megafauna, acoustic sampling of pelagic krill abundance, and seabed habitat characterization of shelf areas along the Trinity Peninsula and Joinville/ D’Urville Island regions of the Antarctic Peninsula.
2. We have successfully completed 24 stations to
date using a random depth stratified sampling design. One station was invalidated due to gear loss. As of 26 February, a total of 754 Kg of
finfish (3387 individuals) of 37 species have been captured and processed. Our greatest combined yields of finfish have
occurred at stations north of
3. Finfish species with the greatest biomass and
numbers thus far has been Gobionotothen gibberifrons and Trematomus newnesi.
The overall finfish species composition encountered thus far
demonstrates a considerable contrast relative to previous AMLR surveys
conducted along the
4. The benthic invertebrate bycatch
composition of all 24 successful hauls have been analysed
in terms of abundance and biomass of 47 taxonomic groupings. Total bycatch biomass has been extremely high ~50% requiring subsampling each weighing over 1 metric ton. This was so
particularly along the shelf of the
5. A total of 120 specimens sampled from 28 notothenioid finfish species have been sampled for buoyancy, gape width, jaw protrusion, and genetic analyses. Three fairly rare notothenioid species are included in this sample. One of these species, Aethotaxis mitopteryx, has never been collected in an AMLR fish survey. Also, A. mitopteryx has been suspected as a neutrally buoyant species, but has never been measured. We were able to measure buoyancy in two specimens and both were neutrally buoyant. This is a significant result that will have broad interest among biologists studying notothenioid fishes.
6. Tissue samples have been taken from 130 fish
specimens representing 28 notothenioid species. Tissues sampled included muscle, heart
ventricle, spleen, and testis. The fish
were preserved in formalin as voucher specimens for the
7. Acoustical data are continually being taken for krill abundance and also bottom typing. Initial acoustical krill abundance ranged from 0.097 to 80.3 g/m2. A few dense patches of krill were observed during trawl transects contributing to large abundances. Average acoustic transects for trawls were 4 nautical miles. Bottom typing data are still being analyzed. Bottom depths are being used to create an in situ bathymetric chart used in finding locations suitable for trawling.
8. Antarctic fur seal scat is being processed onboard for hard parts of dietary components, and lipids are being isolated from milk samples. To date, 27 scats have been processed. Of the 27 scats processed: all contained krill; seven contained one or more otoliths; two contained squid beaks. Remaining work includes processing 3 additional scat samples; identifying, sorting, and fully labeling all otoliths; and processing all milk samples (22 in total).
9. A total of 18 CTDs from a possible 24 stations were successfully completed, with the western station showing mainly Water Zone 4 (Bransfield Strait) waters and the stations north of the Antarctic Sound/ Joinville Island area having Water Zone 5 (Weddell Sea) influence.
10. Predominantly overcast skies with periods of
rain and fog saw air temperatures ranging between 0 and 4.5°C (average around
2°C) during the week, with only short periods of sunshine. Gradual barometer
increase from 985 to 1017 millibars produced a
C. Jones sends.