AMLR 2003 Weekly Report No. 10
1. The R/V Yuhzmorgeologiya is currently in
2. We have completed 17 stations to date in the
eastern, southern, and western sectors of
3. The species composition encountered so far
was similar to those observed during previous surveys. Champsocephalus gunnari and Chaenocephalus aceratus were
either equally or more abundant. Of interest
from an ichthyological point of view were the catch
of some high-Antarctic species, such as Neopagetopsis ionah, Gymnodraco acuticeps or Artedidraco skottsbergi.
Investigations on the reproductive state of the abundant species
indicated that the Chionodraco rastrospinosus,
and mackerel icefish were in the middle of their
spawning season while others, such as Chaenocephalus aceratus and Cryodraco antarcticus were approaching spawning. We were able to collect a large amount of
information on reproduction which we are able to compare with data sampled
during previous surveys. Feeding studies
indicated that species, such as mackerel icefish
preyed heavily on krill. More than 95% of the krill taken was small krill of
age classes 1 and 2.
4. Four combined video/camera transects have been completed this week. The survey design calls for a number of 1 nm transects to be affected across selected depth strata. The data will serve as a method to describe spatial habitat variability within strata and document habitat utilization by fish fauna. The image data will also ground truth the acoustic seabed classification system and provide in situ observation of epibenthic invertebrate fauna. As the camera system is a new experimental design, camera settings and deployment logistics continue to be refined. Our current design incorporates a small (1 m3) frame that houses the digital still camera, sonar altimeter, and flash assembly that is towed from the ship's traction winch. The self-contained video system (video, light, and twin scaling lasers) is flown from a distance of five meters behind the still camera frame. We plan to deploy the video system in the mouth of the trawl later this week.
5. The invertebrate bycatch from the bottom trawl collected from the east and south sides of Elephant Island maintains the pattern observed during the 2001 AMLR bottom trawl survey, with high diversity and biomass, often dominated by sponges, on the east end and lower diversity and biomass to the south side. Reoccupying similar stations as the 2001 survey will offer a good opportunity for interannual comparisons in spatial distributions and ecological relationships. A little benthic invertebrate trawl (“Little BIT”) was attached to the wing sweep of the bottom trawl to collect a more quantitative sample of benthic megafauna for comparison to the bottom trawl bycatch. After an initial deployment of every second trawl, a protocol for processing the abundant and taxonomically complex benthos was established so that every trawl could be deployed with a Little BIT on the side. The samples of the benthos using the Little BIT indicate a very different sampling capability from the fish trawl. In some cases, only a single specimen of a given invertebrate taxon is represented in the bottom trawl, yet in the Little BIT, it was represented by several hundred specimens and has come close to being the dominant taxon in the sample. In other cases, sponges were easily collected, but urchins and brittle stars were largely absent from the fish trawl. Though it is possible that these smaller organisms are washed through the larger mesh fish trawl, it is more likely that they are low enough to the bottom that they are not picked up at all as the net rolls over them. Thus, the Little BIT appears to be a useful tool by which to assess the impact of the bottom trawl on the benthic invertebrate community. The usefulness of this sampling tool will continue to be explored for the duration of the Leg.
6. Blood and tissues samples were collected from
representative specimens from all notothenoiod
species to assess the levels of blood antifreeze proteins and number of
antifreeze genes in their genome. The presence
of the high latitude Antarctic Trematomus and chaenicthyiid species
in the warmer waters of the
7. Three aspects of notothenioid biology have been investigated: the phylogenetic relationships of notothenioids using DNA sequences from both mitochondrial and nuclear genes, the evolution of buoyancy among notothenioid species, and ecomorphological studies that are attempting to relate morphological differences between closely related species with documented ecological variation (i.e., diet). After four days of sampling the species available for molecular phylogenetic study has increased by three, including a previously unsampled family. Buoyancy data collected over the past week has led to a discovery of the heaviest notothenioid recorded to date, Harpagifer antarcticus. Mouth gape width and the degree of upper jaw protrusion have been collected as ecomorphological data on a total of 21 notothenioid species.
C. Jones sends