zodtrawl 9192Pal 19dec91-28feb92 Zooplankton and fish diversity and abundance from net tows. Zodiac trawls were conducted in the immediate Palmer area. The objective of the standard tows at specified stations was to assess macrozooplankton and fish diversity and abundance throughout the season, whereas targetted tows were to collect krill for laboratory experiments. file zodtrwl*.rec: Event number, tow number, location, time begin, time end, time of day, fishing duration, tow direction, ship speed, water depth, cloud cover, sea condition, gear used, tow type, acoustic signal depth, acoustic signal strength, wire out, catch split?, number of krill, number of fish, tow disposition file zodtrwl*.dat: Station on Palmer grid (A-J), event number, date, day or night, number of individuals in the following categories: Euphausia superba juvenile through adult, Euphausia superba calyptopis, Thysanoessa macrura larvae, Thysanoessa macrura juveniles and adults, Calanoides acutus, Calanus propinquus, small C. acutus and C. propinquus (grouped), Rhincalanus gigas, Metridia gerlachei, harpacticoids and cyclopoids, miscellaneous small copepods, miscellaneous amphipods, small white amphipods, ostracods, pilidium larvae of nemerteans, advanced nemertean larvae, barnacle nauplii, brachiolaria (Echinodermata, Asteroidea), holothuroid larvae, chaetognaths, pteropods, pteropod egg cases, mollusc eggs, siphonophores, medusae, polychaetes, "mystery critter 1", fish larvae Each transect, i.e. A through E, and F through G was sampled weekly, with two standard tows per transect for zooplankton, plus targetted tows if krill were seen on the fish finder. Standard tows for zooplankton were between stations A and B, D and E, F and G, and I and J. On several dates both day and night tows were performed. Twice, we sampled zooplankton at night near the Wauwerman Islands (Stations K-O). On 2/12/92 we sampled zooplankton from the Erebus, listed as stations 1*, 2* and 4*. Latitude and longitude of these sites is listed in zodtrwl*.rec. From mid-December until mid-January otter trawls were done between each pair of stations on the two transects for a total of 4 otter trawls per transect per week, but this decreased to 2 stations per transect after mid-January. zodtrwl*.rec Nets were hauled by hand from a Mark V zodiac. Standard headings and depths were used to gauge accurate positioning after identification of headings and deptsh on the zodiac equipped with a GPS system. For all standard zooplankton tows, a 1-m diameter, 500-um mesh ring net was deployed. To survey for larger krill and fish, a 16-ft otter trawl was used. For targetted tows, either a 500-um 3-mm ring net dyed blue, or the 16-ft otter trawl was used (see zodtrwl*.rec). Four tow types exist: oblique, stepped, targetted and neuston. For an oblique tow, the line was let out at a slow, steady rate until the required length was reached, and then the net was pulled steadily in as quickly as possible. For a stepped tow, line was let out to 50 m, 100 m, and 150 m. The net was held at each of these intervals for two minutes, and then rapidly lowered to the next level. After the 150 m step, the line was pulled steadily back in. A targetted tow was performed when a krill school was detected. The zodiac was turned 180 degrees, in order to backtrack over the detected school, and enough line was let quickly out to place the net midway through the school, based on an approximate 3:1 line:depth ratio. After 2-5 minutes, the net was quickly retrieved. For a neuston tow, 5-10 m of wire was let out, and the net was kept at the surface. Wire angle was approximately equal for all tows. Once the cod end was retrieved, krill to be used for live experiments were placed in several seawater-filled buckets or coolers, keeping densities as low as possible. Zooplankton samples (from standard surveys) were kept in a covered bucket and preserved back on station: these samples were poured carefully through a 300-um mesh sieve, and the sieve contents rinsed with seawater into a small (2-4 oz) jar. Buffered formalin was then added for a final concentration of 10% formalin in seawater. zodtrwl*.dat Zooplankton samples were examined with a dissecting microscope. The entire sample was examined and counted, and identified specimens recorded. Individuals of each particular taxon were separated into their own small vials. Unidentified specimens were placed in their own vials. Dominant copepods were identified to adults of species, with larvae grouped. Euphausids were identified to species, and adults vs. larvae. Amphipods, ostracods and pteropods were identified to order. Nemerteans and chaetognaths were identified to phylum, and nemerteans further grouped into early and late larval stages. Echinoderm larvae were identified to class. Mollusc eggs were identified to phylum, except pteropod eggs were identified to order. Cnidarians were identified by general body form: "siphonophore" or "medusa". One odd medusa-like form was identified as "Mystery Critter 1" (possible larval ctenophore). Polychaetes were identified to class. Fish larvae were identified to species. Stations were chosen for standard tows based on their position on the transect line. We chose locations near each end of each transect line to capture the diversity within the near Palmer grid over space and time. Stepped tows were conducted for surveys because it seemed to be the most methodical way to fish, given the limitations of our hand-trawling method. palmer lter, zodiac trawling nearshore, zooplankton, krill ascii data3/lterdata/9192pal/zodtrwl/zodtrwl*.rec data3/lterdata/9192pal/zodtrwl/zodtrwl*.dat Only samples from station I have been counted as of 11/93. zodtrwl*.rec zodtrwlI.dat Robin M. Ross, Langdon B. Quetin Robin M. Ross Robin M. Ross, Tim Newberger, Karen Haberman Karen Haberman (standard zooplankton tows) Karen Haberman Karen Haberman (standard zooplankton tows) Robin M. Ross 28 Apr 1992 20 May 1992 22 Nov 1993 Dr. Mai Lopez (type specimens for copepods); Kellerman, A. ed., 1989. "Identification Key and Catalogue of Larval Antarctic Fishes." BIOMASS Scientific Series No. 10, 136 pages; Makarov, R., "Larval Development of the Antarctic euphausiids." BIOMASS Handbook No. 3, 13 pages; Mauchline, J. "Key for the Identification of Antarctic euphausiids." BIOMASS Handbook No. 5, 4 pages; Waters, K. J. and R. C. Smith, 1992. "Palmer LTER: A Sampling Grid for the Palmer LTER Program." Antarctic Journal of the United States 1992. Individuals keyed to species were carefully examined for identifying characteristics. The practice of removing each counted specimen and placing it in a separate vial minimized counting errors. No attempt was made to classify specimens for which we had no keys, beyond basic taxanomic categories with which the sorter/counter was familiar. Since specimens were separated and stored according to the categories used, these can be further sorted at a later time if desired, with the use of appropriate keys. Core measurments available after two years. Citation acknowledgement: "Data from the Palmer LTER data archive were supported by Office of Polar Programs, NSF (OPP-9011927)."

Datafile Form V1.3 for describing a data file.