trawlgen

02jan

<DATE_RANGE> 8 Jan to 26 Jan, 2002

1) Macrozooplankton community abundance and composition from two trawls with different size mouth opening and mesh.

- 1m metro trawl (333 µm nytex mesh) towed obliquely between the surface and 300 m

- 2m metro trawl (~700 µm stretch mesh) towed obliquely between the surface and 120 m

2) Target tows to verify acoustic targets seen on the acoustic trace. - Tucker open/closing trawl for target tows, ~700 um stretch mesh towed at depth of target

Two files are generated from trawling activities.

(1) trawl.list is a record of the trawl information for all trawls (28 variables): event.number, tow.number, Palmer LTER grid.line, Palmer LTER grid.station, GMTtime.begin, GMTtime.end, day(D) or night(N), tow.duration(min), julian.day, date.mm, date.dd, begin.latitude, begin.longitude, end.latitude, end.longitude, tow.heading, ship speed.over.ground(kts), water.depth(m), %cloud.cover, wind.speed (kts), wind.direction, net(1=1meter.square; 2=2meter.square; tucker=open/close; 1mring=1meter ring net), tow.type(std obl=standard oblique, i.e. to standard depth; shal obl=shallow oblique; target=aim.for.aggregation; abort = did not complete; bottom.trawl = hit bottom), net.depth(from depth transducer at point of attachment of net to sea cable), volume.filtered(m3), catch split? Y=yes; N=no, organisms removed: Y=yes; N=no, comments. The meaning of 'organisms removed' depends on whether or not there was a split of the catch. If there was no split, organisms were removed for other purposes (experiments or chemistry for example) so the preserved sample is not a totally random sample; the preserved sample represents the community composition only if the organisms removed are added back into the sample analysis. If the catch was split, often all rare organisms were removed before the split and preservation, for example, fish larvae, ctenophores or tomopterid worms. Sometimes either all krill or all salps were removed before the remaining samples was split. Comments refers to net handling issues.

(2) trawl.catch is a record of the trawl catch composition with quantitative information that varies with the type of trawl and taxonomic group. For 2 m trawls, all euphausiids are identified to species. The most common amphipods and pteropods are identified to genus. Fish larvae are separated into either silverfish larvae (Pleuragramma antarcticum) or other fish larvae. For other taxa, numbers and volumes of groups of species are recorded. Copepods and ostracods are noted, not counted. For 1 m trawls, presence (p) or absence is noted. Sometimes the number and volume of krill, and the volume of salps is also recorded. All fish larvae are removed and counted. The 43 variables are: event.number, tow.number, Palmer LTER grid.line, Palmer LTER grid.station, Net size (1m square; 2m square), Tow type (standard oblique, shallow oblique or target), Tow depth (net depth sensor or ~ =estimated from wire out and wire angle), volume.filtered(m3), Total volume catch (ml), Euphausia superba#, Euphausia superba vol (ml), Thysanoessa sp.#, Thysanoessa sp vol (ml), Euphausia crystallorophias#, Euphausia crystallorophias vol (ml), Euphausia triacantha #, Salpa thompsoni (mature, digestive gland red)#, Salpa thompsoni (mature, digestive gland red) vol (ml), Salpa thompsoni (eleoblast, colorless or yellow)#, Amphipod (non T. gaudichaudii) #, Amphipod (non T. gaudichaudii) vol (ml), Themisto gaudichaudii #, Themisto gaudichaudii vol (ml), Chaetognaths; Pseudosagitta gazellae #, Pseudosagitta gazellae vol (ml), Clione # (includes several species of this genus), Clione vol (ml), Limacina #, Limacina vol (ml), silverfish larvae #, other fish larvae #, Ctenophore #, Ctenophore vol (ml), Siphonophore #, Siphonophore vol (ml), Polychaetes - non Tomopterids #, Polychaetes - non Tomopterids vol (ml), Tomopterid #, Tomopterid vol (ml), Copepods present or absent, Ostracods present or absent ,Split.Factor used to calculate the total from the split for the non-rare taxa Comments (adult fish; decapod larvae)

<DERIVED_VARIABLES> trawl.list & trawl.catch

1) volume filtered (meters cubed) from Oceanics flowmeter readings = Net area * ((flow meter final reading - flow meter initial reading) * (26873/999999))

When data was missing, volume filtered was calculated from the equation for the relationship between tow duration and volume filtered derived from the remainder of the tows for 4 1-m tows, and for 6 2-m tows.

2) With standard stations the Palmer grid line and station given are for the approximate center of the trawl path.

<SAMPLING_FREQUENCY>

Trawling with the 1-m and 2-m trawls was conducted at cardinal stations on 5 cardinal lines (600.*, 500.*, 400.*, 300.* and 200.*). Three of the cardinal line 1-m tows were not conducted due to lack of ship time and/or net repair (200.-040, 200.180, 300.120). The catches for the 2 M nets at 200.020, 200.040 and 200.060 are only semi-quantitative since the net ripped at the surface during retrieval due to the heavy phytoplankton. One 2-m tow at 200.080 was missed due to net repair and lack of time to repeat the station. Selected stations in Marguerite Bay were sampled (200.-020 and 200.-040). One station seaward of the *.200 station was occupied on the 500.* and 600.* lines. Three stations were occupied in the Grandidier/Lemaire region, called ‘inside north’. There were 96 total tows.

(1) trawl specifications:

• the 1-m trawl (1 m2) is a Metro net, with a fixed frame 1-m on a side, and the bridle attachments in the middle of the side pieces of the frame; the mesh size for the net is 333 µm and the codend is 333 µm;

• the 2-m trawl (4 m2) is a Metro net, with a fixed frame 2-m on a side, and the bridle attachments in the middle of the side pieces of the frame; the mesh size for the net is ~ 700 µm and the codend is 500 µm;

• the 2m2 Tucker trawl is an mechanical open/close net with a fixed frame and weighted bottom bar; the mesh size is ~ 700 µm. A General Oceanics double trip mechanism and messengers are used to open and close the net.

(2) protocol for deployment:

• for both the 1-m and 2-m trawls a flow meter (General Oceanics) was attached to the side of the frame so it hangs in the middle of the net opening; snap clips were used for easy removal;

• the metro trawl tows were oblique to a standard depth (1-m 300 m; 2-m 120 m) and back, water depth permitting;

• a depth sensor calibrated to a range of 0-500 m is attached to the end of the sea cable (0.322 conducting wire); the readout on a chart recorder in the laboratory is used to monitor the depth of the trawl; the net is retrieved once it reaches standard depth or is 10- 20 m above the bottom

• all information for the trawl.list for each tow was recorded on a TRAWL RECORD data sheet;

(3) treatment of catch: The TRAWL CATCH LOG for each tow contains the details of the catch processing and disposition of the catch (# and size of preserved jars and preservative (formalin or ethanol), # frozen and size of vial, # into IGR etc).

(a) trawl1m. All fish larvae are removed and immediately preserved in 95-100% ethanol in glass vials. The fish larvae are counted and identified on board if possible. The remainder of the catch is qualitatively characterized and preserved in 10% formalin. Larval E. superba are noted.

(b) trawl2m The goal is to characterize the total catch, i.e., numbers and volumes of each taxa chosen, and to preserve, freeze, or use subsamples of our targeted species (Antarctic krill and salps) for several purposes. The contents of the tub are sorted on board for macrozooplankton and micronekton. All fish larvae are removed and immediately preserved in 95-100% ethanol in glass vials. The fish larvae are counted and identified on board if possible. Numbers and volumes of the taxa listed above are recorded. Either the total catch or a subsample is preserved in 10% formalin. Subsamples of krill and salps are measured, and preserved in 10% formalin or 100% ethanol, or frozen. At selected stations krill are selected for growth and spawning experiments.

<EXPERIMENTAL_DESIGN>

Tows are done at standard stations along the cardinal lines, i.e., the onshore/offshore resolution is 20 km, and alongshore is 100 km. This is the same spatial resolution as for other biological and physical data. The standard depth for tows was set to correspond

• trawl1-m, 300 m is the deepest depth from which larval krill have been collected in this region

• trawl2-m, 120 m is the deepest depth at which krill schools have been observed in this region

Observations and catch processing information, and disposition of catch are recorded on two forms for each event: trawl record, trawl catch log. The information on the trawl record and trawl catch log for each event for the entire cruise is summarized in two files: trawl.list and trawl.catch. Antarctic krill from these catches were used for instantaneous growth experiments, and spawning frequency experiments. About 30-50 krill per transect were frozen in preweighed vials for later determination of wet weight - total length regressions as is usually done.

zooplankton community composition, Southern Ocean, macrozooplankton

<FILE_FORMAT> ascii The first line is the number of columns followed by ! and the study name. Each subsequent line identifies the variable with units. Data follows in comma separated variable format. -999 means no data available; most often noted for water depth in trawl.list, and for zooplankton volumes in trawl.catch when volumes were very small

<STORAGE_LOCATION> ~lter/~lterdata/02jan/trawlgen/* Velella on the MSILTER Apple network

<FILE_NAMES> trawl.list; trawl.catch

<PRINCIPAL_INVESTIGATORS> Robin M. Ross and Langdon B. Quetin, Marine Science Institute, UCSB, Santa Barbara, CA 93106 (805) 893-2096 robin@icess.ucsb.edu or langdon@icess.ucsb.edu

<ASSOCIATE_INVESTIGATORS> none

<CONTACT_PERSON> Robin M. Ross and Langdon B. Quetin Marine Science Institute, UCSB, Santa Barbara, CA 93106 (805) 893-2096 robin@icess.ucsb.edu or langdon@icess.ucsb.edu

<SAMPLES_COLLECTED_BY> RM Ross, C. Boch, K. Johnston, B. Cheng, SA Oakes, M. Caldwell, S. Couture.

<LAB_ANALYSIS_BY> On board sample analysis by above.

<DATA_ENTRY_BY> On board entry by above, in lab entry by RM Ross.

<DATA_ANALYSIS_BY> RM Ross responsible for quality control of data sets.

<SUBMITTED_BY> RM Ross

<DATE_SUBMITTED> 19 October 2004

<DATES_UPDATED>

<SUPPORTING_DOCUMENTS Keys used to identify species: • Kellerman, A. (ed.). 1989. Identification key and catalogue of larval Antarctic fishes. BIOMASS Scientific Series No. 10. • Gon, O., and P.C. Heemstra (eds.). 1990. Fishes of the Southern Ocean. J.L.B. Smith Institute of Ichthyology, Grahamstown, 462 pp. 12 pls. • FAO Southern Ocean identification guides • Makarov, R. Larval development of the antarctic euphausiids. BIOMASS Handbook No. 3. SCAR/SCOR/IABO/ACMRR, Group of specialists on living resources on the southern Oceans. • Mauchline, J. Key for the identificaiton of antarctic euphausiids. BIOMASS Handbook No. 5. SCAR/SCOR/IABO/ACMRR, Group of specialists on living resources on the southern Oceans.

<QUALITY_ASSURANCE> Trawl catch logs for each tow are set up to show the split factor due to subsamples being counted and only subsamples being preserved. Calculations are done on board and checked by a second person as the data are entered. Trawl.list and trawl.catch information have been checked once against original records, and against the event log. Plots of duration of tow against volume filtered in m3 for each net were used to detect outliers in the relationship that usually indicated data entry errors. Those errors were corrected.

<DATA_REQUESTED_BY>

Datafile Form V1.2 for describing a data file.