Brief description
Samples were collected at trawl stations (approximately every second CTD station), as well as opportunistically when something interesting was spotted on the Echosounder. The samples were collected with an RMT-1 plankton net and preserved in Steedman's solution. Upon returning to Australia, the samples were passed onto Kerrie Swadling, who split them with a Folsom plankton splitter and counted between 400 and 1300 animals. Every organism was identified to the lowest possible taxon - in the case of copepods, usually to species and stage level. Other taxa are to species wherever possible. All the animals were counted and the results are expressed as abundance per 1000 cubic m. The data in the spreadsheet represent a species x site matrix.The excel spreadsheet entitled 'List of major samples and activities BROKE West.xls' is a summary of the sort of samples that were collected at each station, and the purpose for which they were collected.
More detailed notes about the collection of the samples are presented in the Quality field.
Further information about the Trawl stations can be found in the parent BROKE-West metadata record.
This work was completed as part of ASAC projects 2655 and 2679 (ASAC_2655, ASAC_2679).
The fields in these excel spreadsheets are:
Station Number
Species
Date
Latitude
Longitude
Trawl Type
Formalin - whether the samples were fixed in formalin
IGR - whether the instantaneous growth rate experiment was performed
Genetics - preserved in ethanol, samples retained for genetic experiments
Frozen - samples frozen at -85 degrees C for chemical analysis
POP - samples analysed for Persistent Organic Pollutants
Density Contrast - whether the density contrast of the krill were measured
Isotopes - samples retained for isotope analysis
Frozen DG - digestive gland samples were frozen
Ethanol (Squid) - ethanol fixed squid were retained
Frozen (Fish) - frozen fish samples were retained
Formalin (Fish) - formalin fixed fish samples were retained
Ethanol (Fish) - ethanol fixed fish samples were retained
Demography - demographic parameters were collected
Other - various purposes, occasionally noted in the comments field
Comments
The spreadsheet 'List of major samples and activities BROKE West.xls' is marked with solid black circles, or empty white circles - the empty white circles represent Euphausia crystallorophias samples. The solid black circles represent Euphausia superba in columns F-K, M and R. In the other columns they will either represent the animal as marked (eg squid), or may be a collection of anything.
Lineage
Progress Code: completed
Statement: Krill/Zooplankton/Fish: Net Sampling
Regular trawl stations were laid out approximately every second CTD stations. Target trawls were undertaken whenever any target of interest were detected on the echosounder. Single opening-closing RMT 1+8 net (Baker et al., 1973) with CTD System installed was used for all of the tows (Regular and Target), Hard cod-ends were used for all the trawls. Flow meters were used to estimate the volume of water towed. Table 1 summarises the details of RMT stations. Ringnet deployments were undertaken at almost every CTD stations.
Regular Trawl
At each regular trawl station a quantitative standard double oblique tow was conducted from the surface down to 200 m (or to within 10 m of the bottom at stations shallower than 200 m). Such a depth range is considered to be the best compromise between the time available for sampling and the likely vertical depth range of krill. During the hauls, ship's speed was maintained constant at 2.5 plus or minus 0.5 knots. Wire speed of 0.7 to 0.8 m/s during paying out and of 0.3 m/sec during hauling(approx. 0.5 m/s and 0.2 m/s respectively at vertical depth change rate). The net mouth angle is remarkably constant during hauling within the speed ranges given above. When the net reaches maximum depth, the winch was stopped for about 30 seconds to allow the net to stabilise before retrieving. When hauling, the propeller thrust was turned off when the net reached depth of 15 to 20 m; this was to minimise the effects of the propeller action on the net operation and avoid damage of the samples.
Target Trawl
Whenever interesting targets were seen on the echo-sounder, or large amount of krill was required for any purpose, target trawls were performed. Once the position of the target was marked, the ship was turned and navigated to run over the target from direction required within navigation capacity. The ship speed was reduced to below 2.0 knots before hitting the target, so that the net could be lowered down to the desired depth when the net reached the target. Fine adjustments were made throughout the trawl by monitoring the echo-sounder in the aft control room. For live krill target trawl, ship speed was kept as slow as possible to avoid any damage to krill.
Laboratory Sampling and Processing
Sample processing for all regular trawl stations:
RMT-8
Measure the total sample volume (Drain water, then measure using water replacement; mandatory only for the regular hauls).
Sort out all Antarctic krill and count their number. If the sample mainly consists of krill and the volume is more than ~1L, a known portion of the whole sample was sub-sampled for the further processing.
Stage (TL, Carapace Length, Maturity) of all krill (or subsample), up to 50 to 150 individuals, and DG size (the longest axis) of up to 50 individuals were measured using digital calipers.
Other zooplankton groups were immediately sorted out from the catch and their numbers were recorded.
Preservation of RMT-8 samples
Krill (including those used for onboard demography measurements) were fixed in 10% formalin for their further analysis. Whenever excess amount of krill were caught, they were sampled and frozen for POP (persistent organic pollutant) measurements, preserved in 80% ethanol for genetic analysis, and frozen under -80C/ liquid nitrogen for chemical analysis. Fish were preserved in formalin, EtOH, or frozen. Squids were preserved in EtOH.
RMT-1
The whole sample was fixed with 10 % formalin.
If the sample volume was too large, then a known proportion of catch was randomly sub-sampled and fixed.
Regular trawl stations were laid out approximately every second CTD stations. Target trawls were undertaken whenever any target of interest were detected on the echosounder. Single opening-closing RMT 1+8 net (Baker et al., 1973) with CTD System installed was used for all of the tows (Regular and Target), Hard cod-ends were used for all the trawls. Flow meters were used to estimate the volume of water towed. Table 1 summarises the details of RMT stations. Ringnet deployments were undertaken at almost every CTD stations.
Regular Trawl
At each regular trawl station a quantitative standard double oblique tow was conducted from the surface down to 200 m (or to within 10 m of the bottom at stations shallower than 200 m). Such a depth range is considered to be the best compromise between the time available for sampling and the likely vertical depth range of krill. During the hauls, ship's speed was maintained constant at 2.5 plus or minus 0.5 knots. Wire speed of 0.7 to 0.8 m/s during paying out and of 0.3 m/sec during hauling(approx. 0.5 m/s and 0.2 m/s respectively at vertical depth change rate). The net mouth angle is remarkably constant during hauling within the speed ranges given above. When the net reaches maximum depth, the winch was stopped for about 30 seconds to allow the net to stabilise before retrieving. When hauling, the propeller thrust was turned off when the net reached depth of 15 to 20 m; this was to minimise the effects of the propeller action on the net operation and avoid damage of the samples.
Target Trawl
Whenever interesting targets were seen on the echo-sounder, or large amount of krill was required for any purpose, target trawls were performed. Once the position of the target was marked, the ship was turned and navigated to run over the target from direction required within navigation capacity. The ship speed was reduced to below 2.0 knots before hitting the target, so that the net could be lowered down to the desired depth when the net reached the target. Fine adjustments were made throughout the trawl by monitoring the echo-sounder in the aft control room. For live krill target trawl, ship speed was kept as slow as possible to avoid any damage to krill.
Laboratory Sampling and Processing
Sample processing for all regular trawl stations:
RMT-8
Measure the total sample volume (Drain water, then measure using water replacement; mandatory only for the regular hauls).
Sort out all Antarctic krill and count their number. If the sample mainly consists of krill and the volume is more than ~1L, a known portion of the whole sample was sub-sampled for the further processing.
Stage (TL, Carapace Length, Maturity) of all krill (or subsample), up to 50 to 150 individuals, and DG size (the longest axis) of up to 50 individuals were measured using digital calipers.
Other zooplankton groups were immediately sorted out from the catch and their numbers were recorded.
Preservation of RMT-8 samples
Krill (including those used for onboard demography measurements) were fixed in 10% formalin for their further analysis. Whenever excess amount of krill were caught, they were sampled and frozen for POP (persistent organic pollutant) measurements, preserved in 80% ethanol for genetic analysis, and frozen under -80C/ liquid nitrogen for chemical analysis. Fish were preserved in formalin, EtOH, or frozen. Squids were preserved in EtOH.
RMT-1
The whole sample was fixed with 10 % formalin.
If the sample volume was too large, then a known proportion of catch was randomly sub-sampled and fixed.
Data time period: 2006-01-17 to 2006-03-03
text: westlimit=29.92; southlimit=-69.21; eastlimit=80.02; northlimit=-61.66
text: uplimit=200; downlimit=0
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