Data to support Two scales of distribution and biomass of Antarctic krill (Euphausia superba) in the eastern sector of the CCAMLR Division 58.4.2 (55°E to 80°E)

This data may be used to reproduce the analyses (including figures and tables), of 'Two scales of distribution and biomass of Antarctic krill (Euphausia superba) in the eastern sector of the CCAMLR Division 58.4.2 (55°E to 80°E)'.

The data describe krill biomass density distribution and krill net samples (krill total length and krill wetmass) collected during the 2021 TEMPO voyage on R/V Investigator.

During the TEMPO voyage krill biomass was estimated using observations from two sampling instruments: a calibrated EK80 scientific echosounder operating at 120 kHz and an rectangular midwater trawl (RMT 1+8). The supporting data sets, all in CSV format, are split by instrument type.

The EK80 has two datafiles:

1. krill_density.csv – krill areal density from the TEMPO transects, and
2. krill_swarms.csv -krill swarms detected during the TEMPO transects.

The RMT1+8 has four datafiles

1. net_locations.csv
2. krill_lengths.csv
3. krill_wet_mass_to_length.csv
4. krill_wet_mass_to_length_model_predictions.csv

The fields (columns) in each data file are:

krill_density.csv
"lat_M" – centre latitude of an echo integration interval [degrees] (dd.ddddd) WGS84 spheroid (GPS latitude)
"lon_M" - centre longitude of an echo integration interval [degrees] (dd.ddddd) WGS84 spheroid (GPS longitude),
"areal_biomass_density_g_per_m2" – Echo integration interval krill areal biomass density [g wet-mass / m^2]
"daynight" – flag for when the sampling took place [day/night]
"survey" – Either the main survey for the TEMPO biomass survey or the smaller-scale ‘Mawson box’ survey

krill_swarms.csv
"transect" – transect number
"lat" – latitude [degrees] (dd.ddddd) WGS84 spheroid (GPS latitude)
"swarm_depth_m" – mean depth of a krill swarm [m]
"daynight" – flag for when the sampling took place [day/night]
”volumetric_density_g_per_m3" – krill swarm internal volumetric biomass density [g wet-mass / m^3]

net_locations.csv
"station" – Station name for net trawl R for routine haul, T for target trawl
"lat" – mean latitude of a net trawl [degrees] (dd.ddddd) WGS84 spheroid (GPS latitude)
"lon" – mean longitude of a net trawl [degrees] (dd.ddddd) WGS84 spheroid (GPS longitude)
"daynight" – flag for when the sampling took place [day/night]

krill_lengths.csv
"station" – Station name for net trawl R for routine haul, T for target trawl
"total_length_mm” – total length of an individual krill [mm]

krill_wet_mass_to_length.csv
"total_length_mm" – total length of an individual krill [mm]
"wet_mass_g" - wet-mass an individual krill [g]

krill_wet_mass_to_length_model_predictions.csv
"total_length_mm" - total length of an individual krill [mm]
"predicted_wet_mass_g" – predicted mean wet-mass an individual krill of length ("total_length_mm" ) [g]
"LB_wet_mass_g" – Lower bound (lower 95% confidence interval) for the predicted_wet_mass_g [g]
"UB_wet_mass_g"– Upper bound (upper 95% confidence interval) for the predicted_wet_mass_g [g]

本数据集可用于复现《南极磷虾（Antarctic krill，*Euphausia superba*）在南极海洋生物资源养护委员会（Commission for the Conservation of Antarctic Marine Living Resources, CCAMLR）第58.4.2分区东部海域（55°E至80°E）的分布与生物量的两类尺度研究》中的全部分析结果（含图表）。

本数据集记录了2021年TEMPO航次在‘调查者号’（R/V Investigator）科考船上采集的磷虾生物量密度分布数据，以及磷虾网采样本数据（含磷虾总长度与湿重信息）。

本次TEMPO航次中，科研人员采用两种采样设备开展观测以估算磷虾生物量：一是经过校准的120 kHz科学回声测深仪EK80，二是矩形中层拖网（RMT 1+8）。所有辅助数据集均采用CSV格式，并按采样设备类型进行分类存储。

EK80对应2个数据文件：
1. `krill_density.csv`：TEMPO航次断面调查得到的磷虾面密度数据；
2. `krill_swarms.csv`：TEMPO航次断面调查中探测到的磷虾群数据。

RMT 1+8对应4个数据文件：
1. `net_locations.csv`：网拖站位数据；
2. `krill_lengths.csv`：磷虾体长数据；
3. `krill_wet_mass_to_length.csv`：磷虾湿重-体长对应数据；
4. `krill_wet_mass_to_length_model_predictions.csv`：磷虾湿重-体长模型预测数据。

### krill_density.csv 字段说明：
`lat_M`：回声积分区间的中心纬度，单位为度（格式为dd.ddddd），采用WGS84椭球体基准（GPS纬度）
`lon_M`：回声积分区间的中心经度，单位为度（格式为dd.ddddd），采用WGS84椭球体基准（GPS经度）
`areal_biomass_density_g_per_m2`：回声积分区间内的磷虾面生物量密度，单位为克湿重/平方米（g wet-mass / m²）
`daynight`：采样时段标识，取值为‘day’（白天）或‘night’（夜间）
`survey`：调查类型，包括TEMPO生物量主调查，或小规模‘莫森区块’（Mawson box）调查

### krill_swarms.csv 字段说明：
`transect`：断面编号
`lat`：纬度，单位为度（格式为dd.ddddd），采用WGS84椭球体基准（GPS纬度）
`swarm_depth_m`：磷虾群的平均深度，单位为米（m）
`daynight`：采样时段标识，取值为‘day’（白天）或‘night’（夜间）
`volumetric_density_g_per_m3`：磷虾群内部的体积生物量密度，单位为克湿重/立方米（g wet-mass / m³）

### net_locations.csv 字段说明：
`station`：网拖站位名称，‘R’代表常规拖网，‘T’代表目标拖网
`lat`：网拖作业的平均纬度，单位为度（格式为dd.ddddd），采用WGS84椭球体基准（GPS纬度）
`lon`：网拖作业的平均经度，单位为度（格式为dd.ddddd），采用WGS84椭球体基准（GPS经度）
`daynight`：采样时段标识，取值为‘day’（白天）或‘night’（夜间）

### krill_lengths.csv 字段说明：
`station`：网拖站位名称，‘R’代表常规拖网，‘T’代表目标拖网
`total_length_mm`：单只磷虾的总长度，单位为毫米（mm）

### krill_wet_mass_to_length.csv 字段说明：
`total_length_mm`：单只磷虾的总长度，单位为毫米（mm）
`wet_mass_g`：单只磷虾的湿重，单位为克（g）

### krill_wet_mass_to_length_model_predictions.csv 字段说明：
`total_length_mm`：单只磷虾的总长度，单位为毫米（mm）
`predicted_wet_mass_g`：对应体长（`total_length_mm`）的单只磷虾预测平均湿重，单位为克（g）
`LB_wet_mass_g`：预测湿重的95%置信区间下限，单位为克（g）
`UB_wet_mass_g`：预测湿重的95%置信区间上限，单位为克（g）