Cruise Report Cruise no. 0332
Joint investigations on the environment and pelagic fish in the Faroese area and in the Norwegian Sea
30. April - 28. May 2003 R/V Magnus Heinason OW2252
Jan Arge Jacobsen Leon Smith
Eilif Gaard Mourits Mohr Joensen
Faroese Fisheries Laboratory - POBox 3051 - FO 110 Tórshavn, Faroe Islands
INTRODUCTION
The main aims of this survey was to investigate the distribution and abundance of postspawning blue whiting in the Faroese area and to investigate the distribution and stock size of Norwegian spring spawning herring in the Faroese area and the Norwegian Sea. Hydrographic data were collected along the cruise tracks and along the Faroese standard section North (north along 6°W north of the Faroes). Plankton samples were taken at each hydrographic station.
The cruise was part of an joint international survey (Faroes, Norway, Iceland and EU, EU did not participate in 2002-2003) coordinated by the ICES Planning Group on Surveys on Pelagic Fish in the Norwegian Sea (PGSPFN). Cooperating vessel during this investigation was R/V G.O. Sars from Norway. Data from both vessels will be incorporated in a comprehensive report from PGSPFN covering research surveys in the Norwegian Sea during the summer 2003 (ICES CM 2003/D:06).
This report is based only on data from the Magnus Heinason, and therefore no estimate of herring is given due to incomplete coverage in the Norwegian Sea.
MATERIAL AND METHODS
The area was covered from south to north. The first part of the survey (30/4-12/5) covered the blue whiting concentrations in the southern part of the Faroese area. The second part of the survey (13- 28/5) covered blue whiting in the eastern and northern part of the Faroese area and in the
Norwegian Sea (Fig. 1).
Cruise tracks with hydrographic stations (CTD), plankton stations (WP2 net 0-200m), and trawl stations in the Faroese area are shown in Fig. 1. Acoustic data were recorded with a Simrad EK-500 echo sounder. Data from the hull mounted 38 kHz transducer were logged at sea and used in the fish abundance estimation. The area backscattering recordings (sA) per nautical mile were averaged by each 5 nautical mile and the recordings were and scrutinised on a daily basis and allocated to either blue whiting, herring, plankton or other fish (e.g. lantern fish).
The 38 kHz Echo sounder was operating with the following settings, as obtained from a copper sphere calibration prior to the survey:
Max. Power 2000 W
Time varied gain 20 log R
Pulse length Medium
Bandwidth Wide Angle sensitivity 21.9 dB 2-way beam angle -20.6 dB Sv transducer gain 27.12 dB TS transducer gain 27.29 dB 3 dB beam width 6.9/7.1 dg Along ship offset 0.26 dg Athw. ship offset -0.07 dg
For zooplankton sampling a standard WP-2 net with 180 µm meshes was used for vertical hauls 0- 200m.
A CTD was used to record temperature and conductivity (salinity) down to 1000 m depth or to the bottom. Water samples were taken from each station, with water bottles mounted on the CTD, for analysis of nutrients. Samples for chlorophyll were collected from the upper 100m. CTD and WP-2
stations were taken every 10-20 nm in the southern part of the Faroese area and every 25-30 nm in the northern part of the area and in the Norwegian Sea.
RESULTS
The average sA values of blue whiting by statistical square from the Magnus Heinason survey are shown in Fig 2. In the southern part of the Faroese EEZ the highest concentrations of post spawning blue whiting were recorded along the eastern edge of the Faroe bank and on the Monk
("Munkagrunnurin"). In the northern area blue whiting was observed in most of the Norwegian Sea except in the northernmost stations, where the influence of the cold East-Icelandic current had its influence (Fig. 2). The length and weight distributions of blue whiting in the Faroese area is shown in Fig. 4 and 5, respectively. In the southern area the 2002 and the 2000 year-classes dominated, while the 2000 year-class dominated in the northern part of the Faroese EEZ (Fig. 6). The total biomass estimate of blue whiting in the Faroese area in May 2003 was 4.8 million tonnes (Table 1).
The average sA values of herring by statistical square from the Magnus Heinason survey are shown in Fig 3. The highest concentrations of herring observed by Magnus Heinason were located in the area from 63°30'-66°00'N and 2°00'-8°30'W. The herring was large (35.5 cm and 355 g on average, Fig. 7 and 8). The age of the herring was determined from otholit readings and indicate that old herring was dominating the in the area, including the 1998-1994 year-classes, with the 1996 and 1995 year-classes dominating (Fig. 9).
Combined abundance estimates of herring will be given in the 2003 PGSPFN report to ICES (ICES CM 2003/D:06), at a meeting in Tórshavn in late August 2003. Similarly the distribution and biomass of plankton and temperature charts by depth will be combined (Faroese, Norwegian and Icelandic data) and presented in the PGSPFN report (ICES CM 2003/D:06).
REFERENCES
ICES 2003. Report of the Planning Group on Surveys on Pelagic Fish in the Norwegian Sea 2003.
ICES CM 2003 (D:06)
Table 1. Age stratified abundance estimates of post-spawning blue whiting in the Faroes area during May 2003. Data from R/V Magnus Heinason. Biomass in thousand tonnes, numbers in millions, L= mean total length (cm), and W= mean weight (g). Target strength used for blue whiting, TS= 21.8 log(L)-72.8 dB.
Faroese area Age
May 2003 1 2 3 4 5 6 7 Total
Northern area
Biomass 62 314 1,030 479 165 68 7 2.125
Numbers 1,085 3,415 9,587 3,449 1,040 368 27 18.971
L (cm) 20.4 24.0 25.6 28.1 29.6 31.0 34.5 25.8
W (g) 58 92 107 139 159 183 266 112
Southern area
Biomass 786 477 1,159 204 19 7 0 2.652
Numbers 19,821 6,917 14,824 1,974 138 51 0 43.725
L (cm) 19.2 23.4 25 27.7 30.3 29 0 22.2
W (g) 40 69 78 103 134 132 0 61
Total area
Biomass 848 791 2,189 683 184 75 7 4.777
Numbers 20,906 10,332 24,411 5,423 1,178 419 27 62.696
L (cm) 19.2 23.6 25.2 28.0 29.7 30.8 34.5 23.4
W (g) 41 77 90 126 156 177 266 77.3
0131 0134 0137 0135 0138
0142
0120
0127 0111
0126
0170 0143
0019
0021
00230024
00280029 0036 0042
0048 0055
006100630064 0072
0075
0090 0099 01040103
0106 0116
0122
0153 0159
0162 0164 0165 0166
0168
0169
Fig. 1. Cruise tracks with hydrographic stations and trawl stations in the Faroese area and in the southern part of Norwegian Sea, Magnus Heinason 30/4-28/5 2003.
65°N
60°N
15°W 0°E5°W
10°W
413 132 392 311 85
236 356 136
482 352 206
293 412
1,227 858 113 1,250
568 981 3,378 3,553 0 552 453 337 821 1,266
1,000 2,638 1,360 0 0 236 520 644 756 1,981
0 1
975 1,256 1,425 0 27 342 439 756 3 1 4
1,938 666 1,031 1,009 82 334 349 912 373 355 72
1 73
680 460 1,430
225 117 327 265 343 91 32 58
1,202 1,022 121 190 271 30 51
70 47
71 41
øki0332_EK500_icespunt by Avg_BW 1,200 to 5,000 (13)
600 to 1,200 (14) 300 to 600 (21) 150 to 300 (8) 50 to 150 (14) 1 to 50 (9) 0 to 0 (5)
Fig. 2. Mean integration values (sA, m2/nm2) of blue whiting per statistical square, May 2003.
65°N
60°N
0°E5°W
10°W
15°W
0 0 0
0 0
0 0 0
0 0 0
0 0
0 0 0 170
0 0 0 0 0 0 0 0 144 170
0 0 0 0 0 0 0 68 151
83 0 0
0 0 0 0 0 0 24 70 3 0 0
0 0 0 0 0 1 2 110
1 52 388 389 0
0 0 0 0 0 96 151
1 91 83 0
0 0 0 127 104 26 38
0 0
0 0
øki0332_EK500_icespunt by Avg_HE 200 to 500 (2) 100 to 200 (8) 50 to 100 (7) 10 to 50 (3) 1 to 10 (3) 0 to 0 (60)
Fig. 3. Mean integration values (sA, m2/nm2) of herring per statistical square, May 2003.
0 5 10 15 20 25
10 15 20 25 30 35 40
Longd (cm)
%
Sunnanfyri Norðanfyri
Fig. 4. Length distribution of blue whiting in the southern part (< 62°N, dark bars) and in the northern of the Faroese area sampled from Magnus Heinason, May 2003.
0 50 100 150 200 250 300 350 400 450 500
10 50 90 130 170 210 250 290 Vekt (g)
Tal
Fig. 5. Weight distribution of blue whiting in the southern part (< 62°N, dark bars) and in the northern of the Faroese area sampled from Magnus Heinason, May 2003.
0 50 100 150 200 250 300
1 2 3 4 5 6 7
Age
Numbers
Fig. 6. Age distribution of blue whiting in the southern part (< 62°N, dark bars) and in the northern of the Faroese area sampled from Magnus Heinason, May 2003.
0 5 10 15 20 25 30 35 40 45
30 31 32 33 34 35 36 37 38 39 40 Longd (cm)
%
Fig. 7. Length distribution of herring in the northern part of Faroese area (and in the southern part of Norwegian Sea) sampled from Magnus Heinason, May 2003.
0 20 40 60 80 100 120 140 160
150 200 250 300 350 400 450 500 Vekt (g)
Tal
Fig. 8. Weight distribution of herring in the northern part of Faroese area (and in the southern part of Norwegian Sea) sampled from Magnus Heinason, May 2003. The herring was rather thin compared to length, but the stomach and gut was full of prey (Calanus finmarchius and Meganyctiphanes norvegica).
0 20 40 60 80 100 120 140 160 180 200
3 4 5 6 7 8 9 10 11 12
Age
Numbers
Fig. 9. Age distribution of herring in the northern part of Faroese area (and in the southern part of Norwegian Sea) sampled from Magnus Heinason, May 2003.
