Faroese Fishery Laboratory

A study of the availability and catchability of mesopelagic fish in the Northeast Atlantic during a research cruise with R/V “Magnus Heinason” 30/3 – 13/4 and 4/5 – 18/5-2005

by

Súni Lamhauge*, John Willy Valdemarsen** and Kristian Zachariassen

FRS Smárit 05/05

This report is not to be quoted without prior consultation with the respective scientists.

A study of the availability and catchability of mesopelagic fish in the Northeast Atlantic during a research cruise with R/V “Magnus Heinason” 30/3 – 13/4 and 4/5 – 18/5-2005

Súni Lamhauge*, John Willy Valdemarsen** and Kristian Zachariassen

Faroese Fishery Laboratory, PO-Box 3051, Nóatún 1, FO-110 Tórshavn, Faroe Island, Phone: (+298) 35 39 00, Fax: (+298) 35 39 01

*corresponding author ** Institute of Marine Research,

Abstract

A pilot project was made to estimate occurrence of exploitable densities of krill and mesopelagic fish in Faroese zone in spring 2005, to study the escape behaviour of mesopelagic species, and to evaluate various designs of survey trawls.

The results indicated that mesopelagic fish species and krill did not escape actively through the large meshes but were passively filtered out of the trawl. Larger fish like blue whiting and herring were herded towards the center of the trawl.

The density of mesopelagic fish and krill was less than 1 g/m3 during the trial period, which is considered too low to make commercial fishing profitable.

Valuable information on composition of fish escapement was gained from the collecting bag mounted on the outside of the upper trawl panel, and they will be used in future blue whiting and herring stock assessment cruises.

Introduction

With a growing global aquaculture industry, there is an increasing demand for fish protein and fish oil as feed. Marine organisms in lower tropic levels, like mesopelagic fish and krill are known to exist in large biomasses globally. These resources are presently under-exploited, and therefore there is a growing interest to start a commercial fishery for these organisms. This Nordic project was initiated to evaluate the possibility to develop such a fishery in the Northeast Atlantic, primarily based on mesopelagic species. Besides the identification of fishable concentrations in the areas of interest (the Northeast Atlantic), a major obstacle for a successful development of such a fishery is the choice of the optimal fishing technique. The reported study was primarily designed to learn more about the behavior of mesopelagic fish in the trawling process as basis for development of a proper trawl design and fishing practice.

Capture of marine organisms for fish meal and fish oil production require large catches with a minimum of fishing effort, primarily because of a low price of the processed product. As trawling is the only possible fishing method for small organisms like mesopelagic fish and krill, efficient capture depends on the availability of high-density fish aggregations in layers or in schools. The efficiency of a pelagic trawl depends primarily on the fishable volume. Large meshes in the front part of the trawl efficiently herd some “reactive” fish species, and the trawl can thus be designed with an opening area of the trawl more than 250.000 m2 (e.g. for blue whiting, mackerel and redfish). Smaller organisms, like mesopelagic fish (3-8 cm total length) have poorer swimming capability than larger pelagic species, and are thus not herded so effectively. For krill it is well known that capture is by pure filtering, which means that only organisms that is guided by the meshes are captured, whereas similar mechanisms are poorly known for mesopelagic fish.

1 Fishing for krill has recently been successful in the Antarctica by the M/Tr “Atlantic Navigator”, who obtained catch rates of krill corresponding to 50 tons of fish meal per day based on average density of 25-50 g/m3 (wet weight), and it is roughly estimated (John Willy Valdemarsen, personal com. cf. Anon., 2005). Such densities of krill are required to make exploitation of krill profitable. A trawl with an efficient opening area of 100 m2 towed with a speed of 2 kn (1 m/s) will catch around 9 tonnes/hour when the average density is 25 g/m3.

Assuming that mesopelagic fish are capable of some avoidance reaction when stimulated, a density in the order of 5-10 g/m3 might be sufficient for commercial capture (John Willy Valdemarsen, personal com. cf.Anon, 2005). A trawl with an efficient mouth area of 400 m2 towed with a speed of 2.5 kn (1.25m/s) should be able to catch 9 tonnes/hour on average densities of 5 g/m3.

Experimental fishing for capture of mesopelagic fish has been conducted in the gulf of Oman (Ziaee and Valinassab, 1998), in Atlantic waters (Anon., 2004), and in Faroes waters (Anon., 2004).

The catches in Oman were 1.5 – 6.7 tones/hour, and the densities were estimated to be in the range of 0.4 – 2.6 g/m3. The only species mentioned in this study was Benthosema pherotum, and the length distributions (SL) reported were between 1.4 and 4.0 cm. B. pherotum is also the only species mentioned in another report from the gulf of Oman (FAO, 2001). The maximum length (TL) of B. pherotum is 7.0 cm according to literature. The optimum mesh size of the codend was recommended to be 9 mm and the recommended towing speed should be 2.5 kn (2.2-2.8 kn).

In the Northwest Atlantic waters on the slopes of Grand Bank and Flemish Cap, the catches consisted of Myctophum punctatum, Ceratoscopelus maderensis, Benthosema glaciale and Notoscopelus kroeyeri. N. kroeyeri was the most abundant species. The catches in Filin’s research (Mazhirina and Filin, 1987; Filin, 1989; Filin, 1995; Filin, 1998; Poletaev, et al, 1991) were usually between 1 kg to over 500 kg; however, maximum daily catch rates were 25 to 40 tonnes.

In April - June 1984, three investigations according to PINRO research programme were conducted with the vessels MG-1341 “Lensk”, MG-1362 “Vilnus” and MB-2645 “Suloy” The investigations were carried out in the international waters of the Northeast Atlantic along the economic zones of Iceland, UK and Ireland. No commercially attractive concentrations of lanternfish were found and catches did not exceed 24 kg (Poletaev, et al, 1991).

In Faroese waters Notoscopelus kroeyeri, Benthosema glaciale and Myctophum punctatum are the most common mesopelagic fish besides pearlsides (Maurolicus müelleri). From salmon stomach analysis B. glaciale and M. punctatum are mainly found north of Faroe Island, whereas N. kroeyeri is located slightly more southerly. Due to limited data, it is uncertain whether spawning is occurring in Faroese waters. However, occasionally there have been found 0-group myctophids on Faroe Bank in some years. The species caught were not identified.

Fishing trials in Faroese waters were conducted in 2002 (Anon, 2004), using a standard blue whiting midwater trawl with 19.6 mm codend mesh size. The catch was insignificant and it was concluded, that the trawl did not catch myctophids efficiently.

From studies of by-catch in the blue whiting fishery in Faroese waters using a 50 mm meshsize codend, it was apparent that myctophids (Notoscopelus kroeyeri, Lampanyctus intricarius, Lampanyctus macdonaldi) were quite common in November and December 2004 (Lamhauge, 2004). The by-catch of myctophids for the entire fishing trip was 0.3 %, ranging from 15 – 150 kg/hour. It was observed, that small mesopelagic fish along with blue whiting were gilled in the meshes in the aft part of the belly while trying to escape. Stomach analyses of non-target by-catch like saithe and cod resulted in the observation that 25 % of the non-empty saithe stomachs

2 contained myctophids, ranging from 1 to 27 in each stomach. The cod however did not prey on myctophids (Lamhauge, 2004). In a study in May 2005, there was no by-catch of myctophids in the pelagic trawl fishery for blue whiting, and neither any content of myctophids in the saithe- and cod stomachs, and only blue whiting and Todarodes sp. were gilled in the meshes (Lamhauge 2005).

Objectives The objectives of this pilot project were: (1) to study the escape behaviour of mesopelagic species, (2) to evaluate various designs of survey trawls and (3) to estimate occurrence of exploitable densities of krill and mesopelagic fish in Faroese zone in April and May 2005.

Fishing Gear and instrumentation

• A pelagic trawl (Vonin blue whiting trawl with 640 m circumference) rigged with 5.5m2 trawl doors (740 kg), 450 kg weights on both wings and 120 m bridles with 8m lower bridle extensions. Drawing of the trawl with two different bellies and codends are shown in Figure 1 and 2 • A krill trawl with 176 m circumference, with small mesh belly and a codend with 6 mm mesh size, rigged with 120 m bridles and 2 m lower bridle extension and 200 kg wing weights (Figure 3) • Two small meshed collecting bag attached to an aluminum frame, mounted inside and outside on the upper panel of the trawl in the aft belly (Figure 4) • A small meshed collecting bag outside on the upper side of the trawl positioned in two different positions along the aft trawl belly (Figure 5) • Underwater SIT camera with artificial light mounted on a steel frame positioned on the upper panel in various positions along the trawl belly (Figure 5) • Scanmar gear monitoring instruments (distance sensors, speed-sensor, trawl eye, and door angle sensors) and Simrad FS Trawl Sonar • CTD and WP2 plankton sampler • Simrad EK 500 38 kHz and 120 kHz, both calibrated before the trials, and the EchoView post-processing software by Sonardata

Methods

Four independent methods were used during the trials to collect information about escape behavior/herding of fish and krill: . (1) Two types of collecting bags (2) Camera observation in the trawl belly (3) Observation with a trawl eye in inside and outside the trawl belly (4) Comparisons of catches of trawls with large (modified blue whiting trawl) and small mesh (krill trawl) bellies.

Collecting bags

The double bags illustrated in Figure 4 were designed to study the herding/filtering effect of meshes in front of the bags. The basic assumption was that if the belly meshes in front of the bags have no herding or guiding effect, the amount of catch of the relevant organisms in the two bags would be equal. On the other hand, if herding or guiding was occurring the catch in the inside bag would be

3 larger than in that on the outside. As the two frames were equal in sizes, a difference in catches in the outside and inside bags could be used as a quantitative estimate of the herding effect of small organisms by various belly mesh sizes and netting slope angles. Unfortunately the frames were not properly designed (too weak), and they were therefore damaged during the first experiment when attached between the 600mm and 400 mm meshes in the blue whiting trawl.

The second bag illustrated in Figure 5 was designed to cover meshes of the upper panel, corresponding to an area of a mesh with a bar length of approximately 1800mm, the bag thus covered 324 meshes when position above the 200 mm panel and 81 meshes of the 400 mm panel. The positions of the bags during the experiments are described in table 1.

Camera observations

A self-recording low light SIT camera was positioned inside the trawl belly to observe herding/escapement of fish through panels of various mesh sizes. Although we had some technical problems with the use of the camera (wrongly oriented etc) during the experiments, these observations demonstrated escapement through meshes and other useful information like mesh opening.

Trawl eye observations

A Scanmar trawl eye was positioned on the center of the upper panels at various positions along the belly. The main purpose of the use of this instrument was to measure the diameter at various positions along the belly in front of the codend. A secondary use of the instrument was to record acoustic targets above and below the trawl belly. Observation of targets on the outside of the trawl indicates that organisms have passed through the belly meshes in front of the “observation area”.

Comparisons between large and small meshed trawls

The catch composition in the two trawls used in the experiments was supposed to give indication of which mesh sizes are suitable to catch mesopelagic fish. Lack of fishable densities of target fish and bad weather conditions during the experiments made these comparisons of restricted value. Quite some effort was spent to search for fishable concentrations of mesopelagic fish (cruise tracks in Figure 7).

Calculations

The catch density was calculated as shown below: D = Q/F*Tl Where D = catch density (g/m³) Q = Qo + q Qo = amount of catch (g) q = amount of fish escaped from net (g) Tl= towing length (m) F= opening mouth area (m²)

The towing length (Tl) was the actual towing length in meters measured on a MapInfo plot. It was, however, not corrected for the seawater inflow due to the direction against and with the current.

4 In the calculation of the opening mouth area (F) for the collecting bags, it was anticipated (calculated) that the belly angle was 4.30, and the covered area was 1.67 m2 at 200 mm meshes and 1.88 m2 at 400 mm meshes. Then the projected area in the towing direction could be calculated as:

200 mm meshes: 1.67xsin4,3º= 0.13 m² 400 mm meshes: 1.88xsin4,3º= 0.14 m²

In the calculation of the fishable mouth area (F), three different areas are used for different categories of targets, A=large fish like Blue whiting and herring, B=mesopelagic fish and C=krill. For category A the entrance area of the trawl is the vertical height * horizontal spread, for B it is the cross section in front of 40 mm mesh size and for category C it is the cross section with meshes less than 20 mm. The geometry of the krill trawl was measured in in an earlier experiment with the same trawl. The measurements of the Vonin 640 m trawl was done primarily with the Scanmar trawl eye positioned in various positions along the belly. The results of these measurements are shown in Figure 6. The estimated F for both trawls based one these measurements for each category were then:

A B C Krill trawl 13m*13m=169m2 Π*(5)2=78,8m2 π *(1,6)2=8m2 Vonin640 m with small 40m*70m=2800m2 π *0.902 = 2.54 m2 π* 0.752 = 1,76 m2 mesh belly Vonin640m with blue 40m*70m=2800m2 π *0.902 = 2.54 m2 0 whiting belly

Conduct of the experiments

As shown on the map in Figure 7, the experiments were conducted in two periods south and north of the Fareoe Island, respectively. During the first cruise (30/3-13/4) most of the gear experiments were conducted, whereas the last period (4/5 – 18/5 -2005) focused on testing the collecting bag attached to the 400 mm meshes of the upper belly panel. The weather condition during the first period was characterized with mostly very strong winds, and the experimental fishing was therefore limited to a few hauls. Most of the effort was devoted to searching for fishable concentrations of what was believed to be mesopelagic fish. When “suitable” concentrations of mesopelagic fish and krill were located in a layer by the echo sounder, a trawl haul was taken. The various experiments are summarized in table 1.

Results

The catch results and density estimates based on the assumption of F for the various trawls and species are shown in Table 2 and 3 as well as densities calculated if the various species were passively overtaken by the projected area of the collecting bags positioned in the upper belly of the trawl over the 400 mm meshes. Although the material from the collecting bag tests are rather limited, these tests clearly demonstrated that the bag was properly designed and that it caught various sizes and species of marine organisms. A general observation was that the collecting bag captured filtered organisms in similar amounts as could be expected from the assumed fishing area of the trawl codend as illustrated by the calculated densities of krill caught in the codend of the Vonin 640 m trawl with small mesh codend and in the collecting bag, 0.53 g/m3 and 0.22 g/m3, respectively. It was also obvious that significant numbers of blue whiting were caught in the collecting bag. As it is unlikely that blue whiting is passively overtaken by the net covered by the collecting bag, an active escape through the meshes of the 200 and 400 mm panels into the collecting bag is the most likely

5 explanation. Assuming that the escapement into the collecting bag is representative for all the 200 mm and 400 mm belly sections, an escapement as indicated in Table 4 for individual hauls might occur. Certainly only one bag covering approximately 1.5 % of the 200-400 mm sections is a small area, and therefore these calculations are only and indication that ecapement of blue whiting takes place in the aft part of the Vonin 640 m trawl. The same is likely for herring although only one catch of herring appeared in the collecting bag during the second part of the cruise. The camera recordings indicated that larger fish like blue whiting were herded and went further back in the belly. A few fish were, however, observed to swim actively out of the trawl and small organisms were passively going trough the large meshes where the camera was situated (Figure 5). When the trawl eye was positioned on the upper panel of the codend entrance of the Vonin 640 m trawl echoes were recorded 5-15 m above the sensor indicating that “objects” had passed through the larger meshes of the upper panel in the belly section. Mesopelagic fish (Maurolicus müelleri, Benthosema glaciale, Notoscopelus kroeyeri) were caught at the same rate in the codend with 40 mm meshes as in the collecting bag placed on the belly at the beginning of 400 mm meshes (homoscedastic t-test, P=0.25). On the contrary, there was a tendency toward a higher catch of mesopelagic fish in the codend with 12 mm meshes than in the collecting bag placed on the belly at the beginning of the 200 mm meshes (heteroscedastic t-test, P=0.04). The M. müelleri and N. kroeyeri were caught in the first period in southern Faroese waters (Figure 7) and B. glaciale were more scattered and was caught both in the southern and northern areas in small amounts. The densities of mesopelagic fish in all areas were less than one g/m3. Whether krill was caught at the same rate in the collecting bag as in the codend could not be tested due to the mesh sizes in the codend, which were to large to efficiently retain krill. The densities (g/m3) of krill were also less than one gram (Table 3).

Among other fish species which we caught in small amounts where Todarodes sagittatus, Argyropelecus ilfersi, Pterycombus brama, Chauliodus sloani, Lampanyctus intricarius, Lampanyctus macdonaldi, Entelurus aequoreus, Nansenia groenlandica, Pollachius virens (saithe), Sebastes mentella.

Discussion

The catch of blue whiting and in one occasion herring in the collecting bag covering the 400 mm and 200 mm upper panels is a clear indication that the trawl belly is not optimal for catching such fish species. Although the calculation of escapement, on average 10 % through the 200/400 mm belly section, is based on only one collecting bag covering a restricted area on top of the belly, occurrence of blue whiting in most of the hauls is clear indication of frequent escapement. As the catches were rather low in all experimental tows, this loss of fish through belly meshes can not be explained by panic behavior when fish becomes densely packed in the narrow belly section of the trawl. The assumptions of the fishable area of the Vonin 640 m trawl of 2800 m2 therefore have to be reduced. Density estimates of larger fish (herring and blue whiting) from codend catches shown in Table 3 should therefore be considered underestimated. The density estimates of mesopelagic fish based on codend catches in the large Vonin 640 m trawl with a small mesh aft belly and codend are in the order of 10 times higher than that estimated from catches in the collecting bags. A possible explanation is that the herding of the aft belly meshes was better than used in the calculations (2.54 m2). Based on this new information 25 m2 fishing area should be used for such species. The catches of mesopelagic fish in the 40 mm codend were very low in all trials. Such meshes are therefore far too big to retain these species. It is therefore necessary to use collecting bags attached to the trawl belly to get information about presence of these fishes in surveys or commercial fishing with a blue whiting trawl with 40 mm codend mesh size.

6 Concluding remarks

From the present results, it can be concluded that the concentration of mesopelagic fish and krill in the study area from 30/13 to 3/4 and from 4/5 to 18/5-2005 was less than 1 gram per cubic meter of seawater, which is considered too low to make fishing profitable. In 2006 it is planned to use 3 collecting bags of the later type, to attempt an estimate of q, which is the amount of fish that escapees from the net in the density equation. We will also estimate the mesopelagic fish and krill density in other areas in Faroese waters. Additionally we will use the collecting bags to validate the biological samples in future acoustic scrutinizing.

References Anon., (2004) Workshop on mesopelagic fish Tórshavn, Faroe Island 7-8 February 2004 http://www.frs.fo/ew/media/Ritgerðir/2004/Workshop_mesopelagic_fish.pdf

Anon., (2005) Project meeting on mesopelagic fish and krill 2-3 March 2005, Nordatlantsbrygge 91, 4sal. , , Nordisk Ministerråd

FAO, (2001) Trilateral workshop on lanternfish in the gulf of Oman, Muscat, Oman, 7 – 9 May 2001. FAO Fisheries Report No. 665, ISSN 0429-9337

Filin, A.A. (1989) Some Data on the Distribution of the Young og Notoscopelus Kroeyerii (Myctophidae). Voprosy Ikhtiologii, 29 (6), 1989, 1035-1037.

Filin, A.A. (1995) Growth, Size and Age Composition of the Notoscopelus kroeyerii (Myctophidae). Journal of Ichthycology, Vol. 37. No. 1, pp 27 - 32

Filin, A.A. (1998) Occurrence and Vertical Distribution of Notoscopelus kroeyerii (Myctophidae). Journal of Ichthycology, Vol. 38. No. 2, pp 213 - 217

Lamhauge, S. (2004) Hjáveiða í flótitroli. Royndir gjørdar við Næraberg. FRS Smárit 04/06. 12 pp. Faroese Fisheries Laboratory Box 3051, Nóatún, FO-110 Tórshavn. (In Faroese)

Lamhauge, S. (2005) Hjáveiða í flótitroli. Royndir gjørdar við Næraberg. 24.5.2005 – 5.6.2005. FRS smárit 05/03. Faroese Fisheries Laboratory Box 3051, Nóatún, FO-110 Tórshavn. (In Faroese)

Mazhirina, G.P. and Filin, A.A (1987) Gonad Development and Spawning of Notoscopelus Krøyeri in the Nortwest Atlantic, with Observations on Other Biological Caracteristics. J. Northw. Atl. Fish. Sci., Vol. 7

Poletaev V.A.,Gorchinsky K.V.,Filin A.A.,Chumakov A.K. (1991) Preliminary results of studies on lanternfishes from the Atlantic and South Oceans. PINRO complex fisheries researches in the North Basin. (translated to english from russian) pp 118 – 129. PINRO, Murmansk, Russia

Ziaee S. A and Valinassab,T. (1998) Trial fishing for lantern fishes (myctophids) in the Gulf og Oman (1989-1990). FAO Fisheries Circular No. 935 FIRM/C935. http://www.fao.org/docrep/W8239E/W8239E00.htm

7

Figure 1. Vónin 640 m.

8

Figure 2. Vónin 640 m with a belly and codend made for mesopelagic fish.

9 Figure 3. A 176 m circumference krilltrawl without codend (Designed by John Willy Valdemarsen, Norway).

14 mm tråd

200 24

99,5

95 50 95

240 200 24 19,5

201

100 16 19,5 385 40 12 99,5 808 22 10 249,5 1300

22 10 299,5 1100

834 22 10 299,5

670 22 10 299,5

480

22 12 399,5 480

10 Float 2x2.6 kg

Opening Side

5,10m 1m frame 5 mm mesh size collecting bag.

Codend

Figure 4. A small mesh (6 mm) double collecting bag attached to two aluminums frames, outside and inside the upper side of the trawl.

Collecting bag

Belly

Collecting bag

Codend Camera

From the side

Figure 5. In the right upper corner the single collecting bag is situated on top of the trawl belly, from the side. On the left upper corner a close up of the collecting bag can be seen from the front. In the lower part of the figure, the entire trawl can be seen, with the collecting bag and the placement of the video camera.

11

16000mm 8000mm 4000mm 2000mm 1000mm 600mm 400mm 200mm 100mm

Vertical height 40 m 6.5 m 3.2 m 1.6 m Horizontal distance 70 m 7.0 m 3.3 m 1.6 m

Figure 6. Measured diameter at various positions along the belly of the Vonin 640 m trawl.

12 67

05320019

66 05320017 05320026 05320007

65

05320036 05320032 05320009 64 05320001

05320046 63 05320013

62 05200001

05200018 61 12 11 10 9

05200004 05200007 05200017 60

13 12 11 10 9 876 5 4 3 21

Figure 7. Cruise tracks while observing acoustic backscattering. The area south of 62° was the first part of the cruise (30/3 – 13/4 – 2005), and the area north of 62° was during the last part of the cruise (4/5 – 18/5 -2005). The biological sampling numbers are shown.

13 Table 1. Experiments carried out during the two cruises. Drawing of the trawls and collecting bag are shown in figure 1 – 6. Station Date Tow Position Pos. Trawl type Codend Collecting bag position SIT Camera pos. start Lat Lon 05200001 01-04-2005 13:10 61.89 -9.20 Krilltrawl PTK176 8 mm ÷ ÷ 05200002 01-04-2005 15:45 61.81 -8.87 Krilltrawl PTK176 8 mm ÷ ÷ Front edge of 200mm ÷ 05200004 03-04-2005 09:34 60.36 -7.06 Vonin 640 m. 12 mm meshes Front edge of 200mm ÷ 05200005 04-04-2005 14:34 60.16 -7.34 Vonin 640 m. 12 mm meshes Front edge of 200mm ÷ 05200007 05-04-2005 07:14 60.11 -9.38 Vonin 640 m. 12 mm meshes ÷ 2 m in front of front 05200008 05-04-2005 13:20 60.03 -9.38 Vonin 640 m. 12 mm edge of 200mm meshes ÷ 2 m in front of front 05200010 05-04-2005 07:06 60.09 -10.33 Vonin 640 m. 12 mm edge of 400mm meshes ÷ 2 m in front of front 05200011 06-04-2005 11:33 60.09 -10.32 Vonin 640 m. 12 mm edge of 600mm meshes ÷ ÷ 05200012 06-04-2005 14:07 60.11 -10.50 Krilltrawl PTK176 8 mm ÷ 2 m in front of front 05200013 06-04-2005 17:01 60.09 -10.32 Vonin 640 m. 40 mm edge of 600mm meshes Front edge of 400mm 2 m in front of front 05200014 06-04-2005 07:37 60.27 -9.28 Vonin 640 m. 40 mm meshes edge of 600mm meshes Front edge of 400mm ÷ 05200015 06-04-2005 10:29 60.34 -9.30 Vonin 640 m. 40 mm meshes ÷ ÷ 05200016 06-04-2005 12:08 60.32 -9.30 Krilltrawl PTK176 8 mm Front edge of 400mm ÷ 05200017 07-04-2005 16:03 60.05 -7.02 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05200018 08-04-2005 16:20 60.57 -7.35 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320001 07-05-2005 10:46 63.64 -1.64 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320003 07-05-2005 15:34 63.68 -1.63 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320007 09-05-2005 06:53 65.18 -1.85 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320009 09-05-2005 18:19 64.01 -2.69 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320013 10-05-2005 12:28 62.73 -4.37 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320017 11-05-2005 11:31 65.50 -2.50 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320019 11-05-2005 22:18 66.20 -4.12 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320021 12-05-2005 10:23 66.25 -5.06 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320026 13-05-2005 12:23 65.40 -5.38 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320032 14-05-2005 20:00 64.41 -5.96 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320036 15-05-2005 11:08 64.32 -8.75 Vonin 640 m. 40 mm meshes Front edge of 400mm ÷ 05320046 16-05-2005 15:33 62.93 -7.45 Vonin 640 m. 40 mm meshes

14 Table 2. Catch results of main species in the codends when the collecting bag was used in the Vonin 640 m trawl and in the codend of the krill trawl. The species abbreviations are below the table.

Trawl, and Catch, codend meshsize Catch, collecting Towing in mm. Station Species codend, g bag, g length, m 05200001 KRI 2473 4470 krilltrawl, 8 05200001 LAK 363 4470 krilltrawl, 8 05200001 SJP 8 4470 krilltrawl, 8 05200002 KRI 6050 3130 krilltrawl, 8 05200002 LAK 1034 3130 krilltrawl, 8 05200002 LPR 44 3130 krilltrawl, 8 05200004 KRI 8646 476.31 14100 Vonin 640 m., 12 05200004 LAK 3519 39.69 14100 Vonin 640 m., 12 05200005 BLU 178429 530 11100 Vonin 640 m., 12 05200005 LPR 34 0 11100 Vonin 640 m., 12 05200005 MPR 122 0 11100 Vonin 640 m., 12 05200007 BLU 67354 0 6900 Vonin 640 m., 12 05200007 KRI 8626 144 6900 Vonin 640 m., 12 05200007 LAK 295 4 6900 Vonin 640 m., 12 05200007 LAM 2856 0 6900 Vonin 640 m., 12 05200007 LPR 3301 58 6900 Vonin 640 m., 12 05200007 MPR 2405 0 6900 Vonin 640 m., 12 05200007 NAN 58 0 6900 Vonin 640 m., 12 05200007 SJP 145 0 6900 Vonin 640 m., 12 05200012 SJP 3224 3100 krilltrawl, 8 05200014 BLU 21032 0 7700 Vonin 640 m., 40 05200014 KRI 4 234 7700 Vonin 640 m., 40 05200014 LAK 10 14 7700 Vonin 640 m., 40 05200014 LAM 344 0 7700 Vonin 640 m., 40 05200014 LPR 40 20 7700 Vonin 640 m., 40 05200014 MPR 316 0 7700 Vonin 640 m., 40 05200015 KRI 0 24 1500 Vonin 640 m,, 40 05200015 LAK 0 40 1500 Vonin 640 m,, 40 05200016 LAK 189 2600 krilltrawl, 8 05200016 SJP 925 2600 krilltrawl, 8 05200017 BLU 693889 72 6840 Vonin 640 m,, 40 05200017 KRI 0 2 6840 Vonin 640 m,, 40 05200017 LAK 0 2 6840 Vonin 640 m,, 40 05200017 MPR 876 0 6840 Vonin 640 m,, 40 05200018 BLU 93422 36 5000 Vonin 640 m,, 40 05200018 KRI 0 120 5000 Vonin 640 m,, 40 05200018 LPR 0 0 5000 Vonin 640 m,, 40 05200018 SAI 2065 0 5000 Vonin 640 m,, 40 05320001 BLU 63210 162 9200 Vonin 640 m,, 40 05320001 HER 232 0 9200 Vonin 640 m,, 40 05320001 KRI 0 24 9200 Vonin 640 m,, 40 05320001 LPR 0 2 9200 Vonin 640 m,, 40 05320001 SAI 1766 0 9200 Vonin 640 m,, 40 05320003 BLU 238 0 53500 Vonin 640 m,, 40 05320003 HER 2092 0 53500 Vonin 640 m,, 40 05320003 SJP 124 0 53500 Vonin 640 m,, 40 05320007 BLU 95740 186 11800 Vonin 640 m,, 40 05320007 HER 15960 0 11800 Vonin 640 m,, 40 05320009 BLU 30425 88 13400 Vonin 640 m,, 40 05320009 HER 2866 0 13400 Vonin 640 m,, 40 05320009 KRI 0 48 13400 Vonin 640 m,, 40

15 05320013 BLU 433427 1446 11600 Vonin 640 m,, 40 05320013 KRI 0 78 11600 Vonin 640 m,, 40 05320013 LPR 223 132 11600 Vonin 640 m,, 40 05320013 SAI 1372 0 11600 Vonin 640 m,, 40 05320017 BLU 78217 98 8100 Vonin 640 m,, 40 05320017 KRI 0 12 8100 Vonin 640 m,, 40 05320017 LPR 0 6 8100 Vonin 640 m,, 40 05320019 BLU 68955 196 55600 Vonin 640 m,, 40 05320019 HER 17910 0 55600 Vonin 640 m,, 40 05320019 KRI 0 82 55600 Vonin 640 m,, 40 05320021 BLU 67695 552 14600 Vonin 640 m,, 40 05320026 BLU 9052 112 13600 Vonin 640 m,, 40 05320026 HER 56915 0 13600 Vonin 640 m,, 40 05320026 KRI 0 266 13600 Vonin 640 m,, 40 05320026 LPR 28 6 13600 Vonin 640 m,, 40 05320032 HER 78455 2634 15600 Vonin 640 m,, 40 05320032 KRI 0 118 15600 Vonin 640 m,, 40 05320032 LPR 0 32 15600 Vonin 640 m,, 40 05320036 BLU 51677 0 16400 Vonin 640 m,, 40 05320036 HER 2462 0 16400 Vonin 640 m,, 40 05320046 BLU 11610 0 5900 Vonin 640 m,, 40 05320046 KRI 0 50 5900 Vonin 640 m,, 40 05320046 LPR 26 4 5900 Vonin 640 m,, 40

*Species: Large fish: BLU = blue whiting HER = herring Mesopelagic fish: MPR = Notoscopelus kroeyeri LPR = Benthosema glaciale LAK = Maurolicus müelleri LAM = Lampanyctus intricarius NAN = Nansenia groenlandica Krill: KRI = krill Other fish: SAI = Saithe SJP = Entelurus aequoreus

Table 3. Average densities (g/m3) of large fish (blue whiting and herring), mesopelagic fish (N. kroeyeri, B. glaciale, M. müelleri, L. intricarius), and krill (M. norvegica). Density g/m3 Mesh size on Samples Meso Krill Large fish 4 mm collectingbag at 200 mm meshes 3 0.01 0.22 0.19 4 mm collectingbag at 400 mm meshes 16 0.02 0.06 0.13 8 mm Codend (krill trawl) 4 0.001 0.14 0 12 mm codend 3 0.23 0.53 0.004 40 mm codend 16 0.03 0 0.003

16 Table 4. Estimated escapement of blue whiting through the 200 and 400 mm belly panels based on the assumption that the catch in the collecting bag is representative for the escapement in this belly region. Codend Collecting bag Estimated escaped Haul no Catch (g) Catch(g) (g) A B B*75 % escape

5200005 178,429 530 39,750 18.2

5200007 67,354 0 0 0

5200014 21,032 0 0 0

5200017 693,889 72 5,400 0.7 5200018 93,422 36 2,700 2.8 5320001 63,210 162 12,150 16.1 5320003 238 0 0 0 5320007 95,740 186 13,950 12.7 5320009 30,425 88 6,600 17.8 5320013 433,427 1,446 108,450 20.0 5320017 78,217 98 7,350 8.5 5320019 68,955 196 14,700 17.5 5320021 67,695 552 41,400 37.9 5320026 9,052 112 8,400 48.1 5320036 51,677 0 0 0 5320046 11,610 0 0 0 Total 1,964,372 3,478 260,850 11.7

17