Scientific survey report

Danish International Bottom Trawl Survey

2022

The Danish research vessel Dana is used for the Danish participation in the International Bottom Trawl Survey (IBTS), which has the purpose of annually monitoring fish species. Internationally, each nation surveys part of the area, with some overlap in coverage and depth stratification, in a coordinated sampling design.

The IBTS is conducted twice a year in the first and fourth quarters as a depth-stratified survey. The strata are based on sub-divisions and depth layers. Each year the necessary stations are randomly selected before the beginning of the international trawl surveys, from a list of clear haul data. These stations are a stratified randomly selected sub-sample of the possible trawl tracks.

The standard haul is a 30-minutes haul with a towing speed of 3 knots. Trawling only takes place during daylight, defined as the time between 15 minutes past sunrise and 15 minutes before sunset.

All data can be found in the ICES DATRAS database (https://datras.ices.dk/Data_products/Download/Download_Data_public.aspx) and details about the survey design can be found in the ICES IBTS manual.

Period

Quarter 1

Activity

Here is shown a map with the survey activity. The map shows both valid and invalid stations, a station can be deemed invalid if the haoul could not be conducted within the guilines of the survey manual

Trawl Stations

Each trawl stations consists a haul of 30 minutes where all the catch documented, including litter. Biological samples to determine e.g. stock, age matuity are taken from individual fish.

CTD Stations

CTD (Conductivity - Temperature - Depth), are measured trough the water column, and used to calculate e.g. the oxygen and salinity content, key environmental variables for life in the ocean.

CTD Results

Here is shown a map the results of the CTD measurments at the bottom. The heatmap is made with linear interpolation between measurments, and can be seen as the general trend in the monment of the survey

Bottom oxygen

Bottom temperature

Bottom salinity

Catch Overview

Below is a table with the total catche and catches for selected species, in wiegth and numbers. The numbers are in some instances calculated based on representative subsampling of some abundant species. The maps illustrates for biodiveity the number of different species cougt on each station, and for CPUE (catch per unit effort) the catch in numbers standadized to a unit effort of one hour of hauling.
Weight (kg) Number Min. Length (mm) Max. Length (mm)
Total Catch 5927.7 77371
Haddock 3337.8 16946 160 440
Whiting 1149.8 11621 80 440
Herring 484.4 20601 65 300
Plaice 90.4 1049 60 440
Cod 33.4 41 80 840

CPUE

CPUE (catch per unit effort) shown as the catch in Numbers rasied to to pr hour of hauling

CPUE for Selected Species

CPUE (catch per unit effort) shown as the catch in Numbers rasied to to pr hour of hauling. The dots indicates the stations, and red dots indicates that a species where not found at all in that station. The scale is different between plots

Cod

Plaice

Whiting

Haddock

Herring

Biodiversity

Shown is the Number of species cought by station

Length Distributions

Here is shown the length distribution For the 10 most abundant comercieal species cought during the survey, allocated to each ship. The black line represents the average length distribution of the 5 years previus surveys.

Herring

Haddock

Sprat

Whiting

Common dab

Grey gurnard

Plaice

Norway pout

Lemon sole

Mackerel

All species Caught

The table below is an overview of all the different species cought in the survey, devided into the different ices areas covered by the surve.

Area - 20

Latin name English name Weight (kg) Number Min. Length (mm) Max. Length (mm)
Agonus cataphractus Pogge 0.0 1 150 150
Alloteuthis subulata European common squid 0.0 7 30 90
Amblyraja radiata Starry ray 0.5 1 380 380
Ammodytes marinus Lesser sandeel 0.2 133 70 195
Callionymus lyra Common dragonet 0.2 4 150 210
Clupea harengus Herring 51.2 2852 100 265
Cyclopterus lumpus Lumpfish 38.4 13 110 450
Echiichthys vipera Lesser weever 0.1 3 130 160
Eutrigla gurnardus Grey gurnard 1.0 14 80 260
Gadus morhua Cod 15.3 12 140 740
Glyptocephalus cynoglossus Witch 0.1 1 280 280
Hippoglossoides platessoides American plaice 8.5 162 130 250
Limanda limanda Common dab 13.1 161 60 290
Loligo forbesii Northern squid 0.1 1 150 150
Melanogrammus aeglefinus Haddock 1.4 5 190 380
Merlangius merlangus Whiting 31.9 323 90 400
Microstomus kitt Lemon sole 1.1 6 200 280
Molva molva Ling 1.0 1 560 560
Pleuronectes platessa Plaice 10.6 85 150 330
Scomber scombrus Mackerel 0.3 7 170 200
Scophthalmus rhombus Brill 1.0 1 400 400
Scyliorhinus canicula Lesser-spotted dogfish 1.7 2 610 610
Solea solea Sole 0.7 3 270 300
Sprattus sprattus Sprat 0.5 59 80 135
Trachinus draco Greater weever fish 0.3 3 220 270
Trisopterus esmarkii Norway pout 1.0 46 90 180
Trisopterus minutus Poor-cod 0.3 4 180 200

Area - 4B

Latin name English name Weight (kg) Number Min. Length (mm) Max. Length (mm)
Aequipecten opercularis Queen scallop 0.1 2
Agonus cataphractus Pogge 0.4 22 40 160
Alloteuthis subulata European common squid 9.6 2770 20 100
Alosa fallax Twaite shad 0.1 1 220 220
Amblyraja radiata Starry ray 10.7 26 170 480
Ammodytes marinus Lesser sandeel 0.2 70 55 185
Arnoglossus laterna Scaldfish 0.3 27 40 130
Buglossidium luteum Solenette 1.4 127 50 120
Callionymus lyra Common dragonet 0.6 22 40 220
Callionymus maculatus Spotted dragonet 0.0 1 100 100
Callionymus reticulatus Reticulated dragonet 0.0 1 150 150
Cancer pagurus Edible crab 30.9 60 104 231
Clupea harengus Herring 433.2 17749 65 300
Cyclopterus lumpus Lumpfish 18.3 5 190 460
Echiichthys vipera Lesser weever 0.3 10 90 150
Enchelyopus cimbrius Four-bearded rockling 1.7 30 160 300
Engraulis encrasicolus Anchovy 0.3 33 80 150
Entelurus aequoreus Snake pipefish 0.0 1 360 360
Eutrigla gurnardus Grey gurnard 107.2 1803 80 330
Gadus morhua Cod 18.1 29 80 840
Gaidropsarus vulgaris Three-bearded rockling 0.0 1 120 120
Glyptocephalus cynoglossus Witch 3.6 22 60 420
Hippoglossoides platessoides American plaice 12.0 349 70 230
Hyperoplus lanceolatus Greater sandeel 0.2 9 170 315
Illex coindetii Southern shortfin squid 0.0 3 40 50
Leucoraja naevus Cuckoo ray 0.5 1 420 420
Limanda limanda Common dab 418.4 7446 50 280
Liparis montagui Montague’s seasnail 0.0 1 70 70
Lithodes maja Norway king crab 2.5 6 62 109
Loligo forbesii Northern squid 2.7 16 80 290
Lophius piscatorius Angler fish 3.3 2 430 510
Melanogrammus aeglefinus Haddock 3336.4 16941 160 440
Merlangius merlangus Whiting 1118.0 11298 80 440
Micromesistius poutassou Blue whiting 0.2 4 170 230
Microstomus kitt Lemon sole 11.1 112 130 320
Mullus surmuletus Striped red mullet 1.0 10 110 280
Mustelus asterias Starry smooth-hound 15.5 40 350 630
Myoxocephalus scorpius Sculpin 3.5 48 70 300
Nephrops norvegicus Norway lobster 8.8 232 22 55
Pholis gunnellus Butter fish 0.0 1 60 60
Phrynorhombus norvegicus Norwegian topknot 0.1 8 60 90
Platichthys flesus Flounder 4.0 17 220 340
Pleuronectes platessa Plaice 79.8 964 60 440
Pollachius virens Saithe 2.3 2 470 560
Pomatoschistus spp. Sand gobies 0.0 30 30 70
Raja clavata Thornback ray 8.3 4 490 750
Raja montagui Spotted Ray 10.6 18 350 560
Rossia macrosoma Stout bobtail squid 0.1 76
Sardina pilchardus Pilchard 0.3 46 70 120
Scomber scombrus Mackerel 2.8 66 160 260
Scophthalmus maximus Turbot 2.6 4 250 440
Scyliorhinus canicula Lesser-spotted dogfish 5.1 8 270 610
Sepia officinalis Common cuttlefish 0.1 1 100 100
Solea solea Sole 0.3 2 230 240
Sprattus sprattus Sprat 50.5 12497 50 145
Squalus acanthias Spurdog 0.3 1 380 380
Syngnathus acus Great pipefish 0.0 13 90 130
Syngnathus rostellatus Lesser pipefish 0.0 1 130 130
Trachurus trachurus Horse mackerel 0.8 28 100 250
Trisopterus esmarkii Norway pout 7.4 331 80 200
Trisopterus luscus Bib 0.4 4 180 220
Trisopterus minutus Poor-cod 0.5 9 70 210

Quarter 3

Activity

Here is shown a map with the survey activity. The map shows both valid and invalid stations, a station can be deemed invalid if the haoul could not be conducted within the guilines of the survey manual

Trawl Stations

Each trawl stations consists a haul of 30 minutes where all the catch documented, including litter. Biological samples to determine e.g. stock, age matuity are taken from individual fish.

CTD Stations

CTD (Conductivity - Temperature - Depth), are measured trough the water column, and used to calculate e.g. the oxygen and salinity content, key environmental variables for life in the ocean.

CTD Results

Here is shown a map the results of the CTD measurments at the bottom. The heatmap is made with linear interpolation between measurments, and can be seen as the general trend in the monment of the survey

Bottom oxygen

Bottom temperature

Bottom salinity

Catch Overview

Below is a table with the total catche and catches for selected species, in wiegth and numbers. The numbers are in some instances calculated based on representative subsampling of some abundant species. The maps illustrates for biodiveity the number of different species cougt on each station, and for CPUE (catch per unit effort) the catch in numbers standadized to a unit effort of one hour of hauling.
Weight (kg) Number Min. Length (mm) Max. Length (mm)
Total Catch 32479.6 905087
Whiting 8591.7 183491 40 420
Haddock 8174.8 121312 80 470
Herring 2287.3 94997 60 330
Cod 414.1 720 70 1000
Plaice 407.8 3325 100 480

CPUE

CPUE (catch per unit effort) shown as the catch in Numbers rasied to to pr hour of hauling

CPUE for Selected Species

CPUE (catch per unit effort) shown as the catch in Numbers rasied to to pr hour of hauling. The dots indicates the stations, and red dots indicates that a species where not found at all in that station. The scale is different between plots

Cod

Plaice

Whiting

Haddock

Herring

Biodiversity

Shown is the Number of species cought by station

Length Distributions

Here is shown the length distribution For the 10 most abundant comercieal species cought during the survey, allocated to each ship. The black line represents the average length distribution of the 5 years previus surveys.

Sprat

Whiting

Haddock

Horse mackerel

Herring

Common dab

Norway pout

Mackerel

Grey gurnard

Plaice

All species Caught

The table below is an overview of all the different species cought in the survey, devided into the different ices areas covered by the surve.

Area - 20

Latin name English name Weight (kg) Number Min. Length (mm) Max. Length (mm)
Aequipecten opercularis Queen scallop 0.1 0
Ammodytes marinus Lesser sandeel 1.6 423 70 125
Callionymus lyra Common dragonet 0.2 4 170 250
Cancer pagurus Edible crab 16.0 58 80 170
Clupea harengus Herring 1.3 19 130 245
Echiichthys vipera Lesser weever 0.1 1 150 150
Eutrigla gurnardus Grey gurnard 94.5 830 140 320
Gadus morhua Cod 172.8 459 80 780
Glyptocephalus cynoglossus Witch 0.9 2 360 410
Hippoglossoides platessoides American plaice 22.1 385 110 250
Homarus gammarus European lobster 0.5 1 91 91
Hyperoplus lanceolatus Greater sandeel 20.0 571 190 300
Illex coindetii Southern shortfin squid 0.5 4 120 170
Limanda limanda Common dab 49.7 489 110 330
Loligo Loligo sp 3.9 212 30 110
Loligo forbesii Northern squid 3.6 19 120 250
Lophius piscatorius Angler fish 2.0 1 500 500
Melanogrammus aeglefinus Haddock 1733.2 3037 90 470
Merlangius merlangus Whiting 48.3 298 40 360
Merluccius merluccius Hake 42.8 24 410 840
Microstomus kitt Lemon sole 13.0 71 160 390
Molva molva Ling 1.9 1 680 680
Myoxocephalus scorpius Sculpin 0.1 1 180 180
Nephrops norvegicus Norway lobster 0.1 1 57 57
Pleuronectes platessa Plaice 34.9 233 100 410
Scomber scombrus Mackerel 551.7 2328 240 420
Scophthalmus maximus Turbot 2.6 4 300 320
Solea solea Sole 0.2 1 290 290
Trachinus draco Greater weever fish 42.6 195 220 430
Trachurus trachurus Horse mackerel 18.3 73 70 400
Trisopterus esmarkii Norway pout 31.8 1288 70 180

Area - 4A

Latin name English name Weight (kg) Number Min. Length (mm) Max. Length (mm)
Amblyraja radiata Starry ray 2.4 5 360 420
Anarhichas lupus Catfish 4.4 2 580 660
Argentina sphyraena Lesser silver smelt 0.4 7 170 250
Callionymus lyra Common dragonet 0.3 7 160 270
Clupea harengus Herring 112.9 645 245 310
Eledone cirrhosa Horned octopus 0.0 1
Eutrigla gurnardus Grey gurnard 17.1 89 180 370
Gadus morhua Cod 209.0 179 70 1000
Hippoglossoides platessoides American plaice 6.6 121 80 260
Illex coindetii Southern shortfin squid 0.3 2 150 180
Limanda limanda Common dab 1.1 22 120 240
Lophius piscatorius Angler fish 23.7 8 90 620
Melanogrammus aeglefinus Haddock 1347.0 4352 90 400
Merlangius merlangus Whiting 327.6 1298 100 420
Microstomus kitt Lemon sole 5.0 11 150 420
Molva molva Ling 5.0 2 740 810
Pholis gunnellus Butter fish 0.0 1 170 170
Pleuronectes platessa Plaice 6.7 13 290 480
Pollachius pollachius Pollack 1.7 1 640 640
Pollachius virens Saithe 129.8 158 360 560
Scomber scombrus Mackerel 53.4 154 290 390
Trachurus trachurus Horse mackerel 192.3 546 300 400
Trisopterus esmarkii Norway pout 95.3 21593 50 190

Area - 4B

Latin name English name Weight (kg) Number Min. Length (mm) Max. Length (mm)
Aequipecten opercularis Queen scallop 0.5 4
Agonus cataphractus Pogge 0.3 32 80 130
Alloteuthis subulata European common squid 25.4 4909 10 150
Amblyraja radiata Starry ray 5.6 17 90 440
Ammodytes marinus Lesser sandeel 0.2 17 105 190
Anarhichas lupus Catfish 1.0 1 470 470
Arnoglossus laterna Scaldfish 1.1 105 60 140
Buglossidium luteum Solenette 1.5 149 70 120
Callionymus lyra Common dragonet 6.1 167 100 240
Callionymus maculatus Spotted dragonet 0.0 3 70 160
Cancer pagurus Edible crab 34.8 60 65 215
Chelidonichthys lucerna Tub gurnard 3.4 10 200 390
Clupea harengus Herring 2020.1 78593 65 330
Echiichthys vipera Lesser weever 5.7 211 100 170
Enchelyopus cimbrius Four-bearded rockling 1.0 27 90 250
Engraulis encrasicolus Anchovy 0.1 4 120 190
Eutrigla gurnardus Grey gurnard 454.1 6565 110 340
Gadus morhua Cod 21.7 51 100 860
Glyptocephalus cynoglossus Witch 0.8 5 240 350
Gymnammodytes semisquamatus Smoothed sandeel 5.1 333 105 215
Helicolenus dactylopterus Blue-mouth redfish 0.3 3 160 200
Hippoglossoides platessoides American plaice 70.5 1247 100 260
Hippoglossus hippoglossus Atlantic halibut 44.0 1 1420 1420
Homarus gammarus European lobster 3.5 6 70 127
Hyperoplus lanceolatus Greater sandeel 5.8 170 155 320
Illex coindetii Southern shortfin squid 3.3 40 100 180
Lampetra fluviatilis River lamprey 0.1 1 330 330
Limanda limanda Common dab 2746.5 49008 90 350
Lithodes maja Norway king crab 2.2 4 84 113
Loligo Loligo sp 1.8 78 20 170
Loligo forbesii Northern squid 25.8 436 40 300
Lophius piscatorius Angler fish 13.7 7 160 630
Melanogrammus aeglefinus Haddock 5094.6 113923 80 370
Merlangius merlangus Whiting 7344.0 173215 50 350
Merluccius merluccius Hake 1.3 1 550 550
Micromesistius poutassou Blue whiting 0.1 1 210 210
Microstomus kitt Lemon sole 123.5 1243 110 360
Mullus surmuletus Striped red mullet 2.5 26 150 250
Mustelus asterias Starry smooth-hound 38.4 14 650 1080
Myoxocephalus scorpius Sculpin 0.7 11 100 220
Nephrops norvegicus Norway lobster 0.8 23 16 49
Pecten maximus Great scallop 0.7 2
Pholis gunnellus Butter fish 0.0 1 170 170
Phrynorhombus norvegicus Norwegian topknot 0.0 1 140 140
Platichthys flesus Flounder 0.3 1 300 300
Pleuronectes platessa Plaice 324.0 2502 130 420
Pollachius virens Saithe 4.2 24 240 320
Raja brachyura Blonde ray 2.0 2 470 530
Raja clavata Thornback ray 9.8 5 260 770
Raja montagui Spotted Ray 10.1 16 310 540
Sardina pilchardus Pilchard 12.5 92 80 250
Scomber scombrus Mackerel 1082.1 5251 40 390
Scophthalmus maximus Turbot 15.5 12 200 480
Scophthalmus rhombus Brill 5.0 9 230 430
Scyliorhinus canicula Lesser-spotted dogfish 345.5 438 440 670
Solea solea Sole 2.7 15 200 350
Sprattus sprattus Sprat 2271.7 247060 60 145
Todaropsis eblanae Lesser flying squid 0.2 3 90 100
Trachinus draco Greater weever fish 4.6 42 140 400
Trachurus trachurus Horse mackerel 92.0 22036 30 380
Trisopterus esmarkii Norway pout 0.1 15 60 160
Trisopterus luscus Bib 0.3 1 260 260
Trisopterus minutus Poor-cod 0.3 8 90 160
Zeus faber John dory 0.3 1 250 250

Area - 4C

Latin name English name Weight (kg) Number Min. Length (mm) Max. Length (mm)
Aequipecten opercularis Queen scallop 0.0 2
Agonus cataphractus Pogge 0.2 22 90 130
Alloteuthis subulata European common squid 33.2 4258 20 150
Ammodytes marinus Lesser sandeel 12.1 3162 70 150
Arnoglossus laterna Scaldfish 0.2 20 40 140
Bryozoa Bryozoans 1031.0 0
Buglossidium luteum Solenette 1.6 241 30 110
Callionymus lyra Common dragonet 2.0 52 40 250
Cancer pagurus Edible crab 39.3 109 76 165
Chelidonichthys cuculus Red gurnard 4.0 33 190 290
Chelidonichthys lucerna Tub gurnard 3.0 12 100 440
Chelon labrosus Thick lipped mullet 3.1 2 560 560
Clupea harengus Herring 153.0 15740 60 280
Dicentrarchus labrax Bass 3.2 4 380 430
Echiichthys vipera Lesser weever 19.4 882 50 180
Engraulis encrasicolus Anchovy 0.9 149 60 180
Entelurus aequoreus Snake pipefish 0.0 1 440 440
Eutrigla gurnardus Grey gurnard 9.8 89 100 350
Gadus morhua Cod 10.7 31 260 450
Galeorhinus galeus Tope 132.1 14 720 1460
Homarus gammarus European lobster 30.1 51 56 148
Hyperoplus lanceolatus Greater sandeel 10.3 694 125 290
Limanda limanda Common dab 334.8 6808 30 300
Liparis liparis Sea snail 0.0 9 50 70
Loligo Loligo sp 0.2 74 10 70
Loligo forbesii Northern squid 47.1 2457 20 280
Merlangius merlangus Whiting 871.9 8680 50 330
Micromesistius poutassou Blue whiting 0.6 7 210 240
Microstomus kitt Lemon sole 8.4 94 110 280
Mullus surmuletus Striped red mullet 23.6 552 50 290
Mustelus asterias Starry smooth-hound 60.6 35 530 1000
Myoxocephalus scorpius Sculpin 0.7 20 100 160
Pholis gunnellus Butter fish 1.0 40 150 190
Platichthys flesus Flounder 0.5 2 290 300
Pleuronectes platessa Plaice 42.3 577 100 420
Pollachius virens Saithe 1.0 3 290 340
Pomatoschistus spp. Sand gobies 0.1 70 30 70
Raja brachyura Blonde ray 37.2 47 340 790
Raja clavata Thornback ray 25.0 32 240 750
Raja montagui Spotted Ray 18.9 31 340 530
Sardina pilchardus Pilchard 144.1 1523 40 390
Scomber scombrus Mackerel 118.5 831 130 400
Scophthalmus maximus Turbot 1.8 3 290 340
Scophthalmus rhombus Brill 0.7 1 340 340
Scyliorhinus canicula Lesser-spotted dogfish 254.7 673 240 690
Sepia officinalis Common cuttlefish 1.0 2 150 170
Sepiola atlantica Atlantic bobtail squid 0.0 2
Solea solea Sole 11.2 157 140 410
Spondyliosoma cantharus Black sea bream 1.5 4 220 290
Sprattus sprattus Sprat 107.1 14182 55 145
Taurulus bubalis Sea scorpion 0.1 1 150 150
Trachinus draco Greater weever fish 6.9 35 210 420
Trachurus trachurus Horse mackerel 756.6 90641 30 280
Trisopterus esmarkii Norway pout 0.0 4 80 90
Trisopterus luscus Bib 325.6 2891 130 280
Trisopterus minutus Poor-cod 22.8 506 70 200
Zeus faber John dory 5.8 19 220 270