reading

Cover
Title Page
List of Contributors
Foreword
Acknowledgements
1 The Marine Environment
1. 1.1 Marine Habitats
2. 1.2 The Coastal and Fjord Biotopes
3. 1.3 Physical Characteristics of the Pelagic System
4. 1.4 Temperate Marine Communities – Environment and Organisms
5. References
2 Planning Marine Field Studies
1. 2.1 Survey and Sampling Design
2. 2.2 Littoral Survey Design
3. 2.3 Benthos Survey Design
4. 2.4 Oceanic Survey Design
5. 2.5 Ecological Process Studies
6. References
7. Further Reading
3 Sampling Gears and Equipment
1. 3.1 Sampling Organisms
2. 3.2 Sampling the Physical Environment
3. 3.3 Suitability of Equipment in Given Habitat Types
4. References
4 Sorting Specimens and Preserving Materials
1. 4.1 Sampling Diary
2. 4.2 Sorting and Preserving Littoral Collections
3. 4.3 Sorting Zooplankton
4. 4.4 Sieving and Sorting Benthic Samples
5. 4.5 Fish and Nekton
6. 4.6 Data Records
7. 4.7 Samples for Storage
8. References
5 Data Analysis
1. 5.1 Scripts
2. 5.2 Setting the Working Directory
3. 5.3 Importing Data
4. 5.4 Working with Data
5. 5.5 Data Exploration and Statistical Testing
6. References
Index
End User License Agreement

List of Tables

Chapter 01
1. Table 1.1 Plankton size classes.
Chapter 03
1. Table 3.1 Dimensions of different plankton nets. Length of forward cylindrical part (h1) and conical after part (h2). See Figure 3.13 for schematic showing cylindrical and conical sections.
2. Table 3.2 Overview of sampling gears and equipment and the habitats in which they are used.
Chapter 04
1. Table 4.1 General description of maturity stages of fish (Mjanger et al. 2016).
2. Table 4.2 Condition of gall bladder and hind guts used to differentiate between empty and regurgitated stomachs of fish.
Chapter 05
1. Table 5.1 Typical structure of a multivariate data set prepared for ordination analysis. Note that the first column lacks a header name. This column represents row names, which are the different sites investigated. The numbers in each column represent percent cover of a given species within a given site.
2. Table 5.2 A key for how to choose which method of ordination to use.
3. Table 5.3 An example of applying the Bray‐Curtis dissimilarity index to a hypothetical case with samples from one square quadrat plot at each station. According to Equation 5.1, D_jk = 140/(165 + 145) = 0.45.
4. Table 5.4 The values of Table 5.3 after a fourth root transformation. This homogenizes values to give a more accurate picture of differences between the stations. Recalculation of D_jk changes it to 0.20.
5. Table 5.5 A Bray‐Curtis dissimilarity matrix showing the calculated pairwise dissimilarities between samples taken at four sites (four subsamples at each site), where two of the sites are sheltered from waves (s) and the other two are exposed (e).
6. Table 5.6 Part of the example data set showing sites as row names (first column), where the first and second numbers represent site and subsample number, respectively. The letter at the end on each row name represents site type, where “e” means wave exposed and “s” is sheltered site. The rest of the data are the species abundance matrix.

List of Illustrations

Chapter 01
1. Figure 1.1 Topographic chart of the North Sea.
2. Figure 1.2 Part of the coastline of Western Norway, showing the complex bathymetry characteristic of fjords and many other coastal systems.
3. Figure 1.3 The three “universal zones” recognized by Lewis (1961), showing the zones in a gradient from extreme shelter (right) to strong wave‐exposure (left). The area between the dotted lines is the intertidal area between extreme high and low water level (EHWL, ELWL). The littoral zone is composed of the splash zone (littoral fringe) and the eulittoral zone, where the limits are set by zone‐forming organisms. The littoral zone is defined as the area inhabited by organisms influenced by the tidal cycle and is separated from the sublittoral zone. The width of the littoral zone is strongly extended towards the wave‐exposed side due to higher waves and a much wider splash zone. In addition, the limits are shifted upwards on the wave‐exposed side due to the more‐or‐less constant wave action.
4. Figure 1.4 An early map illustrating the Norwegian Coastal Water (yellow and green) between the Norwegian coastline and the oceanic North Atlantic Water (blue) (Hjort and Gran, 1899).
5. Figure 1.5 A transect from the head of a fjord (right) to an oceanic location (left) showing (a) the three main water masses: local brackish water, Norwegian Coastal Water (NCW), and North Atlantic Water (NAW). A summer situation is indicated in (b). The arrows indicate the gradients in salinity, temperature, and density stratification; broken lines indicate isoclines for the three variables. Fresher water contains higher concentrations of CDOM with terrestrial origin causing isolumes, like the euphotic depth, to shoal toward locations more affected by freshwater. Depth of euphotic zone and Mesopelagic isolume is indicated in (c).
6. Figure 1.6 Difference in vertical distributions of (a) salinity, (b) temperature, (c) density, (d) phytoplankton, and (e) nutrients at a coastal (grey) and an oceanic location (black) in an idealized steady state summer situation.
7. Figure 1.7 Effects of coastal winds on circulation patterns of coastal areas and fjords. Northerly and southerly winds cause (a) upwelling and (b) downwelling with opposite circulation patterns in the intermediate layer (the water layer between the brackish water and the sill depth) of a fjord.
8. Figure 1.8 Measurements of downwelling irradiance with a spectroradiometer in the Norwegian Sea. Note that most of the light that remains at large depth narrows to around 480 nm.
9. Figure 1.9 The intertidal community at a locality with high degree of wave exposure. The shore is dominated by barnacles and small, turf‐forming algae.
10. Figure 1.10 The intertidal community at a sheltered locality with low degree of wave exposure. The shore is dominated by large brown algae.
11. Figure 1.11 A typical sublittoral habitat illustrating trophic relations and links to the physical environment.
12. Figure 1.12 Classification of fish communities by depth using the Norwegian Sea shelf slope summer situation as an example. .
13. Figure 1.13 The helmet jelly Periphylla periphylla.
14. Figure 1.14 The alien ctenophore Mnemiopsis leidyi was first observed in the North Sea in 2005. .
15. Figure 1.15 (a) A typical pelagic fish is the sprat (Sprattus sprattus). (b) Pictured are some specimens of the local Lustrafjord population caught in the Fjøsne Bay, September 2016.
16. Figure 1.16 Typical mesopelagic organisms from fjord areas. Pictured are specimens caught in Masfjord. (a) Left; Maurolicus muelleri and right; Benthosema glaciale. (b) Top; Pasiphaea spp., middle; Meganyctiphanes norvegica, and bottom; Sergestes spp.
Chapter 02
1. Figure 2.1 Still images from a video equipped ROV of two typical invertebrate inhabitants of a west‐Norwegian fjord. (a) The squat lobster Munida sarsi in a soft bottom habitat. (b) The sea star Hippasteria phrygiana on the rocky substrate of an undersea mountain.
2. Figure 2.2 Northeast Atlantic mackerel (Scomber scombrus) swimming inside a pelagic trawl.
3. Figure 2.3 Map showing the ten strata used for estimation of mackerel biomass during the International Ecosystem Summer Survey in the Nordic Seas (IESSNS).
4. Figure 2.4 Side view of the Multpelt 832 as deployed from a vessel. The Multpelt 832 is rigged with 350 m of warp, 80 m of sweeps, buoys, a kite, and 400 kg chain weights on each lower wing.
5. Figure 2.5 Standard rigging of the GOV trawl for use in the IBTS North Sea surveys. Modified from the IBTS survey manual (ICES, 2015a).
6. Figure 2.6 MIK‐M trawl for use in the North Sea IBTS first quarter surveys. The depth sensor (orange sensor) is visible on the metal ring. Small nets at side of MIK net are used to collect fish eggs. The flow meter is hanging in the center of the net (only the cord is visible).
7. Figure 2.7 Example of a CTD rosette with 11 water collection canisters.
8. Figure 2.8 Example of Type I and II diel vertical migration. Type I diel vertical migration describes the movement of organisms from a bright surface environment to darker, deeper depths during daytime, while type II diel vertical migration describes the movement of organisms from a darker to a brighter environment during daytime.
9. Figure 2.9 Schematic showing the various types of equipment used to sample the water column. (1) An upward facing EK60 38 kHz transducer located on the bottom of the fjord at 390 m depth sent sound waves toward the surface. This was connected to (2) a laptop on land, where (3) echograms could be followed in real‐time. Data from (4) the hull‐mounted echosounder was used to visualize acoustic targets/scattering layers at different depths. (5) A pelagic trawl combined with a MultiSampler was used to verify the species composition of the acoustic signals/targets (a, b, and d). (6) A plankton sampler collected depth‐stratified plankton samples (c). (7) A CTDO recorded hydrographic data throughout the water column. (8) A light sensor measured radiation every 15 minutes. Large predatory fish (d) were also caught with rod and reel.
10. Figure 2.10 Movement of fish species in the water column over a 24‐hour period; species in each layer were predominantly, from top to bottom, larvae, juvenile and adult pearlside (Maurolicus muelleri). (a) Larvae, juveniles and adult pearlside are distributed at progressively deeper depths during daytime and aggregate in the upper water layer between dusk and dawn (type I migration). (b) Juvenile pearlside display nocturnal descents from the surface to approximately 50 m depth after dusk, while the deeper located adult fish (150–200 m) stay at depth throughout the diel period, with only a small proportion performing reverse diel migrations to 120 m. (c) Juvenile fish migrating to the surface stop their migration at different depths and descend again.
11. Figure 2.11 Migration of pearlside under different levels of light. (a) (upper panel) The arrival to and (lower panel) departure from the surface at civil twilight end and civil twilight start, respectively. Lines indicate the timing of the end and start of civil twilight, while symbols indicate when pearlside arrived or departed from the surface layer in a particular month. (b) Relationship between surface irradiation and SL depth over two days. The July 10 (blue triangles) was a clear day with high surface irradiation, while July 13 (circles) was overcast and had much lower irradiation recordings. Pearlside were distributed at deeper depths on July 10 compared to July 13.
12. Figure 2.12 Diving channel and submersible cage setup. The channel was 500 cm in length and consisted of black knotless netting (20 mm mesh size). The channel was stabilized by eight rings which had a diameter ranging from 70 cm in the top (1) to 55 cm on the bottom (2). Directly above the lower end of the channel, a round net cage was attached, which consisted of black knotless netting. The cage was stabilized by two rings (90 cm in diameter (3)), which were 80 cm apart from each other, that is, the approximate cage height was 80 cm. At the top of the cage mouth was 75 cm of excess netting, which could be closed by a mouth rope (4) that was drawn through the net meshes. The cage was attached to the diving channel by putting the excess net over the lowest ring of the channel and tightening the cage mouth using the mouth rope (4) to a diameter of 30 cm. At the bottom of the cage, a cage retrieval rope (5) with a 3 kg weight (6) was attached (90 cm of rope between cage bottom and weight). Additionally, a 1.5 kg weight (7) was fixed 1 m from the 3 kg weight to buffer potential wave action after cage submersion. The cage could be retrieved to the surface by pulling on an extension (8) of the mouth rope that closed the cage mouth. After detachment of the cage from the channel, a small trawl float (9) was attached to the mouth rope to keep the cage upright after submersion. When the cage was lowered to the bottom, the retrieval rope was held at the surface using a large trawl float. This figure is reprinted with permission from Ferter et al. (2015a).
13. Figure 2.13 The occurrence of external barotrauma signs in angled cod from 0 to 90 m for each 10 m depth interval. As several individuals had more than one barotrauma sign, the sum of occurrence adds up to >100%. This figure is reprinted with permission from Ferter et al. (2015a).
14. Figure 2.14 The probability of (a) swimbladder rupture and (b) gas bubble formation in the venous blood system (venous gas embolism) in angled cod with increasing capture depth. Points represent individual fish presence (1) and absence (0) data (many points overlap). The continuous lines show the model predictions and the dotted lines the range of the 95% confidence intervals. This figure is reprinted with permission from Ferter et al. (2015a).
Chapter 03
1. Figure 3.1 A schematic figure showing macroalgal zones in an intertidal, demonstrating the principles for measuring vertical levels and zones in relation to Chart Datum (0‐level or LAT).
2. Figure 3.2 An example of a steel quadrat and grid overlay used for sampling.
3. Figure 3.3 Use of sample quadrats in the field. The sample frames are positioned by attaching the underlying frame to two permanently fixed bolts in the rock.
4. Figure 3.4 A remotely operated vehicle (ROV).
5. Figure 3.5 Illustration of a pelagic trawl and its components. For some pelagic trawls, lift is created along the headrope by a kite or additional cable connected to the vessel.
6. Figure 3.6 Illustration of a bottom trawl and its components. Mud clouds created by the otter boards (trawl doors), lower bridles, and footrope serve to herd fish into the opening of the trawl.
7. Figure 3.7 Beam Trawl.
8. Figure 3.8 (a) DeepVision system placed between the trawl and codend of a pelagic trawl. (b) Example of a 100 cm Atlantic cod (Gadus morhua) taken by the DeepVision system. Precise time and position are indicated in the white overlay text.
9. Figure 3.9 Vertical position, length, and density of fish in the water column as measured by DeepVision system, overlaid on an acoustic echogram. Trawl path is indicated by the thin gray line, while location of fish is by colored circles with diameter scaled to indicate the number of fish passing per second. Seabed is indicated by the sloping red band. Images above the figure are the specific fish indicated on the depth profile.
10. Figure 3.10 Schematic view of the MultiSampler. Insets illustrate the circled area and show the MultiSampler in (a) open position, no catch retained; (b) first codend activated; and (c) first codend closed, trawl being flushed prior to activating second codend.
11. Figure 3.11 Deployment of a beach seine.
12. Figure 3.12 Retrieval of a plankton ring net.
13. Figure 3.13 (a) Schematic of a WP‐2 cylindrical‐conical net (mesh size 200 µm, mouth opening 0.25 m²).
14. Figure 3.14 MOCNESS in operation. The net is towed obliquely behind the ship at a 45° angle. In this schematic, the eight nets at the bottom have all collected samples at various depths and are now closed; the top net is sampling the shallowest depths on its way back to the surface. The codends at the ends of the nets hold the samples after the nets have filtered plankton from the water.
15. Figure 3.15 Deployment of the MOCNESS. The first net (net 0) is kept open while lowering to maximum fishing depth. When the maximum sampling depth is reached, net 0 is triggered to close, and net 1 will open for the ascent.
16. Figure 3.16 Examples of (a) a 0.125 m², 5 nets MultiNet.
17. Figure 3.17 (a) RP sledge; (b) Schander sledge; (c) Sneli sledge.
18. Figure 3.18 An Agassiz trawl on deck.
19. Figure 3.19 (a) Triangular dredge, (b) Blue‐mussel dredge.
20. Figure 3.20 Sampling of the sediments using a grab.
21. Figure 3.21 A multicorer on deck.
22. Figure 3.22 Various water samples. (a) The original Nansen sampler with housing for thermometers. (b) The Van Dorn sampler with messenger weight. (c) The newer generation Niskin bottle, shown with lids open, with housing for thermometers on the backside. (d) Ruttner sampler in open position.
23. Figure 3.23 An example of a Multi Water Sampler System, with attached CTD.
24. Figure 3.24 Schematic showing gillnets and entangling nets. (a) Gillnets can be set at the bottom or midwater, where weights and floats keep the net open, upright, and at the correct depth; buoys at the surface are then used to find the nets for retrieval. Drift nets are set at the surface. (b) Entangling nets operate by capturing fish as they attempt to swim through the net. (c) Schematic showing the weights along the groundrope and floats along the headline, which keep the net fully open when set.
25. Figure 3.25 An example of a lobster and crab pot. The open holes illustrate escape openings for undersized lobster.
26. Figure 3.26 An example of a cod fyke net. The leading net is to the left and the net bag with funnels is to the right.
27. Figure 3.27 Schematic illustration of how an echo sounder works. (a) sound is directed downwards from a transducer located on the hull of a vessel, some of which is reflected back to the transducer by organisms, such as fish schools in the water column or located near the water bottom, as well as the seabed.
28. Figure 3.28 Echogram from Nordkapp of predominantly single targets at relatively low density, where every horizontal mark is an individual fish. The individual marks within the bottom 150 m are Atlantic cod. The small schools near the surface are capelin and are made up of many individuals.
29. Figure 3.29 Example echogram of herring in Ofotfjord. The green to red colored targets from 50 to 150 m depth are herring and the faint (blue) single targets at deeper depths are blue whiting. The echogram shows five nautical miles (9.3 km), where individual miles are marked with vertical lines. After safely removing the bottom echo (red line), the echo integral for mile no. 4 is 53 016 (including the blue whiting) and 53 000 without the blue whiting.
30. Figure 3.30 A Kongsberg Seaglider on deck, ready to be launched into the Norwegian Sea.
31. Figure 3.31 Main principle of ocean color remote sensing by a satellite. Some part of visible light is scattered by the atmosphere and some is reflected at the sea surface. These signals can be corrected for, thereby allowing the “water‐leaving radiance” to be the signal containing information about water constituents.
32. Figure 3.32 A false‐color picture of the global annual mean of chlorophyll a (mg m³) based on satellite remote sensing from Aqua‐Modis (NASA), Ocean Color web, http://daac.gsfc.nasa.gov./MODIS/
33. Figure 3.33 Chlorophyll a concentration (mg m³) in the North Sea and Skagerrak based on satellite remote sensing measurements from European MERIS (ESA), representing May 8 2008.
34. Figure 3.34 (a) A CTD rosette with mounted water samplers and a Lowered Acoustic Doppler Current Profiler (LADCP) mounted on top. (b) One LADCP is mounted to face downwards, while (c) the other points upwards.
35. Figure 3.35 Visualization of currents using VMDas. (a) Graph showing magnitude (red) and direction (green) of current as a function of depth. (b) Graph shows data quality as a function of depth. (c) Plot of ship track showing the current velocity vectors along the ship track at three separate depth bins. (d) Same as plot in bottom left, after setting bottom track as the reference velocity; minor deviations in track and current velocities may be apparent because the reference velocities have been subtracted from the profile before output.
36. Figure 3.36 (a) A boat mounted ADCP transducer surface with four transducers. The direction of two of the beams are along‐ship and two are across‐ship. (b) Simple description of the Doppler effect.
37. Figure 3.37 Two types of ADCPs typically attached to deployed subsurface moorings. (a) An Aanderaa SeaGuardII DCP Black.
38. Figure 3.38 Illustration of current measurement solutions and mounted ADCPs attached to floating and subsurface buoys and a platform on the seabed.
Chapter 04
1. Figure 4.1 Procedures for processing zooplankton samples. See text in Box 4.1.
2. Figure 4.2 (a) A simple vacuum pump filtering system used for processing small zooplankton samples for total biomass estimation. (c) Removing a filtered sample from the vacuum pump. (b and d) Examples of how to label zooplankton samples after filtration.
3. Figure 4.3 Using seawater to sieve a sample through two different size‐fraction sieves stacked on top of each other, where the largest mesh size is placed on top.
4. Figure 4.4 Sampling with a MultiSampler. (a) Preparing to set a pelagic trawl fitted with a MultiSampler and 3 codends. (b) The MultiSampler trawl hauled on deck. (c) A typical mesopelagic catch in Masfjord, western Norway. (d) A night catch from three codends; the catch in T1 from the deepest mesopelagic layer, in T2 between two mesopelagic layers, and in T3 from the shallowest mesopelagic layer.
5. Figure 4.5 A typical catch from a bottom trawl from 490 m depth in Masfjord, western Norway. (a) The trawl after being hauled onboard. (b) The trawl catch on deck, prior to sorting into baskets of single species. (c) Weighing the baskets of individual species in the wet lab and recording the data. (d) A roundnose grenadier (Coryphaenoides rupestris) on a measuring board. Grenadier tails are fragile and easily break off in the trail, therefore the standard length measurement is from the tip of the snout to the posterior edge of the dorsal fin.
6. Figure 4.6 A typical catch from a bottom trawl from 90–150 m depth in the North Sea. (a) The catch is hauled on deck and placed into a large container before entering the fish lab. (b) The catch is placed into baskets (still unsorted at this stage) to be weighed; (c) the catch is sorted and measured; (d) a basket containing only saithe (Pollachius virens). (e) A hake (Merluccius merluccius) on an electronic measuring board.
7. Figure 4.7 How to subsample and measure the catch of a mesopelagic community.
8. Figure 4.8 Sorting the mesopelagic catch in Masfjord. (a) A typical catch from a 5–10 min haul. (b) The most often caught species: pearlside (Maurolicus muelleri), lanternfish (Benthosema glaciale), Sergestes spp., Pasiphaea spp., krill (Meganyctiphanes norvegica), and the helmet jellyfish (Periphylla periphylla). (c) Sorting a subsample. Counting of (d) pearlside and (e) Sergestes spp. by placing in piles of 10 individuals. (f) Measuring individuals and recording standard length (SL).
9. Figure 4.9 How to measure the length of various fish species at the Institute of Marine Research, Norway.
10. Figure 4.10 Large saithe (Pollachius virens) are found in the pelagic as well as just above the seabed in deep west Norwegian fjords. (a) A 5 kg saithe caught by hand‐line at 90 m depth, immediately below the shallowest mesopelagic sound scattering layer. (b) The individual with its belly opened and the stomach removed. (c) The stomach of the fish was packed with pearlside (Maurolicus muelleri).
11. Figure 4.11 An example of a station form used during the field course in Masfjord, Norway. The top part of the form contains station information, while catch information is recorded at the bottom.
12. Figure 4.12 (a) Example of label information when freezing a sample. (b) Frozen samples should be flat packed and the label must be visible through the plastic bag.
13. Figure 4.13 An example of a length measurement form used during the field course in Masfjord, Norway. Measurement units can be in either mm or cm. One form is used for each species. Data should also include the number and total weight of the measured fish.
14. Figure 4.14 An example of a form to use for individual biological data for large fish that feed on mesopelagic organisms during the field course in Masfjord, Norway.
Chapter 05
1. Figure 5.1 Example of how to obtain the path to a directory (first red line) and set a new working directory (second red line). Note that on MacOS or Linux, a forward slash instead of double or single backslash must be used. A forward slash will also work with Windows versions of R. A forward slash is recommended for producing platform independent syntax. Thus, a more general syntax for the second red line is: setwd(“C:/Documents and Settings/Administrator/My Documents/rwork”).
2. Figure 5.2 A PCA analysis plot from the data shown in Table 5.1. PCA plots are interpreted as follows: sites that are close together in the diagram have a similar species composition; sites 4 and 5 are quite similar. The origin (0,0) is species averages. Points near the origin are either average or poorly explained. Species increase in the direction of the arrow and decrease in the opposite direction. Distance from the origin reflects the magnitude of change. Variables near each other are similar. Angles between arrows approximate their correlations: 90° = 0 correlation, <90° = positive correlation, >90° = negative correlation, and 0° implies correlation = 1.
3. Figure 5.3 A dendrogram showing a hierarchical clustering of sampling sites 11e–24e (samples from wave exposed sites) and 31 s–44 s (samples from sheltered sites) based on a Bray‐Curtis dissimilarity matrix. Connections made at values close to 0 indicate sample sites have a high degree of similarity (“low degree of dissimilarity”).
4. Figure 5.4 A MDS plot showing distances between sampling sites 11e–24e (samples from wave exposed sites) and 31 s–44 s (samples from sheltered sites) on a two‐dimensional plane. The elliptical borders show cluster overlays from the separate cluster analysis with dissimilarity less than 0.6. For 34 s and 44 s the ellipse has collapsed since there are only two data points in this cluster.
5. Figure 5.5 Environmental data from CTD station 0683. The panels show profiles of temperature, oxygen, salinity, and light (PAR) over depth (m). The CTD records pressure (dbar) which is then used as the depth. Note that the depth is not on the same scale for the PAR curve because the light measuring unit cannot measure PAR values <10⁻¹².
6. Figure 5.6 The density of zooplankton (measured in dry weight per cubic meter) at different depths and time of day, day and night. This figure was made using the code in (2) Create a simple plot of the data. Open and solid circles represent day and night samples respectively.
7. Figure 5.7 The density of zooplankton (measured in dry weight per cubic meter) at different depths and time of day, day and night. The lines show mean density at each depth, while symbols are the density of zooplankton in each sample.
8. Figure 5.8 CPUE (kg per hour) for all fish species caught by hook‐and‐line.
9. Figure 5.9 Median depth (thick black line) and depth range of echo‐layers depending on time of day. The left panel shows the median depth (thick line), the upper and lower quartiles (upper and lower borders of the box), and the minimum and maximum values (upper and lower whiskers). Note that the surface of the water (0 m) is at the bottom of the y‐axis. The right panel shows the same information in a slightly different way: 0 m is at the top of the y‐axis, boxplots from day sampling are white and night are shaded grey.
10. Figure 5.10 Size of M. muelleri caught in the upper and lower echo‐layers during the day and night.
11. Figure 5.11 Total biomass as catch per hour (kg) in each echo‐layer, lower and upper, during day and night. The sample size for each group, left to right, is 3, 2, 3, and 2 hauls for each of the layers.
12. Figure 5.12 The proportion of total biomass of each species caught during day and night in the upper and lower echo layers. Data have not been standardized to a similar unit of effort before plotting.
13. Figure 5.13 The proportion (in numbers) of each species caught during day and night in the upper and lower echo layers. Data have not been standardized to a similar unit of effort before plotting.
14. Figure 5.14 Catch (kg) per hour at three depth ranges by species from pelagic trawling during the day (white bars) or night (shaded bars). Depth ranges were 0–100 m, 100–200 m, and 200–300 m.
15. Figure 5.15 Catch (numbers) per hour at three depth ranges by species from pelagic trawling during the day (white bars) or night (shaded bars). Depth ranges were 0–100 m, 100–200 m, and 200–300 m.
16. Figure 5.16 Catch per hour of B. glaciale (biomass) from day (white) and night (shaded) for three depth ranges: 0–100 m, 100–200 m, and 200–300 m. Solid black lines represent median values.
17. Figure 5.17 Length (mm) of B. glaciale from day (white) and night (shaded) for three depth ranges: 0–100 m, 100–200 m, and 200–300 m. Solid lines indicate median values.
18. Figure 5.18 Abundance (g, numbers) of five prey items eaten by saithe and pollack.
19. Figure 5.19 Catch (kg per hour of trawling) of species captured by bottom trawls.
20. Figure 5.20 Catch (number of individuals per hour of trawling) of species captured by bottom trawls.
21. Figure 5.21 Boxplots showing the size range (mm) of all species caught using bottom trawls.
22. Figure 5.22 A map of the North Atlantic showing bottom trawling locations as red dots.
23. Figure 5.23 A map of Norway with the location of Masfjord shown as a red dot.
24. Figure 5.24 Low resolution map of Masfjord created with the sp package. The four sampling stations are marked as red numbers.
25. Figure 5.25 Map of Masfjord created with the RgoogleMaps package, which uses maps from Google Maps. The four sampling stations are marked as red numbers.

Marine Ecological Field Methods

A Guide for Marine Biologists and Fisheries Scientists

List of Contributors

Foreword

Acknowledgements