ICES C.H. 1986/G:58 Ref. Pelagic Fish Committee

FISH COHHUNITIES OF THE NORWEGIAN OEEPS: SPEelES COHPOSITION ANO OISTRIBUTIONAl PATTERNS.

by

Odd Aksel Bergstad Department of fisheries biology. University of Bergen. Norway. \ P.O.Bo~ 1839. N-5011 Bergen-Nordnes /

ABSTRACT

Preliminary results from studies of the fishes inhabiting the Norwegian Oeeps and bordering slopes are presented. including accounts of species composition and distributional patterns.

The Norwegian Oeeps proper is a nursery and feeding area for a number of species. mainly species which are abundant along the upper continental slopes of the North Atlantic and the deep fjord environments. The more abundant include the greater argentine. Argentina silus. blue whiting. Hicromesistius poutassou. and in the Skagerrak. roundnose grenadier. Coryphaenoides rupestris.

Above the 200m isobath the species composition resembles the one found in adjacent coastal areas or on the North Sea plateau. The more abundant demersal species are Norway pout. Trisopterus esmarkii. saithe, Pollachius virens, and haddock, Helanogrammus aeglefinus.

Data from hydroacoustic surveys and bottom trawl surveys suggest pronounced seasonal changes in distributional patterns of some species, notably the greater argentine and blue whiting. •

INTRODUCTIOH

The Norwegian Deeps, with depths in the range 275-700 m, represents a major topographical feature of the comparatively shallow and even North Sea (Fig.1). As such, it has a pronounced influence on watermass distributions and current patterns in the eastern Horth Sea, the Skagerrak and in the Norwegian Coastal waters (Furnes et al. 1986). From fishery data and a few regional studies it is known that the Horwegian Deeps is inhabited by a .fish fauna differing rather markedly from the one found in the bordering shallow waters (Hjort and Ruud 1938; Sahrhage 1964, Aker et Al. 1966, Hamre and Hakken 1970, 1971, Thomassen 1974, Jakupsstövu 1974, lhorsen 1979), including exploitable stocks of greater argentine (Argentina silus), blue whiting (Micromesistius poutassoul, and roundnose grenadier, (Coryphaenoides rupestris). Moreover, the western and southern slope offers feeding grounds for 1arge proportions of the Horth Sea and Skagerrak stocks of saithe (Pollachius virens) and Norway pout (Trisopterus esmarkii) (Poulsen 1968, Reinsch 1976, Lahn-Johannesen et a1.1978, Smedstad 1985) and 1arge1y unknown fractions of the stocks of other species ~ (Cod, Gadus morhua), whiting (Merlangius merlangiusl, herring (Clupea'" harengus), mackere1 (Scomber scombrus), and others).

On this background, the Department of Fisheries Biology of the University of Bergen, Norway, initiated in January 1984 a 3-year study of,the fish.resources of the Norwegian Deeps and bordering slopes. The main objectives of the project is through collection of data on species composition, distributiona1 patterns and feeding eco10gy, to obtain a more comp1ete description of the resources and their ecology. Of particu1ar interest is information which wou1d improve our under­ standing of the significance of the Norwegian Deepsfor the fish populations of the bordering areas, i.e. the North Sea plateau and the coasta1 waters of Norway and Denmark.

This paper is a high1y pre1iminary summary of information on species composition and distributional patterns; with some emphasis on the demersa1 fishes, from surveys in 1984,1985 and the sp~ing of 1986.

MATERIAL AHO METHOOS

The cruises on which data were collected are listed in lable 1. Oue to rather strict limitations on vessel time, area coverage and the number of trawl hauls per survey have varied, and from 1985 on it was decided to limit trawling effort on all ·H~kon Mosby· surveys to four subareas (Fig. 1, hatched areasl. Bottom trawl stations were located at random in each subarea within three depth strata: 100-180 m, 185-235 m, and >240 m. The number of stations per subarea was decided from 1984 data which indicated that among-haul variation in species composition was greater along the slopes. than in the deep areas. Thus, allocation proportional to area was abandoned, and more hauls were allocated to the two upper depth strata. The latter has been only partially successful due to unfavorable bottom substrate, obstructions of all kinds or the steepness of the slopes. In general less attention was given to coastal areas than to the western and southern slope, particularly in the two northern subareas.

The ·Michael Sars· surveys in October (Table 1) were part of the Pandalus program run by the Institute of Marine Research, Bergen (Smedstad and Tveite 19851. Trawl stations from these surveys were incorporated in the data to improve spatial and seasonal coverage. Similarly; scattered data from other ships were included whenever ( .~ 3 . "

possible.

On all theNHAkon HosbyN cruises a commercial shrimp trawl was used for bottom trawling (Br0drene Selstad AIS, Hll0Y, Norwayl. On the other ships a Campel 1800 shrimp trawl was applied. Data for both trawls and accessories are given in Table 2. The fishing power and selection characteristics of the different vessels are assumed accept­ ably similar based on measurements of vertical opening and wingspread during operation, hence, no corrections were applied on the catch data. A standard haullasted 1 h at a towing speed of 3.0 knots. The results were corrected in cases where deviations from these standards oceurred.

Hydroacoustic records were, made continuously on all surveys with ,echosounders and echointegrators (Table 31. The aim was to obtain information on vertical and geographical distribution of fish and plankton rather, than absolute abundance estimation. Based on the characteristics of the echo traees and trawl sampling, ineluding aimed midwater trawling, the deflection values per (n. mile)~ were assigned to the following categories:' Nunidentified planktonN, Neuphausid­ Haurolicus assoeiationN, Npelagic blue whiting N, Ngreater argentineN or Nmixture of greater argentineand roundnose grenadierN, Nother pelagic fish N and Ndemersal fishN. Some hydroacoustic data from other vessels crossing the Norwegian Deeps have,been included, although they generally suffer,from the lack of identification of scatterers by trawl samples.

The, trawl sample: (or a random subsample) was sorted to species, and total cateh of each speeies by numbers and weight '(to the nearest hgl was registered. Length frequeney distributions were reeorded for every species,:while individual data (total length (em or 1/2 cm), ungutted weight (to the nearest 10g), :sex, index of maturity (macroscopic examinationl, index of stomach filling) and otoliths were kept for abundant large gadids, the greater argentine' and same herring. Individually tagged stomaehs of most regularly oecurring species were fixed in 4% buffered seawater solution of formaldehyde, while small fish (total'length < 15-20 cm) werefixed ungutted after injeetion of fixative in the body cavity.

Hydrographical profiles were made by Neil-Brown CTD-profiler following every trawl haul or along standard transeets workedby the Institute of Harine Research, Bergen (Lj0en 1980). Additional data was gathered from other surveys i~ the same or adjaeent areas at the same time.

RfSULTS

Distributional patterns.

Hydroacoustic data. The echogram reproduced in Fig.2'illustrates a ,commonly observed daytime distributional pattern of pelagic or bentho-pelagic seatterers in the'Norwegian Deeps. (Hamre and Nakken 1970, 1971). Two,well developed scattering layers are seen, and the .. lower touches the bottom along the western slope. Hidwater trawl hauls aimedat the ~pper layer gi~e catches of a variabi~ mixture of HOllers pearlsides and euphausids and sometimes a few juvenile saith~. lumpsuckers~ norway pout and blue whiting (Table '4). Catches from the lower layer'contain juvenile blue whiting and usually small numbers of velvet belly, greater argentine and Hüllers pearlsides and euphausids (Table 4). (The euphausids and pearlsides can perhaps be seen as contamination in these catches since the ascending trawl must necessarily pass through the upper layer). In the summer hauls a few o-group gadids (haddock. whiting, norway pout) are caught in both layers as is mackerel and horsemackerel.

A pronounced diurnal'vertical migration is seen forboth scattering layers. The pearlsides form nighttime near-surface layers which are sometimes too close to the surface to be detectedacoustically. lhe blue whiting typically starts their aseent and' deseent about 1 h before sunset and sunrise, respectively. A night-time dispersion is often seen, and single fish are found throughout the water eolumn, although in greater concentrations in the surface layers.

Numerous single fish traees are typieally observed below the pelagie blue whiting layer and scattered throughout the lower part of the water eolumn. Bottom trawl eatehes indieate that this is greater argentine, but also a number of other species including blue whiting, rosefish. roundnose grenadier and others (se~ next seetion).

Fig. 3 shows an echogram'from the deeper parts of Skagerrak in Harch. A bottom trawl eateh on this loeation eontained greater argentine (931 ~ kg), roundnose grenadier (419 kg) and blue ling (56 kg). Similar eoneentrations, although seldom as' dense, were observed over most areas of the Skagerrak with bottom depths greater than 350-400 m. Typically, numerous single fish traces are seen above the main near­ bottom concentrations up to about· 300 m depth. lable 4 (lwo last catches) gives species composition of catches by midwater trawl at 300-330 m and shows that roundnose grenadier is distributed weIl above the bottom at this time and is probably numerous eompared with the other species (i.e. blue whiting and greater argentine).

Oue to the limitations. on the area coverage,' it'has never been feasible to map the geographical distribution of acoustic scatterers satisfactorily. In Fig. 4, however, defleetion va lues per (n mile~ along selected transects crossing the' Norwegian Deeps (see charts below). are givenfor two winter-spring situations and one summer situation. Looking at total values only, a strong difference between winter and summer abundance is seen. In the summer the blue whiting and the Haurolieus - euphausids mixture is found along the entire western and southern slope and may form very dense concentrations~ which reach far into the deepwater areas in a coastward direction. Horeover, ,the greater argentine which in HaOch-APril is concentrated in the deepest parts north of about 61 30'N (Johannesen and Honstad 1985, Own data) and in the Skagerrak, is found in all areas.

In Harch-April dense scattering layers. as shown in"Fig. 20 have virtually never been observed south of the Viking Bk. area (N61 N), and the abundance of blue whiting and Haurolicus is'generally very low. Host deep-pelagic scatterers in Skagerrak at this time appear to be roundnose grenadier and greater argentine. Appreciable blue whiting concentrations are. however. found in the northermost areas at this time (Fig.4, March-86; and Monstad and Johannesen 1985).

The cat~gory 'others' in Fig. 4 contains ·plankton"and "bottom fish". Plankton patches are often responsible forthe isolated very high values. while "bottorn fish· is generally a rninor'contributor of variable species composition. Along the upper slope «200 m) "dottom fish"~ may occasionally contribute significantly to thetotal value. Saithe and norway pout are the dominant speciesin these cases. , Trawl data. The acoustic data are virtually uselessf~r ~tudies of the 5

near-bottom fish, hence bottom trawl indices remain theonly sources of distributional information for a number of benthic or benthopelagic species.

Thus far, a total of 67 fish species were represented in the catches (Table 5). Quite a few of these were caught occasionally only and may not be regular members of the Norwegian Deeps' fish fauna. Catch indices for the more regularly occurring species are given in Fig. 5, re1ated ~to season, subarea and depth interval. (Note: data from the October surveys have been included as summer data). Typical length frequency distributions of these and some other species are shown in Fig. 6. Host of' these species occur in all four sUbareas, and abundance changes re1ated to depth (ar same depth-related factar) are more pronounced than geographical patterns.

It is possible, with some loss of detail, to group most of the species into 2 or 3 categories according to depth distribution. The 'upper slope species' show decreasing' abundance with increasing depth, although they may not be entirely absent from the deep areas. Characteristic members are saithe, norway pout, haddock, wh!ting, cod and possibly long rough dab. These species normally show maximum catch • indices -in the two upper depth intervals. Some, like haddoch and whiting, are more restricted to the shallower depth stratum, while norway pout rather consistentlY has maxima in the 180-235 m interval.

The second category could be called 'bottom species' or rather 'lower slope species' and include greater argentine, blue whiting, roundnose grenadier, rosefish, silvery pout, blue ling, rabbit fish, velvet belly and the two more abundant rays, starry ray and Raja lintea. Among these, roundnose grenadier is a deep-water representative, seldom found shallower than about 300 m.

A few species do not fit na turally into category 1 or 2 and could be lumped in a third category of species which either show a different or no consistent pattern. The dogfish and the hake appear to be 'lower slope species' in Harch-April, while they belong in the 'upper slope' category in, August and October. Other relatively abundant species with no consistent depth distribution are the witch and the four-bearded rockling. The impression is, however,' that these really e· belong to category 2. In addition, of course, there are a number of species for which the da ta at hand are insufficient to determine depth distribution with any certainty.

A .further c provisional categorization can be done according to geographical criteria. Again, three categories can be used: 'southerly species', 'northerly species' and 'species showing other patterns'. Some of the 'lower slope species' show a rather clear southerly distribution. Roundnose grenadier is the prime example, but the rays, four-bearded rockling and, to lesser extent, the '. witch, show increasing abundance in a southward and eastward direction. (The witch is highly abundant along the northern slope of' Skagerrak, as described by Hjort and Ruud (1938)). The cod and perhaps long rough dab may belong to this category as well.

The species which show the highest overall abundance in the Norwegian Deeps belong to the 'northerly species' and include saithe, norway pout, blue whiting, rosefish, silvery pout, rabbit fish and velvet be1ly. Haddoch and whiting may also belong to this group, although their abundance in Skagerrak is probably underestimated due to the depth distribution of the hauls. , 6 '

Greater argentine, blue ling, hake and dogfish belong to category 3. These are highly migratory species which show consistent seasonal distributional changes. As noted in the previous section, the greater argentine concentrates in the deepest parts of the area at some time in the winter months, while in August and October it is less concentrated and widely distributed at least in the two lower depth intervals. Itshould be noted, though, that this pattern is typical for the rather old juveniles and mature fish oniy, while the young juveniles are present along the entire slope in both seasons (Fig. 7). A similar pattern is found for the blue ling, the more abundant of the large Lotinae represented in the area. The hake shows a northerly distribution in Harch, although interestingly the juveniles are found further south (Fig. 8). In summer the general abundance is lower, and most catches are from comparatively shallow water in subarea 3 and 4. The dogfish shows a very similar pattern, which reflects known migratory habits (Hjertenes, 1980). It is obvious· that the bottom trawl data are insufficient to map the real distribution of this species. Species composition. • The species composition in bottom trawl catches in terms of mean proportion by numbers and mass is plotted in Fig. 9a and b. Fig. 9a gives data for all species contributing 5 X or more by numbers and/or mass, while species contributing less than 5 X, but equal to or more than 1 X are shown in Fig. 9b. The results are given for different seasons, depth intervals and subareas. Catches below 305 mare plotted separately since they illustrate patterns below the "sill depth- of the Norwegian Oeeps (Furnes et Al., 1986), a boundary of probable distributional significance. In general, differences in species composition increase with distance between strata. Thus, the species composition characteristic of subarea 4 (Skagerrak) is quite different from the one in subarea 1, while differences between adjacent subareas are less pronounced or insignificant.

\ 60ing southwards along the upper slope, a decrease of abundance of saithe and, to some extent, norway pout is primarily responsible for changes in species composition. The differences among subareas 1,2 and. 3 are probably not significant, while the difference between these and subarea 4 is relatively pronounced.

In the Norwegian Oeeps proper (i. e. depth intervals 240-300m and deeper) important differences in species composition'between subareas are consequences of the distributions of major species like roundnose grenadier, blue whiting, greater argentine, rosefish and silvery pout. The extremes are seen in subarea 1 and 4. Rosefish and silvery pout are major species in the northern areas, but very minor species in subarea 3 and 4. Roundnose grenadier, witch, four-bearded rockling and therays show the opposite pattern. Some species are significant in both areas, i.e. blue whiting, greater argentine, norway pout, velvet belly, rabbit fish, but their contribution varies. Blue whiting and norway pout contribute less in the southern than in the northern areas, while the opposite is seen for greater argentine. The species composition as illustrated is at most representative for the demersal fish communities. No quantitative data besides the acoustic estimates are available for the pelagic fishes. The acoustics certaintly illustrate that blue whiting and Hüllers pearlsides are the two major pelagic species. Recent acoustic summer estimates of blue 7

whiting abundance south of 61 0 N are 310 000 and 330 000 tonnes (Anon. 1983, 1984,1985). Herring, sprat, mackerel and horsemackerel are occasionally represented in the bottom trawl catches, but never in high numbers. Herring is more abundant in the winter surveys and is found in the majority of all shallow hauls along the western slope. The concentrations must be low, however, since they can seldom be differentiated on the echogram. In contrast with historical records (Burd 1978), the western slope appears at present as a marginal area for herring from neighbouring shallow areas. The sprat has been recorded in less than ten bottom trawl catches and is by its coastal distribution most likely an insignificant species in the area.

The mackerel is probably a significant member of the pelagic community of the Norwegian deeps. In· recent years, 10 15 000 tonnes of mackerel have been caught in the area, mainly rather elose to the Norwegian coast (Iversen, Institute of Marine Research, Bergen, pers. comm.). The Norwegian Deeps has been thought to offer suitable overwintering areas for the mackerel, and a winter fishery took place on high concentrations in the late sixties (Postuma 1965, Hamre and Nakken 1970,1971, Hamre, 1978). Except in the Mareh survey of 1985, possible deep-water eoneentrations of mackerel have been left undetected. In 1985 quite a few deep catches contained I-group mackerel (Fig. 10). The horsemackerel can be numerous in a few bottom trawl catches in summer. This species is thought to be a summer visitor and is eertaintly more abundant than indieated by the few and seattered reeords obtained.

The lumpsucker and, somewhat surprisingly, the velvet belly are frequently caught by the midwater trawl and must be regular members of the pelagic fauna,as are several o-group fish and the garfish (Be10ne belone). According to commercial catch records and a few sightings, unknown numbers of bluefin tuna are present in summer.

Total bottom trawl catch rates.

Mean total catches per standard haul vs. depth for each season and ~ubarea are shown in Fig. 11. A gradual decreas~ in mean total catch with increasing depth is found in all subareas except No. 4 in summer, and the same tendency is seen in area 2 and 3 in March-April. In subarea 4, the opposite pattern is apparent in both seasons. The • latter 1s caused by the relatively high catches of roundnose grenadier and greater argentine in the two deeper depth strata.

Catch rates alon9 the upper slope are generally significantly lowor in Skagerrak than in the Northern North Sea subareas. The summer level of the catches is, however, h1gher than the March-April level in all subareas. The catch in terms of mass is heavily· influenced by the abundance of large fish, primarily saithe. The great summer abundance of juvenile saithe joined by migrating mature saithe is the primary cause of the seasonal differences in the upper depth interval. 8'

DISCUSSION

A description of distributional patterns of single species' and relative or absolute abundance is a neeessity for further eeologieal studies. Thus since very little quantitative information on these aspeets were available from other sourees. eolleetion' of abundance data was given high priority in the project. Given available vessel time and equipment. bottom trawl sampling and continuous hydroacoustic mapping was ,chosen as a general approach. The aim was to obtain abundance indices for demersal species from trawl sampies. and information on distribution of major pelagic species from the acoustics.

The species and size selectivity of the bottom trawl is largely unknown. but it is likely that small fish. flatfishes and fast-swimming fish le.g. large saithe. mackerei) are underrepresented in the catches. This may have affected the length frequency distri­ butions and the level of the abundance indices and thereby the species composition. However. it is assumed that the eatch indices for a. given species are reasonably proportional, to the abundance in the near-bottom layer. and reflect temporal and spatial variation. Inability to tell different categories of scatterers apart on the echograms and assign reasonable echo integrator values to them. remains the major source of error with the acoustics as applied. This is especially serious in summer land in the upper layers in March). when the density of plankton and fish is very high and the scattering layers become difficult to differentiate. The exclusion of plankton is highly sUbjective and may bias the contribution of the fish categories (including the Maurolicus euphausids mixture) towards too high values. In addition. the pieture is biased by the inability to deteet fish in the surface layer or fish with low target strength (e.g. mackerei).

Horeover. the deseription is incomplete due to limitations on spatial and temporal eoverage. Most of the coastward slope and some large areas of the Norwegian Deeps proper are inaccessible due to rugged or roeky bottom. Year- to - year differences can hardly be detected with any confidence due to the rather low number of trawl hauls per cruise. There were however no signs of major differences. and the data for all years were pooled. Only very pronounced seasonal changes might be • expected to be detectable.

What remains is at most a reasonably correct description of the fish communities inhabiting the soft-bottom areas. and a rather uncertain picture of the pelagic community. The area is inhabited by two major demersal species assemblages characterstic of the upper slope and bottom of the Norwegian Deeps, respectively.A mixture of the two are caught along the slopes at depths around 200 m. The upper slope' assemblage is the same as found in adjacent shallow areas. i.e. the Northern North Sea and the Skagerrak (Sahrage 1964), but the species composition is somewhat different. The proportion of saithe and norway pout is higher and the haddock. whiting and cod is probably lower. The area represents the major feeding area for saithe. especially for the 3-5 years old juveniles (Fig. 12. Smedstad 1985. Reinsch 1976.1985). while the area is less important or marginal as nursery and feeding area for the other species. Haddock and Norway pout are the only species present in significant numbers as 0- a,Rd 1- group. The winter abundance is the higher for whiting and cod. whieh may refleet a migration towards relatively warm watermasses at this time of the year. The rather minor along-slope differences in species eomposition 9

refleet the differences in distributional patterns. The similarity of the two northern subareas compared with Skagerrak might have been expected, since different stocks (or components of the North Sea stock) inhabit the respective areas.

Earlier aecounts of the lower slope and bottom fishes are based on by-catches on thc Pandalus grounds (Hjort and Ruud 1938, Aker ~ ~. 1966, Thomassen 1974). The results of these and the present study are very similar when only the species assemblage is considered. In general, there is considerable resemblance between the Norwegian Deeps assemblage and the one found along the upper continental slope of the Norwegian Sea (Bakken . et a1.· 1975, Honstad and Johannesen, 1984). Both are composed by boreal species distributed in soft-bottom areas heavily influenced by the Atlantie watermasses. Very similar assemblages are found in the Norwegian fjords' (Skreslet 1978, Hattson 1981, Eliassen 1983). Henee it is reasonable to regard the Norwegian Deeps as a 'vally' just deep enough to permit the slope species to extend their ranges into the North Sea .

Within the Norwegian Deeps there are rather clear differences in species composition between the northernmost areas and the Skagerrak. • The rather high proportion of roundnose grenadier and the virtual absence of northerly species (e.g. rosefish) in Skagerrak is the more pronounced feature. No attempt has been made to explain these differences, but some relation to hydrographical patterns, topography and bottom substrate and associated benthos is likely. The northern areas (1,2,3) are continuously influenced by theoAtlantic inflow and have relatively high bottom temperatures (6-8 Cl. In the Skagerrak the Atlantic inflow is considerably weakened (Furnes et al. 1986), and the bottom temperatures are consistentlY lower (Fig: 13). Host of the 'battom of Norwegian Deeps has a soft mud sediment, and the limited information available point to similar benthic faunas of the northern area and Skagerrak. The deeper parts of Skagerrak have however a some­ w~at different benthic fauna (Kingston and Rachor 1982), probably reflecting species-specific bathymetric distributions.

Some seasonal distributional differences appear rather clearly from the data. The greater argentine shows a pattern of winter concen­ tration and summer dispersion as described from other areas (Johansen og Honstad, 1982, Honstad and Johannesen, 1984). For other species a • similar pattern is indicated (e.g. blue ling, hake). The description of the pelagic fish community resembles earlier accounts (Hamre and Nakken 1970, 1971, Jakupsstovu 1974, Gj0sa!ter 1978). Jakupsstovu (1974) found a relatively low contribution of blue whiting in the commercial trawl catches during the winter months, but no clear seasonal trend from the acoustics, although in two of the three years covered no significant winter concentrations were found. The results so far point to considerable seasonality, but the results 'does not justify firm conclusions. The hypothesis' based on present da ta is that the blue whiting utilizes the entire western and southern slope (including Skagerrak) for feeding in the summer and fall and migrates northwards in late fallto concentrate in the warmer part of the area. A similar pattern is suggested for the 'Haurolicus. The present abundance, nor the significance of mackerel and herring in the Norwegian Deeps cannot be assessed with any certainty from available data. 10·

ACKNOWLEOGEMENTS

The author appreciates the supply of data from the Inititute of Marine Research, Bergen. The project is supported by the Norwegian Council for Fisheries Research.

REFEREIlCES

Aker, E., KÜhlmorgen-Hille, G. and K. Tiews, 1966. Experimental Pandalus Fishing in the Skagerrak and in the North Sea in 1964 and 1965. ICES C.M: 1966/M:2 (mimeo.) . Anon. 1983.1984,1985. International Acoustic survey on Blue Whiting in the Norwegian Sea, August 1983,1984,1985. ICFS C.M.1983/H:5, 1984/H:67. 1985/H:4 (Mimeo.) Bakken. E., Gj0s~ter, J. and J. Lahn-Johannesen, 1975. Demersal fish on the continental slope off Norway. ICES C.M. 1975/F:29 (Mimeo.) Burd, A. C. 1978. Long-term changes in North Sea herring stocks. Rapp. P.-v. Reun. Cons. int. Explor. Mer., 172:137-153 Eliassen, J.-E., 1983. Distribution and abundance of roundnose grenadier (Coryphaenoides rupestris Gunnerus)(Gadiformes, Macrouri-'" dae) in northern and mid-Norway. ICES C.M.1983/G:43 (Mimeo.) Engas, A. and O. R. God0, 1985. The influence of trawl geometry and performance and fish vertical distribution on fish sampling with . bottom trawl. NAFO SCR Doc. 85/102:1-15 Furnes, G. K., Hackett, B. and R. S~tre, 1986. Retroflection of Atlan­ tic water in the Norwegian Trench. Deep-Sea Research, 33(2):247-265 Hamre, J. 1978. The effect of recent changes in the North Sea mackerel fishery on stock and yield. Rapp.· P.-V. Reun. Cons. int. Explor. Mer., 172: 197-210. Hamre, J. and O. Nakken. 1970. Akustiske og biologiske unders0kelser i Nordsj0en og Skagerak i februar-mars 1970. Fiskets Gang, 1970 (26):477-482. (In Norwegian) Hamre. J. and O. Nakken. 1971. Unders0kelser av fiskeforekomster i Nordsj0en og Skagerak i september 1970. Fiskets Gang, 1971(1): 10-14(ln Norwogian) Hjertenes, P. O. 1980. Piggha (Sgualus acanthias L.). Bestandsenhet og vandringsm0nster i Nordsj0en og pa bankene nord av Skottland. Thesis, Univ. of Bergen, Dept. of Fisheries Biology, 61 pp.+app.(ln Norwegian, Abstract in English) (Mimeo.) ~ Hjort, J. and J. T. Ruud. 1938. Deep-sea prawn fisheries and their problems. Hvalradets Skrifter, No. 17, 5-143. Det Norske Videnskapsakademi, Oslo, Norway, 1938. Jakupsstövu, S. H. 1974. Norwegian investigations on Blue Whiting (Hicromesistius poutassou, Risso 1810) in the North Sea 1970-1973. ICES C.M. 1974/H:9 (Mimeo.) Johansen, P.-O. and T. Monstad. 1982. Preliminary results of Norwegian investigations on the greater silver smelt, Argentina silus (Ascanius). ICES C.M. 1982/G: 10 (Mimeo.) Johannesen, A. and T. Monstad. 1984. Bestandsunders0kelser pa vassild. Final report, The Norwegian Council for Fisheries Research, Project No. 1.701.55. Institute of Marine Research, Bergen, Norway, 30 March 1984., 22 pp.+ figs. and tables. (Mimeo.)(ln Norwegian) Kingston, P.F. and E. Rachor. 1982. North Sea level bottom communities. ICES C.M. 1982/L:41 (Mimeo.) lahn-Johannesen, J., Jakupsst6vu, S. H. and T. Thomassen, 1978. Changes in the Norwegian mixed fisheries in the North Sea. Rapp. P.-v. Reun. Cons. int. fxplor. Mer., 172:31-38. Lj0en, R. 1980. Atlas of mean temperature, salinity and density in the summer from the Northern North Sea. Fisken 09 Havet, 1980(2) (Atlas). 37 pp. 11

Hattson. S. 1981. The food of Galeus melastomus, Gadiculus argenteus thori, Trisopterus esmarkii, Rhinonemus cimbrius and Glyptocephalus cynoglossus (Plsces) caught during the day with shrimp trawl in a West-Norwegian "Fjord. Sarsia , 66:109-127. Honstad, T., Dahl, V. and A. Johannesen, 1985. Cruise report, R/V Hichael Sars. 9-28 April 1985.Institute of Harine Research, Bergen, Norway. Hay 1985. (In Norwegian)(Himeo.) Poulsen, E. H. 1968. Norway pout: Stock movements in the Skagerak and the North-eastern North Sea. Rapp. P.-v. Raun. Cons. int. Explor. Her., 158:80-85. Postuma, K.H. 1965. Some remarks on the mackerel migration in the North Sea. ICES C.H./Scombriform Fish Ctte. No. 22 Reinsch, H.-H. 1976. Köhler und steinköhler. A. Ziemsen Verlag, Wittenberg Lutherstadt, DDR, 158 pp. Reinsch. H.-H. 1985. Untersuchungen am Köhler (Pollachius virens) in der Nordsee. Inf. Fischwirtschaft. 32(Heft 4):158-161 Sahrhage, D. Über die Verbreitung der Fischarten in der Nordsee. I. Juni-Juli 1959 und Juli 1960. Ber. Ot. Wiss. Komm. Heeresforsch. 17(3):165-218 . Skreslet, S. 1978. The fish fauna of Skjomen, a fjord of north Norway. Astarte, 11:67-11. • Smedstad, O. H. 1985. Acoustic estimates of saithe in the North Sea in 1984 and 1985. leES C.H. 1985/G:14 (Himeo.) Smedstad, O. H. and S. Tveite, 1985. Shrimp investigations in the Norwegian Oeep 1984-1985. ICES C.H. 1985/K:5. (Himeo.) Thomassen, T. 1976. Variasjoner i mengde og sammensetning av reketralfangster fra et feIt vest av Sotra i arene 1965-1912. Thesis, Univ. of Bergen, Dept. of Fisheries Biology, 82 pp.+app.(In Norwegian) (Himeo.) Thorsen, T. 1979. Populasjonsparametrar hos vassild, Argentina silus (Ascanius). utanfor H0re-Tr0ndelag og i Skagerak. Thesis, Univ. of Bergen, Dept. of Fisheries Biology, 79 pp.+app.(In Norwegian) (Himeo. ) TABLE 1: Cruises on whieh the reported data were eolleeted. TA8lE 2: Charaeteristies of trawls Ind aeeessory eQuipment used on H/S HAkon Hosby and R/V Hiehael Sirs (ref. Table 11.

Vessel Time period No. of trawl stations Bottom trawl Hidw. trawl H/S Hhon Hosby

H/S H.HoSby 84/03/30-84/04/09 29 3 BOTTOH TRAWL Shrimp trawl,8r.dr.Selstad A/S,Hll.y,Norway R/V Bei Oou 84/07/18 and 84/07/26 5 1 Sreatest eireumferenee H/S Eldjarn 84/07/21-84/07/31 6 behind wings (mI 1560 meshes K 80 mm = 125 F/F G.O.Sars 84/07/10-84/07/17 1 1 Gur 18" rubber bobbins H/S H.HoSby 84/08/03-84/08/09 34 3 Heasured vertieal opening (mIt 4.5-5 F/F H.Sars 84/10/05-84/10/19 61 Heasured wingspread (mIt 19-20 H/S H.HoSby B5/03/12-85/03/19 31 Huh size Imml 46 H/S H.Hosby 85/04/09-85/04/13 10 22 Cod end lining,mesh size Imml 2 H/S H.HoSby 85/07/26-85/0B/02 38 Ooors Waeo,5 m ,800 kg F/F H.Sars 85/10/10-85/10/31 70 2 Sweep length (mI 40 H/S Eldjarn 86/03/12-86/04/06 Hydroaeoustie data only H/S H.HoSby 86/03/08-86/03/26 52 2 HIOWATER TRAWL Harstad-trawl,Hod.1662 openinglfathomsl 16 K 16 Greatest eircumference behind wings (mI 1600 meshel K 100 mm K 2 = 320 Cod end mesh size (mml 8 He.sured vertical opening (ml tt 17 Sweep length (mI 100

R/V Hiehael Sars

TABLE 3: Hydroaeoustie equipment and settings. BOTTOH TRAWL Campel 1800 Sreltest circumferenee H/S H.Hosby H/S Eldjarn behind wings Imlttt 1800 meshes K 60 mm 108 Gur 18" rubber bobbins Heasured vertical opening (mItat 3.8-4.2 Eehosounder SIHRAO EK 400 SIHRAO EK 400 Heasured wingspread Iml ta • 17.5-18.5 Frequency (kHz I 38 38 Huh Ihe Imml 40 Transducer (eml 30 K 30 30 K 30 Cod end lining, mesh size (mml 6 2 Transmitter power 1:1 1:1 Ooors Wlco,6 m ,1500 kg Bandwidth IkHzI 3.3 3.3 Sweep length (mI 40 Pulse duration (msl 1.1 1.1 Souree level HIOWATER TRAWL Same al used on H/S Hlkon Hosby. • voltage response 139.5 dB 141.3 dB TVG / Gain 20 19 R - 20 dB 20 19 R - 10 dB Range Iml o - 250;250 ­ o - 250;250 ­ EehO integrator SIHRAO 00 NORD 10 • Own measurements using SCANHAR equipment. No. of ehannels B • 2 bottom eh. 7 • 2 bottom eh. tt Own measurements using SIHRAO Trawl Eye • • tt SCANHAR measurements,(Engls and God.I.1985. ..,

TABLE 4. Species composition in midwater trawl catches from scattering layers of the Norwegian Deeps. 'Upper layer' and 'Iower Iayer' refers to Iayers as shown in Fig.2. Scattering Date Fishing depth Bottoll depth Duration of Catch layer (m) (m) haul(min.)

Upper 04/04/84 80-100 155 15 Müllers pearlside and euphausids (5.5 kg) 1 blue ' whiting, 4 norway pout, 1 lUllp~ucker. Upper 04/07/84 70-185 305 10 Müllers pearlside (4.7 kq), euphausids (2.4 kg). Upper 08/05/85 110-120 305 20 Müllers pearlside (1.0 kg), 2 blue whiting, IUDlp~ucker (5.5 kg, n=3), saithe (9.8 kg, n=B).

Upper 10/19/85 50-100 225 40 Müllers pearlside (3.8 kg, n=2380), euphausids (24.9 kg), blue whiting (1.6 kg, n=B).

Upper 10/27/85 160 185 25 Müllers pearlside (60.0 kg), lumpsucker (17.0 kg, n=7), horse mackerel (2.3 kg n=4), Saithe (1.8 kg, n=2), blue whiting (0.6 kg, n=28), o-group cod (n=l), norway pout (n=4).

Lower 04/07/84 240-260 300 30 Blue whiting (88.5 kg, n=1357), 1 norway pout. Lower 07/26/84 180-250 280 50 Blue whiting (48.0 kg, n=B62), Greater argentine (1.1 kg, n=l1), 13 haddock (o-group), velvet belly (8.5 kg, n=35), müllers peariside (2. kg).

Lower 08/04/84 150-180 260 60 Blue whiting (767,Bkq, n=22oo), Greater argentine (4.5 kq), saithe"(34.1 kq, n=16), velvet beIIy (1. 3 kg).

Lower 07/29/85 200-220 290 15 Blue whiting (8.3 kq, n=103), velvet beIIy (1.3 kg, n=6), lumpsucker (n=l), Müllers pearlside (5.1 kg), euphau~ids (1.3 kg).

Lower 10/17/85 200-220 310 30 Blue whiting (41,9 kg, n=230), saithe (10,1 kg, n=25), greater argentine (0.3 kg, n=3), Müllers pearlside (0.2 kg), euphausids (2,8 kg). Deep- pelagic 03/09/86 315 545 30 Roundnose grenadier (105.4 kg, n=151), greater argentine (1.7 kg, n=3), blue whiting (6.9 kg, n=23), velvet belly (n=l), lumpsucker (n=l). Deep- pelagic 03/12/86 300 450 30 Roundnose grenadier (32.7 kg, n=40) , greater argentine (1.2 kg, n=2), norway pout (n=9), silvery pout (n=l), hake (n=l), müllers pearlside (n=3), euphausids (~2 kg), Pasiphaea sp.. Species name English common name Norwegian common name Spec. code

ScyZiorhinus canicuZa Small-spotted dogfish Smaflekket r~dhai GaZeus meZastomus Black-mouthed dogfish Hägjel SquaZus acanthias Picked dogfish,Spurdog Piggha Sp Etmopterus spinax Velvet belly Svartha Ve Raja radiata Starry ray Kloskate St Raja cZavata Thornback ray Piggskate Th Raja fyZZae Rundskate Rs Raja Lintea Kvitskate Rl Raja oxyrhinchus Long nosed skate Spisskate Ln Dasyatis pastinaca Common stingray Pilskate Chimaera monstrosa Rabbit fish Havmus Rf MauroZicus mueZZeri Mullers pearlside Laksesild CZupea harengus Herring Sild He Sprattus sprattus Sprat Brisling Argentina siZus Greater argentine Vassild Gr Argentina sphyraena Argentine Str~msild NotoscopeZus kroeyeri Stor lysprikkfisk AnguiZZa anguiZZa Europelln eel Al Conger conger Conger. eel Haval BeZone be Zone Garfish Horngjel Coryphaenoides rupestris Roundnose grenadier Skolest Rg MerZuccius merZuccius European hake Lysing Eu • Gadus morhua Cod Torsk Co PoZZachius virens Saithe Sei Sa MeZanogrammus aegZefinus Haddock Hyse Ha MerZangius merZangius Whiting Hvitting Wh PoZZachius poZZachius Pollack Lyr Po Micromesistius poutassou Blue whiting Kolmule BI Trisopterus esmarkii Norway pout 0yepäl No Trisopterus minutus Poor cod Sypike Pe GadicuZus argenteus thori Silvery pout S~lvtorsk Si MoZva moZVa Ling,Common ling Lange Cl MoZva dypterygia Blue ling Blalange Bg Brosme brosme Tusk,Torsk Brosme Tu ?hycis bZennoides Greater fork-beard Skjellbrosme Rhinonemus cimbrius Four-bearded rockling Firetradet tangbrosme Fo Gaidropsarus uuZgari, Three-bearded rockling Tretradet tangbrosme Capros aper Villsvinsfisk Trachurus trachurus Horse mackerel HestemakrE\ll Ho Trachinus draco Greater weever Fjesing Scomber scombrus Mackerel Makrell Ma CaZZionymis Zyra Dragonet Vanlig fl~yfisk Anarhichas Zup~s Zupus Catfish,Atlantic wolffish Grasteinbit Ca Anarhichas minor Spotted wolffish Flekksteinbit SutpigZia gurnardus Grey' gurnard Knurr . Lycodes vah Li i Vahl's eelpout Vanlig älebrosme Va LycencheZys sarsi S~rlig alebrosme Ls Lumpenus Zampraetiformis Langhalet langebarn e Sebastes marinus Redfish,Norway haddock Uer Sebastes uiuiparus Rosefish Lusuer Re Sebastes menteZZa Deepwater rosefish Snabeluer HeZicoZenus dactyZopterus Rockfish BIAkjeft MyoxocephaZus scorpius European sculpin Ulke CottuncuZus microps Polar-sculpin Paddeulke Agonus cataphractus Hook-nose Panserulke CycZopterus Zumpus Lumpsucker Rognkjeks Lu Psetta maxima . Turbot Piggvar Lepidorhombus whiffiagonis Megrim Glassvar' Me ?Zeuronectes pZatessa Plaice R~dspette GZyptocephalus cynogZossus Witch Sm~rflyndre Wi HippogZossus pZatessoides Long rough dab Gapeflyndre Lo HippogZossus hippogZossus Halibut Kveite Hb Limanda Zimanda Dab Sandflyndre Microstomus kitt Lemon sole Lomre SoZea vuZgaris Sole Tunge Lophius piscatorius Angler,Monk Breiflabb Mo

._-----_.__ . -

Table 5. Fish species caught on cruises to the Norwegian Oeeps and adjacent slapes. (Data far cruises and gears are given in Tables 1 and 2.) , 60° ß 60° D ~ 0 2

.- 59° 59°

Figure 1.The Northeastern North Sea and Skagerrak including the Norwegian DeepS (areas deeper than 150-200 m south of approx. 62 N). Sampling effort was concentrated to subareas 1-4. M/S HAKON MOS ~ DEPTH Iml 29 JULY 1985 1 n.m. o I :;;~~;",:,:~:_.. ,c, " ~":~-" >. ;cC'"':iL'S';r:'~~~4S:'~.~~:'c>l'i.';.,~Ji,;!

I --'''• .,.... . ,I ---+I---+----.:-.-_. L +---'-_+-_---+..L-_--.:-+---_---,-+-__---+'..:.-__-+I__-+ ---1__ ._-_._---- -_.._------~------,--- ,i ,::., '1 • i •• ,1 ~.~I'~~'- ~~~~~~~~~~I~~~- ~ , " 100 ,.. __ ._ ...... ,.

200

WESTERN SLOPE

NORWAY COAST ~ ~ NORTH SEA

Figure 2.0aytime echogram from the western slope of the Norwegian Oeeps showing scattering layers of Müllers pearlsides­ euphausids (upper) and juvenile blue w~iting (loWer)d Reco5ding~rom transect running at 300 betwee~ 58 30' and N 58 40'.. • .·M/S HAKON• MOSBY 10 MARCH 1986, 9.00 a.m DEPTH Im) 1-----1 n.m.

200 ._.__..'1.; • .__ ... __ .__ ... ~ -.' ,. ," .... - ..... , ~. -

. -:. - '_4~_~~_ -._._.:._~- ~._ _.~ •• ...... _•__. __. __ ._----- .• __• •••__• . •. 0. •• ."0 ...... '-., 300 .. --/7: ..------.....I '--~ ...__._-~ ::"'7_-_." -.---.- -'.

-.. _--_.. -_._. -" ------...... •-.. -":;--- ,,, .. .----,. --;--_. "....------. . ._- - -;-; - -.------.----..--- _. ------=i=~~~-~~r==~77""' ...... -~~-----+-~ ...... -~...;...~-....--~.....,=__;_~-~~.- ..----..,... 400 iiÄtii_~~ifi~~,::~:, 500

600

Figure 3.Echogram from Skagerak (N 5802~' E 009048') showing concen­ tration of greater argentine and roundnose grenadier. MARCH - APRIL 1985 JULY - AUGUST 1985 MARCH 1986

I 1500

Cl=

1000 '000

000 j 500 500 . R/V Eldjarn I~~,-:- ~

N I 1000 Q) M "... S. 000 l:: ~ R_/_V_E_l=d=ja_r~n.dl.lm . "'1...""",--..Ibrrrrn..-=..Il.J:I...LU:. +J Q) 01 I-l ctl 1500 +J 01 l:: ..-t 1000 +J o Q) :;j I 000 1 _~~ ~ I . SOOl.

N L- -..~_ ~ se S

Others , Pearlside-Euphausids Blue whiting i,Greater argent1ne

..

Figure 4. Inte~ted echo abundance a10ng transe~ crossing the Norw~an Deeps .(see charts below). ~ WINTER SUMMER

COD

so so

25

100 185 2~ .305 -180 -235 -300 DEPT~ INTERVALlml

LONG ROUGH DAS

10

WITCH

10

ROUIllNOSE GRENADIER

200 200

100 100

FOUR-BEARDED ROCKLING

10 10

Figure 5.Hean catch by bottom trawl (Kg.h-1 ) of selected fish species related to depth and subarea (Fig.1). Data from surveys listed in Table 1. Note: Seale on ordinate varies.

... WINTER SUMMER

5TARRV RAV

10 10

.--

SAlTHE

400 400

200 200

NORWAV POUT

100 100

50 50

HAODOCK

50 50 ,',

25 2S #.,,# ..- .'

Figure 5 cont'd. WINTER SUMMER

WHITING

so so

25 25

BLUE WHITING

200

100

RQ5EFI5H

so

25 25

SILVERY PO\JT

10

RABBI! FISH so 50 ~

25 25

Figure 5 cont'd. WINTER SUMMER.

VELVET BELLY

20 20

10 10

GREATER ARGENTINE

200 200

100 100

BLUE L1NG

20 20

10 10

PICKEO OOGFISH

10 10

..-

EUROPEAN HAKE

20 20

10 10

Figure 5 cont'd. I'icked dogUs"h,Spurdog N- 231 20 Argentine

IQ 20 50 ~O 50 60 10 80 90 100

Greater argcntine N- 55H Pollack '0 '0

TOTAL LENGTH (ern) TOTAL LENGTH (ern)

Figure 6.Length frequency di~tributions for some fish species occurring regularly in the Norwegian Deeps; Data from all surveys, depth intervals and subareas were pooled. B1ue wh1ting Na ''''350 Greater fork-beard N.. 53 20 '0

% % 20 Sllvery pout N- 1582 10

10

Mackere1 20

so ..0 50 GO 10 BO 90 400

L1ng,Comrnon 11ng "1= 9CJ '0

10 ~.~ 40 50 ro 10 00 ~ 100 Vahl's ee1pout B1ue 11ng 111

'0

o 10 20 M ....0 50 60 10 BO 90 taO tl0 120 ,:SO TOTAL lENGTH (ern) Tusk,Torsk "I.. t29 10

TOTAL LENGTH (ern)

Figura 6 cont'd, 10 LycencheZys sarst: 1·leqrim N= S4 10 ... ,.

20

'0 20 .0 iO 50 60 10 SO .0 '00

\Htch N- 20'. '0 '0

Figure 6 cont'd. 1984 1985 198El

Winter Summer Winter Summer .v-7inter

N= tlS N= 215 N- 185

20 20 20 20

No survey data

10 '0 10 10

o o 10 20 . 130 iO 50 tO 20 30 "\0 50 o tO 20 3() ~o 50 to 20 50 ~o 50

N= t31 N= • ISi

20 20 20 (Oetober datal n= 2 (Oetober data) No survey data

10 10 10

o+---,---.-lIJ..ll1 ° tO 20 SO-tO 50 o tO 20 50 "'0 SO 10 20 !O "'0 50

TOTAL LENGTH (ern)

Figure 7. Length frequency. distributions for greater argentine (Argentina silus) from the different subareas and seasons. Winter data from subarea 4 (Skagerrak) are either biased (1985) due to the depth distribution of the hauls or lacking (1984).The presence of large fish in Skagerrak is however documented from commercial catch data. •

30 SUBAREA 0/0 1 b 20 Ln' =47 i=1 I 10

10 20 30 40 50 60 70 80 TOTAL LENGTH (ern)

Figure 8.Length frequency histograms for hake (Merluccius merluccius) from different subareas of the Norwegian Deeps. HIS HAkon Hosby. Harch 1986. n.- number of fish in haul i. 1 OEPTH INTERVAL OE PTH 'INTERVAL 100- 180 115-235 2U-300 >305 100-180 185-235 240-300 >305

70 f" 70 n:8 N. No n=8 n=4 n=10 n=8 n=5

N. N. S. II

S. II II O• 1I ·So ••Gr N. Ho H. N~. 1I Gr So H• $1 V. Rf 0 c. . H. Eu I 0 70 ;81 70 ":8 n=3 N. n=9 n=12 n=8 n=22 81 N. N.

N. 6' 1I S.- ® 1I ®

N. CI' H•. CI' S. 1I C C H. N. Gr Z (oWh v. .. Z L. L. ... ~ (i, S. ~ Wh S. 01 Sa ~ 0 S., , ~ 0 0 '"m • ! ! '"m 70 ~ 70 ~ n:11 n=11 N• n:15 n=4 n=22 N. n=15 n=23 n=12

No 11 &I @ N.

N. N.

N. N. N. No @ @ L. •• G· G, WI f. f. G' 1I L. No Wi L. L. 1I •• Wi Wi 61 H. &I H. Va Ho 11 1I f. L. ~ s. N. !\fC.S. C. CoSa$t c~ S. ., 0 , 0 I II ! , , I I I y I II I , I I I I 0 50 0 51 0 50 0 50 0 50 0 50 0 50 0 50 %W %W Fig. 9a WINTER Fig.9a SUMMER,

Fi.gure !t.& and b. Species composition in bottom trawl catche! in teriftS of mean proportion by numbers (tN) and mass (tW) Data from $Urve~isted in Table 1- Specie codes are gheft i ... Table 5. e • • •

DEPTH INTERVAL DEPTH INTERVAL tOO-180 115-235 240-300 >305 tOO-tlO 185-235 240-300 >305

"=8 "=8 "=4 " =to n=8 n=5 5 51 5

SI H.

L. 51 @ SI I. I. @ WI H. V. CI> H. Wh v. L. If C ., CI> Z H. If C Tu Z Re Eu Co ~• ~ 0 TUCI CI H. • 0 ~ 0 Hb Co 1I ~ .. 0 .. ~"' "=tt "= tt n=t5 ~"' "=4 "=22 n=t5 n=23 n=12 5 5 Wi If L. Ro I. (!) If Fe @ L. 50 L. L. V. I. 5' L. 5. , Si Lo. WiSp Va Fo Re L. Eu h R. I. Wi Rg H. ~rEa;p Si v.'::' S. 0 CI F. v:r Eu C. Mo Tu S. C. C. , , , , , 0 5. f'o Eu Tu ~ CI ! M, ·0I "=6 n=5 .n= 4 n=1O n=17 n=9 n=7 n=18 5 5 If v. (4) L. f. f. (4) Wh v. H. Wl If h L. 5. If V. Wi If f. G' Wh F. L. v. v. Rf H. S. H. f. WI W, S. 5' RI ~IStRI Lu R c. 5. C. 0 Hb L. OCI St Sp 0 , , t10C1,lg .,1 Eu Eu c. Th II I , 0 Cl ..RI S. I , 0 ! , I , 5 0 5 0 5 0 5 0 • 5 0 5 0 0 5 %W %W Fig. 9b WINTER Fig. 9b SUMMER a

61

2 0

60 ~

~ 0, ~ 59" •

Figure 10.Catches of I-group mackerel in March 1985. Squares denote bottom trawl stations. Catch in numbers per standard haul is indicated for positive hauls.

900

800

700 "'NTER 700

600 600 SUBAREA , .--,--_._.... 2

a M._.-Q 3 500 ------. 4 r 400 STANDARD ERROR 's,m llkgl 400 STANDARD ERROR Is,ml,lkgl 5 SUBAREA OEPTH INTERVAL SUBARE A DEPTH INTERVAL ~ ~ 300 , 2 3 4 1 2 3 4 g 300 137 97 2'4 57 506 47 117 62 46 38 125 103 200 200 130 84 20 52 94 62 31 29 18 9 32 195 3' 41 4l 70 100 100

'00 200 '00 400 '00 200 '00 400 DEPTH 'm' DEPTH 'm'

1 Figure 11.Total catch (K9.h- ) by bottom trawl in the Norwegian Deeps by season, subarea (Fig.l) and depth interval. Number of hau1s are given for each depth interva1. .). ...

MAR.-APR. 84 AUG 84 MA R,- APR. 85 JUL.-AUG.85 MAR.-APR.86 1'i/h SE ö/h SE n/h SE ii/h SE n/h SE

"'·1.18 " •• IU u •• 114 23 19 418 367 13 ... ; 73 71 288 6 67 472 ' .. % .. SI·· " .. .. j " "j ...... 11 .. "L:L'"1 . 11 11 I • a ••• lf , 11 , 11

" •• 1S1 " •• 12' " •• tU " •• IU 157 139 1312 525 907 98. 54 38 20 .. o .. 486 21 64 54 76 "1' ." 4 2 19 19 .. « .. 4 1 4 UJ a:: % ...... ~ ::::> ::L1L'.. 11 11 11 11 VI " " 11 11 , . " • a 4 •I 11 , " , 11 , 11 , 11 u •• 172 " •• Z87 14 14 792 504 779 623 " •• 111 237 126 " •• zoo 23 6 24 59 26 44 27 51 36 231 108 .."j' ... 1 1 1 1 1 .. 9 3 3 1 .. .. % .. . .. 11 ...... " 11 11

, 11 l.l• a 4 •• lf , " , 11 , 11 " •• az 8 "11 . Z5 1 .. 4 .. ..

"

• II

AGE i:r. s.)

Figure 12.Age frequency distributions and mean catch indices (n/h) of saithe from subareas 1-4. Catch indices are given for three depth intervals; upper figure: < 180 m, midle figure: 185-235 m, lower figure: > 240 m. SE- standard error, s/ln. o _. • . ·•

~ 60· 60·

~ ~

59·

Figure 13.Near-bottom temperature distributions in JUly-August 1985 (upper) and March 1986 (lower).