This Paper Not to Be Cited Without Prior Reference to the Author

This paper not to be cited without prior reference to the author.

International Council for the C.M. 1983 / G:41 Exploration of the Sea Demersal Fish Commi ttee'

Occurrence, gonad development and age distribution of the roughhead grenadier (Macrourus berglax Lacepede) (Gadiformes, Macrouridae) along the Continental slope of northern Norway •

• by

Jens-Eric Eliassen Institute of Fisheries, University of TromS0 P.O. Box 3083, N-9001 Troms0, Norway

Abstract

Roughhead grenadier (Macrourus berglax) is distributed over wide areas of the Continental slope of northern Norway. In selected areas 9.7 to 73 percent (average 24 percent) of the total catch ~as made up of this species, while Greenland halibut (E~in~ .b~..I..Q..t.b.i.Y'§ .b.iJ2.R.Q.g.l.Q'§'§.Qll~.Q) dom i nated ins0 me area s • In f emal e roughhead grenadier larger than 65 cm total length ovarian growth takes place from May to December, and spawning is suggested to occur in mid-winter. Analysis of gill net catches showed that males were younger and smaller than the females and that the sex ratio was 1 : 2.6 males to females.

1 Legrenadier (M~~~~~~~ ~~El~~) est diss~min~ sur de grandes parties de la pente du soele eontinental du nord de la Norvege. Dans des endroits selectionn~s, sur le total des prises, de 9.7 a 73 % (en moyenne 24 %) etaient de cette esp~ce, alors que fletan noire (~iDDgxg~~§ hiRDQ9~~§~~~) dominait dans quelques regions. Chez la fernelle de M.b.-e~ElllX mesurant plus de 65 cm de longueur totale le developpement des oeufs se d6roule de mai a decembre etla ponte est supposee' avoir lieu' au milieu de l'hiver. Les analyses du contenu des filets montraient que les m~les etaient plus jeunes et plus petits que les femelIes et que le rapport des sexes ~tait de 1 mSle pour 2.~ femelIes•

• 1. INTRODUCTION

Roughhead grenadier (M~~~~~ b.-e~l~~ Lacepede 1801) have li mited commercial importance in some parts of northern Norway and are taken as by-catch in.gill net, longline or trawl fisheries for Greenland halibut ~~hardthius hippoglQssoides). The fishe ry is located along the 'Continental slope at 500 - 900 m depth. until 1980 the roughhead grenadier was usually discarded, but in that year commercial interest increased and catches are now reported in the fisheries statistics•

M;berglax is widely distributed along the Continental slopes of • the Northern Atlantie being found off the coasts of Greenland, Labrador, Newfound~and and Island and on the Island-Faroe ridge (PARSONS, 1976; MAGNUSSON, 1977; 1978; GEISTDOERFER, 1979a; '1979b) •

Informations about M;berglax occuring on the Continental slope of Norway, Bear Island and the Spitzbergen area is given by COLLETT (1904), ANDRIYASHEV (1954), YANULOV (1962), GEISTDOERFER (1979b) and more recently by PECHENIK & TROYANOVSKII (1970), BAKKEN, LAHN-JOHANNESSEN & GJ0SßTER (1975) who have investigated commer cial potensial.

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Catches of roughhead grenadier with trawl, both off Baffin Is land, Labrador, Newfoundland, Island and on the Island-Faroe ridge, are usually too small to be of commercial value (PECHENIK & TROYANOVSKII, 1970; PARSONS, 1976; BRIDGER, 1978). The aims of the present study were to obtain information about the distribu tion, abundance and general biology of roughhead grenadier both from a research and a commercial point of view.

2. MATERIALS MD METHODS

During 1981 and 1982 a large-scale commercial fishery was insti gated with the aim of mapping roughhead grenadier (and Greenland • halibut) distributions along the slope of northern Norway (table 6-1). The commercial vessels were hired by the Regional Fisheries Officers in Troms and Nordland Counties. There were no attempts to standarize the fishing gears used in the different investiga tion areas, and the details of differences in fishing gear type and technical data of the equipment are given in table 6-1.

Areas A, Fand G were studied in June and July, and area H in September 1982. The otheF. areas were investigated in September and October 1981. Average fishing time in the longline fishery (longline at bottom) was 4.5 hours (3 - 6 hours). In addition to the catch-statistics for each boat, fisheries statistics from The • Norwegian Raw Fish Associaton are used.

The research areas for the commercial vessels were located along the slope of northern Norway from 66 0 N ,50 30' E to 71 0 30' N, 17 0 E (figure 6-1). In addi tion random sampIes of about 150 M;berglax were taken from the commercial net-catches in the area B during each month in the period from May to December 1981 and 1982. The material taken from these monthly sampIes was used in the study oE gonad development, age and weight-distribution. Age of M.berglax was estimated by reading sagittal otholiths.

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3. RESULTS

3.1. Distribution and catch composition

During 1981 and 1982 the distribution and abundance of roughhead grenadier were investigated by commercial vessels in 8 different deep-sea areas along the Continental slope of northern Norway (figure 6-1). The results showed that M;b~~~l~~ was present,at all locations from 66 0 to 71 0 30' N. Total fish-length of M.. b~..t:~l..9~ ranged from 34 to 94 cm and size distributions varied wi th fishing gear selection, mesh-size and -type and hook-size • (figure 6-1, table 6-1) • The compositions of the ~ommercial catches in area A- H showed considerable variations with only 9.7 % roughhead grenadier in area A, 55 - 45 % of total catch in areas B, C, D and up to 75 % in area H (figure 6-2). Average catch composition for all areas was 2 4 % M. b..e.r.gllJS , 65 % .R.Lb,.iIH?.Q~ilß"§.Q.i.Q~ß and 11 % !h..b.L..9JHO..e. (figure 6-2). ~..t:.Q"§ID~ were only caught in areas A and H where this species made up about 23 % of total catch. The catch compo sition in the areas investigated is based on fishing at different depths and with different fishing effort (numbers.of nets, hooks and fishing time). Both the relative and the total catches are given in figure 6-2.

Total catch of 1L...b~Ul..9JS was 149 t. in 1980,114 t. in 1981 and 67 t. in 1982 (figure 6-3). The landings of ~~L~l~Ä from the Continental slope show seasonal variations with almost no catches during winter and the main catch during summer and autumn.

The total catches of ~~..t:~l..9Ä in 1981 and 1982 were small (fi gure 6-3) and the three hired commercial vessels landed 8.5 and 13.1 percent of the year's total catch during a three-week period in 1981 and 1982 respectively (table 3-1).

L Tab1e 3-1: Catches of roughhead grenadier (M.berg1ax) by 3 hired commercia1 vesse1s in relation to total catches of M;berg1ax in 1981 and 1982. ======YEAR TOTAL CATCHES FROM No OF FISHING- % OF CATCH COMMERCIAL HIRED TIME PR. TOTAL (kg) HIRED VESSEL VESSELS VESSEL CATCH (kg) (weeks) ======

1981 113.540 9617 3 2.5 8.5 • 1982 67.119 8766 3 3 13.1 ======

3.2. Catch pr unit effort.

The differences in fishing methods employed during the course of the investigation means that it is impossible to make direct comparisons between the amounts of M.berg1ax present in all the 8 • ~reas. However, to compare the catches in the areas A, C and H a measure of catch pr unit effort is used which, for the longline areas, will be estimated as: kg M.b~I9~~~ pr 1000 hooks. The catches pr 1000 hooks show that there are variations both within and between areas (figure 6-4). The two subareas A3 and H2 had ~ignificantly higher concentrations (61.0 kg pr 1000 hooks) of roughhead grenadier than the other subareas (18.0 kg pr 1000 hooks) (P < 0.001) (figure 6-4). The number of hooks used in these two subareas was 21600 and 25750 respectively (figure 6-4).

5 • The average catches pr 1000 hooks for the areas A, C and H were 22.3, 38.1 and 44.5 kg's respectively (figure 6-4), and these average catches could indicate a difference in concentration of M.berglax between the areas. A statistical test (table 6-2) shows that such a difference is not significant for the areas A and C. The total number of hooks used in these areas was 155040 for A, 37800 for C and 38100 for the H-area (figure 6-4). A similar test for differences in catch pr unit effort between the longline areas A/C and H was not carried out because only two trials could be done in area H during three weeks in September 1982 due to bad weather conditions.

3.3. Gonad growth •

• The ovaries of mature roughhead grenadier show a growth in weight during the period May toDecember (figure 6-5). During the early stages in the investigation there was no routine method for age estimation of M.berglax and, therefore, the catches were divided into length-groups for the purpose of analysing ovary-growth (figure 6-5). The results indicate that female ~~~~Z less than 65 cm total fish length sho~ed no increase in ovary weight during the 8 month-period: May - December (figure 6-5). In fishes larger than 65 cm the ovaries grew throughout the autumn. Larger fishes also showed a faster growth of ovaries·and reached a • larger total ovary-weight (figure 6-5) • 3'.4. Age and weight of Miberglax from commercial gi11 net catchest

The age-distributions of male and female roughhead grenadier showed clear differences between the two sexes (figure 6-6). In the material from commercial gill net catches the average age of male M;b~~E~~~ is 3.7 years less than that for the average fe male. The male roughhead grenadier are from 8 to 22 years of age while the ,females are from 12 to 25 (figure 6-6). These high ages made it very difficult to perform the age-determinations. Three independent readings have been performed for each otholith, but

6 nevertheless errors of about 2 - 4 years may have been made (cf. SAVVATIMSKIY, 1971bj SAVVATIMSKIY.P. I. et al, 1977).

The weights of the two sexes differed. Mean weight of males was 1043 9 whereas that of fernales was 2142.5 9 (figure 6-7). No males over 2500 9 were found. Fernales up to 5600 9 were regis tered, although fernales heavier than 4000 9 were rare. The total material from the gill net catches in the period May - December also give a sex (female : male) ratio of 2.6 : 1.

4. DISCUSSION

~ Roughhead grenadier (M~berglax) are common in deep waters along the Continental slope of northern Norway but some specimens are found in the deeper fjords, especially in the county of Finnmark (COLLETT, 1904; HOGNESTAD & VADER, 1979). Although Miberglax are said to be common in those areas, no estimates of abundance have been made.

The results of this work show that M.berglax is distributed along the Continental slope of nor thern Norway (figure' 6-1), and that it may constitute about 24 percent - varying from 9.7 to 73 % of the total catch (figure 6-2). The catches must, however, be evaluated on the basis of the fishing effort and the selectivity of the different gears which have been used in the areas A-H (table 6-l).

The current findings are in agreement with IWAMOTO (1963) who said that Macrourids are often found along the Continental slope and, in many areas, are amongst the most dominant species, both in terms of numbers and biomass. The catches of M.bergla~ in the areas A-H of the current study show that there are fishable quatities of this species to be taken as a by-catch in the fishe ry for Greenland halibut (figure 6-2).

7 In November/December most commercial vessels cease to fish for Greenland halibut and roughhead grenadier, concentrating upon Arcto-Norwegian saithe (~~ll~h~~ ~j~D~) and by the end of December fishing is concentrated on Arcto-Norwegian cod (JJMJJ~ morbua) in shallower waters. Therefore it has not been possible to get any commercial catches in the period from December to May. This seasonal variation in the fishery is also reflected in the total landings of M.berglax during the coarse of tbe year (figure 6-3) •

During tbe years 1981 and 1982 tbree commercial fishing vessels were bired to fish for Greenland halibut and roughhead grenadier. The catches from these vessels amounted,to about 10 percent of the total landings of M.berglax for these two years (table 3-1) • If the three vessels had been fishing for the two species • throughout aperiod of 6 months (May to October)with similar catches (figure 6-2), then the three vessels alone would give a total landing of'1L..Q..e..r..91.a~ equal to the 1981 total catch. In 1980, 1981 and 1982 about 80 - 90 percent of the total catches of ~..eI9l.a~ were fished in the areas B,C,D and E (figure 6-1). Results of the current study indicate that there is a potential for increasing catches of M.berglax both by extending the fishing area and increasing the number of vessels.

In the Newfoundland-Labrador area ~..e..r..9l~ occurs along the Continental slope but there can be large variations in catch pr. unit effort (half hour bottom trawl catches) between different ~ub-areas (PARSONS, 1976). The catches from the slope of northern Norway also showed large variations between subareas (figure 6 4), but, as yet, there is no apparent explanation for this. The most dense concentrations of M.berglax in the Newfoundland area gave catches of 120 - 140 kg pr trawl-hour during the period 1958 - 1973 but usually the catch was less than half of this (PARSONS, 1976) •

In the North-East Atlantic along the Continental slope of the Ba rents Sea north of 71 0 N, trawl by-catches of Macrourids were

8 • from 47 - 87 kg pr. ho~r or up to 10 percent of total catch, the majority of the catch consisting of Greenland halibut (B~iD= . hardtius hippoglossoides) and redfish (Sebastes sp) (PECHENIK & TROYANOVSKII, 1970). In the same area. (area A (figure 6-1) which has its northern limit at 71 0 30' N), the by-catch of lLJ2..eI..91..a.x in the current study was 9.7 percent of total catch in the longline fishery for Rihippoglossoides (figure 6-2). Using bottom trawl, BAKKEN et al, 1975 found a similar percentage of M;berglax in this area, but when using of longlines the catch of M.b..eI..91~~ increased to approximately 27 percent of the total. Thus, the differences in the proportions of Miberglax in the to tal net- and longline catches, both within and between the areas, can, to some extent, be explained by differences in efficiency and selectivity of the fishing gears (BAKKEN et al., 1975) •

• M;berglax caught at 470 to 680 meters depth along the Continen tal slope of northern Norway in January contained ripe eggs (YANULOV, 1962). YANULOV (1962) found two egg-groups with diffe rent diameters (0.5 - 1.10 and 2.3 - 2.75 mm) and suggested that Mib..e..r.g.lax spawned both in winter and spr ing. A winter spawning period is suggested by the results of the current study (figure 6-1) where MiQ..eI..91~~ start to build up their ovaries during summer and autumn (figure 6-5). A spawning time in mid-winter in the North-East Atlantic is different from the results of GEISTDOERFER (1979a) who found that M.berglax spawned at the end of spring and beginning of summer on the I~land-Faroe Ridge and in the North-West Atlantic.

·Many species of Macrourids can reach high ages (SAVVATIMSKIY, 1971a). Roundnose grenadier (Coryphaenoides rupestris) are repor ted to be 40 years old (BRIDGER, 1978) while roughhead grenadier can be more than 30 years (BAKKEN et al., 1975). In this study .the oldest MiQ..eI..91gz found was 25 years, but only a limited number of fish have been investigated (figure 6-6). The differen ces in age and size between the two sexes in the material from the commercial net~catches (figures 6-6 & 6-7) can either reflect an effect of selection or a population structure with smaller and younger males and' in addi tion a sex-ratio wi th few males in relation to the females.

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From figure 6-7 it can be seen that the nets caught the smaller males but not the smaller females and this leads to two possible explanations for the absence of the smaller females: either the younger females are not present at this area and depth (average 600 - 650 meters) or males may change sex as they grow larger. Hitherto, the examination of the gonads has given no indica tions for such a sex-change (EL lASSEN & FALK-PETERSEN, in prep.). STEIN & PEARCY (1982) suggested that sex-ratios different from 1 : 1 may be related to distribution differences, age, rates of mortality and spawning habits.

It is often found in fishes that the males spawn at an earlier age and that males are smaller than females, and this has been • explained by the spawning stress and a resulting higher mortality-rate for the earlier maturing males (BAGENAL, 1957; GIESEL, 1972; MacKINNON, 1972). It is also suggested by CLARKE (1983) that the adaptive value of such differences may be to maximize egg-producing biomass and minimize intraspecific compe tition in a situation where the food resources are low.

ACKNOt"lL EDG EMENT

.1 am grateful to the crews of the commercial fishing vessels: "Hege-Anita", "Benum-Senior", "Wal ker", "Tramhavet", "Jan-Yngve" and "Knut-Aleks" for hospitality and help onboard. Thanks to the Regional Fisheries Officers in Troms and Nordland Counties, and the consultants Finn Nilsen, Jan Hansen and Svein Baadst0 for organization and hiring of the fishing vessels.

Thanks to Dr Malcolm Jobling for reading the manuscript. Thanks to student Elling Lorentsen for help with sampling and analysing of the data. Hillka Falkseth and Gunvor Granas prepared the figures. This work was in part supported by the Norwegian Fishe ries Research Council (NFFR).

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;

5. REFERENCES

ANDRIASHEV,A.P. 1954. Fishes of the northern seas of"the U.S.S.R. -Acad.Sci. U.S.S.R. Israel program for Scien tific Translations, Jerusalem 1964. 617 pp.

BAGENAL,T.B. 1957. The breeding and fecundity of the Long Rough Dab (Hippoglossoides platessoides Fabr.) and assosiated cycle in condition. J. Fish. Res. Bd. Can. 36: 339 - 375.

BAKKEN,E.i LAHN-JOHANNESSEN,J. & J. GJ0SETER. 1975. Demersal fis hes on the Continental slope of Norway. Fiskets Gang. • 34: 557 - 565

BRIDGER,J.P. 1978. New deep-water trawling grounds to the west of Britain. -Laboratory Leaflets, MAFF Directorate of Fis heries Research, Lowestoft. 41: 40 pp.

COLLETT,R.1904. Meddelser om Norges fiske:Aarene 1884 - 1901. Forh. Vidensk. Selsk. Krist. 1903(1904) 9:1 - 175.

CLARKE,T.A. 1983. Sex ratios and sexual differences in size among Mesopelagic fishes from the Central Pacific Ocean. • Marine Biology. 73: 203 - 209 • ELIASSEN,J.-E. & I.-B.FALK-PETERSEN. (in prep). Reproduction of roughhead grenadier (Macrourus berglax) at the Continental slope of northern Norway (in prep.)

GEISTDOERFER,P. 1979a. New data on the reproduction of Mac rourids (Teleostei, Gadiformes). -Sarsia. 64(1-2): 109 - 112.

GEISTDOERFER,P. 1979b. Recherches sur l'alimentation de Macrourus berglax Lacepede 1801 (Macrouridae, Gadiformes). Ann. Inst. Oceanogr. 55(2): 135 - 144.

11 •

GIESEL,J.T. 1972. Sex ratio, rate of evolution, and environrnen tal heterogenity. Am. Na t. 106 (949): 380 - 387.

HOGNESTAD,P.T. & V.VADER. 1979. Saltvannsfiskene i Nord-Norge. University of TromS0. Tromura. 6: 74 pp.

IWAMOTO,T. 1963.Macrourid fishes of the gulf of Guinea. Stud. trop. Oceanogr. Miami. 1: 316 - 432.

MacKINNON,J.C. 1972. Summer/storage of energy and its use for winter metabolism and gonad rn~turation in American Plaice (Hippoglossoides platessQides). J. Fish. Res. Bd. Can. 29(12): 1749 - 1759.

MAGNUSSON,J. V. 1977. Some notes on the spawning habi ts of Macrouridae at Ieeland. -Internat. Council. Explor. • Sea. C.M. 1977/F:49. Demersal Fish Comrnittee. 9 pp.

nAGNUSSON,J.V. 1978. On the distribution and spawning grounds of the roughhead grenadier (Macrourus berglax Lacepede) west of Iceland. -Internat. Council. Explor. Sea. C.M. 1978/G:36. Dernersal Fish Comrnittee. 10 pp.

PARSONS,L.S. 1976. Distribution and relative abundance of roundnose, roughhead and common grenadiers in the northwest Atlantic. Internat. Comm. for the • Northwest. Atl. Fish., SeI. Papa 1: 78 - 88 • PECHENIK,L.N. & F.H.TROYANOVSKII. 1970. Trawling resources on the. north Atlantic Continental slope. -Israel program for scientific Translations, Jerusalem. 1971. 66 pp.

SAVVATIHSKIY,P.I. 1971a. Determination of the age of Grenadier (Order Macrouriforrnes). J. Ichthyol. 11: 397 -403.

SAVVATH1SKIY, P. 1. 1971b. Studies of the age and growth of round nose grenadier (Macrourus rupestris Gunn.) in the North Atlantic, 1967 - 1970. ICNAF Res. Doc. 71/93: 125 - 138.

12 SAVVATIMSKIY,P.I.; KOKB,K. & P.YERNST. 1977. Comparison of methods for determining the age of grenadiers (Macrui formes, Pisces) from the northern Atlantic. J.Ichthyol. 17: 324 - 326.

STEIN,D.L. & W.G.PEARCY.1982. Aspects of reproduction, early life history, and biology of Macrourid fishes off Oregon, U.S.A. Deep. Sea. Biol. 29(11A): 1313 -

1329. "\

YANULOV,K.P. 1962. On the fecundity of roughhed grenadier (Macrourus berglax Lacepede). Zool. Zh. 8: 41 - 84 •

• 6. FIGURES ABD TABLES

7 figures and 2 tables are given.

13 jl

\ 70° .;

10 69° j • o , ja \

20 ~10 \ 0', \a

... )~ ". ... 10 \ \ 0 " ,a \ 30 100 \ \ \ \ 67°

Fig. 6-1: Locations ,of areas (A - H) and subareas (Al, A2, ••• ) for commercial fishery for roughhead grenadier (M;berglax) along the Continental slope of Norway in 1981 and 1982. Size distribution of the grenadier by area and gear are shown.

14 f,7;1 Macrourus berglax ~ Reinhardlhius hippoglossoides R Brosme brosme 6978 5100

..-- ~ ..-- .---- Reference 10 figure 1: A B ~ E F G H ro ...... 2"O~'" ~ Cl Ol >. Cl '"Cl '"Cl QlC: Cl c: Cl Ql Ql '" Ql Ql Cl'" Area .. Ql '" Cl ",,,,Cl -'" c: Ql c: c: c: Q) ca.~ E"'-Ql' -'" Cl'" c: '" '" '" 0-'" c: Cl c: !lJ !lJ !lJ >~~ Ql «('iS:;= 1-:;::.... '" :;;;:'" ...JQl'" Cl -, .= .= .= • Fig. 6-2: Composition of commercial catches (in kg and percent) at different areas along the Continental slope of northern Norway.

n 1980 Total eateh. br. 1980: 149 tons m1981 --- 1981: 114 " li 1982 .--- 1982: 67 " ..--

~ ~ " r.:: \' "~: :\' ~ ~: ~: ~ {: ..- '_J, \' :( ~ X s ~~ ~ ... X r: t. \' ~ X ~, ,{: ~ $ \' \' .~ ,~~ '{ X S X f:\. '? . * s v ~: ..- ~: ... f~ v *;<.X· ?x :,. ,. S;. ~ .<: ~ s ~: "~ ->: \' :<: J .... , '/') ~ , \' .... * ~ ,. 'I: <: :{: ~ 'i v f~ \' ~." mIIIIIlI :Y ~>:"1 <. ['i: fx \' rX, r fm.. """""'" rl * . Jan Feb Mar Apr May Jun Jul Aug Sep Oet Nov Dee

Fig. 6-3: Total catch of roughhead grenadier (M;berglax) in Norway in 1980, 1981 and 1982.

15 ...0. 100 Ql I- "0 Catches from subareas Cll n c Ql 8 01- C, Average catches from main areas, I- ~ 95% confindence limits shown "0 Cll Ql ~ .c 60 .c 0. Cl I- ::> ~"'" 0 t/) CI: 40I- 0 Ö "'"0 .c .c u 0 Cll 0 20 u -0 0 ·n n nnn Area: Reference Al A2 A3 A4 A5 A6 A7 A8 A to figure '-1 C Gl G2 G 0 0 0 0 0 0 0 0 0 0 0 0 0 Number of hooks 0 0 0 0 C\I 0 C\I 0 '

600,------., .-. length-group: 40-59.9 cm 0---0 60-64.9 cm 500

~ .-. 65-69.9 cm E Cll 0---0 70-74.9 cm C, 400 ~ ""-"" 75-79.9 cm I fr---i:::,. 80- 100 c m :r ~ w 300 3: I > CI: 200 < >o 100

o~===r===r=-=:r===r=-=----,.:===:;===~-_I o

Fig. 6-5: Change in ovary weight with time for various size groups of roughhead grenadier (M;berglax). Values used in plotting this figure are mean ovary weights. Data from 1981 and 1982.

L 28 I- ~ maLes N=62 x=14.4 age 26 I- st.dev.=2.44 c... 24 I- ::J I- femaLes N=162 x=18.1 age ~ 22 n l!l st.dev. = 2.49 w 20 ~ l!l « 18 I- :r: ~ 16 f.- w z 14 I- H :r: 12 - I ~'" 10 I- ~ 8 I- co 5 6 f.- z 4 f.- 2 l- ~ ~ ~ o nn I~ I~ I~ n n n 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 2223 24 25 AGE (years)

Fig. 6-6: Age-distribution of male and female rough head grenadier (M;berg1ax) from a commercial gi11 net catch (220 mm mesh-opening) in June 1981.

~ males N= 419 x=1043.0g St.dev.=353.14 ll. 80 ::> o nfemales N=1083 ;<=2142.5 g St.dev.=663.38 '" 70 ..:E: :3 60 o o 5 50 w.. • :s 40 :t: ~ 30 ~

~ 20 w '"(D ~ 10 z n ~ ~ ~~~nn~nnn nn ~ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 N ..,. ..,. 0 N 0 0 0 0 0 0 0 0 0 0 co ~ ..,. co 0 N ..,. co 0 N ..,. N ..,. ~ ~ ';? ~ co 0 '" N N N N'" N '" ..,. ..,. ..,. ..,.'" ..,. WEIGHT (gram)'" '" '" '" '" '" '" '" '"

Fig. 6-7: Total weight of male and fema1e roughhead grenadier (M;berg1ax) from commercia1 gi11 net catches (220 mm mesh-opening).

17 • Tab1e 6-1:Materia1s and methods used in a com. fishery for M.berg1ax a10ng the Continerita1 slope of northern Norway. Letters A-H refers to figure 6-1. Dates of investigation (DOI) are given. ======AREA NAME AND FISHING TECHNICAL DATA OF GEAR LENGTH (IN GEAR DOI FEET) OF SHIP ======A "Jan-Yngve" longline ,Type: North-Sea longline 1 (75 ) Hook: Mustad-Harwich no. 7 JUN82 Bait: Mackerel (Scomber scombrus) B "Walker" gill net Type-l net: Monotwine of filament 1 (65 ) no 5*3 Mesh-size: 186 mm Length: 27.5 m Depth: 5.5 m Type-2 net: Multifilament(nylon) of filament no. 5 Mesh-size: 220 mm SEP/OCT81 Length: 26 m Depth: 5~5 m C "Hege-Anita" longline Type: North-cape longline (501) Hook: Mustad-Harwich no. 6 SEP/OCT81 Bait: Mackerel(Scomber scombrus) D "Walker" gill net Same as area B 1 SEP/OCT81 (65 ) E "Benum-Senior" gill net Same as area F 1 SEP/OCT81 (70 ) F "Walker" gill net Type-l net: Monotwine of filament 1 (65 ) no. 5*3 Mesh-size: 220 mm Length: 26 m and Depth: 5.5 m for both type 1 & 2 Type-2 net: Multifilament(nylon) of filament no. 5. JUN/JUL82 mesh-size: 220 mm

G" "Tr~nhavet" gill net Type-l net: Monofilament of 1 (58 ) filament no. 0.65 Mesh-size: 152 mm Length:27.5 m Depth:6.1 m Type-2 net: Multifilament(nylon) of filament no. 4. Mesh-size: 186 mm JUN/JUL82 Length:27.5 m Depth:6.1 m H "Knut-Aleks" longline Type: North-Sea longline. (75' ) Hook: Mustad-Harwich no 6. SEP82 Bait: Mackerel (Scomber scombrus) ======

l Tab1e 6-2: Catch of M.berg1ax pr 1000 hooks. Comparison of means. (t-test with Besse1s correction, MORONEY (1951». ======Area A Area C ======~======NI = 8 N2 = 9 Kg1 = 22.3 Kg2 = 38.1 varl= 24.54 var2= 25.92 N = number of trials in the area Kg = average catch in kg M;berglax pr 1000 hooks var = variance in the data t = -1.922 df = 16 Conclusion: significance of difference is not established (0.10 > P > 0.05). ------