S E C T IO N 1: General Distribution. R.W. B l a c k e r Fisheries Laboratory, Lowestoft

Transcription

1 P R E F A C E The main task of editing papers from a Symposium is to ensure that they are published as soon as possible after the meeting. However, the conclusions and recommendations of this Symposium highlight the lack of knowledge of some potentially valuable fish. Because of this, im portant data have been added to some papers during editing, and several verbal reports to the meeting have been included in this volume at the request of the Symposium. Thanks to the willing cooperation of the authors the amendments and editing have not unduly delayed its preparation for publication. The terms of reference excluded consideration of the herring, redfish and some other pelagic species which are already exploited wherever they occur. The original title also did not include the words and adjacent seas but as m any of the papers deal with species which do not occur in Arctic waters, the addition of a few words to the title seems more desirable than deletion of a number of papers. For the sake of uniformity, wherever possible the scientific names used are those published in ICES Bulletin Statistique, Vol. 49 for 1964 (Copenhagen 1966). I would like to thank Dr. E.M. P o u l s e n for his help and advice both at the meeting and during the editing of this volume, and Mr. R. J. W o o d and others who have helped in sorting out the discussion notes. Finally, Miss R o se B e d f o r d and her assistants of the Fisheries Laboratory must also be thanked for checking the typescripts and proofs. R. W. Blacker Editor and Rapporteur INTRODUCTION At the Statutory Meeting of the International Council for the Exploration of the Sea in 1963 the Distant Northern Seas Committee and the Gadoid Fish Committee presented to the Council recommendations that a Symposium be organised on the Ecology of Pelagic Fish Species in Arctic W aters. These recommendations were renewed in 1964, and Dr. E r ik M. P o u l s e n was nominated Convenor of the Symposium. A Steering Committee including the Convenor and the Chairmen prepared a programme for the Symposium in which the main lines of the Symposium were designed as follows (a) The significance of the pelagic fish within the food-chains in the Arctic and the role of these species as food for the most im portant commercial fishes, (b) Migration and distribution of the pelagic fish in Arctic waters and their relationship with distribution and movements of the main commercial fishes, (c) The biological basis for fishery of pelagic fish in the Arctic. In the 1965 Statutory Meeting the Distant Northern Seas Committee prepared a Preliminary Programme for the Symposium. The Recommendations on the Symposium were adopted by the Consultative Committee and the Council, and the Symposium was convened on September 30th and October 1st, 1966, at Charlottenlund Castle in connection with the Statutory Meeting of that year. Mr. R. W. B l a c k e r was asked to act as Rapporteur, and he accepted this task. Thirty-eight experts from member countries, from Canada and USA as well as from international organisations connected with fisheries and marine researches participated in the Symposium. Twenty-one papers had been submitted and during the Symposium four additional contributions were given verbatim, these latter are also included in the present publication of the contributions. Furthermore, two synopses, one on Norway pout and the other on poutassou prepared for FAO by Mr. D. F. S. R a it t were submitted to the Symposium for comments. These two synopses were considered and comments on them were given. The Symposium expressed the wish that the preparation of these highly useful synopses be continued by FAO to include also other fish species of commercial interest in the Arctic and in adjacent regions. The scientific papers for the Symposium were considered (reviewed by authors or other experts) in the following order in accordance with the Agenda: 1 - General (occurrence), 2 - Capelin, 3 - greater silver smelt, 4 - smelt, 5 - Norway pout, 6 - Blue whiting, 7 - Polar cod, 8 - Navaga, and 9 - General (food interrelations). After each of these items a consideration and discussion of the pertinent papers took place. Thereafter followed a general discussion of the main subject, as follows : 1. The species as links in food-chains; discussionleader: D. V. R a d a k o v, U S S R.

2 / S E C T IO N 1: General Distribution 1. T H E DISTRIBUTION OF PELAGIC FISH IN RELATION TO HYDROGRAPHIC CONDITIONS IN THE SV A LBA RD AREA By R.W. B l a c k e r Fisheries Laboratory, Lowestoft IN TR O D U C TIO N During the course of English investigations into the biology of the cod in the Svalbard area, the R.V. Ernest H olt was fishing there regularly from 1949 to 1959 with some additional cruises during 1960 to Records of fish other than the commercial species are available from most of these cruises, and a num ber of pelagic or bathypelagic species were recorded. Most of these were caught in the cod-end or in a fine-meshed cod-end cover on a standard Granton bottom trawl, but occasional hauls were also made with pelagic trawls. Some small fish were caught in plankton nets, and the routine examination of the stomach contents of cod gave further information on the occurrence of some species. T H E FISH The following pelagic species were recorded from the area north of 70 N latitude: Mallotus villosus (Müller), Capelin. Argentina silus (Ascanius), Greater Silver Smelt, Argentine. Paralepis rissoi kroyeri Lütken, ( = Notolepis r.k. (Lütken)). Myctophum glaciale (Reinhardt). Notoscopelus elongatus (Costa). Trisopterus esmarkii (Nilsson), Norway pout. Merlangius merlangus (L.), Whiting. Gadiculus argenteus thori, Schmidt. Eleginus navaga (Pallas), Navaga. Boreogadus saida (Lepechin), Polar cod. Micromesistius poutassou (Risso), Poutassou, Blue W hiting. Herring, Saithe and Sebastes spp. were caught frequently but do not come within the scope of this Symposium. The Ernest H olt s records of Argentina silus are included in the paper by R a it t and W o o d (this meeting) and those of Mallotus villosus in a paper by C o r l e t t (this meeting), so no further reference will be made to them. Details of the records of the less common of the other pelagic species are given in Table 1:1. B. saida and M. poutassou were caught on too many occasions for all the data to be tabulated. HYDROGRAPHY The basic current system of the area is well known ( L e e 1952) and need not be shown here. Briefly, the hydrographic system is a balance between the Atlantic influence of the West Spitsbergen and North Cape currents and the Arctic influence of the Bear Island and East Spitsbergen currents. D ISTRIBU TIO N OF TH E FISH The two most common pelagic fish, AI. poutassou and B. saida, both of which have been caught in quantities of up to 38 kg per hour, provide a striking contrast in their distributions: B. saida is an Arctic species and M. poutassou an Atlantic one. All the Ernest H olt records of the two species are plotted in Figure 1:1. The hatching indicates the area of predominating Atlantic influence as shown by the distribution of benthic indicator species (B l a c k e r, 1957 and 1965). The correlation between the distribution of the records of M. poutassou and this Atlantic area is clear. Likewise most of the records of Myctophum glaciale and those of Notoscopelus elongatus, Paralepis, Merlangius and Trisopterus esmarkii are also from this Atlantic area (Figure 1:2), but in contrast there are few records there of B. saida. In fact there are only two from near Bear Island and some from West Spitsbergen, where there may be wide variations in the hydrographic conditions.

3 8 Table 1:1. Occurrences of the rarer pelagic species Cruise and station Date Position Lat. N Long. E O f O / Depth (m) Temperat ure ( C) Surface Bottom Total number caught Remarks 1. Trisopterus esmarkii (Nilsson) 6/ October / April / March s/4 basket l*/s basket included spawning females _ /2 basket Merlangius merlangus (L.) 1956 December ? S. T. Grimsby Town 1/ March Gadiculus argenteus thori Schmidt 1/ March _ to 17-0 cm 4. Eleginus navaga (Pallas) 6/ August , I 25 cm 5. Notoscopelus elongatus (Costa) 2/ March Myctophum glaciale (Reinhardt) 3/1950? March???? 2 in cod stomach 8/ October _ 2/ March m larvae net 4/ June / March in cod stomach 4/ May in plankton net (Sta. W) 6/ August September in plankton net (Sta. W) 7/ October / September in plankton net 1/ January / September in plankton net (Sta. V) 2/ May in fish gut 7. Paralepis rissoi kroyeri Lütken 5/ May / in cod stomach 2/ March _ 2/ /» / May / November / June _ _ 4 6/ October /

4 9 20" 30* a M. poutassou T. esm arkii o B saida navaga Paralepis k ro y e ri r ' C. M yctophum glaciale J N o to sco p e lu s ( elongatus Figure 1:1. Records of pelagic gadoids caught by the R. V. Ernest Holt, Figure 1:2. Records of rare pelagic and bathypelagic fish caught by the R. V. Ernest Holt, Eleginus navaga is the only other Arctic species, but the single record from the Central Bank (75 12'N, 33 35'E) is exceptional in that the normal distribution of E. navaga is in shallow water in the SE Barents Sea, from the coast of east M urm an and the White Sea eastwards to the Gulf of Ob, with occasional specimens as far west as the Kola Inlet (A n d r iy a s h e v 1954). The northernmost and north-easternmost occurrences of the Atlantic species are for the summer and autum n months, when the penetration of surface Atlantic water is at its maximum. Although the catches of the pelagic fish are probably not quantitative, there is some indication that the greatest numbers of such species as Paralepis have occurred in years when there has been a great influx of Atlantic water into European seas ( D ic k s o n, personal communication). The small numbers of myctophids from all sources indicate that they must be much less numerous in the north-east Arctic than they are in Greenland waters, where they constitute an im portant part of the food of cod and other commercial species. r e f e r e n c e s A n d r i y a s h e v, A. P., Fishes of the northern seas of the USSR. Keys to the Fauna of the USSR, No. 53. Academy of Sciences of the USSR. Moscow-Leningrad. (Israel Program for Scientific Translations N 836, Jerusalem, 1964).

5 10 B l a c k e r, R. W., Benthic animals as indicators of hydrographic conditions and climatic change in Svalbard waters. Fishery Invest., Lond., Ser. II, 20: (10), 49 pp. B l a c k e r, R. W., Recent changes in the benthos of the West Spitsbergen fishing grounds. Spec. Publ. int. Commn NW Atlant. Fish., (6) Dartmouth, N.S. Lee, A. J., The influence of hydrography on the Bear Island cod fishery. Rapp. P.v. Réun. Cons. perm. int. Explor. Mer, 131: DISCUSSION The author pointed out that his list omitted some species, notably Ammodytes spp, and Cyclopterus which are pelagic at times. H a n s e n stated that sand eels are im portant off West Greenland from Disko southwards where they often occur in the surface waters and in summer are im portant as food of cod, redfish, halibut and salmon. They also cccur in grab samples taken in the fjords. O n the east and south of the Newfoundland G rand Bank sand eels are also im portant as the food of other species, according to T e m p l e m a n. K r e f f t confirmed that Notoscopelus, Lampanyctus and other myctophids are im portant food species off East Greenland and in the Denmark Strait. Scopelosaurus, Bathylagids, Searsids and other Isospondylous fishes may also be im portant there. Paralepis coregonoides is im portant as food of cod off Labrador. N ik o l s k y said that off the Asian coast, the Pacific cod feeds on myctophids. B l a c k e r mentioned that on several occasions recently Cyclopterus lumpus had been caught in pelagic trawls off West Spitsbergen. H o r s t e d and V il - h j ä l m s s o n agreed that at Greenland and Iceland lumpsuckers were also pelagic for part of the year. N ik o l s k y stressed that future work should include the collection of data on the relative importance of myctophids and other bathypelagic species in the diet of commercial fishes.