238
CHAPTER 9 OBSERVATIONS ON THE DISTRIBUTION OF DEMERSAL FISH ON THE I CELAND-FAROE RIDGE IN RELATION TO BOTTOM TEMPERATURES AND DEPTHS
By
A. K o t t h a u s , Biologische Anstalt Helgoland, Zentrale, Hamburg and
G. K r e f f t , Institut für Seefischerei der Bundesforschungsanstalt für Fischerei, Hamburg
INTRODUCTION of ichthyofauna. The patterns of distribution of At Since the days of Sir J o h n M u r r a y , scientists have lantic and Arctic forms were often rather irregular but, well understood how significant is the chain of sub on the whole, followed more or less distinctly a marine ridges — part of which is formed by the Iceland- dividing line along the top of the Ridge. Both hydro- Faroe Ridge —as a barrier between the bottom fauna graphical and topographical factors may be involved of the Atlantic and that of the Arctic. The sharp in the formation of this peculiar pattern. differences in temperature on either side of the Ridge The “ICES-Overflow-Programme” offered a wel are reflected by equally sharp differences in their come chance to learn something more about the fauna, that of the Norwegian Sea being a very peculiar factors governing the distribution of fish living at or one. O f the 433 species of animals listed by M u r r a y close to the bottom of the area. Therefore, immediately {vide N. B. M a r s h a l l : Aspects of Deep Sea Biology: after completing the third hydrographical survey in 357, 1954) on one or other side of the Ridge, only 48 the same area (19.-22. June, 1960), it was decided to have been found on both sides. The fauna of the Ridge spend a few more days with R. V. “Anton Dohrn” in itself, on the contrary, might consist of a mixture of getting some information concerning the relationship both Atlantic and Arctic elements, with a marked between fish distribution, water temperature, and predominance of eurythermie forms. This should be depth. It was assumed that bottom temperatures would especially true for sedentary and slow-moving animals. not have changed significantly within the few days If we assume that the phenomenon of the overflow of and so further observations were made only at one cold Arctic water across the Ridge is confined to some station (AD 759/1960). Here, according to the chart special passages determined perhaps by the topography prepared by Dr. T a it for the third survey, the of the Ridge, then this phenomenon might cause a temperature ought to have been between 0° and 1°C. much more differentiated pattern of distribution of However, the actual bottom temperature when fishing the invertebrate bottom fauna. Unfortunately, a was started at this station was found to be — 0’02°C. detailed survey relevant to this question has not yet Thus the bottom temperatures seem to change more been undertaken. rapidly than was expected. With this information in A pulsating overflow with rapid temperature changes mind, one cannot be sure of the degree to which the near the bottom on one side of the Ridge ought to be temperatures used from Dr. T a i t ’s chart for the paralleled by similar changes in the distribution of the preparation of our distributional charts are reliable. more active, faster-moving animals. In the commercial For that reason, and since only 18 hauls could be fisheries on the northern side of the Ridge, such made in the time available, there is included in this phenomena have sometimes been observed by our report the larger and more detailed information ob trawlermen; rapid changes in the availability of red- tained in a cruise the year before (28. April-6. May, fish have occurred at the same location within a few 1959), which covered nearly the same area and in hours. Long-term variations have also been observed. some cases even the same stations. During this cruise Earlier research vessel cruises to the “ Rosengarten” bottom temperatures were measured immediately be have also shown a rather complex distribution pattern fore fishing commenced at each station. However, due 239
Table 9:1 List of trawl stations. “Anton Dohrn” cruises April/May 1959 and May/June 1960
Station Position Data Depth Bottom Fishing No. N. lat. W. long. m. temp. °Cj1 time Remarks
A. 1959 Cruise. 3 2 1 8 ...... 28. April 64°20' 12°25' 450-460 2-8 19-20—19-50 3223 ...... 29. „ 63°40' 12°30' 450 5-1 06-45-07-15 3224 ...... 29. „ 63°35' 12°29' 440-460 5-1 08-30-10-30 Commercial fishery 3225 ...... 29. 99 63°37' 11°39' 350 5-4 14-10-14-40 3226 ...... 29. „ 63°40' 10°45' 430^50 2-7 17-55-18-25 3229 ...... 30. 99 63° 19' 09°37' 450 1-1 06-45-07-15 3230 ...... 30. „ 63°30' 11°10' 310 5-6 12-45-13-15 3231 ...... 30. 99 63° 12' 11°40' 400 4-1 15-50-16-20 3232 ...... 30. „ 63°24' 12°38' 500-510 3-8 21-00-21-30 3236 ...... 1 . May 63°35' 12°30' 450 _ 06-30-08-30 Commercial fishery 3237 ...... 1 . ,, 63°46' 12°25' 430 _ 10-00-11-40 Commercial fishery 3238 ...... 1 . „ 63°43' 13°00' 650 3-6 14-30-15-00 3252 ...... 2. ,, 63°00' 08°36' 440 _ 23-50-00-20 3253 ...... 3. >» 63°02' 10°35' 450 1-9 06-50-07-20 3254 ...... 3. „ 63°00' 12° 17' 470-480 4-7 17-10-17-40 3255 ...... 3. „ 63°09' 13°18' 735-760 4-2 22-40-23-40 Trawl heavily damaged 3267 ...... 6. >> 61°15' 08°05' 750-805 -0-2 13-40-14-30 Came fast; net damaged
B. I960 Cruise. 751/60...... 19. June 64°11' 12°13' 445 6 10-50-11-20 752/60...... 19. >> 64°20' 12°23' 450 1-2 13-25-13-55 Came fast; net lost 754/60...... 19. 99 63°53' 12°27' 466 6 18-55-19-05 Came fast; net undamaged 755/60 ...... 19. >> 63°53' 11°50' 370 2-3 20-55-21-25 Came fast; net damaged 756/60...... 20. 99 63°36' 12°30' 450 6 07-20-07-50 757/60 ...... 20. 99 63°37' 12°15' 400 ■111] 6 08-50-09-20 758/60 ...... 20. 99 63°36' 11°27' 320-330 3-4 11-45-12-15 759/70...... 20. 99 63°37' 10° 46' 480 0-12 14-40-15-10 761/60 ...... 20. 99 63°23' 10°40' 410 1-2 19-50-20-20 762/60 ...... 20. 63°20' 10°40' 320 1-2 21-20-21-50 763/60 ...... 21. 99 63°23' 11°37' 400 3 06-50-07-20 764/60...... 21. 99 63°22' 12°33' 500 5 11-50-12-05 Came fast; net damaged 765/60...... 21. 99 63°10' 12°43' 500 5-6 13-50-14-20 766/60...... 21. 99 62°58' 12°22' 490-500 4-5 18-20-18-50 767/60...... 21. 99 63°00' 11°45' 480 4 20-45-21-15 768/60...... 22. 99 63°or 10°47' 450 3-4 06-45-07-15 769/60 ...... 22. 63°00' 09°50' 480-500 2 09-40-10-10 771/60...... 22. 62°46' 09°09' 470 4-5 14-50.15-05 Came fast; net undamaged
1 The bottom temperatures for the 1960 cruise were abstracted from a chart of the third survey prepared by Dr. T ait. 2 The actual bottom temperature was stated to be — 0-02° C. to time-consuming racial investigations on redfish, it “demersal fish” as applied in this report. In addition was not always possible to work up the catches in detail, to the “ true” bottom fish, a few other species are i.e. the precise numbers of specimens of the different included which may spend their lives partially in mid species are not always available. In such instances the water rather than at the sea-bed. Such species are e.g. numbers of individuals to each “Korb” (basket) were the greater silver smelt, Argentina silus (Ascanius) and estimated ; reliable factors for such a computation were the blue whiting, Micromesistius poutassou (Risso). Both available. The number of trawl stations on the 1959 of these species may occasionally be taken by hook cruise was 17. and line even close to the surface; however, the main Generally, standard hauls of 30 minutes duration habitat at least of Argentina is on or close to the bottom, were made in both years. In some cases, such as when where according to C o h e n (1958), it seems to prefer the net came fast, the fishing time was shorter, and in the edge of the Continental Shelf, thus often sharing others, when fishing for commercial purposes during the grounds with the redfish, which is, likewise, not a the 1959 cruise for instance, it was extended up to two true bottom-dweller. Most likely the blue whiting is in hours. its habit much more a midwater fish than Argentina. It Some comments may be made concerning the term is, however, very commonly encountered in catches of 240
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" S G S S JQ D S £ §1= S ci S ^ — -» CQ ,'O 3:2 «LU B ü ! § ? ! « ) , -a v Ë S &j &9 &3 Faunal5 types: b The 6 = actual boreal, ba bottom = temperature boreo-Arctic, a was = stated Arctic. to be -0'02°C. cô ci a ^ S a ci as ra as c« ;îcj ds a Ses 1-3 2:d b Q fa fa fa fa fa fa fa fa fa . fa fa fa 16 242 Table 9:3 Ranges and weighted mean values of depths and bottom temperatures for demersal fish species (Numbers of specimens converted from table 9:2 A and 9:2 B according to “standard hauls”; 1959 and 1960 cruises com bined) Number Depth (m) Bottom temperature °C Species of specimens Range Mean Range Mean 662 2-8-S-5 3-9 Centroscyllium fa b r ic ii...... 23 450-760 - 4-2 - Centroscymnus coelolepis...... 1 735-760 400-500 452 -0-02-6-0 2-5 Raja radiala...... 78 310-760 465 1-5-5-6 3-9 Raja fy lla e ...... 26 430-805 586 -0-2-4-2 2-1 Raja spinicauda...... 6 750-805 - -0-2 - Raja hyperborea...... i 310-510 454 1-5-6-0 4-9 Argentina situ s...... 938 450-760 617 2-8-4-2 3-5 Notacanthus phasganorus...... 3 640 1-1-4-2 3-5 Coryphasnoides rupestris...... 533 400-760 450-760 513 2-8-4-2 3-1 Macrourus berglax...... 5 48 310-445 331 1 -5-6-0 3-0 Gadus morhua ...... - 5-6 - Melanogrammus aeglefinus...... 1 310 310-500 385 1-5-6-0 5-3 Pollachius virens...... 27 310-760 431 -0-02-6-0 3-7 Micromesistius poulassou ...... 2628 320-805 439 -0-2-6-0 3-5 Molna dypterygia...... 42 310-500 407 1 -9-6-0 4-6 Brosme brosme...... 40 750-805 - -0-2 - Gaidropsarus argentatus...... 5 500-760 625 3-6-5-0 4-0 Lepidion eques...... 8 - 4-5 - Ammodytes lancea marinus...... 6 470 735-760 - 4-2 - Aphanopus carbo...... 1 320-460 412 1-5-6-0 3-9 Anarhichas minor...... 21 445 1-1-2-7 2-2 Anarhichas denticulatus...... 6 430-450 400-760 496 -0-02-5-5 2-6 Lycodes esmarkii...... 26 400-805 492 -0-2-4-1 0-6 Lycodes eudipleurostictus...... 12 735-805 773 -0-2-4-2 0-3 Lycodes pallidus p a llid u s...... 9 320-760 545 3-5-5-1 4-2 Sebastes viviparus...... 5 378 1-5-6-0 3-4 Sebastes marinus, type marinus...... 272 320-650 320-760 449 1-5-6-0 4-6 Sebastes marinus, type mentella...... 2978 363 -0-02-6-0 2-7 Sebastes marinus, type intermediate 479 320-650 320-470 423 3-5-6-0 4-4 Sebastes marinus, type giants...... 16 450-480 463 -0-02-3-5 0-9 Artediellus atlanticus ...... 16 320-805 481 -0-2-6-0 2-1 Cotlunculus microps ...... 28 735-760 - 4-2 - Cottunculus thomsonii...... 1 450-805 571 -0-2-4-0 2-2 Careproctus reinhardtii...... 3 1 750-805 - -0-2 - Paraliparis bathybii...... - 1-2 - Hippoglossus hippoglossus...... 2 320 400-805 449 -0-2-4-5 1-6 Reinhardtius hippoglossoides...... 180 417 1 -5-6-0 4-1 Hippoglossoides platessoides...... 72 310-500 - 5-0 - Lophius piscatorius...... 2 500 the otter-trawl, and it is obviously very rarely caught perhaps by factors such as pressures, may possibly in situations where the bottom temperature is lower “strand” at the edges of the Ridge and then are eaten than 2-5° C, even if the midwater layers may show by the bottom fish. These midwater fish are not in temperatures suitable for its occurrence. Therefore, it cluded in our report. seems to be justified to conclude that the bulk of the trawl-caught specimens has been taken close to the bottom. MATERIAL AND METHODS During both cruises many examples of true ba- thypelagic and even pelagic fishes were found in the The stations worked during the two cruises are listed stomachs of various species of “bottom fish”, a in Table 9:1. Tables 9 :2 A and 9 :2 B show the numbers situation which suggests that the bottom fish may of demersal fish caught at the different stations of the either temporarily feed off the bottom, or that the respective cruises according to their families, and give midwater fish, limited to a certain minimum depth their size range and their mean lengths. Furthermore, 243 Table 9:4 Cottunculus Reinh.ard.lius Bt.°C No. of specimens (No. of hauls) No. of specimens (No. of hauls) < 0 ...... 7 (2) 19 (2) 0-1 ...... 5 (1) 11 (2) 1-2 ...... 7 (3) 105 (3) 2 - 3 ...... 4 (1) 31 (3) 3 - 4 ...... (-) 5 (1) 4 - 5 ...... 2 (2) 7 (3) the letters “b” (= boreal), “ba” (= boreo-Arctic), and THE ICHTHYOFAUNA OF THE ICELAND-FAROE RIDGE “a” (= Arctic), following the scientific name of each AND ITS DISTRIBUTION species, give a hint as to the ichthyogeographic The demersal fish community of the Iceland-Faroe components to which the species are referred. In the Ridge comprises at least three major faunal elements, headlines of these tables the serial number of each viz. a boreal, a boreo-Arctic, and an Arctic component. station, the depth, the bottom temperature, and the The first component may be further subdivided into duration of the haul (trawl at the bottom) are given. a species group typically inhabiting the deeper parts The number of species was 34, in 1959 and 23 in of the Continental Shelf and the offshore banks and 1960; altogether 36 species were caught. Immediately into another group whose species characteristically after capture, the fish were identified (the non inhabit the Atlantic slopes, where they occupy a much commercial species by the junior author) and measured wider geographical range than do the bankfish. to the cm below. Examples of most of the species The group of boreal bankfish represented in our were preserved and are stored in the collections of the catches is made up of the following seven species : the “Institut für Seefischerei”, Hamburg. gadoid fishes Gadus morhua Linnaeus, Melanogrammus The vertical distribution of the species and their aeglefinus (Linnaeus), Pollachius virens (Linnaeus), the relation to the bottom temperatures are listed in sandeel Ammodytes lancea marinus Raitt, the lesser red Tables 9:3 and 9:5. The geographic distribution is fish Sebastes viviparus Krøyer, the long rough dab mapped on Figures 9:1 to 9 :8, those of the 1960 cruise Hippoglossoides platessoides (Walbaum), and the monk (signed with “B”) showing also the thermic situation fish Lophius piscatorius Linnaeus. at the bottom according to the third hydrographic Atlantic deep-water species are : the dogfishes survey of the “Overflow-Programme”. For the 1959 Centroscymnus coelolepis Bocage & Capello and Centro- cruise (signed with “A”), a cover page7 gives the scyllium fabricii (Reinhardt), the spiny eel Notacanthus bottom temperatures so far actually measured. A phasganorus Goode, the grenadierfish Coryphaenoides second cover page for all the maps shows the topo rupestris Gunnerus, the morid fish Lepidion eques Gün graphy of the Iceland-Faroe Ridge. ther, the black scabbardfish Aphanopus carbo Lowe and The symbols for the individual species are of different the cottunculid Cottunculus thomsonii (Günther), i.e. sizes according to the number of specimens caught. equally 7 species. Four other boreal species link the When the duration of a haul exceeded the usual 30 two sub-groups together to some degree; these are minutes, the numbers of fish actually caught have Argentina silus (Ascanius), the blue whiting Micromesistius been converted to the standard haul in order to make poutassou (Risso), the blue ling Molva dypterygia (Pen the figures on the maps comparable. Some exceptions, nant), and the torsk Brosme brosme (Ascanius), the first however, were made for some rare species. In Figure two of which are indeed semi-pelagic and therefore 9:6 the composition of the redfish catches is shown perhaps show a wider range in their bathymetric according to “types”. distribution. Finally, the composition of the individual hauls was Turning to the boreo-Arctic element, we encounter investigated according to the ichthyogeographic ele an ecological group of fish, most species of which ments of which they were composed. This is shown in show a rather unorthodox relationship to the depth, Table 9 :6 as well as in the Figures 9 :9 A and 9 :9 B and their distribution being mainly governed by tempera thoroughly discussed in the following section. ture. According to S a e m u n d s o n (1949) and others we might regard the following eight species as boreo- 7 For Cover Pages 1 and 2 see pocket in the cover of this Arctic: the rajids Raja radiata Donovan and R. fyllae volume. Liitken, the grenadier Macrourus berglax Lacépède, the (Continued on p. 262) 16* 244 • = Centroscyllium fabricii O = Centroscymnus coelolepis ■ =Raja radiata A = Raja fyllaz □ = Raja spinicauda S - Raja hyperborea ODA =1-3 ODA = 4 - 6 O D A =7-12 ■ s 40 3237 3226 3226 oa 3230 ■3253 8 2 ' 1959 April/M ay 14* Figure 9 :1 A. Distribution of Elasmobranch catches, 1959 cruise. 245 • = Centroscyllium fabricii ■ = Raja radiata ▲ = Raja fyllae Figure 9:1 B. Distribution of Elasmobranch catches, 1960 cruise. 246 Argentina silus 62' 1959 April/May 10’ Figure 9:2 A. Distribution of catches of Argentina silus, 1959 cruise. 247 Argentina silus 751 755 758 '759 761 767 1960 June Figure 9:2 B. Distribution of catches of Argentina silus, 1960 cruise. 248 Micromesistius poutassou 1959 April/May Figure 9:3 A. Distribution of catches of Micromesistius poutassou, 1959 cruise. 249 Micromesistius poutassou 64* 7 6 ? 7«r 769 1960 June Figure 9:3 B. Distribution of catches of Micromesistius poutassou, 1960 cruise. 250 1,4* 10' Gadus morhua Pollachius virens Melanogrammus aeglefinus Molva dypterygia Brosme brosme Gaidropsarus argentatus 3218 O D A = 4 - 6 64’ 3238 3226 1225 3229 3253 3254 3252 62’ 62- 1959 April / May 326] 14* 10- Figure 9:4 A. Distribution of Gadoid catches (except Micromesistius), 1959 cruise. O Gadus morhua % Pollachius virens f l Molva dypterygia I Brosme brosme Figure 9:4 B. Distribution of Gadoid catches (except Micromesistius), 1960 cruise. 252 u* ,0‘ A = Notacanthus phasganorus ■ = Coryphaenoides rupcstris □ = Macrourus berglax a = Lepidion eques ♦ = Aphanopus carbo • = Careproctus reinhardtii 0 = Paraliparis bathybii . - 0 3218 ooA = 1 - 3 2 £ □O A = A - 6 □O A - 7 - 1 0 1 = 500 fi4* 3238 3iyt V 1 " , » 'I »3224 3236 3230 3232 3229 ■ 3231 3255 " ■a V 3253 3252 3254* ■ ■ 1 1959 April / May 3267 • ‘o — -----!------— ------1--— T--1--I---- i 4 1 1 0 # Figure 9:5 A. Distribution of catches of Notacanthidae, Macrouridae, Moridae, Ammodytidae, Trichiuridae, Liparidae and Lophiidae, 1959 cruise. 253 SI = Lepidion eques A = Ammodytes lancea marinus • = Careproctus reinhardtii ® = Lophius piscatorius □ o a = 1 - 3 755 758 763! 761 767 1960 June Figure 9:5 B. Distribution of catches of Notacanthidae, Macrouridae, Moridae, Ammodytidae, Trichiuridae, Liparidae and Lophiidae, 1960 cruise. ■ - Anarhichas minor □ = Anarhichas denticulatus • = Lycodes esmarkii 0 = Lycodes eudipleurostictus ® = Lycodes pallidus pallidus A = Artediellus atlanticus A = Cottunculus microps ♦ = Cottunculus thomsonii * = o □QA =1-3 □ O A = A - 6 □O A = 7-8 3238 .■322''. ^□3236 32p0 3229 g£ 3255 •.e 1959 April/May 1 O’ Figure 9:6 A. Distribution of catches of Blennioidea, Cottidae and Cottunculidae, 1959 cruise. 255 ■ = Anarhichas minor • = Lycodes esmarkii O = Lycodes eudipleurostictus A = Artediellus atlanticus ▲ = Cottunculus microps Figure 9:6 B. Distribution of catches of Blennioidea, Cotddae and Cottunculidae, 1960 cruise. 256 Type composition of redfish catches :| g ia n ts [ mentella inter I marinus Imediate A Sebastes viviparus 1959 April / May Figure 9:7 A. Distribution of Redfish catches, 1959 cruise. Type composition of redfish catches I giants j ’• • mentella inter mediate A = Sebastes viviparus Stat. No. 759 1 specimen type intermediate 14° 10° Figure 9:7 B. Distribution of Redfish catches, 1960 cruise. 17 258 • = Hippoglossus hippoglossus ■ = Reinhardtius hippoglossoides A=Hippoglossoides platessoides specimens = 100 specimens i?237 ■62' 1959 April / May Figure 9:8 A. Distribution of Pleuronectid catches, 1959 cruise. 259 • = Hippoglossus hippoglossus ■ =Reinhardtius hippoglossoides A = Hippoglossoides platessoides A 751 x 62* 1960 June Figure 9:8 B. Distribution of Pleuronectid catches, 1960 cruise. 260 Composition of th e T raw l Catches a rc tic boreal boreo- a rc tic Figure 9:9 A. Ichthyogeographic composition of the trawl catches as percentages of species caught, 1959 cruise. 261 Composition of the Trawl Catches boreal boreo- $> a rctic Figure 9:9 B. Ichthyogeographic composition of the trawl catches as percentages of species caught, 1960 cruise. 262 wolffishes Anarhichas minor Olafsen, A. denticulatus In summary, the ichthyogeographical analysis of Krøyer and Lycodes esmarkii Collett, the redfish Sebastes the demersal fish caught on the Iceland-Faroe Ridge marinus Linnaeus (including the mentella-form) and reveals the following composition: the halibut Hippoglossus hippoglossus (Linnaeus). A. Boreal 18 species The Arctic element is represented by the skates 1) “Bankfish” 7 ” Raja spinicauda Jensen and R. hyperborea Collett, the 2) Atlantic deep water fish 7 gadoid fish Gaidropsarus argentatus (Reinhardt), the 3) “Connecting species” 4 wolffishes Lycodes eudipleurostictus Jensen and L. p. pal B. Boreo-Arctic 8 lidus Collett, the small cottid fish Artediellus atlanticus C. Arctic deep water fish 10 Jordan & Evermann, in spite of the fact that it is taken as “boreo-Arctic, coastal” (!) by S a e m u n d s o n In Table 9:5 the mean values for the distribution of (I.e.), the cottunculid fish Cottunculus microps Collett, the species according to depth and bottom tempera the two liparids Careproctus reinhardtii Krøyer8 and tures as observed during the two cruises of “Anton Paraliparis bathybii Collett, and the Greenland halibut Dohrn” are shown. Where a species was caught at one Reinhardtius hippoglossoides (Walbaum) - altogether ten station only, the values for depth and temperature of species showing a more or less distinct preference for this station are given instead of a mean. In spite of the deep water. scarcity of available data, we arrived in this manner Some remarks should be made concerning the use of at results fitting very well to the expected distribution. the term “Arctic”. The species lumped together here Thus the boreal species are listed on the left, i.e. in the as a group certainly reveal differences with regard to relatively “warm” half of the table, the “bankfish their adaptation to environmental conditions, e.g. some occupying the upper left quarter, the deep-water of them being much more eurythermie than others. species the lower one. In a similar way the Arctic Thus Raja spinicauda, Reinhardtius hippoglossoides and species are found on the “cold” right half of Table 9 :5, especially Cottunculus microps are able to sustain rather whereas the boreo-Arctic fish are widely scattered over high temperatures for a period long enough at least to both sides of its upper half. survive a temporary warming of their habitats. Others, On the other hand, considering the species-compo- as e.g. Artediellus, seem to have successfully established sition of the different stations, no single location is populations adapted to a boreal environment at the occupied by one faunal element only. This is certainly southern edge of their habitats. Since, however, all due to the fact that all of the stations were situated these species reach their maximum abundance in the within the border-area between the boreal Atlantic cold water and since they not only tolerate but seem and the Arctic Norwegian Sea, and the deepest hauls to prefer much lower temperatures than the boreo- suggest what would have been found farther down the Arctic fish, we include them here in the group called slope on either side of the Ridge. Thus, at the wesern- as a matter of convenience “Arctic”, though the term most station at a depth of between 735 and 765 mtand “sub-Arctic ’’might seem to be more adequate for at with a bottom temperature of 4-2° C (stat. 3255) the least some of them. catch comprised a boreal assemblage composed of such According to B a r a n e n k o v a , P o n o m a r e n k o & typical Atlantic deep-water representatives as Centro- S e r e b r y a k o v (1962), the Greenland skate ought to scyIlium, Centroscymnus, Notacanthus, Coryphaenoides, Lepi- be taken as a “w arm ” water fish rather than an Arctic dion, Aphanopus, and Cottunculus thomsonii. In contrast, species. However, the catches of the species in Newfound the easternmost haul (stat. 3267), which took place in land waters of between + 0-65° and — 1 '5 C as well as the Faroe Channel at depths of between 750 and 805 m its occurrence together with R. hyperborea in the Faroe and at a temperature of — 0-2° C, reveals a highly Channel at negative temperatures exclude to our minds Arctic community with Raja hyperborea, R. spinicauda, the Greenland skate from the boreo-Arctic group. Gaidropsarus argentatus, Lycodes eudipleurostictus, L. p. In Table 9:4 the numbers of Cottunculus and Rein pallidus, Cottunculus microps, Reinhardtius hippoglossoides, hardtius are shown in relation to the temperatures Careproctus reinhardtii and Paraliparis bathybii. observed during the two cruises. The Ridge itself-that is, the commercially fished The temperature range between 0° and 2°C seems areas between the 300 m and 500 m isobaths, known to be the preferred one in both species. to the German fishermen as the “Rosengarten —is the typical habitat of a mixed fauna consisting mainly of boreo-Arctic species, with the redfish, the main 8 According to the characters lined out by B u r k e (1 9 3 0 ) the specimens of the Iceland-Faroe Ridge would fall under C. longi- objective of the commercial fishery there, being the pinnis Burke, 1912. However, as long as the taxonomic status of “Leitform” (dominating species). The species com the Greenlandic Careproctus appears to be uncertain, we prefer the prising this community are either eurythermie - the more conservative attitude in referring the specimens to rein true bottom fish - and adapted to sustain rather rapid hardtii Krøyer. 263 Table 9:5. Mean distribution of demersal fish species according to depth and bottom temperatures (1959 and 1960 cruises com bined) Bt.°C 5-6 Depth m. 4-5 3-4 2-3 1-2 0-1 > 0 300-350 Melanogrammus Gadus morhua Hippoglossus aeglefinus hippoglossus 351-400 Pollachius virens Sebastes marinus Sebastes marinus type marinus 401-450 Brosme brosme Micromesistius Anarhichas Reinhardtius Sebastes marinus, poutassou denticulatus hippoglossoides type mentella Molva dypterygia and giants Anarhichas minor Hippoglossoides platessoides 451-500 Lophius Argentina silus Raja fyllae Raja radiata Lycodes piscatorius Ammodytes lancea Lycodes esmarkii eudipleurostictus marinus Cottunculus Artediellus microps atlanticus 501-550 Sebastes Macrourus viviparus berglax 551-600 Raja spinicauda Careproctus reinhardtii 601-650 Notacanthus phasganorus Lepidion eques Coryphaenoides rupestris 651-700 Centroscyllium fabricii 701-750 Centroscymnus coelolepis Aphanopus carbo Cottunculus thomsonii 751-800 Lycodes pallidus Raja hyperborea Gaidropsarus argentatus Paraliparis bathybii changes in bottom temperatures, or are semi-pelagic, Atlantic area. This belt coincides rather closely with and therefore able to avoid such changes by rising to the known distribution of Sebastes marinus s.l. a more suitable water layer. Most of the species The phenomenon of the “overflow” might, we think, involved show a vast geographical distribution, with a be mirrored by the distribution of the demersal fish in particular community forming a characteristic belt of the area investigated. If the distribution of the Arctic varying width marking the borders between the boreal species west of the Ridge could be discovered, perhaps and the Arctic fish fauna along the submarine ridges some clues could be found as to the routes of the Arctic and the edges of the continental shelves in the North water, as well as to the manner in which it may pass 264 Table 9:6 Zoogeographie components of the ichthyo-fauna of the Iceland-Faroe Ridge by stations Spe cies caught Depth Boreal Boreo-Arctic Arctic Characterization Station Bt°C No. m Nos. °// 0 Nos. °/0 Nos. °// 0 of the station 1959 3218 450^t60 2-8 39 30-0 4 40-0 3 300 boreo-Arctic 3223 450 5-1 7 63-6 3 27-3 1 9-1 boreal 3224 440-460 5-1 6 75-0 2 25-0 -- boreal 3225 350 5-4 2 50-0 2 50-0 -- boreal/boreo- Arctic 3226 430-450 2-7 2 25-0 3 37-5 3 37-5 boreo-Arctic / Arctic 3229 450 1-1 1 11-1 3 33-3 5 55-6 Arctic 3230 310 5-6 6 87-5 1 14-3 - - boreal 3231 400 4-1 6 42-8 5 35-7 3 21-4 boreo-Arctic 3232 500-510 3-8 5 83-3 1 16-7 -- boreal 3236 450 _ 4 40-0 6 60-0 -- boreo-Arctic 3237 430 3 42-9 4 57-1 -- boreo-Arctic 3238 650 3-6 7 70-0 2 20-0 1 10-0 boreal deep water 3252 440 3 42-9 3 42-9 1 14-3 boreal / boreo-Arctic 3253 450 i -9 3 27-3 5 45-4 3 27-3 boreo-Arctic 3254 470-480 4-7 4 50-0 3 37-5 1 12-5 boreal/boreo-Arctic 3255 735-760 4-2 9 53-0 4 23-5 4 23-5 boreal deep water 3267 750-805 -0-2 1 10-0 - — 9 90-0 Arctic deep water 1960 751 445 6 5 62-5 2 25-0 1 12-5 boreal 754 466 6 1 50-0 1 50-0 -- boreal10 755 370 2-3 5 83-3 1 16-7 -- boreal 756 450 6 5 71-4 2 28-6 -- boreal 757 400-410 6 5 71-4 2 28-6 -- boreal 758 320-330 3-4 7 87-5 1 12-5 -- boreal 759 480 -0-02 2 22-2 3 33-3 4 44-5 Arctic 761 410 1-2 2 25-0 4 50-0 2 25-0 boreo-Arctic boreal/boreo-Arctic 762 320 1-2 5 55-6 3 33-3 1 11-1 763 400 3 4 44-4 4 44-4 1 11-2 boreo-Arctic 764 500 5 5 71-4 2 28-6 -- boreal 765 500 5-6 5 71-4 2 28-6 -- boreal 766 490-500 4-5 3 60-0 2 40-0 - - boreal 767 480 4 5 62-5 2 25-0 1 12-5 boreal 768 450 3-4 1 16-7 3 50-0 2 33-3 boreo-Arctic 769 480-500 2 4 50-0 3 37-5 1 12-5 boreal/boreo-Arctic 771 470 4-5 3 42-8 3 42-8 1 14-4 boreo-Arctic 9 Only samples of more than 10 specimens of the semipelagic Argentina and Micromesistius are included, the smaller numbers presumably being caught pelagically. 10 Only 10 minutes trawled; net damaged. the Ridge, and as to its extension which may enable Iceland, except Raja spinicauda, which is said to be very the Arctic fishes to extend their ranges. From the rare in the south of this island, and the Greenland species captured by R. V. “Anton Dohrn”, the follo halibut, also very rare to the west of it. The Arctic wing are listed by M u r r a y and H j o r t (1912) as being fish species found on the Iceland-Faroe Ridge therefore among the principal “coldwater” fish of the deep certainly have immigrated from the slope of the Norwegian Sea: Raja hyperborea, Lycodes pallidus, L. Norwegian Sea. So far as the num ber of species is eudipleurostictus, Cottunculus microps, Careproctus reinhardtii concerned, it represents 27-8 °/0 of the total demersal and Paraliparis bathybii. To these fish we may add Raja fish fauna, the number of specimens indeed being a spinicauda, Gaidropsarus argentatus, Artediellus atlanticus, very small one; this, however, may be related to the and Reinhardtius hippoglossoides. According to S a e m u n d - well-known fact that most of the species involved, so n (I.e., Table II) none of these species has ever been when compared with either boreal or boreo-Arctic captured in the warm water to the south or west of species, occur only in small numbers. 265 Table 9:6 and Figures 9:9A and 9:9B show the Table 9:7. percentages of the species composition at the individual Observed bottom temperatures for stations from the faunal point of view. A striking “Arctic fish-stations” similarity can be seen at once in the distribution of Bottom temperatures in °C. the Arctic component when comparing the two cruises. ------Station It then appears that in both years the Arctic species No. Survey No. measured which are found in the deeper grounds to the east 1 2 3 in 1959 as well as to the west of the “top” of the Ridge, with 3218 3 2 1-2 2.8 one exception only, did not inhabit the shallowest 3223 4.5 3.5 5-6 5.1 parts of the Ridge (within the 400 m-contour). The 3226 RsO 0-1 0-1 2.7 percentage of Arctic species decreases from east to 3229 a» 1.2 -0.25 < 0 1.1 west, but in the west apparently it increases again 3231 2-3 ssl 3 4.1 3238 « 5 3-4 3-4 3.6 with increasing depth (1959). Figure 9:9 B illustrates a 3252 s» 1.5 2-3 3 _ rather satisfying relationship between the distribution 3253 0-1 > 2 3 1.9 of these species and the isotherms. Bearing in mind 3254 3-4 4 4-5 4.7 the fact that the hydrographical situation shown on 3255 > 4 2 3-4 4.2 3267 ^ 0 «*0 % 0 -0.2 the map was drawn up some days before the fishery 751 5 2 6 _ stations were done, a close parallelism may not be 759 < 0 0-1 0-111 _ expected. Nevertheless, the stations where Arctic 761 ~ 2 0-1 1-2 _ _ species were captured are situated either inside or 762 <*2 0-1 1-2 763 1-2 2-3 3 _ somewhat in front of the indentations of the isotherms 767 1-2 1 4 _ where the cold water is pushing southwestwards or 768 <*1 2-3 3-4 _ westwards. The fish distribution therefore could suggest 769 1-2 1-2 2 _ a somewhat advanced phase of the hydrographical 771 1-2 4-5 4-5 — situation in which the cold water masses have been 11 Actually measured - 0-02° C. progressing on their way across the Ridge. However, there is also the possibility that the Arctic species might be more or less stationary, their distribution southeastern slope appear to be the main passages rather closely linked with fixed passages of cold water. where the cold water advances in a generally south Not only is the fact that the similarity in the distri westerly direction. In addition, there is the deep bution of these fish between the two cruises favours the Faroe-Bank Channel where the water flows perm a last mentioned possibility, but also the fact that none nently to the northwest only in the lowest depths. of the species involved is a powerful swimmer except Table 9:7 shows the bottom temperatures met with possibly the Greenland halibut. Moreover, some of the during the three surveys of the ICES Expedition for more eurythermie species such as the Greenland skate, those stations of the two respective cruises where Cottunculus microps, and the Greenland halibut were Arctic species were found and the actual measurements encountered actually at rather high temperatures in obtained during the 1959 cruise. some instances during the 1959 cruise. It is shown that six of the twenty stations involved In order to find the extent of the role hydrography always had bottom temperatures of less than 2° C, five plays in the distribution pattern of fish, the sketches of up to 3° C, four up to approximately 4° G, three up to the isotherms close to the sea bottom (prepared on 5°C, and two up to 6°C. For the first 6 stations the board during the two previous surveys of the “Overflow- respective numbers of Arctic fish were 10 species with Programme”) were compared with the final chart of 196 specimens, for the next five stations they were 6 the third survey (prepared by Dr. T a it ) and also with species with 50 specimens. The four stations with a the temperature chart for 1959. Despite the quantita temperature range up to about 4°C gave 7 species tive differences in the distribution of the cold water on with 17 specimens, the next three up to 5° C, 3 species the Ridge, a rather clear trend can be seen as to the with 5 specimens, and the two stations with the directions and th: passages in which the phenomenon warmest temperatures 2 specimens of Cottunculus of the overflow proceeds. The overflow seems to be microps only. Six of the eleven first-mentioned stations closely related to the topography of the Ridge, the are situated along the eastern slope of the Ridge, one cold water, depending upon its weight, being forced in the Faroe-Bank Channel, one on the northern on its way across the Ridge to follow the slopes of the slope and two on the southern, leaving only one two plateaus outlined by the 400 m contour and station in the middle of the Ridge itself. The four forming the top of the Ridge. The shallow furrow stations showing a variation in temperature of up to between the two plateaux as well as the extensive 4°C are the western or southwestern ones, except for 266 station No. 768, which is near the southern slope, 36 species of demersal fish were caught during the where two of the stations of the next group are also two cruises. Eighteen of these are boreal fish, which to be found, leaving one (No. 3238) on the north can be further subdivided into 7 species of “Bankfish”, western slope. The two warmest stations are northern 7 Atlantic deep-water and 4 “Connecting species”. and northwestern respectively. Eight species belong to the boreo-Arctic group, and From the picture drawn from the fish distribution, 10 are Arctic or semi-Arctic respectively. it can be concluded that the Arctic species tend to Since the authors believe that the influence of the follow closely the cold water on its way across the “Overflow” on the distribution of demersal fish can Ridge to the western side, where they are able to find best be understood by studying the exact locations of suitable conditions on the rather steep slope. This slope Arctic species, they have dealt primarily in this paper represents the narrow westernmost fringe of the distri with the habitat pattern of these species. A striking bution area of some of the Arctic species, where, on similarity in the distribution of the Arctic fish can be their way down they meet with the easternmost observed when a comparison of the two cruises is made. outposts of the boreal deep water species, as can be Furthermore, a close relationship appears to exist seen from the trawl catches at stations No. 3238 and between the movement of the cold water, the distri No. 3255. In such situations an increase in the number bution of the Arctic fish species and the topography of of Arctic fish can be observed below 700 m depth, the the Ridge. The cold water, according to its weight, fish apparently becoming crowded by the environ seems to be forced on its way across the Ridge to mental conditions. follow the slopes of the two plateaux forming the sum The routes by which Arctic fish apparently do cross mit of the Ridge. The shallow furrow between these the Ridge are indicated in Figure 9:9B by black plateaux as well as the extensive southeastern slope arrows. It is further concluded that although some appear to be the main passages for both the cold of these species at least are able to tolerate somewhat water and the Arctic fish species. Most of the stations greater variations in temperatures, the main direction involved, especially those showing a rather high pro and the main passages of the “Overflow” must be portion of Arctic fish were found to be immersed in rather constant and that this phenomenon takes place cold water almost every time they were investigated. in relatively short intervals because every investigation In other cases only those species which are more of the Iceland-Faroe Ridge reveals the existence of eurythermie were caught at somewhat higher bottom the Arctic fish element at almost the same localities. temperatures. Since most of the Arctic fish are rather slow and presumably unable to avoid sudden changes in tempera ACKNOWLEDGEMENTS tures by active emigration, the phenomenon of the The authors are indebted to Dr. J. B. T a it of the overflow must take place in relatively short intervals Marine Laboratory, Aberdeen, by whose permission and mainly by the same passages in order to enable the bottom chart for the third hydrographic survey of the Arctic fish species to establish their habitats on the the “Overflow-Programme” could be used, and to Dr. Ridge. The steep western slope of the Iceland-Faroe G. T o m c z a k of the Deutsches Hydrographisches In Ridge seems to represent the westernmost fringe of the stitut, Hamburg, who made available some prelimi distribution area of the Arctic fish fauna. Here they nary charts of the first two surveys, prepared on are crowded in by the environmental conditions and board the R. V. “Gauss”. Miss F. W. C r o u s e helped therefore increase in numbers again at a depth of in revising the English wording. more than 700 m, where they build up a peculiar community with the easternmost outposts of the boreal s u m m a r y deep-water species. Immediately after the third hydrographic survey of the “ICES-Overflow-Programme”, the R. V. "'Anton Dohrn” undertook a trawling survey in order to get REFERENCES some information concerning the relationship between B a r a n e n k o v a , A. S., P o n o m a r e n k o , V. P. & S e r e b r y a k o v , V. P., fish distribution, water temperatures and depth. The 1962. “Thorn-tail skate (Raja spinicauda Jensen) in the Barents Sea”. Probl. Ichthyol., 2,1(22): 18-24. results of this and a similar survey made in 1959 are B u r k e , V., 1930. “ Revision of the Fishes of the Family Lipari- reported and discussed. Distribution charts of the dae” . U. S. Nat. Mus. Bull., 150: 1-204. individual fish species as well as of the ichthyogeo- C o h e n , D. M., 1958. “A Revision of the Fishes of the sub-family graphic components are given for both cruises. Argentininae”. Bull. Fla St. Mus. biol. Sei., 3 (3): 93—172. M u r r a y , J. & H j o r t , J., 1912. “ The Depths of the Ocean” , The fish fauna of the Iceland-Faroe Ridge is 821 pp., London. composed of three major elements, viz. a boreal, a S a e m u n d s s o n , B., 1949. “ Marine Pisces” . Zoology Iceland, 4 (72) : boreo-Arctic, and an Arctic component. As a whole 1-150. 267 LIST OF DEMERSAL FISH SPECIES CAUGHT BY F. R. V. Family Ammody tidae - the Sand Eels ANTON DOHRN ON THE ICELAND-FAROE RIDGE IN 1959 20) Ammodytes lancea marinus Raitt, 1934 A N D 1960 Family Anarhichadidae — the Wolffishes Family Squalidae — the Picked Dogfishes 21) Anarhichas minor Olafsen, 1772 —the Spotted 1) Centroscylliumfabricii (Reinhardt), 1825 Wolffish 2) Centroscymnus coelolepis Bocage & Capello, 1864 22) Anarhichas denticulatus Krøyer, 1844 Family Rajidae —the Rays and Skates Family Zoarcidae - the Eel Pout Family 3) Raja radiata Donovan, 1808— the Starry Ray 23) Lycodes esmarkii Collett, 1880 4) Rajafyllae Liitken, 1887 24) Lycodes eudipleurostictus Jensen, 1902 5) Raja spinicauda Jensen, 1914 —the Greenland 25) Lycodes pallidus pallidus Collett, 1879 Skate Family Scorpaenidae — the Rockfishes 6) Raja hyperborea Collett, 1878 26) Sebastes viviparus Krøyer, 1845 —the Lesser Family Argen tin id ae — the Silver Smelts Redfish 7) Argentina silus (Ascanius), 1775 —the Greater 27) Sebastes marinus, type marinus (Linnaeus), Silver Smelt 1758 - the Redfish Sebastes marinus, type mentella Travin, Family Notacanthidae - the Spiny Eels 1951 - the Redfish 8) Notacanthus phasganorus Goode, 1881 Sebastes marinus, type “intermediate” - the Redfish Family Macrouridae - the Grenadiers Sebastes marinus, type “giants” - the Redfish 9) Coryphaenoides rupestris Gunnerus, 1765 10) Macrourus berglax Lacépède, 1802 Family Cot tidae —the Bull-heads 28) Artediellus atlanticus Jordan & Evermann, 1898 Family Gadidae-the Cod Family 11) Gadus morhua Linnaeus, 1758 — the Cod Family Cottunculidae 12) Melanogrammus aeglefinus (Linnaeus), 1758 — the 29) Cottunculus microps Collett, 1875 Fladdock 30) Cottunculus thomsonii (Günther), 1882 13) Pollachius virens (Linnaeus), 1758-the Coal- fish Family Liparidae-the Sea-snails 14) Micromesistiuspoutassou (Risso), 1826 - the Blue 31 ) Careproctus reinhardtii Krøyer, 1862 Whiting 32) Paraliparis bathybii Collett, 1879 15) Molva dypterygia (Pennant), 1784-the Blue Family Pleuronectidae — the Flounders Ling 16) Brosme brosme (Ascanius), 1772-the Torsk 33) Hippoglossus hippoglossus (Linnaeus), 1758 —the 17) Gaidropsarus argentalus (Reinhardt), 1838 Halibut 34) Reinhardtius hippoglossoides (Walbaum), 1792 — Family Moridae the Greenland Halibut 18) Lepidion eques (Günther), 1887 35) Hippoglossoides platessoides (Fabricius), 1780 — the Long Rough Dab Family Trichiuridae — the Flair-tails 19) Aphanopus carbo Lowe, 1839-the Black Scab- Family Lophiidae — the Angler Family bardfish 36) Lophius piscatorius Linnaeus, 1758 —the Monk Rapports et Procès-ver baux, Vol. 157, Ch. 9. » 2.8 *3.6 *5,6 «1,1 62' 1959 April / May Cover page 1. Bottom temperatures actually measured during the 1959 cruise. Rapports et Procès-verbaux, Vol. 157, Ch. 9. 14* 10* Cover page 2. Bathymetric chart of the Iceland-Faroe Ridge (by hectometres).