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1 t- ISSN CANADIAN TRANSLATION OF FISHERIES AND AQUATIC SCIENCES N o Reduction of algal vegetation in Helgeland coastal waters by K. Sivertsen and A. Bjorge FIMIERIES ez OCEANS CANADA PECIIES ET OCEANS ICAN LIBIURY I leileuorifii.',(ye) 2eA trriwww,.:( 1,1 K.1 - Original Title: Reduksjon av tareskogen paa helgelandskysten From: Fisken Hav (4): 1-9, 1980 Translated by the Translation Bureau (LT) Multilingual Services Division Department of the Secretary of State of Canada Department of Fisheries and Oceans Maritimes Regional Library Halifax, N.S pages typescript

2 t_ -7 DEPARTMENT OF THE SECRETARY OF STATE TRANSLATION BUREAU MULTILINGUAL SERVICES DIVISION CANADA SECRÉTARIAT D'ÉTAT BUREAU DES TRADUCTIONS DIVISION DES SERVICES MULTILINGUES TRANSLATED FROM TRADUCTION DE INTO EN AUTHOR - AUTEUR Norwegian Knut Sivertsen, Arne Bjorge English TITLE IN ENGLISH TITRE ANGLAIS Reduction of algal vegetation in Helgeland coastal waters TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ÉTRANGERE (TRANSCRIRE EN CARACTÈRES ROMAINS) Reduksjon av tareskogen paa heleelandskysten REFERENCE IN FOREIGN LANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE FOREIGN CHARACTERS. RÉFÉRENCE EN LANGUE ÉTRANGÉRE (NOM DU LIVRE OU PUBLICATION), AU COMPLET, TRANSCRIRE EN CARACTÈRES ROMAINS. Fisken Hav REFERENCE IN ENGLISH - RÉFÉRENCE EN ANGLAIS Fish - Sea PUBLISHER.- ÉDITEUR PLACE OF PUBLICATION LIEU DE PUBLICATION Marine Research Inst. of Fisheries Directorat Denmark YEAR ANNÉE 1980 DATE OF PUBLICATION DATE DE PUBLICATION VOLUME ISSUE NO. NUMÉRO 4 PAGE NUMBERS IN ORIGINAL NUMÉROS DES PAGES DANS L'ORIGINAL 1-9 NUMBER OF TYPED PAGES NOMBRE DE PAGES DACTYLOGRAPHIÉES 11 REQUESTING DEPARTMENT MINISTÉRECLIENT DF0 TRANSLATION BUREAU NO. NOTRE DOSSIER N BRANCH OR DIVISION DIRECTION OU DIVISION PERSON REQUESTING DEMANDÉ PAR SIPB Allan T. Reid TRANSLATOR (INIT ( ALS) TRADUCTEUR (INITIALES) L9' YOUR NUMBER VOTRE DOSSIER N DATE OF REQUEST DATE DE LA DEMANDE (REV. 2/68)

3 I+ Secretary Secrétariat of State d'état MULTILINGUAL SERVICES DIVISION TRANSLATION BUREAU DIVISION DES SERVICES MULTILINGUES BUREAU DES TRADUCTIONS Clients No. No du client Department Ministère Division/Branch Division/Direction City Ville DFO S.I.P.B. Bureau No. Nedu bureau Language Langue Translator (Initials) Traducteur (Initiales) Norwegian LT Fisken Hav :1-9 REDUCTION OF ALGAL VEGETATION IN HELGELAND COASTAL WATERS Knut Sivertsen Institute of Marine Biology and Limnology, Marine Botany, Oslo University and Arnb'SWie;rai.iiii-e. lté -Sêai-ch Inst. of the Fisheries Directorate Reduced densities of Laminaria have been report ed from coastal waters in SOr-TrOndelag, Nord-TrOndelag and Nordiand counties. A provisional study of algal vegetation and benthic fauna was made by -. divin g west of Vega in Helgoland, N(?riland county (position 65 G 41' 11 Q 43'E), October The study revealed a significant difference in sublittoral density of sea urchins between three locations selected for abundant, scattered and no Laminaria gro th. Strongylocentrotus droebachiensis dominated over Fchinus escuientus at all three locations. The lowest sea urchin density was found et the location with abundant Laminaria, and a high density of sea urchins at the location with no or scattered Laminaria. It is therefore presumed that grazing by increasing numbers of pea urchins is a major factor causing a reduction of Laminari:I. The catfish (Anarhichas lupus) may be the most important predator on sea urchins in these waters, and the catfish is preyed upon by seals. It is therefore suggested that increasing local StocOt«grey seals (Halichoerus grypus), may have influenced the catfish abundance, an çl thus allowed the sea urchins to increase with a subsequant detrimental effect on the vegetation of Laminaria. erre ne, n r701

4 2 Introduction Depletive grazing of kelp beds in Nova Scotia by the common green sea urchin Strongylocentrotus drobachiensis has been described by Mann and Green (1972), Breen (1974), Breen and Mann (1976) and Lang and Mann (1976). The same phenomenon has been recorded in Newfoundland by Himmelman and Steele (1976) and in New Brunswick by Arnold (1976). Once the kelp beds are fully consumed, the sea urchin eats the embryonic plants when these begin to grow, thus preventing a regrowth. Lang and Mann (1976) stated that a denuded kelp bed stays in that state for at least four years, while Breen and Mann (1976) showed that the kelp Laminaria longicruris begins to grow again in a few months after sea urchins are removed experimentally from a kelp-growing area. Svendsen (1972) found that regrowth takes place in Norway after three or four years. Himmelman and Steele (1971) have discovered a number of predators on sea urchins (Strongylocentrotus drobachiensis) in Canadian waters: starfishes, lobsters, crabs, lumpfish, American plaice, gulls, eider ducks, and sea otters. Mann and Breen (1972) claim that lobster is the most prominent predator. Whemlobster density is low, sea urchin populations can grow uncontrolled. Few observations are available about the effect of the grazing on kelp by sea urchins in European waters. However, Jones and Kain (1967) proved that an experimental removal of Echinus from an area at the Isle of Man had an obvious effect on kelp. Jorde and Kalvestad (1963) described a conspicuous reduction in algae vegetation in Hardangerfjorden. They claimed that grazing by Echinus esculentus and E. acutus was a major cause of the decline. Besides, the snails Lacuna vincta and Patina pellucida feed on kelp.

5 3 Although especially P. pellucida is common along the Norwegian coast, Kain and Svendsen (1969) claim that its grazing has no significant effect in Norway. Some quantitative kelp studies were carried out on the Helgeland coast by Grenager (1955). The algal vegetation of this coastal area has not been studied by others. The Marine Research Institute of the Fisheries Directorate has received several communications from fishermen of the Helgeland coast, who express their worry about the decline of large kelp vegetation in several locations. They point out particularly that the habitats of the young coastal cod are destroyed, which can affect trap fishing. Some preliminary studies of kelp vegetation and bottom fauna were carried out in October 1979 west of Vega along the Helgeland coast in connection with seal research. This report presents the results of the studies. Materials and methods Three stations were chosen in the archipelago west of Vega: - Station I - without Laminaria - Station II - with sporadic occurrences of Laminaria - Station III - with dense Laminaria beds At all stations the bottom was made up of rock and big boulders, sloping towards northwest. All stations were just about equally exposed. Station I was in position "N 11 42'30"E, while the other two were located west of it in a straight line, each station being at a distance of about 200 m from the other. Observations were made by diving. Macroscopic algae and animals were ut!rnrup Tr: in..' M -- '; : -.

6 14 inventoried at each station from a depth of about 5 m to the shore. Density of sea urchins was measured by counting all individuals inside an iron hoop with a 40 cm diameter. Ten countings were carried out at each station with the iron hoop randomly placed at different depths from three to five metres below the upper balanus line. Results Flora Table 1 illustrates the algal vegetation at the three stations. All stations had about the same species composition in the littoral zone, but the sublittoral zone showed great differences. The large kelp Laminaria hyperborea was fully absent at Station I, which had only calcareous algae. The large kelp occurred sporadically at Station II, and Station III had dense kelp beds. The species composition was more or less similar at Stations II and III except that there were essentially more epiphytes on the large kelp at Station III. Fauna All three stations had almost similar species composition (Table 2) and quantitative proportions of animals, with the exception of the epiphytic fauna. As Table 3 shows, one essential difference was observed between the stations, consisting of different densities of the sea urchins Strongylocentrotus drobachiensis and Echinus esculentus. The S. drobachiensis density was significantly lower and the E. esculentus density significantly higher at Station III, in comparison with the other two stations.

7 Table 1. Algal vegetation observed on rocky shores in three locations in the Vega area 5 Station No. Algae observed 11 III Littoral zone Pelvetia canaliculata rucus vesiculosus f. evesiculosus Cladophora rupestris RhiiocloniUm riparium Polvsiphonia urceolata x x x Volysiphonia brodiaei Trailliella intricata Paimaria palmata Coranina officinalis Fucus serràtus Sublittoral zone Alaria esculenta Desmarestia aculeata Laminaria h - perborea Laminaria saccharina Calcareous algae Epiphytes on Laminaria hyperborea Rhodomela lvcopodioides Palmaria palmata Polysiphonia urceolata Audouinella purpurea

8 ' 6 Table 2. Benthic fauna observed on rocky shores in the Vega area. Station No. Algae observed I II III - littoral zone Littotina saxatilis x x x Liitorina littorea x x x Balanus.balanoides x - x x Patelle vulqata x X x Thais lapillus x x x Sublittoral zone Carcintls haencs Modidius hodiblus Pagurus bernhardus nuccinum undatum Ophiotrix fragilis Asterias rubens Echinus esculentus Strongylocentrotus droebachiensis Alcyonium digitatum Actinaria X Epiphytes on Laminaria hyperborea Bryozoa Uvtilus edulis Strongylocentrotus droebachicnsis A comparison between the densities of the two sea urchin species shows that at Stations I and II S. drobachiensis dominated fully, and that even at Station II, which had the highest density of E. esculentus measured, S. drobachiensis still constituted 61.3% of the number of sea urchins.

9 Table 3. Counts per test area (0.126 m 2 ) and densities per m2 of S. drobachiensis (S) and E. esculentus (E) in ten randomly located test areas at each of the three stations west of Vega. 7 Station I Station II Station. III S E S E S E Average Number Standard deviation Number of individuals/m 2 9,4 0,4 11,4 0, ,9 4,33 0,7 6,71 1,0 3,13 2,6 74,8 3,2 94, ,6 23,1 Discussion Tables 1 and 2 show that the stations differed from each other most in the sublittoral zone. The large kelp (L. hyperborea) was a main species in the sublittoral community, constituting a fertile substrate and a shelter for other plants and animals. That the large kelp was either lacking or strongly declined at Stations I and II shows that grazing had been too intensive. The essentially higher density of S. drobachiensis in locations where the large kelp was absent or strongly declined, probably means that S. drobachiensis plays an important role in the decline. At Station III the kelp bed was probably still in a balanced state. According to Lang and Mann (1976), the normal density of S. drobachiensis in kelp beds at Nova Scotia is 36.8 individuals/m 2. At Station III, this density was 36.6 ind./m 2. The lower density of E. esculentus at Stations I and II in comparison with that at Station III can be possibly attributed to competitive

10 8 conditions between E. esculentus and S. drobachiensis, under which conditions the former is to a certain degree suppressed by the latter. If this assumption is correct, E. esculentus cannot be essentially ipportant with regard to the decline of kelp beds west of Vega. Breen and Mann (1976) claim that a sea urchin population grazes on large plants, for instance by climbing up a plant one after the other, and when there is a sufficient number of sea urchins on a plant, their weight makes it bend down, and the sea urchins keep it down to consume it completely. The same procedure was observed at Station II at Vega. While lobster may be the foremost predator of sea urchins in Nova Scotia, its density is so low around Vega that it is not an important factor. North Norway constitutes the northern limit of lobster occurrence. Atlantic wolffish (Anarhichas lupus) is more likely to be the main predator. Information obtained from two Vega fishermen shows that the quantity of Atlantic wolffish as a secondary catch by fish trap has decreased by 4-5 % from what it was 15 years ago. A local fish wholesaler is of the opinion that the annual quantity of landed Atlantic wolffish has been reduced to less than 10 of the annual quantities before Atlantic wolffish is caught as a byproduct by several other fishing methods as well. However, the fishermen of Vega claim that the decline in Atlantic wolffish catches can be blamed mainly on the seal. Benjaminsen et al. (1977) describes a significant increase in gray seal (Halichoerus gryphus) populations along this coastal stretch, and it is known from Canada that Atlantic wolffish is part of the gray sears diet (Mansfield and Beck 1977). The information collected indicates that a decline of kelp beds at Vega has been going on for the last 10 years, and that it is increasing. A similar decline has been recorded at Hitra in southern TrOndelag during

11 9 the last 3-4 years. The master of a kelp trawler reportea that decline in kelp beds can be observed in certain locations along the TrOndelag coast from Hitra to Vikna. He was not aware of such decline at Nordmpre. Fishermen from Smpla had not noticed any decline either. This study shows that significant decline has taken place in kelp beds in some locations west of Vega, and that the same tendency can probably be observed in a coastal area stretching towards south until Hitra. More studies along the coast have to be carried out to determine the extent of the decline. Whether the decline is increasing or decreasing can be found out only by long-term studies. The studies were carried out in connection with the inshore seal project of the Marine Research Institute and financed by the Norwegian Fisheries Research Council (NFFR I ). Jan Rueness from the Institute of Marine Biology and Limnology at the University of Oslo, and Terje Benjaminsen from the Marine Research Institute of the Fisheries Directorate participated in the planning of the studies. The manuscript was prepared by Torger Oritsland, Marine Research Inst. of the Fisheries Directorate.

12 Literature 10 ARNOLD, D.C Local denudation of the sublittoral rringe by the green sea urchin, Strongylocentrotus droebachiensis (0.F. Muller). Canad. Fld.Nat., 90: c.,<) BENJAMINSEN, T., BERGFLODT, B., HUSE, I. BRODIE, P. og TOKLUM, K UndersOkelser av havert pà norskekysten fra Lofetc tu l FrOya, september-november Fiskerinm - inclens FcrsOksfond, Rapporter, r1 77(1): ) BREEN, P.A Relation am,m,: lobsters, sea urchin and kelpf in Nova Scotia. Ph. D. thesis, Dalhousie University, Halifax, Nova Scotia. 1q0 p. 4,) BREEN, P.A. and MANN, K.H Destructive grazing of kelp by sea urchins in eastern Canada. J. Fish. Res. Bd Can., 33: e5) GRENAGER, B Kvantitative undersokelser av tareforekomster i SOr-Helgeland 1952 cg Rep. Norw, Inst. Seaweed Res,, 7: IiIMME,LI,nN, J.H. and STEELE, D.H Foods and predators of the green sea urchin Strongylocentrotus droebachiensis in Newfoundland waters. Mar. Biol. (Berlin), 9: ) JONES, N.S. and KAIN, J.M Subtidal algal colonization following the removal of Echinus. Helgol. Wiss. Meeresunters., 15: ) JORDE, I. and KALVESTAD, N The natural history of the Hardangerfjord. 4. The benthonic algal vegetation. Sarsia, 9: e7) KAI, J.M. and SVENDSEN, P A note on the behaviour of Patina pellucida in Britain and Norway. Sarsia, 38:

13 /0) LANG, C. and MANN, K.H Chan.:Iùs in sea urchin population after the destruction of kelr beds.mar. Biol., 36: MANN, K.H. and BREEN, P.A The relation between lobster abund:lnce, sea urchins alui kelp beds. J. Fish. Res. Bd Can., 29: MANSFIELD, A.W. and BECK, B i. The grey seal in eastern Canada. Tech. Rep. Fish. nsr. Serv. Can., 704: /3)SUNDSEN,P.1972.Noenobservas7ioner. over,tay er t. 'e li g gjen- vekst av stortare Laminaria hyperborea. Fiskets Ganc, 58: Benjaminsen, T., Bergflodt, B., Ruse, I., Brodie, P. and Toklum, K Gray seal studies on the Norwegian coast from the Lofoten to Froya, Sept.-Nov Reports of the Experimental Foundation of the Fishery Industry, 1977 (1) : Grenager, B Quantitative studies of kelp beds in southern Helgeland 1952 and Rep. Norw. Inst. Seaweed Res., 7 : Svendsen, P Some observations on kelp trawling and regrowth of the large kelp Laminaria hyperborea. Fiskets Gang, 58 :