15e» 0-7041-31/&

t_Canadian Translation of Fisheries and Aquatic Sciences No. 5067

Coastal seal investigations: cruise reports LIBRARY «. FISHER TES AND .00EA1. BIBLIOTI IÈQUE A. Bjorge, B. Bergflodt, and K.A. Fagerheim PikIIES ET OCÉANS

Original title: Kystselundersokelser

In: Fiskeridirektoratets havforskningsinstitutt, Bergen, Norway, 46 p., 1980

Original language: Norwegian

Available from: Canada Institute for Scientific and Technical Information National Research Council Ottawa, Ontario, Canada R1A 0S2

1984

79 typescript pages Secretary Secrétariat of State d'État

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Title in English or French - Titre anglais ou français Coastal Seal Investigations

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Kystselundersokelser

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Cruise Reports

Publisher - Editeur Page Numbers in original DATE OF PUBLICATION Numéros des pages dans DATE DE PUBLICATION l'original Institute of Marine Research Issue No. 1 - 46 Year Volume Place of Publication Année Numéro Number of typed pages Lieu de publication Nombre de pages dactylographiées Bergen, Norway 1980 79

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Coastal Seal Investigations

Cruise Reports

A. Bjorge, B. Bergflodt and K. — A. Fagerheim Institute of Marine Research, Directorate of Fisheries Bergen.

SEC 5-25 (Rev. 82/11) Canadâ 2 .

Preface

The Institute of Marine Research has since 1975 carried out field studies on coastal seals (grey seal and harbour seal) between Stadt and Lofoten. The field work was carried out during one or two short cruises yearly from 1975 to 1980. The(collectedImaterial\from the cruises is now being worked up and reports on the coastal seal biology, stock size and their relationship to the fisheries will become available in the new year 1981. Due to considerable interest in our field observations, we have found it convenient to collect the cruise reports in one volume. The field trips from 1975- 77 have been published earlier, but the 1977-80 reports are only type- written and originally intended for internal use. Terje Benjaminsen led the field work up to 1977 and Torger Ôrritslan d has been the project leader all along. The cruise reports have different authors) and it is indicated in the report who participated in the work. Everyone is hereby thanked for their contribution.

Arne Bjbrge Bjorn Bergflodt Kjell-Arne Fagerheim

_ s 3.

t.F TABLE OF CONTENTS

Page Counting of grey seals along the Norwegian coast from Halten-Froam to Bode) and studies on the parasite infection in fish at Vega. 1. 5.

Grey Seal investigations on the Norwegian Coast from Lofoten to Froya, September - November 1976. 8. 20.

Harbour Sealand Grey Seal_investigations on the Norwegian coast from Nordmbre to Setrhelgeland in 1977. 19. 43.

Harbour Seal investigations on the More and Trondelag coasts in 1978. 24. 54.

Grey seal investigations on the coast between Statt and Bronnàysund in 1979. 32. 62.

Grey seal investigations in the whelping period in the fall of 1979. 37. 68.

Harbour seal and grey seal investigations in the summer of 1980. 42. 74. 4

"Jaktinteressen synes fremdeles à vmre liten hva haverten angâr"

"The interest in hunting still seems to be low with respect to the grey seal." Reprint of "Reports" no. 1-1976.

Counting of Grey Seals on the Norwegian Coast from .p. 1 Halten-Froan to Bod8 and Studies on the Parasite Infection in Fish at Vega. by Terje Benjaminsen, Bjorn Bergfledt and Ingvar Huse, Institute of Marine Research.

Introduction

In the early 1960Is, the number of whelping grey seal females (Halichoerus grypus) on the coast between Halten- Froan and Bode was estimated to be about 600 animals (Oynes, 1964). At that time the grey seal was protected in Sor- Trbndelag county (Royal Resolution of April 24, 1953) and there was little interest in hunting this seal species. In 1973 all seal species were totally protected in Southern Norway from the Swedish border up to and including Sogn and Fjordane County, and protected from May 1 to November 30 further north along the Norwegian coast (Royal Res. of April 13, 1973). In this area there are also two nature reserves > Bliksvaer and Ytre Vikna where seals are totally protected within two kilometres from the outer borders of the reserve. (Royal Res. of Dec. 4, 1970 and Nov. 16, 1973). "The hunting interest" still seems to be low with respect to the grey seal. As pointed out by dynes' (1964) the skins of the grey seal are low in demand and the value of the pelt is low compared with our other coastal seal, the harbour seal (Phoca vitulina). 0 •

Through the Norwegian Fishermen's Organizatione it was reported by local fishermen's organizations in 1974 and 1975 that the seal population in Southern Helgeland had increased in number and that this had led to high exploitation of fisheries resources, damage to fishing gear and spread of parasite infection of fish in the area. From earlier studies in Great Britain (Young, 1972) and Canada (Scôtt and Fisher, 19 -%) it is known that the grey seal is the most important host animal for the parasitic roundworm (nematode) Phocanema decipiens (=Terranova decipiens) which spilds part of the larval stage in fish. It is this round- worm larva that can be found as "kveis" ("cyst") in the flesh of the fish (Berland, 1973). The problem had been identified before, and as early as in the summer of 1974, the Institute of Marine Research first attempted to count grey seals and to study the nematode infection of fish near Vega, (Benjaminsen et al., 1975). It was then found that the nematode infection was so high in this area that the fish from some fishing grounds could not be sold, and that some fishing grounds and fishing methods had been given up. About 50% of 30 cod and more than 90% of 20 cusk that were studied at a fish buying station at Kirki;y in Vega were infected by nematodes in the flesh. Poor weather conditions hindered the counting of seals, but it was confirmed that the seal population seemed to be increasing at Vega. New investigations were carried out at Vega between July 7 and 9, 1975, and in the fall of 1975 funds were made 7. available by the Fishing Industry Research Fund for more extensive studies of grey seals in the whelping period. The investigations were chiefly aimed at mapping the grey seal pupping areas on the coast from Froan to Bod6 and to find out if the pups could be counted from an airplane. In some localities the aerial counting was to be confirmed and tagging and collection of material for parasite studies carried out. These activities - are described in the following together with the counts and parasite studies carried out at Vega in July 1975.

Seal Counting at Vega in JulY 1975

Counting of seals was carried out from a motor boat in the area southwest to north of Vega in the period July 7- 9. The weather was good with good visibility. Most of the animals observed were grey seals, a total of 33 animals. Only 3 harbour seals were seen. Two of the seals were too far away to be identified as to species. Most of the grey seal observations were made in Fuglevaer west of Vega and off Bremstein. It is probable that some of the grey seals that pup in the area in the fall had migrated in search of food so that the count does not give a correct picture of the population in the area.

Seal Counting from Froan to Bode) in October 1975

Grey seals pup on the outer skerries and small islands along the coast, chiefly from Mbre to Nordland in the period 8.

September - November. The pups are born with a long-haired

white fur which they lose after 2 - 3 weeks. After moulting the pups have a short-haired grey pelt. The first weeks after birth the pups spend all their time ashore. By counting in the middle of the pupping period, a minimum estimate of the number of pups born can be made. The sexually mature females have a pup each year and comprise about one fourth of the population of one-year old and older animals. The total population can be estimated by multiplying the number of pups by four. Using Brônnbysund as a base, most of the knomm pupping areas for grey seal along the coast from Froan to Bodo were investigated from the air between October 8 and 16. Total p. 2 flying time was 12 hours and 30 minutes. Cessna seaplane was leased from Norwing. The track covered is shomm in Fig. 1 and Fig. 2. The largest number of pups, a total of 46, was spotted at Halten- Froan, but this area was not completely covered since the plane had to return when it was'low on fuel. Oynes (1964) estimated the numbers of whelping grey seal females at Halten-Froan to be 300. Blix (1974) investigated all islands in the Halten- Froan area from a helicopter. He found 21 grey seal pups and estimated the average age to be ca. 3 weeks. On October 20,1975, he counted a total of 50 grey seal pups in the area. Of these,15 were seen on Melsteinen east of Halten. Most of the pups had then lost the white pelt, (Blix, personal

communication). No grey seal pups were found in the area Vikna- ; Sklinna. bynes (1964) indicates that a total of 100 grey seal pups are born yearly here. It is therefore reason to believe that whelping had not started when the flight was

carried out on October 8. In the Vega area, 25 pups were counted. The aerial counts were here checked by counting from a boat on mo.st of the islands. This count was carried out 2 days after the -Lue SoL±J flight, and 14 pups were then counted j veYllr-from the air. But of these, two pups were probably younger than 2 days. It appears as if aerial counting is quite accurate. Most of the animals had just been born so that it can be assumed that it was early in the whelping period and that a larger number of grey seals pup in this area. Ôynes (1964) estimated that 50 pups were born here each year. On the Floholmene island group to the southwest of Traena, a total of 10 pups were observed on October 9. On October 16, the number had increased to 22 pups:The/le is reason to believe that this is an important whelping area for grey seals in Nordland county. In Melby we observed a total of 12 pups that appeared to be newly born, Oynes (1964) gave the number here as 25 pups. Since whelping had only just started when the aerial survey was carried out, the numbers can only be considered to be minimum estimates of the number of whitecoats from

Halten-Froan to Bode). A total of 106 grey seal pups, 49 adult grey seals, 22 harbour seals and 10 seals that could not be identified:, were counted. - 10.

Parasite Investigations

There are four major types of roundworm larvae or "kveis" (cysts) in fish: Contracaecum and Phocascaris on the organs in the stomach cavity, Anisakis in the stomach cavity and on the liver where it is clearly visible and Phocanema that also occur in the organs in the stomach cavity, but prefers fish muscle. (Berland, 1973). In our waters it is Phocanema decipiens that is the greatest problem with respect to the marketing of fish. The sexually mature P. decipiens are found in the stomach of seals and their eggs go into the water with the seal excrements. The eggs hatch and are eaten by an invertebrate animal, probably a crustacean living on the bottom. The larvae remain in the crustaceans until eaten by a fish. The larvae then move from the fish intestine into the stomach cavity or into the flesh where they remain until the fish is eaten by a seal. In this life cycle all three stages are necessary in order for the nematode to live and reproduce. According to Young (1972) the size of the seal population is the most important factor determining the number of nematodes in the fish. He demonstrated that the grey seal has many more P. deqinienz in the stomach than the harbour seal. Also in Canada (Mansfield 1966)Plas\itlbeen demonstrated that there is a connection between the grey seal population and nematode infection in fish. Scott and Fisher (1958) showed that the grey seal had five times as many P. decipiens in the stomach as harbour seals on the east coast of Canada. • 11.

According to fishermen in Sèir-Helgeland, there has been a sharp increase in the number of nematodes in fish flesh in recent years. This especially appliesto fish taken in the area frequented by grey seals. The parasites are especially plentiful in fish from shallow areas, especially inshore cod. Studies of fish taken in the Vega area confirm this. Experimental fishing was carried out in five ar'eas north of Vega. It is only in Holandsvika, close to a pop- ulated area, that there are no seals. Both harbour seals and grey seals occur in the other three areas. At Lanan the fishery was chiefly carried out at 40 meters'depth. Cod there had an average of 15 nematodes in the flesh and 6 in the stomach cavity. No fish was without parasites, and the highest numbers were 70 and 48 in the only two inshore cod caught. These also had most nematodes in the stomach cavity. Two cod caught at 80 metres deep in the Kilvaer Fjord had respectively 1 and 0 nematodes in the flesh and one cod caught 100 metres deep off Skjaervaer had L. nematodes in the flesh. Cod taken at 30 metres in Holandsvika had an average of one parasite in the flesh. For comparison it can be mentioned that Young (1972) who studied the parasite infection in five areas in Great Britain, found average values for P. decipiens that varied from 0.5 to 4 larvae per fish. Platt (1974) studied the occurrence of P. decipiens and Anasakis in cod in North Atlantic and Arctic waters. He found the highest average values for P. decipiamin waters around Iceland and the Faroe Islands where cod from certain areas had 8.4 larvae per fish. In 12.

Lofoten and the Barents Sea, he only found 0.2 and 0.6 larvae per fish, but here the Anisakis infection was considerable, up to 10.2 larvae per cod on the average. He compared the high infection rate of P. decipiens at Iceland and Faroe Islands with the grey seal populations in these areas and P. 3 indicated that the Anasakis infection could have a connection with the whale population which is the most important host animal for this parasite. Five samples of fish flesh from cod and cusk collected during an experimental fishery at Vega in July 1974 have been studied by Bjorn Berland, Zoological Laboratory, University in Bergen. Many roundworm larvae were found encapsulated in the muscles of the belly flaps. Some larvae that were more closely investigated were all P. decipiens (III - stage larvae). Anisakis larvae were not found in the fish flesh, but can still have been present in the stomach cavity. The stomach from an 11 year old grey seal female collected in the Fuglevaer area on October 15, 1975 contained about 3050 nematodes, both small and relatively large individuals. Most of these were loose in the stomach, but some had fastened themselves to the stomach wall. Otherwise, the stomach contained a few fish bones and the half digested tail of a small fish. This is probably the highest number of nematode larvae that has been registered in a seal stomach. Of the 30ratdomly picked individuals, one Contracaecum was found (IV - stage, probably C. osculatum). All the others were identified as P. decipiens. Many of them were larvae (III - stage) of the same typeYfound in fish, and some of 13. these were in the process of shedding their skins (moulting). Otherwise both sexually mature and immature individuals were found. Bje.rn Berland concludes by saying that P. decipiens seems to be practically the only species occurring in the stomach studied. In a piece ofsmaIl intestine attached to the grey seal stomach studied, Bjorn Berland found five individuals of the acantocephalene Corynosoma strumosum.

Seal tagging

Three trips with a motor boat were made to the Fuglevaer area west of Vega for counting and tagging of seals on the 9th, 10th, and 15th of October. A total of 23 grey seal pups were tagged, most of these newly born white-coated pups. Yellow plastic tags with numbers from D0219 to D0241 were fastened to the swimming skin (membrane) on one of the back flippers on each animal. The tags were marked "Havforskning Bergen Norw". The Institute of Marine Research has used this tag type (Dalton Jumbo Rototags) for tagging of seals in the Artie Ocean for a number of years. Experiences have been good and recaptures of seals tagged up to 8 years earlier have been reported. However, it is still not certain if these tags will remain attached on grey seals that haul up on -Lhe shore where wear and tear can cause them to fall off. It is requested that recaptures and observations of tagged animals or finds of loose tags be reported to the Institute of Marine Research (Post office Box 2906, 5011 1 5.

14. mad on Flatholmene ) the whelping starts [ include when and where a areas further north probably was made, how the r, it must be pointed out that was attached. Further- e their young as early as August the lower jaw of anuary-February. nt in with the report, but in the Vega-area show that parasite so desired. For reports heavy in certain areas that the fish per tag will be paid. :eted. P. decipiens was identified when the lower jaw is ;11 fish and grey seals from Vega. 7e is a connection between the grey rasite infection of fish in this area. Dably spread and increase parallel )tal of 106 grey seal crease of the grey seal population. 7 seals and 10 unidentified and has edited the manuscript, Bjorn lowever, carried out in um have determined the species and it cannot be used eal and fish. Detailed tables of the population of these nematode infection in fish are torate of Fisheries. an estimate of the pup ed by repeated counts from be spread out over ember to the beginning the pupping period Lace. The chief whelping to occur from the end , No pups were observed

assume that pupping, if it takes itil the middle of 16.

(.--EftômersuND ql

1 /: I / ea 1 r I I . I/

1) Flight 8/10 -F light 14/1 ') 5 pups 5) 10 pups fly eller bàt fra 8.— 16. oktober 1975 fra Froan til Vega. Fig. 1. Havertunger observert fra 6) 20 pups 1) Flytur, 8/10, 2) flytur 14/10, 3) 1 unge, 4) 5 unger, 5) 10 unger,_ 6) 20 unger. Fig 1. Grey seal pups observed from airplane or boat October 8-16,1975 betwee9 Froan and Vega. 5

1) Flight 9/10 2) Flight 16/10 3) 1 pup 4) 5 pups 5) 10 pups

Fig. 2. Havertunger observert fra fly eller bAt 8.-16. oktober 1975 fra Vega til Bodo. 1) Flytur 9/10,2) flytur 16/10,3) I unge 4) 5 unger, 5) 10 unger. Fig. 2. Grey seal pups oberved from airplane or boat from October 8-16, 1975, between Vega and Bodo. . • 18.

LITTER A11. R Noi th Atlantic and Ai ctic waters. J. alp!. Fa.!., 12 (2): 437-450. BENJAMINSI.N, T., BLaoi wiry, B., FLASLJ, A., Husi I., og Scorr, D. M., and FISHER, H. D. 1958. 1 m icicnce of the ascarid OP.ITSLAND, T., 1975. Sclundersokelsei i clet nordlige Porrocaecum dcdpiens in the stomachs of three species of Atlanterhav i 1974. Fiskets Gang, 61: 381— 389. seals along the southern Canadian atlantic mainland. BERLAND, B., 1973. Om parasittcr i fisk. FisActs Gang, .59: J. Fish. Res. Bd. Can. 15(4): 495 — 615. 486-493. YouNo, P. C., 1972. The relationship between the presence of Bux, A. S., 1974. Rapport om telling av havert (H. grypus) i larval anisakine nematodes in cod and marine mammals Froanontràdet. Rapport til Institutt for Midisinsk Biblogi, in British home waters. J. appl. Ecol. 9 (2): 459-485, Universizetet i Tromso, 1. nov. 1974: 1 -2, 2 kart. 2 pls. MANSFIELD, A. W., 1966. The grey seal in Eastern Canadian OYNES, P., 1964. Sel pà norskekysten fra Finnmark tu l More. waters. Can. Audubon, 28 (4): 161-166. Fiskets Gang, 50: 694-707e PLATT, N. E., 1975. Infestation of cod (Gadus morhua L.) with larvae of codworm (Terranova decipiens Krabbe) and herringworm, Anisakis sp. (Nematoda Ascaridata), -in

Benjaminsen, T; Bergflodt, B, Froland, A., Huse, I and Orrilsland,T, 1975. Seal investigations in the NortharnAtlantic in 1974. Fiskets Gang, 61: 581-589.

Berland, B., 1973. On parasites in fish. Fiskets Gang. 22: 486-493.

Blix, A.S. 1974. Report on counting of grey seals (H. ry-pus) in the Froan area. Report to the Institute for Medical Biology, The University of Troms6, Nov 1, 1974: 1-2, 2 maps

Oynes, P. 1964. Seals on the Norwegian coast from Finnmark to Itire. Fiskets Gang, 50: 694-707. p. 6 19.

"The investigations showed, however, that counting from airplanes was a practical method for determining the pup production of grey seals" 20.

Grey Seal Investigations on the Norwegian Coast from Lofoten to Fré)va. September-November 1976. by Terje Benjaminsen, Bjorn Bergflodt and Ingvar Huse, Institute of Marine Research, Directorate of Fisheries; Paul Brodie, Bedford Institute of Oceanography, Dartmouth,N.S., and Kjell Toklum, Zoological Laboratory, University in Bergen.

Introduction

Local fishermen's organizations from More to Sor- Helgeland have in recent years pointed out that grey seals

and harbour seals haveLincreasingly\createdlgreater_ difficulties for the coastal fishery. It is claimed that the seal population in some areas has increased sharply and that this has led to damage to fishing gear, increase in parasite infection in fish and heavy exploitation of fisheries resources. The production of grey seal pups on the coast from Froya to Lofoten was estimated to be 570 early in the 1960's. In the summer of 1974 the Institute of Marine Research started investigations of the parasite infection and counting of grey seals at Vega (Benjaminsen et. al 1975). The size of the grey seal population was not successfully determined, but it was confirmed that parasite infection in fish in some areas was high. New investigations were carried out at Vega in July 1975 and from Froan to Bodei in October 1975 (Benjaminsen et. al 1976). The studies at Vega showed that parasite infection in

cod in certain areas is so high that it is difficult to market 21. the fish. The parasitic roundworm P. decipiens ("kveis" "cyst"), that can be found as larvae in the fish muscle and as sexually mature nematodes in the stomach of seal, was found in large numbers in both fish and grey seal from Vega. Counting of grey seal pups from an airplane was carried out between October 8 and 16, 1975. A total of 106 grey seal pups were observed from Froan to BodO, but the counts were carried out in such a short period that the results could not be used as a basis for estimating the total pup production of grey seals. Funds for a more comprehensive seal count from Froya to Lofoten were made available from the Fishing Industry Research Fund in the fall of 1976. In addition to the aerial survey, as many grey seals as possible lyre to be shot in the area west of Vega. Onepurpose was to study if a local reduction of the population could lead to a decline in the parasite infection in fish and to lower damage to fishing gear. From the animals killed, samples were to be collected for studies on age, reproduction, stomach contents and parasites.

In this report, the aerial survey is described, together

with other studies carried out in the fall of 1976 by the Institute of Marine Research with assistance from the Fisheries and Marine Service, Ministry of the Environment, Canada, and the Zoological Laboratory, University in Bergen.

Seal Counting from Lofoten to Fraya

• Grey seal pups are born with a long-haired white pelt on the outermost islets along the coast, chiefly 22. from More to Lofoten. The pups lose the white pelt in 2-3 weeks and then have a short-haired grey pelt. The white coats lie on the shore all the time, but can carry out short swims in the ponds ashore. The time for whelping on the Norwegian coast varies from area to area ana occurs chiefly from the end of September to November, but some pups can be burn as early as August and others as late as January- February. In the period September 28 to November 10, 1976, a total of 7 surveys were carried out from the air. The flights were carried out with a Cessna belonging to Norving; pilot was Bjorn Jaeger. A total of 29 hours were flown. In the area to the west of Vega, counting from the air was carried out six times. Other known or possible pupping areas for grey seals in the area from Lofotodden to Fraya were investigated from 1 to 5 times. The areas that were covered and the number of pups observed are shown in figures land 2. The observations in the various areas (island groups and villages) are summarized in Table 1 together with an estimated minimum production in each area. The molting stage of the pups was registered on most of the counts, and this gives a basis for the minimum estimates of pup production in Table 1. To the number of pups observed in an area during the first countY the number of whitecoats seen during the next count ) if the counts are carried out three weeks or more apart. It is then assumed that the pups have shed the white coat before they are 3 weeks old and that the whitecoats seen during the second count wanaborn after P.9 2 3.

the first count was carried out. In the area near Mosken south of Lofotodden, a total of 21 pups were observed. Of these, five were seen on the west side of Mosken itself. The counts were carried out here on October 18 and November 10. According to bynes (1964) there has been a grey seal colony off Lofotodden which consists of at least 6 pairs. The counts show that pupping occurs in this area from the first part of October until well into November. In the area near Ràst, a total of 6 pups were observed on October 18. 8ynes (1964) writes that only 2 grey seal pairs with pups have been seen here. In the skerries group Grànna in Melày, the aerial survey was carried out on November 10. A total of 6 pups were seen here, all with white pelts. At a similar count on October 16, 1975, no pups were observed here. This indicates that pupping in this area does not start until the beginning of November. According to àynes (1964) this colony should consist of at least 15 pain. Further south, east of Myken, there is a number of small islands called Valvaer. On October 18 we observed 17 pups here; 8 days later a new count was made from the air and only 5 pups were seen. This was a day with unusually

fine weather) and it must be assumed that this was the reason for so many pups having left the islands: On November 10, no grey seal pups were observed here. dynes (1964) writes that 5-6 pairs whelp in this islet group and that 15 white- coats were seen here in 1952. On October 16, 1975, Benjaminsen 24. et. al (1976) counted 12 whitecoats from the air in Valvaer. The observations indicate that the pupping starts in the first part of October. The whelping areas in Traena were investigated on the 18th and 26th of October and on November 10. Only one whitecoat was observed. Oynes (1964) indicated that 15 pairs should be whelping in this area. During the aerial counting in 1975 only one pup was also observed. On Floholmene off Skibbatsvaer in Donna, a total of four aerial surveys were carried out from October 11 to November 10. The largest number was observed on October 18 when we saw 34 pups. However, it is probable that some pups have been missed on this flight since light conditions were poor. On October 25 we were at Floholmene wi th a boat and landed on the islands where most of the pups had been observed. A total of 24 pups were tagged of which half had shed their white pelts. Only one of the pups was newborn. The counts showed that the pups in this area were born from the beginning of October until well into November; most of them in the first half of October. The outermost islands southwards to Vega were investigated, but no grey seal pups were seen. The emphasis of the p. 13 investigation was placed on the area to the west of Vega. Counting was carried out here 7 times from September 28 to November 10. Table 1 shows that the number of grey seal pups increased up to October 20-22 when a kill was carried out on most of the islands. On October 25 and November 10 only one pup was spotted on the islands where the kill was

Tabell I. thdersulde ornrelder o ob.terverte' wzger ay. haver 25. tend fia fl) og Iii lots fra Lefotc.n Iii Fia, septtniber — nouenzber 1976. S = Svartunger, uzsger sum 1°1: eller delvis har felt den hrite ungepelsen. P =.Afinirmanspoduksjon beregnet pci grunnlag av ungene aldenfordeling. [Surveyed areas and the number of grey seal pups counted from the air and on foot on the coast fronz Fraya to Lofoten in Septenzber — November 1976. S = Beaters, pups which are moulting-or have moulted their foetal haircover, P = Minimum production estinzated from the age distribution of pups.] Antall No. pups Ontràde [Area] Dato unger [Date) Totalt -. [Total] S P

Tennholmen 10/11 0 — — Mosken 18/10 13 0 « 10/11 12 7 21 Rost 18/10 6 0 6 Gronna 10/11 6 _0 6 Valvzr 18/10 17 0 . « 26/10 5 0 « 10/11 0 — 17 Myken 26/10 0 — Tr-mna 18/10 1 0 • « 26/10 0 • — « 10/11 0 — 1 Floholmene 11/10 29 0 « 18/10 34 0 « 25/10 24 13 « 26/10 14 0 « • 10/11 4 1 AZ Lyngvter 11/10 0 — « 26/10 • 0 — Ytre Flesan 26/10 0 — Flovrs 26/10 0 — « 1 10/11 0 — Skjarvxr 25/10 0 — « 1 26/10 0 — « a 10/11 0 — Vest av Vegas 28/9 2 0 « 1 11/10 10 1 « 1 19/10 42 0 « 1 20-22/10 41 0 « 1 25/10 9 2 « 1 26/10 11 0 « 10/11 12 11 67 °niacin 28/9 0 — « 19/10 0 — « 26/10 1 0 1 Vikna 28/9 0 — « 19/10 1 0 I ['alien —Froans 28/9 28 1 «1 19/10 94 — 94 Mdsteinen 28/9 0 — .« 19/10 19 0 19 Sulen1 28/9 0 — Stun 270 1 De fleste kastelokaliteter dekket. [Most of the breeding localities covered by the survey.] 8 Bare en liten del av kastelokalitetene dekket. [Only a few breeding localities covered.] Tabell 2. Antall, art, utviklings,stadier og kjonnsfordeling av rundorm i magen av haver fanget vest av Vega 20.-22. oktober 1976. Art, utviklingsstadium og kjonn ble bestemt for 30 rundormfra hver sel. [The number, species, stage of development and sex composition of nematodes from stomachs of grey seals samples west of Vega 20.-22. October 1976. Species, stage of development and sex were determined for 30 nenuztodes from each seal]. • Havert (grey arid) Antall P. decipiens Anisakis Contracaecum rundorm Larve Kjonnsmoden Larve Kjonnsmoden Larve Kjonnsmoden Kjonn Alder No. of (immature) (mature) (immature) (mature) (immature) (mature) (Sex) (Age) nemat 3. stad. 4. stad. Hann I * Hunn 3. tad. I.. stad. Hann I Hunn 3. stad. 1 4. stad. Hann I litinn

Hun 10 996' 0 7 13 10 0 0 0 0 0 0 o 0 Han 10 1633 0 9 II li) 0 0 0 0 0 0 0 0 « 3 302 3 4 4 13 1 4 0 0 0 1 0 0 Hun 17 5591 9 3 4 9 5 0 0 0 Q 0 ' 0 0 « 10 1665 0 7 12 11 0 0 0 0 ' 0 0 0 0 « 10 1932 0 12 7 11 0 0 0 0 0 0 0 0 « 9.4037 0 17 6 7 0 0 0 0 0 0 0 0 « 14 2351 0 20 3 7 0 0 0 0 0 0 0 0 « 8 2071 0 17 6 7 0 0 0 .0 0 0 0 0 « 6 2033 1 2 11 16 0 0 0 0 0 0 0 0 « 6 732 0 10 5 6 0 4 1 3 0 0 0 1 Hann 6 718 1 5 11 13 0 0 0 0 0 0 0 0 ràder er markert med strek 1) 1 unge, Fig. I. Havertunger observert ira Froan tu l Vega. De undersekte oin. covered h indi- 2) 5 unger, 3) 10 unger, 4) 20 unger. [Grey seal pups observed from Froan to Vega. Arca cated by line. I) 1 pup, 2) 5 pups, 3) 10 pups, 4) 20 pups.] 28. 1 2

v. RÔY

1 6

• • • #

d t • • l

4* :

J. o

TR/ZNA .•4, 1 e

I '

('-' 1‘ .4â

i. n Iç te4 4. ' • 1 •• • •• • 2 3

7. 4, YEGA 4

. ...... ».‘„. • .2) '1 O %6BRÔNNpYSUND

I 7,6; . "?`•••‘...... • •

Fig. 2. Havertunger observert fra Vega til Lofotodden. De undersokte omràder er markert med strek 1) 1 unge, 2) 5 unger, 3) 10 unger, 4) 20 unger. [Grey seal pups observed from Vega to Lofotodden. Area covered à indicatcd by line. 1) 1 pup, 2) 5 pups, 3) 10 pups, 4) 20 pups.] 29. conducted. This indicates that whelping had practically ended in this area on October 20 and that most of the pups were born between the 10th and 20th of October. In 1975 it was found through counting from the air and from a boat that whelping started around October 10 (Benjaminsen, et. al 1976). Our counts in 1976 showed that at least 67 grey seal pups were born in the area to the west of Vega. Oynes (1964) assumed that about 50 pairs pupped in that area in the beginning of the 1960 1 s. On the small islands where whitecoats were seen in 1975, pups were found also in 1976. Pups were seen on a total of 18 small islands there. Grytholmene, Alflesa and Gasflesene seem to be the most important. Some of the most important whelping areas on the coast between Vega and Vikna were investigated on the 19th and 26th of October. Only one whitecoat was observed in the whole of this area. In the aerial survey October 8th and 14th, 1975, no pups were seen here. Oynes (1964) indicated that 20 pairs whelped at Sklinna. The Vikna area was investigated on October 19, but only one pup was seen. According to bynes (1964), a total of 100 grey seal pups were born annually in the Vikna area and that the number had been increasing. Since thenkimehas probably not been any hunt of importance on grey seals, and it should therefore be expected that the population has increased further. It is therefore reasonable to believe that whelping does not start in this area before the end of October. 30 •

On September 28 we investigated the most important whelping areas in the Halten-Froan area. A total of 28 pups were seen. On October 19 the area was covered more completely and a total of 94 pups observed. All the islands could not be covered since we were running short of fuel. Finnvaer and a few other islands whereelelping was probably occurring had to be left out. Some of the pups were observed swimming in the sea and many May therefore have been missed. The investigations showed that a considerable number of the pups were born as early as in the last half of September, but the whelping period seems to vary from island to island. On Helvete and Brattflesa, furthest to the north, we saw 20 pups on September 28, compared with 31 pups observed on October 19. Further south and west, on Vona, Ormskjaer, Gromnskjaer and Klokkerne, we saw a total of 7 pups on September 28. On October 19 the number had increased to 41. dynes (1964) estimated the number of whelping grey seal females at Halten-Froan to be 300. Frengen and Roy (1976), who carried out a count of grey seal pups in the northern part of the Fro Islands on October 11-12, 1974, found 97 pups that varied in age from newborn to about 4-week old animals. They assumed that the counting was carried out in the middle of the whelping period and estimated that at least 300 pups were born on Fro Islands. All the islands in the Halten- Froan area were investigated from helicopter on October 28, 1974 (B1ix 1974). He found 21 grey seal pups and estimated the average age to be 3 weeks. In a corresponding survey on October 20, 1975, a total of 35 grey seal pups were seen. 31.

Most of them had then shed the white coat (Blix, personal communication). In an aerial survey in 1975, a total of 46 pups were observed on Halten-Froan (Benjaminsen, et a1 1976). However, the area was not completely covered since the plane had to return due to a shortage of fuel. Pups were seen on the same island in 1976 as in 1975 3 with few exceptions. On Melsteinen, a group of islands to the east of the Fro Islands, a total of 19 whitecoat pups were seen on October 19. On the first flight on September 28 no pups were seen here. It must therefore be assumed that whelping did not start here until sometime in October. Blix (personal communication) saw 15 pups on this island group on October 20 in 1975. The area to the southwest from the Fro Islands to Sulen to the north of Froya was investigated on September 28. However, no grey seal pups were observed in this area. In order to be able to determine the grey seal pup production in the various areas, the whelping periods must be known. This means that one must know when the largest number of whitecoats is present and the relationship letween this number and the total pup production. Anderson and Curry (1976) studied the whelping period for two islands on the Hebrides only 1 km apart. They showed that the average date for pupping was October 9 on one island and October 17 on the other and that the duration of the whelping period was different on the two islands. The relationship between the maximum number of pups present at any one time and the total number of pups 32.

born was 1:1.2 on one island and 1:1.6 on the other. This shows that one cannot arbitrarily transfer a ratio from one whelping area to another. The duration of the whelping period also varies in some areas studied on the Norwegian coast. At Vega most of the pups are born in a 10-day period while the pupping extends over a month on Halten-Froan. It is therefore necessary to combine the aerial surveys with control counts ashore in order to determine the distribution of the ages of the pups. The accuracy of the aerial counts in 1975 was checked by going ashore on some of the islands (Benjaminsen et. al, 1976). It was verified that the aerial surveys gave quite accurate results. The investigations in 1976 conirmed that. On 7 small islands to the west of Vega, a total of 40 pups were counted from the air on October lg.

We went ashore on the same islands on October 20 - 22 and counted 41 pups. On some of these islands,the number found was higher than by aerial counting, on others it was lower , the largest deviation being 4 pups. The difference can partly be explained by the fact that some pups were born between the two counts.

Sampling of Grey Seals

To the west of Vega, a total of 26 adult seals and 44 PuP s were killed in the period October 20-22. In addition, three live pups were captured for the University of Oslo. Since most of the adult animais had to be shot in the water, more than half were lost. However, we were able to collect 33. samples from 12 adults, 10 females and 2 males. From each of the animals, a collection was made of the lower jaw for age determination, sexual organs for determination of sexual maturity, and stomachs for studies of food ànd parasite (nematode) infection.

Parasite Studies

Of the four types of nematode (roundworm) larvae or "kveis" in fish, Phocanema decipiens is the only one that prefers the muscle of the fish (Berland, 1973). The other types can be found on organs in the stomach cavity (Contracaecum and Phocascaris) and in the stomach cavity or on the liver (Anisakis) where they are quite visible. Since it is P. decipiens that first and foremost creates problems for fish marketing, the life cycle of this species will be briefly described. In the North Atlantic the sexually mature P. decipiens can usually be found in the stomachs of a number of seal species, more seldom in whales (Scott and Fisher, 1958; Rae, 1963; Young, 1972). Both in Canadian and British waters, it is the grey seal that has the largest number of P. decipiens. Each of the sexually mature P. decipiens produce approximately 1500 eggs. These eggs are carried into the sea with the seal excrements ) where they hatch and can be eaten by an invertebrate animal, probably a crustacean that lives on the bottom. The larva then remains in the crustacean until it is eaten by a fish. From the fish intestine the larva moves into the stomach cavity or the muscle where 34. it remains until eaten by a seal. The larva then becomes a sexually mature nematode in the seal stomach j and the cycle is closed. P. decipiens can be found in bottom fish like cod, cusk, and ling, probably because the crustacean which is the second stage in the cycle liveson the bottom. Benjaminsen et al. (1976) showed that cod caught in shallow water was more heavily infected by nematodes than fish in deeper water, and that inshore cod ( coastal cod) seem to have many P. decipiens. According to Mansfield (1966), Young (1972) and Platt (1975), the size of the seal population is the most important factor that determines the number of P. decipiens in fish. Studies in the Vega area in 1974 and 1975 confirmed this (Benjaminsen et. al 1976). Table 2 shows species and stage5of development and the total number of nematodes in grey seals shot west of Vega in October 1976. Species and stagasof development are determined on the basis of 30 nematodes from each seal stomach. The table shows that P. deciriens dominate in numbers, of a total of 360 individuals studied, 340 were of this species. Only 18 Anisakis and 2 Contracaecum were found in the sample nematodes. This is very different from the species distribution of nematodes in grey seals in Great Britain (Young, 1972). The domineering species in the British material was Contracaecum ) and up to 30,000 individuals were found in one seal stomach. The largest 35. number of P. decipiens was found in a grey seal from the Orkney Islands where this nematode occurred with an average of 735 individuals per seal. The maximum number of P. decipiens in one grey seal stomach from the Orkney Islands was 1853. The largest number of nematodes in our material of grey seals from Vega was 5591 which was found in a 17-year old female. The smallest number was 302 in a 3-year old male. The average number was 2005. There was an increasing number of nematodes with increasing age (correlation coefficient r = 0.75). Remnants of food were found in the stomachs of 4 seals. In two of the animals, remnants of whelks (Buccinum undatum) were found; in three remnants of fish and crabs (Hyas sp).

The. crab Carcinus maenas was found in two animals. Studies on nematodes were carried out in fish caught in two areas. North of Sola in position N65°11' Ell ° 41', a total of six cod were caught at 20 metres'depth on October 25. The fish were from 2 to 3 years old with Carcinus maenas and hermit crabs in the stomachs. Only 2 fish had nematodes, one in each. On October 28 a total of 44 cod and 1 haddock were caught at 15-60 metres depth south of Sola in position N65° 39 1 , Ell° 42'. The stomach content was herring and small pollock. Nematodes were found in 36 fish ) and the number of nematodes in the flesh varied from 0 to 38, on the average 6.6 larvae per fish. a This is lower than in a fish sample taken at Lanan north of Vega in 1975. BeWaminsen et al.(1976) found 36. that the cod here had an average of 15 nematodes in the flesh and that the largest number was 70 nematodes in a fish. Platt (1974) studied the nematode infection in cod caught by British trawlers in various areas of the North Atlantic. He found that the number of P. decipiens was greatest off the northwest coast of Iceland with an average of 8.4 larvae per cod. The average number for P. decipiens in cod taken off the coast of NortheriNorway and in the Barents Sea was only 0.2 larvae per fish. In the fish sample taken to the south of Sola the number of nematodes in the fish flesh increased with increasing age of the fish (r = 0.41). Species determination of 32 nematode larvae from cod and 2 from cusk showed that all were P. decipiens.

Mortality and Age of Sexual Maturity

The grey seal population has shown a sharp increase in both Canada and Great Britain in the past 25 years. hl the whelping areas in Great Britain I the density of animals is so great that this leads to a very high pup mortality. On Farne Islands it is usually more than 20% (Bonner and Hickling, 1974). This pup mortality is usually due to the fact that the females cannot find their pups again,and that these therefore starve to death. During the investigations in the Vega area in 1975 and 1976, and on Floholmene in 1976, we have seen a total of 94 pups close up, but we have not observed any undernourished or dead pups. This indicates

that the pup mortality in these areas is very small, in any 37. case during the first three weeks after whelping. Fishermen in the area say that they get some grey seals, especially young ones, in fishing nets or traps, but we do not know how many lose their lives in this way. The killer whale can be another important mortality factor for the grey seal population. 8ynes (1974) observed a pod of up to 300 killer whales off the Helgeland coast in 1974, and we observed 15 killer whales only 15 nautical miles to the north of the whelping area at Halten in October 1976. Greenland sharks can also possibly take some grey seal pups. At fertilization i a hormone-producing structure is formed in the ovaries (-Le yellow body, Corpus luteum), which plays an important role in regulating the pregnancy and the size of the fetus. After birth, this body is reduced to a scar and decreases in size until it finally disappears. In some animals this occurs in about a year, in others the scar from bodies formed 5 years ago or earlier can still be seen. Grey seal females usually have one pup each year and for each pregnancy only one yellow body is formed. The scars can usually be recognized for a couple of years or more, and by studying the ovaries from relatively young animals one can get an idea of how old the seal was the first time it whelped. In our material it was shown that two females had their first pup already as 4-year olds. A 10- year old animal and a 9-year old had both had their first pup at the latest as 5-year olds. This show that a considerable part of the grey seal females.in the Vega area have their first pup as 4-5 year olds. In the material from Vega ) the average 38.

age was 10 years for the 10 females that had pupped. On Sable Island off the east coast of Canada, most grey seal females have their first pup when they are 5 years old. However, on Farme Island, it appears as if the females mature later, and it is probable that the females do not have their first pup before they are 10 years old (Platt et al.1975).

Pup mortality, and age at sexual maturity therefore seem to be lower for grey seals off Vega than for instancéYthe grey seal population on Farme Island,which has increased by 9% yearly since the end of the 1950's

(Bonner and Hickling, 1974). If mortality among the older

animals is not very different in the two areas, which is a reasonable

assumption, it can be concludedthat the grey

• seal population off Vega may now increase by more than 10% yearly.

Seal Tagging

On October 25, 1976, we tagged 24 grey seal pups on Floholmene off Skibbatsvaer in Donna. Yellow plastic tags with numbers from D1301 to D1325 were fastened to the tail flippers of each animal. The tags had the text "Havforskning Bergen Norw". One of these animals was taken in a gillnet on January 10, 1977, 2- months after the tagging, at Myken, which is about 40 nautical miles north of the tagging location. In October 1975,a total of 23 grey seal pups were tagged to the west of Vega. One of these was caught in April 1976, six months after the tagging, in Flovaer which is 15 nautical . 39.

miles to the north of Vega. We request that recaptures, observations of tagged animals or finds of loose tags be reported to the Institute

of Marine Research (P.O. Box 2906, 5011 Bergen-Nordnes). Include information on when and where the recapture, observation or find was made, how the animal was captured and how the tag was fastened. We are furthermore interested in the lower jaw of tagged seals. The tag should be sent in with the notice, but it will be returned to the finder if

so desired. For information on recaptures, a fee of 30

kroner per tag is paid. This is increased to 50 kroner when the lower jaw is included with the information.

SUMMAR.Y AND CONCLUSIONS Grey seal pups (Halichocrus su pus) were counted from the air along the Norwegian coast from Froya (about 64° North) to Lofoten (about 68cNorth) dming the period from 28 September to 10 November 1976. Fairly complete estimates of pup production were obtained for some of the more important breeding locations. A minimum of 70 pups were born west of Vega Island. This corresponds to a stock in this region of more than 300 seals. On Floholmene off Skibbâtsvier which were surveyed four, times, production was estimated at a minimum of 40 pups, corresponding to a stock in excess of 150 seals. At both of these loc- ations the aerial surveys were checked by direct counts on foot. At the other breeding locations the time sequences of the aerial surveys are incomplete, and only rough minimum estimates of production can therefore be given for these locations. It became clear, however,

40 • • 17

• at hic age f. !!:, Nvi”.1t.F. r.-.) and CicilAnd !1.11r1 (So7;,:;ititus _by din. et C(11] OF. I lion.

Halten -Froan apinar, luc the most productiv- Analysis of ovari( J indicate that many females pro- breeding area for grey suuh, on the coast of Norway. duce their first pup at ages 4-5 years. Both pup mort- In this region a total of 94 pups v.-ere counted from ality and age at reproductive maturity is lower at the air, but coverage was incomplete. Other im- Vega than in the United Kingdom. portant breeding locations may be the Mosken group In order to obtain better estimates of pup product- of islands where 21 pups were counted from the air, ion and stock size at other locations than the Vega and Valvxr (east of Myken) where 18 pups were area and Floholmene, it will be necessary at each recorded. location to make at least four,aerial surveys and to A total of 270 pups were recorded, corresponding check the age-composition of pups by counts on foot to a total stock of about 1100 seals in the whole area at least once during the local breeding season. covered by the surveys. However, this is a minimum and the total stock of grey seals in the area probably L1TTERATUR exceeds 3000. Anderson, S. S., and Curry, M. C. 1976. Grey seals at the In the early 1960-ies it was found that about 600 Moriach Isics , Outer Hebrides, 1975. Coun. Mea. int. grey seal pups were produced annually from Froya to Coun. Explor. Sea, 1976 (N :9) 1-6. Lofoten. This would correspond to a total stock of Benjaminsen, T., Bergflodt, B., Froland, A., Huse, I., og Orits- about 2500 seals. In area.s which were well covered land, I. 1975. Selundersokelser i det nordlige Atlanter- by this survey, we found significantly higher numbers hav i 1974. Fiskets Gang, 61: 381-389. - Bergflodt, B. og Huse, I., 1976. Telling av haven pà of pups than suggestcd for the 1960-ies. Norskekysten fra Halten-Froan tu l Bodo og under- The timing of the breeding season varies between sokelse av kveisinfeksjonen i fisk ved Vega. Fonde: for locations within the area covered by the surveys. At fiskeleiting og forsek. «Rapporter» Nr. 1-2, 1976: 17-22. Mosken, Valvac-, Vega, Floholmene and Halten most Berland, B., 1973. Om parasitter fisk. Fiskets Gang, 59: 486/493. of the pups are born during the first half of October. Blix, A. S., 1974. Rapport om telling av havert (H. grypus) i Froanomràdet. Rapport til hutilutt for Aledisinsk Biologi, At Gronna and Vilnia, huwever, puping does not Universitetel i Tromso, 1. nov. 1974:1-2, 2 kart. begin until early November. Bonner, W. N., and Hickling, G. 1974. The grey seals of the 'West of Vega 26 adult g-rey seals and 44 pups were Farne Island 1971 to 1973. Trans. nat. Hist. Soc. shot and 3 pups were collected for physioldgical Northumb., 42 (2) 65-84, pls. 4-6. studies. Lower jaws, stomachs and reproductive Frengen, O. og Rev. N., 1976. Havert i Halten-omràdet. Uni- Universitetet i Trondheim, DK1i6M Rapport. Zoologisk organs were sampled from 10 adult females and 2 Scric 1975-7. males. Mansfield, A. W., 1966. The grey seal in Eastern Canadian The stomachs of 12 dissected grey seals sampled waters. Can. Audubon, 28 (4) :161 - 166. west of Vega, contained an average of 2005 nema- Platt, N. E., 1975. Infestation of cod (Codas morhua L.) with todes each. Subsamples . which were identified, show larvae of codworm (Terranova decipiens Krabbe) and herringworm, Anisakis sp. (Nematoda Ascaridata), in that 94.5% were Phocanenla decipiens, 5.0% were North Atlantic and Arctic waters. J. appl. Ecol., Anisakis sp. and 0.5% were Contracaecum sp. 12(2):137 -450. An average of 6.6 nematodes was found in the Platt, N. E., Prime, J. H., and M'itthames, S. R. 1975. The age muscle-tissue of 44 cod (Gadus morhua) and one had- of the grey seal at the Farne Islands. Trans. nat. Hist. dock (Gadus aeglefinus) caught - in the area west of Soc. Northumb., 41(4): 99-106. Rae, Bennet B. 1963. The incidence of Porrocateum decipiens in Vega. These nematodes were all P. decipiens. The the flesh of cod. Department of Agriculture and Fisheries number of P. decipiens increased with increasing age for Scotland. illarine Research No, 2 1963 (2): of both the seals and the fish. The grey seals at Vega Scott, D.m., and Fisher, H. D., 1958. Incidence of the ascarid are far more heavily infested veith P. decipiens than Porrocaecum decipiens in the stomachs of three species of grey seals investigated in the United Kingdom, and teals along the southern Canadian Atlantic mainland. .y. Fish. Res. Bd Can. 15 (4) : 495 - 6 I 5. the present studies confirn-i that nematode infestation Young, P. C., 1972. The relationship between the presence of is a serious problem for local fisheries in the Vega larval anisakine nematodes in cod and marine mammals district. itt British home waters. J. Appl. Eco!., 9(2) :459-485, Natural mortality of pups during the first few week.s 2 pls. alter birth appears to be very low. None of the 94 Oynes, P., 1964. Sel pà norskekysten fra Finnmark til More. Fiskets Gang, 50: 694 - 707. pups which were closely observed at Vega and Flo- - 1974. Observasjoner og merking av brugde og hval i holmene were starving or dead. Mortality is affected Norskehavet i mai og juni 1974. Fiskerirucringeru Forseks- by fishing gear and may also be caused by killer fond, Rapporter 1974(4): 43 - 46. Benjaminsen et. al. 1975. Seal investigations in the Northern Atlantic in 1974. Fiskets Gang, 61: 381-389.

Benjaminsen, T., Bergflodt, B and Huse, I. 1976. Counting of grey seals on the Norwegian coast from Halten-Froan to Bodo and studies of nematode infection in fish at Vega. Fund for Fish Searching and Experiments. "Reports" No. 1-2, 1976: 17-22.

Berland, B. 1973. On parasites in fish. Fiskets Gang. 59:486- 493.

Blix, A.S. 1974. Report on counting of grey seals(H. grypus) in the Froan area. Report to Institute for Medical Biology, University in Tromso, Nov. 1, 1974: 1-2, 2 maps.

Frengen, O. and Roy, N. 1976. Grey seals in the Halten area. University in Trondheim, DKNSM Report, Zoological Series, 1975- 7.

8ynes, P. 1964. Seals on the Norwegian Coast from Finnmark to Mare. Fiskets Gang, 50: 694-707.

- 1974. Observations and tagging of basking shark and whale in the Norwegian Sea in May and June 1974. Fishing Industry Research Fund, Reports 1974(4): 43-46. 42.

"Ungene var da ett i sjoen og det ble bare sett 1 unge og 6 voksne"

"The pups had then gone in the water and only one pup and 6 adults were seen" 43.

19 UNDERSOKM STI:r;);()BEE 00 11VERT PA NORSKEKYSTEN TII,f-:'..,R11.1:1.GELAND. I V.:77 [Harbotn 3(al and gru 5Lal inzsti,-..ctini on du- .h.'i.ru.rgian coast from A'oidar)e to Sorhcl,gcland in 1977]

A v/B y Terjc Benjaminscn, Bjorn Bergflodt og Torger Oritsland Fiskeriditektoratets Havforskningsinstitutt, Bergen Arne Bjorge, Morten Broandal, Arvid Paasche og Knut Siverisen, Universitetet i Oslo • Paul Brodie, Bedford Inttitute of Oceanography, Dartmouth N. S., Canada K jell Toklunz, Universitekt i Bergen

ABSTRACT Harbour seals were counted along the Norwegian coast from Vikna (about 65° North) to Vega (about 66° North) during the period from 18 June to 7 July 1977. The population of harbour seals in the southern part of the Vikna area was esti- mated at 100-200 seals. In the southern part of Nordland county only 30 harbour seals v,,ert observed. From 21 September to 9 October 123 grey sea/ pups were counted in the Halten—, Froan area (about 64° North). West of Vega 36 grey seal pups were observed from 17 to 23 October. In 1976 57 pups were counted in the same arca .The decrease may be explained by the kill of 20 mature female seals during the breeding season of 1976. Because of continous bad weather the planned aerial surveys of grey seals pups WCIt. not carried out. • West of Vega one adult grey seal bull, 17 adult females and 36 pups ‘vere shot. This continue the experiment startet in 1976 when as many grey seals as possible were shot in ibis area to investigate whether a local reduction of the stock would in- fluence levels of cod-worm infestation of fish-and the amount of damage to fisheries. Lower jaws, stomachs and reproductive organs were collected from 25 grey seals and 12 harbour scal in the Halten—Froan area, at Vikna and west of Vega. The stomachs of 6 dissected grey seals sampled at Vega contained an average of 1095 nematodes each. Identified sub- samples show that 930Jo of the nematodes were Phocanema decipicns were Anisakis and 1°/o Contracarcum osculatum. An average of 1180 nematodes were found in 17 grey seal stomachs collected in the Halten—Froan area. Subsamples have not yet been identified. The harbour seals Lad substantially lower infestation of nematodes than gl`ey seals. The stomachs of 12 harbour seals contained an average of 52 nematodes (39°/. P.decipiens, 43% Anisokis and 180/e C.osculatum). in the Halten Froan arca 99 grey seal pups were tagged. Tag returns show that the pups are able to swim 4 nautical miles in open Nvater before they are 3 weeks old. Return of 3 tags after 6 to 8 weeks were repported south of Halten, two of them as far as 70 nautical miles away. Analyses of ovaries indicate that many grey seal females produce their first pup at ages 4-5 years. 44.

Introduction

The Institute of Marine Research started investigations of nematode infection in fish and the size of the grey seal population at Vega in the summer of 1974 (Benjaminsen et. al. 1975). The studies showed that the nematode infection p. in fish was high in the areas where there were grey seals and that the infection was greater in shallower water than in deeper water. In 1975, in addition to further studies of nematode infection in fish and collection of biological material of grey seals, counting of grey seal pups from Froan to Bodo was carried out (Benjaminsen et.al . 1976). In the fall of 1976 more comprehensive seal counting was carried out from Froya to Lofoten (Benjaminsen et al. 1977). On the basis of these counts it was estimated that the total population of grey seals on the coast between FrOya and Lofoten was greater than 3000 one-year or older animals. The investigations in 1976 showed that the parasitic nematode Phocanema decipiens ("kveis"; "cysts") which are found as larvae in the fish muscle and as sexually mature in the stomachs of seal, were found in large numbers in both fish and grey seals in the Vega area. To the west of Vega,a total of 26 adult grey seals and 44 pups were killed in 1976. The purpose of this was to see if a local reduction of the population could lead to a decline in the nematode infection in fish and less damage to fishing gear. Funds for continued studies in 1977 were obtained 46.

-e•

Tabell 1. Ante op (i , t rundom i magin av steinl.obbe og havert fanget Afelle,rn Vikna 21. tit 29. juni pe Fro- oyene 21. 3(ptemlni til 'bet ve3t av Vega 17. til 23. cd.tober. Art bic bestemt .for inr:til 3.7 rundorm fra hp:7 sel. [The number end speLirs of nematJdes funz stornac.hs of hwbour and grey seals caught at Alellom Vikna 21-20 June, on Frooyene 21 Stptember to 9 October and West of Vega 17-23 October. Species were determined for up to 30 nematodes from each seal]. Antall Art [Species] OrnrAde Kjonn - Alder rundorm P. decipiens Anisakis C.osculatum [Areas] [Sex] [Age] [No.of nem] Stein kobbe [Harbour seal] * Vikna Hann ti 5+ 100 0 27 3 — * « « 5+ 9 .8 0 1 - * « « 5+ 320 8 20 2 * « — « 5+ 5 0 4 I — * (C • « 5+ 60 24 () 6 — * « HunnF 5r 2 1 0 I — * « « 8+ 9 3 0 6 — * « « 8+ 5 3 0 2 — * « « 5+ 0 0 0 0 — * « et 5+ 0 0 0 0 lavert [Grey seal* « Hann 4 — 6 480 16 6 8 — • « Hunn 2-3 250 22 4 /I — * Frooyene Hann 1 450 — « « 3 450 — « « 19 960 « « 16 50 — « « 16 1 710 — « « 1 800 — « « 4 1 000 % . — « « 19 560 - 4( Hunn 17 1 460 — « « 12 1290 — « « 13 2 550 — « ' « 16 770 . — ' « ee 10 530 — « « 17 1 730 — « « 30 620 — « « 24 2 970 —, « « 16 2 130 'Steinkobbe « Hann 1 45 — « Hunn 4 70 Flavert Vega « 8 190 29 1 0 — « « 11 1 530 29 1 0 — « « 6 1 130 23 5 2 — et « 9 200 30 0 0 — et « 15 2 400 28 2 0 ' 14 1 120 29 1 0

0 ForeleDiee aldersbestemmelser Dà arunnlae av lenede cher antall arr i eeestokkene. FPreliminarv ape determinations on thr ba3is tit length or number of Corpora albicantia). L 5, from The Fishing Industry Research Fund and the Norwegian Fisheries Research Council. The aerial survey program was to be continued along the coast from More to Lofoten and the reduction of the grey seal population to the west of Vega would be continued. In addition, samples of seals, bottom animals and fish were ir) be collected and tagging of grey seal pups on Fro Islands carried out. The investigations were also to include counting and sampling harbour seals on Sorhelgeland and Vikna.

Nematode Studies

Three types of roundworm larvae ("kveis") in fish, our waters. Of with marine mammals as hosts) are known in these, Phocanema decipiens is the only one that prefers the muscle of fish and therefore is a problem for fish marketing. The other types, Contracaecum osculatum and Anisakis are found in the stomach cavity. Sexually mature P. decipiens can be found in several seal species in the North Atlantic p. 20 such as grey seal, harbour seal and Greenland (Harp) seal. Of these, grey seals have the most individuals (Young 1972, Mansfield and Beck, 1977). The eggs of P. decipiens go into the sea with the seal excrements, hatch and can then be eaten by an invertebrate animal, probably a crustacean living on the bottom. The larvae remain in the crustacean until this is eaten by a fish. From the fish intestine the larvae migrate into the stomach cavity or muscles to become encapsulated. If the fish is eaten by a seal,the larvae will develop into sexually mature individual in the seal stomach. 47.

Benjaminsen et al. (1977) showed that the number of nematodes in grey seals caught at Vega on the average was as high as 2005. Of these, P. decipiens comprised 94%, Anisakis 5%, and C. osculatum 1%. Table 1 shows the total number and species composition of nematodes in grey seals and harbour seals caught in Sr-Vikna in June 1977, on Fro Islands in September-October 1977 and to the west of Vega in October 1977. The grey seals on Fro Islands had an average cf nematodes in the stomach. Two harbour seals caught in 1180 the same area had respectively 45 and 70. The species composition of these roundworms is still not known since the work is still underway. From the table it can be seen that p. 21 harbour seals shot on Vikna have considerably fewer nematodes than grey seals on Vega and Fro Islands. The average is only 52 worms per seal. The species composition is also

different) with 43% Anisakis , 39% P. decipiens and 18% C. Osculatum. The two young grey seals from Vikna had about the same number of nematodes as grey seals of corresponding age on Fro Islands and Vega, but the percentage of P. decipiens was only 63%. Grey seals on Vega had on the average 1095 nematodes; i.e. only about half the number found the year before in this area. P. decipiens comprised 93%, Anisakis 6%, and C. osculatum 1 %. The results therefore show that grey seals on Fro Islands also have a large number of nematodes in the stomach. It furthermore shows that the harbour seals in the areas studied appear to have little importance for the transfer of P. decipiens to fish. This has also been found in corresponding studies in Canada where grey seals 48. had 8 times as many P. decipiens as harbour seals. (Mansfield and Beck 1977).

Seal Counting

Counting of harbour and grey seals was carried out in the Fuglevaer area to the west of Vega from June 18 to 22. Only five harbour seals and twelve grey seals were obsèrved in the area. The investigations continued June 24-29 in Mellom-Vikna from Ofstad Sea to Nord- Gjaeslinga. The population of harbour seals in this area was estimated to be 100-200 animals. Fourteen grey seals were also seen in this area. Counting was carried out in Flovaer to the north of Vega between July 1 and 3 and 12 harbour seals and 2 grey seals were spotted. From July 4 to 7, the area from Torg Island to Lyngvaer to the south of Bronnàysund was searched. Three harbour seals were seen at Torg Islands and 10 harbour seals in Lyngvaer. The surveys show that even if the investigations were carried out in the best harbour seal areas on Sàr eelgeland, only a total of 30 harbour seals were observed. This indicates that the population of this species issmallelp than estimated on SOrhelgeland. Oynes (1964) estimated that there were a total of 130 harbour seals in the Vega-Bronnoysund area in the early 1960's. However, the survey in Mellom-Vikna showed that the population is greater than the 80 harbour seals estimated by Oynes (1964). Counting of grey seal pups from a boat in the Halten- Froan area was carried out from September 21 to October 9.

A total of 123 pups were observed. Since only a part of the 49. whelping area was covered and a considerable number of pups are born also after October 9, it must be assumed that many more pups than these 123 are born in the Halten-Froan area. To the west of Vega from Fuglevaer to Gasflesene to the Southwest of Muddvaer, a total of 36 grey seal pups were observed between October 17 and 23. In the same period and area, 57 pups were observed in 1977. This decline can be explained by the fact that about 20 sexually mature grey seals were killed here in 1976. It must, however, be pointed out that the total production is greater than 36 pups since a number of pups were no doubt born after the investigations were completed. Counting of grey seal pups on Halten-Froan from an airplane was carried out on October 3 for the first time and a total of 50 whitecoat pups were seen. Due to an extended period with poor weather, a new air survey could not be carried out before November 22. Only Orskjaerene (Ors Skerries) on More was then covered. A total of 3 adults, but no pups, were seen. The next survey was carried out on December 6 in the Halten-Froan and Melsteinen areas in Sor-Trondelag, Vikna in Nord-Trondelag and Vega in Nordland. The pups had then gone in the water and only 1 pup and 6 adult grey seals were seen.

Killing and Sampling

In Mellom-Vikna from June 24 'to 29, material was collected for ageing and also reproductive organs and stomach contents from 10 harbour seals (5 males and 5 females). • _

In addition, two grey seals (1 male and 1 female) were sampled in the same area. In connection with parasite studies, samples of cod and cusk were also collected in three locations and also several samples of bottom animals. some of this material is being worked eu as part of a thesis at the University of Oslo. In cooperation with local fishermen, a further reduction of the grey seal population was carried in an area between October 17 and 23. A total of 36 pups, a young animal, an adult male and 17 adult females were killed.

From these, mater ial for age studies was collected as well as re- productive organs and stomach samples of 6 adult females. In 1977 a total of 44 pups and 26 adult grey seals were killed in the same area.

Seal tagging

In the Halten-Froan area in S6r-Tr8ndelag a total of

99 grey seal pups were tagged from September 21 to October 9. Five recaptures showed that the pups moved as far as 4 nautical rildes before they were 3 weeks old. In November and December, a p. 22 total of 3 recaptures were made from this tagging to the south of Halter', two of these as far as 70 nautical miles from the tagging area. A grey seal pup that was tagged on Floholmene off Skibbatsvaer in Nordland in October 1976 was recaptured at Myken in Nordland, about 45 nautical miles further north, in January 1977.

Age of Sexual MaturitY 51.

Analyses of ovaries from 13 grey se l s showed that most seem to have their first pup when they are 4 to 5 years

as is, old. This is the same age of- sexual maturityfound for grey seals in Eastern Canada, (Mansfield and Beck 1977). 52.

1.MT.HATUR III_NJAP.INSLN, T., BEI:ci cr..), B., FizoLm.u, A., liusE, 1., og Olaisticio, T., 1975. SelundersoLelser i (let nordlige Atlanterhav 11974. Fiskets Gang, 61:381-389. - BERGFLODT, B., og liusE, 1. 1976. Tclling av havert pà Norslekysten Ira Halten — Froan tu lBuda og under- . sokelse av kveisinfeksjonen i fisk ved Vega. Fiskerins- , rineens Forsek.doncl «Rapporter» nr. 1-2 1976:17 -22. ' - BI-.KGFLODT, B., HUSE, 1., BRODIE, P., og TOKLUIL, K., 1977. Undersokelser av havert pà norskekystr_n ira Lofoten dl Freya, september—november 1976. Fiskeri- ncringeru Forsoksjond, «Raeoriet» nr. 1, 1977:24 — 33. MANsFIELD, A. W., and BECK, B. 1977. The grey seal in eastern Canada. Tech. Rep. Fih. mar. Seto. Can., 701:1—xi, 1-81. YOUNG, P. C., 1972. The relationship between the presence of lai-val anisakine nematodes in cod and marine mammals

in British home waters. J. Ecol., 9(2):459-4'85, 2 pls. OYNES, P., 1964. Sc! pà norskekysten Ira Finnmark til Mere. Fiskets Gang, 50:694 —707.

Benjaminsen et. al. 1975. Seal investigations in the Northern Atlantic in 1974. Fiskets Gang, 61:381-389.

Benjaminsen et. al. 1976. Counting of grey seals on the Norwegian Coast from Halten-Froan to Bodo and investigations of the nematode infection in fish at Vega. Fishing Industry Research Fund. "Reports" no. 1-2, 1976:17-22.

Benjaminsen et. al. 1977. Grey seal investigations on the Norwegian Coast from Lofoten to Fr'oya, September- November 1976. Fishing Industry Research Fund, "Reports" No. 1, 1977: 24- 33.

Oynes, P. 1964. Seals on the Norwegian Coast from Finnmark to M ire. Fiskets Gang. 50:694-707. 23

"Her ble det ogsà sett 5-10 havert som là sammen med steinkobbene"

"Here were also seen 5 - 10 grey seals together with harbour seals". 54.

Directorate of Fisheries Institute of Marine Research p. 24 Bergen. Report, January 29, 1979.

Harbour Seal Investigations on the More and Trbndelag Coasts in 1979. by • Terje, Benjaminsen

In cooperation with the University in Oslo and with assistance from the Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada, the Institute of Marine Research carried out harbour seal investigations on the coast from Aalesund to Smola and in Nains Fjord from June 1 to July 3, 1978. The program included tagging of pups, counting of seals, collection of reproductive organs, stomachs and jaws, and also the measurement of lengths and weights of up to 150 harbour seals. Cruise participants: Terje Benjaminsen (1/6 - 3/7) Bjbrn Bergflbdt (13/6 - 3/7) Arne Bjorge (7/6 - 23/6) Paul Brodie, Bedford Institute (1/6 - 3/7)

Tagging

Rototags were used in the tagging of harbour seal pups. A total of 28 pups were tagged. Of these, 21 were tagged off Haroy to the west of Molde and 7 on Orskjaerene off Kristiansund. One of the pups tagged on Orskjaerene was caught in a monofilament mackerel gillnet in the Lyse Fjord to the south of Bergen two months after tagging. This pup had travelled 222 nautical miles. Another pup tagged off p. 25 Haroy was recaptured in flounder nets at Àrsund on Nordmàre, two months after the tagging. These recaptures indicate that the younger harbour seals are not as stationary as earlier assumed.

Counts

Figure 1 shows the result of counting harbour seals on the coast between Aalesund and SmOla. The area from Vigra to Flemsoya was investigated between June 3 and 8. A total of about 100 harbour seals were observed here. The largest number was seen on Lepsàklovningen to the west of Leps6ya where about 40 harbour seals were observed on June 3 and 4. Here were also seen 5-10 grey seals together with the harbour seals. The area to the west of Fjàrtoft and Haroy to Ona was covered in the period June 19 to 23. On the coast between Fjàrtoft and Harày a total of about 250 harbour seals were observed. The most important localities here are Gronnvaeret, Oddan, the Eknes-Skerries, Havsteinen and Skrapen to the west of Harày. From Sand6y, Ona to Saltsteinen a total of 260 harbour seals were seen. The seals were spread over the whole area with the largest concentrations to the northeast of Ona and in Saltsteinen. Orskjaerene outside Avere.ya was investigated from June 12 to 17 and from June 26 to 30. On the last trip

• 56.

Ravnene to the east of Orskjaerene was also visited. On

Orskjaerene a total of 200 harbour seals and 4 grey seals were observed. Most of the animals were seen in the north- eastern part of this group of skerries. On Ravnene an estimated 150 harbour seals were observed. Since the distance from Orskjaerene to Ravnene is not more than L. nautical miles, these animals can have moved from one island group to •another and therefore represent double observations. SmOla was visited June 9 to 12 > and only one harbour seal was observed. On July 1 Namsfjord was investigated. A total of three harbour seals were observed close to the mouth of Namsen.

Nutritional Studies

A total of 31 stomachs of harbour seals were collected.

Nine of thesestomachs contained remnants of herring. Redfish were found in four of the stomachs and cod in one. The volume of fish remnants varied from 0.5 dl to 10 dl with an average of 5 dl. Seventeen of the stomachs contained sterns of kelp with a volume from 0.5 dl to 5 dl.

Parasites

Nematodes in the stomachs have not yet been determined as to species. There were from L. to 250 nematodes in the

31 collected stomachs. This is an average of 26 per seal. Jr- • ?KRISTIANSUND v

‘ 1-Li • e, 7-1

ORSKJERENE

Fig 1. Number

of harbour seals observed from

Aalesund to

ONA • C> (1 ee*tr \_ . 13 HÂ8yA VP

epe yr . • 1 • 2 0 z • 3

e --, ° D ■ ID it

00 58. 28

"Merkene ble festet tu l svommehuden pà havertenes baksveiver"

"The tags were fastened to the webs of the grey seal's hind flippers" 59.

Directorate of Fisheries, Institute of Marine Research Report Nov. 22, 1978. Bergen Revised Nov 13, 1980.

Grey Seal Investigation in the Fall 1978. by Arne Bjorge

Personnel: B. Bergfle)dt Institute of Marine Research K.A. Fagerheim A. Bj'orge University in Oslo M. Brônndal ” V. Depuis A. Skadsheim B. Berland University in Bergen D. Fraser University of California

K. Parker 11 tt

Two rubber boats with 28 and 40 Hp outboard motors were used for the investigations. A tagging program on yearling pups of grey seals at Halten/Froan was carried out in the period October 4-13. A total of 91 pups were tagged. A modified cattle tag, "Jumbo Rototag" was used. Sixty of the pups were also double tagged with the tag "Allflex" in addition to "Jumbo Rototag". This was done in order to compare how long the tags would stay on. The tags were fastened to the webbed part of the tail p. 30 flippers with the help of special tongs. The tongs for 60.

"Jumbo Rototag" functioned satisfactorily while the tong for "Allflex" caused some problems. In addition to the tagging, parasite and age material was collected in the Halten/Froan area and also other biological parameters from twelve grey seals and four harbour seals. In the Fuglevaer area to the west of Vega, the preceding year's project) aimed at reducing the grey seal population in a limited area) was followed up. In the period October 17-27 a total of six adult grey seals (five were sampled) and six pups were killed. Weather conditions made it impossible to cover the whole area. Two of the most westerly and most exposed islets (Allflesa and Trollkona) were not investigated, but the whole annual production of grey seals that could be observed in the rest of the area were killed. Information from local fishermen indicatesthat some grey seal pups were killed in the Fuglevaer area before the October 17. This fact taken together witirrecent years' kill could be the reason for so few animals being observed in this area. Difficult weather conditions and problems with the outboard motors limited to a considerable extent the efficiency of the survey. , 61.

"Close to four times the estimated population in 1963". 62.

Directorate of Fisheries p. 32 Institute of Marine Research

Bergen Report, January 4, 1979

Investigations of Harbour Seals on the Coast between Statt and Br8nn6vsund in 1979. by a Arne Bjorge

The Institute of Marine Research carried out harbour seal studies in the field between Statt and Bronnoysund during the period June 25-July 17, 1979. The purpose of the cruise was counting, collection of age material and reproductive organs for evaluating the population, the collection of stomachs for nutritional and parasitic studies, and finally, tagging of pups. The cruise was carried out with two rubber boats with ôutboard motors and with base onboard M/V "Sorry" of

Aalesund) skippered by Guttorm Pedersen. "Sorry" is a 38-foot aluminum boat built for passenger traffic and was suitable as a mobile base which increased the efficiency of the cruise.

Cruise participants: Bjorn Bergflodt Institute of Marine Research Arne Bjôrge “ Kjell-Arne Fagerheim Morten Bronndal University in Oslo •■• 63.

Counting

Due to time limitations, the counting was limited P. 33 to the outer skerries. For the same reason some of the localities where counting was carried out in 1977-78 and the area between the Fosen Peninsula and Folla were not investigated either. Fig. 1 shows the result of the harbour seal count. A total of 849 harbour seals and 131 grey seals were observed during the cruise. Table 1 shows the observations by county and also compared with the investigations carried out by dynes in 1963.*

Table 1. The harbour seal population in the counties of More and Romsdal, Sor-Trondelag and Nord-Trondelag.

County Animals observed Estimated population in 1979 in 1963

Me;re og Romsdal 1,071** . 1,050 Sr-TrOndelag 247 490 Nord-Trhdelag 132** 130

** The numbers include localities investigated in 1977-78.

The populations in the Haroy-area, at Orskjaera to the west of Averoya and at Tarva must be assumed to be accumulated populations. For the two first mentioned ) there is agreement between the calculations of 1963 and the counts

*Oynes, Per. 1964. Seals on the Norwegian Coast from Finnmark to More. "Fiskets Gang", 48. 64.

in 1978-79. In the Tarva area a total of 154 harbour seals were counted in 1979, close to four times the estimated population in 1963. County by county there is very good numerical agreement between the two investigations. The difference for Sr-Trondelag is chiefly due to an estimated population of 200 animals noted for Halten in 1963, a location that was not investigated in 1979. Differences in methodology in the two investigations indicate, however, that there has been an increase in the .constitute populations. The numbers from 1963 Y an estimated total of population the counties) based on questionnaires and observations, while the values from 1979 are observed animals and thereby absolute minimum values for the populations in these localities.

Collection of Samples

Age material, reproductive organs and stomachs were collected from 31 harbour seals and 4 grey seals. In addition, 8 pups of harbour seals were weighed and measured, blubber thickness and stomach content noted. The collected

material has not yet been processed.

IMELLE

Due to a delayed start of the cruise, the tagging of harbour seal pups was made very difficult. The pups were already able to swim and could not be caught in the water. Only three pups that were caught sleeping ashore were tagged. w 65.

Tags of the type "Rototags" were used. The tags are impressed with a number and the address: Havforskning, Bergen, Norw. 35 66..

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"torskekveis utgjor praktisk tait hele rundormfaunaen i magesekken hos havert"

"Cod "kveis" (cod worms) comprise practically the whole roundworm fauna in the stomach of the grey seal". „ 68.

Directorate of Fisheries Institute of Marine Research Bergen Bergen, January 4, 1980.

Investigations of Grey Seals in the Whelping

Period in the Fall of 1979. by Arne Bjorge

The Institute of Marine Research carried out field studies of grey seals in the whelping period between October 8 and 20, 1979. The purpose was to tag pups at Halten- Froan and map the whelping progression in the same area. Furthermore, counting of grey seal pups between Froya and Vega from the air and an experimental reduction of the grey seal population in a defined area to the west of Vega were to be carried out. A two-engined.plane of the type Piper Navajo” from Tronderfly A/S was used for counting from the air. For tagging and killing two rubber boats with outboard motors were used for transportation.

Participants: Bjbrn Berflè,dt, Institute of Marine Research

Arne Bjarge, 11 11

Kjell-Arne Fagerheim, " 1 1 Morten Bremndal, University in Oslo • 69.

Results

Up to October 14,a total of 137 grey seal pups were tagged at Halten-Froan. The whole area between Finnvaer lighthouse and Halten lighthouse was investigated, and it is reasonable to assume that more than 3/4 of the pups born in the area at that time were tagged. The area was investigated again on October 24-25, and another 31 pups tagged. A total of 168 grey seal pups were tagged in 1979. In connection with the tagging it was observed that more than 1/3 of the grey seal pups had clumps of sticky oil in their pelts. Some of the pups were quite badly smeared with oil. The whelping progression was determined by estimating the age of the pups. Their ages were determined on the basis of if they had umbilical cords and how far moulting had progressed. Timing of whelping up to October 25 is shown in Fig. 1. Pupping started already on September 2k.. and the greatest activity was observed in the period October 5-17, fLy witheaximum on October 12. The activity decreased towards the last observation date, October 25.

Aerial counting was carried out on October 15. Outside the area already investigated at Halten-Froan, a total of 91 grey seal pups were observed between Froya and Vega. The largest concentrations are given in Table 1. Outside these localities there was only scattered whelping. '1 70.

4:4V-LL UNGER No. of pufis 25'

20 .1.0.1•1 MBA.

111■111 15

■••■•• •■■■■ 10

fl 22 0X1. MTO SEPT.24. 2. 23. 30. 2. 4. G. 8. 10. 12. 14. 1G. 18, 20.

Fig. 1. Whelping of grey seals at Halten-Froan from age estimation of 182 pups in 1979.

Table 1. Large concentrations of grey seal pups on the stre±ch between FrCiya and Vega. Counted from the air October 15, 1979.

Locality No. of Pups

Grogna north of Froya 10 Melsteinen 28 Hortavaer at Leka 15 Fuglevaer at Vega 22

In the Fuglevaer area a total of 16 pups and 9 adult grey seal pups were killed. The whole area was covered. Except for 1978 ) when the work was hindered by poor weather and the fact that an unknown number of pups were killed by local fishermen, the number of pups killed is assumed to be proportional to the yearly production and therefore to the grey seal population in the area. Table 2 shows the number of pups killed yearly in the Fuglevaer area from 1976 to 1979.

Table 2. Number of grey seal pups killed yearly in the Fuglevaer area from 1976 to 1979.

Year No. of pups killed

1976 47 1977 36 1978 6 1979 16

Investigations carried out in Great Britain* indicate that the number of cod nematodes (Phocanema decipiens) per grey seal increases with increasing population density of grey seals. Parasite samples have been taken every year of one year old and older grey seals in the Fuglevaer area. Species determinations show that Phocanema comprises practically the total nematode fauna in the stomachs of grey seals staying in the area.

Table 3. The number of nematodes per animal in grey seals killed in 1976-79 at Fuglevaer to the west of Vega.

* Young, 1972: The relationship between the presence of larval anisakine nematodes in cod and marine mammals in British home waters, J. Appl. Ecol. 9:459-484

' 1 72.

Year No. of grey seals studied No. of nematodes per grey seal.

1976 12 2 005 1977 6 1 195

1978 3 1 024 1979 2 328

A reduction of a grey seal population will therefore lead to a more than proportional reduction ini the incidence of nematodes. l• é 73. 41

"Det synes à vœre en klar sammenheng mellom stein- kobbenes aktivitetsrytme og flo - fjœre rytmen" "There seems to be a clear connection between the activity rhythm of the harbour seal and the low/high tidal rhythm". 74.

Directorate of Fisheries 42 Institute of Marine Research I" Bergen Bergen, August 14, 1980

Investigations of Harbour Seals and Grey Seals Summer of 1980 by Arne BjOrge

The Institute of Marine Research carried out field studies of grey seals and harbour seals on the coast between Aalesund and Bodà between June 15 and July 8, 1980. The purpose of the studies was to count harbour seals in the whelping period and to map the grey seal distribution outside the breeding season. The daily rhythm of the harbour seal was also to be studied and harbour seal pups tagged. Samples of both harbour seals and grey seals were to be be collected. as well. The work was carried out with two rubber boats with outboard motors and with base onboard M/B "Sorry" of Aalesund, skippered by Guttorm Pedersen, Aalesund.

Participants: Bjorn Bergflàdt Institute of Marine Research Arne Bjbrge Kjell-Arne Fagerheim

Gunn Nilsen ti Kjell Toklum University in Bergen 75.

Counting and mapping of the population

Except from Hustadvika and along the Fosen Peninsula to Fold, the whole outer skerries area from Stadt to Vega was investigated in 1977-79. The counts on this cruise were concentrated on the areas mentioned above that had incomplete coverage in 1977-79 and also further north.from Vega to the Salt Fjord. The number of animals observed in the areas studied are shown in Table 1. The numbersof animals observed aria absolute minimum populations. Except for the area Vigra-Galleskjaer and Orskjaer-Ramnana where counts were very thorough, it is not unreasonable to assume that the real populations are 10-30% higher than the numbers given. The grey seals congregate in September-October in colonies in order to whelp and to mate. The most important whelping area is the Halten-Froan area in SOr-TrOndelag. This is also the southernmost known whelping colony in Norway. Between Halten and Mosken in Nordland there are several smaller whelping colonies of grey seals. Outside the whelping period the distribution of grey seals is little known. The southernmost observation of grey seals was made at Lepsoyklôvningen (position 62° 39'20"N 06°02 1 30"E) where 4 grey seals were seen. About five grey seals were seen in this area in 1978. 76.

Omràde Antall dyr No. of Animals

-More og Romsdal Siadt - Runde 51 Vigra - Flemsoy 121 Fjortoft - Haroy 250 Sandoy - Ona - Galleskjœra 260 Orskjœra - Ramnene 350 Grip - Smola 46 Sum 1 077 Sor-Trondelag Froya - Halten (J 3 Tarva - Tristeinen 162 Buholmràsa 12 Sum 267 Nord-Trondelag Namsenfjorden Vikna 15.) Hortavœi% 40 Sum 193 Nordland tu l Saltfjorden Bindalsflesa - Horsvœr 38 Lyngvœrfjorden 15 - Vegaomrâclet 5 Lànan 12 Selo}, 15 Valvœr 5 Sum 90

r;tadt - Saltfjoptien totalt 1 627

Table 1. The number of harbour seals observed in the area Stadt-

Saltfjorden. Table based on studies in 1977-1980. 77. 1. 4 •

Outside the whelping period, smaller concentrations of grey

seals seem to be common along the outer skerries from More to Salt-

fjorden, but with increasing density in the neighbourhood of the

whelping areas.

In More and Romsdal, harbour seal is the domineering species,

but the relative population proportions change northwards. In the

Trondelag counties both species are numerous, but in Nordland grey'

seals dominate by number. •

Collection of Samples

Samples of 22 harbour seals and 6 grey seals were collected.

The samples comprise age material, ovaries for reproductive studies

and stomachs for nutritional and parasite studies.

Tagging of Harbour Seal Pups

Eighteen harbour seal pups were tagged. The pups can swim a

few hours after birth and they spend much time in the water together

with the mother. The tagging was carried out by fastening a yellow

plastic tag of the type "Rototag" to the tail flipper of pups

caught in the water. The pups are let go immediately and can be

observed together with the mothers shortly afterwards.

Daily " -■ rhythm studies of Harbour Seal. p. 45

The daily rhythm of harbour seals is divided into

periods when the animals seek food and resting periodswhen they

haul up ashore. This rhythm was studied by counting the number of

animals ashore in a 24 hour period. • 78.

Two colonies were studied: at Orskjaer on MOre, June 18-19 and at Hortavaer in North Trondelag, June 26-27. Due to distances in time and place l the low-high tidal rhythm was 4 hours 24 minutes later at Hortavaer in relation to Orskjaer.

At Orskjaer the greatest number of animals observed was 119 while at Hortavaer the colony observed had 29 animals. In order to make the comparison easier, both colonies were calibrated to 100 animals. ,solar day The number of animals ashore is shown in relation to the Y—in Fig. 1 and in relation to low-high tide in Fig 2.

There sems to be a clear connection between the activity rhythm of the harbour seals and the tidal rhythm , with feeding at high tide and resting at low tide.

Variations according to the solar day in Fig 1 can be at least partlyrexplained by the fact that the time difference between high and low tide between the two observation days was about 4.5 hours.

At Orskjaer, parts of the population only had one active period per 24 hours .

This period was at night. The animals that remained ashore at high tide at night were chiefly newborn pups. AN TALL No. of animals ashore DYR PÀ LAND FLO = high tide FLO FLO FLO 100 I OR SK J . -OR SKJ H.V£R A \ ; iit I 1 I '11 V, • . ■ 50 Y t/ r e % 1 I. t I I I 141.

° -071 03 (-)5 07 09 11 13 15 17 19 21 23 KLOKKEN = time

Fig. 1 No. of harbour seals ashore in relation to solar eiait. - - - - at Orskjaera on More at Hordavaer in Nord Trondelag and mean number ashore. Both colonies calibrated to 100 animal.

DyHAN T ALL No. of animals ashore PA LAND 100

50

0 TID TIM.ER . hours time_ -

Fig. 2. No. of harbour seals ashore in relation to high-low tidal rhythm. at Orskajaera on More, at Hordavaer in Nord Trondelag and mean number of animals ashore and low-high tidal rhythm. Both colonies are calibrated to 100 animais.