...., ' .,

1 This paper not to be cited without prior reference to the authors

International Council for C.M. 1988/N: 12 the Exploration of the Sea Marine Mammal Committee

DIET OF THE PILOT WHALE, GLOBICEPHALA MELAS, AROUND THE FAROE ISLANDS. by

Genevieve Desportes Natt1lrugripasavn -Futalag qO, FR-100 T6rshavn, F0royar.

and R6gvi Mouritsen • Fiskiranns6knarstovan Debesartr~6, FR-IOD T6rshavn, F~royar.

ABSTRACT The diet of the Pilot Whale was studied from the Faroese whale drive fishery. Pods of whales were sampled in all months of the year, from July 1986 to December 1987. The stomach contents of around 20% of the whales within target pods were examined both qualitatively and quantitatively. This gave a total of 720 stomachs of which 77% contained food remains. The list of items identified included 9 genera of Cephalopods, 1q genera of fish, plus shr~ps and miscellaneous other items. These prey were of different ecological or behavioral types, but all of them were fairly comnl0n species in the locality of the catch. The Pilot Whale is mainly a squid eater around the Faroes with Todarodes • sagittatus and Gonatus s~ as the main prey. Pilot Whale diets varied according to the length of the animal, the season and the year. When T. sagittatus was available, the diet was nearly exclusively of this prey, despite the availability of the other usual prey. If not available, the diet was supplemented with a large range of items including fish, suggesting an opportunistic foraging behaviour. This feature appeared clearly from the comparison of the diet in the summers 198~, 1986 and 1987.

INTRODUCTION Data on pilot whale diet are usually limited to the listing of the species found in' a few stomaehs (Mercer, 1967; Tomilin, 1967; Moore et alt 1979; Martin et al, 1987). They have been reviewed by Mitchell (1975) and Evans (1987). Hcwever two studies. carried out in Newfoundland (Sergeant, 1962) and in the Faroes (Desportes, 1985) , . • J

2 attempt to evaluate the daily food intake and the relative importance of the prey. Cephalopods form the bulk of the food, and seasonal movements of ~ mel~ towards the coast in some areas have been related to inshore movements of squid species, e.g. Illex illecebrosus in Newfoundland (Mercer, 1975) and Todarodes sagittatus in the Faroes (Hoydal, 1987).

As shown by Clarke (1983, 1985, 1986) a knowledge of the predator's diet combined with a knowledg8 oE th~ prey biology and behaviour can lead to a much better understanding of the predator itself or the food chain in general. Stomaeh examination can throw some light on the migration of the whales, or shorter movements, if some prey can be assigned as markers because of their restricted distribution, geographie or bathymetric, or their absence in the locality of the catch. The estimation of the biomass of the species consumed by the predator provides information on its place within the ecosystem and the potential conflicts. It gives also better knowledge of the importance of the cephalopods in the ocean, knowing specially that most of the species are poorly sampled by nets. The study of the long finned Pilot Whale undertaken in the Faroese drive fishery, over aperiod of four years and covering all months in the year, should contribute to this aim. The study is not completed yet and only preliminary results are presented here.

MATERIALS AND METHODS Sampling The stomach analysis was carried out on 720 pilot whales of those driven onshore in the Faroes between July 1986 and December 1987. From each pod, stomaehs of all the whales of 3 meters long or smaller and of about 10 bigger animals were examined, i.e. 20% of the whales. In Table 1 are given details on the sampling. The pilot • whales examined were of both sexes and all lengths. Table 1. Details of the sampling.

YEARS 1986 1987 TOTAL

No of pods sampled 16 17 33 Menths represented 7,9,10, 1,2,3,4,5 all, 11,12. 7,8,9,10 expt 6 No of stomachs: - examined 380 340 720 - empty 29 43 72 - containing milk only 59 34 93 - containing food remains n 278 277 555 (with er without milk) Y. 73% 81Y. 77% - containing flesh remains n 1 9 10 (with or without·milk) y. <.lX 2.6Y. 1.4Y. ------3

The pilot whale diet data obtained by the first author in 1981r in the Faroes will be u~ed in comparison to enlarge the temporal spread of the stornach examination. Searching

The Pilot Whale stornach comprises 3 compartments: the fore, the main and the pyloric stomaehs as in all other delphinids (see Despor­ tes, 1985, for more details). All three could contain hard remains of prey i.e. cephalopod beaks, fish otoliths or bones. Most flesh was found in the first compartment, though partially digested flesh, as cephalopod crowns or buccal masses, could also be retrieved from the second. For all whales, the three compartments were opened and very carefully searched in the laboratory. For c. one third of the whales, the whole intestines were also searched, but seldom contained any remains. Flesh remains were kept in 5% formalin, beaks and bones in 70% alcohol and otoliths dried. Identification

Prey could be identified by visual inspection and cephalopod flesh could be distinguished from fish flesh. Nevertheless, because the usual lack of flesh, most of the prey were identified to the genus or species level from closer examination of the beaks or otoliths. Size and weight of the identified prey were then obtained from the lower rostral length of the cephalopod beaks and the length or weight of the fish otoliths. The methods used for identification and the relationships giving the length and weight of the prey from their hard parts are described elsewhere (Clarke, 1962, 1980, 1986; Despor­ tes, 1985; Härk0nen, 1986). Quantification To assess the relative importance of the prey species in the diet, we used, as a preliminary step, their frequency of occurence in the stomaehs (~Io) and their importance by number (Cn%). • We defined four main categories of frequency of occurence and importance by number as folIows: Frequency of occurence common (flesh or hard remains found in more than 50%) frequent (50 - 20 %) infrequent (20 - 10 %) rare (less than 10%) Importance by number prime (more than 30% of the total amount of prey) secondary (10 - 30 %) low (10 -2 %) insignificant < 2 %) Throughout this paper, the term " s ignifica'nt" is used solely in the statistical sense of differences significant at the 5% level of probability. • •

RESULTS Quantity of food in stomaehs

The proportion of whales whose stomachs were found to be empty or to contain food remains (with or without milk) did not vary sig­ nificantly between 1986 and 1987 (X 2 = 2.~, D.F.= 1, P> 0.1). They did not vary either between '8~," '86 or '87 (X 2 = 5.1~, D.F.= 2, P> 0.05).

It is notable how low is the proportion of stomachs found to contain flesh remains in '86-'87 (F= 1,~%). Table 2 gives the per­ centage of stomachs found to contain flesh or just indigestible prey remains in August and September of '8~, '86 and '87. The proportion is already significantly greater in '87 (X2= 7.23, D.F.= 1, P< 0.01), and the variation becomes highly significant if considering "'8~ (X 2 = 135.~, D.F.= 2, P< 0.001). The greatest quantities of flesh retrieved in any whales in either '86 or '87 was 200g of squid flesh (3 mantles partially digested), while in '8~ it was 25 kg of squid flesh. Some species of whales are known to vomit stomach contents during driving or capture. This has rarely been observed for pilot whales, for example in the case of few specimens shot on the edge of" the Faroe Bank, whose entire oesophagus was found to be full of fresh squid. Even so, if this is the only explanation of the lack of flesh in stomaehs examined in 1986 & 1987, such a dramatic change between this and the earlier sampling" period would be surprising, especially since many stomachs full of milk were recovered in all three years. The length of the drive could influence the phenomenon, but it changes a lot from hunt to hunt, from a 15 mn to several hours. In '8~ the three pods sampled were killed after 15mn, 6 and 3 hours drive, nevertheless, in all of them most of the whales were found with stomachs Eull of fresh squids. Then the general absence of flesh indicates more likelythat the whales fed less close to the islands in '86-'87 than in the s~mer of '8~. • Table 2. Percentage of pilot whale stomaehs examined in the sum~ers '84, '85 and '87 containing food remains, which were found to contain flesh or solely the indigestible remains of prey.

JULY - AUGUST 1984 1986 1987 combined

No of pods 3 4 4 11 n 59 70 61 190 Flesh Y, 88.1 o 9.8 30.5 Indigestible remains only y, 11.9 100 90.2 69.5

Prey species and relative importance in the diet Over the two years of sumpling, four main diet components were identified: cephalopods, fish, crustacea (only shrimps in the period considered) and other miscellaneous items. Their relative 5

frequency of occurence are shown in Figure 1. The Pilot Whale is mainly a squid eater around the Faroes, but fish (frequent) and shrimps (infrequent) are also eaten. Table 3 gives details of the.prey species. Figure 2 shows their relative frequency of occurence and.their importance by number. Cephalopods Up to now cephalopods have only been identified to genus. 8 were retrieved from our sampIe; in addition beaks of 4 more, one thought to be Megalocranchia, were present. Between these genera or species, two were far dominant: - Todarodes sagittatus with ~Io> 50% and Cn%> 30% - Gonatus sQ. with ~Io and Cn% > 47% All the other genera occured rarely in the diet except Brachio~ teuthis which appeared in 12% of the stomachs but with a low impor­ tance by number. Genera represented by flesh were 10darodes and Eledona . All the families collected have previously been recorded from . • pilot whale ~tomachs in the North Atlantic (Desportes, 1985). Fish No evidence of fish flesh was ever recorded. Most of the fish otoliths did allow an identification to the level of the species. 13 species from 6 families were identified with, in addition, otoliths from one more family. All species of fish occured rarely in the stomachs and have a very low contribution by number. Even so, two are far more common than the others, Argentina silus and Micromesistius pout~?sou. Of the 7 families represented, 3 have not previously been recorded from long finned pilot whale stomachs: Macrouridae, Zoarcidae, Trichiuridae.

Crustacea Over the period '86-'87, only shrimps were found in the stomachs. It can be wondered if these shrimps are actually pilot whale prey or indirect prey. Shrimps are small and 50ft animals which should be digested and disappear rapidly froIn the stomachs, particularly • if they are prey of prey which means already· partially digested. Their occurence in stomachs containing only indigestible remains of prey or no remains at all, i.e. as the freshest prey, together with for some of them a fresh aspect, indicate a strong circumstatial evidence for shrimps being a direct prey oE the pilot whale, at least in some cases. To our knowledge, shrimps were not previously recorded as being direct prey oE the Pilot Whale. Miscellaneous other items These occured rarely in the stomach.If not secondary prey, they can be considered as accidentally taken. Stones were infrequently retrieved in the forestomach but always in small number and size.

Diversity in the stomaehs

Even iE the Pilot . Whale can Eeed on a large range oE items ,---- -~------

6

around the Faroes, the diversity of the prey in the stomaehs is quite lew with 48% of the stomaehs eontaining not more than one speeies, as shown in Table 4.

The total numt,er of prey represented by remains (fish and cepha­ lopods eombined) is 7249. An average of 18.3 prey were found per stomaeh, with a maximum of 380 (all Gonatus beaks) in a single stomaeh.

Table 4. Prey diversity in the pilot whale stomaehs over the sampling period July 1986 - December 1987.

No No species/st. y. st. with st. max aVe 1 spec ies

Fish + Cephalopods 382 8 1.91 47.9Y. Cephalopods 359 6 1.65 57.7Y. • Fish 91 5 1.43 69.2Y. Changes in the diet aeeording to the length of the whales As notieed in '84 (Desportes, 1985), the size of the prey inerease with the size of the pilot whale. Considering only Todarodes sagittatus, for the whale smaller than 300em, the average mantle size of the prey is e. 17em and the maximum e. 25em. For the larger animals, the average mantle size is e. 20cm and the maximal size c. 50cm. For the month of September 1986, the frequeney of oecurenee of the eephalopods (C), fish (F) and shrimps (S) did not vary signifieantly in the diet of the four following elasses: - 1) whales below 300em long - 2) females over 300em long - 3) males between 300 and 500em long - 4) males over 500em long. (F and non F: X2 = 1.05, D.F.= 3, P)0.9; C and non C: X2= 5.62, D.F.= 3, P> 0.2; Sand non S: XZ= 1.45, D.F.= 3, P) 0.9). Nonetheless, young individuals fed preferably on small prey, • whieh can be either the smallest individuals of a speeies or a small speeies. Sepiola e.g. has an oeeurenee of 66.7% with an importance by nurnber of 60% in elass 1. In the groups 2 and 3, it oceured in less than 15% of the stomaehs and represented less than 10% of the prey. It didn't oceur in the stomaehs of the bigger males (group 4). These changes are illustrated in Figure 3. Changes in the diet according to the season and year The diet of the pilot whale varies with the availability of the prey species in the viscinity of the Faroes. Fish were more frequent and important in winter time, even if eephalopods are the" bulk of the diet. More speeies were taken and the diversity is greater in the stomachs. In sum~er nearly only cephalopods were eaten, with one or two species dominant, and the diversity decreases in the stomachs. 7

The importance of prey availability appears clearly from the comparison of the diet over three years 1984. '86 and '87. for the months August and September when T. sagittatus is thought to be on thc Faroese shelf. The results are illustrated in Figures 4 and 5 as weIl as in Table 5. and show the following:

- 1984 was an exceptional year for the Faroese Todarodes fishery with 1147.3 tons landed. · only one prey group appeared in the stomachs. the cephalopods. · the diversity was of course very low. · T. sagittatus did occur in all the stomachs and represented 96% of the beaks. · another genus, Gonatus, appeared in 40% of the stomaehs but con­ tributed only 4% of the beaks. - 1986 when no Todarodes at all were landed . the cephalopods represented the main diet component, but fish occured commonly in the stomach even if they accounted for only 10% • of the numberof prey. · M. poutassou occured in one fourth of the stomachs, and one other species appeared still in 16.6% of them. · 8 species of cephalopods were recorded. of which 3 occured at least frequently. Gonatus was by far the dominant species with ~Iu . and Cn% of about 80%. Todarodes appeared still in one fourth of the stomachs but represented only 2% of the beaks. · the diet was more diverse with only one third of the stomachs containing only one prey species. - 1987 was a poor year for the fishery, only 10.7 tons were landed. The presence of Todarodes was recorded in some fjords but at deeper levels than usual. the diet was mainly centred upon cephalopods but fish were recorded. · 7 cephalopod species were identified and the diversity was greater than in 1984 . T. sagittatus was again the dominant species, but two others appeared frequently in the diet even if they accounted for only 10% • of the prey.

Table 5. Diversity of the diet in the months August and September of 1984,86 and 87.

Number of species Y. st. aVe no. n ident. max aVe with 1 sp. prey/st.

1984 35 3 2 1.42 57.1% 103.5 1985 45 13 5 2.5 32.5% 47.3 1987 50 8 4 1.52 48.3% 13.2 8 DISCUSSION Methods

As pointed out in other studies (Hyslop, 1980; Bigg & Pere=. 1985; Clarke. 1985; Martin & Clarke, 1986; Murie. 1987; Prime & Hammond. 1987), the problem inherent in diet analyses is the differential rate of digestion of the various components which lead to overestL~ate the importance cf 50me of them. The soft tissues of different species are likely to be digested at different rates: cephalopods, specially the non muscular, are quicker to disintegrate than fish; smaller prey will disappear before larger. tougher species. . The otoliths and beaks are known to accumulate in toothed whale stomachs for several days or even weeks, e.g. in the case of the sperm whale (Clarke, 1980). The time which the remains from different species stay in stomachs undoubtedly varies according to their size, fragility and composition. Otoliths and beaks differ in • this respect, even the otoliths of different groups of fish, e.g. gadids and clupeids, and some species have no otoliths e.g. sharks. Miller (1978) found that in fur seal stom~chs, squid beaks stay several days whereas otoliths passed through rapidly. The use of the otoliths, in particular, to calculate the importance by weight brings additional biases. Their erosion during digestive process leads to a 10ss in dimension and perharps density which is difficult to evaluate and depends again on their original shape. . Thus in our study the import:ance of thc fish spccies is likely underestimated, and heterogeneously according to species.

One way of overcoming this ~roblem could be to look. at the occurence of cephalopod statoliths, which having tne same structure as the otoliths, are more likely digested at the same rate. The relative proportion of fish and cephalopods in the diet could also be assessed in using eye lenses. However this would not avoid the problem of different sizes of indigestible remains disappearing at different rates. To evaluate the biases inherent in the various • methods, future work could profitably compare them on .two representative samples of stomachs, one containing flesh and the other only indigestible remains. A further problem deriving from the exclusive use of hard remain is to determine which are the remains of direct prey and which the remains of secondary prey. In particular, it has to be taken int6 account that many of the prey species found in a single stornach are capable of eating each other. Since the bias introduced by the method has not been estL~ated and the importance of the prey by weight not used, this study doesn't necessarily provide an exact measure of the relative importance of thc prey in the diet. Nevertheless we feel confident that the appoximate rank order of importance estimated here is correct.

The Pilot Whale is mainly a squid eater around the Faroes as previously noted in the other studies quoted, dealing with other 9

areas. Two species appeared to be dominant, ~o~ittatus and Gonat~s s~, but the diet can be supplemented with a large range of items included fish <'md shrimps.

All the species identified in the stomaehs are fairly co~mon around the Faroes. Even though Gonatus is not thought to be on the Faroe shelf. it is still very abundant further offshore to the north of the Faroes in deeper water. The prey species are usually either oceanic or neritic but some typically inshore species were recorded e.g. Sepiola and Saithe. Most of the species are in mid-water or at least known to accomplish vertical migration (e.g. Todarode~. Argen­ tines, Rat-tails, Greenland Halibut) and thus may have been taken there. Nevertheless some are typically demersal species e.g. Eledona, Torsk or Eelpout. The prey can be found either above rocky bottom or soft bottom. Most of them are gregarious species. Nearly all the ~quids present in the diet are l~~inous speciez. It seems that the pilot whale. like most of the cetacea, is an opportunistic feeder. It foragez on different type of prey "easy" to catch and its diet will reflect the availability of the varlous species. Yet pilot whales don't exploit all the available abundant food resources of a zone. In our sampie cod are not present in the diet nor herrings, when they are common species in the neritic zone. Pilot whales show certain preferences in their diet. Squid are clearly indicated as the favourite prey. In the S~Tmers of '86 and '87 no dramatic changes were reported in thc availability of the f ish on the Faroe plateau. nevertheless t!-le pilot ,...hales w~re feeding north on Gonatus. At a time comnon speciesof fish may become dominant if necessary; e.g. 70% of the whales in a pod caught in july '86 were found to contain otoliths of the greater argentine. The same feature is reported from Newfoundland by Sergeant (1962) with cod and by Mercer (1967) with greenland halibut. There is also selectivity a~ongst the cephalopods, in August-September when T. sagittatus is present on the Faroe shelf the diet becomes nearly monospecific; the same pattern has been observed on the edge of the Faroe Bank .where 8 specimens were • caught with stomaehs full of fresh Loligo forbesi, beaks of the same species, and few unidentified fish bones (R.M. pers. obs~). The cause of these preferences is not obvious. It has been mentioned for several predators,e.g. puffins (Harris and Hislop, 1978) or gannets (Nelson, 1978) that the selection could be made on the energy and nutrient contents of the prey. Yet it would be more advantageous in most cases to feed upon fish rather than squids. Still the rank of importance of the squid species, as defined so far, seems to follow the calorific values of the proy given by Croxall & Prince (1982) and Clarkeet al (1985). Pilot whales 500ms to forage at a wido variety of water depths. The main range could be c. 100-500 meters, . though they probably dive to greater depth to fed on genera such as Gonatus, Bistioteuthis, Coryphanoides. On the other hand, prey as Todarodes may be taken from near the surface at night and pilot whales have been observed feeding at the surface on the sloop of the Faroe Bank by the sacond author. On the edge of the Faroe Bank, pilot whales feed typically 10

between c. 8:00 am and c. 3:00 pm (R.M. pers. obs.). In our sample we have not been able to loo}: at periodicity in the feeding. The ~ime for complete dir,estion given by Sergeant (1962) for the pilot whales is less than 8 hours. Then the three pods sampled in 1984 had been feeding at different periods, one during the nignt, the two others in the afternoon. The periodicity may change according to the characteristics of the area. As this study is continued, and closely linked with knowledge of . the Faroese fauna, it is likely that some further light will be thrown.on these questions. Pilot whales are obviously opportunistic feeders. As a result, studies in different area and different time can yield very divergent conclusions, especially about the feeding preferences. Confirmation of the hypotheses built on stomach examination of pilot whales caught in the Faroes is depending upon a knowledge of the diet of pilot whales feeding elsewhwre and specially offshore.

ACKNOWLEDGMENTS This analysis is made possible by the great help of the staff of the Faroese Natural History Museum who help in the field sampling or the opening of the stomachs, or at least share the delicacy of the smells. We would like specially to thank D. Bloch, M. Debes-Dahl, S. Skaaning and E. Stefansson. Great thanks also to all the other people involved in the sampling and notably J. Balbuena, F. Jean-Caurant and L. Venturino. We would like to thank also the funding authorities, and specially ~. Hoydal, Director of the Faroese Fishery, who made possible the International Research Programme on the Ecology and Status of pilot whales off the Faroe Islands. REFERENCES Bigg, M.A~ and Perez, M.A. (1985) 'Modified voluMe: a frequency-volume method to assess marine mammal food habits'. Pages 277-283 in J.R . Beddington, R.J.H. Beverton and D.M. Lavigne, eds. "Marine mammals and fisheries". George Allen and Unwin Ltd •• London. • Clarke, A., Clarke, M.R., Holmes, L.J. and Waters, T.D. (!985)'Calorific values and elemental analysis of eleven species of oceanic squids (Mollusca: Cephalopoda)', J. ~ar. biol. Ass. U.K., 65, 983-6. Clarke, M.R. (1962) 'The identification of cephalopod "beaks" and the relationship between beak size and total body weight', Eul. British Mus. (Nat. Hist.) Zooi., 8(10), 419-80. Clarke. M.R. (1980) 'Cephalopoda in ·the diet of spern whales of the souphern hemisphere and their bearing on sperm whale biology', Discovery Rep., 37, 1-324. Clarke, M.R. (1983) 'Cephalopod biomass - Estimation for predation', Mem. Nat. Mus. Victoria, 44, 95-107. Clarke, M.R. (1985) 'Cephalopods in the diet of cetaceans and seals', Rapp. Comm. int. Mer. Medit., 29(8), 211-9. Clarke, M.R. (1986) "A handbook for the identification of Cephalopod beaks", Clarendon Press, Oxford; Clarke, M.R. (1986) 'Cephalopods in the diet of odontocetes', in 8ryden, M.M. and Harrison, R.J. (eds.), "Research on Dolphins" Clarendon Press, Oxford. Croxall, J.P. and Prince, P.A. (1982) 'Calorific content cf sQuid (Mollusca: Cephalopoda)'. Br. Antarct. 11

Surv. Bull., 55, 27-31. Desportes, G. (1985) 'La Nutrition des Odontocetes en Atlantique Nord Est', doctoral thesis, University of Poitiers, Poitiers. Evans, P.G.H. (1987) "Whales and Dolphins", Christopher Helm, London. I-arris, M.P. and Hislop. J.R.G. (1978) 'The food of young puffins ErateLcul~ctica', J. Zool. Lond., 185, 213-35. H~rkll!nen, 1. (1985) "Guide to the Otoliths of the Bony Fishes of the northeast Atlantic", Oanbiu ApS. Biological consultants, Denmark. Hoydal, K. (1987) 'Oata on the long finned pilot whale (GlDbicenbala m~ena Traill) in Faroe water and an attempt to use the 274 years time series of catches to assess the state of the stock', IWC Report 37, in press. hyslop, E.J. (1980) 'Stomach content analysis - a review of methods and their application', J. Fish. 8iology, 17,411-30. :-:artin, A.R. and Clarke M.R. (1985) 'The diet of sperm whales (~se1~ m~cepba~) captured between Ieeland and Greenland', J. mar. biol. Ass. U.K., 65, 779-790. ~artin, A.R., Reynolds, P. and Richardson, M.G. (1987) 'Aspects of the biology of Pilot whales (G~~~~elae~) in recent mass strandings on the British coast', J. Zooi., Lond., 211, 11-23. r':ercer, M.C. (1957) 'Wintering' of pilotwhales, Glollkenba1a..JIlw.e.na, in Newfoundland inshore waters'. J. Fish. Res. Bd. Canada, 24(11), 2481-83. Kercerj M.C. (1975) 'r.odified Leslie-DeLury population models cf the long finned pilot whale (Glpbice~ha~Laena) and annual production cf the short finned's~uid (llle~llecebr~s~) based upon their interaction at Newfoundland', J. Fish. Res. Bd. Canada, 32, 1145-52. Miller L.K. (1978) 'Energetics of the northern fur seal in relation to climate and food ressources of the Bering Sea'. US Marine Mammal Commission, Washington D.C. Report r.MC-75/08. Mi tchell, E.D. (ed.) (1975) 'Review of biology and fisheries fol"' smaller cetaceans' , J. Fish. Res. Bd. Canada, 32, 889-983. Moore, M.J., Hutten, T.C. and Cole, A.T. (1979) 'Leng finned pilot whale (Glab.i.reAb.al n melaen.a.): rrerphological and ecological

comparisons between Newfoundland and the Faroes I •. Cambridge Univ. Rep., unpublished manuscript. Murie, D.J. (1987) 'Experimental approaches to stomach centent t • analyses of piscivorous marine mamma1s • Pages 147-153 A.C. in Huntley, D.P. Costa, G.A.J. Worthy and M.A. Castellini, eds. "Approaches' to Marine mammal energetics" Soc. Mar. Mammalogy, special publication no 1, Allen Press. Nelson, J.8. (1978) "The Gannet",. T 6- A.D. Poyser, 8erkha!1'sted. Prime, J.H. and Hammond P.S. (1987) 'Quantitative assessment of grey seal diet from fecal analysis'. Pages 155-181 in A.C. Huntley, D.P. Costa, G.A.J. Worthy and M.A. Castellini, eds. "Approaches to Marine ma~mal energetics" Soc. Mal"'. Ma~malegy, special publication no 1, Allen Press. Roper, C.F.E., Sweeney, M.J. and Nauen, C.E. (1984) 'F~D species cata­ logue. Velo 3. Cephalopods of the werld. An annoted and illustrated catalogue of species of interest te fisheries', FAD Fish. Synop., 125 (3 ), 277p. Sergeant, D.E. (1952) 'The biology of the pilot or pothead whale Gl~Qice~bal~_~~qen~(Traill) in Newfoundland waters', Bull. Fish. Res. Bd Can •• 132, 1-84. lemilin, A.G. (1967) 'Cetacea', Israel Program for Scientific translations, Jerusalem. 12 Table 3. Species represented in stomachs of pilot whales examined in the Faroes between July 1986 and December 1987. (Depth and habit data of fish are given for the viscinity of the Faroes and are based on advice from the Fishery Research Laboratory of the Faroes) SQUIDS (C) Ommastrephidae 51 Todarodes sagittatus Erachiteutt>idae S7 Erachioteuthis sp. Gonatidae S2 Gonatus sp. Histioteuthidae S4A Histioteuthis A S4B Histioteuthis E Chiroteuthidae 511 Chiroteuthis sp. Cranchiidae S5 Teuthowenia sp. S9 ? Megalocranchia sp. Sepiolidae 58 Sepiola sp. Octopodidae .' 53 Eledona sp. SIND, SIND1, SIND2, SIND3 Unidentified sp., spl, sp2, sp3

FISHS (F) Habitat and rarety A;gentinidae OOm F1 Argentina silus (Greater argentine) N C DP 2-8 Gadidae F2 Micromesistius poutassou (Blue whiting) NO TC P 2-5 FI0 Merlangius merlangus (Whiting) C TC D -2 Fl1 Melanogrammus aeglefinus (Haddock) N F DP -2 F3 Trisopterus sp. (Pout) NC DP -2.5 F4 Gadiculus argenteus (Silvery pout) N C P 2-5 F14 Erosme brosme (Torsk) N CD 1-15 F15 Enchelyopus cimbrius (Four-beared rockling) Macrouridae F5 Coryphanoides rupestris (Rat tail) NO C DP 6-28 Ammoditidae (Sandeei) F7 Ammodytes sp. N C DP -2 Zoarcidae F19, Lycodes sp. (Eelpout) NO CD -2 Trichiuridae F20 sp. (Seabbard fishes) N C D 3-20 .' Pleuronectidae F6 Reinhardtius hippoglossoides (Greenland halibut) NO C DP 4-12 FI8 Glyptocephalus cynoglossus (Witchl N C D -5 FIND Unidentified fish

CRUSTACEA (5) Shrimps

MISCEllANEOUS OTHER ITENS (D) Aphrodite aculeata, Nereis sp.(mandibules) Feathers, Algae Shark eggs (? Galeus melastomus) Stones (size of a nut or smaller)

Fish Habitat: N = Neritic, 0 = Oceanic, C = Coastal, 0 Demersal, P Pelagic. Rarety in trawlers: C = Common, TC Very common, F = Frequent. Depth, given in hundred meters. Cephalopods For the Cephalopods depth and habits, we will refer on Clarke (1966, 19851 and Robert ~ (1984). • • Fig. 1 July 86 - December 87, Frequency SepL 86 100...------, Fig. 3 Cn% companson by size and sex Il:ll-----< ~ 100.------. f ~ . 601---- .. < .:lOOcm 1 / •. % 397 stomaehs Il:ll------'f------j l : 401---- r>.3OOC:m 22 I" --e- 3<1.4>500 13 401------I1~·--_l__\_--l M>5OOcrn---- 7 o r .48sl IlDAS

o I n n-o 52 55 se 9'01 r2 n SI 54"51~ Fig. 2 July 86-December 87, F% and Cn% roh - ~ 26 dr., 397 sl, 7249 preys (Fish+Ceph) 6Or------, F% comparison by Slze arid sex 100 .. _. --- so·· ....------.• -----..--.-.- Fish Il:l' .. -----.-. ------W: 40 . "'-' ----_.. _-_.._-_.__ .-

Je .-.--.-.---- - .•._._-- -_ •• - ..

20 .... ------.. _-. ------.-

.. n F'2 r4 n FlO SI 52 54" 55 51 se ~SI'OI n FJ r3 n fl1 n5 n9 FlO F'2 r4 r5 no n4 ne r2Q r"" - CrVdoPod roh f 60...-----'------, F% comparison by size and sex " so·· ------100'-- Ceph 40 -- 80

Je - ----.------1 60

20 -ml~------j 4()

20 ---_.

0 51 SJ S4Il 57 59 ~ !NJ2 ~ ()V 52 54" 55 se 511 SI'OI SNlJ CErH rnus ~ 1\.". .~:', '. .' . . ' . • ,,_...... ~~ .. __~ ...~ -,~.•~ .. --...'"'.•- .... ~ _

14

August-September 84 - Frequency 100..-----

a:l --_ .._- 3 drives 60------% 35 slomachs

20 .------

oL...L:::.::::;:::2 ov

Septeunbre 86 - Frequency 100,-----===------,

3 drives

% 48 slomachs

20

o ov

August-Seplelnber 87 - Frequency 100..-----.--==;>1------,

% 61 slomachs

ov

Fig. 4: Comparison between the months of August - September of 1984, 1986, and 1987 - Frequency of occurence of the main components. . . •• t.

15

Aug-Sept 87, F% and Cn% 4 dr., 61 sl, 806 'preys (Fish+Ceph) 100..------, 100

001--'------1 00 -

60 ------,------,--

~t_------l -

:201------,---1 20 . . l o ItL III n F3 F'5 n m n5 f19 Fl{) SI s:s S48 S7 S9 90 9'D2 F'2 f4 f6 no f14 nB F'2O 52 54,.. 55 SB SI1 9'01 SNl3 f"l!tl ~

Septembre 86 - F% and Cn%, 3 dr., 48 sl, 2268 preys (Fish + Ceph) l00..-~------, 100..------,

00 ------00 ------.----

liO .,.' - ..----.----.-.--.-'.....---...... --..---- fJ:J " -- -.----.-•••--.--

~ ------_._---- ~ _. ------_._------: --t, ~ , ,~ ~-~~-,~~-----

fI F3 15 n n1 f15 fl9 IN) SI ~, S40 51 S9 90 9-1)2 f2 r. "6 110 n. 116 r20 52 54A 55 SB 511 901 srm f;g, ~

Aug-Sept 84, F% and Cn% 3 dr., 35 sl, 3624 preys (Fish + Ceph)

120,------,

100

00-

fJ:J- ._----_._-_._----

,---,-----_..- .._--

20

o IIIIIIIIIIIII II fI F3 F'5 n f11 f15 f19 Fl{) 51 s:s S48 57 S9 9-D 902 F'2 f4 f6 f10 f14 f1B f20 52 S4A 55 SB $11 901 SNl3 f;g, ~

Fig. 5: Comparison between the months ofAugust - September of 1984, 1986, and 1987 - Frequency of occurence and importance by number of the prey species.