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Effects of oil pollution on breeding Grey Seals
Volume 7/Number 6/June 1976 Bella, D. A. & McCauley, J. E. (1972). Environmental considerations for estuarine dredging operations. Proc. WorldDredging Conf , pp. 457-478. Bothner, M. H. & Carpenter, R. (1972). Sorption-desorption of mercury with suspended matter in the Columbia River. IAEA symposium on the interaction of radioactive contaminants with constituents of the marine environment. Seattle, Wash. 10-14 July (1972). Clifton, A. P. & Vivian, C. M. G. (1975). Retention of mercury from an industrial source in Swansea Bay sediments. Nature (Lond.), 253, 621-622. Fitzgerald, W. F. (1976). Mercury concentrations in seawater and rain: Geochemical implications. In Marine Pollutant Transfer, H. Windom and R. Duce (eds.). D. C. Heath Pub. (in press). Hans, Nelson, C., Pierce, D. E., Leong, K. W. & Wang, F. H. (1975). Mercury distribution in ancient and modern sediment of Northeastern Bering sea. Mar. GeoL, 18, 91-104.
Klien, D. H.& Goldberg, E. D. (1970). Mercury in the marine environment. Environ. Sci. Technol., 4,765-768. Knauer, G. A. & Martin, J. H. (1972). Mercury in a marine pelagic food chain, LimnoL Oceanog. 17,868-872. Kojima, K. (1973). Summary of recent studies in Japan on methylmercury poisoning. TbxicoL, 1,43-62. Krauskopf, K. B. (1965). Factors controlling the concentrations of thirteen rare metals in seawater. Geochim. Cosmochim. Acta, 9, 1-32B. Lindberg, S. E., Andren, A. W. & Harriss, R. C. (1975). Geochemistry of mercury in the estuarine environment. Estuar. Res., 1, 64-107. Stainton, M. P. (1971). Syringe procedure for transfer of nanogram quantities of mercury vapor for flameless atomic absorption spectrophotometry. AnaL Chem., 43,625-627. Trefry, J. H., Sims, R. R. Jr. & Presley, B. J. (1975). In ShellDredging and its Influence on The Gulf Coast Environment. A. H. Bouma (ed.). Houston, Texas: Gulf.
Effects of Oil Pollution on .Breeding Grey Seals Marine m a m m a l s are probably frequently exposed to floating oil but little is k n o w n about the effect oil pollution has on them. Oil stranded on the shore in Pembrokeshire, West Wales in September 1974 coincided with the start of the Grey Seal breeding season there. Observations have been made on the effect the oil had on the newborn pups and their mothers. Oil was first r e p o r t e d f r o m the a r e a b e t w e e n F r e s h w a t e r W e s t a n d W h i t e s a n d s Bay, D y f e d , d u r i n g the n i g h t o f 8
•
Y :~
.St Oovids
Romey#7 ? ~Islond ~
St Anne's Head 0 ,
1
2
3
,
,
~
5
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Fig. 1 Areas known to be affected by oil pollution in September 1974.
S e p t e m b e r 1974, f o l l o w i n g a week o f severe s o u t h a n d s o u t h - w e s t e r l y gales. M o r e oil c a m e a s h o r e o n S k o m e r I s l a n d , N a t i o n a l N a t u r e Reserve, a n d at several m a i n l a n d sites d u r i n g the next few d a y s (Fig. 1). N o n e o f the b e a c h e s was h e a v i l y p o l l u t e d a l t h o u g h the d e g r e e o f oiling v a r i e d f r o m b e a c h to b e a c h . T h e oil which c a m e a s h o r e o n the S k o m e r b e a c h e s a r r i v e d in s m a l l p a t c h e s a b o u t 1 m a c r o s s on the t i d e f r o m the n o r t h . T h e p a t c h e s o f oil, w h i c h were fluid a n d fresh at first, collected in s h e l t e r e d b a y s a n d caves with a s o u t h - w e s t aspect, a n d w e a t h e r e d q u i c k l y , b e c o m i n g d a r k b r o w n a n d t a r r y . N o i n f o r m a t i o n was a v a i l a b l e or has since b e e n d i s c o v e r e d , o n the s o u r c e o f the oil. L i t t l e a t t e m p t was m a d e to clean b e a c h e s o n S k o m e r , b u t m o s t s a n d y b e a c h e s on the m a i n l a n d were c l e a n e d b y m e c h a n i c a l m e a n s , a b o u t 260 t o n s o f oil a n d b e a c h m a t e r i a l b e i n g r e m o v e d , a n d in a few cases s o m e c l e a n i n g was d o n e using a l o w - t o x i c i t y c h e m i c a l d i s p e r s a n t . T h e oiling c o i n c i d e d with the s t a r t o f the G r e y seal ( H a l i c h o e r u s grypus) b r e e d i n g s e a s o n in s o u t h - w e s t W a l e s . A d u l t s were a s s e m b l i n g o n the b r e e d i n g b e a c h e s a n d p u p s b o r n in the e a r l y p a r t o f the s e a s o n were a f f e c t e d b y the oil. P r e v i o u s oil p o l l u t i o n i n c i d e n t s i n v o l v i n g seals a r e few a n d r e c o r d s m e a g r e . T h e largest i n c i d e n t , the S a n t a B a r b a r a C h a n n e l oil spill, a f f e c t e d w e a n e d E l e p h a n t seal p u p s , M i r o u n g a angustirostris, a n d n u r s i n g C a l i f o r n i a sea lions, Z a l o p h u s californianus (Le B o e u f , a n d B r o w n e l l & Le B o e u f , in S t r a u g h a n , 1971). N o d e l e t e r i o u s effects o f oil o n E l e p h a n t seal p u p s were f o u n d , a n d it was c o n c l u d e d t h a t c o n t a m i n a t i o n d i d n o t h a v e a m a r k e d effect o n sea lion p u p m o r t a l i t y . V a n H a a f t e n (1973) f o u n d C o m m o n seals ( P h o c a vitulina) in D u t c h waters with p a t c h e s o f oil on their fur, b e l o w which were i n f l a m e d a r e a s o f skin. A s m a l l n u m b e r o f a n i m a l s h a d s k i n lesions a s s o c i a t e d with oil p a t c h e s , b u t he n o t e d t h a t t h e r e were l a r g e r n u m b e r s o f seals w h i c h h a d lesions b u t n o sign o f o i l p o l l u t i o n . Davies (1949) m e n t i o n s oiled G r e y seal p u p s o n R a m s e y I s l a n d w h i c h were o n the w h o l e u n a f f e c t e d b y t h e i r thick c o a t i n g o f fuel oil, a l t h o u g h t w o d i e d t h r o u g h b e i n g w a s h e d o f f beaches. I n e a r l y N o v e m b e r 1969 f o u r t e e n p u p s were w a s h e d up oiled a n d 115
Marine Pollution Bulletin dead on the N o r t h Dyfed coast, (Nature in Wales, 1970). No information is available on whether oil caused these pup deaths. Because the 1974 incident was the first time an oil spill affecting seals in Great Britain had been reported, experiments in cleaning pups were undertaken and one o f us (J.E.D.) m a d e detailed records o f the progress and behaviour of oiled animals on Skomer Island. In addition, m a n y o f the South Wales breeding sites were visited that a u t u m n during a Grey seal population survey o f the Welsh coast (Anderson, in prep.), and the n u m b e r o f oiled pups seen during single visits to each breeding site was recorded.
Numbers of Oiled Seals On Skomer Island three pups were born before the first oil came ashore, but a further ten appeared in the subsequent 48 h. Eleven of these pups were oiled and a further 14 became affected later in the season. Thus, of the 62 pups born by 30 October, 40070 were either wholly or partly oiled. Ten cows were heavily oiled at the beginning and an additional 13 partly oiled as the season progressed; four oiled bulls were seen. The single visits to Ramsey Island and the mainland f r o m St Davids to Fishguard between 27 September and I October 1974 revealed fewer examples of heavily oiled seals and the percentages o f oiled animals were lower. The n u m b e r o f oiled adults could not be recorded accurately during these single visits. Table 1 shows these counts together with those for Skomer for 29 September for comparison. On Skomer Island, those animals which were completely coated in thick oil could have become contaminated through contact with floating oil at sea, or oil accumulated thickly in caves. There was insufficient oil on the breeding beaches to account for the degree of oiling o f most cows and pups, but it is possible that cows which initially pupped in severely polluted caves subsequently moved to open beaches. Those animals which were oiled on the ventral surface only would p r o b a b l y have acquired the oil through hauling out on polluted beaches. It is thought that the majority of pups became oiled through contact with their mothers or f r o m oil transferred to the beach by cows. However, as quite young pups were occasionally seen swimming in the shallows, some of the badly oiled pups, which were found soon after the oil first appeared, m a y have collected floating oil directly.
feasibility o f cleaning pups and to m o n i t o r any effects on behaviour. Seven o f the badly oiled pups were selected and four separate substances were tried. 1. Washing-up liquid (Winfield) applied undiluted and rinsed with either hot or cold water was found to be ineffective. 2. ' S w a r f e g a ' was rubbed into the pelt and was rinsed o f f with either hot or cold water. This was effective in removing the oil but caused distress in contact with the eyes. Trials were therefore discontinued because insufficient was known a b o u t possible side effects of 'Swarfega'. 3. 'Saroul' detergent was applied undiluted and rinsed o f f with sea water. This was effective in removing oil, but took a long time to apply. 4. BP 1100X was sprayed on using a knapsack sprayer and was rubbed into the oil; the pups were then rinsed in sea water. Three pups were successfully cleaned by this method. A fourth pup which was wet f r o m swimming in the shallows was sprayed with BP l l00X and then released into the sea. This had some cleaning effect although oil on the coat which had weathered was not removed. Thus, five pups were cleaned successfully, but each of these became recontaminated to varying degrees through contact with their oiled mothers which could not be cleaned. One of these pups was completely recoated with thick weathered oil and a second attempt to clean it with BP l l00X met with much reduced success. It was concluded that BP 1100X was only effective on fresh oil. No further cleaning was attempted and it was concluded that there was little justification in cleaning pups unless all sources of recontamination could also be treated.
Growth Rate and Survival of Pups Twelve unoiled and nine oiled pups were weighed at three day intervals. The average birth weights, peak weights, time to reach peak weight and growth rate per day are shown in Table 2. There are insufficient data on birth weights to test for any difference between the two groups, but the average peak weights were significantly different (t-- 3.07, P <0.01). The average times taken to reach peak weights were not significantly different (P > 0.05, by M a n n - W h i t n e y test, Snedecor & Cochran, 1971). Because o f the variance within the growth rate data, no tests of significance were attempted on the average growth rates per day. C o m p a r a b l e figures for the Farne Islands (Coulson & Hickling, 1964) and North
Cleaning Trials Because it was not known whether oil would have a directly deleterious effect on pups or adults, it was decided that an attempt should be m a d e to test the
TABLE 2 Weights and growth rates of Skomer pups with comparative data from elsewhere. Average birth weight (lbs)
TABLE 1 Numbers of oiled pups. Area
Date (1974)
Total pups counted
Ramsey 27 Sept. 153 Island StDavids-30Sept.-1 Oct. 118 Fishguard Skomer Island 29 Sept. 22 116
Number of oiled pups
Percentage
11
7
25 l1
Average Averagetime Average peak to reach growth rate weight peak weight per day (lbs) (days) (lbs)
SKOMER
Oiled pups Unoiled pups
27.5 26.2
60.9 78.2
14.9 15.6
2.24 3.13
21
FARNES* NORTH RONA§
31.9 33.8
90-100 87.6
17 --
4.0 --
50
*Coulson & Hickling (1964). §Boyd& Campbell (1971).
oiled
Volume 7/Number 6/June 1976 TABLE 3 Mortality of Skomer pups. Total born
Oiled Unoiled
25 37
Died (670) Disappeared Later onbeaches from beaches recoveries
5 (20%) 11 (30%)
4 4*
1 2* + 2
TABLE 4 Causes of death. Total dead
10 17
Percent mortality
40 46
*Two pups were subsequently recovered. R o n a (Boyd & C a m p b e l l , 1971) are s h o w n in T a b l e 2. T h e S k o m e r figures are lower t h a n those for elsewhere, a n d m a y p e r h a p s be characteristic o f the W e l s h Grey seal population. T h e thick tarry oil affecting the n a t a l coat had a b i n d i n g effect, a n d a l t h o u g h the fur b e g a n to loosen a r o u n d the head a n d flippers as n o r m a l , it was n o t u n t i l it was quite loose a r o u n d the p u p that it c a m e away. This was because the oil held the fur together u n t i l a hole was r u b b e d in it by the p u p ' s m o v e m e n t s so t h a t the m a t b e g a n to b r e a k u p a n d the whole coat was shed very quickly. T h e m o u l t e d pups were a l m o s t clean b u t some picked u p oil f r o m their shed coats if they stayed i n the same place after m o u l t i n g . T h e other p u p s affected b y weathered oil, which did n o t have a clogging or b i n d i n g effect in h o l d i n g the coat together, m o u l t e d n o r m a l l y . M o r t a l i t y O f the 62 pups b o r n b e f o r e 30 O c t o b e r , 16 were s t i l l - b o r n or died b e f o r e w e a n i n g a n d 8 d i s a p p e a r e d b e f o r e w e a n i n g whilst in a weak c o n d i t i o n a n d were t h o u g h t u n l i k e l y to survive. Five tagged p u p s were s u b s e q u e n t l y recovered, two f r o m n e a r b y Welsh m a i n l a n d beaches a n d o n e f r o m Dorset. T w o o f those pups which d i s a p p e a r e d were f o u n d in C o W e x f o r d , I r e l a n d a n d C o r n w a l l . T h e m o r t a l i t y in oiled a n d u n o i l e d pups is s h o w n in T a b l e 3. T h e p e r c e n t a g e m o r t a l i t y o f each g r o u p was very high c o m p a r e d with other sites such as the F a r n e I s l a n d s ( C o u l s o n & H i c k l i n g , 1964). P r e v i o u s d a t a o n m o r t a l i t y is n o t available for S k o m e r , b u t Davies (1949) suggests a figure o f 15-20070 for n e a r b y R a m s e y I s l a n d . T h e high m o r t a l i t y in 1974 m a y reflect the d i s t u r b a n c e which was i m p o s s i b l e to avoid whilst investigating the oiling
Moult
Disappeared (assumed dead) Still-born Drowned in fishing net or washed up dead Underweight, starvation, exposure Cause unknown Infection Encased in oil, washed off beach
Oiled
Unoiled
4 --1 1 2 2
2 4 4 3 3 1 --
i n c i d e n t . M o r t a l i t y o n the beaches a n d total m o r t a l i t y were b o t h slightly higher in the u n o i l e d g r o u p , i n d i c a t i n g that oiling was n o t a direct cause of death, a l t h o u g h the s a m p l e was too small to e n a b l e firm c o n c l u s i o n s to be d r a w n . H o w e v e r , the lower peak weights (Table 2) o f oiled seals m u s t have reduced the survival chances o f those a n i m a l s : B o n n e r & H i c k l i n g (1971) suggested that pups which failed to reach 65 lbs by the time their m o t h e r s deserted t h e m w o u l d be u n l i k e l y to survive their first winter. The n u m b e r o f s u b s e q u e n t recoveries was too low to give f u r t h e r i n f o r m a t i o n o n this p o i n t . Causes o f d e a t h are s u m m a r i s e d in T a b l e 4. Six o f the dead pups were s u b m i t t e d for post m o r t e m analysis; the analyses showed that n o n e o f the pups h a d ingested oil, thus s u p p o r t i n g the a b o v e c o n c l u s i o n that oiling was n o t a direct cause of death. T h e only deaths which c o u l d be a t t r i b u t e d directly to oil, were those o f two p u p s , encased in oil so that they were u n a b l e to swim a n d thus were d r o w n e d w h e n washed o f f the beach.
Effects on Behaviour O b s e r v a t i o n s m a d e d u r i n g regular c o u n t s indicated that cows a p p e a r e d to locate a n d feed their pups successfully w h e t h e r they were oiled or clean, a l t h o u g h three i n c i d e n t s were recorded in which o n e oiled cow fed two p u p s s i m u l t a n e o u s l y . T o investigate f u r t h e r the effects o f oil o n b e h a v i o u r a n d p u p d e v e l o p m e n t , o b s e r v a t i o n s were m a d e o n a g r o u p o f oiled a n d u n o i l e d seals in S o u t h Castle Bay, one o f the m a i n b r e e d i n g
TABLE 5 Summary of behavioural observations. Cow-pup pair Cow's condition Pup's condition Time under observation Cow: % of time spent on beach Time spent sleepingon beach Number of visits to pup Number of feeds Average length o f feeds Average interval between feeds No. of times cow showed aggression to pup-other cow-bull Interval between aggressiveacts
A Clean Clean 50 V2h 31.9% 2 h 16 min 18 12 9 Vz min 4 h 34 min 1/ 12/4
B Oiled Oiled 50 V2h 47.5% 3 h 25 min 16 12 7 V2min 3 h 30 min 3/15/3
C Clean Clean 42 ~/zh 62.1% 6 h 10 min 14 6 15 min 4 h 58 min 2/27/1
D Clean Oiled 50 Vz h 47.3°7o 5 h 45 min 18 11§ 10 min 5 h 9 min 0/16/3
E Oiled Oiled 50 '/2 h 26.0% 4 h 25 min 7 I 15 min -0/7/0
3 h 8 min
2 h 31 min
1 h 22 min
2 h 40 min
6 h 17 min
Pup: Date of birth Sex Weight on day of birth Peak weight Average weight gain per day Age when peak weight reached Fate of pup
10/9/74 M ? 64 Ibs 2.4 lbs 14 days Unknown
13/9/74 M 35 lbs* 67 lbs 2.8 lbs 14 days Unknown
21/9/74 F 18 lbs 28 lbs 1.6 lbs 6 days Lost 1/10/74, found dead in Cornwall in 2 weeks
14/9/74 M ? 53 lbs I. 1lbs 11 days Died 30/9/74 cause unknown
18/9/74 M 35 lbs* 65 lbs 2.5 lbs 12 days Unknown
*Pup was probably fed once or twice in the interval between birth and first weighing. §Six feeds to pup D and five to pup E. 117
Marine Pollution Bulletin
beaches on the island, from 1030-1930 h for six consecutive days. A permanent hide, situated so that access was possible without causing any disturbance to the seals, was used. Records were kept of all the activities of five mother-pup pairs. A summary of the quantitative information is given in Table 5. One oiled (B) and one unoiled (A) mother-pup pair progressed normally, one unoiled (C) failed and two oiled pairs (D and E) showed an example of adoptive suckling. Oil in itself did not appear to preclude normal mother-pup relations, but because cows identify their pups by smell (Fogden, 1971) the covering of oil on pups D and E may have confused cow D so that she could not distinguish between them. However, Fogden recorded adoptive suckling in uncontaminated animals and concluded that its occurrence was a function of human disturbance.
Conclusions Although we have concluded from a very small sample that the behaviour of oiled seals did not appear to differ from that of normal seals, peak weights of oiled pups were significantly lower than those for unoiled pups. Since there was no evidence from post mortem analyses of a directly deleterious effect of oil, there must have been some other interference with the mother-pup relationship. Both oiled and unoiled seals were disturbed by weighing and tagging operations, but the oiled pups were certainly more disturbed than unoiled pups at the beginning of the season by cleaning operations, veterinary inspection and visiting observers. The lower peak weights may partly reflect the greater disturbance suffered by oiled pups. There was no difference between the mortality of oiled and unoiled pups on the beaches, but insufficient information is available on mortality at sea to study the survival of pups with low weaning weights. To draw more positive conclusions than is possible from this study would require a larger sample of animals. We conclude from the cleaning trials that unless all
Waste Heat in the Aquatic Environment National Research Council Canada. (1976) Waste Heat in the Aquatic Environment. Ottawa, NRCC. Price: $1 .oo. It is probable that the Canadian electricity generating 118
sources of recontamination can also be treated, there is little point in cleaning individual animals. The resultant disturbance is probably more damaging to a pup's chances of survival than the oil itself. We should like to thank M. Cullen, H. Davis and S. B. Evans for assistance with fieldwork, and J. Horwood for help with the statistical analyses. The MAFF Veterinary Investigation Service carried out the post mortem analyses. The Nature Conservancy Council kindly provided financial assistance which enabled J. E. Davis to complete this study. We are also grateful to colleagues for assistance in preparing the manuscript and for helpful comments.
JOHN E. DAVIS
West Wales Naturalist Trust 4 Victoria Place Haverfordwest, Dyfed U.K. SHEILA S. ANDERSON
Seals Research Division Institute for Marine Environmental Research c/ o Fisheries laboratory Lowestoft, Suffolk, U.K. Anderson, Sheila S. (in prep). The Grey seal in Wales. Bonnet, W. N. & Hickling, Grace (1971). The Grey seals of the Farne Islands. Trans. nat. Hist. Soc. Northumb. N.S., 17, 141-162. Boyd, J. M. & Campbell, R. N. (1971). The Grey seal (Halichoerus grypus) at North Rona, 1959-1968. J. Zool. Lond., 164,469-512. Coulson, J. C. & Hickling, G. (1964). The breeding biology of the Grey seal, Halichoerus grypus (Fab), on the Farne Islands, Northumberland. J. Anon. Ecol., 33,485-512. Davies, J. L. (1949). Observations on the Grey seal (Halichoerus grypus) at Ramsey Island, Pembrokeshire. Proc. Zool. Soc. Lond., 119,673-692. Fogden, S. C. L. (1971). Mother-young behaviour at Grey seal breeding beaches. J. Zool. Lond., 164, 61-92. Nature in Wales. (1970). Mammals, 12(2), 110. Snedecor, G. W. & Cochran, W. G. (1971). StatisticalMethods. Iowa, USA: The Iowa State University Press. Straughan, D. (1971). Biological and Oceanographical Survey o f the Santa Barbara Oil Spill, 1969-70. Vol. I. Biology and Bacteriology. Spec. Publ. Allan Hancock Foundation. (Sea Grant Publ. No. 2.) Van Haaften, J. L. (1973). Die Bewirtschaftung von Seehunden in den Niederlanden. Bietriige zur Jagd- und Wildforschung, 8, 345-349.
capacity will increase by at least ten times within the next 25 years. A large part of this increase will be provided by thermal electricity generating plants (either nuclear or fossil-fueled), generally operating at energy efficiencies between 30-40o7o. The energy wasted in these plants is for the most part discharged directly to surface waters as a stream of heated water about 5-10°C higher in temperature. Since they will need large quantities of cool
Klien, D. H.& Goldberg, E. D. (1970). Mercury in the marine environment. Environ. Sci. Technol., 4,765-768. Knauer, G. A. & Martin, J. H. (1972). Mercury in a marine pelagic food chain, LimnoL Oceanog. 17,868-872. Kojima, K. (1973). Summary of recent studies in Japan on methylmercury poisoning. TbxicoL, 1,43-62. Krauskopf, K. B. (1965). Factors controlling the concentrations of thirteen rare metals in seawater. Geochim. Cosmochim. Acta, 9, 1-32B. Lindberg, S. E., Andren, A. W. & Harriss, R. C. (1975). Geochemistry of mercury in the estuarine environment. Estuar. Res., 1, 64-107. Stainton, M. P. (1971). Syringe procedure for transfer of nanogram quantities of mercury vapor for flameless atomic absorption spectrophotometry. AnaL Chem., 43,625-627. Trefry, J. H., Sims, R. R. Jr. & Presley, B. J. (1975). In ShellDredging and its Influence on The Gulf Coast Environment. A. H. Bouma (ed.). Houston, Texas: Gulf.
Effects of Oil Pollution on .Breeding Grey Seals Marine m a m m a l s are probably frequently exposed to floating oil but little is k n o w n about the effect oil pollution has on them. Oil stranded on the shore in Pembrokeshire, West Wales in September 1974 coincided with the start of the Grey Seal breeding season there. Observations have been made on the effect the oil had on the newborn pups and their mothers. Oil was first r e p o r t e d f r o m the a r e a b e t w e e n F r e s h w a t e r W e s t a n d W h i t e s a n d s Bay, D y f e d , d u r i n g the n i g h t o f 8
•
Y :~
.St Oovids
Romey#7 ? ~Islond ~
St Anne's Head 0 ,
1
2
3
,
,
~
5
"Lx...._ ''--'-j Freshw°}.e/~i~\ I I
Fig. 1 Areas known to be affected by oil pollution in September 1974.
S e p t e m b e r 1974, f o l l o w i n g a week o f severe s o u t h a n d s o u t h - w e s t e r l y gales. M o r e oil c a m e a s h o r e o n S k o m e r I s l a n d , N a t i o n a l N a t u r e Reserve, a n d at several m a i n l a n d sites d u r i n g the next few d a y s (Fig. 1). N o n e o f the b e a c h e s was h e a v i l y p o l l u t e d a l t h o u g h the d e g r e e o f oiling v a r i e d f r o m b e a c h to b e a c h . T h e oil which c a m e a s h o r e o n the S k o m e r b e a c h e s a r r i v e d in s m a l l p a t c h e s a b o u t 1 m a c r o s s on the t i d e f r o m the n o r t h . T h e p a t c h e s o f oil, w h i c h were fluid a n d fresh at first, collected in s h e l t e r e d b a y s a n d caves with a s o u t h - w e s t aspect, a n d w e a t h e r e d q u i c k l y , b e c o m i n g d a r k b r o w n a n d t a r r y . N o i n f o r m a t i o n was a v a i l a b l e or has since b e e n d i s c o v e r e d , o n the s o u r c e o f the oil. L i t t l e a t t e m p t was m a d e to clean b e a c h e s o n S k o m e r , b u t m o s t s a n d y b e a c h e s on the m a i n l a n d were c l e a n e d b y m e c h a n i c a l m e a n s , a b o u t 260 t o n s o f oil a n d b e a c h m a t e r i a l b e i n g r e m o v e d , a n d in a few cases s o m e c l e a n i n g was d o n e using a l o w - t o x i c i t y c h e m i c a l d i s p e r s a n t . T h e oiling c o i n c i d e d with the s t a r t o f the G r e y seal ( H a l i c h o e r u s grypus) b r e e d i n g s e a s o n in s o u t h - w e s t W a l e s . A d u l t s were a s s e m b l i n g o n the b r e e d i n g b e a c h e s a n d p u p s b o r n in the e a r l y p a r t o f the s e a s o n were a f f e c t e d b y the oil. P r e v i o u s oil p o l l u t i o n i n c i d e n t s i n v o l v i n g seals a r e few a n d r e c o r d s m e a g r e . T h e largest i n c i d e n t , the S a n t a B a r b a r a C h a n n e l oil spill, a f f e c t e d w e a n e d E l e p h a n t seal p u p s , M i r o u n g a angustirostris, a n d n u r s i n g C a l i f o r n i a sea lions, Z a l o p h u s californianus (Le B o e u f , a n d B r o w n e l l & Le B o e u f , in S t r a u g h a n , 1971). N o d e l e t e r i o u s effects o f oil o n E l e p h a n t seal p u p s were f o u n d , a n d it was c o n c l u d e d t h a t c o n t a m i n a t i o n d i d n o t h a v e a m a r k e d effect o n sea lion p u p m o r t a l i t y . V a n H a a f t e n (1973) f o u n d C o m m o n seals ( P h o c a vitulina) in D u t c h waters with p a t c h e s o f oil on their fur, b e l o w which were i n f l a m e d a r e a s o f skin. A s m a l l n u m b e r o f a n i m a l s h a d s k i n lesions a s s o c i a t e d with oil p a t c h e s , b u t he n o t e d t h a t t h e r e were l a r g e r n u m b e r s o f seals w h i c h h a d lesions b u t n o sign o f o i l p o l l u t i o n . Davies (1949) m e n t i o n s oiled G r e y seal p u p s o n R a m s e y I s l a n d w h i c h were o n the w h o l e u n a f f e c t e d b y t h e i r thick c o a t i n g o f fuel oil, a l t h o u g h t w o d i e d t h r o u g h b e i n g w a s h e d o f f beaches. I n e a r l y N o v e m b e r 1969 f o u r t e e n p u p s were w a s h e d up oiled a n d 115
Marine Pollution Bulletin dead on the N o r t h Dyfed coast, (Nature in Wales, 1970). No information is available on whether oil caused these pup deaths. Because the 1974 incident was the first time an oil spill affecting seals in Great Britain had been reported, experiments in cleaning pups were undertaken and one o f us (J.E.D.) m a d e detailed records o f the progress and behaviour of oiled animals on Skomer Island. In addition, m a n y o f the South Wales breeding sites were visited that a u t u m n during a Grey seal population survey o f the Welsh coast (Anderson, in prep.), and the n u m b e r o f oiled pups seen during single visits to each breeding site was recorded.
Numbers of Oiled Seals On Skomer Island three pups were born before the first oil came ashore, but a further ten appeared in the subsequent 48 h. Eleven of these pups were oiled and a further 14 became affected later in the season. Thus, of the 62 pups born by 30 October, 40070 were either wholly or partly oiled. Ten cows were heavily oiled at the beginning and an additional 13 partly oiled as the season progressed; four oiled bulls were seen. The single visits to Ramsey Island and the mainland f r o m St Davids to Fishguard between 27 September and I October 1974 revealed fewer examples of heavily oiled seals and the percentages o f oiled animals were lower. The n u m b e r o f oiled adults could not be recorded accurately during these single visits. Table 1 shows these counts together with those for Skomer for 29 September for comparison. On Skomer Island, those animals which were completely coated in thick oil could have become contaminated through contact with floating oil at sea, or oil accumulated thickly in caves. There was insufficient oil on the breeding beaches to account for the degree of oiling o f most cows and pups, but it is possible that cows which initially pupped in severely polluted caves subsequently moved to open beaches. Those animals which were oiled on the ventral surface only would p r o b a b l y have acquired the oil through hauling out on polluted beaches. It is thought that the majority of pups became oiled through contact with their mothers or f r o m oil transferred to the beach by cows. However, as quite young pups were occasionally seen swimming in the shallows, some of the badly oiled pups, which were found soon after the oil first appeared, m a y have collected floating oil directly.
feasibility o f cleaning pups and to m o n i t o r any effects on behaviour. Seven o f the badly oiled pups were selected and four separate substances were tried. 1. Washing-up liquid (Winfield) applied undiluted and rinsed with either hot or cold water was found to be ineffective. 2. ' S w a r f e g a ' was rubbed into the pelt and was rinsed o f f with either hot or cold water. This was effective in removing the oil but caused distress in contact with the eyes. Trials were therefore discontinued because insufficient was known a b o u t possible side effects of 'Swarfega'. 3. 'Saroul' detergent was applied undiluted and rinsed o f f with sea water. This was effective in removing oil, but took a long time to apply. 4. BP 1100X was sprayed on using a knapsack sprayer and was rubbed into the oil; the pups were then rinsed in sea water. Three pups were successfully cleaned by this method. A fourth pup which was wet f r o m swimming in the shallows was sprayed with BP l l00X and then released into the sea. This had some cleaning effect although oil on the coat which had weathered was not removed. Thus, five pups were cleaned successfully, but each of these became recontaminated to varying degrees through contact with their oiled mothers which could not be cleaned. One of these pups was completely recoated with thick weathered oil and a second attempt to clean it with BP l l00X met with much reduced success. It was concluded that BP 1100X was only effective on fresh oil. No further cleaning was attempted and it was concluded that there was little justification in cleaning pups unless all sources of recontamination could also be treated.
Growth Rate and Survival of Pups Twelve unoiled and nine oiled pups were weighed at three day intervals. The average birth weights, peak weights, time to reach peak weight and growth rate per day are shown in Table 2. There are insufficient data on birth weights to test for any difference between the two groups, but the average peak weights were significantly different (t-- 3.07, P <0.01). The average times taken to reach peak weights were not significantly different (P > 0.05, by M a n n - W h i t n e y test, Snedecor & Cochran, 1971). Because o f the variance within the growth rate data, no tests of significance were attempted on the average growth rates per day. C o m p a r a b l e figures for the Farne Islands (Coulson & Hickling, 1964) and North
Cleaning Trials Because it was not known whether oil would have a directly deleterious effect on pups or adults, it was decided that an attempt should be m a d e to test the
TABLE 2 Weights and growth rates of Skomer pups with comparative data from elsewhere. Average birth weight (lbs)
TABLE 1 Numbers of oiled pups. Area
Date (1974)
Total pups counted
Ramsey 27 Sept. 153 Island StDavids-30Sept.-1 Oct. 118 Fishguard Skomer Island 29 Sept. 22 116
Number of oiled pups
Percentage
11
7
25 l1
Average Averagetime Average peak to reach growth rate weight peak weight per day (lbs) (days) (lbs)
SKOMER
Oiled pups Unoiled pups
27.5 26.2
60.9 78.2
14.9 15.6
2.24 3.13
21
FARNES* NORTH RONA§
31.9 33.8
90-100 87.6
17 --
4.0 --
50
*Coulson & Hickling (1964). §Boyd& Campbell (1971).
oiled
Volume 7/Number 6/June 1976 TABLE 3 Mortality of Skomer pups. Total born
Oiled Unoiled
25 37
Died (670) Disappeared Later onbeaches from beaches recoveries
5 (20%) 11 (30%)
4 4*
1 2* + 2
TABLE 4 Causes of death. Total dead
10 17
Percent mortality
40 46
*Two pups were subsequently recovered. R o n a (Boyd & C a m p b e l l , 1971) are s h o w n in T a b l e 2. T h e S k o m e r figures are lower t h a n those for elsewhere, a n d m a y p e r h a p s be characteristic o f the W e l s h Grey seal population. T h e thick tarry oil affecting the n a t a l coat had a b i n d i n g effect, a n d a l t h o u g h the fur b e g a n to loosen a r o u n d the head a n d flippers as n o r m a l , it was n o t u n t i l it was quite loose a r o u n d the p u p that it c a m e away. This was because the oil held the fur together u n t i l a hole was r u b b e d in it by the p u p ' s m o v e m e n t s so t h a t the m a t b e g a n to b r e a k u p a n d the whole coat was shed very quickly. T h e m o u l t e d pups were a l m o s t clean b u t some picked u p oil f r o m their shed coats if they stayed i n the same place after m o u l t i n g . T h e other p u p s affected b y weathered oil, which did n o t have a clogging or b i n d i n g effect in h o l d i n g the coat together, m o u l t e d n o r m a l l y . M o r t a l i t y O f the 62 pups b o r n b e f o r e 30 O c t o b e r , 16 were s t i l l - b o r n or died b e f o r e w e a n i n g a n d 8 d i s a p p e a r e d b e f o r e w e a n i n g whilst in a weak c o n d i t i o n a n d were t h o u g h t u n l i k e l y to survive. Five tagged p u p s were s u b s e q u e n t l y recovered, two f r o m n e a r b y Welsh m a i n l a n d beaches a n d o n e f r o m Dorset. T w o o f those pups which d i s a p p e a r e d were f o u n d in C o W e x f o r d , I r e l a n d a n d C o r n w a l l . T h e m o r t a l i t y in oiled a n d u n o i l e d pups is s h o w n in T a b l e 3. T h e p e r c e n t a g e m o r t a l i t y o f each g r o u p was very high c o m p a r e d with other sites such as the F a r n e I s l a n d s ( C o u l s o n & H i c k l i n g , 1964). P r e v i o u s d a t a o n m o r t a l i t y is n o t available for S k o m e r , b u t Davies (1949) suggests a figure o f 15-20070 for n e a r b y R a m s e y I s l a n d . T h e high m o r t a l i t y in 1974 m a y reflect the d i s t u r b a n c e which was i m p o s s i b l e to avoid whilst investigating the oiling
Moult
Disappeared (assumed dead) Still-born Drowned in fishing net or washed up dead Underweight, starvation, exposure Cause unknown Infection Encased in oil, washed off beach
Oiled
Unoiled
4 --1 1 2 2
2 4 4 3 3 1 --
i n c i d e n t . M o r t a l i t y o n the beaches a n d total m o r t a l i t y were b o t h slightly higher in the u n o i l e d g r o u p , i n d i c a t i n g that oiling was n o t a direct cause of death, a l t h o u g h the s a m p l e was too small to e n a b l e firm c o n c l u s i o n s to be d r a w n . H o w e v e r , the lower peak weights (Table 2) o f oiled seals m u s t have reduced the survival chances o f those a n i m a l s : B o n n e r & H i c k l i n g (1971) suggested that pups which failed to reach 65 lbs by the time their m o t h e r s deserted t h e m w o u l d be u n l i k e l y to survive their first winter. The n u m b e r o f s u b s e q u e n t recoveries was too low to give f u r t h e r i n f o r m a t i o n o n this p o i n t . Causes o f d e a t h are s u m m a r i s e d in T a b l e 4. Six o f the dead pups were s u b m i t t e d for post m o r t e m analysis; the analyses showed that n o n e o f the pups h a d ingested oil, thus s u p p o r t i n g the a b o v e c o n c l u s i o n that oiling was n o t a direct cause of death. T h e only deaths which c o u l d be a t t r i b u t e d directly to oil, were those o f two p u p s , encased in oil so that they were u n a b l e to swim a n d thus were d r o w n e d w h e n washed o f f the beach.
Effects on Behaviour O b s e r v a t i o n s m a d e d u r i n g regular c o u n t s indicated that cows a p p e a r e d to locate a n d feed their pups successfully w h e t h e r they were oiled or clean, a l t h o u g h three i n c i d e n t s were recorded in which o n e oiled cow fed two p u p s s i m u l t a n e o u s l y . T o investigate f u r t h e r the effects o f oil o n b e h a v i o u r a n d p u p d e v e l o p m e n t , o b s e r v a t i o n s were m a d e o n a g r o u p o f oiled a n d u n o i l e d seals in S o u t h Castle Bay, one o f the m a i n b r e e d i n g
TABLE 5 Summary of behavioural observations. Cow-pup pair Cow's condition Pup's condition Time under observation Cow: % of time spent on beach Time spent sleepingon beach Number of visits to pup Number of feeds Average length o f feeds Average interval between feeds No. of times cow showed aggression to pup-other cow-bull Interval between aggressiveacts
A Clean Clean 50 V2h 31.9% 2 h 16 min 18 12 9 Vz min 4 h 34 min 1/ 12/4
B Oiled Oiled 50 V2h 47.5% 3 h 25 min 16 12 7 V2min 3 h 30 min 3/15/3
C Clean Clean 42 ~/zh 62.1% 6 h 10 min 14 6 15 min 4 h 58 min 2/27/1
D Clean Oiled 50 Vz h 47.3°7o 5 h 45 min 18 11§ 10 min 5 h 9 min 0/16/3
E Oiled Oiled 50 '/2 h 26.0% 4 h 25 min 7 I 15 min -0/7/0
3 h 8 min
2 h 31 min
1 h 22 min
2 h 40 min
6 h 17 min
Pup: Date of birth Sex Weight on day of birth Peak weight Average weight gain per day Age when peak weight reached Fate of pup
10/9/74 M ? 64 Ibs 2.4 lbs 14 days Unknown
13/9/74 M 35 lbs* 67 lbs 2.8 lbs 14 days Unknown
21/9/74 F 18 lbs 28 lbs 1.6 lbs 6 days Lost 1/10/74, found dead in Cornwall in 2 weeks
14/9/74 M ? 53 lbs I. 1lbs 11 days Died 30/9/74 cause unknown
18/9/74 M 35 lbs* 65 lbs 2.5 lbs 12 days Unknown
*Pup was probably fed once or twice in the interval between birth and first weighing. §Six feeds to pup D and five to pup E. 117
Marine Pollution Bulletin
beaches on the island, from 1030-1930 h for six consecutive days. A permanent hide, situated so that access was possible without causing any disturbance to the seals, was used. Records were kept of all the activities of five mother-pup pairs. A summary of the quantitative information is given in Table 5. One oiled (B) and one unoiled (A) mother-pup pair progressed normally, one unoiled (C) failed and two oiled pairs (D and E) showed an example of adoptive suckling. Oil in itself did not appear to preclude normal mother-pup relations, but because cows identify their pups by smell (Fogden, 1971) the covering of oil on pups D and E may have confused cow D so that she could not distinguish between them. However, Fogden recorded adoptive suckling in uncontaminated animals and concluded that its occurrence was a function of human disturbance.
Conclusions Although we have concluded from a very small sample that the behaviour of oiled seals did not appear to differ from that of normal seals, peak weights of oiled pups were significantly lower than those for unoiled pups. Since there was no evidence from post mortem analyses of a directly deleterious effect of oil, there must have been some other interference with the mother-pup relationship. Both oiled and unoiled seals were disturbed by weighing and tagging operations, but the oiled pups were certainly more disturbed than unoiled pups at the beginning of the season by cleaning operations, veterinary inspection and visiting observers. The lower peak weights may partly reflect the greater disturbance suffered by oiled pups. There was no difference between the mortality of oiled and unoiled pups on the beaches, but insufficient information is available on mortality at sea to study the survival of pups with low weaning weights. To draw more positive conclusions than is possible from this study would require a larger sample of animals. We conclude from the cleaning trials that unless all
Waste Heat in the Aquatic Environment National Research Council Canada. (1976) Waste Heat in the Aquatic Environment. Ottawa, NRCC. Price: $1 .oo. It is probable that the Canadian electricity generating 118
sources of recontamination can also be treated, there is little point in cleaning individual animals. The resultant disturbance is probably more damaging to a pup's chances of survival than the oil itself. We should like to thank M. Cullen, H. Davis and S. B. Evans for assistance with fieldwork, and J. Horwood for help with the statistical analyses. The MAFF Veterinary Investigation Service carried out the post mortem analyses. The Nature Conservancy Council kindly provided financial assistance which enabled J. E. Davis to complete this study. We are also grateful to colleagues for assistance in preparing the manuscript and for helpful comments.
JOHN E. DAVIS
West Wales Naturalist Trust 4 Victoria Place Haverfordwest, Dyfed U.K. SHEILA S. ANDERSON
Seals Research Division Institute for Marine Environmental Research c/ o Fisheries laboratory Lowestoft, Suffolk, U.K. Anderson, Sheila S. (in prep). The Grey seal in Wales. Bonnet, W. N. & Hickling, Grace (1971). The Grey seals of the Farne Islands. Trans. nat. Hist. Soc. Northumb. N.S., 17, 141-162. Boyd, J. M. & Campbell, R. N. (1971). The Grey seal (Halichoerus grypus) at North Rona, 1959-1968. J. Zool. Lond., 164,469-512. Coulson, J. C. & Hickling, G. (1964). The breeding biology of the Grey seal, Halichoerus grypus (Fab), on the Farne Islands, Northumberland. J. Anon. Ecol., 33,485-512. Davies, J. L. (1949). Observations on the Grey seal (Halichoerus grypus) at Ramsey Island, Pembrokeshire. Proc. Zool. Soc. Lond., 119,673-692. Fogden, S. C. L. (1971). Mother-young behaviour at Grey seal breeding beaches. J. Zool. Lond., 164, 61-92. Nature in Wales. (1970). Mammals, 12(2), 110. Snedecor, G. W. & Cochran, W. G. (1971). StatisticalMethods. Iowa, USA: The Iowa State University Press. Straughan, D. (1971). Biological and Oceanographical Survey o f the Santa Barbara Oil Spill, 1969-70. Vol. I. Biology and Bacteriology. Spec. Publ. Allan Hancock Foundation. (Sea Grant Publ. No. 2.) Van Haaften, J. L. (1973). Die Bewirtschaftung von Seehunden in den Niederlanden. Bietriige zur Jagd- und Wildforschung, 8, 345-349.
capacity will increase by at least ten times within the next 25 years. A large part of this increase will be provided by thermal electricity generating plants (either nuclear or fossil-fueled), generally operating at energy efficiencies between 30-40o7o. The energy wasted in these plants is for the most part discharged directly to surface waters as a stream of heated water about 5-10°C higher in temperature. Since they will need large quantities of cool