1

Distribution and abundance of harbour seals (Phoca vitulina) during thebreeding season in the Wash and along the Essex and Kent coasts.

Report to Natural England covering surveys carried out in 2004 to 2011.

Dr David ThompsonNERC Sea Mammal Research Unit

University of St Andrews.

BackgroundThe Wash is the largest estuary in England, and holds the majority of the English harbour

seal (Phoca vitulina) population (Vaughan, 1978). This population has been monitored since

the 1960s, using counts of animals hauled out as indices of population size. The initial

impetus for monitoring this population was to investigate the effects of intensive pup

hunting. When this hunt ceased in 1973 the monitoring program was reduced

In the summer of 1988 an epidemic of phocine distemper virus (PDV) spread through the

European harbour seal population. More than 18000 seal carcasses were washed ashore over

a 5 month period, many of them in areas with high levels of human activity (Dietz, Heide-

Jorgensen & Härkönen, 1989). Mortality in the worst affected populations, in the

Kattegat-Skagerrak, was estimated to be around 60% (Heide-Jorgensen & Härkönen, 1992).

After the end of 1988, no more cases of the disease were observed until the summer of 2002,

when another epidemic broke out (Harding et al., 2002). Mortality in the European

population during the 2002 epidemic was 47%, similar to that seen in 1988 (Harkonnen et al.

submitted). However, on the English East coast the mortality rate estimated from pre and

post epidemic air survey counts was much lower, approximately 22% (Thompson, Lonergan

& Duck, 2005). The pre-epidemic population in 2002 was similar in size to the pre-epidemic

population in 1988 and the disease hit the English population at the same time of year, so to

date there is no clear explanation for the lower mortality rate.

In general, harbour seal population monitoring programmes have been designed to track and

detect medium to long-term changes in population size. As it is difficult to estimate absolute

abundance, monitoring programmes have usually been directed towards obtaining indices of

population size. If consistent, such time series are sufficient to describe populations’

2

dynamics and have been used to track the long-term status of the English harbour seal

population. However, these indices are based on the numbers of individuals observed hauled

out, so their utility depends on this being constant over time and unaffected by any changes

in population density or structure.

Counts are usually carried out during the annual moult, when the highest and most stable

numbers of seals haulout. Unfortunately such counts do not provide a sensitive index of

current population health. It is generally accepted that breeding success is a more sensitive

index. The breeding season is also the time when disturbance of seal haulout groups is likely

to have direct effects. E.g. disturbance of mother/pup pairs will lead to temporary separation

which may have direct effects on pup survival, especially if the disturbance is repeated.

Most of the UK harbour seal population breeds on rocky shore habitats, where identifying

and counting pups is both difficult and expensive. However, on the English east coast

harbour seals breed on open sand banks where pups are relatively easy to observe and count.

As a first step towards improving the monitoring program (to increase its sensitivity to short

term changes), we identified a need for a baseline survey to map the distribution of breeding

harbour seals. In June 2001 Fenland District Council commissioned Sea Mammal Research

Unit to conduct an aerial survey of the entire breeding population in the Wash. Since 2004

Natural England have commissioned single annual breeding season surveys to develop a time

series of pup counts as an adjunct to the annual moult surveys to obtain a more sensitive

index of current status as well as to monitor the distribution of breeding seals. These counts

are conducted at the end of June or beginning of July when the peak counts are expected. In

2008 and 2010 additional funds were provided to obtain a time series of counts within one

breeding season to define the parameters of the pupping curve. In addition to confirming the

date of the peak number of pups ashore and available to be counted, these results can provide

an estimate of the ratio between peak pup counts and pup production and provide an

indication of the likely error on estimates of pup production.

Routine annual moult surveys cover the coast from Donna Nook in Lincolnshire to Scroby

Sands off Great Yarmouth in Suffolk. There are known to be smaller groups of seals at

various sites along the Essex and the north and east Kent coasts. These sites have been

surveyed sporadically during the moult since 2002. In 2011 the Wash pup survey was

extended to cover all sites between Scroby Sands and the Goodwin Sands off eastern Kent.

3

Historical data

One or two complete surveys of the Wash were carried out during the moult, in the first half

of August in each year from 1988 to present. The results, combined with counts at the same

time of year from the period 1968-2007 are shown in fig. 1. The counts increased between

the late 1960s and 1988, at an average of 3.4% pa ( R2=0.62, p<<0.0001). The 1988 count

was obtained approximately one week before the first reports of sick and dead seals being

washed up on the UK coast. The number hauling out fell by approximately 50% between

1988 and 1989, coincident with the PDV epidemic. After 1989 the number increased again,

at an average of 5.9% pa (R2=0.77, p<<0.0001). The post epidemic rate of increase was

significantly higher than the pre epidemic rate ( t=2.87, df=20, p<0.01 (Comparison of

regression coefficients for small samples with unequal residual variances (Bailey 1972)).

Post epidemic counts were also obtained at the other major east coast haulouts outside the

Wash, at Blakeney (45km east) and Donna Nook (40km north). At both sites the counts fell

after 1988, reaching a minimum in 1990 (fig 2). Between 1990 and 2001 Blakeney counts

increased by an average of 14.4% pa. (R2=0.47, p<0.01), and DonnaNook counts by 18% pa

(R2=0.35, p<0.03). The total for all three east coast sites increased at an average rate of

7.2% pa. (R2=0.87, p<<0.0001) (fig 2).

In 2002 there was another outbreak of PDV. The timing of the epidemic and the population

size were similar to 1988. The population in the Wash declined by an estimated 22% based

on results of surveys in 2003 and on a fitted population growth model (Thompson, Duck &

Lonergan, 2005). There appears to have been a continued decline or at least a failure to

recover in the moult counts for the English east coast population. Overall, the combined

count during the moult for the English East coast population in 2006 was 12% lower than the

mean count in 2005, although preliminary results from the 2008 moult count are similar to

the 2005 level. This apparent lack of recovery or continued decline contrasts with the rapid

recovery of the Wadden Sea population that has been increasing at around 12% p.a. since

2002. This failure to recover from the 2002 epidemic is a cause for concern and should be

investigated.

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Breeding season surveys 2004 to 2011

Based on a preliminary assumption that the peak number of pups would be encountered at

the end of June, beginning of July we have surveyed the breeding population between 27th

June and 4th July in each year from 2004 to 2010. In addition in both 2008 and 2010 we

carried out four additional surveys between 12th June and 13th July to establish the form of

the pups ashore curve. In 2011 we surveyed the entire coast and offshore banks from Donna

Nook in Lincolnshire to Deal in Kent on 2nd July. Surveys were carried out over the period

1.5 hours before to 2 hours after low water. All tidal sand banks and all creeks accessible to

seals were examined visually. All groups of more than 10 animals were photographed using

either colour reversal film in a vertically mounted 5X4" format, image motion compensated

camera in 2004 & 2005 or with a hand held digital SLR camera since . The equipment and

techniques are described in detail in Hiby, Thompson & Ward (1986) and Thompson et al.

(2005). Photographs were processed and all seals were identified to species. Harbour seals

were then classified as either pups or 1+ age class. No attempt was made to further

differentiate the 1+ age class

RESULTS

The Wash

A total of 1106 pups and 3283 older seals (1+ age classes) were counted in the Wash on

2/07/2011. No pups were observed at either Donna Nook or at Blakeney point, the two

nearest haulout sites to the North and East of the Wash respectively. This peak count

compares with peak counts of 1432 pups and 3702 older seals (1+ age classes) during the

2010 breeding season survey and 1130 pups and 2523 older seals (1+ age classes) during the

2009 breeding season survey. Previous counts are presented in table 1. These were

distributed over 48 separate haulout groups, although the number of sites is to some extent a

function of the arbitrary division or pooling of groups. Figure 3 shows the distribution of

haulout sites in the Wash and figure 4 shows the counts of seals at each site obtained during

the 2004, 2005, 2006 , 2007, 2008 ,2009, 2010 and 2011 breeding season, For 2008 and

2010 only the peak count survey data are shown. Table 2 presents the data for 2008,2009,

2010 and 2011 and all the raw count data are presented in the appended Excel spreadsheet

along with similar data from a survey carried out in 2001 for Fenland District Council. Pups

were widely distributed throughout the Wash, being present at all but two of the occupied

sites in all years between 2004 and 2011.

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The 2010 survey produced the highest pup count ever obtained in the Wash, 26% higher than

the estimated peak in 2009 which was itself 13.6% higher than the 2008 peak count. The

2011 count was 25% lower than the 2010 peak and within 2% of the 2009 count. Figure 5

suggests that the trend in the counts can be approximated by an exponential increase at an

annual rate of increase of 9% p.a. since 2001. The relatively large increases in 2005-2006,

2009-2010 and the large fall in 2010-2011 indicate that there is a large inter-annual

variability in pup production.

The evolving time series indicates that there was no evidence of a major decline in pup

production after the 2002 PDV epidemic. Despite the large decrease from 2010 to 2011 the

time series is still fairly well represented by a simple exponential increase of 9% p.a.. This

continued increase in pup production contrasts with the apparent decrease in the moult counts

between 2003 and 2007 (figs 1 & 6). Figure 6 shows that the moult count appears to be

increasing for the last few years.

The distribution of pups was relatively constant over the period 2001 to 2005; when pooled

into the four sub-regions the overall geographical spread was similar between years (fig 7).

Almost all of the increase in pup counts and therefore presumably also pup production in

2006 and subsequent years occurred in the eastern half of the Wash, from the mouth of the

Nene eastwards (fig 8).

In 2001 only one pup was seen in the Western region of The Wash. By 2004 around 5% of

total pup production was found on these outer western banks, in 2005 this had further

increased to 9%. However, these numbers are low and the number of pups counted in the

western region has remained reasonably constant since 2006.

Figure 10 shows the locations of groups on open coast line in the area around the mouth of

the river Nene. In 2010 there were two haulout groups within 1 km of the route of the

hovercraft Fig 10. The closest group (group A in Fig 10) was on the east bank of the river

Nene at the closest point on the coast to the drilling barge and at a location that the hovercraft

would pass close to on each return trip along the river channel. In 2010 site A had a

maximum of 36 non pups and 12 pups (Fig 11). Site B was a much larger haulout group

with up to 218 non pups and 52 pups. On the single survey in 2011 site A had 60 non pups

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and 40 pups but site B was empty. Figure 12 shows the peak pupping date counts at the

two sites over the 6 years 2006 to 2011. There is no clear pattern in numbers of pups or non

pups counted at the sites and no indication that the 2010 counts were unusual. Prior to 2006

the sites do not appear to have been important haulouts during the breeding season. The

absence of seals at site B in 2011 is unusual. There were no signs of tracks which suggests

that seals had not been disturbed prior to the survey flight. There were large haulout groups

with pups on Scalman’s Sled at a site not occupied in any of the five breeding surveys in

2010, and larger groups on Outer West Mark Knock than in 2010.

Essex and Kent coasts.

The entire coast of Essex and north and east Kent was surveyed during the harbour seal

moult in 2002, 2003, 2008 and 2010 and during the harbour seal breeding season in 2011.

The locations of all surveyed haulout sites and the numbers of seals counted in all surveys are

presented in table 3. Figure 11 shows the distribution of non-pup harbour seals on 2/7/2011

and indicates the locations of all haulout sites identified in previous surveys. In total 371

non-pup harbour seals were counted. Seals were widely distributed around the coast with

groups on many of the offshore banks and in the sheltered estuary at Hamford Water.

Unlike previous years there were no seals on the sites in the Swale or at Southend. However,

subsequent opportunistic visits to these sites in January 2012 showed that they are still used.

Figure 12 shows the distribution of harbour seal pups on 2/7/2011. A total of 47 pups was

counted. Most were found in the sheltered banks in Hamford water (18 pups) or on the banks

off the mouth of the river Crouch, Foulness and Buxey sands (21 pups).

Figure 13 shows the distribution of grey seals from the same survey. They were found

exclusively on the exposed outer banks, with the largest groups on Goodwin sands. Figure

14 shows the changes in numbers of both species from 2002 to 2011. The numbers of both

species have clearly increased over the past decade. Goodwin sands were not surveyed in

2002, but removing the Goodwin counts does not affect the overall pattern of increase.eve

Discussion

The Wash

7

The most significant event in recent years for harbour seals in the Wash was the recurrence

of a PDV epidemic in 2002. Our standard annual moult surveys indicated that the effect of

this epidemic were less severe than in 1988. There was still a significant reduction of 22% in

our population index, so we might expect a commensurate decrease in pup production.

However, if there were differential sex and/or age linked mortality, the effects of the

epidemic on the dynamics of the population could be more or less severe than expected.

Unfortunately the moult counts cannot differentiate the population into sex or age classes,

and there was little information on the sex and age structure of the seals found dead in 2002.

Although the standard moult counts provide a robust index of population size, it is somewhat

damped and will therefore not be a particularly sensitive indicator of current status of the

population. Pup production can be thought of as a compound of population size and

fecundity and may therefore give a more sensitive index of population status.

The recent low intensity pup survey effort has produced two interesting results that highlight

the advantage of a two pronged approach to seal monitoring. Although there was a well

documented decline of over 20% in the population as a result of the 2002 PDV epidemic

there was no apparent decrease in pup production between the pre and post epidemic counts.

There are several potential explanations for the lack of a decline. If there was differential

mortality, the number of adult females lost to the epidemic may have been small.

Alternatively any decrease in adult female population could have been masked by variations

in fecundity. Alternative scenarios involving temporary immigration are thought to be less

most likely.

The most recent data suggest that the apparently dramatic step change in pup production

between between 2005 and 2006 may have simply been part of a continuing increasing trend.

The large increase in pup count in 2006 was unexpected and hard to explain, but has been

maintained into 2007-2010. Although the moult counts in Wash continued to decline after

the 2002 epidemic they have clearly stabilised and appear to be showing signs of recovery.

The fact that pup production varies much more than the moult population index and more

rapidly than could be accounted for by changes in adult female numbers, means that there

must be wide fluctuations in fecundity and or short term immigration and emigration. At

present we do not have information on pregnancy rates in any UK harbour seal population.

8

Telemetry data from both the English and Dutch populations suggests that movement

between the two areas is unlikely to be sufficient to account for these changes.

As we are conducting only single counts in most years there is a potential danger of

confusing timing effects with actual changes. Therefore, before attempting to draw

conclusions about the causes or implications of changes in pup production it is important that

we are able to discount the possibility that the difference in counts were artefact of the

changes in timing of the surveys.

The timing of the 2004 surveys was constrained by aircraft and staff availability, and the

count in 2004 was approximately 12 days later than in 2001. Although we have no hard

information, local observers suggested that the number of pups might decline in early July as

pups wean and/or begin to spend time foraging with their mothers. We would therefore

expect the 2004 count to represent the same or a lower proportion of the pup production

compared to the 2001 count. The 2004 pup count was in fact 12% higher than the pre-

epidemic count. As a result, we carried out the 2005 count midway between the 2001 and

2004 count dates. The pup count increased slightly between the 2004 and 2005 counts.

Assuming that this indicated that the surveys were occurring around the peak, we carried out

the 2006 count midway between the dates of the 2004 and 2005 flights. The 2007 peak count

was timed to coincide with the date of the 2006 survey.

In 2008 and 2010 we carried out a sequence of surveys to confirm the timing of the peak.

The peak number ashore occurred on or about the 28th June and on or about 1st July,

confirming that the previous years’ counts had been close to the peak. In fact, with the

exception of 2001 and 2004, all counts would have been within 4% of the peak if the timing

in each year was similar to the 2008 or 2010 patterns. The largest under-estimation would

have been in 2001 when the count would have represented 90% of the peak if the timing was

the same as in 2008.

The series of pup counts from 2008 and 2010 confirms the timing of the peak count and will

allow estimation of the shape and therefore the cumulative total of the birth curve. This

confirms that a pup-production monitoring program based on single annual counts with

occasional more intensive surveys, (e.g. every 5 years a series of 4 or 5 surveys to re-estimate

birth curve parameters) will provide data to be combined with the annual total population

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index surveys in August to allow more responsive and sensitive management of the harbour

seal population. However, the fitted pup curve for 2008 did not fit well to the 2010 data. At

present we do not know if this is a problem with 2008 or 2010 or if there is a greater than

expected level of inter annual variation in the behaviour of breeding females and pups.

The observed large increase in pup production in the absence of an equivalent increase in the

moult counts is unexplained at present. It could be generated in various ways:

1. Immigration of a large number of adult females. The absence of any substantial

populations on the east coast means that the source of seals would have to be either

the Wadden Sea or the Scottish East coast. Data on seal movements suggest that

immigration from Scotland is unlikely and that movement between the English and

European populations is unlikely to explain these changes.

2. A continual increase in fecundity. This seems unlikely given the scale of the increase

since 2005, although rapid changes in both directions do suggest wide variation in

fecundity rates.

At present we have no information to allow us to differentiate clearly between these options

and it is likely that a combination of some or all could be operating. However, in each case

the explanation would represent a major change in harbour seal demographics.

The results of the 2001 pup survey suggested that there had been a significant shift in spatial

distribution of breeding seals over the preceding 30 years. The 2004 and 2005 distribution

was similar to the 2001 distribution, suggesting that there has been a real shift in distribution

with a much higher proportion of pups being found in the south eastern corner of the Wash.

At present we do not know why this distributional change is occurring.

The 2010 data from the breeding surveys suggested that the hovercraft activities in the Wash

did not unduly disturb harbour seals close to the route. The two haulout sites nearest to the

hovercraft route were both occupied on all surveys and both had substantial numbers of pups.

One group was as close as possible to the barge and must have been passed regularly by the

hovercraft. Again there was no indication that seals had been disturbed by the close

approaches of the hovercraft or had been prevented from hauling out or pupping in close

proximity of the barge. In 2011 the nearest group held more than double the number of pups,

but the next closest and substantially large group in 2010 was absent in 2011. Although we

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know little about haulout site fidelity in harbour seals in the Wash, it is clear that several

apparently suitable alternative haulout and/or pupping sites were easily accessible. The fact

that seals continued to use the closest site is a strong indication that there was no significant

long term disturbance effect. It is therefore extremely unlikely that they would have had a

detrimental effect on the wider population.

In conclusion, these single annual surveys supplemented by occasional multi survey

programmes to establish the timing of breeding give us an appropriately accurate estimate of

total pup production, the data do indicate that:

1) The breeding population, or at least the pup production was not dramatically reduced

by the 2002 PDV epidemic;

2) Therefore, mortality on breeding females and recruiting females was probably not

higher than the population average;

3) The pup production has not followed the decrease and later stabilisation in moult

counts and has in fact grown by 9% pa since 2002;

4) A single series of multiple pup counts within one season allows us to estimate the pup

production in years with only a single count around the peak pupping dates, and will

provide confidence intervals on the pup production estimates.

5) Wide variation in ratio of pups to moult adult count suggests large changes in

fecundity.

6) There is no evidence that the position of the drilling barge or the activities of the

hovercraft had any long term effect on seal haulout patterns.

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References

Bowen, W.D., Boness, D.J., & Iverson, S.J. (1999) Diving behaviour of lactating harbourseals and their pups during maternal foraging trips. Canadian Journal of Zoology - RevueCanadienne de Zoologie, 77, 978-988.

Hiby, A. R., Thompson, D. & Ward, A. J. (1987). Improved census by aerial photography -an inexpensive system based on non-specialist equipment. Wildl. Soc. Bull. 15, 438-43.

Lonergan, M., Duck, C.D., Thompson, D., Mackey,B.L., Cunningham,L. & I L Boyd (2007)Using sparse survey data to investigate the declining abundance of British harbour seals.";Journal of Zoology; 271(3):261-269

Reijnders, P.J.H. & Fransz, H.G. 1978. Estimation of birth rate and juvenile mortality fromnumbers of juveniles in a seal population with normally dispersed reproduction. I.C.E.S.C.M. 1978/N:7

Reijnders, P.J.H. (1978) Recruitment in the harbour seal (Phoca vitulina) population in theDutch Wadden Sea. Neth. J. Sea. Res. 12(2): 164-179

Thompson, D, Lonergan, M & Duck, C.D. (2005) Population dynamics of harbour seals(Phoca vitulina) in England: growth and catastrophic declines. J. Appl. Ecol. 42 (4): 638-648

Vaughan, R. W. (1978). A study of common seals in the Wash. Mammal Rev. 8, 25-34.

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Table 1. Counts of harbour seal pups and 1+ age classes in the Wash.

2001 2004 2005 2006 2007 2008 2009 2010 2011

Pups 548 613 651 1054 984 994 1130 1432 1432

1+ age classes 1802 1766 1699 2381 2253 2009 2523 3702 3702

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Table 2. Counts of harbour seal pups and 1+ age classes at haulout sites in the Wash, 2007 to 2011.

02/07/2011 03/07/2010 02/07/2009 28/06/2008 29/06/2007Map# site name lat long 1+ages pups 1+ages pups 1+ages pups 1+ages pups 1+ages pups

1 Inner Knock 53.0819 0.3640 63 5 96 9 96 15 51 11 41 13

2 Inner Dogs Head 53.0355 0.3763 33 7 25 4 42 7 20 6 34 5

3 Friskney 53.0342 0.3087 59 20 115 32 88 29 49 28 66 20

4 Friskney Middle 53.0342 0.3087 17 8 0 0 0 0 0 0 0 0

5 Friskney South 52.9967 0.2250 23 10 84 44 66 34 20 9 20 9

6 Long Sand N/E End 53.0188 0.3339 0 0 0 0 0 0 0 0 0 0

7 Long Sand Middle 53.0053 0.2967 78 20 81 25 57 25 27 9 37 9

8 Ants 52.9782 0.2641 11 3 0 0 0 0 1 0 9 4

9 Rodger 52.9633 0.2167 0 0 4 0 2 0 2 0 2 1

10 Black Buoy 52.9238 0.1168 51 11 61 8 76 9 58 7 137 52

11 Boston Channel 52.9167 0.0583 68 17 60 32 25 15 48 33 58 30

12 Herring Shoal 52.9045 0.0642 107 18 65 26 45 16 0 0 0 0

13 Toft East 52.9318 0.1527 46 7 63 21 24 10 57 11 63 22

14 Toft West 52.9199 0.1333 14 4 0 0 26 5 0 0 19 18

15 Mare Tail 52.9167 0.1517 85 19 21 9 65 43 16 10 36 17

16 Main End 52.9070 0.1933 25 10 21 7 24 9 26 9 81 18

17 Gat End 52.9122 0.2033 0 0 17 11 0 0 0 0 27 7

18 Gat Sand 52.9346 0.1983 60 10 45 10 57 14 32 14 25 10

19 Puff 52.8987 0.1210 0 0 19 15 15 7 39 23 65 51

20 Kenzies Creek 52.8997 0.1057 63 22 105 44 0 0 44 21 38 30

21 Fleet Haven Marsh 52.8769 0.1523 32 1 0 0 0 0 0 0 0 0

22 Fleet Haven Middle 52.8842 0.1571 149 35 358 139 148 75 212 118 246 97

23 Fleet Haven Lower 52.9085 0.1565 164 70 0 0 0 0 0 0 0 0

24 Fleet Haven Mouth 52.9218 0.1579 0 0 32 31 0 0 28 12 0 0

25 Evans Creek 52.8776 0.1692 34 11 65 25 11 8 58 40 48 7

26 Dawesmere Creek 52.8592 0.1912 4 3 75 43 92 81 85 56 78 53

27 OWMK 1 52.8745 0.2333 22 8 1 1 7 6 7 0 74 18

28 OWMK 2 52.8667 0.2500 38 23 0 0 0 0 0 0 0 0

29 Nene Channel 1(or pooled) 52.8751 0.2199 33 11 41 29 0 0 20 4 0 0

30 Nene Channel 2 52.8672 0.2161 41 19 4 1 0 0 0 0 0 0

14

31 Nene Channel 3 Barge 52.8604 0.2140 60 40 16 12 30 22 15 15 0 0

32 Nene Channel 4 52.8455 0.2061 0 0 218 52 98 29 92 40 123 48

33 Nene Channel 5 52.8271 0.2192 0 0 24 12 0 0 0 0 0 0

34 IWMK 52.8515 0.2354 57 25 245 137 155 106 128 104 22 22

35 Scalmans Sled 52.8572 0.2581 255 121 0 0 0 0 0 0 0 0

36 Breast Sand 52.8283 0.2745 85 18 256 77 67 52 110 85 0 0

37 Thief West 52.8778 0.2732 61 14 7 2 8 4 28 13 155 74

38 Thief East 52.8778 0.2732 0 0 46 11 59 20 221 73 12 4

39 Seal Sand (West)/Black Shore 52.8750 0.3117 290 70 81 35 69 16 15 10 176 58

40 Seal sand (East) 52.8808 0.3524 218 48 244 82 333 140 24 15 161 64

41 Seal Sand/Daseleys 52.8819 0.3512 0 0 0 0 0 0 0 0 42 17

42 Hull Sand 52.8399 0.3075 285 127 489 141 158 93 225 101 203 69

43 Bull Dog Sand 52.8656 0.3556 81 33 59 45 102 49 52 22 0 0

44 Pandora 52.8619 0.3546 0 0 210 84 254 75 77 33 104 60

45 Black Guard 52.8829 0.3721 0 0 24 5 5 1 0 0 39 28

46 Old Bell 52.9000 0.3718 0 0 0 0 5 0 1 0 0 0

47 Stylemans Middle 52.8868 0.3804 48 3 5 0 30 7 16 0 11 4

48 Pie Corner 52.8345 0.3273 54 30 0 0 0 0 6 1 101 45

49 Lynn Channel 52.8000 0.3583 468 205 310 162 175 108 90 60 0 0

50 Sunk Sand 52.9754 0.4930 1 0 10 0 9 0 9 1 0 0

Wash Total 3283 1106 3702 1423 2523 1130 2009 994 2353 984

15

Table 3. Counts of harbour seals (pups and 1+ age classes) and grey seals (all ages) at haulout sites along the Essex and Kent coast 2002 to 2011.

02/07/2011 07/08/2010 09/08/2008 09/08/2003 12/08/2002

site name latitude longitude

harboursealadult

harboursealpup

greyseal

harboursealadult

greyseal

harboursealadult

greyseal

harboursealadult

greyseal

harboursealadult

greyseal

Hamford Water 1 51.88939 1.228 32 10 0 38 0 41 0 17 0 28 0

Hamford Water 2 51.87894 1.216667 7 0 0 7 0 0 0 0 0 0 0

Hamford Water 3 51.87703 1.2265 18 8 0 10 0 16 0 0 0 0 0

Hamford Water 4 51.87611 1.258889 1 0 0 13 0 6 0 0 0 0 0

Ryefleet Channel 51.80861 0.954444 1 1 0 2 0 3 0 0 0 2 0

Blackwater 51.70889 0.773889 6 0 0 0 0 0

Tillingham 51.68222 0.946111 9 4 0 43 0 0 0 0 0 0 0

Foulness Sand 51.65667 1 11 1 0 2 17 7 0 11 4 0 0

Buxey sand N 51.70667 1.066667 40 13 0 85 0 25 61 0 9 12

Buxey Sand S 51.66667 1.016667 20 4 0 7 0 0 0 0 0 0 0

Gunfleet Sand 51.78667 1.368333 3 0 12 8 25 14 10 0 0 0 0

Sunk Sand 51.71667 1.433333 16 0 10 9 7 10 1 0 0 0 0

Long Sand Inner 51.63333 1.408333 23 0 33 0 0 0 0 0 0 0 0

Maplin Sands 51.56667 0.914722 0 0 0 24 12 2 5 0 0 0 0

Shoebury Ness 51.51 0.913333 0 0 0 18 0 3 0 0 0 0 0

Southend 51.52288 0.691667 0 0 0 0 0 3 1 2 0 7 0Horse Sand(Swale) 51.35167 0.920633 0 0 0 0 0 22 0 9 0 7 0

St Mary's marsh 51.49583 0.546389 0 0 0 0 0 3 0 0 0 0 0

Isle of Grain 51.47583 0.72 0 0 0 3 0 0 0 0 0 0 0

Margate 1 51.42222 1.261667 0 0 21 3 9 44 16 1 0 6 0

Margate 2 51.44667 1.316667 34 0 3 48 12 7 2 0 0 13 0

Margate 3 51.435 1.345 36 2 0 0 0 10 0 0 0 0 0

Goodwin 1 51.30639 1.527778 20 0 2 48 12 0 0 55 0 * *

Goodwin 2 51.28028 1.528889 39 4 0 0 0 0 0 10 0 * *

Goodwin 3 51.23889 1.563333 26 0 0 0 0 0 0 9 0 * *

Goodwin 4 51.21083 1.563333 35 0 214 11 299 97 125 5 92 * *

Total 371 47 295 379 393 319 160 180 96 72 12

16

0

1000

2000

3000

1965 1975 1985 1995 2005

nu

mb

er

ofse

als

year

harbour seals in The Wash

epidemic52% drop

epidemic22% drop

Figure 1. Aerial survey counts of harbour seals in the Wash during the annual moult

for the period 1968 to 2009. Dramatic declines in 1988 and 2002 were the result of

epidemics of Phocine Distemper Virus. The fitted polynomial for 2003 to 2010 is

included simply for illustration.

17

0

1000

2000

3000

4000

1988 1993 1998 2003 2008

num

ber

ofharb

our

seals

year

Wash Blakeney DonnaNook Eastern England total

Figure 2. Aerial survey counts of harbour seals at sites in East Anglia during

recovery from the 1988 and 2002 PDV epidemics. There were no significant

changes between 2003 and 2009, the fitted polynomial is included simply for

illustration.

18

Figure 3. Locations of haulout sites in the Wash. Numbers correspond to locations in

table 2.

19

Figure 4. Distribution of pups in the Wash in 2011. Numbers of pups are represented by

the areas of the circles on each site. Locations given to nearest 50m. Names of haulout

sites together with latitudes and longitudes and numbers of seals at each site in 2007 to

2011 are given in table 2.

20

Figure 5. Maximum counts of pups in The Wash between 2001 and 2010. The

fitted line is a simple exponential.

y = 9E-92e0.1079x

R2

= 0.8663

0

500

1000

1500

2000 2002 2004 2006 2008 2010 2012

year

ma

xp

up

co

un

t

21

0

1000

2000

3000

2000 2002 2004 2006 2008 2010 2012

nu

mb

er

ofse

als

year

PDV epidemic

Figure 6. Maximum counts of pups in The Wash between 2001 and 2010 together

with the standard moult population monitoring counts for the same sites. The fitted

line for the pups is a simple exponential and a simple quadratic has been fitted to the

moult count data to illustrate the general trend.

22

0

500

1000

1500

2000

2500

ad

ult

co

un

t

Outer west Inner west Creeks East .

0

200

400

600

800

1000

pu

pco

un

t

Outer west Inner west Creeks East .

2001 2004 2005 2006 2007

2008 2009 2010 2011

Figure 7. Distribution of harbour seal pups and non-pups (1+ age classes) in the

Wash during the 2001 & 2004,- 2011 breeding seasons pooled into geographical

sub regions(Vaughan, 1978). For 2008 and 2010 the distribution on the day of the

maximum count is presented.

23

0

500

1000

2000 2002 2004 2006 2008 2010 2012

pup

count

year

Outer West Inner West Creeks South East

Figure 8. Distribution of harbour seal pups in the Wash during the 2001 to 2011

beeding seasons pooled into geographical sub regions(Vaughan, 1978). For 2008

and 2010 the distribution on the day of the maximum count is presented. The most

dramatic change is the sudden increase in numbers of pups in the complex of banks

in the south east corner of the Wash in 2006. This increased importance of these

banks was maintained through to 2011.

24

Figure 9 Map of locations of open coast (as opposed to creeks) haulout sites adjacent to

the drilling barge and hovercraft route. Counts for site a and b are presented below in

(Fig 10). Approximate positions of the barge and hovercraft route are shown.

a

b

barge

Hovercraft route

25

0

10

20

30

40

50

60

2006 2007 2008 2009 2010 2011 2012

pu

pco

un

t

year

pups group a group b

Figure 10 Counts of pups at the two haulout sites closest to the drilling barge as

shown on figure XX. Group b was absent , ie there were no pups or adults on the site

on the survey date in 2011.

26

Figure 11. Distribution of 1+ age classes of harbour seals in south east England on2/7/2011. Numbers of seals are represented by the areas of the circles on each site.Locations given to nearest 50m. Black dots indicate known seal haulout sites with noharbour seals present during this survey.

27

Figure 12. Distribution of harbour seal pups in south east England on 2/7/2011.

Numbers of pups are represented by the areas of the circles on each site. Locations given

to nearest 50m. Black dots indicate known seal haulout sites with no pups present during

this survey.

28

Figure 13. Distribution of grey seals (all ages) in south east England on 2/7/2011.Numbers of seas are represented by the areas of the circles on each site. Locations givento nearest 50m. Black dots indicate known seal haulout sites with no grey seals presentduring this survey.

29

0

100

200

300

400

2002 2004 2006 2008 2010 2012

seal

cou

nts

year

harbour seals grey seals

Figure 14. Counts of harbour seals and grey seals in south east England (Essex

and Kent) between 2002 and 2010.