A preliminary analysis was made of the seal sighting data held in the JerseySeals database for 1999 and 2000. The majority of sightings are of the Grey Seal (Halichoerus grypus). Sightings were reported in all seasons and all months (except December 2000). 45% of sightings involved a single seal. About a third (32%) involved three or more. The greatest number of individual seals believed sighted in one day was 23. Effort related findings for Les Écréhous reef show sightings were made on 43 out of 45 observation days (96%) in 1999. For 2000, sightings occurred on all 48 observation days (100%). For both years this involved data for all seasons. A few individual seals may have been observed during more than one year. In the light of these findings the previous status of seals in Jersey as “occasional” should be reviewed.
Seals have been sighted off Jersey’s coast and offshore reefs and islands for many years (see Status of Seals in Jersey). JerseySeals maintains a database of the sightings of seals for the Channel Islands area: it contains over 800 records each with more than 20 fields (although not all fields have data for all records). Further details of the database and methodology will be published in the future – meanwhile some key findings are made available here.
The present article focuses on 1999 and 2000 and Jersey (which includes the offshore reefs of Les Écréhous, Les Dirouilles, Paternosters and Les Minquiers). The JerseySeals database (“the database” for the rest of this article) for this period and area is believed to be comprehensive.
The status of seals has been described as “occasional” or “occasionally seen” and then in only very small numbers. There is also reference to “frequently seen” although the only known prior records report few sightings annually - in single figures or tens (see Status of Seals in Jersey).
· Sighting - the event where and when one or more seals are seen: a sighting involving more than one seal is counted as one sighting.
· Group size - the number of seals seen in a sighting.
· Dedicated sighting - a sighting where a primary purpose of the recorder at the time is to sight seals (for example in a boat passage where a primary purpose is the sighting of seals).
· Casual sightings – sighting where, at the time, there are interests other than seal observation foremost in the recorder’s mind.
· Effort related sighting - a dedicated sighting which has an associated measure of the effort taken in achieving the sighting (for example where records are kept of every visit to a site whether or not seals are seen there on any occasion).
· Observation day – a day when some effort is made to sight a seal.
Much of the data in the database involves casual sightings that are neither dedicated nor effort related. Without effort related data any changes in the number of sightings from one time to another (for example between years) do not necessarily reflect changes in the seal population – they could equally reflect changes in the effort involved in achieving sightings. There is no data here to support any suggestion that the seal population has changed – it may well be that there have been significant changes in the population but the data cannot elucidate that.
There is no known Channel Island dedicated or effort related data for 2000 or before except that of JerseySeals. The intensity of the seal-sighting endeavour generated by JerseySeals especially during 1999 and 2000 and most particularly during August in both years resulted in very many reported sightings on some days. This was a maximum on 1st August 2000 when there were 24 sightings between the hours of 07:45 and 17:15 UTC, involving 4 recorders and covering much of Les Écréhous reef. The same seal or seals may have been recorded more than once in different sightings.
Table 1 shows seal sighting by species – compare with Table 1 in Local Seal Species on this website.
Table 1: Sightings of the Harbour (or Common) Seal (Phoca vitulina), Grey Seal (Halichoerus grypus) and Seals of unidentified species in the database for Jersey for 1999 - 2000
|
Harbour Seal Sightings |
Grey Seal Sightings |
Unidentified Seal Species |
|
0 |
544 |
50 |
|
|
· Grey Seal identified in the report (or recorded so by default). |
· Not necessarily Grey or Harbour. |
Table 2 shows the numbers of seal sightings around Jersey from the database for 1997 to 2000 inclusive.
Table 2: Records of the number of seal
sightings and the number of days on which there were sightings for Jersey from database
records 1997 - 2000.
Year
|
Number of Sightings |
Number of Days
on which there were sightings |
|
1997 |
6 |
5 |
|
1998 |
19 |
14 |
|
1999 |
138 |
64 |
|
2000 |
456 |
98 |
Note
JerseySeals commenced data recording in 1997. |
||
Table 3 shows sightings data from the database - month by month for 1999 and 2000 for Jersey and Écréhous only (see Channel Islands Map).
Table 3: Records of the number of seal sightings and the number of days on which there were sightings for the database 1999 – 2000 for Jersey and Écréhous only.
|
Year |
1999 |
2000 |
||||||
|
|
Jersey |
Écréhous only |
Jersey |
Écréhous only |
||||
|
Month |
Days |
Sightings |
Days |
Sightings |
Days |
Sightings |
Days |
Sightings |
January
|
4 |
5 |
2 |
2 |
4 |
7 |
4 |
7 |
|
February |
1 |
3 |
1 |
2 |
2 |
2 |
2 |
2 |
|
March |
3 |
7 |
2 |
5 |
4 |
12 |
2 |
6 |
|
April |
2 |
4 |
1 |
3 |
6 |
22 |
3 |
6 |
|
May |
10 |
14 |
6 |
10 |
7 |
29 |
7 |
28 |
|
June |
5 |
7 |
4 |
5 |
12 |
61 |
12 |
60 |
|
July |
15 |
48 |
15 |
47 |
17 |
74 |
17 |
66 |
|
August |
13 |
31 |
11 |
28 |
22 |
131 |
21 |
114 |
|
September |
3 |
8 |
3 |
7 |
19 |
95 |
19 |
86 |
|
October |
3 |
6 |
3 |
6 |
4 |
20 |
3 |
15 |
|
November |
2 |
2 |
2 |
2 |
1 |
3 |
0 |
0 |
|
December |
3 |
3 |
2 |
2 |
0 |
0 |
0 |
0 |
Total
|
64 |
138 |
52 |
119 |
98 |
456 |
90 |
390 |
Notes
·
“Jersey” refers to events around Jersey including the Écréhous, Dirouilles,
Paternoster and Minquiers reefs (but excluding data for elsewhere in the
Channel Islands). ·
“Écréhous only” refers to events within Les Écréhous reef. ·
“Days” are the number of days when seals were sighted. ·
A “0” for Days or Sightings does not imply the absence of seals merely
the lack of sightings. |
||||||||
Table 4 presents the data from Table 2 accumulated for both years 1999 and 2000 and arranged by season.
Table 4: Accumulated data 1999 and 2000 for Jersey and
arranged by season.
|
|
Jersey only, 1999 and 2000, accumulated data |
|
|
|
Days |
Sightings |
Spring
|
32 |
88 |
|
Summer |
84 |
352 |
|
Autumn |
32 |
134 |
|
Winter |
14 |
20 |
Total
|
162 |
594 |
Notes
· See Notes to Table 3. · Spring: March, April, May. · Summer: June, July, August. · Autumn: September, October, November. · Winter: December, January, February. |
||
Seals sighting reports usually include the group size seen at the time and place of the sighting. This data is presented in Table 5 and Chart 1 for the database 1999 and 2000 and Jersey only data. Nearly half (45%) of sightings involved a single seal – almost a third (32%) involved 3 or more.
|
Group size |
Number of sightings with that group
size |
Percentage of sightings with that
group size (%) |
|
1 |
264 |
45 |
|
2 |
134 |
23 |
|
3 |
77 |
13 |
|
4 |
49 |
8 |
|
5 |
30 |
5 |
|
6 |
10 |
2 |
|
7 |
6 |
1 |
|
8 |
9 |
2 |
|
9 |
6 |
1 |
|
10 |
3 |
0.5 |
|
11 |
0 |
|
|
12 |
0 |