Wintering aggregations of Steller sea lions in the Ishikari‐Bay, Sea of Japan Kaoru HATTORI, Takeomi ISONO and Orio YAMAMURA Hokkaido National Fisheries Research Institute, FRA
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Wintering aggregations of Steller
sea lions in the Ishikari‐Bay, Sea of Japan
Kaoru HATTORI, Takeomi
ISONO and Orio
YAMAMURAHokkaido National Fisheries Research Institute, FRA
Steller
sea lions (SSLs, Eumetopias
jubatus)
Piscivorous marine mammalOpportunistic feeder
Distribution and feeding are affected by prey availability
Rookery
SSLs
in the Okhotsk Sea
Okhotsk Sea
0
4,000
8,000
12,000
16,000
20,000
60's 70's early 80's
late 80's
90's 00‐01 02‐03 04‐05 06‐07
No. SakhalinNorthern part of Sea of OkhotskKuril Is.
Rookery
Breeding Season(Jun.‐Aug.)
PuppingMating Nursing
SSLs
in the Okhotsk Sea
Wintering Season (Oct.‐May)
Growth NursingGestation
Okhotsk Sea
Information on SSLs
distribution and abundance
We examined spatial distribution of SSLs
in the Sea of Japan. 1) Observation of haul‐out sites2) Aerial surveys3) Encounter with fishermen
Sea of Japan; important wintering ground for SSLs
originating from
the Okhotsk Sea
To their conservation and managementTo the study of “hot‐spots”
Major haul‐out sites
▲
▲
▲
Sea of Japan
Ishikari‐Bay Ofuyu
Point
Major haul‐out sites
▲
▲
ID 04/05 05/06 06/07 07/08 08/09 YearsБ66 ● ● 2Б618 ● ● 2C541 ● ● 2И190 ● ● ● ● 4И234 ● ● ● 3И304 ● ● ● 3И322 ● ● 2Я86 ● ● 2Я112 ● ● 2Я139 ● ● 2
Sea of Japan
Ishikari‐Bay Ofuyu
Point
Major haul‐out sites
▲
Isono
et al. 2010
ID 04/05 05/06 06/07 07/08 08/09 YearsБ66 ● ● 2Б618 ● ● 2C541 ● ● 2И190 ● ● ● ● 4И234 ● ● ● 3И304 ● ● ● 3И322 ● ● 2Я86 ● ● 2Я112 ● ● 2Я139 ● ● 2
Sea of Japan
Ishikari‐Bay Ofuyu
Point
Hauling Swimming
Ishikari Bay
SSLs
distribution along the coastal line during winterFeb. 2011 Mar. 2008
Hauling Swimming
Ishikari Bay
SSLs
distribution along the coastal line during winterFeb. 2011 Mar. 2008
Density2.8 / km2
No.
SSLsOther mammals
SSLs
distribution on late April based on aerial surveys
Offshore distributionlow density
Rare in the costal region
Line‐transect samplingCovered the continental shelf part
Density0.01 / km2
2000‐20032006‐2009
0
50
100
EML EML EML EML EML EML EML EML EM LOct Nov Dec Jan Feb Mar Apr May Jun
0
50
100
EML EML EML EML EML EML EML EML EM LOct Nov Dec Jan Feb Mar Apr May Jun
Local abundance index; Encounter rate with fishermen and SSLs
0
50
100
150
200
250
02/03 03/04 04/05 05/06 06/07 07/08 08/09 09/10
max. No. SSLs
year
A
B
C
D
Ofuyu point become the major sites since 2003/04.Cape Kamui has not been used as a haul‐out site, recently.
A; Bentenjima
B; Ofuyu
C; Kamui
D; Sebachi
Monitoring of haul‐out sites
Not reliable because of disturbance
“sea lions year in
Japan”
from October 2003
to June 2004
Fishery in the Ishikari Bay during winter
0
100
200
300
400
500
600
700
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Catch (t)
Seasonal change of herring catchin the Ishikari‐Bay
spawning
Fishery in the Ishikari Bay during winter
0
100
200
300
400
500
600
700
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Catch (t)
Seasonal change of herring catchin the Ishikari‐Bay
spawning
Other fish spp.
Pacific cod
AnchovyArabesque greenling
Octopuses
Flounders
Sand lance
Herring
Walleye pollock
Diets of SSLs(Goto, unpublished)
0200
400
600800
1,000
1,2001,400
1,600
1,8002,000
98/99 99/00 00/01 01/02 02/03 03/04 04/05 05/06 06/07 07/08 08/09 09/10
Catch (t)
Year
West side
East side
0
50
100
EML EML EML EML EML EML EML EML EM LOct Nov Dec Jan Feb Mar Apr May Jun
Ishikari‐Bay
Change of herring
Fishery damage by SSLs
in the Ishikari‐Bay
0
2,000,000
4,000,000
6,000,000
8,000,000
10,000,000
12,000,000
98/99 99/00 00/01 01/02 02/03 03/04 04/05 05/06 06/07 07/08 08/09 09/10
US dlrs.West sideEast side
Amount of fishery damage
SummaryThe high concentration of SSLs in the Ishikari‐Bay was observed during winter season, especially eastern area.The abundance of SSLs increased as herring gathered in the Bay for spawning.SSLs were probably attracted to this spawning aggregation of herring.Herring is also important target of commercial fishery during winter in the Bay.The competition between SSLs and fishery for herring is a serious problemDuring winter season, the Ishikari‐Bay is one of hot‐spots for SSLs and human activity
Related Documents
