Harbour Porpoises in the Southern North Sea

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Harbour Porpoises in the Southern North Sea
The Harbour Porpoise in the Southern North Sea
an update

• C.J. Camphuysen

C.J. Camphuysen, Royal NIOZ
Foto Bart Vastenhouw, Texel
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Southern North Sea whales dolphins

27 taxa
Source Camphuysen C.J. Peet G. 2006. Whales and
dolphins of the North Sea. Fontaine Uitgevers,
Kortenhoef. Camphuysen C.J. Peet G. 2006.
Walvissen en dolfijnen in de Noordzee. Fontaine
Uitgevers, Kortenhoef. (Updated)
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Status in The Netherlands, based on 1970-2005
data (36 years)
Status Resident Regular
visitor Irregular visitor Vagrant or annual
visitor
Number of years found or observed (n)
32 years 18-31 years 4-17 years lt4
years
Percentage of years found or observed ()
gt90 50-90 10-50 lt10
Species White-beaked dolphin (34)
Bottlenose dolphin (23) Fin Whale (9)
Sei Whale (3) Harbour Porpoise
(36) Minke Whale (16) Humpback
Whale (2) Sperm Whale (13)
Rissos Dolphin (3) Sowerbys beaked (6)
Blainvilles beaked (1) Pilot Whale
(16) White Whale (4) Bottlenose Whale
(4) Striped Dolphin (6) common
Dolphin (11) White-sided Dolphin
(11) Number of species 2 1 10 4
17 taxa
Source Meij S.E.T. van der C.J. Camphuysen
2006. Distribution and diversity of whales and
dolphins (Cetacea) in the Southern North Sea
1970-2005. Lutra 49(1) 3-28.
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Harbour porpoise in the southern North
Sea Historical evidence

• permission for culling in 14th century (1340)
• appreciated as food in 16th century (1585)
• bycatch in cod fisheries, 16th century (1585)
• known and probably common 19th century
• treated as sea monsters in 19th century (1829)

Remains of porpoises and other cetaceans in
pre-historic middens along the coast indicative
of the use of stranded animals, or catches
Source Camphuysen C.J. Peet G. 2006. Walvissen
en dolfijnen in de Noordzee. Fontaine Uitgevers,
Kortenhoef Coenen A. 1585. Walvisboeck
Leeuwarder Courant 18 April 1829 Leidsch Dagblad
28 augustus 1887.
Source Louwe Kooijmans L.P. et al. 2005.
Nederland in de prehistorie. Bert Bakker,
Amsterdam. Painting A. Coenen 1585. Het
Walvisboeck.
eikenhouten boomstamkano (vroege-) midden
ijzertijd
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Harbour porpoise in the southern North Sea 20th
century

• Harbour porpoise, indigenous marine mammals in
  the Southern North Sea
• early 20th century - high numbers, frequent
  strandings, incidental bycatch in fishing gear
• 1950s-1960s - population decline, local
  extinction
• 1970s-1990s - very few sightings / few
  strandings
• 1990s-early 21st century - rapid increase in
  sightings, strandings frequency increase,
  incidental bycatch in fishing gear

Camphuysen C.J. Peet G. 2006. Whales and
dolphins of the North Sea. Fontaine Uitgevers,
Kortenhoef. Camphuysen C.J. Peet G. 2006.
Walvissen en dolfijnen in de Noordzee. Fontaine
Uitgevers, Kortenhoef
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Harbour porpoise coastal sightings (n 9682)
versus strandings (n 3030), 1970-2008 (
of all seen and of all beached)

Publication update from NZG Marine Mammal Database
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Harbour porpoise coastal sightings, 1970-2009 (n
10,325) (seasonal pattern, 10-day periods,
summer centralised)
J F M A M J J A S O N D
Unpublished data, NZG Marine Mammal Database
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Harbour porpoise coastal sightings, 1970-2009 (n
10,325) (seasonal pattern, 10-day periods,
winter centralised)
J J A S O N D J F M A M
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Harbour porpoise strandings, 1970-2009 (n
3069) (seasonal pattern, 10-day periods, summer
centralised)
J F M A M J J A S O N D
Unpublished data, NZG Marine Mammal Database
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Harbour porpoise strandings, 1970-2009 (n 3062)
(seasonal pattern, 10-day periods, winter
centralised)
J A S O N D J F M A M J
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Harbour porpoise sightings versus strandings
(seasonal pattern, summer centralised)
Conclusion sightings frequency ? strandings
frequency
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Harbour porpoise North Sea distribution (from
ESAS database)
Source Reid J.B., Evans P.G.H. Northridge S.P.
(eds) 2003. Atlas of cetacean distribution in
north-west European waters. Joint Nature
Conservation Committee, Peterborough, 76pp.
HARBOUR PORPOISE Phocoena phocoena
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Harbour porpoise North Sea distribution (from
SCANS-1 II)
Harbour porpoise abundance whole survey
area 386,000 animals in July 2005 (95
confidence interval 260,000-570,000 animals North
Sea (north and east of Strait of Dover) 239,061
North Sea and adjacent waters 340,000 in 1994
July (SCANS I) 335,000 in 2005 July (SCANS
II) Large-scale changes in the distribution of
porpoises were observed between 1994 and
2005. In 1994, porpoises most abundant off the
northeastern coast of the UK and around Denmark.
In 2005, the main concentration had shifted to
the southern North Sea. Why this change in
distribution has occurred is not clear.
Source LIFE04NAT/GB/000245, FINAL REPORT, Small
Cetaceans in the European Atlantic and North Sea
(SCANS-II)
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Harbour porpoise North Sea distribution (from
SCANS-1 II)
1994
2005
Harbour porpoise estimated density surface
(animals per km2) in 1994 and 2005.
Source LIFE04NAT/GB/000245, FINAL REPORT, Small
Cetaceans in the European Atlantic and North Sea
(SCANS-II)
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A population shift south ? And if soWhy ??
distributional shifts rather than population
fluctuations underlie the trends observed. The
re-distribution of harbour porpoises in the North
Sea may have been triggered by local reductions
or shifts in principal prey availability .
Source Camphuysen C.J. 2004. The return of the
harbour porpoise (Phocoena phocoena) in Dutch
coastal waters. Lutra 47(2) 113-122
we suggest that negative effects of climate
change on sandeel availability may have negative
effects on harbour porpoise populations in the
North Sea by increasing the likelihood of
starvation in spring
Source MacLeod C.D. et al. 2007. Linking
sandeel consumption and the likelihood of
starvation in harbour porpoises in the Scottish
North Sea could climate change mean more
starving porpoises? Biology Letters 3 185-188
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Harbour porpoise sightings versus strandings
(seasonal pattern, winter centralised)
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Harbour porpoise in the Wadden Sea (gt 1990) all
data, Jun-Dec Dutch seabird group, marine mammal
database
489 sightings, 861 individuals
Unpublished data, NZG Marine Mammal Database
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Harbour porpoise in the Wadden Sea (gt 1990) all
data, Jan-May Dutch seabird group, marine mammal
database
1022 sightings, 2658 individuals
Unpublished data, NZG Marine Mammal Database
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Harbour porpoise in the Delta area (gt 1990) all
data Dutch seabird group, marine mammal database
301 sightings, 609 individuals
337 sightings, 780 individuals
Unpublished data, NZG Marine Mammal Database
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Harbour porpoise Delta area versus Wadden Sea (gt
1990) Dutch seabird group, marine mammal database

Unpublished data, NZG Marine Mammal Database
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Harbour porpoise Delta, mainland coast Wadden
Sea (gt 1990) Dutch seabird group, marine mammal
database


Unpublished data, NZG Marine Mammal Database
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Harbour porpoise distribution patterns, trends,
migration and population size What is needed
Seasonal patterns offshore? Total numbers
southern North Sea? Migration and origin?
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Harbour porpoise monitoring techniques (options)
Aerial surveys
Ship-based surveys
Passive acoustic monitoring
Acoustic surveys
T-pods
T-POD Timing POrpoise Detector
Hydrophones
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Harbour porpoise monitoring options

• A plea for more consistent research
• Summary current knowledge (temporal spatial
  patterns, urgent research needs)
• Research questions to be formulated
• Monitoring platforms chosen
• Field studies
• Data-processing, evaluation, synthesis, ....and
• Publication in open, refereed literature

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Harbour porpoise a perspective from documented
strandings
A sex-ratio change and a drop in size when did
this happen?
Unpublished data, NZG Marine Mammal Database
www.walvisstrandingen.nl
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Harbour porpoise a perspective from documented
strandings (1) Sexratio and mean length
From sexratio a gradual shift? From total
length 2 distinct periods
even
Current situation frequent strandings,
predominantly juvenile males
Unpublished data, NZG Marine Mammal Database
www.walvisstrandingen.nl
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Harbour porpoise a perspective from documented
strandings (2) Age composition

Assumptions Female gt150 adult Male gt145
adult All lt95 neonate
Unpublished data, NZG Marine Mammal Database
www.walvisstrandingen.nl
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Harbour porpoise a perspective from documented
strandings Post-1990 strandings age composition
through the year
Assumptions Female gt150 adult Male gt145
adult All lt95 neonate
Unpublished data, NZG Marine Mammal Database
www.walvisstrandingen.nl
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Harbour porpoise a perspective from documented
strandings Conclusions

• Summary from strandings data
• A sharp increase in strandings frequency
• Altering sex-ratio (two periods, pre- and post
  1990s)
• Altering age composition (more juveniles)
• High bycatch rates, notably late winter / spring
• High bycatch rates, notably in juveniles/males
• Acoustics and porpoise mortality.? An open
  question

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Harbour porpoise the need for comprehensive
studies
What is the relevance of all this
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Harbour porpoise international conservation
measures OSPAR, Annex V
OSPAR EcoQualityObjective
Annual bycatch should be less than 1.7 of the
population
For the North Sea, a best abundance estimate of
239,061 harbour porpoises was derived from the
SCANS II survey conducted in July 2005. The
1.7 annual bycatch levels corresponding to this
abundance estimate is 4064 animals.
Bycatch can only reliably be estimated using a
properly designed monitoring scheme that is
independent of the fisheries being checked.
Although several types of fisheries may
occasionally catch harbour porpoises, those that
pose the greatest risk to harbour porpoise
populations are bottom-set gill-nets. Such
fisheries are relatively common throughout the
shallower parts of the North Sea. Bycatch
estimates have been made in most relevant UK,
Danish and Swedish fisheries in the North Sea,
but not in any French, Belgian, Dutch, German or
Norwegian fisheries.
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Concluding remarks

• A local stock of considerable size brings
  responsibilities
• Recent history no porpoises, not much to
  conserve
• Currently many thousands, many issues to
  consider

• Conservation measures are required, but what to
  conserve?
• Knowledge of ecology and reproductive biology
  crucial
• Knowledge of current threats should be thorough
  and balanced, no hypes

• Explanation of recent trends, forecasting future
  issues?
• Ecological data and age/sex structure of the
  population crucial
• Multiple data-sources to be combined
• Large scale studies are required rather than
  national or local approach
• Long-term trends rather than ad-hoc projects

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Thank you