Marine Awareness North Wales, Wildlife Trust harbor porpoise baseline surveys on the north coast of Anlesey, Wales, UK

Richard Shucksmith

Dataset credit

Richard Shucksmith, Nia H. Jones, George W. Stoyle, Andrew Davies and Emily F. Dicks


Primary contact Richard Shucksmith The Scottish Association for Marine Science
Data entry Andrew DiMatteo US Dept. of the Navy Naval Facilities Engineering Command Atlantic


Shucksmith, R. 2011. Marine Awareness North Wales, Wildlife Trust harbor porpoise baseline surveys on the north coast of Anlesey, Wales, UK. Data downloaded from OBIS-SEAMAP ( on yyyy-mm-dd.


A three year study was undertaken during 2002 to 2004 from May to September to estimate abundance and density of harbor porpoises on the north coast of Anglesey, Wales, United Kingdom. There were no ecological data regarding the harbor porpoises in Anglesey waters so the ability to influence conservation measures was highly constrained. Boat-based transects using distance sampling techniques were applied so a robust estimate of density and abundance could be attained. The study area consisted of a block approximately 489 km2 extending from the east of Point Lynas to the west of South Stack on north coast of Anglesey. The study area was divided into five blocks consisting of 31 perpendicular transect lines to the shore. Each of the transect lines were surveyed 1–5 times by the end of the three year study. Based on the assumption that g(0) = 1 the density of harbor porpoises for the 489 km2 study site was estimated to be 0.630 individuals/km2 (CV = 0.20) and the abundance is estimated to be 309 individuals (CV = 0.20). Heterogeneity in density and abundance was observed across the five blocks which showed Point Lynas and South Stack to have the highest densities. This distribution was closely associated to fine-scale oceanographic features which cause prey to be concentrated and may facilitate foraging for harbor porpoises. The study showed that Anglesey provides coastal habitats for the harbor porpoise and was the first study of this kind in North Wales, United Kingdom.


The need for abundance and density estimates was highlighted as a key factor in the conservation and management of the harbor porpoise in Anglesey waters. Moreover, proposed extension of the wind farms from Liverpool Bay to Anglesey and the potential of the area for marine renewable energy devices presented a problem to managers and planners due to the lack of knowledge of harbor porpoise populations in north Wales.

Supplemental information

Among tracklines, two lines were removed as either start or end time was not recorded. These are: 6/08/2003 starting 16:23, and 9/08/2003 ending 16:02.




This section explains attributes included in the original dataset. OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only. Should you need other attributes described here, you are encouraged to contact the data provider.

Attributes described below represent those in the original dataset provided by the provider.
Only minimum required attributes are visible and downloadable online. Other attributes may be obtained upon provider's permission.

Attributes in dataset

Attribute (table column)Description
oidUnique ID number (generated by SEAMAP)
obs_dateObserved date
obs_timeObserved time
latitudeLatitude of observation
longitudeLongitude of observation
sp_obsSpecies observed
sp_tsnSpecies ITIS TSN
obs_countsum of adult, juvenile and calf counts
transectnotransect number
startlatdtransect start latitude degree
startlatmstransect start latitude minutes
startlondtransect start longitude degree
startlonmstransect start longitude minutes
endlatdtransect end latitude degree
endlatmstransect end latitude minutes
endlondtransect end longitude degree
endlonmstransect end longitude minutes
no_adnumber of adults
no_juvnumber of juveniles
no_calfnumber of calves
psport or starboard
proc_notesprocessing notes
Marine mammals214
Sea turtles0
Rays and sharks0
Other species0
Non spatial0
Non species0
Date, Begin2002-07-07
Date, End2004-09-09
Temporal prec.111111
Latitude53.26 - 53.50
Longitude-4.83 - -4.20
Coord. prec.4 decimal digits
Data typeAnimal sighting
EffortYES (ID: 707)
Traveled (km)911
Effort hours75
Contr. through
Sharing policy CC-BY-NC (Minimum)
Shared with OBIS
GBIF (via DOI)
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See metadata in FGDC XML
See download history / statistics