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

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

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.

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.

Overview

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
oid	Unique ID number (generated by SEAMAP)
obs_date	Observed date
obs_time	Observed time
latitude	Latitude of observation
longitude	Longitude of observation
sp_obs	Species observed
sp_tsn	Species ITIS TSN
obs_count	sum of adult, juvenile and calf counts
effort_id
input_by
boat_name
transectno	transect number
startlatd	transect start latitude degree
startlatms	transect start latitude minutes
startlond	transect start longitude degree
startlonms	transect start longitude minutes
endlatd	transect end latitude degree
endlatms	transect end latitude minutes
endlond	transect end longitude degree
endlonms	transect end longitude minutes
no_ad	number of adults
no_juv	number of juveniles
no_calf	number of calves
ps	port or starboard
distance
bearing
wind
sea
swell
cloud
precip	precipitation
visibility
proc_notes	processing notes