---------- Forwarded message ----------
Date: Sat, 1 Sep 2001 05:02:59 -0700
From: MARMAM Editors <marmamed@uvic.ca>
Reply-To: Marine Mammals Research and Conservation Discussion
<MARMAM@UVVM.UVIC.CA>
To: MARMAM@UVVM.UVIC.CA
Subject: Abstract: inter-annual variation in harbour seal diet (fwd)
Interannual variation in the summer diets of harbour seals Phoca vitulina at
Mousa, Shetland (UK)
Brown, E.G., Pierce, G.J., Hislop, J.R.G. & Santos, M.B. (2001) Journal of
the Marine Biological Association of the UK, 81, 325-337.
ABSTRACT
The main prey species in the summer (July-September) diets of harbour seals
(Phoca vitulina) on the Island of Mousa (Shetland, UK), 1994-1997, were
whiting (Merlangius merlangus), herring (Clupea harengus), sandeel
(Ammodytidae) and garfish (Belone belone). Norway pout (Trisopterus
esmarkii) was numerically important but comprised no more than 11% of prey
weight in any one year. There were marked between-year fluctuations in the
relative importance of these prey, with whiting comprising 16-34% (by
weight) of the diet, herring 12-28%, sandeels 7-18% and garfish 7-22%.
Additional data on spring (April-June) diet were available for 1995-1997:
sandeels were the most important prey (% weight) in all three years (51-60%
of the diet), while herring (8-48%) and gadids (2-22%) varied in importance.
The average size of fish eaten was larger than that reported in comparable
studies from other areas. Harbour seals appear to have selected larger
sandeels, whiting, and Norway pout than the average size available in the
area, as indicated by survey trawls, although between-year changes in the
size of Norway pout in the diet did to some extent reflect availability.
Interannual variation in the importance of Norway Pout in the diet appeared
to track trends in abundance, although the short time series precluded
detection of a statistically significant correlation. Thus, some of our
results are consistent with harbour seals feeding opportunistically while
others point to selectivity, particularly for prey size. Estimated
consumption of fish by the 500 harbour seals on Mousa during summer ranged
from 152-195 tonnes.
Reprint requests to:
Edward G. Brown
9 Twageos Rd
Lerwick
Shetland
ZE1 0BB
Scotland, U.K.
Email: e.brown@ssmg.shetland.co.uk
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