Seabird Oiling and By-Catch

Scientific Research on Triangle Island

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Recent analyses indicate that the Common Murre is one of the species most often killed as a result of fisheries bycatch and chronic oiling in waters off the British Columbia coast. This has raised concerns about the population-level effects of this mortality, still basically unquantified, on murres in the P&Y Region. And we know that numbers in neighbouring Washington State have been declining for at least the last decade, with high rates of bycatch possibly contributing to the declines.

More than 95% of all murres that breed in BC have historically bred in the immediate vicinity of Triangle Island (the majority on Puffin Rock), so the population status of Common Murres at Triangle is essentially equivalent to their status in the entire Region. A couple of questions present themselves:

What is the population status of Common Murres at Triangle Island,
and elsewhere in BC?

And if the population is declining, is anthropogenic mortality
due to bycatch and/or oiling an important factor?

To answer these questions, we began a demographic study of Common Murres at Triangle Island in 2002, and have been monitoring annual variation in vital rates (adult survival and breeding success), as well as chick diets and growth rates. In addition, in summer 2003 we resurveyed all murre breeding sites around Triangle Island, and made comparisons with results of a 1989 survey conducted by CWE graduate Dr. Michael Rodway.
What have we found?
Results of the 2003 survey suggest that Common Murres have abandoned satellite colonies at Castle Rock and Murre Rock, and now are breeding at much higher densities on the main colony at Puffin Rock. However, numbers in 2003 were down about 25% overall from 1989. Interestingly, conditions for breeding, as judged by adult mass dynamics, reproductive success, and chick growth rates, appear to be very favourable for murres at Triangle. If that is the case, any population declines may well be being driven by factors operating outside the breeding season.
We will continue to monitor the situation at Triangle. Additionally, in collaboration with partners in 2003 and 2004 we conducted a complete survey of all historical murre colonies in the P&Y Region. As can be seen in the table below, murres were absent from several sites where they bred in previous years. This survey data will be critical in making appropriate recommendations on management of Common Murre populations in British Columbia.
Colony
Survey Date
 No. of Common Murres Previous Estimate (year)
Kerouard Islands
24 June 2004
 377 400 (1987)
Triangle Island (total)
2003, 2004
 4327 5937 (1989)
Southeast Point
18 Jul 2003
 0 568
Puffin Rock
18 Jul 2003
 4297 3370
Murre Rock
18 Jul 2003
 30 987
Castle Rock
2003, 2004
 0 1012
Sartine Island
9 Jul 2004
 0 600 (1975)
Cleland Island
6 Jul 2004
 0 8 pairs (1975)
Florencia Island
30 Jun 2004
 0 1 pair (1969)
Starlight Reef
30 Jun 2004
 0 2 pairs (1980)
TOTAL
4704