Salmon and herring populations off southwest
Vancouver Island will suffer next year and
the year after because of the persistence of
unusually warm temperatures in the ocean,
warns a State of the Oceans report, released
Wednesday by Fisheries and Oceans Canada.
"A lot of the fish we have here live a long
time so they're adapted to periods of warm
water and periods of cold water and they do
just fine through those. What they're not
adapted to are these long periods of really
warm conditions," said Ian Perry, one of the
report's authors and a biologist at the
Pacific Biological Station in Nanaimo.
Warmer sea temperatures reduce the mixing of
nutrients and cut the production of
phytoplankton, which are the bottom of the
food chain. While the temperature change is
bad news for salmon, which prefer cooler
water, it's good news for other fish species
such as sardines and Pacific hake, the
report said.
The warmer water means predators will likely
eat young salmon emerging from the rivers,
reducing the numbers able to return and
spawn, Perry said.
Warm oceans will also lead to the planet
getting warmer, said Perry, "because the
oceans store heat. And even though the
atmosphere might cool, that heat is still
going to be in the ocean. It takes a long
time for it to cool down."
Waters off B.C. are attracting species that
normally live off the California coast, such
as sardines, mackerel and a voracious eater
of many fish, the Humboldt squid, said
Perry.
Scientists are surprised that the oceans
have stayed warm for the past three years.
"We had actually expected it to cool," said
Perry, noting a strong cool period lasted
from 1999 through 2001.
"We thought we were going back to conditions
that were good for salmon and that we've
seen through the 1980s and early 1990s.
"The surprise has been that 2003, 2004 and
2005 have all gone back to warm conditions."
Sea temperatures off B.C. down to 175 metres
in depth remain 0.5 to 5 degrees Celsius
warmer than in 1990-1996, the report said.
The warming trend puts the sea temperature
off Tofino at 13 to 14 degrees Celsius, said
Perry.
The temperature of oceans globally last year
was slightly cooler than in 2004 but still
ranked as the seventh-warmest year on record
since 1880. The ocean has been warming on
average by 0.13 degrees Celsius per decade
since 1880.
"Warm conditions mean things are going to be
different than we have had them in the
past," said Perry.
IN HOTTER WATER
- On an annual basis, the Pacific coast was
warmer and drier than normal in 2005.
- Sea temperatures maintained warm
conditions in 2005 in all B.C. marine
ecosystems.
- Warm sea temperatures reduced the supply
of plant nutrients into surface layers of
the Pacific Ocean, thus reducing the
production of phytoplankton, which is the
base of the marine food web.
- The growth of juvenile coho salmon on the
west coast of Vancouver Island during spring
to fall was the lowest since these
observations began in 1998.
- Warm-weather migratory species such as
Pacific hake and Pacific sardine were
abundant in B.C. waters during 2005.
Other warm-water species not typically seen in B.C were also spotted.
Other warm-water species not typically seen in B.C were also spotted.
Source: State of the Oceans 2005