Derby
Crew Member
River sturgeon numbers decline
But conservationists buoyed by catches of three large mature fish
By Randy Shore, Vancouver Sun December 24, 2012
• Story
• Photos ( 1 )
Jeff Welch, left, lead guide for Great River Fishing Adventures, and Dean Werk, owner of Great River hold a 500-kilo great white sturgeon caught in September in the Fraser River.
Photograph by: The Canadian Press, Files , Vancouver Sun
The population of Fraser River white sturgeon is at its lowest level since 2001, when conservationists began counting and tagging the fish.
Estimates contained in the annual Lower Fraser White Sturgeon Monitoring and Assessment Program report suggest that the number of sturgeon in the river in 2011 dropped below 45,000 fish, a 23-per-cent decline since the population peaked at 58,090 in 2003.
The greatest decline was among juvenile sturgeon less than one metre in length, while the population of mid-sized fish was relatively stable.
"There are a lot of factors at play (in the population estimates) because these are very long-lived fish - they can live up to 200 years and grow up to 20 feet (six metres) long," said Sarah Schreier, executive director of the Fraser River Sturgeon Conservation Society. "We have seen a steady decline, but in the past five years the population has been holding steady and that gives us a lot of hope these fish will mature and spawn."
Sturgeon don't reach sexual maturity until they are between 26 and 36 years old and may only spawn every six to 10 years, Schreier said. But their longevity allows them to endure years of poor spawning conditions and still survive to reproduce.
Despite the gloomy numbers, conservationists were buoyed by news that three very large sturgeon were hooked and released by anglers this year.
Two sturgeon measuring 3.25 m and 3.21 m were caught and released earlier in the year.
A sturgeon weighing 500 kilos and 3.40 m in length was landed by a sport fisherman near Chilliwack in September. It was the fourth largest sturgeon recorded in the 12-year study period.
In 90,000 sturgeon encounters recorded by the group's monitoring program, only about a dozen fish longer than three metres have been noted. During the peak of the commercial sturgeon fishery between 1892 and 1920, sturgeon measuring up to six metres were routinely pulled from the Fraser River.
"There are still big old fish in the river and we know that they spawn," Schreier said. "Those three fish were very inspiring; it's very rare for us to see them."
There are indications that conditions in the river and the white sturgeon's ocean habitat has not been optimal for most of the last seven years. The average growth rates for all size groups recorded in the five years starting in 2005 were 23-per-cent lower than the five-year period before 2005.
Growth rates partly recovered in 2010 and 2011, though they are still below the pre-2005 rate.
The Fraser River sturgeon fishery was shut down and converted to catch-and-release in the early 1990s, but a largely unexplained die-off of mature fish in 1993 further hobbled the population.
"There were dozens of (dead) fish and that really alarmed folks, so our organization was founded to get a handle on that population and to protect and restore the sturgeon habitat on the river," Schreier said.
The life cycle and migration habits of the Fraser River white sturgeon remain largely opaque to researchers, but they are known to spend part of their lives in the ocean, mainly in the summer. Sturgeon are known to feed on oolichan and salmon and may be sensitive to fluctuations in the populations of those fish in the ocean and in the river, where they return to spawn.
The conditions sturgeon require for spawning are also mysterious, though eggs have been collected consistently in specific parts of the river.
Because of the sturgeon's lengthy spawning cycle and the long period before the fish reach sexual maturity, Schreier thinks the natural recovery of the Fraser River sturgeon to pre-fishery abundance could take 300 years.
rshore@vancouversun.com
Read more: http://www.vancouversun.com/technol...bers+decline/7740125/story.html#ixzz2G5O0fXzr
But conservationists buoyed by catches of three large mature fish
By Randy Shore, Vancouver Sun December 24, 2012
• Story
• Photos ( 1 )
Jeff Welch, left, lead guide for Great River Fishing Adventures, and Dean Werk, owner of Great River hold a 500-kilo great white sturgeon caught in September in the Fraser River.
Photograph by: The Canadian Press, Files , Vancouver Sun
The population of Fraser River white sturgeon is at its lowest level since 2001, when conservationists began counting and tagging the fish.
Estimates contained in the annual Lower Fraser White Sturgeon Monitoring and Assessment Program report suggest that the number of sturgeon in the river in 2011 dropped below 45,000 fish, a 23-per-cent decline since the population peaked at 58,090 in 2003.
The greatest decline was among juvenile sturgeon less than one metre in length, while the population of mid-sized fish was relatively stable.
"There are a lot of factors at play (in the population estimates) because these are very long-lived fish - they can live up to 200 years and grow up to 20 feet (six metres) long," said Sarah Schreier, executive director of the Fraser River Sturgeon Conservation Society. "We have seen a steady decline, but in the past five years the population has been holding steady and that gives us a lot of hope these fish will mature and spawn."
Sturgeon don't reach sexual maturity until they are between 26 and 36 years old and may only spawn every six to 10 years, Schreier said. But their longevity allows them to endure years of poor spawning conditions and still survive to reproduce.
Despite the gloomy numbers, conservationists were buoyed by news that three very large sturgeon were hooked and released by anglers this year.
Two sturgeon measuring 3.25 m and 3.21 m were caught and released earlier in the year.
A sturgeon weighing 500 kilos and 3.40 m in length was landed by a sport fisherman near Chilliwack in September. It was the fourth largest sturgeon recorded in the 12-year study period.
In 90,000 sturgeon encounters recorded by the group's monitoring program, only about a dozen fish longer than three metres have been noted. During the peak of the commercial sturgeon fishery between 1892 and 1920, sturgeon measuring up to six metres were routinely pulled from the Fraser River.
"There are still big old fish in the river and we know that they spawn," Schreier said. "Those three fish were very inspiring; it's very rare for us to see them."
There are indications that conditions in the river and the white sturgeon's ocean habitat has not been optimal for most of the last seven years. The average growth rates for all size groups recorded in the five years starting in 2005 were 23-per-cent lower than the five-year period before 2005.
Growth rates partly recovered in 2010 and 2011, though they are still below the pre-2005 rate.
The Fraser River sturgeon fishery was shut down and converted to catch-and-release in the early 1990s, but a largely unexplained die-off of mature fish in 1993 further hobbled the population.
"There were dozens of (dead) fish and that really alarmed folks, so our organization was founded to get a handle on that population and to protect and restore the sturgeon habitat on the river," Schreier said.
The life cycle and migration habits of the Fraser River white sturgeon remain largely opaque to researchers, but they are known to spend part of their lives in the ocean, mainly in the summer. Sturgeon are known to feed on oolichan and salmon and may be sensitive to fluctuations in the populations of those fish in the ocean and in the river, where they return to spawn.
The conditions sturgeon require for spawning are also mysterious, though eggs have been collected consistently in specific parts of the river.
Because of the sturgeon's lengthy spawning cycle and the long period before the fish reach sexual maturity, Schreier thinks the natural recovery of the Fraser River sturgeon to pre-fishery abundance could take 300 years.
rshore@vancouversun.com
Read more: http://www.vancouversun.com/technol...bers+decline/7740125/story.html#ixzz2G5O0fXzr
