Derby
Crew Member
Somass River Escapement Bulletin
Observations to Oct 25, 2011
OBSERVATIONS:
Stamp falls counting facility has been operational since September 1. During the past week
Chinook adult numbers have ranged from 58 to 320. Coho adults have ranged from 68 to 357
and Sockeye adults have ranged from 0 to 4. Total escapement through Stamp Falls to
October 25 is 25,769 adult Chinook, 46,481 adult Coho and 477 adult Sockeye. Sockeye
escapement through both Great Central Lake and Sproat Lake counters requires further
analysis at this time. No additional data is available at present.
Stamp Falls enumeration has been fully operational so far with no shut downs.
River flows are moderate, and river temperature is 11oC.
2011 EXPECTATIONS:
Sockeye: For 2011, the forecast return of Somass sockeye was upgraded to 1,400,000. The
escapement target for this run size is 513,600, giving a surplus of 886,400 sockeye available for
catch. Expected stock composition is about 48% Great Central, and 52% Sproat Sockeye.
Expected age composition is about 25%, 62%, 7% and 6% for age 42, 52, 53 and 63 adults,
respectively.
Chinook: Approximately 47,600 Somass Chinook are forecast to return to Barkley Sound and
Alberni Inlet in 2011. The predicted adult age composition is 8%, 81% and 11% of 3, 4 and 5-
year olds, respectively. Given the age composition, about 32,500 spawners are required to
meet the 57.2M egg target for the system. Therefore, about 15,000 Somass Chinook are
available for harvest in the ‘terminal fishery’ from Alberni Inlet seaward to Barkley Sound.
Chum: Approximately 565,000 Chum are forecast to return to South West Vancouver Island in
2011, however pre-season forecasts for Chum returns are highly uncertain. Over the last few
years, returns of WCVI Chum have been well below long-term averages and this trend is
expected to continue in 2011.
Coho: For the 2008 brood year, 405,000 coho smolts were released from the Robertson Creek
Hatchery and there were about 39,000 natural spawners. The forecast survival rate of
Robertson Creek/Somass Coho for the 2008 brood year is above average at 8.5%. The total
expected return to Somass system is about 40,000 to 60,000 coho.
PROGRAM OVERVIEW:
Fish counting operations on the Somass system are run by the Hupacasath First Nation in
collaboration with DFO.
To estimate the escapement of Somass Sockeye, automatic fish counters are installed at the
Sproat and Great Central fishways in mid-May. Twice weekly visual calibrations are used to
validate counter data as well as to determine species and age (jacks versus adult) composition
of escapement. A portion of the Sockeye escapement is biologically sampled at the fishways.
Of interest are age at return, sex ratio and fecundity. For Henderson Sockeye, escapement is
estimated through a series of swim surveys of the main spawning habitat (Clemens Creek and
nearby beach habitat). These surveys are conducted in September and October.
Counters are removed from the Great Central fishway in early September when Chinook begin
to migrate upstream. After this, all salmon passing through the Stamp Falls fishway are counted
by trained and experienced observers. They identify fish to species, estimate the portion of
jacks by relative size and estimate the portion of marked (adipose fin clipped) fish. Migration
through the fishway is videotaped for later verification of daytime real-time counts and species
Page 2 of 3
identification and for enumeration of night-time migration. Real-time observations are typically
greater than 95% accurate for counts, species identification and mark rate.
Below, are a series of figures that express 2011 escapement observations relative to average
escapement timing from 1999 to 2010 for Chinook and Coho. Although informative, in some
years observed escapement rate relative to average escapement timing may be a poor
indication of final run abundance. In contrast to ‘run timing’, (the return of Chinook/Coho to
Alberni Inlet) escapement timing tends to be more variable. It is influenced by the impact of
fisheries and environmental conditions, such as river temperature or flow.
Cumulative Daytime Adult Chinook Returns Through Stamp Falls
Observations to Oct 25, 2011
OBSERVATIONS:
Stamp falls counting facility has been operational since September 1. During the past week
Chinook adult numbers have ranged from 58 to 320. Coho adults have ranged from 68 to 357
and Sockeye adults have ranged from 0 to 4. Total escapement through Stamp Falls to
October 25 is 25,769 adult Chinook, 46,481 adult Coho and 477 adult Sockeye. Sockeye
escapement through both Great Central Lake and Sproat Lake counters requires further
analysis at this time. No additional data is available at present.
Stamp Falls enumeration has been fully operational so far with no shut downs.
River flows are moderate, and river temperature is 11oC.
2011 EXPECTATIONS:
Sockeye: For 2011, the forecast return of Somass sockeye was upgraded to 1,400,000. The
escapement target for this run size is 513,600, giving a surplus of 886,400 sockeye available for
catch. Expected stock composition is about 48% Great Central, and 52% Sproat Sockeye.
Expected age composition is about 25%, 62%, 7% and 6% for age 42, 52, 53 and 63 adults,
respectively.
Chinook: Approximately 47,600 Somass Chinook are forecast to return to Barkley Sound and
Alberni Inlet in 2011. The predicted adult age composition is 8%, 81% and 11% of 3, 4 and 5-
year olds, respectively. Given the age composition, about 32,500 spawners are required to
meet the 57.2M egg target for the system. Therefore, about 15,000 Somass Chinook are
available for harvest in the ‘terminal fishery’ from Alberni Inlet seaward to Barkley Sound.
Chum: Approximately 565,000 Chum are forecast to return to South West Vancouver Island in
2011, however pre-season forecasts for Chum returns are highly uncertain. Over the last few
years, returns of WCVI Chum have been well below long-term averages and this trend is
expected to continue in 2011.
Coho: For the 2008 brood year, 405,000 coho smolts were released from the Robertson Creek
Hatchery and there were about 39,000 natural spawners. The forecast survival rate of
Robertson Creek/Somass Coho for the 2008 brood year is above average at 8.5%. The total
expected return to Somass system is about 40,000 to 60,000 coho.
PROGRAM OVERVIEW:
Fish counting operations on the Somass system are run by the Hupacasath First Nation in
collaboration with DFO.
To estimate the escapement of Somass Sockeye, automatic fish counters are installed at the
Sproat and Great Central fishways in mid-May. Twice weekly visual calibrations are used to
validate counter data as well as to determine species and age (jacks versus adult) composition
of escapement. A portion of the Sockeye escapement is biologically sampled at the fishways.
Of interest are age at return, sex ratio and fecundity. For Henderson Sockeye, escapement is
estimated through a series of swim surveys of the main spawning habitat (Clemens Creek and
nearby beach habitat). These surveys are conducted in September and October.
Counters are removed from the Great Central fishway in early September when Chinook begin
to migrate upstream. After this, all salmon passing through the Stamp Falls fishway are counted
by trained and experienced observers. They identify fish to species, estimate the portion of
jacks by relative size and estimate the portion of marked (adipose fin clipped) fish. Migration
through the fishway is videotaped for later verification of daytime real-time counts and species
Page 2 of 3
identification and for enumeration of night-time migration. Real-time observations are typically
greater than 95% accurate for counts, species identification and mark rate.
Below, are a series of figures that express 2011 escapement observations relative to average
escapement timing from 1999 to 2010 for Chinook and Coho. Although informative, in some
years observed escapement rate relative to average escapement timing may be a poor
indication of final run abundance. In contrast to ‘run timing’, (the return of Chinook/Coho to
Alberni Inlet) escapement timing tends to be more variable. It is influenced by the impact of
fisheries and environmental conditions, such as river temperature or flow.
Cumulative Daytime Adult Chinook Returns Through Stamp Falls
