October 19, 2018 at 2:00 pm
[caption id="attachment_3165" align="alignright" width="500"]
A nice, healthy Sebago salmon. The Crooked River weir is providing MDIFW fisheries biologists with valuable insight into the health and numbers of Sebago's wild salmon.[/caption]
By MDIFW Fisheries Biologist Brian Lewis
Several years ago, the Sebago Lakes region purchased a portable steel picket weir with the intention of setting it up periodically on the lower Crooked River to monitor the size and duration of the annual landlocked salmon spawning migration. These salmon migrate as far as 60 miles up the river from Sebago Lake each fall to spawn, but the actual number of individuals running up the river and their fate has not been comprehensively investigated since the removal of the Bolsters Mill dam and fish trap in 1982. The actual deployment of the weir had to be postponed due to a temporary lack of staffing, but I am happy to report the temporary weir is now in place on the river and functional.
This temporary weir is a simple design that uses a row of metal pipes to direct migrating salmon to a funnel, which then passes the fish into a large holding pen. Once in the pen, the salmon can’t easily find the entrance to the funnel and so remain in the holding pen until released upstream by regional biologists. The weir was installed in mid-August when river water temperatures were still close to 70 degrees Fahrenheit. We didn’t begin to see salmon in the trap until water temperatures dropped into the 60’s and didn’t see them in numbers until the water temperature dropped into the 50’s. To minimize stress on migrating salmon, handling was minimized when the water temperature was over 63 degrees by simply releasing them from the holding pen with a quick head count. The weir will be removed after the salmon migration has slowed.
The first notable catch of salmon from the weir occurred on September 12th and in the ensuing few weeks we have captured and passed upstream over 1,700 landlocked salmon. Salmon sizes have ranged from a 10-inch precocial male to a 26-inch hook jaw monster, but the average fish has been around 18 inches long. Water temperature permitting, a portion of these fish are measured, weighed, and a scale sample is taken to determine age. A further subset of salmon are electronically tagged with Passive Integrated Transponder (PIT) tag to monitor their movements as they migrate, spawn, and then drop out of the river and back into Sebago Lake.
The ultimate purpose of the weir is to answer questions that will help biologists manage the Sebago Lake wild salmon fishery and the associated wild salmon migration, which ultimately contributes around 80% of the salmon caught in Sebago Lake. The most obvious question is how many individuals comprise the current migration and how that compares to the migrations of the 1970s and early 1980s. Also important is collecting age and growth data of wild salmon, which can tell us how fast fish are growing, how long the young stay in the river before dropping into the lake, and how long it takes a wild salmon to reach legal size. Further questions involve determining the timing of the spawning migration and the timing of their return to the lake. Also of interest is the question of how many salmon do not return to the lake after spawning due to either mortality or possibly even overwintering within the Crooked River.
As you can see there are a lot of questions to be answered, but the most exciting part is that we have the opportunity to collect more data on wild Sebago Lake salmon in the next three months than biologists have been able to collect in the last three decades. The weir is scheduled for removal in November, though fish tracking efforts will continue into December and is expected to resume in the spring of 2019. We anticipate collecting enough data to keep us in learning mode for some time to come!
Editor’s Note: Last Friday, a volunteer discovered 12 dead salmon on top of the fish collection box at the Crooked River weir. Based upon initial findings, game wardens feel this could be an intentional act and are actively investigating this incident. The weir has been in place for eight weeks and during that time over 1,700 salmon have passed through the weir. The weir has and will continue to provide MDIFW with valuable information on wild landlocked salmon migrations, growth rates, and the overall health of the Sebago Lake and Crooked River fishery. Anyone with information that might help game wardens are being asked to call Public Safety dispatch at (207) 624-7076 or Maine Operation Game Thief at 1-800-ALERT-US.
[caption id="attachment_3166" align="alignleft" width="861"]
A view of the temporary weir from the upstream side.[/caption]
A nice, healthy Sebago salmon. The Crooked River weir is providing MDIFW fisheries biologists with valuable insight into the health and numbers of Sebago's wild salmon.[/caption]
By MDIFW Fisheries Biologist Brian Lewis
Several years ago, the Sebago Lakes region purchased a portable steel picket weir with the intention of setting it up periodically on the lower Crooked River to monitor the size and duration of the annual landlocked salmon spawning migration. These salmon migrate as far as 60 miles up the river from Sebago Lake each fall to spawn, but the actual number of individuals running up the river and their fate has not been comprehensively investigated since the removal of the Bolsters Mill dam and fish trap in 1982. The actual deployment of the weir had to be postponed due to a temporary lack of staffing, but I am happy to report the temporary weir is now in place on the river and functional.
This temporary weir is a simple design that uses a row of metal pipes to direct migrating salmon to a funnel, which then passes the fish into a large holding pen. Once in the pen, the salmon can’t easily find the entrance to the funnel and so remain in the holding pen until released upstream by regional biologists. The weir was installed in mid-August when river water temperatures were still close to 70 degrees Fahrenheit. We didn’t begin to see salmon in the trap until water temperatures dropped into the 60’s and didn’t see them in numbers until the water temperature dropped into the 50’s. To minimize stress on migrating salmon, handling was minimized when the water temperature was over 63 degrees by simply releasing them from the holding pen with a quick head count. The weir will be removed after the salmon migration has slowed.
The first notable catch of salmon from the weir occurred on September 12th and in the ensuing few weeks we have captured and passed upstream over 1,700 landlocked salmon. Salmon sizes have ranged from a 10-inch precocial male to a 26-inch hook jaw monster, but the average fish has been around 18 inches long. Water temperature permitting, a portion of these fish are measured, weighed, and a scale sample is taken to determine age. A further subset of salmon are electronically tagged with Passive Integrated Transponder (PIT) tag to monitor their movements as they migrate, spawn, and then drop out of the river and back into Sebago Lake.
The ultimate purpose of the weir is to answer questions that will help biologists manage the Sebago Lake wild salmon fishery and the associated wild salmon migration, which ultimately contributes around 80% of the salmon caught in Sebago Lake. The most obvious question is how many individuals comprise the current migration and how that compares to the migrations of the 1970s and early 1980s. Also important is collecting age and growth data of wild salmon, which can tell us how fast fish are growing, how long the young stay in the river before dropping into the lake, and how long it takes a wild salmon to reach legal size. Further questions involve determining the timing of the spawning migration and the timing of their return to the lake. Also of interest is the question of how many salmon do not return to the lake after spawning due to either mortality or possibly even overwintering within the Crooked River.
As you can see there are a lot of questions to be answered, but the most exciting part is that we have the opportunity to collect more data on wild Sebago Lake salmon in the next three months than biologists have been able to collect in the last three decades. The weir is scheduled for removal in November, though fish tracking efforts will continue into December and is expected to resume in the spring of 2019. We anticipate collecting enough data to keep us in learning mode for some time to come!
Editor’s Note: Last Friday, a volunteer discovered 12 dead salmon on top of the fish collection box at the Crooked River weir. Based upon initial findings, game wardens feel this could be an intentional act and are actively investigating this incident. The weir has been in place for eight weeks and during that time over 1,700 salmon have passed through the weir. The weir has and will continue to provide MDIFW with valuable information on wild landlocked salmon migrations, growth rates, and the overall health of the Sebago Lake and Crooked River fishery. Anyone with information that might help game wardens are being asked to call Public Safety dispatch at (207) 624-7076 or Maine Operation Game Thief at 1-800-ALERT-US.
[caption id="attachment_3166" align="alignleft" width="861"] A view of the temporary weir from the upstream side.[/caption]Categories