Atlantic salmon are among the most imperiled species in the Northeast Region. While at one time hundreds of thousands of salmon made their epic migration from the oceans of Greenland to their natal rivers in Maine, now only remnant populations remain. Recovering this iconic species is a priority for the U.S. Fish and Wildlife Service.
The odds have been against the salmon. The construction of dams, overfishing, habitat loss, and water pollution have collectively caused their decline.
Biologists at the Craig Brook National Fish Hatchery, part of the Atlantic salmon recovery operation that Santavy oversees, are experimenting with ways to delay the spawning cycle that they’re seeing in the Penobscot River salmon. By artificially manipulating water temperatures and length of daylight they are attempting to bring the captive fish more in sync with seasonal river conditions. Hatchery-raised fish comprise 95-percent of the salmon population in the Penobscot.
Adult Atlantic salmon. Credit: Bob Michelson Adult Atlantic salmon. Credit: Bob Michelson
An additional concern in recovering the Atlantic salmon is that the rivers in the Downeast region of Maine are experiencing extreme fluctuations in water flows – heavier rainfalls happening less frequently, combined with earlier snow and melting river ice – that have been predicted in certain climate change models. During these weather events, the high-flowing water doesn’t have a chance to absorb into the river beds, which contain minerals that serve as a buffer to changing water chemistry. This lack of buffering can increase the acidity of the water. After the rainwater flushes out the system, river flows now tend to decrease rapidly unlike the gradual decline seen in the past.
According to Santavy, these shifting river conditions occur at a time in the spring when the juvenile salmon are very vulnerable. In the wild, the fish have just a one-month window of time to transform from parr into smolt before migrating to the sea.
Biological studies conducted by the U.S. Geological Survey (U.S.G.S.) show that it can take weeks for a salmon in this life stage to recover after being exposed to acidic conditions. Acidic pH levels in the water lower than 6 (7 is neutral) can cause naturally occurring aluminum levels in the water to become reactive to the fish. This can prevent calcium from binding to the fishes’ gills – a necessary process for their transition to the marine environment. If this is the case, Santavy says it could help explain the reason smolt are being lost in the estuaries, and would be devastating to recovery efforts.
The odds have been against the salmon. The construction of dams, overfishing, habitat loss, and water pollution have collectively caused their decline.
Biologists at the Craig Brook National Fish Hatchery, part of the Atlantic salmon recovery operation that Santavy oversees, are experimenting with ways to delay the spawning cycle that they’re seeing in the Penobscot River salmon. By artificially manipulating water temperatures and length of daylight they are attempting to bring the captive fish more in sync with seasonal river conditions. Hatchery-raised fish comprise 95-percent of the salmon population in the Penobscot.
Adult Atlantic salmon. Credit: Bob Michelson Adult Atlantic salmon. Credit: Bob Michelson
An additional concern in recovering the Atlantic salmon is that the rivers in the Downeast region of Maine are experiencing extreme fluctuations in water flows – heavier rainfalls happening less frequently, combined with earlier snow and melting river ice – that have been predicted in certain climate change models. During these weather events, the high-flowing water doesn’t have a chance to absorb into the river beds, which contain minerals that serve as a buffer to changing water chemistry. This lack of buffering can increase the acidity of the water. After the rainwater flushes out the system, river flows now tend to decrease rapidly unlike the gradual decline seen in the past.
According to Santavy, these shifting river conditions occur at a time in the spring when the juvenile salmon are very vulnerable. In the wild, the fish have just a one-month window of time to transform from parr into smolt before migrating to the sea.
Biological studies conducted by the U.S. Geological Survey (U.S.G.S.) show that it can take weeks for a salmon in this life stage to recover after being exposed to acidic conditions. Acidic pH levels in the water lower than 6 (7 is neutral) can cause naturally occurring aluminum levels in the water to become reactive to the fish. This can prevent calcium from binding to the fishes’ gills – a necessary process for their transition to the marine environment. If this is the case, Santavy says it could help explain the reason smolt are being lost in the estuaries, and would be devastating to recovery efforts.
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