Post by AgMD on Aug 4, 2011 18:37:18 GMT -5
A recent post on this board and some PM's between Henry and myself, has prompted me to make this post.
This is the time of the year that the rivers are running warm. This last Mon. I read the Hoosic at 76* F. The previous week it was 78*F.
Trout are a cold water fish and their metabolism peaks in the mid to high 60*'s. That is when they digest food fastest and eat more -- and when the fishin' is really good. The upper limit for brown trout is held to be at 77*F. This is the point that 50% of brown trout will die. It is easy to see that even at temps. below 77*F the fish are stressed. Part of this response to warm temperatures is related to oxygen levels. As the water gets warmer it's ability to carry dissolved oxygen is diminished. Diminished oxygen levels results in slower metabolism and physical activity becomes difficult and the fish is exhausted easily. This is a lot like the physical stress experienced by mountain climbers at high altitude. In both cases, the climber or fish is slowly suffocating to death. The added stress of being caught produces acidosis of the blood which the fish cannot correct due to the diminished metabolism. This can be, and often is fatal to the fish.
How do trout survive at temps of 77*F and above? Spring seeps, feeder streams and rough water. The rivers in our area have a lot of cold water seeping in from under ground sources. This water is usually at 55*F, more or less. Small feeder streams that are well shaded and come from the the shaded side of the hills can be nearly as cold as ground water. You can find places in most of our rivers, where trout are "schooled" up in little pockets where there is a feeder stream or spring. Rough water, rapids, falls and dams also increase the dissolved oxygen level and so as the river starts to warm we will see the trout move into positions just below these types of features.
At what temperature should we stop fishing? The most common answer seems to be 70*F. I myself have stretched that one or two degrees but only in water where I know the water is exceptionally well oxygenated by a dam or falls.
Although we may keep a fish or two, now and again, it seems that most of us practice C&R. If the whole point of C&R is to preserve the fish so that we preserve the fishing, then C&R at temps over 70*F makes no sense.
AgMD
This is the time of the year that the rivers are running warm. This last Mon. I read the Hoosic at 76* F. The previous week it was 78*F.
Trout are a cold water fish and their metabolism peaks in the mid to high 60*'s. That is when they digest food fastest and eat more -- and when the fishin' is really good. The upper limit for brown trout is held to be at 77*F. This is the point that 50% of brown trout will die. It is easy to see that even at temps. below 77*F the fish are stressed. Part of this response to warm temperatures is related to oxygen levels. As the water gets warmer it's ability to carry dissolved oxygen is diminished. Diminished oxygen levels results in slower metabolism and physical activity becomes difficult and the fish is exhausted easily. This is a lot like the physical stress experienced by mountain climbers at high altitude. In both cases, the climber or fish is slowly suffocating to death. The added stress of being caught produces acidosis of the blood which the fish cannot correct due to the diminished metabolism. This can be, and often is fatal to the fish.
How do trout survive at temps of 77*F and above? Spring seeps, feeder streams and rough water. The rivers in our area have a lot of cold water seeping in from under ground sources. This water is usually at 55*F, more or less. Small feeder streams that are well shaded and come from the the shaded side of the hills can be nearly as cold as ground water. You can find places in most of our rivers, where trout are "schooled" up in little pockets where there is a feeder stream or spring. Rough water, rapids, falls and dams also increase the dissolved oxygen level and so as the river starts to warm we will see the trout move into positions just below these types of features.
At what temperature should we stop fishing? The most common answer seems to be 70*F. I myself have stretched that one or two degrees but only in water where I know the water is exceptionally well oxygenated by a dam or falls.
Although we may keep a fish or two, now and again, it seems that most of us practice C&R. If the whole point of C&R is to preserve the fish so that we preserve the fishing, then C&R at temps over 70*F makes no sense.
AgMD