08-30-2019, 02:06 PM
What all of you need to remember is that you are looking at an average. A major problem with an average is that often times there are no individuals that actually fit the average!
You guys are assuming that fish growth is determinate, and that fish will always grow larger over the course of their life. In a good, healthy, system they should. The problem with most of this line of thinking is that anglers want size to be the result of time. ie: a fish will grow to x inches in y years.
This model is flawed. Because fish are indeterminate growers. They experience periods of growth, which might be + and might be -.
So, how do you grow large fish if you don't manage them based on time?
You must look at those growth rates, and figure out how to maximize how much time a fish spends in that period of maximum growth. This doesn't mean that you have to "let the small fish go so that they can grow bigger". What this means is that you have to manipulate the overall population so that the entire population - both small fish and big fish - are in that zone of maximum growth.
the overall system must be healthy to accomplish this. You cannot accomplish this simply by "feeding" the fish more food. If the population is out-of-whack, then adding more food simply compounds the out-of-whack problem (ie: more food = better reproduction = higher densities of fish = slow growth rates = more small fish).
Look at this growth curve:
![[Image: qEBhHYW.jpg?1]](https://i.imgur.com/qEBhHYW.jpg?1)
You want your fish populations somewhere in the middle, in that zone of maximum growth. This is where fish sizes explode. Fish are growing like crazy. You have enough harvest, but not too much (either by anglers or other natural means of mortality).
Think about trout lakes for a minute. When they get overrun with chubs growth rates of trout decrease significantly. If you add more food for the trout, you just increase the carrying capacity of fish and increase the population, which drives average size down. So, instead, you poison the lake and eliminate all the fish (chubs + trout). Now the lake has 0 fish, and the lake has a boom in nutrients, zooplankton, aquatic insects, etc. Now you restock it with trout -- and guess what? Growth rates explode! Those trout, as we've seen in places like Yuba, Piute, Panguitch, after a rotenone treatment, grow big fast!
We see this all the time with brook trout on the Boulder. After a partial winterkill the remaining fish experience fast growth rates and get large fast! What we do NOT want with these fish is for them to get "old". If they are getting old it means their population numbers are staying high, which means more fish survive, which means growth rates slow, which means average size goes down -- and those trophy sized fish disappear. We do not want old fish. We want fish that are growing fast!
So, the real question that you guys need to figure out with the catfish isn't how old they are, or what their average inches per year over the life of the fish is. The question you need to find out is: what are their current growth rates? Find out the "K" factor.
Find out what can be done to increase the growth rate. Most likely the answer would be to remove more fish. Any fish. White bass. Carp. Suckers. Catfish. Any of them. Harvest more -- I'm pretty sure those fisheries are currently not overharvested. Take more fish out and increase growth rates. Increased growth rates = big fish.
Than, like wormandbobber said, the space occupied by that 15 year old fish that you just harvest will immediately be replaced by another fish that experienced high growth rates, which means another big fish.
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You guys are assuming that fish growth is determinate, and that fish will always grow larger over the course of their life. In a good, healthy, system they should. The problem with most of this line of thinking is that anglers want size to be the result of time. ie: a fish will grow to x inches in y years.
This model is flawed. Because fish are indeterminate growers. They experience periods of growth, which might be + and might be -.
So, how do you grow large fish if you don't manage them based on time?
You must look at those growth rates, and figure out how to maximize how much time a fish spends in that period of maximum growth. This doesn't mean that you have to "let the small fish go so that they can grow bigger". What this means is that you have to manipulate the overall population so that the entire population - both small fish and big fish - are in that zone of maximum growth.
the overall system must be healthy to accomplish this. You cannot accomplish this simply by "feeding" the fish more food. If the population is out-of-whack, then adding more food simply compounds the out-of-whack problem (ie: more food = better reproduction = higher densities of fish = slow growth rates = more small fish).
Look at this growth curve:
You want your fish populations somewhere in the middle, in that zone of maximum growth. This is where fish sizes explode. Fish are growing like crazy. You have enough harvest, but not too much (either by anglers or other natural means of mortality).
Think about trout lakes for a minute. When they get overrun with chubs growth rates of trout decrease significantly. If you add more food for the trout, you just increase the carrying capacity of fish and increase the population, which drives average size down. So, instead, you poison the lake and eliminate all the fish (chubs + trout). Now the lake has 0 fish, and the lake has a boom in nutrients, zooplankton, aquatic insects, etc. Now you restock it with trout -- and guess what? Growth rates explode! Those trout, as we've seen in places like Yuba, Piute, Panguitch, after a rotenone treatment, grow big fast!
We see this all the time with brook trout on the Boulder. After a partial winterkill the remaining fish experience fast growth rates and get large fast! What we do NOT want with these fish is for them to get "old". If they are getting old it means their population numbers are staying high, which means more fish survive, which means growth rates slow, which means average size goes down -- and those trophy sized fish disappear. We do not want old fish. We want fish that are growing fast!
So, the real question that you guys need to figure out with the catfish isn't how old they are, or what their average inches per year over the life of the fish is. The question you need to find out is: what are their current growth rates? Find out the "K" factor.
Find out what can be done to increase the growth rate. Most likely the answer would be to remove more fish. Any fish. White bass. Carp. Suckers. Catfish. Any of them. Harvest more -- I'm pretty sure those fisheries are currently not overharvested. Take more fish out and increase growth rates. Increased growth rates = big fish.
Than, like wormandbobber said, the space occupied by that 15 year old fish that you just harvest will immediately be replaced by another fish that experienced high growth rates, which means another big fish.
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