I am curious about a few things:
1) In southwest Idaho (Airport pond in Emmett, CJ Strike, Lake Lowell, etc) how long do small and large mouth bass take to grow? I have heard a 5lb bass is over 15 years old?
2) Why is it that everyone says to never keep bass? Does this negatively impact growth and population? Is this only in small ponds vs large reservoirs? What is the science behind this? Should people not be keeping bass to eat?
Both species of bass in most of the waters you list grow slowly. A 5 lb bass could certainly be 15 years old; however, no matter where you are talking about bass from the same year class show a range of growth rates with some growing slow, others near average, and others growing more quickly. This may be influenced by water temps, sex, feeding habits, and age at maturity. We recently estimated the ages of bass at Lake Lowell. Many bass in the 14-16 range ranged from 6-12 yrs of age. Bass at other waters grow at a similar rate, but probably not quite as slow as Lake Lowell.
There are several reason why people encourage others not to keep bass. One is people think it is a highly-prized sportfish and they have some interest in seeing high release rates, so they have the opportunity to catch trophy individuals. A second reason is that bass have consumption advisories throughout Idaho due to mercurcy bioaccumulation. All anglers should ensure that they are following these advisories which encourage only a certain numbers of meals per time period and to selectively harvest smaller fish. Lastly, you discuss science/biology, this is a very water specific question. We estimate harvest rates through tagging studies. We see a range of harvest rates from these studies. Most of the larger water bodies (Brownlee and CJ) have moderate harvest rates (20-35%) which have shown to be sustainable and capable of providing some trophy class fish too. Smaller ponds and reservoirs may be over-harvested if they receive intense pressure, but not all receive intense pressure. If you have additional questions, please call the Southwest Regional Office in Nampa.