Decreased relative predation risk during the experiment reflected the reduction in littoral predators and identified seasonal differences in nearshore predation risk. The smallmouth bass population was resilient to removal, producing strong year‐classes throughout the experiment. Mechanical removal was successful at decreasing smallmouth bass abundance and increasing native fish abundance, but removal must be conducted on a yearly basis to maintain low smallmouth bass population abundance.
This is in-line with the contexts shared in the "Must Read" thread. It doesn't take a high standing population of SMB to produce substantial year classes of offspring. Reducing adults can help to reduce the predation mortality of SMB that are below recruitment lengths. So it can be difficult to reduce the production/survival of SMB offspring by removing SMB adults. The same applies to any fish. This includes BG. One cannot cause the production of YOY to suffer by removing BG that are too large to eat.
Because non-catchability in recreational angling has been demonstrated to be an inherited trait over time (a couple of years) we can quickly have a pond full of non-catchable fish.
Stop and consider this:
If non-catchability is an inheritable trait, then why did selected fish that did not prove vulnerable to angling (were not caught) have offspring that were in fact vulnerable to angling?
Doesn't make sense, does it? That is, that "not being caught" is a trait that can be inherited. If that were true, the offspring of fish that were apparently invulnerable would not have been vulnerable at all. Vulnerability (or catchability ... let them mean the same) is heritable. So the fish that were not caught of the parent generation were not non-catchable ... they were vulnerable (or catchable) to a lesser degree. This is evidenced by the fact that their offspring were indeed vulnerable (or catchable) to a lesser degree than the parent generation.
FWIW. I believe that LMB definitely can learn hook/lure avoidance and that some are more vulnerable than others. These are important to catch rates in any BOW. The first, I believe, is the most powerful influence. Why? I regularly fish ponds that are subjected to insane levels of fishing effort. Every year, I observe a peak of catch-rates in spring that rapidly decline as the fishing hours rapidly increase for the year (The vast majority of which are not mine but others). From this experience, I discern that the winter rest does them good and helps to make them more vulnerable than they were after 6 months of persistent fishing pressure. Another influence is population density. Philipp, etal normalize catch-rates by this variable ... and I do believe this is very important. In my favorite pond, I have done monthly shore surveys for several years and the number of LMB sighted has been declining where the curve that best fits the data indicates the population is ~50% of what it used to be. So part of the catch rate that I experience there is this influence alone.
With regard to the heritable trait of vulnerability ... little is known about what is actually inherited. There have been a number of studies that have sought to discover what other traits may be selected when vulnerability is selected. The jury is still out, although some cooccurring traits have been suggested. It could be something as simple/complex as the inability to determine whether an artificial item is not food. Or it could be behavioral, for example, LMB that might pursue and consume mostly in darkness may less vulnerable during the day when folks are fishing. The point is, there is alot to be learned about vulnerability that we do not yet know.
I have personally given a lot of thought to vulnerability and how I will manage it. To lessen the deterioration of the trait, fish that have proven vulnerable to artificial lures should be selected so that the trait can be inherited. A pond only needs a limited number of LMB, if the trait is important to one, he should try to limit his population to fish he has caught on artificial lures. To lessen the impact of those less vulnerable, he should remove them by alternative methods of removal. Fishing with live bait or electro-fishing, for example. Possession is 9/10 of the law. If LMB of higher vulnerability are selected to be those adults that reproduce, then their vulnerability trait will pass to future generations. To effectively manage in this way, one must be able to identify LMB that have been caught on artificials by some system of marking. If an LMB is caught without the identification by live bait or electrofishing, then there is less risk that the LMB removed was highly vulnerable to angling. It is more likely, given sufficient cumulative fishing effort with artificials, that the unmarked LMB be of lower vulnerability.
Finally, with regard to the chart depicting the decline of catch-rates. Down there in the far right, especially later in the warm season, that is my experience in the pond described above when fishing with artificial lures. Fishing pressure has a huge effect on catch-rates. I can catch LMB at 2 or more per hour on live BG (even to include the BG bait fishing if they are abundant). Live bait is more effective on difficult to catch LMB. The chart shows catch-rate vs cumulative catch. A better representation would be vulnerability vs cumulative fishing effort (cumulative fishing hours) per unit area). This would normalize the data in the language of Philipp, et al. It would depend on the data which may not be presented in sufficient detail to infer catchability and cumulative fishing effort. Anyways, I would like to review that paper to see if the data is sufficient for these inferences ... if someone could point me to a link where a downloadable version is available. This could serve as a model I could share with members that would model expected catch rates under various population density and cumulative fishing hours. We could also collect our own data, if people were interested in contributing data.
