Dr. Keith Jones On BassFan

Back in April I posted about a section on BassFan that was highlighting some of the work of Dr. Keith Jones from Berkley. Dr. Jones has his own book out on largemouth bass entitled "Knowing Bass: The Scientific Approach to Catching More Fish" which can be found at the book link on the left sidebar of this site. The section on BassFan is entitled "Bass Buzz" and seems to be a now somewhat regular column on the site. The most recent article posted today on the site is "Can Bass Learn?".

The article references an Illinois Study, the abstract of which can be found here. One of the interesting findings from that study was the following: "Some fish were caught as many as 16 times in a single season and one individual was caught 20 times during the 4-year experimental period. On the average, largemouth bass were caught approximately twice during any given fishing season. Between 1977 and 1980, the 1,774 fish that were caught in 1980 had been captured a total of 6,969 times or approximately four times each."

They ultimately determined that largemouth capture by anglers is largely a product of individuality and can vary from season to season. They also suggested that this trait could be heritable. Another study with very similar results was written by Willis and Cody. You can find the .pdf version here and an html version here. This study confirms a couple theories, the first being that catch rates of largemouth bass in general are directly correlated to population size. The more fish in a body of water, the more fish get caught. This has been further documented in other species of fish, most notable (that come to mind) being walleye. The other interesting finding they mention (from an INHS study), is that as pressure increases on a given body of water, catch rates ultimately decrease, also directly correlated. They surmized a learned behavior which could actually make bass in a particular body of water practically uncatchable.

Another similar study which documents the genetic differences in catchability between different subspecies of largemouth bass comes from Kleinsasser et al.. They confirmed that northern bass were generally much more "catchable" than their Florida counterparts. They also documented what is known as "hybrid vigor", that being the first generation cross between the two subspecies showed best growth and weight characteristics when compared to either parental lines. This obviously has some limitations though based around environmental conditions, as Florida strain bass when stocked up north tend to do no better than their northern counterparts.

Finally, an interesting study on rainbow trout from Askey et al. subject to heavy catch-and-release angling pressure. Catch rates dropped off significantly within 10 days of angling pressure. Among their conclusions:

• Learned hook avoidance was a key component needed to explain the large data set of individual capture histories.
• It was only possible to fit the sharp initial decline in catch rates if intrinsic differences in fish were also taken into account. It seems plausible that some proportion of fish populations should be less vulnerable to angling because of factors such as highly selective diets.
• Catch rates may continue to decline with continued pressure; however, the decline is much slower after the original “fishdown” period.
• Lastly, a small part of the decline in catch rates was fishery independent; catch rates were found to decline in the lightly fished lakes. Thus, other geographical regions that have different climatic patterns and fish species may experience different seasonal trends.

Comments

[Paul Roberts]

"They surmized a learned behavior which could actually make bass in a particular body of water practically uncatchable."

Why do they think this?

[Big Indiana Bass]

Different studies have shown bass to display varying degrees of conditioning or learned behavior. In the example cited, bass in the moderately and heavily fished ponds became uncatchable toward the end of the experiment. The authors attributed this to a conditioned response on the bass' part to the baits being presented. A similar study done by Hackney and Linkous (1978) demonstrated this same learned behavior by bass to live bait presentations.

In the real world, you would have several factors present. First, individuals that are highly susceptible to being caught would most likely get removed from the existing population. Second, studies show that there is almost always a certain percentage (15% in the study cited in the post) of bass that are never caught for a given population. Lastly, you have the middle group of occassional biters, some of which would be removed and some of which would "learn" and possibly not be hooked again in the future. Ultimately with enough angling pressure, this would lead to an incredibly tight-lipped population of bass.

The counters to this however also have to be taken into consideration. One, unlike studies, there is usually a never ending array of different baits or lures being presented to fish over time, thereby making the likelihood of fish being completely conditioned unlikely. Additionally, in nearly all cases there are always 'young ones' being recruited into the catchable population on a yearly basis. These previously uncaught (unconditioned?) fish then become a stable supply of catchable fish for a given year. Even this isn't a guarantee though as at least one study has demonstrated that bass populations, when broken apart into two distinct groups (highly catchable and highly uncatchable), are then bred separately, the offspring of each respective group tends to take on the biting characteristics of their parents. This then suggests not only a learned response at work, but also a genetic selectivity, similar to the differences found between the Florida and northern subspecies. Lastly, unlike many controlled studies, the unpredictable environmental variable which might override (if only temporarily) some learned caution.

[Richard Ziert]

There's something that lends to this post but can be overlooked.

When hatchlings are new to the world and guarded by Pappa Bass, is this solely for their protection, or is it also for learning what those little guys have to do in order to get along in their world? Imprinting behavoir/survival? I think so. Are fish the only cold blooded species that tends their young after birth? I believe this activity is something that sets them apart. It happens with just about every other species - save lizards - even then, they guard their nests - so why wouldn't it happen here?