I came across this interesting research story in Yahoo news a while back: Scientists say fishing regs may create timid fish. The researchers in this study propose that it is the aggressive and larger fish that are most prone to capture under normal regulations, and hence their removal leaves a population of slower growing and more timid fish left in the population. You’ve probably read articles on bass fishing that suggest the largest bass get that way by being the best and most efficient predators, actually more aggressive and having to feed either more frequently or on larger prey items in order to maintain that level of growth and body condition.
This also ties in nicely then with why larger bass always seem to be in the minority of the population in a lake, and also falls in line with the theory that John Hope proposed in his giant bass telemetry tracking, that being that giant bass behavior and life-style patterns were such that they largely avoided traditional zones of pressure and angling effort.
There was a paper presented on a study here in Indiana that documented just such happenings on largemouth bass. I got a chance to speak with the authors rather extensively about their study. They sampled a 5-acre kettle lake that had been around for nearly 30 years and had only the slightest pressure (private and largely unfished) and a strictly enforced catch and release policy for the few who have been able to get access. Using ‘hook and line’ sampling on 8 different dates from Sept.-Nov. 2007, they caught, weighed and tagged 58 largemouth bass. Each fish also had a fin clip sample taken to document age. There was only a single recapture out of the 58 fish sampled, and the total LMB population was estimated to be 1,450 individuals with a metric that suggested most of the fish in the population were well over 12″.
Further results included a mean length of 16.7″ and a mean weight of 2.12 pounds. Mean length at age-4 was 16.0″ compared to a state average in public waters of 11.4″. The largest bass captured was 23.75″. The theory proposed to explain the differences was that in unexploited populations, the most aggressive and subsequently fastest growing fish were the predominant drivers of the population age and size structure, and fishing pressure that allowed for most any level of harvest would ultimately crop off these particular fish first from the population, potentially leaving smaller (i.e. slower growing) fish in their place. Any wonder why you catch lots of 13.75″ bass when tourney fishing on a lake with a 14″ size limit?