Time for an update! For those of you just tuning in, I'm trying to balance this old 2.2 acre, bass-heavy farm pond by use of selective harvest. Last fall, I did a creel survey and harvest with the goal of removing as many bass as possible. I pulled out 115 LMB for a total of 40# removed. I surveyed the BG last year and their WRs were all 80% and relatively large (and all were returned to the pond), again consistent with the classic bass-heavy, under-harvested pond.
After a few days of fishing this spring, I've pulled out an additional 91 LMB worth 29# for a total of 206 LMB and 69# over the last six months. I did not survey the BG yet this year.
I recorded the weight and length of nearly all the fish during both sessions and here are some charts to help display the data:
This is a summary graph that shows all the fish in both the Fall '12 and the Spring '13 surveys. The '12 fish are in blue, and the '13 fish are in green. The x-axis shows the length of the fish, and the y-axis shows its relative weight. There are a few things I noticed about the distribution of the data in this 'raw' form.
The first thing I noticed was the bent rainbow shape to the distribution. The shortest fish have the worst RWs and the fish around 12" have the best RWs. As the fish get larger than 12" the RW falls again. The best explanation that I have for this is that the smallest fish are the most crowded -- the five-inchers won't take a lure very often, but those that do must have lots and lots of competition in their class. My guess is that the RWs improve for the larger fish because there are fewer of them in that size class, and then the RW falls again for the very long fish because of inadequate forage.
The next thing I noticed is that most of the green (2013) dots are higher than the corresponding blue (2012) dots at the same fish length. This suggests that the fish are in slightly better condition this year. It's possible this is a result of the harvest the year prior, but I'm guessing it reflects the fact that the fish I'm catching now are pre-spawn.
The last thing that jumps out at me is that most of the fish are between 8" and 9", and most of the RWs of those fish are in the 40% range. I think this is the size where most of the fish stunt and stop growing.
The following charts attempt to illustrate these trends in a way that's easier to comprehend graphically.
Here is the original Fall 2012 creel survey depicted as a combined histogram showing the number of fish caught in each length class as well as the average RW of the fish in each length class. Note how the average RW of the fish in each class improves as the fish get larger.
Here is this year's creel survey. The same RW trend is present. Also note how there are relatively fewer of the large fish, but those that are present (>12") approach 100% RW. The 8" fish class dominates the data set.
This chart shows the percent change in RW from 2012 to 2013. The RW of fish in every class except the smallest one increased. Again, I think this is likely to be a result of this year's fish being pre-spawn vs. last year's post-spawn fish.
Any thoughts or suggestions? Even though some of the 12" fish are posting ~100% RWs, my impulse is still to keep pulling them out. I hope I will see some continued improvement in WRs when I survey again in the fall.
Here's a pic that shows just how many LMB my cousin and I pulled out in about three hours this week (30+!). There's also one BG in there that didn't survive the catch & release we did with about 29 of his friends over the same time period.
Survey data album
