I've come across two truly fascinating studies concerning largemouth bass and hypoxia. One was published a year ago, the other is set for publication very soon. In both cases they studied varying amounts of air exposure after exercise/angling that a bass could be subjected to. One was done in the lab, one in the field. Both have reached the same basic conclusion. Check these out:
Behavioral and physiological responses of the congeneric largemouth (Micropterus salmoides) and smallmouth bass (M. dolomieu) to various exercise and air exposure durations
This is the lab test comparing largemouth to smallmouth. Bass were physically exercised to simulate angling and then held by the jaw ("thumbed" just like most every angler does) for a randomly chosen amount of time up to 10 minutes out of the water and exposed to the air. Afterward, fish were placed back into a holding tank and observed and tested for some chemical parameter monitoring, then ultimately placed back into a raceway for 24 hours to observe for delayed mortality. Water temps ranged between 18-23 deg. C. in this test. Largemouth recovered faster than smallmouth as expected, but there were no documented mortality cases after 24 hours.
Physiology, Behavior, and Survival of Angled and Air-Exposed Largemouth Bass
In this test of largemouth bass only, bass were angled from the lake and then held out of the water for a varying amount of time that ranged from 0 up to 15 minutes. Tests were conducted during two specific environmental time frames, once at 15 deg. C. water temps and again at 21 deg. C. Bass were also tested for various bodily (chemical) parameters and were then placed in a holding tank for 30 minutes of recovery/observation. During this time they were fitted with an external transmitter and then released back into the lake and tracked for 5 days. Again, no delayed mortality occurred for any of the fish including those held out of the water for the maximum 15 minutes. Fish held out of the water longer took longer to recover, as well as longer to leave their release area in the lake (at higher temps vs. short duration cooler temps, but not significant).
We've always figured "bass aren't trout" and could be subjected to greater stressors (i.e., air exposure) and still come out OK. That bass could be held out of water for 10-15 minutes and returned relatively unharmed was a bit of a surprise to me. That is a rather lengthy bit of time even for the most unpracticed of bass anglers. I am actually quite shocked at the result, but certainly love the practicality of the study. That said, keep in mind that all testing occurred at water temps at or under 75 degrees F., the temp. threshold that has long been thought to be the dividing line between safe and unsafe when it comes to fish care handling practices. Both studies warned of possible high mortality if repeated in these warmer water temps. The general rule of thumb that you'll hear bass anglers espouse is to hold bass out of the water no longer than you could hold your own breathe. While this still remains good practical advice to follow, we now have some concrete evidence to actually make specific statements concerning this subject.
Another Fun Day on the Water
Another good day on the water. Met the "Big Dummy" himself around 10:30 this morning, loaded everything up and hit the water for a few hours. Had a light NNE breeze, temps in the high 80's, plenty of sunshine and a little bit of boat traffic. Water temps were running between 82 and 83 degrees. Was perfect conditions to run around in the little jon boat today. Did a bit of graphing and spent most of the time hopping from spot to spot. Kept the tackle on the light side and just threw worms, jigs and crankbaits. Managed to put a good triple limit of keepers in the boat averaging about what you see in the picture size-wise. We had a few bigger and a few smaller, along with 3 sets of doubles today. The bite wasn't fast and furious, but we managed to catch fish off most every spot we pulled up on, many times several fish.
Got a few graph pictures to show everyone what we were seeing and fishing most of the day. In this first pic you can see a nice aggregate of bass sitting off a hard bottom transition as we slide down a sloping break. Lots of bass roaming in small groups from what we could see on the depthfinder. That was also how we tended to catch them. It seemed if you could get one triggered, by repeating the cast we would often end up catching 3 or 4 fairly quickly. This was most likely why we ended up with several doubles today.
In this next pic, you'll see a nice group of shad starting to show on the depthfinder as we come off a little break. You can even see what appears to be a bass at the leading edge of the school. You'll notice the shad schools are sitting at about the same depth as the bass in both pics. There are a lot of shad moving around and a lot of bass sitting on these areas waiting for shad to move in. We saw a lot of isolated dead shad floating and they were all about 2" long.
On a little sadder note, there was a club tourney out on the water today. Water is fairly warm and when you're out there for 8 hours or more, it can definitely be stressful on the bass. Livewell maintenance is at a premium in hot water conditions. Turns out it took just over 11 pounds to win today, so there weren't any jam packed livewells out on the water. We had much more than that in the 4 hours we fished. But when I came in today about 45 minutes after they weighed, I saw several dead bass just laying on the bank next to the ramp. These were freshly killed fish as you can tell in the picture, which I'm certain were from the tourney. Dead fish are going to happen in tourneys, sometimes there are just no good ways around it. But if you're going to run around at 65 mph on a little 300 acre lake acting like Pro-feesh-ionals, at least deal with your dead bass in a professional way also. Let someone take them home and fillet them, plant them in your rose garden or dispose of them in a trash receptacle. Leaving them dead on the bank is not the impression you want to leave for all the recreational people using the lake that day.
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