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
Permalink | Comments (6) | TrackBack (0)
Reblog (0) | Tweet This!