As avid bass anglers, we all strive to be good conservationists while minimizing our impact on fisheries. At the same time, however, we also want to show off our catches to our friends and family. This leads us to a prominent question that has been at the center of many spirited debates: What, if any, physical impact does holding a bass have on its jaw?
There isn't much scientific research on this topic, which currently leaves anglers and biologists very little basis for making recommendations. We want to begin to change that.
To gain a better understanding of this issue and learn exactly what's happening to the jaw when held at various angles, we teamed up with Steven Bardin, a leading fisheries biologist and owner of Texas Pro Lake Management. Bardin, along with two veterinarians, Dr. Casey Locklear and Dr. Steven Mapel, designed and conducted an experiment to help shed some light on things.
The results and correlating imagery were nothing short of fascinating.
Bardin and his team of veterinarians had very specific criteria for
this experiment. In order to judge the effects on overweight,
trophy-sized fish without actually harming true trophies, they paid
especially close attention to the relative weights of each test subject.
"We
wanted to mimic the body shape and anatomy of trophy-sized fish,"
Bardin said. "In order to do this, we captured fish using electrofishing
on a private lake that I personally manage. We then selected the
individuals that weighed between 2 and 6 pounds with a relative weight
of 100 to 125 percent.
"Relative weight is a body condition score fisheries biologists use to compare the actual weight of a fish to what it should
weigh based on its length. These higher relative weight fish are
overweight for their length, giving them the appearance of what we would
expect a trophy fish to look like."
Once the test subjects were
captured and their relative weight was calculated, Dr. Locklear and Dr.
Mapel of Hat Creek Veterinary Services took detailed radiographs of each
bass being held in four common positions.
Vertically, with minimal pressure on the jaw.
Vertically, from a hanging fish scale.
Vertically, with the weight of the fish forcibly applying downward pressure on the lower jaw.
Each fish was radiographed in the order described above to ensure any
damage on the jaw would be cumulative based on the potential increase
in stress at each position. The veterinarians then examined the
radiographs of each position, looking for any noticeable breaks in jaw
bones, with an emphasis on the dentary bones that make up the bottom
jaw.
What did we see?
Based on the
radiographic images, the veterinarians did not observe any broken bones
in the lower jaw after being held in any position. After further
discussion with the team of veterinarians, they explained that broken
bones are not as probable as soft tissue injuries in this situation.
Each fish was radiographed in the order described above to ensure any
damage on the jaw would be cumulative based on the potential increase
in stress at each position. The veterinarians then examined the
radiographs of each position, looking for any noticeable breaks in jaw
bones, with an emphasis on the dentary bones that make up the bottom
jaw.
"The excess weight and pressure being applied to the jaw is not
resulting in one bone location taking all the stress," Dr. Locklear
said. "Instead, the entirety of the lower jaw bones, joints and other
soft tissue areas tend to absorb the stress. The weakest parts of the
jaw are actually the soft tissue areas, not the bones."
The absence of broken bones is certainly a good thing, but were there any other soft tissue injuries that occurred?
"There
is very little reference material or studies regarding soft tissue
injuries in a bass jaw, so we carefully attempted to isolate specific
joints and bone junctions (symphysis) that were potential locations for
injury," Bardin said. "These areas of interest are places where
excessive pressure would likely be applied or over-flexion or
over-extension of the joint could occur. Potential areas of concern in
the lower jaw were found to be the mandibular symphysis, located
centrally where the left and right dentary bones meet, and the joints
where the angular bones and the quadrate meet.
"The mandibular symphysis is not a joint, but a location where two
bones meet with cartilage between them. They are not fused like a
human's bottom jaw, so there is slight mobility in this area. I found
that each dentary bone could move slightly, but mobility in this area
became much greater as we increased the weight of our test subjects.
"When
you hold a bass by the lower jaw, you usually place your thumb onto, or
to either side of this symphysis, and your fingers fit directly behind
it. So in some of the holding positions, you put excess pressure on this
area. Professional angler Gary Klein, who I asked to observe the
experiment, mentioned he has actually caught fish in the past that had a
visible separation of this symphysis.
"In regards to joints, we
identified the joint between the angular and quadrate bones as a major
concern. This is not the only joint where soft tissue injuries could
occur, but it is one the primary joint that controls the opening and
closing of the mouth. Essentially, this joint is where the lower jaw
meets the rest of the skull. It appears this would be the joint that
actually has the greatest likelihood of over-extension."
"Due to a lack of industry research, we honestly don't know how an
injury like this affects a fish, nor do we fully understand the recovery
period for these injuries," Bardin said. "For humans, spraining an
ankle, dislocating a shoulder or any other soft tissue injury can take a
much longer time to repair and recover from than a clean break of a
bone. In fact, these injuries can increase the potential for reinjury
and, in many cases, cause further instability.
"Fish with these soft tissue injuries will likely swim away and
appear completely normal. The questions become: How does a soft tissue
injury in the jaw affect the ability of the fish to properly capture
forage? Is the injury more likely to reoccur in the future? Does the
fish feel the effects of the injury long-term or possibly forever?"
It's
also important to understand the impact that the fish's size had on a
potential injury. According to Bardin, there was definitely a
correlation between the two.
"It did appear that there was a
direct correlation between the size of the fish and the probability of a
soft tissue injury," Bardin said. "The jaw of the largest fish we
radiographed actually made an audible 'pop' when it was placed into the
exaggerated vertical position. Following the study, this fish also had
visible laxity in the mandibular symphysis that I would consider to be
abnormal. This damage was not observed in smaller fish nor did they have
the same pliability in the jaw that the larger fish did."
The use of a fish grip or hanging scale
(Photo: Steven Bardin)
"I
personally use a hanging fish scale with a clip when weighing fish on
my electrofishing boat," Bardin said. "I'd never want to do something
that has a negative effect on my clients' fish. Thankfully, we found
that in most positions, a fish grip or hanging scale with a clip was
beneficial because it was difficult to put additional pressure on the
fish's joints while holding them vertically. The clips actually act as a
pivot point, so as the fish move on the scale, it takes much of the
pressure and force off of the jaw."
Important takeaways from this study
Larger fish do require an increased emphasis on proper fish handling, by supporting their weight with a second hand.
Applying
too much pressure to soft tissue areas can cause damage. Many state
agencies claim anything greater than any angle that deviates 10 percent
or more from vertical or horizontal has the potential to damage the jaw.
Holding fish with a fish grip or by a hanging scale is beneficial.
The
recommendation that it is acceptable to hold fish horizontally with a
second hand supporting its weight or completely vertical is still valid
and supported by our research.
Holding fish vertically with the weight of the fish being placed on the jaw in an exaggerated fashion is not acceptable.
Injured fish will likely swim away and appear completely normal.
Long-term affects of soft tissue injuries are currently unknown.
What's next?
(Photo: Steven Bardin)
As
an industry, we certainly need to expand this research by looking at
both the short and long-term effects of possible soft tissue injuries to
the jaw. How does this affect feeding and the ability of these fish to
compete? Do the fish have a lifelong injury or higher potential for
reinjury?
In the meantime, it's important to do everything we can
to care for these trophy bass for the short time they're in our
possession. Although the fish may swim away normally, it's always best
to err on the side of caution and handle these fish the best way we know
how.
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