We've all heard about how we should be more cautious concerning the frequency with which we hold bass using the "lip grip" due to torquing the jaw when handling and taking photos, especially with larger fish. I've spent much time trying to track down specific studies in the literature that actually confirm or refute the claims we read, but have pretty much come up empty. A lot of stuff we do while handling fish, we tend to think is the right or best way of doing so, but often studies don't support such claims. Hard to tell where or how these things get their beginnings, but needless to say, they get repeated ad infinitum in articles and forums year after year. Regardless, the following is the best article I've found on the subject that is rooted in solid scientific basis. It is by Justin Grubich, a fish physiology and biomechanics major who has studied the feeding mechanics and jaw pressures of a variety of fish...the same person responsible for that slow motion smallmouth feeding video from yesterday. Not stating right or wrong, as this piece is likely salt water biased, and as we all know, not all fish are created equal. Just makes for one of the better (educated) reads on the subject.
Why lifting fish by their lower jaw can significantly reduce post-release survival
Originally published in Salt Water Sportsman (Article>Gear-and-Techniques>Lip-Gripping-May-Harm-Fish)
March 1, 2004
By Justin Grubich, Ph.D
We've all done it: the classic trophy pose. You know, the one where you lift the fish by its lower jaw, either by placing your thumb in its mouth or with one of those popular lip-gripping devices. Before attending graduate school, I held many of my own catches in this manner. However, subsequent research into fish physiology and biomechanics - in which I earned my degree - has shown me that lifting fish by their lower jaw can cause severe and potentially life-threatening injuries. That's why I no longer do it.
It's understandable why lip-gripping is so universally accepted. For one thing, it's a convenient way of immobilizing the fish during the hook-removal process, plus it keeps slime and scales off your clothes and boat. Furthermore, the practice is perpetuated by the fishing media - lip-gripping appears everywhere, in magazines, newspapers, books and on TV.
To find out just how prevalent the technique is, I conducted an informal survey of recent fishing magazines (August to October 2003). I categorized the handling methods depicted in the photos as either "hoisting" (lifting the fish by its lower jaw or the corner of its gill plate) or "cradling" (supporting the fish with two hands in a roughly horizontal plane). In this simple survey, salt water anglers hoisted their catch by the lower jaw roughly 40 percent of the time. Some species, such as red drum, snook, tarpon, striped bass and seatrout, were jaw-hoisted more often, probably because the lack of sharp teeth on their lower jaw makes them easier to handle in this fashion. For comparison, salt water anglers fall somewhere between trout fly fishermen, who cradled nearly 100 percent of their fish in the photos I observed, and fresh water bass anglers, who appear to always hoist their fish by the lower jaw.
Handling techniques may seem a small issue until you consider all the physiological and anatomical stress experienced by the fish during the fighting and landing process. Muscle exhaustion, lactic acid buildup and hook punctures all reduce a fish's chances of post-release survival, so it's important to limit any additional forms of stress or injury. And one simple way to do this is to refrain from lifting them by their lower jaw.
Jaws of Life
The jaws of fish perform multiple functions during feeding. They are used to capture, manipulate, dispatch and, in some species, locate prey. For example, a red drum's jaw can detect the movements of buried prey through pressure-sensing extensions of the lateral line found in pits along the lower jaw bones and gill plates.
Although the mechanics of feeding appear to be as simple as the opening and closing of the mouth, the underlying sequence of muscle contractions and bone movements is actually very complex. Many of the fish we pursue, including striped bass, tarpon and snook, capture prey by generating a powerful suction that pulls the prey into the mouth. Suction feeding is accomplished by a dynamic sequence of head and jaw movements that creates a pulse of water that flows into the mouth and out the gills. First, the lower jaw rapidly opens. Next, the head begins to lift, the upper jaw protrudes, and the floor of the mouth depresses. Finally, when the jaws are open to their fullest extent, the cheeks rapidly expand and the gill plates flare to the sides. This expansive phase of the strike generally takes less than 0.03 seconds - faster than can be perceived by the human eye. After expansion, the strike concludes with the jaws quickly clamping shut, trapping or grasping the prey and preventing its escape. Fish will also often repeatedly bite and manipulate large or awkwardly shaped prey items in their jaws prior to swallowing.
The lower jaw plays a critical role in feeding mechanics in that its downward motion controls protrusion or extension of the upper jaw through ligaments. Jaw protrusion aides in prey capture by first shortening the distance to the prey and then creating a rounded oral tube for sucking it into the mouth. In most game fishes, the lower jaw rotates approximately 30 to 40 degrees during feeding. This rotation occurs at a pair of saddle joints at the bottom of each cheek. These joints are the only places where the lower jaw is attached to the rest of the fish's skull.
Mechanically speaking, the lower jaw mechanism emulates what engineers call a third-class lever system. Third-class levers are very common in the limbs and jaws of most animals. For example, your biceps, elbow joint and forearm form a third-class lever. This type of lever is good at transforming muscle force into speed at the jaw tip, but is not necessarily strong. The farther away weight is placed on the jaw from the center of rotation, the weaker the bite and the less able the jaw is to resist damaging forces. The length of a fish's lower jaw is directly proportional to the speed at which it is able to open and close its mouth and is inversely related to the strength of its bite. For example, species with relatively long lower jaws, such as snook and tarpon, have fast jaw movements but generally weak biting ability.
Too Much Weight
Regardless of the species, when you grab a fish by its lower jaw and lift it, you're placing nearly all of its body weight on that crucial lower jaw joint. In red drum, for example, the weight of the opening and closing jaw muscles and lower jaw bones make up less than two percent of the fish's total body weight.
Keep in mind also that the fish's jaw muscles, bones and joints have developed in the relatively weightless underwater environment, where they never experience such heavy loads. As fish get larger, jaw stability and strength do not increase proportionally, so bigger fish have relatively weaker jaws than smaller fish of the same species. Therefore, lifting big fish by the lower jaw can be even more harmful, because their jaw muscles are less able to resist the stretching forces of their heavier body weight.
Hyper-extension of the jaw can also damage the jaw's closing muscles, located in the cheeks. For example, if you tuck your elbow against your body when lifting a fish, stretching forces caused by the fish's body weight can tear the muscle fibers and tendons attached to the lower jaw bone and cause dislocation of the saddle joints. These kinds of injuries will prevent the fish from being able to quickly close its jaws during future feeding, which may allow its prey to escape.
The use of "lip grippers" and weighing devices, which do not necessarily hyper-extend the jaw, can still dislocate this critical joint in bigger fish and can potentially tear the jaw-opening muscles of the throat that attach to the inside of the lower jaw tip. Injury to these muscles and attachment sites will reduce the fish's ability to generate suction for feeding. Lip-gripping devices should be used primarily to control the fish's head so that you can place your other hand underneath the body to cradle it. Bottom line: only hold the fish vertically when measuring its weight is absolutely necessary.
Internal Damage
Hoisting a fish that you intend to release may not only injure its jaws and limit its ability to feed, it may also damage its internal organs. Remember, fish are designed to function in a buoyant environment, without the gravitational forces we experience on land. When you hold a really large fish vertically, the weight of its internal organs can stretch or tear the mesenteries that hold them in place, causing the internal organs to slump toward the tail. Such internal damage could have adverse effects on the fish's digestive functions.
If you are serious about ensuring the survival of a released fish, the best thing you can do is never remove it from the water. But what if you want to take a picture of the fish or need to bring it onboard to remove the hook? Fortunately, there are ways to handle a fish that will not cause as much harm as holding it by the lower jaw - and make for a better photo, as well!
Let's face it: holding a fish by its lower jaw doesn't really present it in the best light. After all, fish generally don't swim in a vertical position, so it's somewhat unnatural to see them held that way. The next time you pose with a fish, try cradling it in your arms, with one hand supporting its body. I think you'll be more pleased with the resulting photo, and you can also take comfort in the fact that you are giving the fish a better chance of survival.
Florida native and avid angler Justin Grubich received his Ph.D. in fish physiology and biomechanics from Florida State University in 2001. He would to thank Jason Schratwieser and Ron Taylor of the Florida Fish & Wildlife Commission for their help with this article.
Ancient Fishing Wisdom - I
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