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FINSIGHTS- TRANSLATING THE SCIENCE OF FISHERIES REPORTS #10

Finsights #10 Lip gripping devices and your catch. Tiger fish. Dave McCoy photo.

Finsights #10 Lip gripping devices and your catch. Tiger fish. Dave McCoy photo.

Sport Fishing Magazine recently published an article on A Guide to Lip Grippers. The very last paragraph of the article touches on how lip gripping devices can impact fish and the author states “Many of the lip-grip manufacturers interviewed independently stated that they believe their weight scales do not cause physical damage to fish or inhibit future feeding ability — when the fish is hung vertically”.  I decided to dig through the scientific literature to see if anyone had looked at this at this and found only three studies that focused on lip gripping devices, each on different species.

 
Bonefish The first study looked at if lip-gripping devices caused injury to bonefish.  They compared bonefish held vertically in the air with a lip gripper to those held horizontally in the water with a lip gripper, all compared against a ‘control group’ where bonefish were handled only with bare hands   Bonefish held with a lip-griping device either vertically or horizontally were prone to injury – 90% of fish had at least minor injuries (which included holes through the tissue of the lower jaw where the lip gripping device was placed) and 35% of fish had major injuries (including broken mandible and separated tongue).  Conversely, only one of the fish held by hand had a minor injury and none had major injuries.  All fish survived for 48 hours after being handled, but the authors did not monitor for long-term survival or feeding ability.  

Injuries sustained to bonefish using a mechanical lip-gripping device.  Link to report.

Injuries sustained to bonefish using a mechanical lip-gripping device. Link to report.


Barramundi In 2009, a different group of scientists looked at how lip grippers compared to nets for holding barramundi (an Australian sportfish).  They compared barramundi held in a net with those held vertically by a lip gripper, as well as those held horizontally with a lip gripper and one hand supporting the midsection of the fish.  They found that all fish held vertically and 81% of fish held horizontally had holes in their lower jaws.  However, no fish had severe injuries as was seen with bonefish.  Furthermore, all fish resumed feeding within 3-5 days and all holes healed within three weeks.  The scientists also took x-rays of some of the barramundi to see if holding them with lip grippers had any effect on their vertebral alignment.  They found that holding barramundi vertically, and to a lesser extent holding them horizontally with the lip gripper causes vertebral separation.  None of the vertebrae separations recovered after three weeks. Being water dwellers where the water supports much of their body weight, holding fish in the air has the possibility of causing damage or separation to vertebrae.


Florida Largemouth Bass The most recent study on lip grippers was conducted on Florida largemouth bass and examined the differences between holding largemouth bass vertically with a lip gripper, by hand on the lower jaw using a tilted grip, and using a two-handed hold.  They found no difference in feeding behavior, survivorship, or rates of injury between any of the three methods of holding bass.  They did, however, find that largemouth bass that were held with the lip-gripping device took longer to recovery than other fish.


Why are these studies important to anglers?
    •    These three studies constitute a start to the much-needed research on lip-gripping devices, and given the diversity of these devises and the species they are used on, clearly there is more work to be done.
    •    What these studies do show is that there is a wide variation in how lip-gripping devices affect the incidence of injury on different fish species.
    •    What I could not find are any studies that examine repeated use of lip grippers, long-term affects on fish, or compare injuries from lip grippers to those caused by nets.  
    •    If tackle manufactures want to make claims that their lip grippers and other fish handling products do not harm fish, they should consider independent testing.

Happy Fishing!
Sascha Clark Danylchuk

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FINSIGHTS- TRANSLATING THE SCIENCE OF FISHERIES REPORTS #6

Finsights #6 – “I saw the fish swim away so it must be fine” - Part 2

Golden dorado pondering the outcome of it's next meal.  Dave McCoy  photo.

Golden dorado pondering the outcome of it's next meal. Dave McCoy photo.

My last article aside, we assume that most of the fish that we catch and release actually live. But, does catching and releasing a fish have any impact on it?  Maybe.  Does an angler have any control over what these impacts are?  Sometimes.  

The slew of possible impacts of angling on fish are called sublethal effects. A lot of catch and release angling science has to do with minimizing or explaining the sublethal effects, so it’s important to understand what those can be and how different aspects of angling can have different sublethal effects.  

Fig. 1. from  the linked paper.  Conceptual diagram outlining the immediate and long-term effects of escape or release from commercial fishing gear and how it relates to each level of biological organization. Question marks (?) denote areas for which no primary literature exists, and present future avenues of research.

Fig. 1. from the linked paper. Conceptual diagram outlining the immediate and long-term effects of escape or release from commercial fishing gear and how it relates to each level of biological
organization. Question marks (?) denote areas for which no primary literature exists, and present future avenues of research.

For this post, I’m focusing on one figure from an article.  Don’t be put off by the fact that this article deals with commercial bycatch and not recreational angling – the issues for released fish are the same, and this paper is widely referenced in the recreational fisheries science literature (not to mention that several of the authors work on recreational fisheries too).  

So, here it is, a rundown of the potential sublethal effects of angling:

Immediate Sublethal Effects
This deals with the acute effects of angling on fish and are most obvious to fishers.  
    •    Physical Injury.  Hooking wounds are what usually come to mind, but don’t leave out blood loss, foul hooking injuries, and injury that occurs during handling and hook removal.
    •    Physiological responses.  Physiology deals with the functions of an organism or it’s systems/parts.  A physiological response occurs when an event (such as angling) causes an animal to function beyond its “normal” activity levels.   This is most often measured via a blood sample in fish (see Finsights #4 for more details).
    •    Reflex impairment.  This is most easily thought of in human terms – when you’ve had one too many and can’t walk a straight line, you have reflex impairment.  For fish, this could include the loss of equilibrium (see Finsights #5), or lack of coordinated movement between the mouth and gills.  

Testing the reflex impairment of golden dorado on the Rio Juramento, Argentina. Tyler Gagne photo.

Testing the reflex impairment of golden dorado on the Rio Juramento, Argentina. Tyler Gagne photo.

Delayed Sublethal Effects
If the immediate sublethal effects are severe or last long enough a fish could end up with these.
    •    Behavioral impairment.  This could include anything from spawning to swimming behavior.  
    •    Altered foraging efficiency = altered ability to find, compete for, and capture food.
    •    Growth and wound healing.  Animals that must spend energy on wound healing can have decreased growth.
    •    Altered energy allocation has to do with how a fish apportions energy (e.g. energy derived from food) to the life traits of growth, reproduction, and survival.
    •    Immune function and disease development & offspring quality, performance, and survival & reproductive success.  All of these have to do with the point above; when more energy is needed for one of the three life traits, one or both of the others get less energy.  

All of the sublethal effects above only refer to what happens to an individual fish.  It’s possible that these individual level effects can also impact the entire population.  For example, if enough fish experience decreased reproductive success, this could lead to less fish in subsequent generations.  

It’s this step - moving beyond what happens to one fish to the population - that is particularly challenging for the field of catch and release science.  In part, this is because it’s a really hard thing to do - to show, definitively, that sublethal effects at the individual level can have cascading effects on an entire population or community.  In future posts, I will dig into some of the studies that have begun to chart this course.  

As anglers, the more we can do to decrease the sublethal impact of angling on individual fish, the less likely there are to be higher-level effects.

Happy Fishing!
Sascha Clark Danylchuk

 

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