An evaluation of the injury and short-term survival of bonefish (Albula spp.) as influenced by a mechanical lip-gripping device used by recreational anglers
Aug 19th, 2009 by OutdoorsFIRST
Modified Aug 19th, 2009 at 12:00 AM
Fisheries Research 93 (2008) 248-252
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An evaluation of the injury and short-term survival of bonefish (Albula spp.) as
influenced by a mechanical lip-gripping device used by recreational anglers
Andy J. Danylchuka,b,*, Aaron Adamsc,d, Steven J. Cookea,b, Cory D. Suski a,e
a Cape Eleuthera Institute, Flats Ecology and Conservation Program, Cape Eleuthera, Eleuthera, The Bahamas
b Department of Biology, Carleton University, Ottawa, Ontario, Canada
c Bonefish & Tarpon Unlimited, Key Largo, FL, USA
d Mote Marine Laboratory, Sarasota, FL, USA
e Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL, USA
article info abstract
Received 10 February 2008
Received in revised form 1 June 2008
Accepted 2 June 2008
Mechanical lip-gripping device
Mechanical lip-gripping devices are becoming popular among recreational anglers as a means of holding
fish for hook removal and photos prior to release in an effort to minimize scale or slime loss from handling. To date, however, there has been no actual evaluation of the consequences of using such a device
on the health and survival of the fish. Using wild adult bonefish (Albula spp.) as the test organism, we
assessed the impact of a commonly used mechanical lip-gripping device on fish injury, behavior, and
survival in a seawater laboratory. Upon further review, this sentence would be more accurate if it read
“A detailed assessment of injury and short-term (<48 h) mortality was conducted for bonefish handled
with a mechanical lip-gripping device for 30 s either while being restrained horizontally in water or held
vertically in the air. A control group was also handled, but only with bare hands. Although no fish died
after 48 h, the lip-gripping device caused mouth injuries to 80% of bonefish restrained in the water and
100% of bonefish held in the air, always when fish thrashed while being held. Some of the injuries were
severe (40%) and included separating the tongue from the floor of the mouth, creating tears and holes
in the soft tissue of the lower jaw, and splitting the mandible. Anglers should use caution when using
mechanical lip-gripping devices for bonefish, at least until additional studies are conducted to help tease
apart how the risk of injury using mechanical lip-gripping devices on less exhausted individuals compares
to the risk of post-release mortality for fish exercised to exhaustion.
© 2008 Published by Elsevier B.V.
Catch-and-release angling is a management technique that,
under ideal circumstances, can allow anglers to utilize recreational
fish species with negligible impacts on fish populations (Muoneke
and Childress, 1994; Cooke and Suski, 2005; Arlinghaus et al., 2007).
The handling component of a catch-and-release angling event,
however, has the potential to injure, stress, or kill fish if not done
correctly (reviewed in Cooke and Suski, 2005; Arlinghaus et al.,
2007). Correctly handling the fish requires restraining it in a manner that limits injury to the fish and the angler, and allows the hook
to be quickly and safely removed prior to release.
To facilitate release, nets can be used to land fish, although some
mesh materials and sizes can remove slime or scales and fray fins
(Barthel et al., 2003). In marine systems, gaffs are also often used
Corresponding author at: Cape Eleuthera Institute, 498 SW 34th Street, Ft. Lauderdale, FL 33315, USA. Tel.: +1 609 945 0710; fax: +1 954 337 3799.
E-mail address: [email protected] (A.J. Danylchuk).
to assist with landing fish, but primarily when the catch is to be
kept rather than released. In rare cases, gaffs are used during catch-
and-release angling, such as for tarpon (Megalops atlanticus) when
the soft tissue behind the mandible is hooked as a way to restrain
these large fish prior to release. Tarpon, as well as other large fish
(e.g., muskellunge; Esox masquinongy) are also landed using soft
cradles (Margenau, 2007). Despite these devices to assist landing,
the most common way of landing fish is by hand, usually with
the angler gripping the fish behind the head or by the tail, or if
mouth morphology and dentition are appropriate, by gripping the
fish in the mouth (e.g., black bass, Micropterus spp.; common snook,
Holding a fish by hand during release might not be effective,
especially if the animal is thrashing; excessive thrashing can lead
to a fish being dropped or squeezed more firmly, thereby exacerbating stressors associated with the catch-and-release event (Ferguson
and Tufts, 1992; Cooke et al., 2001). Similarly, damage from handling (e.g., scale loss, bruising, slime loss) coupled with the stress
from an angling event can lead to opportunistic pathogen infections
that have the potential to kill fish. Furthermore, the handling event
0165-7836/$ – see front matter © 2008 Published by Elsevier B.V.
A.J. Danylchuk et al. / Fisheries Research 93 (2008) 248-252
itself can induce physiological disturbances, e.g., through air exposure (Ferguson and Tufts, 1992; Cooke et al., 2001), that ultimately
leads to post-release mortality (Danylchuk et al., 2007a,b).
Recent innovations in the fishing tackle industry have provided
anglers with new tools for handling fish intended for release. In
particular, there are now many different types of mechanical fish-
handling devices on the market that restrain the fish by firmly
gripping the lower lip or jaw. Many mechanical fish-handling tools
operate by using opposing metal plates (often “C” shaped) to grip
the lower lip of the fish, with one plate placed inside the mouth
on the lower jaw and one that opposes this plate but on the ventral surface outside the jaw. Such tools maintain a positive grip on
the lip of the fish without any gripping effort being exerted by the
angler because the weight of the fish serves to more firmly anchor
the fish-handling tool to the lower lip of the fish. These tools presumably allow the fish to be restrained by anglers using one hand,
leaving a second hand free to hold a fishing rod or remove the
hook, and allowing anglers to avoid touching the fish with their
hands. Because the weight of the fish is often used to secure the
prongs of mechanical lip-gripping tools, some of these devices have
integrated weight scales so that the fish can be weighed prior to
release. Springs used to weigh the fish may also act as an internal shock absorber that dampens motion to help reduce injury
to restrained fish. Some tools also incorporate a component that
rotates which can eliminate torque on the head of the fish when it
spins or thrashes.
Although the premise of mechanical lip-gripping devices is
to allow anglers to land their catch without having to touch a
fish, thereby reducing injury and post-release mortality related
to handling stress, to date there have been no formal assessments of these devices and their potential for causing physical
damage to fish. The angling community frequently debates the
potential for damage to mouth tissue or the spinal column
in fishing magazines and online forums, indicating its importance. Because mechanical lip-gripping devices continue to be
advocated as a way to properly handle catch, it is critical that
these tools be systematically tested to determine whether or not
they contribute to the conservation benefit of catch-and-release
The goal of this study was to evaluate a commonly used mechanical lip-gripping device and assess its use on the injury, behavior,
and survival of bonefish (Albula spp.). Bonefish were selected
because they are a common popular saltwater recreational sport-
fish for which catch-and-release rates approach 100% as a result of
a strong conservation ethic among this specialized angling group
(Cooke et al., 2006). Furthermore, the bonefish angling community
has a particular interest in this device, because it has the potential
to reduce slime loss during handling, which is a concern for this
group of fishes (see Cooke and Philipp, 2007).
2. Materials and methods
This study was conducted between 2 and 5 December 2007 at
the Cape Eleuthera Institute (CEI), Eleuthera, The Bahamas. Bonefish were collected from nearby tidal saltwater creeks using a seine
net stretched across narrow channels (45.72 m × 1.22 m, 1.22 m bag,
0.95 cm mesh; Danylchuk et al., 2007a,b). Once captured, bonefish
were transferred to submerged mesh pens for temporary holding
prior to transport back CEI. Fish were transported to CEI in large
plastic coolers (80-100 L) with no more than four fish per cooler.
Up to six complete water exchanges were made in coolers during
the 2-3 km trip from the creeks back to CEI. Once at CEI, aeration
was added to each cooler and the fish were allowed to rest for up
to 30 min.
Following the resting period, fish were exercised for 1 min in a
cooler, and then randomly assigned to one of three 30-s treatment
groups: (1) handling using a mechanical lip-gripping device with
the fish horizontal in the water, (2) handling using a mechanical
lip-gripping device with the fish held vertically out of the water,
and (3) restrained by hand while submerged, without the use of a
mechanical device (i.e., control). One minute duration of exercise
was used in this study since it is possible for an angler to retrieve a
bonefish in this amount of time, and that reducing the angling time
for bonefish is currently being promoted since prolonged exercise
has been shown to be physiologically taxing (Suski et al., 2007)
and potentially increase post-release predation (Danylchuk et al.,
The mechanical device used in this study was comprised of a
cylindrical tubular housing that defined the handle (outfitted with
a spring scale) and two opposing “C” shaped prongs at the terminal end of the device (Fig. 1). To use the device, the trigger was
pulled back, and the two opposing prongs were spread open. Once
open, one of the prongs was inserted into the mouth of the fish,
and the other was positioned under the lower jaw. Upon release of
the trigger mechanism, the prongs closed, and locked into place on
either side of the lower jaw. When suspended vertically to determine a weight, an internal spring mechanism in combination with
the mass of the fish locked the prongs even more tightly to the lower
jawbone of the bonefish. Ten fish were included in each treatment
and fish in all treatments were handled for a total of 30 s.
Fig. 1. Diagram of a typical mechanical lip-gripping device used for the handling of
recreationally angled fish. Image (A) shows the device with the jaws closed; arrows
associated with image (B) indicates the retraction of the spring-loaded handle and
opening of the jaws to be inserted into the mouth of fish.
A.J. Danylchuk et al. / Fisheries Research 93 (2008) 248-252
Following handling, fish were measured (TL and FL to nearest mm), given a differential fin clip according to treatment, and
placed in a 13,180 L flow-through seawater holding tank for 48 h.
Fish were not examined for specific injuries at this time because
extra handing may have influenced the condition of the fish independent of the use of the mechanical lip-gripping device. Instead,
fish were observed for signs of abnormal swimming patterns, loss of
equilibrium, or distress immediately after release into the holding
tank. Periodic observations were also made during the 48 h holding
Following the 48 h holding period, fish were removed from the
holding tank one at a time and examined for injuries to the lower
jaw and other parts of the body. Individuals were identified based
on their total lengths and their treatment group based on different
fin clips. Injuries were defined as visually observed physical damage
caused to the soft or hard structures of the bonefish. Damage to the
soft tissue could either be classified as non-perforated with no clear
opening through the skin and muscle, or perforated if the prongs of
the lip-gripping device had penetrated the soft tissue. Damage to
harder structures such as the bony tongue and the mandible were
also noted, and these injuries were considered severe. In all cases,
the physical dimensions of the injuries were measured using a ruler
or caliper, and a digital image was taken to catalogue the range of
potential injuries caused by mechanical lip-gripping devices.
Bonefish used in this study ranged in size from 380 to 540 mm
TL (±44 mm S.D.) and there was no difference in body size among
the three handling treatments (ANOVA, P = 0.6). No fish died during
handling or the 48 h holding period. Following the holding period,
only one fish in the control treatment showed any signs of injury
(minor inflammation inside the lower jaw), whereas 90% (18 of 20)
of fish in the mechanical lip-gripping treatments received injuries
to the lower jaw.
All bonefish suspended vertically in the air using the mechanical handling device received injuries (Table 1). Seven of ten fish
had perforations in the soft tissue between the mandible and
the isthmus, and perforations ranged in size from 5 to 28 mm
(mean = 15 ± 7.6 mm S.D.) and in shape from small circular holes to
long tears (Fig. 2A). Two of the bonefish with perforations suffered
a broken mandible (Fig. 2B) while a third fish had its tongue separated from the base of the mouth for a length of 15 mm. One fish
with a non-perforated wound obtained a separated tongue, resulting in a total of four fish in this treatment receiving severe injuries.
Other bonefish suspended vertically using the handling device had
less severe non-perforated injuries, such as shallow tears on either
the inside (n = 1) or outside (n = 2) of the mouth (Fig. 2C) ranging in
size from 3 to 19 mm (mean = 8.6 ± 8.6 mm S.D.). Six out of the ten
fish injured in this treatment obtained multiple injuries.
Eighty percent of bonefish held horizontally in the water using
the mechanical lip-gripping device received injuries (Table 1). Of
these fish, four received perforated wounds that ranged in size from
10-27 mm (mean = 19 ± 7.5 mm S.D.). Two bonefish held horizontally in the water suffered a broken mandible. The tissue injuries
associated with these broken mandibles were much more severe
(22 and 27 mm tears) than the tissue injuries obtained by the two
fish in the vertically held treatment that also had a broken mandible
(9 and 12 mm tears). Four fish held horizontally in the water had
their tongue separated from the base of the mouth, with tearing
ranging from 20 to 32 mm in length (mean = 25 ± 6 mm S.D.). Non-
perforated wounds occurred in two bonefish in this treatment and
the size of the wounds was 14 and 32 mm, respectively (Fig. 2D).
Three out of the eight bonefish injured in this treatment obtained
multiple injuries. Most of the injuries in this study occurred when
bonefish held by the restraint device thrashed and moved violently
and not as a result of compression or abrasion from the device itself.
The incidence of perforated wounds was significantly different
among treatment and control groups (Kruskal-Wallis, P = 0.006),
with the incidence of perforated wounds being higher for the treatments in which the mechanical lip-gripping device was used when
compared to the control. The incidence of perforated wounds was
not significantly different between the two treatments in which
the mechanical lip-gripping device was used (Mann-Whitney,
P = 0.25). The size of perforated wounds was also not significantly
different between the two treatments (t-test, P = 0.36). In addition,
there was no significant difference in the body size of bonefish
that received perforated wounds versus those that received non-
perforated wounds (t-test, P = 0.32 for fish held vertically in air,
P = 0.80 for fish held horizontally in water).
The results of our study indicate that mechanical lip-gripping
devices can inflict injury to the lower jaw of bonefish exposed to
exercise periods of 1 min. Regardless of whether the fish were held
horizontally in the water or vertically suspended in the air, 90% of
bonefish handled with the mechanical lip-gripping device received
injuries and 40% of these injuries were severe, including injuries
such as a broken mandible and/or detached tongue. Although none
of the bonefish in our study died during handling or 48 h holding
period, the injuries caused by the mechanical lip-gripping device
could have increased the fish’s susceptibility to infection and disease that could lead to impaired normal metabolic activity and
growth, if not death (Meka and Margraf, 2007). Serious injuries to
the lower jaw could also impair the ability of a fish to forage, which
may be especially acute for a benthivor such as bonefish. Even if
these injuries were to heal, delays in foraging that may result from
these injuries can have negative bioenergetic consequences (Meka
and Margraf, 2007). In addition, injuries caused by the mechanical
lip-gripping device during handing could exacerbate those incurred
during the angling event (e.g., hook damage).
The premise associated with these use of mechanical lip-
gripping devices as a tool that could reduce the impacts of handing
is laudable. Indeed, in instances when a bonefish is to be released,
any efforts that reduce handling time (Danylchuk et al., 2007b) and
the amount of contact between the fish and other materials (hands,
nets, gloves, etc.) should be beneficial. In principle, gripping a bonefish by the mouth via two opposing plates would seem to be a
logical means of controlling the fish for hook removal and obtaining a weight. Although we did not quantify the specific degree of
thrashing, however, there is also potential for injury from using the
device when bonefish restrained by these devices thrash.
At a minimum, our results indicate that bonefish exercised for
1 min should not be held out of water using lip-gripping devices due
to the potential for severe tissue damage. If bonefish are suitably
exhausted, the use of mechanical lip-gripping devices may have
some merit such that their thrashing and activity levels will likely
be reduced. In some situations, however, it has been shown that
it is undesirable to angle bonefish to exhaustion since it increases
the likelihood of post-release predation (Cooke and Philipp, 2004,
2007; Danylchuk et al., 2007b). One benefit of mechanical lip-
gripping devices is that they can be used to hold fish in the water
thus minimizing air exposure, reducing physiological stress (Suski
et al., 2007) and the loss of equilibrium that can influence the incidence of post-release predation (Danylchuk et al., 2007a,b).
Systematically examining the influence of specific elements of
the angling event is critical for the development of scientifically
A.J. Danylchuk et al. / Fisheries Research 93 (2008) 248-252
Fig. 2. Injuries sustained to bonefish using a mechanical lip-gripping device. (A) A perforated tear in the tissue posterior of the mandible and extending parallel along the
isthmus. (B) A bonefish with a broken mandible. (C) A non-perforated wound on the inside of the mouth posterior to the mandible. (D) A wound similar to that visible in (A),
however no perforation was made by the mechanical lip-gripping device.
based best practices that can act as guidelines for recreational by seine, the collective influence of then being transferred to cool-
anglers. For instance, in our study we captured bonefish using a ers, transported 3 km by boat, and then chased for 1 min prior to
seine net rather than via angling to eliminate confounding injuries handling, likely exhausted tissue energy stores and cause physiopotentially caused by hooking. Although these fish were captured logical disturbances consistent with an angling event (Suski et al.,
Number of bonefish and injuries they received in each handling treatment
Treatment Non-perforated wound
in lower jaw
Perforated wound in
Tongue separated from
base of mouth
Suspended vertically in air
Held horizontally in water
N = 10 fish sampled in each treatment, and multiple injuries occurred for some fish.
A.J. Danylchuk et al. / Fisheries Research 93 (2008) 248-252
2007; Cooke et al., in press). Nevertheless, additional studies need
to be conducted on bonefish in a controlled laboratory setting using
a range of handling times as well as field studies on angled fish to
help tease apart how the risk of injury using lip-gripping devices on
less exhausted individuals compares to the risk of post-release mortality for fish exercised to exhaustion. It would also be important to
examine the long-term tradeoffs between a bonefish that is poorly
handled using bare hands, net, or cradle (resulting in potential scale
and slime loss), relative to bonefish with mouth injuries potentially resulting from a lip-gripping device. Given that our study only
examined obvious external injuries, additional studies need to be
conducted to determine whether the use of lip-gripping devices
also result in internal injuries, such as vertebral separation due to
the fish being suspended vertically out of the water.
As with all gear-related innovations in the recreational fishing
industry that potentially affect fish injury, condition or survival,
there is a need for independent scientific investigations to determine if the innovations are truly beneficial to fish prior to their
wide adoption by anglers (see Pelletier et al., 2007). Because our
study revealed that the opposing prongs are the origin of the tissue
damage, there may be some opportunity to refine the configuration
(shape, size) of the prongs to minimize tissue damage to bonefish.
Again, such refinements may not work on all species (see discussion of the need for species-specific evaluations in Cooke and Suski,
2005) since some devices may not be appropriate for different
mouth morphologies. Until additional studies are conducted, we
urge anglers to use caution when using lip-gripping devices and
to monitor scientific developments to ensure that best practices
are used to optimize the conservation benefits of catch-and-release
angling. For bonefish in particular, we encourage anglers to use a
pair of hemostats to gently remove barbless hooks while the fish is
held in the water. In addition, if a fish is to be removed for admiration or photography, we urge that the fish be gently supported
underneath with wet hands just above the water surface for the
shortest duration possible.
This research was supported by Cape Eleuthera Institute, the
Cape Eleuthera Foundation, Bonefish & Tarpon Unlimited, Carleton
University, the University of Illinois, and The Bahamas Department
of Marine Resources. We gratefully acknowledge David Philipp,
Jeff Koppelman, Edd Brooks, Aaron Schultz, Katrina Cook, and
Amanda Lilleston for assistance with experimentation, and Sascha
Danylchuk and two anonymous reviewers who provided useful
comments on an earlier version of this manuscript. Thanks also
to Vanessa Proctor who provided valuable assistance with fig
ures. Lastly, we like to thank Jim Shulin (Temple Fork Outfitters),
Bruce Richards (Scientific Anglers) and Lou Tabory (Albright Tackle)
for their continued support of our research on catch-and-release
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