Background
and issues addressed
Rapidly
increasing angler use of the Alagnak River rainbow trout fishery
since the early 1990’s led to concerns about the health of the
population(s) and resulted in regulatory changes to catch-and-release
fishing only beginning in 1996. Determined by the number of
angler days per year, the Alagnak River is one of the most heavily
used trout sport fisheries in the southwest Alaska wild trout
management area. Alagnak River rainbow trout are subjected to
stresses including exhaustion during the landing process, handling
and air exposure during hook removal, and a high probability
of hook injury with heavy catch-and-release fishing pressure.
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Map
of the Alagnak River Drainage |
The effects of high incidences of catch-and-release
captures on the physiological response by trout to acute stress
and any sublethal effects resulting from hooking injuries remain
unknown. Mortality and sublethal effects such as changes in
reproductive behavior, resistance to disease, and growth suppression
or a decrease in appetite have been an observed response by
fish subjected to different types of acute stress. Fish with
sublethal injuries may be at risk to opportunistic organisms,
disease, or fungal infection, and certain injuries, such as
eye injuries, may influence the feeding habits of fish. In 1997
and 1998, USGS biologists captured approximately 2100 rainbow
trout, the majority of which were caught by hook and line. The
number of obvious previous hooking scars was recorded for 1900
individual captured Alagnak River rainbow trout and over 30%
of those captured had at least one distinctive mutilation most
likely due to previous hooking. Numerous cases of angler dissatisfaction
due to trout deformities or injuries purportedly resulting from
repeated hooking by anglers have been reported to USGS biologists.
The detrimental aesthetics of injured trout have reduced the
overall appreciation of the Alagnak River by many anglers traveling
to Alaska to fish pristine waters. Research on the various factors
that influence hooking injury and the duration of the angling
process may provide supplemental information essential in evaluating
ways to reduce the severity of hooking injuries, angling mortality,
and associated sublethal effects of Alagnak River rainbow trout.
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Fishing
for rainbow trout in the main stem of the Alagnak River |
Objectives
The
goals of this study were to assess the incidence of hooking
injury and measure the immediate physiological stress response
to the duration of angling and handling during hook removal.
We will address the issues of whether different tackle, methods
of fishing (fly vs. spin), time fish are played and landed,
experience level of anglers, and water temperature influence
the physiological stress levels (cortisol, glucose, lactate,
and ions) and hooking injuries in rainbow trout.
Methods
Physiology
- Fish greater than 254 mm FL were sampled for blood chemistry
during the summers of 2000-2002. Rainbow trout were anesthetized
using a clove oil solution and blood was withdrawn from the
caudal vessels. Fish recovered in a tub of freshwater and were
released near their capture when equilibrium was reached and
normal swimming activity resumed. Using a field camp “lab” that
was set up on the boat, blood samples were centrifuged and plasma
was extracted. Plasma samples were stored in liquid nitrogen
tanks and eventually transported to a freezer for analysis at
the USGS Conte Anadromous Fish Research Center (http://www.lsc.usgs.gov/caflindex.asp).
Different portions of each capture and sampling procedure were
timed for fish that were to be sampled for blood chemistry.
The timed events included: from the point a fish was hooked
until it was landed, time to remove hook, time in clove oil,
time fish was sampled for blood, and recovery time. Upon release,
fish were followed by foot until out of sight and behavior was
recorded (also a timed event).
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Drawing
blood from the caudal vessels of rainbow trout
following catch-and-release fishing. |
Hooking
injury
- Rainbow trout were caught by hook and line using different
types of terminal gear in the Alagnak River and at outlets of
Nonvianuk and Kukaklek lakes. Method of fishing (fly or spin)
and hook type (circle hook barbed and barbless, J hook barbed
and barbless) each angler used were randomized twice daily.
All captured fish were weighed (g), fork length (mm) measured,
and examined for present or past hooking injuries. Angler experience
was classified as novice (fished < 10 days over their lifetime)
and experienced (fished > 10 days per year) based on the
fishing experience of anglers participating in this study. Anglers
consisted of USGS and NPS biologists and volunteers, and volunteers
from other governmental agencies or the general public.
Fish
were not held after capture to monitor mortality rates or the
duration of the physiological response to avoid any associated
stress or injury resulting from confinement.
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Collecting
measurement and hooking injury data from captured rainbow
trout |
Physiology
– The levels of plasma cortisol and lactate were evaluated in
fish landed and handled for less than 2 minutes (rapid capture)
and greater than 2 minutes (extended capture). Plasma cortisol
and lactate increased significantly as the duration of the angling
process (landing and handling combined) increased. Levels of
plasma glucose and ions (sodium, chloride, potassium) did not
differ significantly in relation to the duration of the angling
process, water temperature, or length. The duration of the angling
process was significantly related to fish size, i.e. larger
fish took longer to land and handle than smaller fish. Water
temperature varied significantly among years, and the levels
of plasma cortisol and lactate were significantly higher in
years with higher temperatures. Plasma cortisol and lactate
concentrations increased with the amount of time fish were angled
regardless of the temperature range, however, the magnitude
and range of the response was higher in when temperatures were
warmer.
Hooking
injury:
Hooking injury results were similar in all years and methods
remained consistent, thus the data were combined. Hooking injuries
were defined as present if there was sufficient tissue damage
to external areas that would lead to a permanent scar or if
the injuries occurred in sensitive areas (e.g. tongue, gills),
and past injuries were old injuries thought to have resulted
from previous capture by angling. The majority of fish captured
were hooked in the upper or lower external jaw (71%), with the
eye or eye and jaw (10%) being the next most common hook locations.
About 30% of fish captured had at least one previous hooking
scar (mean fork length 410 mm) indicating a substantial portion
of the population is subjected to multiple captures.
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An
example of an Alagnak River trout with no obvious hooking
scars |
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Rainbow
trout with a torn maxillary from being previously caught
and released |
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Rainbow
trout with missing maxillary and 2 scars on the chin (gular
region) |
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Rainbow
trout with missing maxillary |
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Rainbow
trout with inverted maxillary from being previously caught
and released |
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Rainbow
trout with missing eye from being previously caught and
released |
Fifty-eight
(n=386/666) percent of fish captured by hook and line experienced
at least one new hooking injury (which would lead to a scar
or was in a sensitive area). There was no significant difference
in the proportion of newly injured fish caught with J hooks
by fly fishing (57% injury rate) or spin fishing (62% injury
rate), or fish injured while fly fishing with circle hooks (46%
injury rate) compared to J hooks (56% injury rate). However,
when examining internal injuries only, internal injuries (e.g.
tongue, gills, eye, and esophagus) were more frequent in fish
caught using J hooks compared to circle hooks, and internally
hooked fish bled more frequently than fish hooked externally.
Bleeding from new hooking injuries occurred in 25% of fish captured.
Of fish injured using fly and spin fishing gear with J hooks
(n = 355), significantly more fish were injured when caught
using barbed hooks (67% injury rate) than with barbless hooks
(50% injury rate). Barbed J hooks were more efficient at landing
fish than barbless hooks, with fewer fish lost using barbed
hooks, and J hooks were more efficient at landing fish than
circle hooks. Barbed J hooks also took significantly longer
to remove than barbless hooks. Novice anglers injured proportionally
more fish than experienced anglers (70% and 56% injury rate,
respectively). Experienced anglers took significantly longer
to land fish than novice anglers. There was little variation
in the size of fish injured in this study that were caught fly
or spin fishing, or caught with barbed or barbless hooks. The
degree of injury, as indicated by medium to heavy blood flow,
was slightly higher in fish captured with barbed hooks (15%)
as compared with barbless hooks (10%) for both fishing methods.
Immediate mortality was observed in 8 fish (1.2%), the majority
of which were hooked internally and experienced moderate to
heavy bleeding from the hook wound or gills.
Management
Implications
The
results of this study will have direct application for management
decisions regarding catch-and-release fishing throughout cold-water
regions, and will provide specific recommendations for management
tools to restore the naturally occurring rainbow trout population
in the Alagnak Wild River to a more pristine state.
Barbed
J hooks caused significantly more new hooking injuries, took
longer to remove, and were more efficient at catching fish than
barbless hooks in this study. A restriction on barbed J hooks
would reduce the frequency of injuries and associated bleeding
rates, and reduce the amount of time fish are handled when removing
hooks. Although circle hooks were not as efficient at landing
fish as J hooks, and the overall injury rates were similar between
circle and J hooks, the frequency of internal injuries were
much less using circle hooks. Numerous studies on the effects
of hooking injuries on mortality indicate that fish hooked in
sensitive internal areas suffer the highest initial mortality
rates. The use of circle hooks could provide benefits to minimize
mortality by lessening the frequency of internally hooked fish,
yet the poor catch efficiency of circle hooks may make them
undesirable for use by anglers.
Initiating
angler education programs focusing on proper hook removal techniques
and the importance of quick landing times to minimize the physiological
response could potentially reduce injury rates and sublethal
effects associated with landing and handling times. Minimizing
the duration of the angling process will ultimately reduce the
peak physiological response and duration of recovery of angled
fish, particularly at warmer water temperatures. As the popularity
of angling for wild rainbow trout continues to rise in Alaska,
resulting in heavier angling pressure and catch-and-release
regulations, managers will need to consider the physiological
impacts of multiple recaptures on the response of wild fish
and the sublethal effects resulting from hooking injuries and
the duration of angling on individual rainbow trout, and trout
populations.
Manuscripts
in preparation.
Contact
Information
Julie
Meka
Fishery Biologist
USGS, Alaska Science Center
Biological Science Office
1011 E. Tudor Rd., MS 701
Anchorage, AK 99503
(907) 786-3917
(907) 786-3636 FAX
email: julie_meka@usgs.gov
USGS
Crew #1 of 2002 -
From left to right, Brian Byrne (volunteer), Julie Meka
(USGS), Dan Parker (volunteer), Jim Pikul (volunteer),
and Elliot Aguillor (NPS). Not pictured, Brad Hanson (volunteer)
and Steve McCormick (USGS). |
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USGS
and SCA
Alagnak Crew of 2001
left to right - Duncan Oswald (USGS), Bob Frampton (SCA),
Julie Meka (USGS), Ryan Gray (SCA), and Phil Richards
(USGS) |
USGS,
NPS, and SCA Alagnak Crew of 2000
left to right - Derek Wilson (USGS), Julie Meka (USGS),
Chris Wall (NPS), and Ryan Beatty (SCA) |
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