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FINAL REPORT
State: Maryland Project No.: F-48-R
Study No.: VI
Job No.: 2
Project Title: Survey, Inventory, and Management of Maryland's
Freshwater Fisheries Resource
Study Title: Hooking Mortality Studies
Job Title: Gear Type and the Associated Hooking Mortality on
Trout Populations
Job Objectives: To measure the differential hooking mortality of
wild trout associated with gear type.
Duration: January 1, 1991 through December 31, 1994.
INTRODUCTION
The purpose of this study was to determine if there is a difference in hooking
mortality rates among trout associated with gear type. Specifically, we compared
mortality rates produced by treble hook equipped artificial lures and single
hook flies.
The study was conducted on the Savage River tailwater. The study area was 4.5
miles in length and is managed as a trophy wild trout fishery for brook and
brown trout. Regulations permit the use of single hook flies fished from
conventional flyfishing tackle on the first 1.3 miles; the remaining 3.2 miles
are open to fishing with artificial lures equipped with treble hooks or flies.
Anglers may creel two trout per day. Minimum creel length is 12 inches (305 mm)
for brook trout and 18 inches
(457 mm) for brown trout. The Savage River tailwater is not stocked with
hatchery trout.
METHODS
Angling effort by volunteer fisherman and Fisheries Service personnel was
divided between two gear types: artificial lures equipped with a single treble
hook and single hook flies. Twelve study exercises were conducted from 1991
through 1994. All trout were landed and unhooked by hand. No landing nets,
forceps, or hook disgorgers were used. Fisherman used identical six lure
assortments consisting of locally popular treble hooked spinners (hook sizes 12
and 14) that included Panther Martin, Mepps, and Roostertail. They used a
variety of single hook artificial flies (hook sizes 10 through 18). All
artificial lures and flies were equipped with barbed hooks.
Captured trout received partial fin clips to identify hooking location according
to the following code (Figure 1):
bleeding fish: adipose clip plus one of the following;
upper or lower jaw (lip area) - no mark
roof of mouth - top of caudal
floor of mouth - bottom of caudal
gill arches - right pelvic
esophagus - right pectoral
eye - left pelvic
outside of mouth (except eye) - left pectoral
All captured fish were placed in lidded, five gallon plastic buckets and then
transported to a holding site approximately midway in the study section. There
they were transferred to perforated, lidded plastic holding boxes 27 in long x
16 in high x 12 in depth. A separate holding box was provided for each fisherman
and gear type. Freshwater Fisheries personnel assigned to transport fish visited
each angler at about 10 to 15 minute intervals. Transport time to the holding
area was less than five minutes. Captured trout were held for 48 hours after the
end of the exercise and observed for delayed mortality every 12 hours. Trout
species, total length, hooking location, gear type, and survival were recorded
for each fish at the end of each sampling exercise. Total angling hours by gear
type for each fisherman was also recorded. Surviving trout were redistributed in
the study section.
No delayed mortality was observed in 48 hours of post capture observation during
the first exercise, all mortalities occurring within the first hours after
capture. In order to best utilize available time and manpower, the 11 subsequent
experiments were conducted using an identical procedure except that observations
of mortality were limited to the duration of each sampling exercise, with no
prolonged confinement for the purpose of evaluating delayed mortality. Captured
trout averaged about four hours in confinement (range approximately two to six
hours).
Angler gear preference data was collected via on stream interviews conducted
between March and June 1994 on the Savage River tailwater. Fisherman were
queried regarding the lure design, hook type, and hook size of terminal tackle
in use at the time of the interview.
Statistical comparison of means were carried out using SAS (SAS Institute 1982)
at the .05 significance level.
RESULTS
During the study discharge volumes from the Savage River Dam ranged from 35 to
55 ft³/s and water temperature varied from 10.5C to 16.1C.
Twelve volunteers and eight Fisheries Service personnel participated in 12 study
exercises (Table 1). Anglers fished 116.5 hours with artificial lures and 116.5
hours with artificial flies. They captured 237 wild trout (197 brook and 40
brown) with artificial lures for a pooled catch rate of 2.0 trout/h. Mean catch
rate by study exercise for spin fishing was 1.7 + 0.5 trout/hour.
Anglers caught 199 wild trout (130 brook and 69 brown) with artificial flies for
a pooled catch rate of 1.7 trout/hour. Mean catch rate by exercise for
flyfishing was 1.8 + 0.5 trout/hour.
Mean catch rates were not significantly different between gear types when brook
and brown trout samples were combined. When treated separately, however, catch
rates differed significantly for both species (Table 2). Brown trout were more
vulnerable to capture with flies than with artificial lures, while brook trout
were most easily captured with artificial lures. For either gear type, brook
trout were more vulnerable to capture than brown trout in the Savage River
tailwater.
Total mortality was 18 trout (17 brook, 1 brown) or 7.6% of 237 trout caught
using artificial lures. Ten anglers, four volunteers and six Freshwater
Fisheries personnel, accounted for the 18 mortalities. The mean mortality rate
(and 95% confidence interval) by exercise for artificial lures was 7.9% + 2.5%,
(Table 1). Mortality associated with artificial lures was highest among brook
trout; 8.7% + 2.7% (N=197) versus 0.7% + 1.2% for brown trout (N=40) (Table 2).
No mortalities were observed among the 199 trout captured with artificial flies.
The mean lengths of brook and brown trout are presented in Table 2. Fisherman
caught significantly smaller trout with artificial lures than with flies,
particularly among brown trout. The average length of brook and brown trout
captured with artificial lures was almost identical while brown trout captured
with flies were larger on average than brook trout taken on the same gear.
The average length of brook and brown trout collected during population surveys
conducted in the Savage River tailwater for the years 1991 through 1994 is
presented in Table 3 (Pavol and Klotz, 1991-1994). Brook and brown trout
captured with artificial lures were smaller than the average size of adult trout
present in the Savage River tailwater during the study period, 1991 through
1994. However, the average lengths of brook and brown trout caught on flies were
not significantly different than the average lengths of the adult fish present
during the study period.
Of the 18 mortalities, 17 were brook trout that averaged 179 + 14mm; not
significantly different than the overall mean length for brook trout caught with
spinners. The single brown trout mortality was 168 mm long, similar to the mean
of brown trout captured with spinners.
The most common hooking location for trout captured with flies was the upper or
lower jaw (86.4%). Trout caught with spinners tended to be hooked more deeply
within the mouth than trout hooked with flies; either in the roof or floor of
the mouth (or both), or in the gill arches. Only 42.6% of trout caught on
spinners were hooked in the jaw. Of the eighteen mortalities associated with
artificial lures, 12 were hooked in the gill arches, five were hooked in both
the roof and floor of the mouth, and one was hooked in the eye.
The proportions of non-jaw hooked trout, bleeding trout, and mortality by gear
type are compared in Figure 2. Trout captured with artificial lures were hooked
in an area other than the jaw 57.4% of the time (65.7% of brown trout and 56.8%
of brook trout), 27.8% were bleeding when unhooked (12.5% of brown trout and
31.0% of brook trout), and 7.6% died. Of the fly caught sample, 13.6% were
hooked in an area other than the jaw, only 2.5 % were bleeding, and none died.
DISCUSSION
The artificial lures and flies used in this study were equipped with hooks small
enough to be ingested deeply even by trout of less than 200 mm. Warner (1978)
noted that smaller treble hooks (size 10) were more easily ingested than single
hook flies and caused significantly higher mortality. We found that treble hook
equipped lures were difficult to disengage from captured trout, particularly
when hooked within the mouth or in the gills. This increased the time required
to unhook the trout and thus the actual handling of the fish. Nuhfer and
Alexander (1989) reported that the treble hook equipped Mepps spinners used in
their hooking mortality study were more difficult to unhook from anatomical
sites within the mouths of wild brook trout than were single hooks. We found
that single hook artificial flies were generally less difficult to unhook than
treble hooks and required less handling of the trout.
The spinner type artificial lures used in this study were equipped with small
treble hooks that are characteristic of the sizes used by anglers on the Savage
River Tailwater. An on stream angler survey conducted by Fisheries Service
personnel from March through June 1994, revealed that the average hook gape of
treble hook equipped lures in use was 4.7 mm (range: 4 to 8 mm, N= 23). The size
12 and 14 treble hooks on artificial lures used in this study had hook gapes of
4 and 5 mm respectively. All but two of anglers interviewed were using a spinner
type lure similar to those used in the study. Flyfisherman interviewed during
the survey were using single hooked flies with an average gape of 5.1 mm (range:
3 to 8 mm, N= 36), comparable to the 3 to 7 mm hook gapes found on the single
hook flies used in this study. Fisherman were also asked if they carried
specific tools for hook removal. Thirty five of 36 fisherman (97%) using
artificial flies carried some form of forceps for hook removal while 11 of 23
fisherman (48%) using artificial lures carried forceps or pliers.
It is clear that trout caught on treble hook equipped artificial lures in this
study sustained more physical trauma than those captured on single hook flies,
as evidenced by the higher incidence of bleeding fish. Over half (57.4%) of
trout captured on spinners were hooked in a location other than the jaw and
27.8% were bleeding when unhooked. Only 13.6% of trout captured with flies were
hooked in a location other than the jaw and only 2.5% of those were bleeding
when unhooked. Mongillo (1984) concluded that salmonids hooked in a non-jaw
location (gills, esophagus, tongue, or eye) were four times more likely to die
regardless of hook type. Although trout captured in our study were not observed
for more than about 4 to 6 hours, the relatively greater physical damage and
bleeding observed among trout captured with artificial lures versus flies
supports the premise that a larger proportion of trout caught on lures would
experience delayed mortality.
Warner and Johnson (1978) noted that 86% of landlocked Atlantic salmon that were
bleeding at capture died. If bleeding at capture is considered a predictor of
eventual mortality, then spinner hooked trout in this study were about 11 times
more likely to experience delayed mortality than fly caught trout. Brown trout
hooked on artificial lures were less likely to bleed than brook trout (12.5%
versus 31.0%) although the proportion of non-jaw hooked brown trout was slightly
greater than for brook trout. The reasons for differential bleeding are not
clear, but may be related to differences in the relative degree to which brook
and brown trout struggled during capture. However, no attempt was made to
characterize the relative degree to which brook and brown trout struggled when
hooked during this study. The higher proportion of brook trout that were
bleeding when captured with treble hook equipped spinners may account for the
higher mortality that we observed among brook trout. As noted earlier, anglers
routinely use artificial lures with small treble hooks on the Savage River
tailwater, enabling trout of modest size to engulf the lure deeply.
Shetter and Allison (1955 and 1958) reported 0.0% hooking mortality for brown
trout captured with artificial flies (N=109) and a 3.0% hooking mortality for
brown trout caught on artificial lures with barbed treble hooks (N=67). We
observed no hooking mortality among 69 brown trout captured on flies in this
study and a 0.7 + 1.2% hooking mortality for brown trout captured with treble
hook equipped lures (N=40). Because artificial lures produced a relatively low
catch rate (0.3 trout/h) and low mortality rate for brown trout in the Savage
River tailwater during this study, we believe is unlikely that their use has any
measurable effect on the brown trout population. The same can be said for the
use of single hook artificial flies in the Savage River tailwater.
Shetter and Allison (1958) reported a hooking mortality rate of 3.9% for brook
trout captured with treble hook equipped lures (N=382), lower than the 8.7 +
2.7% observed in this study. In a compilation of many studies, Wydoski (1977)
reported that hooking mortality was 6.1% for salmonids hooked on artificial
lures, within the 95% confidence interval for brook trout hooking mortality
measured in this study. Nuhfer and Alexander (1989) observed an 8.3% mortality
rate among wild brook trout captured with Mepps spinners and Cleo spoons
equipped with treble hooks. They noted that the mortality rate for wild brook
trout captured on the same lures equipped with single hooks was significantly
lower at 2.4%.
Population studies carried out on the Savage River tailwater from 1991 through
1994 (Pavol and Klotz, 1993 and 1995) indicate that adult brook trout were more
abundant in the portion of the Lower Savage River which is restricted to
flyfishing only compared to the area open to the use of artificial lures or
flies (472 fish/mile and 343 fish/mile respectively). It is not clear to what
degree the difference can be attributed to hooking mortality. The adult brown
trout population, which exhibited a low vulnerability and low hooking mortality
associated with artificial lures, was distributed similarly. An average of 527
brown trout/mile were present in the flyfishing only area of the Savage River
tailwater from 1991 through 1994, while a mean population of 395 brown
trout/mile was measured in the area where the use of artificial lures is
permitted during the same period.
Although no comprehensive survey of angler gear preference has been conducted on
the area of the Savage River tailwater where artificial lures or flies may be
used, routine observations by Freshwater Fisheries personnel indicate that the
use of spinning tackle is not as common as fly tackle. Fedler (1988), in a
survey of Maryland trout fisherman, noted that 70 percent of anglers who fished
with artificial baits used flyfishing gear exclusively. Fedler also identified
the Savage River as the most popular trout fishing destination in Western
Maryland and the second most frequently fished trout stream in Maryland.
A key question is how much recreational fishing pressure by anglers using
artificial lures equipped with treble hooks can the brook trout population of
the Savage River tailwater sustain. Age and growth studies have indicated that
adult brook trout rarely exceed 12 inches in length in the Savage River
tailwater. Therefore, angler harvest probably represents a negligible proportion
of annual mortality.
Natural mortality rates of wild brook trout in the Savage River tailwater are
not known. However, we can estimate the degree of angling effort with artificial
lures equipped with treble hooks that will result in a proportionate reduction
of the wild brook trout population given our known variables regarding
population size, mortality rate, and catch rate. For example, the average annual
total population of wild adult brook trout in the Savage River tailwater where
the use of artificial lures is permitted was 1098 fish during the study period
(derived from Pavol and Klotz, 1992-1995). Anglers using artificial lures in the
Savage River tailwater killed 8.7% + 2.7% of brook trout captured during this
study. They caught brook trout at a rate of 1.7 fish/h with artificial lures. If
it is assumed that the brook trout catch rate is reduced proportionately as
mortalities occur, the catch rate will average 1.275 fish/h for the initial 50%
of the original population. By applying our catch rate and hooking mortality
rate to the average population, we find that a daily average of 13.5 hours of
fishing effort with artificial lures will reduce the population of adult brook
trout by about 50% in one year in the 3.2 mile reach of the Savage River
tailwater where the use of artificial lures is permitted, exclusive of the
unknown effects of natural mortality. That level of effort is equivalent to
about one artificial lure angler per day per mile, given an average fishing day
of 4.0 hours.
Our study did not evaluate the hooking mortality associated with artificial
lures equipped with single hooks, although single hook artificial flies did not
produce a mortality among 199 wild brook and brown trout captured. As noted
earlier, Nuhfer and Alexander (1989) measured a brook trout mortality rate of
8.3 percent for Mepps spinners equipped with a treble hook, in close agreement
with the 8.7 percent mortality rate among brook trout captured with treble hook
equipped spinners that we observed in the Savage River tailwater. They also
observed that the mortality rate among brook trout captured on identical
artificial lures equipped with single hooks was 2.4%, or less than one third of
that for treble hook equipped lures. If the mortality rate among brook trout in
the Savage River tailwater was reduced to a similar degree by the use of single
hook artificial lures, then the level of fishing effort described in the
preceding paragraph (1.0 anglers per day per mile) would produce a total annual
mortality of about 14 percent of the adult brook trout population, given the
assumptions stated in the preceding paragraph.
CONCLUSIONS
Single hook artificial flies did not produce any observed mortalities among 199
wild brook and brown trout captured in the Savage River tailwater.
Brown trout in the Savage River tailwater exhibited a low vulnerability to
capture with artificial lures and a low mortality rate when caught on artificial
lures equipped with treble hooks. The use of artificial lures probably does not
produce a measurable effect on brown trout in the Savage River tailwater.
Brook trout in the Savage River tailwater were subject to a significantly higher
mortality rate than brown trout when captured on the same treble hook equipped
artificial lures. In addition, relatively low levels of angler effort with
treble hook equipped artificial lures will produce disproportionately higher
mortality among brook trout in the Savage River tailwater.
RECOMMENDATIONS
The use of single hook artificial flies should continue to be permitted on
the Savage River tailwater.
The regulation regarding artificial lures currently in effect on the Savage
River tailwater should be modified to require the use of single point hooks
only.
Prepared By :
Kenneth W. Pavol
:
Alan W. Klotz
Date :
LITERATURE CITED
Fedler, A. J. 1988. Trout Fishing in Maryland, an Examination of
Angler Characteristics, Behaviors, and Economic Values. Md.
DNR, Tidewater Adm., Annapolis, Md. 101 pages.
Mongillo, P. E. 1984. A summary of hooking mortality. Washington
Department of Game, Fish Man. Div., Seattle. 46 pages.
Nuhfer, A. J. and R. A. Gaylord. 1989. Hooking mortality of
trophy-sized wild brook trout on artificial lures. Michigan
DNR, Fish. Res. Report No. 1963. 15 pages.
Pavol, K. W. and A. W. Klotz. 1993. Survey and inventory of
coldwater fisheries resources, Lower Savage River trout
population studies. Fed. Aid Study Proj. F-48-R-1, Study
No. III, Job No. 2. Md. DNR, Freshwater Fish. Div.
_____________________________ 1995. Survey and inventory of coldwater fisheries
resources, Lower Savage River trout
population studies. Fed. Aid Study Proj. F-48-R-1, Study
No. III, Job No. 2. Md. DNR, Freshwater Fish. Div.
SAS Institute. 1989. SAS/STAT user's guide, version 6, 4th edition, vol 1. SAS
Institute, Cary, North Carolina.
Shetter, D. S. and L. N. Allison. 1955. Comparison of mortality
between fly-hooked and worm-hooked trout in Michigan streams.
Mich. Dep. Conserv. Inst. Fish. Res. Pub. No, 9, 44 pages.
_________________________________ 1958. Mortality of trout caused
by hooking with artificial lures in Michigan waters, 1956-57.
Mich. Dep. Conserv., Inst. Fish. Res. pub. no. 12, 15 pages.
Warner, K. W. 1978. Hooking mortality of lake dwelling landlocked
Atlantic salmon, Salmo salar. Trans. Amer. Fish. Soc. 107 (4)
pp. 518-522.
____________ and P. R. Johnson. 1978. Mortality of landlocked
Atlantic salmon (Salmo salar) hooked on worms and flies in a
river nursery area. Trans. Amer. Fish. Soc. 107 (6)
pp. 772-775.
Wydoski, R. S. 1979. In: A national symposium on catch and release fishing as a
management tool. R. A. Barnhart and
T. D. Roelofs, Eds. Humbolt State U. Arcata Ca. pp. 43-87.
Table 1. Summary of Angler Effort and Associated Hooking Mortality in the Savage
River tailwater, 1991 - 1994.
Gear Type
Parameter Measured Spin Fly
Total Hours Effort 116.5 116.5
Total Catch 237 199
Catch Rate Per Hour - pooled 2.0 1.7
Mortality Rate - pooled 7.6 % 0.0%
Mean Mortality Rate by Exercise 7.9+2.5% 0.0%
=========================================================
Number of Study Exercises = 10 spin, 12 fly
Number of Anglers = 20
Table 2. Average Lengths, Catch Rates by Gear Type, and Mortality Rate by
Species for trout in the Savage River tailwater, 1991 - 1994.
Spin Fly
Brook Trout
Total Catch 197 130
Catch Rate/Hour 1.7 1.1
Avg. Length mm 175 203
Total Mortalities 17 -0-
Avg. Mortality Rate 8.7 + 2.7% -0-
Brown Trout
Total Catch 40 69
Catch Rate/Hour 0.3 0.6
Avg. Length mm 174 265
Total Mortalities 1 -0-
Avg. Mortality Rate 0.7 + 1.2% -0-
=================================================================
Table 3. Average length of adult brook and brown trout collected during
population studies in the Savage River tailwater, 1991-1994 (Pavol and Klotz,
1993 and 1995).
Year Brook Trout L N Brown Trout L N
1991 207 mm 270 280 mm 172
1992 190 mm 275 229 mm 323
1993 178 mm 201 259 mm 289
1994 228 mm 103 297 mm 242
----------------------------------------------------------------
All Years 197 mm 849 262 mm 1026
=================================================================
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