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Feasibility of Initiating a Commercial Fishery for Paddlefish in Alabama Reservoirs of the Tennessee River

Authors:

Abstract

In recent years, commercial paddlefish harvesters have renewed their requests for opening a potential commercial paddlefish (Polyodon spathula) season in Alabama reservoirs of the Tennessee River, including part of Pickwick Reservoir, all of Wilson and Wheeler reservoirs, and the majority of Guntersville Reservoir. These reservoirs of the Tennessee River once supported robust stocks of paddlefish; however, beginning in the 1940s overexploitation became evident as the number of paddlefish harvested declined. Because of this widespread overharvest, a commercial and recreational moratorium on paddlefish possession and harvest in all Alabama waters went into effect in November 1988. We report on recent paddlefish sampling efforts in Alabama reservoirs of the Tennessee River to evaluate if paddlefish stocks have recovered to the point that sustainable commercial harvest is feasible. We used gill nets with various configurations and expended a total of 3125.4 h of gillnetting effort from all four reservoirs combined from October 2016 to January 2021. We captured 17 paddlefish conferring an overall CPUE of 0.005 fish h–1. Standardizing gill-net effort across configurations resulted in CPUEs ranging from 0.00 to 0.05 fish m–2 per 24-hr soak time. Biological data obtained from 10 of the 17 paddlefish collected during gillnetting indicated these 10 fish were sexually mature with ages ranging from 8 to 16 years. Only two female paddlefish were harvested during an experimental commercial paddlefish season from Guntersville Reservoir in 2017. Due to extremely low CPUEs, results of this study indicate Tennessee River paddlefish stocks in Alabama would not support a sustainable commercial fishery at this time. We recommend continuation of the paddlefish moratorium and monitoring of the population using a standardized design based on gear and effort. We further recommend consulting with adjoining state resource agencies to seek a moratorium on commercial paddlefish harvest in shared waters of Guntersville Reservoir in the Tennessee River.
2022 JSAFWA 1
Feasibility of a Commercial Paddlesh Fishery . Rider et al.
Feasibility of Initiating a Commercial Fishery for Paddlesh in Alabama Reservoirs
of the Tennessee River
Steven J. Rider
, Alabama Division of Wildlife and Freshwater Fisheries, 3608 Fairground Road, Montgomery, AL 36110
J. Eric Ganus, Tenne s s e e Wildlife Resources Agency, 5107 Edmonson Pike, Nashville, TN 37211
Travis R. Powell, Alabama Division of Wildlife and Freshwater Fisheries, 3608 Fairground Road, Montgomery, AL 36110
Gregory T. Miles, Alabama Division of Wildlife and Freshwater Fisheries, 3608 Fairground Road, Montgomery, AL 36110
Abstract: In recent years, commercial paddlesh harvesters have renewed their requests for opening a potential commercial paddlesh (Polyodon
spathula) season in Alabama reservoirs of the Tennessee River, including part of Pickwick Reservoir, all of Wilson and Wheeler reservoirs, and the
majority of Guntersville Reservoir. ese reservoirs of the Tennessee River once supported robust stocks of paddlesh; however, beginning in the 1940s
overexploitation became evident as the number of paddlesh harvested declined. Because of this widespread overharvest, a commercial and recreation-
al moratorium on paddlesh possession and harvest in all Alabama waters went into eect in November 1988. We report on recent paddlesh sampling
eorts in Alabama reservoirs of the Tennessee River to evaluate if paddlesh stocks have recovered to the point that sustainable commercial harvest
is feasible. We used gill nets with various congurations and expended a total of 3125.4 h of gillnetting eort from all four reservoirs combined from
October 2016 to January 2021. We captured 17 paddlesh conferring an overall CPUE of 0.005 sh h–. Standardizing gill-net eort across congura-
tions resulted in CPUEs ranging from 0.00 to 0.05 sh m– per 24-hr soak time. Biological data obtained from 10 of the 17 paddlesh collected during
gillnetting indicated these 10 sh were sexually mature with ages ranging from 8 to 16 years. Only two female paddlesh were harvested during an
experimental commercial paddlesh season from Guntersville Reservoir in 2017. Due to extremely low CPUEs, results of this study indicate Tennessee
River paddlesh stocks in Alabama would not support a sustainable commercial shery at this time. We recommend continuation of the paddlesh
moratorium and monitoring of the population using a standardized design based on gear and eort. We further recommend consulting with adjoining
state resource agencies to seek a moratorium on commercial paddlesh harvest in shared waters of Guntersville Reservoir in the Tennessee River.
Key words: commercial harvest, CPUE, age structure, moratorium
Journal of the Southeastern Association of Fish and Wildlife Agencies 9: 1–7
Paddlesh (Polyodon spathula) are found in the Tennessee Riv-
er and Mobile River basins of Alabama (Boschung and Mayden
2004, Mettee et al. 2009). e Tennessee River basin encompasses
an area of 105,905 km, including parts of Virginia, North Caroli-
na, Tennessee, Georgia, Alabama, and Mississippi; the river nally
discharges into the Ohio River in Kentucky. e Mobile River basin
is the largest drainage on the Gulf Coast east of the Mississippi Riv-
er and encompasses 113,900 km in Georgia, Tennessee, Alabama,
and Mississippi. Six major river systems compose the basin, in-
cluding the Black Warrior, Tombigbee, Alabama, Cahaba, Coosa,
and Tallapoosa rivers, joining to ow into Mobile Bay and the Gulf
of Mexico. Historically, rivers in the Tennessee and Mobile River
basins sustained abundant paddlesh populations that supported
recreational and commercial sheries (Gengerke 1986). Nonethe-
less, the legacy of commercial paddlesh harvest in Alabama has
been one of overexploitation with limited to no regulations (Rider
et al. 2019). Overexploitation of paddlesh was evident in the Ten-
nessee River by the early 1940s, as harvest with snag lines declined
84% from 323,865 kg in 1941 to 52,011 kg in 1946 (Pasch and
Alexander 1986). Despite this drastic decline in abundance, the
Alabama legislature legalized the use of nets in 1946 to encourage
increased harvest of paddlesh as demand surged for meat and roe
aer World War II (Pasch and Alexander 1986). Accordingly, pad-
dlesh harvest increased in 1947 to 68,745 kg but by 1954 had de-
clined to 53,751 kg. Increasing roe prices in the late 1970s resulted
in paddlesh harvest peaking at approximately 150,000 kg in 1980
(Gengerke 1986). rough the 1980s, Tennessee River paddlesh
stocks farther north in Kentucky and Tennessee also declined due
to overshing, and commercial harvesters then redirected their
eorts to Alabama, increasing additional pressure on already de-
pleted stocks (Rider et al. 2019). e additional shing eort re-
sulted in a severe decline in paddlesh abundance and sizes; there-
fore, the Alabama Division of Wildlife and Freshwater Fisheries
(ADWFF) placed a recreational and commercial moratorium on
1. E-mail: Steve.Rider@dcnr.alabama.gov
Rider et al. 2
2022 JSAFWA
the capture, possession, and harvest of paddlesh in Alabama wa-
ters beginning November 1988 (Rider et al. 2012).
By early 1993, ADWFF managers sought a current population
assessment to determine if paddlesh stocks had recovered in Al-
abama reservoirs of the Tennessee River since the moratorium.
From November 1993 to June 1994, a total of 346 gillnetting and
20 electroshing h of eort failed to capture a single paddlesh in
this area (Hoxmeier and DeVries 1996). However, these sampling
eorts were not extensive. Additional paddlesh sampling was
conducted from February to March 2012 in Guntersville Reser-
voir in consultation with a commercial harvester who had targeted
paddlesh before the moratorium. No paddlesh were collected
with 72 h of sampling eort; however, the ow was high which
made sampling dicult (S. Rider, ADWFF, unpublished data).
By the early 2000s, studies in the Mobile River basin indicated
paddlesh abundance in the Alabama River had increased since
the moratorium (Rider 2006, Mettee et al. 2009). By 2012, sam-
pling revealed this stock had a robust population with older age
classes along with many prime spawning sh present (Scarnecchia
et al. 2007, Rider et al. 2012). erefore, the ADWFF proposed a
“provisional” shery using a proactive approach (Rider et al. 2019)
and informed commercial harvesters this approach would allow
ADWFF to evaluate the shery for future seasons. A commercial
paddlesh season opened in 2013, but the season was suspended
indenitely in 2018 due to numerous and agrant violations by
commercial paddlesh harvesters (ADWFF 2018).
Despite the indenite closure of commercial paddlesh harvest
in the Alabama River, commercial paddlesh harvesters have con-
tinued to voice their support for a commercial paddlesh season
in Alabama reservoirs of the Tennessee River, claiming that pad-
dlesh stocks have recovered to the point such a shery is war-
ranted. In addition, the Tennessee Wildlife and Resources Agency
(TWRA) allows commercial paddlesh harvest below Nickajack
Lock and Dam, at the headwaters of Guntersville Reservoir. is
shery exists only 14.5 km above where the Tennessee River cross-
es into Alabama. is limited commercial shery just upstream of
Alabama waters bolstered the commercial paddlesh harvesters’
convictions that a commercial shery downstream in Alabama
is warranted. erefore, our objective was to determine whether
paddlesh relative abundance (CPUE) was sucient to allow com-
mercial harvest in Alabama reservoirs of the Tennessee River.
Study Area
Paddlesh sampling was conducted in Alabama waters of the
Tennessee River in Guntersville, Wheeler, Wilson, and Pickwick
reservoirs (Figure 1). Guntersville Reservoir has a surface area of
27,478 ha and stretches over 135.2 km from Nickajack Dam in
southeastern Tennessee to Guntersville Dam. Wheeler Reservoir
begins immediately below Guntersville Dam and ows north-
west for 119.3 km, encompassing 27,142 ha. Wilson Reservoir is
the smallest of the four reservoirs (6,273 ha), beginning below
Wheeler Dam and owing west for 24.9 km. Pickwick Reservoir
begins immediately below Wilson Dam and ows in a southwest-
ern to northwestern direction for 84.3 km, encompassing 17,442
ha. Pickwick Reservoir is a multi-jurisdictional reservoir shared
by Mississippi and Tennessee, with most of Guntersville, and all of
Wheeler and Wilson entirely in Alabama. Collectively, these four
reservoirs have a total surface area of 78,335 ha and encompass
350.4 km of the Tennessee River.
Methods
Paddlesh sampling was conducted using gill nets of various
congurations, materials, mesh sizes, depths, and lengths in the
four reservoirs at varying times from 2016 to 2021. Mono-twist gill
nets were 61 m long, 4.9 or 5.5 m deep with 152-mm mesh. Mono-
lament untied gill nets (i.e., non-hobbled) ranged in lengths of
46, 61, and 91 m, depths of 1.8, 2.4, 3.0, 3.6, 4.3, and 5.5 m, with
square (bar measure) meshes sizes of 25, 38, 52, 64, 76, 89, 102,
127, and 152 mm. We also deployed tied-down (i.e., hobbled) gill
nets. ese nets run a string every 1.8 m along length of the gill
net that is attached from the oat line to the lead line to reduce
the depth of the net. is results in a bag of webbing being formed
at the bottom of the net where paddlesh are entangled. Gill nets
of this conguration capture more sh from entanglement rather
than being wedged in the mesh (Hamley 1980). e use of tied-
down gill nets is common with commercial paddlesh harvesters
Figure 1. Map of the ve mainstem reservoirs that consist of Alabama waters of the Tennessee River
where sampling for paddlesh was conducted from October 2016 to January 2021.
Rider et al. 3
2022 JSAFWA
where legal (Honagle and Timmons 1989, Scholten and Bettoli
2007, Geik 2016; Risley et al. 2016). Our monolament tied-down
gill nets were 91 m long and either 3.6 m deep tied-down to 3.0 m
or 7.3 m deep tied-down to 5.5 m with square mesh sizes of 76,
102, 127, and 152 mm. Multilament untied gill nets ranged in
lengths of 46 and 61 m with a depth of 3 m and square mesh sizes
of 127, 152, and 203 mm; whereas tied-down multilament gill
nets were 61 m long, 3.7 m deep, and tied-up to 1.8 m with square
mesh sizes of 76, 102, 127, and 152 mm. Gill nets were either sink-
ing or oating style with oating nets set below the water surface
approximately 1 m to prevent passing boats from becoming entan-
gled. Sinking gill nets were set on the bottom of the water body or
in the mid-water column. We deployed gill nets in the aernoon
to early evening and pulled the following morning with set times
ranging from 15 to 21 h. Sample locations were determined using
commercial harvester input based on historical catches and more
recent bycatches of paddlesh.
e number of hours to collect paddlesh was an important
statistic requested by ADWFF biologists and administrators.
erefore, CPUE was calculated across all net congurations as
paddlesh h– of gill-net eort and was reported to the nearest
0.001 to emphasize the amount of time needed to catch paddlesh.
We realized this value may not reect an accurate CPUE as gill
nets deployed were of dierent congurations as described above
and were shed for various soak times. erefore, we also provid-
ed standardized CPUE calculated as paddlesh 100 m– of gill net
per 24-h soak time by mesh size (Paukert and Fisher 1999). Eort
did not meet the assumption of normality; therefore, we exam-
ined dierences in paddlesh hourly CPUE among reservoir and
collection date, reservoir combined by collection dates, and stan-
dardized CPUE by gill net meshes using a Kruskal-Wallis one-way
ANOVA on ranks. All statistical analyses were conducted using
the statistical soware package SigmaStat 3.5 (Systat Soware Inc.,
San Jose, California) with signicance determined using P ≤ 0.05.
Biological data were obtained from all paddlesh collected in
Guntersville Reservoir and one paddlesh in Wheeler Reservoir.
We did not obtain any biological data from the remaining three
and four paddlesh collected from Wheeler and Pickwick reser-
voirs, respectively, because these sh were released aer capture as
the crews did not have the space required to keep them. Paddlesh
were measured from anterior orbit of the eye along curvature of
the body to the fork of the caudal n (curved eye-to-fork; CEFL)
to the nearest mm (Rider et al. 2019). Total sh weights were mea-
sured to the nearest 0.2 kg. Gonads were excised, separated from
the gonadal fat, and weighed to the nearest 0.1 g; sex was deter-
mined visually from the excised gonads (Scarnecchia et al. 2007).
We used the gonadosomatic index (GSI) which was calculated for
each individual with the following equation: GSI = 100 x gonad
weight (g)/body weight (g) and reproductive staging guides to as-
sign reproductive maturity (Crim and Glebe 1990, Scarnecchia et
al. 2007, Webb et al. 2019). To determine age, the le lower dentary
bone was excised, processed, and sectioned as described in Scar-
necchia et al. (1996) and ages assigned by counting annuli (Scar-
necchia et al. 2006).
In 2017, the ADWFF initiated a seven-week experimental com-
mercial paddlesh harvest season in the upper reaches of Gunters-
ville Reservoir to provide current commercial catch data (ADWFF
2017). Commercial paddlesh harvest numbers and statistics were
obtained from the Alabama Daily Commercial Paddlesh Har-
vester and Dealer’s Report (Rider et al. 2019). Commercial paddle-
sh harvesters were required by regulation to submit these reports
on a weekly basis (ADWFF 2017). For each harvested female, the
CEFL, total sh weight, total egg weight, and total screened egg
weight were required. e harvesters also provide their start and
ending shing times and number of gill nets shed each day. In ad-
dition to the data provided by commercial paddlesh harvesters,
sheries biologists with the River and Stream Fisheries Program of
ADWFF obtained paddlesh harvest data via check stations. In-
dependent biological data from harvested female paddlesh were
obtained to verify biological data provided by commercial paddle-
sh harvesters.
Because commercial paddlesh harvest remained open and
legal in the upper reaches of Guntersville Reservoir in Tennes-
see during this study, we obtained commercial paddlesh harvest
numbers by sex and total egg weights (kg) from below Nickajack
Dam in Tennessee from TWRA commercial sh reports (Ganus
2016, 2017, 2018, 2020, 2021). Harvest numbers from 2011 to
2015 were obtained from TWRA’s commercial harvest database
(J. E. Ganus, TWRA, unpublished data). Reporting commercial
paddlesh harvest data was mandated by the State of Tennes-
see (Rule 1660-1-30) with roe-harvest data collected using Daily
Commercial Roe Fish Harvest Reports (WR-0896). e number
of female paddlesh harvested met the assumption of normality;
therefore, we examined the dierence in the number of paddle-
sh harvested from 2010–2015 compared to 2016–2021 using a
two-sample t-test with the statistical package SigmaStat 3.5. Signif-
icance was determined using P ≤ 0.05.
Results
We collected 17 paddlesh from the four study reservoirs aer
expending 3125.4 h of gillnetting eort (Table 1). Overall mean
(SD) CPUE was 0.005 (0.006) sh h– which translates to 200 h
of gillnetting eort required to catch one paddlesh. Nine of the
17 paddlesh were collected from Guntersville Reservoir with
Rider et al. 4
2022 JSAFWA
CPUEs ranging from 0.000 to 0.017 sh h– with a mean of 0.008
(0.008) sh h–. Four paddlesh were caught in each of Wheeler
and Pickwick reservoirs, with CPUEs ranging from 0.000 to 0.019
sh h– across reservoirs; mean CPUE was 0.003 (0.006) sh h– at
Wheeler Reservoir and 0.005 (0.009) sh h– from Wheeler and
Pickwick reservoirs, respectively. We did not collect any paddle-
sh from Wilson Reservoir. Paddlesh CPUE was similar across
reservoirs and sample dates (H = 17.9, df = 15, P = 0.264) or among
reservoirs when combined by collection date (H = 1.76, df = 3,
P = 0.624).
Standardized CPUEs ranged from 0 to 0.05 paddlesh m– of
gill net per 24-h soak time (Table 2) and was similar among the
various mesh sizes used (H = 2.47, df = 5, P = 0.78). Similar with the
hourly CPUE, the standard CPUE indicated it would take exces-
sive eort to collect one paddlesh. For example, using a 91.4-m x
7.3-m gill net it would take 160 h of eort to collect one paddlesh.
For female paddlesh (n = 4) CEFL and total weights ranged
from 1147 to 1234 mm, and 25.2 to 34.4 kg, respectively (Table 3).
All females were age 13 or 14 and were sexually mature individuals
based on GSIs and visual inspection of the ovaries. Male paddle-
sh (n = 6) CEFL and total weights ranged from 847 to 1177 mm,
and 12.5 to 24.0 kg, respectively. Ages ranged from 8 to 15 years
and these males were classied as sexually mature based on visual
inspection of the gonads (Table 3).
e 2017 Alabama experimental commercial paddlesh season
in Guntersville Reservoir only yielded 2 harvestable female pad-
dlesh, generating a CPUE of 0.02 sh h– (Table 3). Commercial
harvesters caught more paddlesh (males or undersized females)
but did not record accurately the total number as required by reg-
ulation and only shed 2 of 7 weeks that were open for commer-
cial paddlesh shing due to high water. e TWRA commercial
harvest data documented 117 female paddlesh harvested below
Table 1. Total number of gill-net sets, eort (gill net-h), number of paddlesh collected, median
and mean CPUE (sh h–1) by reservoir and date from Alabama reservoirs of Tennessee River.
Reservoir Date Gill nets Eort nMedian Mean
Guntersville Oct 2016 14 171.7 3 0.0 0.017
Guntersville Nov 2016 28 504.0 1 0.0 0.002
Guntersville Jun 2017 20 448.4 5 0.0 0.011
Guntersville Jul 2017 19 436.1 0 0.0 0.000
Wheeler Feb 2017 3 54.0 0 0.0 0.000
Wheeler Nov 2017 10 174.2 1 0.0 0.006
Pickwick Nov 2017 11 185.0 0 0.0 0.000
Wheeler Mar 2018 3 54.0 0 0.0 0.000
Pickwick May 2020 18 216.0 4 0.0 0.019
Wheeler Jun 2020 18 216.0 3 0.0 0.014
Wilson Jul 2020 8 96.0 0 0.0 0.000
Pickwick Oct 2020 12 144.0 0 0.0 0.000
Wilson Oct 2020 8 96.0 0 0.0 0.000
Wheeler Oct 2020 12 144.0 0 0.0 0.000
Pickwick Nov 2020 8 96.0 0 0.0 0.000
Wheeler Jan 2021 3 90.0 0 0.0 0.000
Total 195 3125.4 17 0.0 0.005
Table 2. Total number of gill nets, number of paddlesh collected, median and mean paddlesh
CPUE by mesh size from Alabama reservoirs of the Tennessee River, 2016 to 2021. CPUE is reported
as paddlesh 100 m–2 of gill net per 24 h soak time. Mesh size (mm) for paddlesh collected in
experimental gill nets (i.e., 76-102-127) was not recorded; therefore, CPUE was calculated per
experimental gill net.
Mesh size (mm) Gill nets nMedian Mean
89 7 0 0.0 0.00
102 7 0 0.0 0.00
127 10 0 0.0 0.00
152 80 9 0.0 0.02
203 7 0 0.0 0.00
76-102-127 84 8 0.0 0.05
Total 195 17 0.0 0.03
Table 3. Biological data for paddlesh collected by ADWFF biologists or commercial paddlesh harvesters (CPH) from the Alabama reservoirs of the Tennessee River, 2016 to 2017. CEFL is the curved-eye-to-
fork length, and GSI is the gonadosomatic index.
Collector Date collected CEFL (mm) Sex Maturity/ Reproductive condition Total weight (kg) Gonad weight (g) GSI Age
ADWFF 2 Nov 2016 1125 M Mature/ Pre-spawn 23.8 371.0 1.6 15
ADWFF 2 Nov 2016 1234 F Mature/ Gravid 34.4 6370.0 18.5 13
ADWFF 2 Nov 2016 1148 F Mature/ Gravid 25.8 3970.0 15.4 13
ADWFF 3 Nov 2016 1114 M Mature/ Pre-spawn 23.4 544.3 2.3 13
ADWFF 19 Jun 2017 1147 F Mature/ Post-spawn 25.2 888.3 3.5 13
ADWFF 19 Jun 2017 1118 M Mature/ Post-spawn 24.0 79.4 0.3 14
ADWFF 19 Jun 2017 1185 F Mature/ Post-spawn 27.4 982.0 3.6 14
ADWFF 19 Jun 2017 965 M Mature/ Post-spawn 16.9 61.7 0.4 9
ALDWFF 19 Jun 2017 847 M Mature/ Post-spawn 12.5 42.6 0.3 8
ADWFF 29 Nov 2017 1177 M Mature/ Pre-spawn 30.2 330.0 1.1 16
CPH 9 Mar 2017 1130 F Mature/ Gravid 26.3 4.8 18.3 15
CPH 7 Mar 2017 1213 F Mature/ Gravid 29.5 4.5 15.3 n/a
Rider et al. 5
2022 JSAFWA
Nickajack Dam from 2010 to 2015, with catches ranging from 26
to 47 per year. However, the number of female paddlesh harvest-
ed from 2016 to 2020 in this area ranged from 4 to 16. On average
more female paddlesh were harvested the rst ve years (x¯ = 35,
SD = 8) compared to the last ve years (x¯ = 8, SD = 5) (t = 6.5, df = 8,
P < 0.001; Table 4).
Discussion
Our results indicate paddlesh populations in the Alabama res-
ervoirs of the Tennessee River are still recovering from past de-
pletion and thus vulnerable to overshing. For example, CPUEs
from paddlesh surveys conducted in the Alabama River (Mobile
River basin) from 2005 to 2008 ranged from 0.1 to 2.3 sh h– with
a mean (SD) of 0.70 (0.67) sh h– before commercial harvest was
allowed (Rider 2012). is is a dierence in orders of magnitude
compared to our results from the Tennessee River. On average it
took 1.4 h to catch a paddlesh in the Alabama River; whereas
with our sampling in the Tennessee River it took 200 h to catch
a paddlesh. Likewise, in the lower Tombigbee River, Alabama,
which has been closed to commercial harvest since the 1988 mor-
atorium, gill net CPUEs from 2012 to 2014 ranged from 0 to 14.6
sh h– with a mean (SD) of 1.15 (3.22) sh h– (S. Rider, ADWFF,
unpublished data). In that system, a total of 0.87 h of eort was
required on average to catch one paddlesh. In contrast to the
Tennessee River, both the lower Tombigbee and Alabama rivers
demonstrated sucient relative abundance to justify a commer-
cial season, which was initiated in the Alabama River beginning
in 2013. However, no such justication was found in the Alabama
reservoirs of the Tennessee River, even though legal commercial
paddlesh shing has not been conducted since 1988.
Commercial paddlesh harvest and catch data reected compa-
rable results as our shery surveys. Hoxmeier and DeVries (1997)
conducted the only other paddlesh survey in Alabama reservoirs
of the Tennessee River, which occurred just ve to six years aer the
moratorium went into eect. ey failed to collect any paddlesh,
although their sampling eort (366 h) was low compared to our
sampling eort. However, their results indicated how heavily the
paddlesh population was exploited prior to 1988. Likewise, the
CPUE recorded for the 2017 experimental commercial paddlesh
season in Guntersville was an order of magnitude less than what
was observed in the Alabama River, where the mean (SD) CPUE
for commercial harvesters from 2013 to 2017 was 0.14 (0.03) sh
h– (S. Rider, ADWFF, unpublished data). erefore, 30 years aer
the paddlesh moratorium was authorized in Alabama, the Ten-
nessee River populations there had shown little signs of recovery.
Although a commercial shery still exists on the Tennessee
River upstream of Alabama below Nickajack Dam, the number
of paddlesh harvested has also decreased over the last decade.
A total of 215 female paddlesh were harvested over 2010–2020
(J. E. Ganus, TWRA, unpublished data; Ganus 2016, 2017, 2018,
2020, and 2021), but most (82.3%) of them were harvested from
2011–2015 and paddlesh harvest decreased 5-fold from 2010–
2015 compared to 2015–2020. e commercial paddlesh season
in the upper reaches of Guntersville Reservoir of Tennessee may
in fact be limiting or suppressing the Reservoir’s paddlesh pop-
ulation. Paddlesh are highly migratory and oen congregate be-
low dams and other barriers where they become more vulnerable
to overshing (Tripp et al. 2019). e recent decline in paddlesh
harvest numbers during 2015–2020 and low relative abundance
found in our survey indicate that recruitment overshing may be
occurring in this population. us, both Tennessee and Alabama
data indicate that paddlesh populations in this section of the Ten-
nessee River have not rebounded and may in fact have declined.
We expended a large amount of eort targeting paddlesh in the
Alabama reservoirs of the Tennessee River in this study; however,
these reservoirs are large, and this eort may still be low relative to
their surface area. us, increased sampling/monitoring eorts are
needed in these reservoirs.
Downstream of our study area in Kentucky Lake, ages of pad-
dlesh in an exploited population ranged from 2 to 16 years old
(Hageman et al. 1986, Honagle and Timmons 1989). However, by
2004 the shery was overshed with no ages over 11 years (Schol-
ten and Bettoli 2005). Hoxmeier and DeVries (1997) examined
age structure of the Alabama River population just ve to six years
aer implementation of the statewide harvest moratorium and
found that 92% of these sh were age 7 or younger. Similar trun-
cated age structures were found in exploited Louisiana paddlesh
populations (Reed et al. 1992). Due to their longevity and late age
at maturation, paddlesh populations recovery from overshing
Table 4. Number of paddlesh harvested by commercial harvesters below Nickajack Dam at the
headwaters of Guntersville Reservoir, Tennessee River, Tennessee, 2011 to 2021.
Harvest season Females Males Total Total egg weight (kg)
2010–2011 29 9 38 44.90
2011–2012 36 1 37 64.70
2012–2013 47 5 52 95.10
2013–2014 39 6 45 89.60
2014–2015 26 4 30 66.80
2015–2016 16 0 16 48.50
2016–2017 5 20 25 20.40
2017–2018 7 0 7 25.80
2018–2019 6 0 6 12.70
2019–2020 4 0 4 13.10
Total 215 45 260 481.6
Rider et al. 6
2022 JSAFWA
oen occurs over decadal time scales and truncated age structures
are indicative of heavily exploited populations (Carlson and Bon-
islawsky 1981, Graham 1997). Conversely, unexploited, or light-
ly exploited paddlesh populations routinely have sh exceeding
20 years in age (Scarnecchia et al. 1996 for the Yellowstone River,
Montana/North Dakota; Runstrom et al. 2001 for the Wisconsin
River, Wisconsin; and S. Rider, ADWFF, unpublished data for the
Tombigbee River, Alabama). However, despite no harvest being
allowed in the Alabama reservoirs of the Tennessee River since
1988, the oldest sh collected during this study was 16 years old
(i.e., 2001-year class). us, although recruitment is occurring, it
seems to be at a lower rate in Alabama reservoirs of the Tennessee
River compared to other Alabama river systems. Lower recruit-
ment could be associated with insucient discharge rates during
the spawning period and/or associated physical habitat (Schlosser
1982, Po and Allan 1995, Ward et al. 1999, Nilsson and Svedmark
2002).
Movement from closed and/or protected areas (i.e., Alabama
reservoirs of the Tennessee River) for mobile species like paddle-
sh has been documented for marine and freshwater shes (Hayes
et al. 1997, Apostolaki et al. 2002, Kerwath et al. 2009, Knip et al.
2012). Our data suggests that low paddlesh abundances in the
Tennessee River may reect sh moving upriver or downriver out
of Alabama water where harvest is closed into areas where they
could be exploited. However, the large lock and dams found in
the Tennessee River constitute substantial barriers to movement.
Paddlesh have been documented moving upriver and downriver
of low-head dams when inundated; however, movement through
these larger dams and locks is substantially less (Moen et al 1992,
Zigler et al 2003, Mettee et al. 2009). Also, if this did occur then
paddlesh from other reservoirs where exploitable populations
exist would also be moving into the closed areas in Alabama. At
this time, we cannot determine whether this is occurring, but we
believe it is unlikely. erefore, synchronous regulations are par-
amount for management and conservation of paddlesh popu-
lations in waters shared between states, and we recommend the
TWRA and ADWFF seek a joint paddlesh harvest moratorium
in Guntersville Reservoir to the headwaters below Nickajack Dam
in Tennessee.
e low relative abundance and young ages of this unexploited
paddlesh population indicate it is still recovering and recruit-
ment is low compared to other populations in Alabama aer the
moratorium. e causes of low recruitment are uncertain at this
time and additional research is warranted to determine what abi-
otic and biotic factors are aecting recruitment. Potential causes
and/or bottlenecks may be changes to reservoir operations, loss of
habitat, illegal harvesting, and continued commercial harvest of
paddlesh in shared waters of the Tennessee River. Nonetheless,
Alabama reservoirs of the Tennessee River paddlesh stocks have
not recovered to date to allow for sustainable commercial harvest.
We propose the following management recommendations to
accurately describe the characteristics of the paddlesh popula-
tions in the Alabama reservoirs of the Tennessee River.
1) Develop annual stratied-random sampling protocols to en-
sure all habitats and areas of the reservoir are represented with the
appropriate amount of eort.
2) Sample annually during the winter (December–February)
and spring (March–May).
3) Use standardized gear congurations for adult and juvenile
sampling.
4) Use standardized sampling eort.
5) Implant telemetry tags in paddlesh to discern if movement
into and out of these Alabama reservoirs is occurring.
Acknowledgments
e authors thank Keith Floyd and Phil Ekema of the Alabama
Division of Wildlife and Freshwater Fisheries for providing addi-
tional gill net data from Alabama waters of the Tennessee River
and several anonymous reviewers whose comments and sugges-
tions improved this manuscript.
Literature Cited
Alabama Division of Wildlife and Freshwater Fisheries (ADWFF). 2017. Ala-
bama Administrative Code Regulation 220-2-.158 Guntersville Reservoir
paddlesh management area and season established. Montgomery, Ala-
bama.
_____. 2018. Alabama River commercial paddlesh seasons suspended in-
denitely. Montgomery, Alabama. <https://www.outdooralabama.com/
node/2391>. Accessed 15 July 2021.
Apostolaki, P., E. J. Milner-Gulland, M. K. McAllister, and G. P. Kirkwood.
2002. Modelling the eects of establishing a marine reserve for mobile
sh species. Canadian Journal of Fisheries and Aquatic Sciences 59:405–
415.
Boschung, H. T. and R. L. Mayden. 2004. Fishes of Alabama. Smithsonian
Books, Washington, D. C.
Carlson, D. M. and P. S. Bonislawsky. 1981. e paddlesh (Polyodon spathula)
sheries of the midwestern United States. Fisheries 6:17–27.
Crim, L. W. and B. D. Glebe. 1990. Reproduction. Pages 529–533 in C. B. Schreck
and P. B. Moyle, editors. Methods for sh biology. American Fisheries So-
ciety, Bethesda, Maryland.
Ganus, E. 2016. Tennessee’s commercial sh and mussel report. Report no.
16-12. Tennessee Wildlife Resources Agency, Fisheries Management Di-
vision, Nashville, Tennessee.
_____. 2017. Tennessee’s commercial sh and mussel report. Report no. 17-09.
Tennessee Wildlife Resources Agency, Fisheries Management Division,
Nashville, Tennessee.
_____. 2018. Tennessee’s commercial sh and mussel report. Report no. 18-07.
Tennessee Wildlife Resources Agency, Fisheries Management Division,
Nashville, Tennessee.
_____. 2020. Tennessee’s commercial sh and mussel report. Report no. 20-02.
Rider et al. 7
2022 JSAFWA
Tennessee Wildlife Resources Agency, Fisheries Management Division,
Nashville, Tennessee.
_____. 2021. Tennessee’s commercial sh and mussel report. Report no. 21-03.
Tennessee Wildlife Resources Agency, Fisheries Management Division,
Nashville, Tennessee.
Geik, A. 2016. Movement, habitat use, reproduction, and commercial harvest
of paddlesh in Lake Dardanelle, Arkansas. Master’s esis, Arkansas
Tech University, Jonesboro.
Gengerke, T. W. 1986. Distribution and abundance of paddlesh in the Unit-
ed States. Pages 22–35 in J. G. Dillard, L. K. Graham, and T. R. Russell,
editors. e paddlesh: status, management, and propagation. Special
Publication No. 7. American Fisheries Society, North Central Division,
Bethesda, Maryland.
Graham, K. 1997. Contemporary status of the North American paddlesh,
Polyodon spathula. Environmental Biology of Fishes 48:279–289.
Hageman, J. R., D. C. Timpe, and R. D. Hoyt. 1986. e biology of paddlesh
in Lake Cumberland, Kentucky. Proceedings of the Annual Conference of
the Southeastern Association of Fish and Wildlife Agencies 40:237–248.
Hamley, J. M. 1980. Sampling with gill nets. Pages 3753 in T. Backiel and
R. L. Welcomme, editors. Guidelines for sampling sh in inland waters.
Advisory Commission Technical Paper 33. FAO European Inland Fish-
eries, Rome, Italy.
Hayes, M. C., L. F. Gates, and S. A. Hirsch. 1997. Multiple catches of small-
mouth bass in a special regulation shery. North American Journal of
Fisheries Management 17:182–187.
Honagle, T. L. and T. J. Timmons. 1989. Age, growth, and catch analysis of
the commercially exploited paddlesh population in Kentucky Lake,
Kentucky-Tennessee. North American Journal of Fisheries Manage-
ment 9:316–326.
Hoxmeier, R. J. and D. R. Devries. 1996. Status of paddlesh in the Alabama
waters of the Tennessee River. North American Journal of Fisheries Man-
agement 16:935–938.
Kerwath, S. E., E. B. orstad, T. F. Næsje, P. D. Cowley, F. Økland, C. Wilke,
and C. G. Attwood. 2009. Crossing invisible boundaries: the eectiveness
of the Langebaan Lagoon Marine Protected Area as a harvest refuge for a
migratory sh species in South Africa. Conservation Biology 23:653–661.
Knip, D. M., M. R. Heupel, and C. A. Simpfendorfer. 2012. Evaluating marine
protected areas for the conservation of tropical coastal sharks. Biological
Conservation 148:200–209.
Mettee, M. F., P. E. O’Neil, and S. J. Rider. 2009. Paddlesh movements in the
lower Mobile River basin, Alabama. Pages 63–81 in C. P. Paukert and G. D.
Scholten, editors. Paddlesh management, propagation, and conservation
in the 21st century. American Fisheries Society, Bethesda, Maryland.
Moen, C. T., D. L. Scarnecchia, and J. S. Ramsey. 1992. Paddlesh movements
and habitat use in Pool 13 of the upper Mississippi River during abnor-
mally low river stages and discharges. North American Journal of Fisher-
ies Management 12:744–751.
Nilsson, C. and M. Svedmark. 2002. Basic principles and ecological conse-
quences of changing water regimes: riparian plant communities. Envi-
ronmental Management 30:468–480.
Pasch, R. W. and C. M. Alexander. 1986. Eects of commercial shing on
paddlesh populations. Pages 46–53 in J. G. Dillard, L. K. Graham, and
T. R. Russell, editors. e paddlesh: status, management, and propaga-
tion. Special Publication No. 7. American Fisheries Society, North Cen-
tral Division, Bethesda, Maryland.
Paukert, C. P. and W. L. Fisher. 1999. Evaluation of paddlesh length distri-
butions and catch rates in three mesh sizes of gill nets. North American
Journal of Fisheries Management 19:599603.
Po, N. L. and J. D. Allan. 1995. Functional organization of stream sh assem-
blages in relation to hydrological variability. Ecology 76:606–627.
Reed, B. C., W. E. Kelso, and D. A. Rutherford 1992. Growth, fecundity, and
mortality of paddlesh in Louisiana. Transactions of the American Fish-
eries Society 121:378384.
Rider, S. J. 2006. Population status of paddlesh (Polyodon spathula) in the Al-
abama River. Interim project report, 2005. Alabama Division of Wildlife
and Freshwater Fisheries, River and Stream Fisheries Program, Mont-
gomery, Alabama.
_____, T. R. Powell, and T. W. Ringenberg. 2012. Assessment of an unexploit-
ed paddlesh population in the Alabama River. Report ARP-1104. Al-
abama Division of Wildlife and Freshwater Fisheries, River and Stream
Fisheries Program, Montgomery, Alabama.
_____, D. K. Riecke, and D. L. Scarnecchia. 2019. Proactive harvest manage-
ment of commercial paddlesh sheries. Pages 267297 in J. D. Schooley
and D. L. Scarnecchia, editors. Paddlesh: ecological, aquacultural, and
regulatory challenges of managing a global resource. American Fisheries
Society, Bethesda, Maryland.
Risley, J. T., R. L. Johnson, and J. W. Quinn. 2016. Evaluation of the com-
mercially exploited paddlesh shery in the lower Mississippi River of
Arkansas. Journal of the Southeastern Association of Fish and Wildlife
Agencies 4:5259.
Runstrom, A. L., B. Vondracek, and C. A. Jennings. 2001. Population statis-
tics for paddlesh in the Wisconsin River. Transactions of the American
Fisheries Society 130:546556.
Scarnecchia, D. L., L. F. Ryckman, Y. Lim, G. J. Power, B. J. Schmitz, and J. A.
Firehammer. 2007. Life history and the costs of reproduction in northern
Great Plains paddlesh (Polyodon spathula) as a potential framework for
other Acipenseriform shes. Reviews in Fisheries Science 15:211–263.
_____, _____, _____, _____, _____, and V. Riggs. 2006. A long-term pro-
gram for validation and verication of dentaries for age estimation in the
Yellowstone-Sakakawea paddlesh stock. Transactions of the American
Fisheries Society 135:1086–1094.
_____, P. A. Stewart, and G. J. Power. 1996. Age structure of the Yellowstone–
Sakakawea paddlesh stock, 1963–1993, in relation to reservoir histo-
ry. Transactions of the American Fisheries Society 125:291–299.
Schlosser, I. J. 1982. Fish community structure and function along two habitat
gradients in a headwater stream. Ecological Monographs 52:395–414.
Scholten, G. D. and P. W. Bettoli. 2005. Population characteristics and assess-
ment of overshing for an exploited paddlesh population in the lower
Tennessee River. Transactions of the American Fisheries Society 134:1285–
1298.
_____ and _____. 2007. Lack of size selectivity for paddlesh captured in
hobbled gillnets. Fisheries Research 83:355–359.
Tripp, S. J., B. C. Neely, and R. J. Hoxmeier. 2019. Paddlesh migrations and
movements: a review of tagging and telemetry studies. Pages 4965 in
J. D. Schooley and D. L. Scarnecchia, editors. Paddlesh: ecological, aqua-
cultural, and regulatory challenges of managing a global resource. Amer-
ican Fisheries Society, Bethesda, Maryland.
Ward, J. V., K. Tockner, and F. Schiemer. 1999. Biodiversity of oodplain eco-
systems: ecotones and connectivity. Regulated Rivers: Research and Man-
agement 15:125–139.
Webb, M. A. H., J. P. Van Eenennaam, J. A. Crossman, and F. A. Chapman.
2019. A practical guide for assigning sex and stage of maturity in stur-
geons and paddlesh. Journal of Applied Ichthyology 35:169–186.
Zigler, S. J., M. R. Dewey, B. C. Knights, A. L. Runstrom, and M. T. Steingrae-
ber. 2003. Movement and habitat use by radio-tagged paddlesh in the
upper Mississippi River and tributaries. North American Journal of Fish-
eries Management 23:189–205.
ResearchGate has not been able to resolve any citations for this publication.
Chapter
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