Is Mass Removal an Efficient Measure to Regulate the North American Catfish Ameiurus melas Outside of Its Native Range?

Abstract

The black bullhead (Ameiurus melas) is a North American species that has successfully established populations throughout Europe. The main management policy to regulate its population in France is systematic mass removal by fishers, but the efficiency of this measure has not been evaluated. In the Grande Brière Motièrre marsh (northwest France), this species currently dominates the fish assemblage. We sampled this black bullhead population with trap nets and by electrofishing. The non-commercial fishery was also surveyed. Length-frequency distributions were significantly different between trapped individuals and those sampled by electrofishing, suggesting a size-selectivity of trap nets. Abundance of black bullhead was negatively correlated with the fishermen activity, measured at variable locations of the study site. The young-of-the-year/adult ratio was constant at each site, suggesting that black bullhead might not compensate for fishing mortality with increased recruitment.

Full text

ls Mass
Removal
an Efficient
Measure
to
Regulate
the_North
American
catfish Ameiuru; melas
Outside
of lts Native
Range?
Julien
cucherousset,
Jean-Marc
paillisson,
and Alexandre
carpentier
UMR 6553
ECOBIO,
Biologie des
populations
et de ta Conseruation
Université
de Rennes
t - CNFS /
Campus
de Beaulieu,
Avenue
du Général
Leclerc
35042
Rennes,
France
E-m
ai I : julien.
cuch
erousset
@ un iv_
rennes
I .fr
ABSTRACT
fishing mortality with increased
recruitmànt.
INTRODUCTION
, The black bullhead (Ameiurus
melas)
is a North American species
that has
successfully
established
populations
througirout
Europe.
The main management
policy to
regulate
its population in France
is systemàtic
mass
removal by fishers,
Uut
tne "fficià"y
of this measure
has
not been
evaluated.
In the Grande
Brière ùotiène marsh
(northwest
France),
this species
currently dominates
the fish assemblage.
we sampled
this black
bullhead population withtrap nets
and
by electrofishing.
Tte norr-"or.,-".cial fishery
was also. surveyed.
Length-frequency
distributions
were significantly different between
ft'apped
individuals and those
sampled
by electrofishing,
siggesting a size-selectivity
of
tra.g
1ets.
Abundance
of black bullhead
was negatively
corrétatea
*ittr ttt" fishermen
activity, measured
at variable locations
of the study siie. The young-of-the
-year
/ adult
ratio was constant
at each
site, suggesting
that blaék
builhead
migÈt not compensate
for
i. - _
During the two last centuries,
Tany fish species
have
been introduced
in Europe,
notably from North America, with variabie ,.r""àr, of naturalization
(review in copp ei
al' 2005). The black bullhead (Ameyrus melas),
an ictalurid fish native to North Aïerica,
ls anexample of a non-indigenous
fish species
iirat has
successfully
established
lations.
throughout
Europe (wheeler l97g) and particularly in France
where
it was
luced in 1871
(Boët 2001). whereas
this speciei is well rtoai"d in its native range
(e.g.' Hanchin et aI.2002a,
Brown et al. 1999),
few studies
have
been conducted
in its
non-native
range
in Europe (but see Boiit l9g0).
Despite
its classification
as
a "species
liable to cause
biological disequilibrium" by
legislation (article R. 232-3
code rural, see
Guevel 1997),
few management
have
been
undedaken
in the country to limit its increasing
populattns. one
measure
is the obligation for fishers
to eliminate all captured
inàiviauat. Recently,
and Declerck (2006) experimentally
showed
that trapping may potentially be a
effective tool for the mass
removing of brown bullhead
(Améiuis'nebulosus\.
, the efficiency of this measure
to limit black bunhead population size
has
e83).
been
assessed
outside
ofits native range
to our knowledge (but see
Hanson
et al.
The objective ofthis study
was to investigate
the effect ofthe trap-net fishery on
black bullhead population in a man-made
*ellaod (Grande
grière N4ïftière
marsh,
rthwest
France).
First, we compared
the length-frequency
distributions of black
llhead
from the frap-net
fishery with electrofishing
to evàluate
the size-selectivitv
of
rùrrçrJ
wr.u çrççuuus{llng
ro evaluaïe
Ine slze-selectlvlty
gears.
Then, we investigated
whether
black bullhead
abundances
were related
to
iable fishermen
activity to assess
the efficiency of this management
tool.
METHODS
AND MATERIALS
area
andfishermen
activity
surl)ey
Grande
Brière Mottière (Fig. l) is a 7000 ha freshwater
marsh located
on the Loire
drainage
in northwest
France (47"22'N,02'r l'w) with a water regime regulated
699
of Freshwater
Ecology,
Volume
21,
Number
4
- December
2006

by a sluice
at the outlet. The area is composed
of a complex web of permanently
flooded
ditches
within a patchwork of temporary
flooded habitats
mainly composed
of ieed beds
(lhl1gmitel australis) and
grasslands
(Poaceae;
see
Eybert et al. I I 99S] and Carpentier
et
al.120041
for details).
Based
on traditional habits,
the study site is dividid into eight
zones
where fishing is permitted (mean
area
of land cover: 905 ha + 366 S.D.). The fwo
protected
areas
(250 and 700 ha, respectively),
where fishing is totally prohibited, were
not included in the study.
The study site supports
a traditional fishery cômposed
of non-
commercial fishers that target the European eel (Anguilla anguilla) and large piscivorous
fish such as northern pike (Esox lucius) and pikeperch (sander lucioperca)-. The black
bullhead,
introduced
in 1929
(Maillard 1972) and
currently dominating the local fish
assemblage
(authors,
unpublished
data),
is principally captured
by eel fishers
that use
modified trap nets
(i.e., eel pots). In 2005, we questioned
2g fishers
using eel pots (i.e.,
58% of the fishers
using this gear)
to evaluate
the fishermen
activity in eàch
of the eight
zones
of the Grande Brière Mottière marsh.
Fishermen
activity was calculated
as
the
number
of eel
pots per kilometer of ditch in each zone.
Black bullhead
sampling
The black bullhead population was sampled
in 2004 using trap nets
and electrofishing.
Trap nets, which have already
proven their efficiency to monitor black bullhead
population
(Hanchin et al.2002b), were used
to establish
the size-class
distribution of
rilffil
FqiqlË'*.j
'- Ditch network
l---l Fished
area
lll,.ïil Protected area
..... Zone
delimitation
f Ebctrofishing
Q Trapping
N
I
1Km
Figure l. Map of the Grande Brière Mottière marsh
ditch network and location of
trapping surveys
and ditches
sampled
by eleckofishing in 2004.
700

black bullhead caught
with this gear.
Eight trap nets
(i.e., fishermen
eel pots, 1.5
m long
with 1.0
x 0.4 m frames
and 10
mm mesh)
were randomly set
at three locations
in the
study
area
from May to August, representing
a happing effort of 242
net-nights.
Electrofishing was used
to assess
spatial
variations
in the black bullhead
abundance
in the whole study area
(7, 000 ha) and to define the population length-
frequency
distribution. The point abundance
sampling
method
pÀS, see Nelva et al.
1979)
was used because
it is an efficient and cost:effective
mettrod
for assessing
fish
abundance
(expressed
in catch per unit effort [CpUE] : number
of individuals.FAs-t;
and provides
reproducible
and quantitative
samples
allowing for within- and between-site
comparisons (e.g.,
copp 1989).
Furthermore,
this method
is effective for capturing
all
species
and
most life stages in shallow
waters.
The sâmpling
design
(pAS numbeiper
site) was defined
in accordance
with Copp and
Garner's
(1995) recommendations.
The
sampling
operations
were conducted
using an EFKo F.E.G. 8000 electrofishing
apparatus (30 cm anode
diameter,
400-600
v and 6-10 A) and
consisted
of throwing the
anode
from a boat to a distance
of 5 to 10 m to limit fish escape,
each
pAS being
separated
by a minimum distance
of 50 m (e.g.,
Persat
and Copp 1989).
Sixteen
ditch
sections
were sampled
in August (i.e., after the spawning period of this species)
totaling
401
PAS (mean: 25.1
+3.2 S.D.
per
ditch). In total, 5,0g4
fish
were
caught,
and
a
minimal sub-sample
of 100
individuals was measured
to the nearest
mm in each
ditch
section.
From the inspection
of length-frequency
distributions,
we used
a 70 mm total
length threshold
to distinguish young-of-the-year
(YOY) from adults,
this threshold
being
in accordançe
with results
of Hanchin et al.
(2002a).
Because
yoy are
not caught
by
fisher trap nets as
a consequence
of eel
pot mesh-size,
they were removed
fronr-the
àata
set collected
by electrofishing
to compare
length distributions.
Black bullhead
abundance
(CPUE) was logls(x+l) transformed
to conduct
the statistical
analyses.
RESULTS AND DISCUSSION
The length-frequency
distributions
of black bullhead
> 70 mm (Fig. 2) was
different between
trap nets and
electrofishing
(two-sample
Kolmogorov-Smirnov test, KS
= Q.170,
p < 0.001).
This global difference in size-classes
mainly involved the selectivity
by eels
pots of individuals between
70 and 100 mm (i.e., certainly age-l individuals
[Hanchin et al. 2002a]).
Black bullhead
abundance
was negatively
related with fishermen
activity (linear
regression,
n : 16,
R2
: 0.609,
p < 0.001,
Fig. 3), indicating that trap-net
fisners likely
had an effect on bullhead
density.
A major concern
in mass
removal is whether
or not
increased
recruitment
would negate
the benefits of population
reduction
(Hanson
et al.
Electrofishing
(N
= 1,535)
Trapping
(N
= 733)
Size-classes
(mm)
Figure 2. size-frequency
distribution for Ameiurus melas sampled
by trap nets
and
electrofishing
in the Grande Brière Mottière marsh in.2004.
E
I
12
Ero
o
()
-e
(Û
o
.36
(g
.94
(g
e.2
0
701
70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230

r'
iL
1983).
In the
studied
black
bullhead
population,
yoy / adult
ratio
did not vary
in relari.,n
,'
to the
adult
abundance
(linear
regression,
n = 16,
R2
: 0.03, p : 0.503),
*gr"!,i-r* -riî*' ,,
black
bullhead
might
not
compensate
for fishing
mortality
*ia in"rrurJ Ë*ïd*r;* ,
least
under
these
metrics.'rhis
result
is surprising
becausé
mechanical
;;;i;1|;jr*
are generally
temporary
since
the_remaining
fishès
exhibit
compensatory
survival, ,
increased
growth,
and
increased
fecundity,
alr
of which
result
ii " i"pià'r"Jru"rj"r
populations
(wvdoski and
wiley 1999).
Neverthgre.ss,
Hanson
et ur.
1Ds:jàiffi;^
observe
any
significant
increased
recruitment
in theirûhck bullhead
popufation.
In our ,
population,
the
absence
of a significant
relation
between
yoy / ud*li;i";;A;il" ,,
abundance
might indicate
that fishing
mortality affecrs
black
bullheaa
a"rrrtyl"irît
sufficiently
to activate
regulatory
mechanisms.
The
systematic
mass
removal
by fishermen
seems
to be
partry
successful
in
limiting
the
abundance
of black
bullhead
in the
Grande
Brière
Mottièr";;i. - .^' '
Nevertheless,
the
black
bullhead
is still the
dominant
species
in the local
irsh
Lsemulage.
Consequently,
the
use
of this
single
management
measure
currently
is not
sufficient
to
ye{ate the
population.
Recent
works
have
shown
that
alternativ"
-"ut"ro -";ilt"* l
for limiting
the
establishment
of non-native
fishes.
In the
Grande
e.iere ùrottie.;,tlr;*'
invasion
ofnatural
habitats (grassrands)
by reed
beds
during
the
last
""r;t il;;-' -'-
substantially
altered
ecosystem
function (Éybert
et
al. 1998j.
This
habitat
modification
is ,
E
8P
cÈ
(UP
=û,
_dE
(Ee
Ee
(5+
ox
-cv
=o,
d-e
-X uJ
(!J
fiù
-c)
1.6
I
'€
E
0)
?. 1.2
o
o
Ê
€ o.s
g
E
- 0.4
o
4
3.5
3
2.5
2
1.5
1
0.5
04681012
Fishermen
activity
(eel pots
per
km)
R'=
0.03
p =
0.503
^.....- -V-
00.5 't 1.5 22.5 3 3.5 4
o
Adult
abundance
(CPUE,
log (x+1)
transformed)
Figure 3' Relationship
between
total black bullhead
abundance
and fishermen
activity
gd between young-of-the-year
/ adult ratio and adult black bullhead abundance
in the Grande
Brière Mottière marsh.
Abundance
(cpuE) ..rut,rl,
,"."
logle(x+
1
) transformed.
R2
= 0.60
p <
0.001

cedainly one of major cause
for the domination
of the fish assemblage
by the black
bullhead'
Recently, scoppettone
et al. (2005) demonskated
that habitat restoration
could
be valuable
to control.non-native
fish species.
consequently,
we propose
that
managers
continue
the systematic
mass
removal but in conjunctio.,
witi "ut ,ui habitat
restoration
to more efficiently regulate
the black bullhead
population in the Grande
Brière Mottière
marsh.
ACKNOWTEDGMENTS
we are grateful to J.-p. Damien,
E. Le Mitouard, v. Thoby and the numerous
persons
who participated
in the field work. we acknowledge
D.w, wirtis and
two
anon)rmous
referees
for valuable
comments
on an earlier diaft. we thank the parc naturel
régional
de Brière for rogistic and
the pnrB, FEDER, unnN, negr;;;"y, de la Loire
and
Agence de I'Eau from Loire-Bretagne
ior financial ,.rppor1. "---- '
Boët,
p.
1e80.
L'arimentation.'HHH;Y,ï":,Ïï?,
*",o,Rar.)
dans
le
rac
de
Créteil.
Annales
de
Limnoiogie 16:255_270.
Boët,
P' 2001.
Le poisson-chatr
*iiu*, meras (Rafrnesque,
lg20). In: Keith,p.
and
J.
Allardi (eds.),
Atras des poisons
d'eau douce
de Frànce.
put iÀoin", naturers,
MNHN, P
ans,
47
: 222_223.
Brown,
M.L., D.w. willis, and
B.G. Blackwell.
1999.
physicochemical
and
biorogical
influences
on black bullhead
populations
in eastern-
South
Dakoia glacial lakes.
Journal
ofFreshwater Ecology lq: Cl_e}.
Carpentier,
A., J.-M. Paillisson, F,.
FLunteun,
and
L. Mario
n.2004.Fish community
structure
in tempo^rary
loytand flooded grassland.
Bulletin rr"iuir de la pêche
et
de
la Piscicultwe
375:
l_14-
copp, G.H. 1989.
Electrofishing for fish larvae
and
juveniles: equipment
modifications
for increased
efficiency with short fishes.
Aquaculture
anà
Éirh"ri", Management
20:453-462.
Copp, G'H' and
P. Garner' 1995.
Evaluating
microhabitat
use
of fish larvae
and
juveniles
with point abundance
sampling.
Folia
Zoologica
44:145_15g.
copp, G'H.' P.G.
Bianco,
N.G. Bogutskaya,T.Eros,
I. Falka,
M.T. Ferreira,
M.G. Fox,
J.
Freyhof, R.E. Gozlan,
J. Grabowska,
v. Kovac, R. Moreno-Amicn, e.u. Naseka,
M.Penaz,
M. povz,
M. przybylski,
M. Robillard,
f.C. nuss"if S.-Stuk"nur,
S.
Sumer,
A' vila-Gispert, and
c. wiesner. 2005. To be, ôr not to be, a non-native
freshwater
fish? Joumal of Applied Ichthyology Zt: iqZ_ZeZ.
Eybert,
M.-c, J.-Y. Bemard,
p. constant, E. Feunteun,
J. Hédin, and s. euestiau. 199g.
Réhabilitation
des prairies inondables
dans
les marais
briéronsrévolution de la
.fl9*: 9:l poissons
et des
oiseaux.
Gibier et Faune
sauvage
t S: S9S_
t Ot
e .
Guevel,
B. 1997.
La loi pêche_(code
Rural) et l'introductio" a"i "rfé"es piscicoles.
Bulletin Français
de
la pêche
et de
la pisciculture
l+cB+s:il--51.
Hanchin,
P.A., D.w. willis, and
M.J. Hubers. 2002a.
Brack bullheaà
gr;*th in south
Dakota waters:
limnological and
community influences.
ro.r-ui orr.r"shwater
Ecology
17:65-73.
Hanchin,
P.4., D.v/. willis, and
T.R. st. Sauver.
2002b.
comparison of concurrent
trap-
net and
gill-net samples
for black bullheads.
Journal
of Freshwater
Ecology 17:
233-237.
Hanson,
D.A., B.J.
Belonger,
and
D.L. Schoenike.
19g3.
Evaluation
of a mechanical
population reduction
ofblack crappie
and
black bullheads
in a small Vy'isconsin
lake. North American
Journal
of Fisheries
Management
.3: alai.
Louette,
G. and s. Declerck.
2006.
Assessment
and
"orr-t
ol of the non-indigenous
brown
703

bullheadAmeiurus
nebulosas populations
using
fuke
nets irr shallow ponds. ,:i:i
Jounral of Fish
Biology 68:.522-531. , ,:;
Maillard, Y, 1972. Poissons
et
problèmes
piscicoles
du bassin
du Brivet. Penn
ar
386-399.
Nelva 4., H. Persat
and D. Chessel. 1979.Une
nouvelle
méthode d'étude
des
peuplements
ichthyologiques
dans
les grands
cours d'eau par échantillonnage:
,,:,r
ponctuel
d'abondance.
Comptes
Rendus de l'Académie des Sciences2Sg:
1295- ,
1298.
Persat,H.andG'H.Copp.1989.E1ectricfishingandpointabundancesarrplingforttre
ichthyology of large rivers. Pages 197-209
In cowx, I. (ed.),
Development
'n electric l,
fishing. Oxford: Fishing New Books,
Blackwell Scientific Publications. ' .;.
scoppettone,
G.G., P.H. Rissler,
c. Gourley, and c. Martinez.2005. Habitat restoration
as a means
of controlling non-native
fish in a Mojave desert oasis.
Restoration ',
Ecology
13:247-256.
Wheeler, A. 1978.
Ictalurus melas
(Rafinesque,
1820) and,
I. nebuloszs
(Lesueur,
18lg)t:
the North American catfishes
in Europe.
Journal of Fish Biology 12:435-439.
Wydoski, R.S. and R.W. Wiley. 1999.
Management
ofundesirable fish species.
pages, ':r
403-430
1z Kohler, C.C. and W.A. Hubert (eds.),
Inland fisheries
manageme,nt
in
North America. American Fisheries Society, Bethesda,
Maryland.
i.,:i
$
Received:
1 May 2006
704
Accepted: 12 August
2006