331
E adica ion a emp o an ea ly de ec ed in asi e c ay ish: he
case o Paci as acus leniusculus (Decapoda, As acidae) in he
Cli unno Ri e (cen al I aly)
An onella Ca osi1, F ancesca Lo enzoni1, Fa emeh Za ei1, Massimo Lo enzoni1
1 Depa men o Chemis y, Biology and Bio echnologies, Uni e si y o Pe ugia, ia Elce di So o, 06123 Pe ugia, I aly
Co esponding au ho : An onella Ca osi (an onella.ca [email p o ec ed])
Copy igh : © An onella Ca osi e al.
This is an open access a icle dis ibu ed unde
e ms o he C ea i e Commons A ibu ion
License (A ibu ion 4.0 In e na ional – CC BY 4.0).
Resea ch A icle
Abs ac
The signal c ay ish Paci as acus leniusculus (Dana, 1852) is one o he mos ecologically impac ul deca-
pod c us aceans in oduced in Eu ope. As a species o Union conce n, ea ly de ec ion and apid e adica-
ion measu es a e equi ed o p e en i s es ablishmen and sp ead. We aimed o: i) es he e ec i eness
o an e adica ion a emp unde aken o coun e ac he sp ead and con ain he demog aphic g ow h o
P. leniusculus in he Cli unno Ri e Basin (cen al I aly), whe e he species has been de ec ed in 2020; ii)
assess dis ibu ion, age s uc u e and g ow h o P. leniusculus in his in aded a ea. The emo al ac ions
we e conduc ed biweekly, om June 2022 o Decembe 2024, using bo h aps and elec o ishing. Bio-
me ic pa ame e s we e indi idually eco ded, and he demog aphic ea u es and g ow h o P. leniusculus
popula ion we e assessed. In o al, 259 emo al ac i i ies we e ca ied ou and a biomass o 39.74 kg was
emo ed. The p esence o six coho s ( om 0+ o 5+), including he young-o - he-yea (0+), a es ed o
he apid acclima isa ion o P. leniusculus, which ga e ise o a sel -sus aining popula ion in a sho ime.
The g ea es emo al e o s ha e been concen a ed on a small ibu a y, named Fosso Vecchio, whe e
he a e age alues o Ca ch Pe Uni E o (CPUE) showed a signi ican dec easing end o e ime, sug-
ges ing he e ec i eness o he emo al ac ions. Ou indings p o ided some e idence ha ea ly de ec-
ion and e adica ion measu es conduc ed on a small scale, bu wi h high e o , ep esen e ec i e man-
agemen ools o limi popula ion abundance and p e en in asi e c ay ish om sp eading u he .
Key wo ds: Biodi e si y conse a ion, chalk s eams, inland wa e s, in asi e c ay ish, emo al ac i i ies
In oduc ion
Biological in asions ep esen one o he majo causes o biodi e si y loss in
eshwa e s (Riccia di and MacIsaac 2011; Reid e al. 2019). Ac ing as powe ul
gene alis omni o es, c ay ish a e included amongs he mos success ul in ad-
e s in hese en i onmen s (Ghe a di 2012; Twa dochleb e al. 2013; Wacke
and Ha zsch 2021; So o e al. 2023; Ca alho e al. 2025). C ay ish ha e s ong
oppo uni ies o in ading aqua ic sys ems due o hei capaci y o en e he
ood chain a a ious ophic le els and o exploi he conside able ene gy e-
se es o he de i al pool (Ghe a di 2007). In he in aded a eas, signi ican
managemen e o s a e equi ed o p e en damage om alien c ay ish, since
hey ha e he po en ial o di ec ly a ec na i e species ( h ough p eda ion, com-
pe i ion o ood and shel e s, disease ansmission, e c.) as well as indi ec ly
Academic edi o : Ped o Anas ácio
Recei ed:
16 Janua y 2025
Accep ed:
12 June 2025
Published:
7 Oc obe 2025
Ci a ion: Ca osi A, Lo enzoni F, Za ei
F, Lo enzoni M (2025) E adica ion
a emp o an ea ly de ec ed in asi e
c ay ish: he case o Paci as acus
leniusculus (Decapoda, As acidae)
in he Cli unno Ri e (cen al I aly).
In: Anas ácio P, Ribei o F, Chainho P
(Eds) In asions in Aqua ic Sys ems.
NeoBio a 102: 331–350. h ps://doi.
o g/10.3897/neobio a.102.146951
NeoBio a 102: 331–350 (2025)
DOI: 10.3897/neobio a.102.146951
Ad ancing esea ch on alien species and biological in asions
A pee - e iewed open-access jou nal
NeoBio a
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NeoBio a 102: 331–350 (2025), DOI: 10.3897/neobio a.102.146951
An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
a ec ecosys ems ( h ough ood webs and habi a al e a ions) (Fice ola e al.
2012; Twa dochleb e al. 2013). No h Ame ican c ay ish a e o pa icula con-
ce n, conside ing hei abili y o assume a p eponde an ole in aqua ic com-
muni ies when in oduced ou side hei o iginal ange (Vaeßen and Holle
2015; Sou y-G osse e al. 2016); hei de imen al e ec s ha e been linked o
li e his o y ai s (ea ly sexual ma u i y, high ecundi y), wide ole ance o a -
ious en i onmen al condi ions, sca ci y o na u al p eda o s, and compe i ion
wi h na i e c ay ish (Ghe a di 2006; Vaeßen and Holle 2015). Due o he
widesp ead di usion o No h Ame ican c ay ish in Eu ope, many local cases
o na i e species ex inc ion ha e been obse ed (Kouba e al. 2014); he combi-
na ion o biodi e si y loss and ecosys em p ocesses al e a ion o en esul ed in
ecological and economic dis up ions (Lodge e al. 2000).
The signal c ay ish Paci as acus leniusculus (Dana, 1852), na i e o he no h-
wes e n coas o he Uni ed S a es, is conside ed one o he mos widesp ead and
ecologically impac ul decapod c us aceans in oduced in Eu ope (Reb ina e
al. 2015; Chucholl and Chucholl 2021). This species is a ca ie o he c ay-
ish plague, which is le hal o he mos na i e Eu opean c ay ish (Holdich e al.
2009). Mo eo e , i s ecological niche la gely o e laps wi h ha o na i e c ay ish
(P éau e al. 2020); o he de imen al e ec s a e ela ed o p eda o y ac i i y and
en i onmen al al e a ions in he in aded a eas. Wi h i s eeding habi s, P. lenius-
culus modi ies he ood web and al e s he composi ion o aqua ic communi ies,
consuming mac ophy es, o ganic de i us, and p eying on mac oin e eb a es,
amphibians and small ben hic ish (Sou y-G osse e al. 2006; P ocopio 2020).
Fu he mo e, he digging ac i i y associa ed wi h c ea ing shel e , inc eases wa-
e u bidi y, educing ligh pene a ion wi h a consequen d op in p ima y p o-
duc i i y. Digging ac i i y can also damage i e banks, acili a ing hei collapse
(Ha ey e al. 2011). The species has led o he local ex inc ion o many na i e
c ay ish popula ions in Scandina ia, England, and no he n Eu ope (Lodge e
al. 2000; G een e al. 2018). E en in I aly, as in o he Eu opean coun ies, local
ex inc ion o he na i e c ay ish Aus opo amobius pallipes complex (Le eboulle ,
1858) has been epo ed immedia ely a e he in oduc ion o he signal c ay ish
(Ghia e al. 2017); he e a e ew cases in which a na i e popula ion o A. pallipes
complex was obse ed in syn opy wi h P. leniusculus (Ghia e al. 2019).
The dis ibu ion ange o P. leniusculus in I aly, in he pe iod 1981–2015, was
limi ed o some wa e cou ses in he no he n pa o he coun y (Capu o e al.
2007; Mo pu go e al. 2010; Bo e al. 2016; Ghia e al. 2017); he i s epo o
he species in Cen al I aly da es back o 2020, when some indi iduals we e ound
in he Cli unno Ri e (Umb ian po ion o he Tibe Ri e basin) (Della Bella e
al. 2021). The u he sp ead o P. leniusculus in he Apennine wa e cou ses ais-
es se ious conce n because among all he No h Ame ican c ay ish, i s ecological
p e e ences la gely o e lap wi h ha o A. pallipes complex (Sou y-G osse e al.
2006; Chucholl 2013), which being a cold-wa e species p e e en ially colonizes
he uppe i e s e ches (Bo e al. 2016).
Acco ding o he Eu opean In asi e Alien Species Regula ion (EU
1143/2014), due o he de imen al mul i-le el impac s posed by he species
on na i e biodi e si y and ecosys em se ices, P. leniusculus is deemed as spe-
cies o Union Conce n. The e o e, popula ion moni o ing and quick emo al
ac ions sho ly a e i s de ec ion a e equi ed, o p e en a u he sp ead o
333
NeoBio a 102: 331–350 (2025), DOI: 10.3897/neobio a.102.146951
An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
he species. Based on hese egula o y equi emen s, wi hin he LIFE p oj-
ec (IMAGINE IPE/IT/000015) he Umb ia Region p epa ed, an e adica ion
plan ha was s a ed in 2022. The pu pose o he e adica ion a emp was
o con ain he dispe sal and he popula ion g ow h o P. leniusculus in he
Cli unno Ri e Basin. The LIFE P og amme is he EU’s unding ins umen
o suppo ing En i onmen , Na u e Conse a ion and Clima e Ac ion p oj-
ec s h oughou he Eu opean Union (EU).
Two c ucial ai s exp essing species i ness, popula ion pe sis ence and habi a
adap a ion a e: popula ion g ow h and demog aphic cha ac e is ics (Ho mann e
al. 2017). Thus, a deepe knowledge o hese aspec s plays a majo ole in c ay ish
in asions managemen (Guan and Wiles 1999), and i is essen ial o p edic ing
po en ial ange expansion o in asi e species (Chuang and Pe e son 2016).
Wi hin his con ex , he p esen s udy aimed o i) es he e ec i eness o he
e adica ion ac ions, in e ms o limi ing P. leniusculus sp ead and popula ion abun-
dance in he Cli unno Ri e Basin; and ii) assess dis ibu ion, age s uc u e and
g ow h o P. leniusculus popula ion in he in aded a ea.
Ma e ial and me hods
S udy a ea
The Cli unno Ri e (Tibe Ri e Basin, cen al I aly) is a chalk s eam ha
lows o 18 km, in an ag icul u al con ex , wi h an almos cons an slope
(0.18%), and s able he mal and hyd ological egime (wa e empe a u e
ange: 11.8–20 °C; a e age low a e: 1.5 m3/s) (Lo enzoni e al. 2010, 2023).
The s eam o igina es om a heo-limnoc enic sp ing sys em, called “Fon i
del Cli unno”. Despi e he high cul u al, na u alis ic, and landscape alue o
he Cli unno Ri e , which has inspi ed a is s and poe s since Roman imes
(Pascual e al. 2024), i s i e bed is cha ac e ised by he p esence o signi ican
sil deposi s ha ha e buil up o e he yea s because o u ban and indus i-
al discha ges (Lo enzoni e al. 2010). The Cli unno Ri e has been classi ied
as ha ing “mode a e ecological s a us”, in line wi h he assessmen s ca ied
ou by he egional En i onmen al P o ec ion Agency (ARPA Umb ia) in he
yea s 2016–2017 (Della Bella e al. 2021). The hyd og aphic ne wo k o he
Cli unno Ri e Basin is e y complex and a icula ed, due o he nume ous
human-made hyd aulic sys em modi ica ions ca ied ou o e he cen u ies
(Lo enzoni e al. 2023). The Cli unno Ri e hos s an abundan mac ophy e
communi y (Cingolani e al. 2008), while amongs he mos widesp ead ish
species, se e al a e cu en ly acing he h ea o ex inc ion acco ding o he
IUCN Red Lis (IUCN 2024). These include Anguilla anguilla (Linnaeus,
1758) (CR), Sa ma u ilus ubilio (Bonapa e, 1837) (VU), and Ba bus ybe i-
nus (EN). Addi ionally, acco ding o he IUCN Red Lis o I alian Ve eb a es
(Rondinini e al. 2022), he cyclos ome Lampe a plane i (Bloch, 1784) is lis -
ed as ulne able. The na i e c ay ish A. pallipes complex is locally ex inc , while
he in asi e P ocamba us cla kii (Gi a d, 1852) is widely dis ibu ed h ough-
ou he Basin, including he a ea conside ed in his s udy. He e he species
seems o ind sui able condi ions o ep oduc ion only in he downs eam
wa me i e s e ches (Lo enzoni, pe sonal obse a ion).
334
NeoBio a 102: 331–350 (2025), DOI: 10.3897/neobio a.102.146951
An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
Expe imen al design
Fig. 1 schema ically shows he selec ed a ea o P. leniusculus e adica ion ac i i ies,
loca ed in he uppe pa o he Cli unno Ri e Basin. The e adica ion p og amme,
conduc ed using bo h apping and elec o ishing, was based on he esul s o p e-
limina y moni o ing ca ied ou in 2021 (Lo enzoni e al. 2023). The en i e a ea
has been di ided in o 13 s e ches. Nine si es ( om -1 o -9) we e si ua ed ups eam
om he i s de ec ion poin o P. leniusculus (si e 0); h ee si es, numbe ed om 1 o
3 and loca ed downs eam o si e 0, we e selec ed as “con ol si es”, o check he pos-
sible ange expansion, gi en ha , in hese a eas, he species was no de ec ed du ing
he p elimina y moni o ing. The mos abundan P. leniusculus popula ion, occu ing
in he si e iden i ied as he “in asion co e”, was chosen o conduc he demog aphic
and g ow h analyses. Table 1 shows he main en i onmen al cha ac e is ics o each
i e s e ch, including canopy co e (i.e. he pe cen age o ege a ion co e age o
he i e bed), p e alen subs a e (i.e. he dominan pa icle size o he sedimen s),
and shaded a ea (i.e. he pe cen age o ipa ian ege a ion shading). In he p esen e-
sea ch we es ed he hypo hesis ha he e adica ion ac ions we e e ec i e in limi ing
P. leniusculus sp ead and popula ion abundance in he in es iga ed a ea.
Figu e 1. Loca ion o he si es selec ed o P. leniusculus emo al ac i i ies. a. Tibe Ri e wa e shed; b. Topino Ri e sub-wa e shed;
c. Hyd og aphic ne wo k o he uppe Cli unno Ri e Basin and loca ion o he e adica ed s e ches. An as e isk indica es he i s de ec-
ion si e. The shaded a ea includes he species occu ence s e ches. The dashed a ow indica es he sp ead di ec ion o he signal c ay ish.
335
NeoBio a 102: 331–350 (2025), DOI: 10.3897/neobio a.102.146951
An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
Table 1. Lis o sampling si es along geog aphical coo dina es, and main en i onmen al ea u es. Canopy co e , P e alen subs a e and
Shaded a ea e e o: ege a ion co e age o he i e bed, dominan pa icle size o he sedimen s, and ipa ian ege a ion shading, espec i ely.
Ri e s e ches
code and locali y Geog aphic coo dina es A e age
dep h (m)
A e age
wid h (m)
Canopy
co e (%)
P e alen
subs a e
Shaded
a ea (%)
An h opisa ion
le el Type o dis u bance
CL0 Pia o B idge
i s de ec ion si e
33 T 4747402.16 m N,
315656.63 m E
0.9 6 75 Sil 30 Ve y high Canalisa ion, Di use o ganic
pollu ion
CL1 Bo go T e i 33 T 4749177.40 m N,
314823.23 m E
0.8 12 90 Sil 90 High Canalisa ion, Di use o ganic
pollu ion, P esence o obs acles
FS2 Pie a ossa 33 T 4750596.97 m N,
313932.25 m E
0.4 1 20 Sil 50 Ve y high Canalisa ion, Poin -sou ce
o ganic pollu ion
IR3 Bo go T e i 33 T 4750793.29 m N,
314195.95 m E
0.5 2 10 Sil 10 Ve y high Canalisa ion , Di use o ganic
pollu ion
CL(-1) Pigge 33 T 4746511.93 m N,
316183.45 m E
0.7 12 70 Sil - Fine
G a el
10 Mode a e Canalisa ion
FI(-2) Pigge 33 T 4746497.39 m N,
316178.65 m E
0.7 2.5 30 Sil 20 Mode a e Canalisa ion, Di use o ganic
pollu ion
FP(-3) T epon i 33 T 4745034.65 m N,
316789.89 m E
1 2.5 20 Sil 50 High Canalisa ion, Di use o ganic
pollu ion
FM(-4) T epon i 33 T 4745058.25 m N,
316802.64 m E
0.4 4 20 Sil - Fine
G a el
80 High Canalisa ion, Di use o ganic
pollu ion
CL(-5) T epon i 33 T 4745128.83 m N,
316837.82 m E
1 10 100 Sil - Sand 30 Mode a e Canalisa ion, Di use o ganic
pollu ion
FV(-6) T epon i 33 T 4745008.15 m N,
316869.76 m E
0.5 3 80 Sil 80 High Canalisa ion, Di use o ganic
pollu ion
CL(-7) Fon i 33 T 4744708.80 m N,
317445.71 m E
1 8 90 Sil - Sand 70 Mode a e Canalisa ion
FV(-8) Fon i 33 T 4744664.53 m N,
317446.05 m E
0.3 2.5 20 Sil 100 Ve y high Canalisa ion, Di use o ganic
pollu ion, P esence o obs acles
FN(-9) T epon i 33 T 4744929.48 m N,
316845.18 m E
0.5 2.5 70 Sil 50 Ve y high Canalisa ion, Poin -sou ce
o ganic pollu ion
Remo al ac i i ies
Bai ed aps and a i icial e uge aps
The emo al ac ions we e conduc ed biweekly, om June 2022 o Decembe
2024, using wo ypes o aps: bai ed and a i icial e uge aps (ART). Bai -
ed aps consis ed o double en y cylind ical (50 × Ø 30 cm) plas ic cages,
wi h a mesh size o 0.5 cm. They we e bai ed wi h d y ood o ca s o ish. In
o al, up o 22 bai ed aps we e used, wi h an a e age alue o 15. The aps
we e placed, app oxima ely 25 m apa om each o he , in a semi-subme ged
posi ion along he banks, o a oid causing dis u bance o non- a ge species
ha could be a ac ed by he bai , ollowing indica ions epo ed in he signal
c ay ish Na ional Managemen Plan (T ica ico e al. 2021).
Following G een e al. (2018), o collec mo e indi iduals ep esen a i e o small
size anges, he use o bai ed aps was conside ed mo e e ec i e in combina ion
wi h ART. ARTs we e made o se en PVC ubes, o which wo o 10-, 20-, 32- di-
ame e , espec i ely, and one o 50-mm diame e , and all 400 mm long, joined by
a clamp, and closed by a ine mesh ne a one end. Up o 10 ARTs we e employed
in o al, wi h an a e age alue o se en; hey we e placed close o bai ed aps, in
he a eas mos equen ed by ju eniles.
The end in ca ches o e ime was assessed by Ca ch pe Uni E o
(CPUE), calcula ed as a daily a e age o ca ches pe ap (bai ed and ART). As
P. leniusculus is a species o Union conce n, all indi iduals we e ozen imme-
dia ely a e cap u e and all specimens we e b ough o he labo a o y o sex
de e mina ion and biome ic measu emen s.
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NeoBio a 102: 331–350 (2025), DOI: 10.3897/neobio a.102.146951
An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
Elec o ishing
Limi ed o wadable s e ches, in all he 13 i e s e ches, he emo al ac i i ies
included elec o ishing, using a 4.5 kW elec o shocke . The in e en ions we e
ca ied ou on a seasonal basis, excluding win e , applying a ime o 45/60 minu es
a each sampling si e. The a e age leng h o he i e s e ches was 40 m ( ange:
15–120 m); hey we e sampled by a leas h ee ope a o s, p oceeding om down-
s eam o ups eam. In some pa s o he Cli unno Ri e , whe e he wa e was oo
deep o elec o ishing, he ca ches we e made along he i e banks.
En i onmen al cha ac e isa ion
To in es iga e he en i onmen al condi ions ha could mos in luence he p esence
and ac i i y o he signal c ay ish, a he same ime as elec o ishing, he ollowing
physico-chemical pa ame e s we e measu ed: wa e empe a u e (°C), pH (uni s),
elec ic conduc i i y (μS cm-1) and dissol ed oxygen (mg l-1). The measu emen s
we e conduc ed simul aneously wi h he elec o ishing emo al ac i i ies, using a
mul ipa ame ic p obe (Hanna Ins umen s, Pado a, I aly).
Labo a o y ac i i ies
Fo each indi idual iden i ied as P. leniusculus based on mo phological cha ac e s
(i.e. whi e o al pa ch a he join o he claw inge s and wo pai s o pos -o bi al
idges), sex was de e mined, he o al weigh was measu ed using a digi al scale
(accu acy ± 0.1 g) and he ollowing biome ic pa ame e s we e measu ed using a
callipe (accu acy ± 1 mm): cephalo ho ax leng h (CL) om he ip o he os um
o he pos e io edge o he ca apace and he o al leng h (TL) om he ip o he
os um o he elson. Cheliped damage (absen o egene a ing) o he p esence o
o he mac oscopic lesions we e also eco ded.
Demog aphic ea u es and g ow h o P. leniusculus popula ion
Fo he FV(-6) popula ion, he o al leng h-weigh ela ionship (LWR) was es i-
ma ed by he leas -squa es me hod (Ricke 1975), based on he loga i hmic equa-
ion: log10 W (g) = a + b log10 CL (cm), whe e a is he in e cep on he Y-axis and
b is he eg ession coe icien . The s anda d e o was calcula ed o he slope (b) o
LWR. Isome ic g ow h was es ed h ough a - es , using he equa ion:
s = b-3/Sb
whe e Sb is he s anda d e o o he slope (b), o α = 0.05 (Sokal and Rohl 1987).
The LWR was i ed bo h o he o al sample and sepa a ely o males and emales.
Age classes we e es ima ed by Bha acha ya’s me hod based on he CL equen-
cy dis ibu ion da a (Bha acha ya 1967), using he so wa e FiSAT II (FAO-
ICLARM S ock Assessmen Tools . 1.2.2).
Theo e ical g ow h was es ima ed by he on Be alan y g ow h cu e model
(VBGE) ( on Be alan y 1938): whe e CL is he ca -
apace leng h o he c ay ish a ime , L∞ he heo e ical maximum ca apace leng h
(cm), k he a e o app oach o L∞ and 0 he heo e ical age (in yea s) a which
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NeoBio a 102: 331–350 (2025), DOI: 10.3897/neobio a.102.146951
An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
CL = 0. Fu he mo e, he index o g ow h pe o mance (Φ’) was calcula ed by he
equa ion o Pauly and Mun o (1984): Φ’ = log10 k + 2 log10 L∞ whe e k and L∞ a e
he g ow h pa ame e s o he on Be alan y model.
S a is ical analysis
To es he di e ences be ween mean CPUE amongs si es, amongs yea s and
he in e ac ion be ween hese a iables (si e x yea ), a wo-way ac o ial ANOVA
was pe o med. A one-way ANOVA was pe o med o compa e physico-chemical
pa ame e s amongs si es. Fo LWR, di e ences be ween sexes we e assessed by
ANCOVA. To compa e he leng h o P. leniusculus caugh by di e en emo al
me hods, a K uskal-Wallis ANOVA was pe o med. The no mali y o leng h da a
dis ibu ion was es ed by Shapi o–Wilk es . All s a is ical es s we e conduc ed
using Dell STATISTICA 13 so wa e o Windows.
Resul s
Remo al ac i i ies and P. leniusculus dis ibu ion
Bai ed aps and a i icial e uge aps
A o al o 180 emo al ac i i ies we e conduc ed. The o e all e o applied h ough
se ing aps was equal o 2057 ap days in 2022, 5583 ap days in 2023, and 8708
ap days in 2024. O e all, 1075 Paci as acus leniusculus indi iduals we e emo ed
o a o al biomass o 37.9 kg. This species was only caugh ups eam om he i s
de ec ion si e (Fig. 1), whe e he la ges sample (91.63% o o al indi iduals) has
been emo ed om Fosso Vecchio, a small ibu a y o he Cli unno uppe s e ch.
In FV(-6) we obse ed a p og essi e dec easing end o e ime o he mean annual
CPUE alues (± SE), which d opped om 0.284 ± 0.071 ind/ ap day eco ded
in 2022 o 0.065 ± 0.005 in 2024 (Fig. 2). A d as ic educ ion o CPUE was also
obse ed in he same pe iod o FM(-4) and CL(-5), whe e he mean annual alues
(± SE) dec eased om 0.070 ± 0.055 o 0.024 ± 0.008 and om 0.018 ± 0.061 o
0.001 ± 0.014 ind/ ap day, espec i ely. A all o he si es, no P. leniusculus indi id-
uals we e cap u ed in 2024 by aps. The e a e di e ences be ween he mean alues
amongs si es ( wo-way ac o ial ANOVA: F = 32.19; P = 0.004), and a signi ican
in e ac ion be ween hese a iables ( wo-way ac o ial ANOVA: F = 2.51; P = 0.001).
Du ing he e adica ion in e en ions, a p og essi e signi ican dec easing end in
he a e age daily CPUE alues was obse ed h ough ime o aps in he FV(-6) (Fig.
3). The compu ed equa ion was y = 2.83 - 0.025 · x (F = 6.56; P = 0.022; 2 = 0.46);
he eg ession slope signi ican ly di e ed om 0 ( = 2.79; d = 9; P = 0.022).
Fo bai ed aps, he analysis o he mon hly end in CPUE alues allowed us o
iden i y wo peaks, occu ing in Ap il and Augus (Fig. 4), wi h mean alues (± SE)
eco ded a 0.27 ± 0.05 and 0.21 ± 0.02, espec i ely. The lowes alues we e obse ed
in Janua y (mean ± SE = 0.02 ± 0.02) and Feb ua y (mean ± SE = 0.02 ± 0.01). The
di e ences amongs he mean alues we e s a is ically signi ican (one-way ANOVA:
F = 2.69; P = 0.003). Fo ARTs, he mon hly mean alues we e always lowe han
hose o bai ed aps; he lowes alues we e obse ed in Decembe (0.004 ± 0.003)
and Janua y (ze o ca ches). Howe e , in his case, he di e ences amongs he mean
alues we e no s a is ically signi ican (one-way ANOVA: F = 1.74; P = 0.08).
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An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
Elec o ishing
A o al o 79 elec o ishing emo als we e ca ied ou , du ing which o e all 28 speci-
mens we e collec ed. The mean o al leng h o indi iduals (± SE) was 10.0 ± 2.59 cm
( ange 4.3–13.5 cm); he mean weigh (± SE) was 38.66 ± 23.77 g ( ange 2.3–
72.0 g). This me hod p o ed i s e ec i eness in CL0 and FV(-6), wi h cap u es e-
co ded exclusi ely in 2022 and 2023. In 2024, wo indi iduals we e also cap u ed
om FM(-4) (Fig. 5).
Figu e 3. T end o e ime in mean seasonally CPUE alues o P. leniusculus du ing e adica ion in e en ions conduc ed wi h bai ed aps
and a i icial e uge aps in he Fosso Vecchio Ri e . The solid line ep esen s linea eg ession (equa ion: y = 2.83–0.0251*x; P = 0.0218;
2 = 0.46). The do ed lines ep esen con idence limi s (95%).
Figu e 2. Bai ed aps and a i icial e uge aps: mean annual CPUE alues o P. leniusculus a e b oken down by yea and emo al si es
alling wi hin he in aded a ea. Ve ical ba s deno e s anda d e o s.
339
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An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
Selec i i y o emo al me hods
The mean leng h (± SE) o indi iduals caugh wi h ARTs (7.36 ± 0.27 cm) was
signi ican ly lowe om hose o bo h bai ed aps (10.04 ± 0.04 cm) and elec o-
ishing (9.60 ± 0.58 cm) a he K uskal-Wallis ANOVA (χ2 = 38.44; P < 0.001).
Sex a io did no di e signi ican ly amongs di e en emo al me hods a he chi-
squa e es (χ2 = 1.10; P = 0.578).
En i onmen al cha ac e isa ion
Wa e empe a u e anged om 11.20 °C, eco ded in FM(-4), o 19.36 °C, e-
co ded in FN(-9) (Fig. 6a). The di e ences be ween he mean alues calcula ed o
he 13 si es we e s a is ically signi ican (one-way ANOVA: F = 5.27; P < 0.001).
Figu e 4. Mon hly mean CPUE alues o P. leniusculus du ing e adica ion in e en ions conduc ed wi h bai ed aps and a i icial e uge
aps in he Fosso Vecchio Ri e . Ve ical ba s deno e con idence limi s.
Figu e 5. Elec o ishing: mean annual CPUE alues o P. leniusculus a e b oken down by yea and emo al si es alling wi hin he in aded
a ea. Ve ical ba s deno e s anda d e o s.
346
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An onella Ca osi e al.: Alien c ay ish emo al ac i i ies in a Medi e anean chalk s eam
Use o AI
No use o AI was epo ed.
Funding
This s udy was suppo ed and unded by LIFE IMAGINE – LIFE19 IPE/IT/000015 wi hin he
amewo k o he Eu opean Commission Li e P ojec s.
Au ho con ibu ions
Concep ualiza ion: ML, AC. Da a cu a ion: FZ. Fo mal analysis: AC. Funding acquisi ion: ML.
In es iga ion: FZ, FL, ML. Me hodology: ML. Supe ision: ML. W i ing - o iginal d a : AC. W i -
ing - e iew and edi ing: FL, ML.
Au ho ORCIDs
An onella Ca osi h ps://o cid.o g/0000-0003-0513-7287
Massimo Lo enzoni h ps://o cid.o g/0000-0002-8548-9487
Da a a ailabili y
All o he da a ha suppo he indings o his s udy a e a ailable in he main ex .
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