Filippo PICCARDI, POLI F., SGUOTTI C., BORME D., TIRELLI V.,
MAZZOLDI C., BARAUSSE A.
Department of Biology, Hydrobiological Station “U. d’Ancona”, University of Padova,
Isola San Domenico 3, 30015 Chioggia, Italy
Email: camilla.sguotti@uni-hamburg.de
PRELIMINARY RESULTS OF THE EFFECTS OF MNEMIOPSIS
LEIDYI A. AGASSIZ 1865 ON A SMALL-SCALE FISHERY IN THE
VENICE LAGOON
Abstract
Mnemiopsis leidyi (Agassiz, 1865) is a highly invasive ctenophore, native to the West Atlantic Sea,
that is currently spreading in the Mediterranean Sea. Blooms were reported also in the Venice lagoon,
a hotspot of habitat richness and biodiversity. However, no studies have been published about the
impacts of this ctenophore on the lagoon ecosystem and its services, as traditional small-scale
fisheries. Combining local ecological knowledge (questionnaires), statistical modelling (time-series
analysis) and field sampling (boardings) we investigated whether the presence of M. leidyi is affecting
artisanal fisheries. Preliminary results indicate that i) overall the landings of the lagoon fishers
strongly declined with the blooms and ii) the mechanical clogging of the nets by the ctenophore
severely impedes fishing activities. Our results call for a better understanding of M. leidyi impact on
both lagoon ecosystems and the socio-economic consequences.
Key-words: invasive species, local ecological knowledge, small-scale fisheries, time series
analysis, M. leidyi
Introduction
In marine habitats, invasive alien species (IAS) are difficult to monitor, hence the
environmental and economic damages they cause are challenging to predict and contrast
(Molnar et al., 2008). Transitional environments, such as lagoons, are highly productive
but delicate environments that provide a wide range of ecosystem services (i.e.,
biodiversity support, nursery areas, feeding grounds, small-scale fishery etc.) (Newton et
al., 2018). Being highly productive refugia areas compared to the open sea, lagoons in
the Mediterranean Sea have been recently suggested to be vulnerable to the invasion of
Mnemiopsis leidyi Agassiz, 1865 (Delpy et al., 2016; Marchessaux & Belloni, 2021) a
ctenophore listed among the 100 most invasive species worldwide (IUCN Lowe et al.,
2000). The Venice lagoon is the largest Mediterranean lagoon, located along the Northern
Adriatic Sea coast. Despite the first bloom of M. leidyi was registered in 2016 (Malej et
al., 2017), nowadays no assessment of its presence and impacts exists.
Materials and Methods
To fill this gap, we dated the appearance, spread and bloom of M. leidyi using structured
questionnaires to recover the ecological knowledge of traditional fishers and the consequences on
their fishing activities. Then, time series (1997-2019) of lagoon fishery landings (kg/day) of the
most valuable species targeted by the local small-scale fishery were extracted using official data
of the Chioggia Fish Market. We included in the analyses the lagoon daily water temperature, a
major driver of both environmental changes and the spread of M. leyidi (Delpy et al., 2016). We
boarded with lagoon fishers to assess M. leyidi biomass over the total net content.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
117
MAZZOLDI C., BARAUSSE A.
Department of Biology, Hydrobiological Station “U. d’Ancona”, University of Padova,
Isola San Domenico 3, 30015 Chioggia, Italy
Email: camilla.sguotti@uni-hamburg.de
PRELIMINARY RESULTS OF THE EFFECTS OF MNEMIOPSIS
LEIDYI A. AGASSIZ 1865 ON A SMALL-SCALE FISHERY IN THE
VENICE LAGOON
Abstract
Mnemiopsis leidyi (Agassiz, 1865) is a highly invasive ctenophore, native to the West Atlantic Sea,
that is currently spreading in the Mediterranean Sea. Blooms were reported also in the Venice lagoon,
a hotspot of habitat richness and biodiversity. However, no studies have been published about the
impacts of this ctenophore on the lagoon ecosystem and its services, as traditional small-scale
fisheries. Combining local ecological knowledge (questionnaires), statistical modelling (time-series
analysis) and field sampling (boardings) we investigated whether the presence of M. leidyi is affecting
artisanal fisheries. Preliminary results indicate that i) overall the landings of the lagoon fishers
strongly declined with the blooms and ii) the mechanical clogging of the nets by the ctenophore
severely impedes fishing activities. Our results call for a better understanding of M. leidyi impact on
both lagoon ecosystems and the socio-economic consequences.
Key-words: invasive species, local ecological knowledge, small-scale fisheries, time series
analysis, M. leidyi
Introduction
In marine habitats, invasive alien species (IAS) are difficult to monitor, hence the
environmental and economic damages they cause are challenging to predict and contrast
(Molnar et al., 2008). Transitional environments, such as lagoons, are highly productive
but delicate environments that provide a wide range of ecosystem services (i.e.,
biodiversity support, nursery areas, feeding grounds, small-scale fishery etc.) (Newton et
al., 2018). Being highly productive refugia areas compared to the open sea, lagoons in
the Mediterranean Sea have been recently suggested to be vulnerable to the invasion of
Mnemiopsis leidyi Agassiz, 1865 (Delpy et al., 2016; Marchessaux & Belloni, 2021) a
ctenophore listed among the 100 most invasive species worldwide (IUCN Lowe et al.,
2000). The Venice lagoon is the largest Mediterranean lagoon, located along the Northern
Adriatic Sea coast. Despite the first bloom of M. leidyi was registered in 2016 (Malej et
al., 2017), nowadays no assessment of its presence and impacts exists.
Materials and Methods
To fill this gap, we dated the appearance, spread and bloom of M. leidyi using structured
questionnaires to recover the ecological knowledge of traditional fishers and the consequences on
their fishing activities. Then, time series (1997-2019) of lagoon fishery landings (kg/day) of the
most valuable species targeted by the local small-scale fishery were extracted using official data
of the Chioggia Fish Market. We included in the analyses the lagoon daily water temperature, a
major driver of both environmental changes and the spread of M. leyidi (Delpy et al., 2016). We
boarded with lagoon fishers to assess M. leyidi biomass over the total net content.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
117