Preprint volume - SIBM

Pre-print Volume –Posters
NECTON AND FISHERY COMMITEE
L. ORSI RELINI, L. LANTERI, F. GARIBALDI
Centro di Biologia Marina del Mar Ligure (BIOLMAR)
Corso Europa, 26 – 16132 Genova, Italia.
largepel@unige.it
MEDUSIVOROUS FISHES OF THE MEDITERRANEAN.
A COASTAL SAFETY SYSTEM AGAINST JELLYFISH BLOOMS
PESCI MEDUSIVORI DEL MEDITERRANEO.
UN BALUARDO CONTRO LE MEDUSE
Abstract – More than twenty species of medusivorous fishes are present in the Mediterranean Sea: they can
be grouped in a coastal and an offshore assemblage. Seven species of the former group resulted as top
species in terms of CPUE (catches per fishery season) at the Camogli tuna trap since a long time; given
their relevance as biomass, we consider these species as a “safety system” against jellyfish invasions.
Offshore medusivorous fishes are less known. During recent blooms of Pelagia noctiluca we have observed
the jellyfish consume in five species (three of the coastal group) in which the gut was coloured by medusa
pigments.
Key-words: medusae, pigments, fish predation, Ligurian Sea.
Introduction – Jellyfish blooms being in the spotlight (see for instance JMBA Global
Marine Environment issue 11, 2010), we consider worth of attention a related subject,
that is medusivorous fish. Investigating the reason of the blooms, attention to predators
and/or competitors of medusae, helps to indicate gaps of knowledge and subjects for
future research. The present note correlates the general subject of the fishes which
occasionally or regularly feed on medusae with observations carried out monitoring
fishing activities in the Ligurian Sea: the result underlines the importance of
medusivorous fish.
Results and conclusions - From general reviews about jellyfish consumers including
medusivorous fishes (Ates, 1988; Arai, 1988, 2005) we have selected the species living
in the Mediterranean. Adding some cases observed in the Ligurian Sea (Orsi Relini,
2010; Orsi Relini et al., 2010a), a total of twenty species, plus some casual ones, can be
listed (Tab. 1). A first group (1-11) are deep living fish, both demersal on the slope or
mesopelagic in their adult phase. A second group of species (12 onward) live in neritic
coastal waters and in the Ligurian Sea was studied in temporal series of catches at the
Camogli tuna trap. This trap, located on the western side of the Portofino Promontory,
on a water column of about 40 m, produces about 50t of landings per fishing season
(April-September), including more than 40 species. Annual total landings are
considered CPUE as for large tuna traps, that is proxies of abundance indices.
Temporal series of such data are available for the periods 1950-1974 and 1996-2000
(Balestra et al., 1976; Relini, 2001) and regard the ten species most important in terms
of biomass (called also ten top species); in the above indicated periods they included
the sunfish Mola mola (Orsi Relini et al., 2010b), which was later on banned as food
by EC; at present this fish, if caught, is released alive. It is easily verified that the top
ten species coincide, in 7 cases of 10, with medusivorous species, those numbered 12
to 18 in Tab. 1. The quantitative pattern of catches (CPUEs) and the persistence of the
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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