MAP Technical Reports Series No. 106 UNEP

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Living, moribund and dead Squilla mantis were on the sediment during the day and
several individuals were observed swimming freely several metres above the bottom
(Stachowitsch, 1984).
Echinoderms
Echinoderms, a major component of the macroepibenthos in the Gulf of Trieste,
showed a variety of behavioural modifications before death in the 2-3 days after the first signs
of stress.
On the second day, the sea start Astropecten aurantiacus was observed on mounds
with greatly extended discs. This stress reaction characterized by a gas-filled stomach was also
observed in Emilia-Romagna Region Italy, near Cesenatico (Rinaldi et al., 1993), and it was
followed on the third day by overturning individuals. Amphiura chisjei, the echinoderm species
last to succumb, was aggregated in large numbers on the tops of mounds. All individuals of the
epibenthic holothurian Holothuria tubulosa were found eviscerated on the first day, with death
taking place on days 2 and 3. On day 1, the burrowing form Thyone fusus emerged from the
sediment.
Fish
In the Gulf of Trieste, small benthic fish were also affected on the first day. Great
numbers of dead goblids Gobius jozo as well as juvenile trachinidae and small flatfish were
found dead on the sediment surface.
In the 1977 mortality event, these fish were concentrated at the core of the affected
area, resulting in increased catches of fish normally not caught together (Stefanon and Boldrin,
1982).
6.2.2 Effect of the oxygen deficiency on the benthic ecosystem of the North-West Adriatic
It is difficult to quantify the effects of the oxygen deficiencies on the stocks of bottomdwelling
fish because of the intensity of the fishing activities to which they are subjected.
However, Hippocampus antiquorum and Trachinus draco are amongst the fish species which
have disappeared or become much rarer, on which fishing practices have had only a negligible
effect.
The most significant observations were made on molluscs and crustaceans.
The following is a list of the species of molluscs and crustaceans which have gradually
become rarer (marked RA) or have actually disappeared (marked DS), since 1975. The
observations refer to the area of sea off the coast of Emilia-Romagna, up to 20 km off shore
(Rinaldi et al., 1993).
Molluscs
Gasteropods
Aporrhais pes-pelecani (L.) RA
Turritella communis Risso RA
Spheronassa mutabilis (L.) RA
Trunculariopsis trunculus (L.) DS
Murex brandaris (L.) DS