(Tattersall and Tattersall 1951), and S. clausii, a
littoral species (Genovese 1956a), seemed to be
associated mainly with the inner stations. S.
armata has its most abundant period during late
spring and early summer, differently from that
observed by Mees et al. (1993) for coastal and
estuarine waters of the south-western
Netherlands, where a bimodal abundance pattern
with maxima in spring and autumn was recorded. This species is not very abundant in the
Stagnone during summer, as it probably departs
for colder and deeper areas, as reported by
Cuzin-Roudyand Tchernigovtzeff (1985) for the
Ligurian Sea. It reproduces from March to
August, confirming observations made by
Mauchline (1980) for other littoral habitats;
whereas Ariani (1967) reported a longer reproductive period (March-October) for the Adriatic
coasts of Apulia. This species is the only one in
the Stagnone to show a sex ratio which is slightly
biased towards males. This could be caused by an
underestimation of the actual number of
females. which show secondary sexual features
which can be recognised when a bigger body size
is reached in comparison with that of males
(Mauchline 1980). with the result that females
may be erroneously classified as juveniles. The S.
clausii also shows its maximum density between
late spring and early summer, as observed by
Genovese (1956a) for the Lake of Faro. Differently
from S. armata, this species also shows a moderate abundance in the winter months. In the
"Stagnone di Marsala" S. clausii prefers the inner
area and, in particular, the stations characterized
by P. oceanica, as pointed out by Furnestin (1959)
for the Moroccan waters of the Atlantic Sea. It
shows a single reproductive period (from March
to October), as observed by Genovese (1956a,
1963) for the Lake of Faro (where it reproduces
from March to July), and in contrast with the
marine forms which have two separate reproductive periods in spring and autumn (Colosi 1929;
Tattersall and Tattersall 1951).
The M. gibbosa, a neritic species most frequently found in shallow waters (Ariani 1967),
shows a spring peak in abundance. It is present at
a fairly low density in winter and disappears
almost completely in late summer to early
autumn. As reported by Mauchline (1970, 1980),
this species seems to prefer areas with a lot of
organic terrigenous fall-out material. In the
Stagnone M. gibbosa reproduces from April to
June, the same period reported by Mauchline
Mysid Community in the "Stagnone di Marsala" (Western Sicily)
153
(1980) for British coasts of the Northeast
Atlantic.
The M. slabberi is a typically euryhaline
species (Tattersall and Tattersall 1951; Mees et al.
1993) and is little represented in the "Stagnone di
Marsala.". It is present at a very low density and
mainly during the autumn-winter period. This is
in contrast with what has been reported by Vaan
der Baan and Holthuis (1971). according to
whom this species moves towards off-shore
waters during the winter period. In the Stagnone
M. slabberi is more abundant near areas of urban
discharge (Stn 9), confirming what has been
noted by Ariani (1967) for the Adriatic coast of
Apulia. Reproductive females were never collected in the Stagnone but, as reported by Mauchline
(1980) for British coasts, M. slabberi seems to
reproduce throughout the year. particularly in
spring and summer.
Analysis of the results obtained shows clear
distribution patterns which vary from species to
species. These distribution patterns, such as the
relative abundance of different species, may, in
such a complex environment, be ascribed to the
synergy of a number of factors. both biotic and
abiotic, as has already been observed by Williams
and Collins (1984) for the Bristol Channel.
Among these, temperature, salinity, vegetal covering, quantity of organic detritus and water
quality seem to be the most important. Some
merely biotic factors such as predation, spacetime variations in food sources and interspecific
competition for food resources may also be
determinant.
In the "Stagnone di Marsala". predation by
the "resident" (Quignard 1984) fish species, especially pipefishes and sandsmelt. is very important. In fact Syngnathus typhle feeds almost
exclusively on mysids, which constitute more
than 95% of the diet of the adult specimens and
more than 40% of that of the juveniles (percentages refer to the total number of prey) (Scilipoti
1998). Mysids also form a considerable part of
the diet of S. abaster (up to 12%) and Atherina
boyeri (up to 10%) adults (Scilipoti 1998), and
are preyed on to a lesser extent (up to about 3%
of diet) by juveniles of M. surmuletus, a transient
species in the Stagnone (La Rosa et al. 1997).
The array of known predators of mysids
indicates their importance in the food webs of
this environment.
Their contribution to the trophodynamics is
probably also through the remineralization of
littoral species (Genovese 1956a), seemed to be
associated mainly with the inner stations. S.
armata has its most abundant period during late
spring and early summer, differently from that
observed by Mees et al. (1993) for coastal and
estuarine waters of the south-western
Netherlands, where a bimodal abundance pattern
with maxima in spring and autumn was recorded. This species is not very abundant in the
Stagnone during summer, as it probably departs
for colder and deeper areas, as reported by
Cuzin-Roudyand Tchernigovtzeff (1985) for the
Ligurian Sea. It reproduces from March to
August, confirming observations made by
Mauchline (1980) for other littoral habitats;
whereas Ariani (1967) reported a longer reproductive period (March-October) for the Adriatic
coasts of Apulia. This species is the only one in
the Stagnone to show a sex ratio which is slightly
biased towards males. This could be caused by an
underestimation of the actual number of
females. which show secondary sexual features
which can be recognised when a bigger body size
is reached in comparison with that of males
(Mauchline 1980). with the result that females
may be erroneously classified as juveniles. The S.
clausii also shows its maximum density between
late spring and early summer, as observed by
Genovese (1956a) for the Lake of Faro. Differently
from S. armata, this species also shows a moderate abundance in the winter months. In the
"Stagnone di Marsala" S. clausii prefers the inner
area and, in particular, the stations characterized
by P. oceanica, as pointed out by Furnestin (1959)
for the Moroccan waters of the Atlantic Sea. It
shows a single reproductive period (from March
to October), as observed by Genovese (1956a,
1963) for the Lake of Faro (where it reproduces
from March to July), and in contrast with the
marine forms which have two separate reproductive periods in spring and autumn (Colosi 1929;
Tattersall and Tattersall 1951).
The M. gibbosa, a neritic species most frequently found in shallow waters (Ariani 1967),
shows a spring peak in abundance. It is present at
a fairly low density in winter and disappears
almost completely in late summer to early
autumn. As reported by Mauchline (1970, 1980),
this species seems to prefer areas with a lot of
organic terrigenous fall-out material. In the
Stagnone M. gibbosa reproduces from April to
June, the same period reported by Mauchline
Mysid Community in the "Stagnone di Marsala" (Western Sicily)
153
(1980) for British coasts of the Northeast
Atlantic.
The M. slabberi is a typically euryhaline
species (Tattersall and Tattersall 1951; Mees et al.
1993) and is little represented in the "Stagnone di
Marsala.". It is present at a very low density and
mainly during the autumn-winter period. This is
in contrast with what has been reported by Vaan
der Baan and Holthuis (1971). according to
whom this species moves towards off-shore
waters during the winter period. In the Stagnone
M. slabberi is more abundant near areas of urban
discharge (Stn 9), confirming what has been
noted by Ariani (1967) for the Adriatic coast of
Apulia. Reproductive females were never collected in the Stagnone but, as reported by Mauchline
(1980) for British coasts, M. slabberi seems to
reproduce throughout the year. particularly in
spring and summer.
Analysis of the results obtained shows clear
distribution patterns which vary from species to
species. These distribution patterns, such as the
relative abundance of different species, may, in
such a complex environment, be ascribed to the
synergy of a number of factors. both biotic and
abiotic, as has already been observed by Williams
and Collins (1984) for the Bristol Channel.
Among these, temperature, salinity, vegetal covering, quantity of organic detritus and water
quality seem to be the most important. Some
merely biotic factors such as predation, spacetime variations in food sources and interspecific
competition for food resources may also be
determinant.
In the "Stagnone di Marsala". predation by
the "resident" (Quignard 1984) fish species, especially pipefishes and sandsmelt. is very important. In fact Syngnathus typhle feeds almost
exclusively on mysids, which constitute more
than 95% of the diet of the adult specimens and
more than 40% of that of the juveniles (percentages refer to the total number of prey) (Scilipoti
1998). Mysids also form a considerable part of
the diet of S. abaster (up to 12%) and Atherina
boyeri (up to 10%) adults (Scilipoti 1998), and
are preyed on to a lesser extent (up to about 3%
of diet) by juveniles of M. surmuletus, a transient
species in the Stagnone (La Rosa et al. 1997).
The array of known predators of mysids
indicates their importance in the food webs of
this environment.
Their contribution to the trophodynamics is
probably also through the remineralization of