224
S. Vizzini et al.
suggest that its geographical distribution should
be widened.
As regards the biometric and meristic characters, from the data reported it was not possible
to distinguish between specimens from the two
study sites: only two biometric and one meristic
parameter showed statistically significant differences (Table 3). Generally speaking, biometric
measurements are a tool for identifying different
fish populations; differences in the average number of meristic parameters indicate that stocks
are genetically different (Taning 1951). The
meristic phenotype of fish depends on genetic
and environmental variation. The main environmental factors are: temperature, salinity and
light during egg incubation (Beacham and
Murray 1986). In the case of O. gracilis further
insights (karyotype characterisation, electrophoresis analysis of isoenzyme, nDNA and
mDNA) is needed to make it possible to distinguish between two populations.
Stomach Content AnalYSis
Data on the feeding ecology of O. gracilis are
reported for the first time in this paper. In accordance with its benthic habit O. gracilis feeds on
small phytal prey living on Posidonia leaves.
Throughout the year Copepoda Harpacticoida
are the most common and abundant prey. Their
importance as a food source is well known for
other fish species living in the "Stagnone di
Marsala" (Scilipoti 1998). The dominance of this
systematic group is not surprising since
Copepoda Harpactioida are normally the most
numerous group in the phytal habitat of
"Stagnone di Marsala". In summer and autumn
Tanaidacea also become preferential prey. The
feeding preferences of O. gracilis follow the
annual trend of trophic resources in the study
site. Copepoda Harpacticoida show a peak in
abundance in the winter and spring months,
while their number decrease during summer and
autumn concomitantly with the increase in the
Tanaidacea resource (although the latter are
numerically fewer than the Copepoda
Harpacticoida) (Campolmi 1998). In conclusion
O. gracilis can be defined as a micro-carnivore
specialised on epifaunal Crustacea especially
Copepoda Harpacticoida and Tanaidacea.
References
Beacham TD, Murray CB (1986) The effect of spawning time
and incubation temperature on meristic variation in
chum salmon (Oncorhynchus keta). Can I Zool 64: 45-48
Bini G (1968) Atlante dei pesci delle coste italiane. In: Mondo
sommerso, Roma 8: 129-130
Briggs IC (1986) Gobiesocidae. In: Whitehead PJP, Bauchot
ML. Hureau IC,Nielsen T, Tortonese E (eds) Fishes of the
north-eastern Atlantic and Mediterranean. UNESCO,
Paris, pp 1351-1359
Calvo S, Drago D, Sortino M (1980) Winter and summer submersed vegetation maps of the Stagnone (western coast
of Sicily). Rev Biol-Eeol Mediterr vn 2: 89-96
Calvo S, Giacrone G. Ragonese S (1982) Tipologia della vegetazione sommersa dello Stagnone di Marsala (TP). Nat
Sicil S IV VI(2): 187-196
Campolmi M (1998) Studio della comunita zooplanctonica di
un bassofondo costiero mediterraneo (Stagnone di
Marsala, Sicilia occidentale). PhD thesis, Univ Messina
Cardona 1, Guerao G (1992) Primera cita de Opeatogenys gracilis (Canestrini 1864) (Osteichthyes: Gobiesocidae) en el
litoral catalan (Meditemineo NO). Misc Zoo116: 243-245
Giaccone G, Sortino M (1964) Flora e vegetazione algale di
Isola delle Femmine. Lav 1st Bot Giardino Colon Palermo
21: 3-27
Hyslop EJ (1980) Stomach contents analysis-a review of methods and their application. J Fish BioI 1: 491-429
Pinkas L, Oliphant MS, Iverson ILK (1971) Food habits of
albaeore, bluefin tuna and bonito in California waters.
Calif Dep Fish Game Fish Bull 152
Reina-Hervas JA, NUfiez-Vergara Je (1985) Opeatogenys gracilis (Canestrini 1864) (Gobiesocidae, Osteichthyes) en el
Mediterraneo espafiol. Mise Zoo19: 405-407
Russo GF, Fresi E, Vmci D (1985) The hand-towed net method
for direct sampling in Posidonia oceanica beds. Rapp
Comm Int Mer Mediterr 29(6): 175-177
Scilipoti D (1998) Studio della comunita ittica residente all'interno della Stagnone di Marsala (Sicilia occidentale), con
partieolare riferimento alla distribuzione delle specie e
alla ripartizione delle risone in dipendenza di habitat a
diversa complessita strutturale. PhD thesis, Univ
Messina
Soljan T (1975) I pesci dell' Adriatico. In: Arnoldo Mondadori,
Verona,pp 159-163
Taning AV (1951) Experimental study of meristic characters
in fishes. BioI Rev Cambridge Philos Soc 27: 169-193
Tortonese E (1975) In: Fauna d'Italia: Osteichthyes. Pesd
ossei. Calderini, Bologna. 11, pp 546-555
S. Vizzini et al.
suggest that its geographical distribution should
be widened.
As regards the biometric and meristic characters, from the data reported it was not possible
to distinguish between specimens from the two
study sites: only two biometric and one meristic
parameter showed statistically significant differences (Table 3). Generally speaking, biometric
measurements are a tool for identifying different
fish populations; differences in the average number of meristic parameters indicate that stocks
are genetically different (Taning 1951). The
meristic phenotype of fish depends on genetic
and environmental variation. The main environmental factors are: temperature, salinity and
light during egg incubation (Beacham and
Murray 1986). In the case of O. gracilis further
insights (karyotype characterisation, electrophoresis analysis of isoenzyme, nDNA and
mDNA) is needed to make it possible to distinguish between two populations.
Stomach Content AnalYSis
Data on the feeding ecology of O. gracilis are
reported for the first time in this paper. In accordance with its benthic habit O. gracilis feeds on
small phytal prey living on Posidonia leaves.
Throughout the year Copepoda Harpacticoida
are the most common and abundant prey. Their
importance as a food source is well known for
other fish species living in the "Stagnone di
Marsala" (Scilipoti 1998). The dominance of this
systematic group is not surprising since
Copepoda Harpactioida are normally the most
numerous group in the phytal habitat of
"Stagnone di Marsala". In summer and autumn
Tanaidacea also become preferential prey. The
feeding preferences of O. gracilis follow the
annual trend of trophic resources in the study
site. Copepoda Harpacticoida show a peak in
abundance in the winter and spring months,
while their number decrease during summer and
autumn concomitantly with the increase in the
Tanaidacea resource (although the latter are
numerically fewer than the Copepoda
Harpacticoida) (Campolmi 1998). In conclusion
O. gracilis can be defined as a micro-carnivore
specialised on epifaunal Crustacea especially
Copepoda Harpacticoida and Tanaidacea.
References
Beacham TD, Murray CB (1986) The effect of spawning time
and incubation temperature on meristic variation in
chum salmon (Oncorhynchus keta). Can I Zool 64: 45-48
Bini G (1968) Atlante dei pesci delle coste italiane. In: Mondo
sommerso, Roma 8: 129-130
Briggs IC (1986) Gobiesocidae. In: Whitehead PJP, Bauchot
ML. Hureau IC,Nielsen T, Tortonese E (eds) Fishes of the
north-eastern Atlantic and Mediterranean. UNESCO,
Paris, pp 1351-1359
Calvo S, Drago D, Sortino M (1980) Winter and summer submersed vegetation maps of the Stagnone (western coast
of Sicily). Rev Biol-Eeol Mediterr vn 2: 89-96
Calvo S, Giacrone G. Ragonese S (1982) Tipologia della vegetazione sommersa dello Stagnone di Marsala (TP). Nat
Sicil S IV VI(2): 187-196
Campolmi M (1998) Studio della comunita zooplanctonica di
un bassofondo costiero mediterraneo (Stagnone di
Marsala, Sicilia occidentale). PhD thesis, Univ Messina
Cardona 1, Guerao G (1992) Primera cita de Opeatogenys gracilis (Canestrini 1864) (Osteichthyes: Gobiesocidae) en el
litoral catalan (Meditemineo NO). Misc Zoo116: 243-245
Giaccone G, Sortino M (1964) Flora e vegetazione algale di
Isola delle Femmine. Lav 1st Bot Giardino Colon Palermo
21: 3-27
Hyslop EJ (1980) Stomach contents analysis-a review of methods and their application. J Fish BioI 1: 491-429
Pinkas L, Oliphant MS, Iverson ILK (1971) Food habits of
albaeore, bluefin tuna and bonito in California waters.
Calif Dep Fish Game Fish Bull 152
Reina-Hervas JA, NUfiez-Vergara Je (1985) Opeatogenys gracilis (Canestrini 1864) (Gobiesocidae, Osteichthyes) en el
Mediterraneo espafiol. Mise Zoo19: 405-407
Russo GF, Fresi E, Vmci D (1985) The hand-towed net method
for direct sampling in Posidonia oceanica beds. Rapp
Comm Int Mer Mediterr 29(6): 175-177
Scilipoti D (1998) Studio della comunita ittica residente all'interno della Stagnone di Marsala (Sicilia occidentale), con
partieolare riferimento alla distribuzione delle specie e
alla ripartizione delle risone in dipendenza di habitat a
diversa complessita strutturale. PhD thesis, Univ
Messina
Soljan T (1975) I pesci dell' Adriatico. In: Arnoldo Mondadori,
Verona,pp 159-163
Taning AV (1951) Experimental study of meristic characters
in fishes. BioI Rev Cambridge Philos Soc 27: 169-193
Tortonese E (1975) In: Fauna d'Italia: Osteichthyes. Pesd
ossei. Calderini, Bologna. 11, pp 546-555