1997). By contrast, macroalgae were the most
important food item in the diet of S. salpa juveniles. In particular, they fed on Rhodophycaea
(Laurencia sp. and Polisiphonia sp.), that have
been reported in this environment (Scilipoti
1998). Our results are in agreement with Antolic
et al. (1994) who found adults of S. salpa, in the
southern Adriatic Sea, feeding mainly on
Rhodophycaea and marine phanerogams.
Among other food items, only Ascidiacea larvae
and Hydrozoa provided an important contribution to the diet of this species.
Juveniles of D. puntazzo always presented a
niche breadth larger than that of S. salpa juveniles. In fact, their diet was composed of largely
diversified prey items, while macro algae represented the dominant fraction of gastric contents
of S. salpa juveniles. Niche overlap of the two
species at 4 pm is dearly due to the intensive
ingestion of Ascidiacea larvae by both D. puntazzo and S. salpa. As the availability of this item in
the environment was scarce, it hypothesised a
competition between the two species for this
kind of resource.
The unimodal trend in the daily feeding
rhythm of both species (without a real feeding
peak), indicates that they were continuously
feeding during the day, but not during the night.
This habit allows them to avoid competition for
food resources with other small-size residential
species. In fact, additional studies carried out in
the same area showed that residential species,
such as Pomatoschistus tortonesei, Aphanius fasciatus and Atherina boyeri, fed largely on same
resources (Copepoda, Amphipoda, Tanaidacea)
(Scilipoti et al. 1997; Scilipoti 1998). Yet, a comparison between diel feeding cycles of these
species suggests that there is a shift in feeding
times in order to reduce trophic competition.
Both D. puntazzo and S. salpa juveniles followed
a square root model of gastric evacuation with a
gastric evacuation rate of 0.011 and 0.014 g DW
h- 1 , respectively. These low rates of gastric evacuation may be due to a number of factors such as
their very small size. the scant amount of food
ingested, water temperature, and food quality. It
is well known that all these factors may influence
gastric evacuation rates (Tobling 1987; Dos
Santos and Jobling 1988; Karjalainen et al. 1990;
Parrish and Margraf 1990). The D. puntazzo diet
was made up of small crustaceans with relatively
hard chitin esoskeleton, and S. salpa gastric content was mainly composed of macro algae, with
Diel Feeding Features of Juveniles of Two Sparids
213
strong cellulose content. Nonetheless evacuation
rates reported here are very low when compared
to those of the juveniles of Mullus surmuletus in
the same area, who presented an evacuation rate
of 0.66 g DW h- 1 (Mazzola et al. 1999).
Daily food rations, calculated following
Pennington (1985) were 1.3% BDW for D. puntazzo and to 1.60/0 for S. salpa. These results are
lower than those reported by other authors, for
juveniles of different species but based on
Eggers' and Elliott and Persson's models
(Lagardere 1987; Sagar and Glova 1988;
Ruggerone 1989; Mazzola et al. 1999). So the differences observed might be due to the fact that
the Pennington method, based on square root
model. tends to underestimate food consumption, when compared with Eggers' (1979) and
Elliott and Persson's exponential models,
(Ruggerone 1989).
Acknowledgements. The authors are particularly indebted to
Dr. G. Sara (University of Palermo) for precious collaboration
during sampling. Thanks are due to Prof. R. Danovaro
(University of Ancona) and Dr. T. La Rosa (University of
Palermo) for suggestions and support during ms revision.
This work was supported by a grant of the Ministero
dell'Universita e Ricerca Scientifica e Tecnologica and the
Ministero per Ie Politiche Agricole, Italy.
References
Antolic B, Skaramuca B, Musin D, Sanko-Njire J (1994) Food and
feeding habits of a herbivore fish Sarpa salpa (L.) (Teleostei,
Sparidae) in the southern Adriatic (Croatia). Acta Adriat 35:
45-52
Arrhenius F, Hansson S (1994) In situ food consumption by
young-of-the-year Baltic Sea herring Clupea harengus: a test
of predictions from a bioenergetics model. Mar Bcol Prog
Ser 110: 145-149
Campolmi M (1998) Studio della comunita zooplanctonica di un
bassofondo costiero mediterraneo (Stagnone di Marsala,
Sicilia occidentale). Ph D thesis, Univ Messina.
Coull Be (l990) Are members of the meiofauna food for higher
trophic levels? Trans Am Microsc Soc 109(3): 233-246
Dos Santos J, Jobling M (1988) Gastric emptying in cod, Gadus
morhua L.: effects of food particle size and dietary energy
content. J Fish BioI 33: 511-516
Eggers DM (1979) Comments on some recent methods for estimating food consumption by fish. J Fish Res Board Can 36:
1018-1019
Harmelin-Vivien ML, Harmelin JG, Leboulleux V (1995)
Microhabitat requirements for settlement of juvenile sparid
fishes on Mediterranean rocky shores. In: Balvay G (ed)
Space partitionig within aquatic ecosystems, Hydrobiologia,
vol 300-301, pp 309-320
Hellawell JM, Abel R (1971) A rapid volumetric method for the
analysis of the food of fish. J Fish BioI 3: 29-37
Tabling M (1987) Influences offood particle size and dietary energy
content on pattern of gastric evacuation in fish: test of a physiological model of gastric emptying. J Fish BioI 30: 299-314
important food item in the diet of S. salpa juveniles. In particular, they fed on Rhodophycaea
(Laurencia sp. and Polisiphonia sp.), that have
been reported in this environment (Scilipoti
1998). Our results are in agreement with Antolic
et al. (1994) who found adults of S. salpa, in the
southern Adriatic Sea, feeding mainly on
Rhodophycaea and marine phanerogams.
Among other food items, only Ascidiacea larvae
and Hydrozoa provided an important contribution to the diet of this species.
Juveniles of D. puntazzo always presented a
niche breadth larger than that of S. salpa juveniles. In fact, their diet was composed of largely
diversified prey items, while macro algae represented the dominant fraction of gastric contents
of S. salpa juveniles. Niche overlap of the two
species at 4 pm is dearly due to the intensive
ingestion of Ascidiacea larvae by both D. puntazzo and S. salpa. As the availability of this item in
the environment was scarce, it hypothesised a
competition between the two species for this
kind of resource.
The unimodal trend in the daily feeding
rhythm of both species (without a real feeding
peak), indicates that they were continuously
feeding during the day, but not during the night.
This habit allows them to avoid competition for
food resources with other small-size residential
species. In fact, additional studies carried out in
the same area showed that residential species,
such as Pomatoschistus tortonesei, Aphanius fasciatus and Atherina boyeri, fed largely on same
resources (Copepoda, Amphipoda, Tanaidacea)
(Scilipoti et al. 1997; Scilipoti 1998). Yet, a comparison between diel feeding cycles of these
species suggests that there is a shift in feeding
times in order to reduce trophic competition.
Both D. puntazzo and S. salpa juveniles followed
a square root model of gastric evacuation with a
gastric evacuation rate of 0.011 and 0.014 g DW
h- 1 , respectively. These low rates of gastric evacuation may be due to a number of factors such as
their very small size. the scant amount of food
ingested, water temperature, and food quality. It
is well known that all these factors may influence
gastric evacuation rates (Tobling 1987; Dos
Santos and Jobling 1988; Karjalainen et al. 1990;
Parrish and Margraf 1990). The D. puntazzo diet
was made up of small crustaceans with relatively
hard chitin esoskeleton, and S. salpa gastric content was mainly composed of macro algae, with
Diel Feeding Features of Juveniles of Two Sparids
213
strong cellulose content. Nonetheless evacuation
rates reported here are very low when compared
to those of the juveniles of Mullus surmuletus in
the same area, who presented an evacuation rate
of 0.66 g DW h- 1 (Mazzola et al. 1999).
Daily food rations, calculated following
Pennington (1985) were 1.3% BDW for D. puntazzo and to 1.60/0 for S. salpa. These results are
lower than those reported by other authors, for
juveniles of different species but based on
Eggers' and Elliott and Persson's models
(Lagardere 1987; Sagar and Glova 1988;
Ruggerone 1989; Mazzola et al. 1999). So the differences observed might be due to the fact that
the Pennington method, based on square root
model. tends to underestimate food consumption, when compared with Eggers' (1979) and
Elliott and Persson's exponential models,
(Ruggerone 1989).
Acknowledgements. The authors are particularly indebted to
Dr. G. Sara (University of Palermo) for precious collaboration
during sampling. Thanks are due to Prof. R. Danovaro
(University of Ancona) and Dr. T. La Rosa (University of
Palermo) for suggestions and support during ms revision.
This work was supported by a grant of the Ministero
dell'Universita e Ricerca Scientifica e Tecnologica and the
Ministero per Ie Politiche Agricole, Italy.
References
Antolic B, Skaramuca B, Musin D, Sanko-Njire J (1994) Food and
feeding habits of a herbivore fish Sarpa salpa (L.) (Teleostei,
Sparidae) in the southern Adriatic (Croatia). Acta Adriat 35:
45-52
Arrhenius F, Hansson S (1994) In situ food consumption by
young-of-the-year Baltic Sea herring Clupea harengus: a test
of predictions from a bioenergetics model. Mar Bcol Prog
Ser 110: 145-149
Campolmi M (1998) Studio della comunita zooplanctonica di un
bassofondo costiero mediterraneo (Stagnone di Marsala,
Sicilia occidentale). Ph D thesis, Univ Messina.
Coull Be (l990) Are members of the meiofauna food for higher
trophic levels? Trans Am Microsc Soc 109(3): 233-246
Dos Santos J, Jobling M (1988) Gastric emptying in cod, Gadus
morhua L.: effects of food particle size and dietary energy
content. J Fish BioI 33: 511-516
Eggers DM (1979) Comments on some recent methods for estimating food consumption by fish. J Fish Res Board Can 36:
1018-1019
Harmelin-Vivien ML, Harmelin JG, Leboulleux V (1995)
Microhabitat requirements for settlement of juvenile sparid
fishes on Mediterranean rocky shores. In: Balvay G (ed)
Space partitionig within aquatic ecosystems, Hydrobiologia,
vol 300-301, pp 309-320
Hellawell JM, Abel R (1971) A rapid volumetric method for the
analysis of the food of fish. J Fish BioI 3: 29-37
Tabling M (1987) Influences offood particle size and dietary energy
content on pattern of gastric evacuation in fish: test of a physiological model of gastric emptying. J Fish BioI 30: 299-314