the epipelagic zone at night. The latter species
remains below 300 m where it feeds in the late
afternoon, maybe to reduce trophic competiton.
The S. diaphana, concentrated between 500 and
800 m, feeds on copepods, ostracods and
amphipods (small individuals). The young stages
of S. pseudobscura, occurring below 800 m, prefer
copepods, polychaetes and euphausiids, while
adults preferentially feed on amp hip ods and
fishes.
Sameoto (1988) demonstrated how
Benthosema glaciale, which dominates the
mesopelagic zone of Nova Scotian waters in the
North Atlantic selects certain species of copepods, but not the most abundant Calanus finmarchicu5, despite the fact that B. glaciale has a
feeding preference for prey species larger than 1
mm. During the day, the population is concentrated at a depth from 300 and 550 m. with a
maximum from 320-360 m. At night, the population moves below the main concentration of
copepods that occupy the upper 30 m. This
could either imply that the predator occurs
exactly in correspondence with the maximum
concentration of zooplankton, and feeds on it
there, or, that the predators remain below their
prey with only brief excursions into the upper
stratum to eat.
Goodyear et aI. (1972) studied the ecology
and distribution of mesopelagic fishes in the
Mediterranean Sea, sampling more than 20,000
specimens from 36 species of 10 different families. Mesopelagic fishes occurred in the upper
1000 m during the day, and were mainly sampled
between 100 and 1000 m. On the other hand, at
night they were captured between 0 and 1000 m,
with a maximum concentration between 0 and
100 m and 400 and 800 m. Depending on the size,
a vertical stratification depending on size was
evident for the majority of species, both during
the day and at night. The authors subdivided this
group into a broad scale, involving distinct and
widely separated depths, and a narrow scale,
involving continuous distributions usually of
limited depth.
Matallanas (1982) studied the diet of
Lampanyctus crocodilus collected in the western
Mediterranean between 300 and 700 m, concluding that the species exhibits a high coefficient of
fullness which indicates its voracity. The mean
number of prey per stomach was higher during
spring at the same time when euphausiids were
more abundant, while the size of the prey
Energy Flux in the South Tyrrhenian Deep-sea Ecosystem
201
increased proportionally to that of the predator.
The species feeds also on copepods, mysids.
amphipods, pelagic decapods and fishes
(Cyclothone braueri. L. crocodilus) without any
relation between trophism and daily vertical distribution.
The diet of Cyc1othone braueri collected
between 300 and 900 m in the Ligurian Sea
includes zooplankton organisms with wide vertical distribution ranges. The most important
groups are copepods (mainly Pleuromamma gracilis, Euchaeta marina, Chiridius poppei and
Calanus helgolandicus) and ostracods, followed
by larvae of euphausiids. amphipods and
decapods (Palma 1990).
The two most abundant myctophids in the
Straits of Messina. the lanternfishes Hygophum
benoiti and Myctophum punctatum (Scotto di
Carlo et al. 1982), were distributed at a depth
between 100 and 1000 m, with a maximum concentration between 700 and 1000 m. Dietary
variations were related to age. both as regards
size and taxonomic composition of the prey (Fig.
4), indicating differences in feeding habits
between the two species. The H. benoiti has a
trophic behaviour related to the different size
classes of prey. The young ate mainly copepods
whereas the prey diversity and biomass of the
other zooplanktonic taxa such as amphipods,
mysids and chaetognaths were greatest in the
stomachs of medium-sized individuals. On the
other hand, adults had a more euphausiid-based
diet. This model implies not only a greater efficiency in the capture of larger prey. but also
selective feeding during all stages of the life
cycle. Myctophum punctatum, instead, exhibited
a mixed diet during all the developmental stages.
with the exception of small individuals that fed
almost exclusively on copepods. Prey diversity
and biomass in the stomach contents generally
increased with size. Myctophum punctatum
became a more efficient and opportunistic
predator with age. This type of strategy, which
gradually adds a new type of prey to the diet as
the fish matures, is the most common for
mesopelagic fishes (Tyler and Pearcy 1975).
Myctophum punctatum was also the most active
predator. since it fed on a wide range of prey,
such as gasteropods, thaliaceans and appendicularians, which were absent in the diet of
Hygophum benoiti. The composition of the diet
of both species very much resembled a nocturnal zooplanktonic community composed of both
remains below 300 m where it feeds in the late
afternoon, maybe to reduce trophic competiton.
The S. diaphana, concentrated between 500 and
800 m, feeds on copepods, ostracods and
amphipods (small individuals). The young stages
of S. pseudobscura, occurring below 800 m, prefer
copepods, polychaetes and euphausiids, while
adults preferentially feed on amp hip ods and
fishes.
Sameoto (1988) demonstrated how
Benthosema glaciale, which dominates the
mesopelagic zone of Nova Scotian waters in the
North Atlantic selects certain species of copepods, but not the most abundant Calanus finmarchicu5, despite the fact that B. glaciale has a
feeding preference for prey species larger than 1
mm. During the day, the population is concentrated at a depth from 300 and 550 m. with a
maximum from 320-360 m. At night, the population moves below the main concentration of
copepods that occupy the upper 30 m. This
could either imply that the predator occurs
exactly in correspondence with the maximum
concentration of zooplankton, and feeds on it
there, or, that the predators remain below their
prey with only brief excursions into the upper
stratum to eat.
Goodyear et aI. (1972) studied the ecology
and distribution of mesopelagic fishes in the
Mediterranean Sea, sampling more than 20,000
specimens from 36 species of 10 different families. Mesopelagic fishes occurred in the upper
1000 m during the day, and were mainly sampled
between 100 and 1000 m. On the other hand, at
night they were captured between 0 and 1000 m,
with a maximum concentration between 0 and
100 m and 400 and 800 m. Depending on the size,
a vertical stratification depending on size was
evident for the majority of species, both during
the day and at night. The authors subdivided this
group into a broad scale, involving distinct and
widely separated depths, and a narrow scale,
involving continuous distributions usually of
limited depth.
Matallanas (1982) studied the diet of
Lampanyctus crocodilus collected in the western
Mediterranean between 300 and 700 m, concluding that the species exhibits a high coefficient of
fullness which indicates its voracity. The mean
number of prey per stomach was higher during
spring at the same time when euphausiids were
more abundant, while the size of the prey
Energy Flux in the South Tyrrhenian Deep-sea Ecosystem
201
increased proportionally to that of the predator.
The species feeds also on copepods, mysids.
amphipods, pelagic decapods and fishes
(Cyclothone braueri. L. crocodilus) without any
relation between trophism and daily vertical distribution.
The diet of Cyc1othone braueri collected
between 300 and 900 m in the Ligurian Sea
includes zooplankton organisms with wide vertical distribution ranges. The most important
groups are copepods (mainly Pleuromamma gracilis, Euchaeta marina, Chiridius poppei and
Calanus helgolandicus) and ostracods, followed
by larvae of euphausiids. amphipods and
decapods (Palma 1990).
The two most abundant myctophids in the
Straits of Messina. the lanternfishes Hygophum
benoiti and Myctophum punctatum (Scotto di
Carlo et al. 1982), were distributed at a depth
between 100 and 1000 m, with a maximum concentration between 700 and 1000 m. Dietary
variations were related to age. both as regards
size and taxonomic composition of the prey (Fig.
4), indicating differences in feeding habits
between the two species. The H. benoiti has a
trophic behaviour related to the different size
classes of prey. The young ate mainly copepods
whereas the prey diversity and biomass of the
other zooplanktonic taxa such as amphipods,
mysids and chaetognaths were greatest in the
stomachs of medium-sized individuals. On the
other hand, adults had a more euphausiid-based
diet. This model implies not only a greater efficiency in the capture of larger prey. but also
selective feeding during all stages of the life
cycle. Myctophum punctatum, instead, exhibited
a mixed diet during all the developmental stages.
with the exception of small individuals that fed
almost exclusively on copepods. Prey diversity
and biomass in the stomach contents generally
increased with size. Myctophum punctatum
became a more efficient and opportunistic
predator with age. This type of strategy, which
gradually adds a new type of prey to the diet as
the fish matures, is the most common for
mesopelagic fishes (Tyler and Pearcy 1975).
Myctophum punctatum was also the most active
predator. since it fed on a wide range of prey,
such as gasteropods, thaliaceans and appendicularians, which were absent in the diet of
Hygophum benoiti. The composition of the diet
of both species very much resembled a nocturnal zooplanktonic community composed of both