PRELIMINARY DATA ON THE BIOLOGY OF ALEPOCEPHALUS ROSTRATUSRISSO, 1820
IN THE CENTRAL-WESTERN MEDITERRANEAN
Follesa M.C.*, Cabiddu S., Pesci P., Sabatini A., Cau A.
Department of Animal Biology and Ecology, University of Cagliari, Italy - * follesac@unica.it
Abstract
This note deals with 107 specimens of Alepocephalus rostratuscaught in the Sardinian Channel at depths between 950 and 1190 m. Its
frequency of numerical abundance increased with depth. The standard length (SL) of the specimens caught ranged between 13 and 45 cm
for females and 13 and 36 cm for males. The length-weight relationship was TW=0.0063SL
3.113
for sexes combined. The main prey
identified in the stomachs were the tunicate Pyrosoma atlanticumas well as crustaceans.
Key words: deep sea fish; Alepocephalus rostratus; Mediterranean Sea
Rapp. Comm. int. Mer Médit., 37,2004
357
Introduction
Alepocephalus rostratus Risso, 1820, the only known
representative of the family Alepocephalidae in the Mediterranean
Sea (1), occupies a dominant position among the typical bathyal
species and its biology has been studied mainly in the Catalan Sea
(NW Mediterranean) (2-3). In this note we present preliminary data
on its biology based on specimens caught in the Sardinian Channel
(central-western Mediterranean).
Materials and methods
Samples were collected from 12 experimental trawl hauls (mesh
size 40 mm, stretched) carried out in the Sardinian Channel at depths
between 800 and 1200 m (4 at a mean depth of 800 m, 4 at 1000 m,
and 4 at 1200 m) during summer 2003. A total of 107 specimens were
caught, which were measured for standard length (SL, cm), weighed
(total weight, TW, g), sex was identified and state of gonad was
determined microscopically. The length-weight relationship was
estimated for sexes combined. Finally, a preliminary analysis of
stomach contents was done for 55 specimens, with prey identified to
the lowest taxonomic level.
Results
A. rostratuswas caught at depths between 950 and 1190 m. The
number of specimens caught was zero between 800 and 900 m and
gradually increased with depth, making up 6% in 900-1000 m and
11% in 1100-1200 m. In the Sardinian Sea it was found at depths
between 550-780 m (4) as in the remaining part of the western
Mediterranean (5).
Of the 107 specimens caught 62 were females, 30 males whereas
sex was not determined for 15 individuals. Their SL ranged between
13 and 45 cm for females, 13 and 36 cm for males and 13-18 cm for
indeterminate specimens. The sex ratio (F:M) was 2.06 in favour of
females.
The length-weight relationship was TW=0.0063SL
3.113
for sexes
combined (N=104; R
2
=0.95; SE
b
=0.64), indicating positive
allometry.
The analysis of the stomach contents of 55 individuals indicated a
large number of empty stomachs (41 out of 55). The diet was
dominated by the tunicate Pyrosoma atlanticum (N%=81%),
crustaceans (N%=16%) and, to a lesser extent, cephalopods
(N%=3%). The diet composition was similar to that reported from the
Catalan Sea (1).
References
1-Markle D.F., and Quero J.-C., 1984. Alepocephalidae. Pp. 228-253. In:
P.J.P Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen and E. Tortonese
(eds.), Fishes of the North-eastern Atlantic and the Mediterranean.
UNESCO, Paris,Vol.1.
2-Stefanescu C., Lloris D., and Rucabado J., 1992. Depth size trends in
western Mediterranean demersal deep-sea fishes. Mar. Ecol. Prog. Ser.,
81: 205-213.
3-Carasson M., and Matallanas J., 1990. Preliminary data about the
feeding habits of some deepsea Mediterranean fishes. J. Fish Biol.,36:
461-463.
4-Cau A., 1980. Secondo contributo alla conoscenza dell’ittiofauna dei
mari circostanti la Sardegna meridionale (Osteichthyes). Quad. Civ. Staz.
Idrobiol. Milano,8: 39-43.
5-Raimbault R., 1963. Notes sur certaines espèces ichthyologiques
capturées au cours des campagnes de l’Institut des Pêches en Méditerranée
(1957-1961). Rév. Trav. Inst. Pêches Marit., 27 (1).
