Aa Pendugiu

Genetic characterization and artificial reproduction attempt of endemic Sardinian trout Salmo trutta L., 1758 (Osteichthyes, Salmonidae): Experiences in captivity

Abstract Native species of Sardinian brown trout (Salmo trutta) have declined drastically because of the introduction of non-native salmonids, overharvesting, and habitat degradation. One approach to conservation of declining species is to establish new populations through repopulation with genetically certified fish. In this study, samples of brown trout from seven rivers in Sardinia were analysed to look for the presence of pure individuals of the endemic Sardinian trout. Analyses of the mitochondrial DNA control region and the LDH-C1* gene revealed the presence of non-endemic and hybrid individuals in four of the seven rivers analysed. In addition, we reared a stock of native Sardinian trout at the experimental fish farm of Sadali and had them reproduce artificially. This experiment provided more knowledge about the incubation phase, hatching, reabsorption of the vitelline sac and the initial phases of growth, which can be used to develop more optimal management of this resource.

Assemblages in a submarine canyon: influence of depth and time

In this work we have studied the assemblages from Quirra canyon (Sardinia). We analysed data from 25 trawl samples from the canyon, made at different times and depth. A total of 71 demersal species (38 teleosts, 5 cartilaginous fishes, 13 molluscs and 15 crustaceans) were examined. We found four groups using cluster analysis; each group is characterised by a certain depth or time. In particular we have shown that the time of the day appears to have a role in the movement of shrimps and other species. This phenomenon seems to be linked to trophic need and by the consequent different food availability into the Canyon.

Demersal assemblages in two trawl fishing lanes located on the Baronie Seamount (Central Western Mediterranean)

This work focuses on the species associations of the Baronie Seamount (north-eastern Sardinia, Italy), according to variations in depth and time of day. The aim was to highlight the potential vertical movements of the species and to compare these results to existing data from a submarine canyon. Twenty-two samples were taken at different depths and times along two trawl lines over the seamount. A total of 94 species were caught; among these, 4 8 bony fish, 9 cartilaginous fish, 13 molluscs and 24 crustaceans were selected for analysis. Cluster analysis showed 3 groups in which both depth and time of day play an important role in grouping. Nine species showed some daily and nocturnal movement, probably linked to trophic requirements. The daily movements according to size and sex of the shrimps Aristaeomorpha foliacea and Aristeus antennatus were also studied. For these two populations, the analysis showed an uneven distribution and the diel cycle appears to involve only the females. These species seem to adapt their life cycle to the geomorphology of the sea bottom. The diurnal movements from the base of the seamount to the edge of the continental shelf increase the range of the species distribution. In fact, the seamount, due to its geomorphological conformation, offers these species the opportunity to very quickly span a considerable range of depths. These movements are known to occur in the continental shelf and slope, but in the seamount they are broadened and can be studied more easily.

Morphological description and intraspecific variability of Mullus surmuletus (Teleostea, Mullidae) vertebral column

Morphological aspects of the vertebral column of Mullus surmuletus from the Sardinian Channel are highlighted. The total number of vertebrae proved to be constant (24) in all examined individuals and the most correct morphological subdivision appears to be into three regions (abdominal, caudal, and intermediate). A difference in the number of abdominal and intermediate vertebrae can be noted: respectively, 7+3 in 39% of individuals and 6+4 in the remaining 61%. The number of caudal vertebrae, however, is always constant (14). These differences were not influenced by size or sex. The present paper shows the first observations of variability, independently of depth or latitude, in the vertebral column of a species with subcarangiform swimming. Since variations in the vertebral composition are determined in the very early stages of ontogenesis, the observed differences might be caused by groups of individuals born in different periods of the same year, in which there could be differences in environmental parameters sufficient to determine variations in the vertebral morphology, but not in the number of vertebrae.