Nicola Ungaro

Long-term changes in demersal resources of the Adriatic Sea: comparison between trawl surveys carried out in 1948 and 1998

Abstract Trawl surveys carried out in the Adriatic Sea in 1948 and 1998 provided information on the changes that occurred in the composition and distribution of demersal fish resources over the 50 years period. The main change was the decrease of elasmobranchs diversity and frequency, mostly referring to the Hypotremata group. Life history parameters appeared to be determining factors, since small sized species such as the smallspotted catshark ( S. canicula ) or the brown ray ( R. miraletus ) were frequently collected in both surveys, while bigger shark species and most other rays disappeared or were rarely found during the 1998 survey. Regarding bony fishes, common species were collected with similar frequency in both surveys; some fishery target species (e.g. the hake) have similar percentage values (biomass) in both surveys, while others (the silver scabbardfish) have increased values, and some (mainly small sized species such as red mullet) replace elasmobranchs at the top of the catches. Despite the low number of observations (two surveys only) and some sampling differences, the data provide an interesting long-term comparison.

Rapid miocene-pliocene dispersal and evolution of Mediterranean rajid fauna as inferred by mitochondrial gene variation.

Rajidae (colloquially known as skates and rays) experienced multiple and parallel adaptive radiations allowing high species diversity and great differences of species composition between regional faunas. Nevertheless, they show considerable conservation of bio‐ecological, morphological and reproductive traits. The evolutionary history and dispersal of North‐east Atlantic and Mediterranean rajid fauna were investigated throughout the sequence analysis of the control region and 16S rDNA mitochondrial genes. Molecular estimates of divergence times indicated recent origin and rapid dispersal of the present species. Compared with the ancient origin of the family (Late Cretaceous), the present species diversity arose in a relatively narrow time‐window (12 Myr) from Middle Miocene to Early Pleistocene, likely by speciation processes related to dramatic geological and climatic events in the Mediterranean. Nucleotide substitution rates and phylogenetic relationships indicated Mediterranean endemic skates derived from sister species with wider distribution during Late Pliocene–Pleistocene. Skate phylogeny and systematics obtained using mitochondrial gene variation were largely consistent with those based on morpho‐anatomical data.

Microsatellite DNA variation reveals high gene flow and panmictic populations in the Adriatic shared stocks of the European squid and cuttlefish (Cephalopoda)

In the semienclosed Adriatic Sea, the shared stocks of the cephalopods Loligo vulgaris and Sepia officinalis represent important marine fisheries resources exploited by all coastal countries. The improving of knowledge on the demographic features of these shared stocks is internationally relevant for adopting responsible management and conservation of these marine resources. Analyses of microsatellite variation in geographical samples collected from all parts of the Adriatic Sea were performed using arrays of species-specific di-nucleotide and tri-nucleotide loci. In L. vulgaris the level of genetic variability was consistent with that observed in other loliginid species, whereas the S. officinalis stock showed a microsatellite variation markedly lower than that estimated for the Atlantic and Mediterranean populations collected around the Iberian peninsula. The weak spatial genetic differentiation, the discordant results of the genetic divergence estimators and the lack of any geographical cline in the spatial genetic differences suggest the occurrence of single genetically homogeneous populations within the Adriatic stocks of both species, recommending a coordinated management of the squid and cuttlefish by the Adriatic fishing countries. On the contrary, significant differences detected in temporal replicates of S. officinalis might suggest that allelic frequency can change relating to reproductive behaviour.

Development of molecular and morphological markers to improve species-specific monitoring and systematics of Northeast Atlantic and Mediterranean skates (Rajiformes)

The Northeast Atlantic and Mediterranean skates (Rajidae) showed remarkable species diversity but with high morphological and ecological conservatism. Since skates are particularly vulnerable to the bottom trawl fishery, species-specific demographic surveys as well as studies defining life history and evolutionary traits are important in prioritising conservation programs. However, the identification of juveniles and adults of some species may be difficult using referenced guidelines and identification keys. Therefore, we attempt to develop markers for species identification through the parallel analysis of a 16S rDNA gene sequence and of several morphological characters on 135 individuals collected by trawl surveys in the Adriatic Sea and putatively assigned to six taxa. Species-specific haplotypes were defined for Raja miraletus, Raja montagui, Dipturus oxyrinchus, since a solid accordance between species boundaries and well-differentiated haplotypes was observed. Comparative analysis of 16S rDNA sequences allowed the identification of three juvenile specimens of Leucoraja circularis, a species that rarely occurs in the Adriatic Sea. On the contrary, morphological traits and haplotype distribution were largely discordant in Raja asterias and R. clavata. While all putative R. clavata individuals showed a unique haplotype (H-CLA), only 8 of 30 putative R. asterias individuals possessed a second weakly divergent haplotype (H-AST). The remaining 22 R. asterias carried the H-CLA. The multivariate analyses of morphometric and meristic characters in putative R. clavata and R. asterias revealed the clustering of individuals regardless of haplotypes. However, a bimodal distribution of R. asterias and R. clavata samples would suggest that two separated taxa might exist, both sharing the two 16S rDNA haplotypes. The haplotype distribution appeared to be significantly correlated only to the standardised disc length/total length (DL/TL) variation. Three alternative explanations may support this scenario: (i) an incomplete lineage sorting process in two morphologically yet distinct taxa; (ii) a recent hybridisation between the two taxa; (iii) the two taxa are morphologically plastic species and all considered morphological characters may be misleading in discriminating between them at all maturity stages, except for the DL/TL. However, further analyses on larger data sets and using molecular key markers (i.e. nuclear genes) will be needed to definitely resolve the status of these taxa. Molecular relationships among rajid taxa are largely consistent with systematics based on internal and external anatomical features. This multidisciplinary study contributed to defining the pattern of species diversity and abundance of rajids in the Adriatic Sea.

COMPOSITION AND DISTRIBUTION OF THE CEPHALOPOD FAUNA IN THE EASTERN ADRIATIC AND EASTERN IONIAN SEA

the composition and spatial distribution of cephalopods in the eastern Adriatic and the eastern Ionian Sea were analyzed based on the samples collected during the trawling campaigns performed in 1996, 1997, 1998, and 2000 in the framework of the MEDItS Project “International bottom trawl Survey in the Mediterranean Sea”. cephalopod samples were collected with a bot- tom trawl net, at sea depths ranging between 21 and 800 meters. A total of 32 species was registered, out of which 26 were found in the northern and central eastern Adriatic, 21 in the south eastern Adriatic region, and 26 in the eastern Ionian area. Results of the multivariate analysis revealed the existence of three main species assemblages related to the depth gradient, with minor differences between regions. Eledone moschata, Loligo vulgaris, and Alloteuthis media had the highest biomass percentage in the assemblage related to the upper continental shelf. the assemblage observed on the middle slope of the south eastern Adriatic was charact...

A “Traffic” Light approach for the assessment of the Broadtail shortfin squid Illex coindetii Verany, 1839 in the Southern Adriatic Sea (Central Mediterranean)

A multi-indicator system and the Traffic Light methodology (TL) to provide the first description of the Illex coindetii (Verany 1839) stock in the GFCM geographical sub-area (GSA) 18 (southern Adriatic Sea; Central Mediterranean) were applied using independent fishery data (“Mediterranean Bottom Trawl Survey”, “Medits”, programme, years 1996–2004). The trajectories of nine population indicators of Frequency of Occurrence (F), Biomass (BI), Density (DI), Recruit Strength (RS), Spawner Strength (SS), Mean Body Weight (MBW), Mantle Length (ML), Mantle Length Excluding Recruits fraction (MLER), Mean mantle Length-Females Length at maturity ratio (MLLm), were analysed using statistical estimators as arithmetic and geometric mean, median, and 75th percentile. The TL methodology was applied to analyse the resulting multiple-indicator panel. Results describe a significant trend of the I. coindetii stock (in number) in the GSA 18 related to a shift within its structure due to a greater proportion of small specimens in the population. Factors that may be contributing to the observed changes are sea temperature, the reduction of possible predators, the recovery of some prey species mostly due to the fishing pressure occurring in the area, and the fast growth and short life span of I. coindetii. In a dynamic system like the Adriatic Sea, the capability to respond quickly to the “environmental” or “ecosystem” changes seem to give I. coindetii an advantage in competition with the long lived finfish species. Accordingly, there is potential to use squid population dynamics as recorders to track environmental and ecological changes, as well as overexploitation. The adopted methodology drew attention to changes occurring within the stock of I. coindetii, and could provide an opportunity for managers to consider action at an early stage. The multi-indicator system and the TL methodology are illustrated as means to follow dynamic changes within squid stock, and to provide useful information for the assessment of the resource.

Demersal fish assemblage biodiversity as an index of fishery resources exploitation

Abstract Until 1996, scientific information about groundfish assemblages on southern Adriatic trawlable bottoms almost exclusively referred to the western side of the same basin (Italian waters). During 1996, for the first time, a summer trawl survey was carried out along the full South Adriatic area. A total of 93 demersal fish species was obtained and the ‘species abundance (biomass)/sam‐pling stations’ matrix was analysed by means of cluster analysis. The analysis was useful to discriminate the shelf and slope assemblages on both sides of the South Adriatic and to compare biodiversity. This was determined with univariate ecological indices (diversity, equitability) and graphical methods (ordinary, cumulative, and partial dominance; abundance/biomass comparison curves). Fish assemblage biodiversity was higher on shelf bottoms of the eastern Adriatic side (Albanian waters) than the western shore (Italian waters). The highest catch yields, referring to the main “target”; trawl fishery species, were usuall...

Notes on ichthyofauna of the deep basin of the Southern Adriatic Sea

Abstract Thirteen teleosts and four cartilaginous fishes occurred in bottom trawls from the 826–1196 m depth zone of the Southern Adriatic Sea. Cataetyx alleni (Byrne, 1906), Caelorinchus occa (Goode & Bean, 1886) and Lepidion lepidion (Risso, 1810) were recorded for the first time in this area, and all occurred deeper than 1000 m depth. The families Macrouridae, Moridae, and Squalidae dominated the catches below 1000 m depth, contributing 90 % in terms of weight and 91 % in terms of numbers.