Abundances of demersal sharks and chimaera from 1994-2009 scientific surveys in the central Mediterranean sea

Bibliographic and data gathered in scientific bottom trawl surveys carried out off the Southern Coasts of Sicily (Mediterranean Sea), from 1994 to 2009 and between a depth of 10 and 800 m, were analysed in order to prepare a checklist of demersal sharks and chimaera, which are species sensitive to fisheries exploitation. Out of the 27 previously reported demersal shark and chimaera taxa in the Mediterranean, only 23 were found in literature and 20 sampled during the surveys in the investigated area. Among the species sampled in the surveys, only 2 ubiquitous (Squalus blainville and Scyliorhinus canicula) and 3 deep-water (Chimaera monstrosa, Centrophorus granulosus and Galeus melastomus) species showed a wide geographical distribution with a consistent abundance. Excluding the rare (such as Oxynotus centrina) or uncommon shark (e.g. Squalus acanthias), the estimated frequencies of occurrence and abundance indexes show a possible risk of local extinction for the almost exclusively (e.g. angelshark, Squatina spp.) or preferential (e.g. Scyliorhinus stellaris) neritic species.peer-reviewe

Size and age at onset of sexual maturity of female Norway lobster Nephrops norvegicus L. (Crustacea: Nephropidae) in the Strait of Sicily (Central Mediterranean Sea)

The reproductive cycle of the Norway lobster (Nephrops norvegicus) female was investigated to determine the size and age at onset of sexual maturity (SOM), as a baseline to establish the minimum catchable size. Samples were gathered in four seasonal (Spring 1986 - Winter 1987) trawl surveys on the Italian side of the Strait of Sicily (Central Mediterranean Sea). The relative frequency of females in different stages of maturation and in berried conditions was observed. According to the ovary stages, gonadal maturation is attained during Spring and Summer; berried animals occur almost exclusively in Summer and Autumn, in about 40% of the sample. Length structure changes slightly by location and by season; recruitment to the gear occurs more or less continuously. Gaussian components appear to be highly overlapped; the resolution of the length frequency distribution values leads to the identification of multiple cohorts, five of which were well represented. The population attains 50% of maturity at 30-32 mm CL, corresponding to an age of 5 years. The mean size of the first Gaussian component from the catch (about 22 mm CL) is well below the estimated size at 50% maturity, suggesting a precocious recruitment to the fishery.No disponibl

A Tale on the Demersal and Bottom Dwelling Chondrichthyes in the South of Sicily through 20 Years of Scientific Survey

In the present work, an overview of the demersal (sharks‐chimaera) and bottom dwelling (batoids) of experimental survey international bottom trawl survey in the mediterranean (MEDITS) data, from 1994 to 2013, is provided. The analysed data refer to a wide area located off the southern coast of Sicily, namely south of Sicily (according to the general fisheries commission for the mediterranean (GFCM) classification, Geographical Sub‐Area 16). A checklist of the recorded Chondrichthyes was integrated by density index, D.I. (N/Km2) and average individual weight (as the ratio between biomass index, D.I. (N/Km2) and D.I.). Results suggest that most of the Chondrichthyes in South of Sicily are in a steady state, although in the last few years, they seemed to recover. The spatial distribution of sharks‐chimaera in the geographical sub‐area (GSA) 16 is mainly concentrated in the southern and north‐western zones. Nevertheless, possible management actions to promote the recovering of these very important ecological and threatened species are discussed

Kolebanja nekih indeksa rasta gospodarskih iskorištavanog sredozemnog oslića

In this paper, some life‑history estimates concerning the females of the Mediterranean hake Merluccius merluccius (L., 1758), i.e. the parameters of the von Bertalanffy growth function (L∞, K, and t0), the maximum-ever lengths (Lmax-e), and the lengths at full maturity (Lmst) were gathered from the pertinent literature and used to derive 5 growth performance indexes (K, φ’, RL=Lmst/ L∞, t50% and ω). The original datasets (n= 70) and the corresponding growth performance indexes were organized and analyzed by various geographical units (GFCM’s geographical sub‑area, GSA; GFCM’s statistical division, GD; and biological province, BP). The parameter distribution resulted to be normal only for the growth performance indexes K and RL; a significant relationship correlation was detected between K and t50%, between φ’ and ω, and between K and ω. The examination of the available historical data showed a scattered and unbalanced geographical distribution by GSA (e.g. 13 of 20 GSAs had less than 5 datasets each), a variability which was higher intra‑GSA than inter‑GSAs (as evidenced by the box‑plots) and no clear geographical trend. GD and BP presented similar patterns, with significant geographical effects only in the RL. Present results suggest that, even if geographical effects are expected, they are obscured by the uncertainty of the original parameters, especially those related to the von Bertalanffy growth function (vBGF). Consequently, growth performance indexes should be used (and interpreted) with caution.U ovom radu, iznesene su neke procjene rasta koji se odnosi na ženke sredozemnog oslića (Merluccius merluccius L., 1758) tj. parametara rasta von Bertalanffy-eve jednadžbe rasta (L∞, K, i t0), maksimalna dužina ikad postignuta (Lmx-e), te dužina u punoj zrelosti (Lmst), a koji su prikupljeni iz literature i korišteni za dobivanje 5 različitih indeksa rasta (K, φ’, RL=Lmst/L∞, t50% i ω). Originalni setovi (n = 70) i odgovarajući indeksi rasta su organizirani / sistematizirani i analizirani prema različitim geografskim jedinicama (GFCM-a zemljopisno podpodručje, GSA, GFCM-a statistička podjela, GD, te biološka pokrajina, BP). Parametar raspodjele rezultirao je normalno samo za izvedbe rasta indeksa K i RL; značajna korelacija povezanosti je utvrđena između K i t50%,, između φ ‘i ω, te između K i ω. Pregled dostupnih povijesnih podataka pokazao je raspršenu i neujednačenu geografsku raspodjelu po GSA (npr. 13 preko 20 GSAs imali su manje od 5 skupova podataka svaki), više varijabilnosti unutar GSA od međudjelovanja GSAs (o čemu svjedoči okvir box-plotova) i nejasan geografski trend. GD i BP prikazuju slične obrasce, sa značajnim geografskim učincima samo u RL. Trenutni rezultati pokazuju da, čak i ako su geografski učinci očekivani, oni su prikriveni nesigurnošću izvornih parametara, posebno onih koje se odnose na rast prikazan von Bertalanffy-evom funkcijom (vBGF), pa stoga performanse rasta indeksa treba koristiti (i interpretirati) s oprezom

Differences in demersal community structure and biomass size spectra within and outside the Maltese Fishery Management Zone (FMZ)

We examined the protection effect of a long-established fisheries protection zone by studying the demersal communities and the biomass size spectra of specific taxonomic groups. The results and the relevant management implications of the community analysis are discussed within the context of the MEDITS trawl survey program, from which the data was derived. The demersal fishery resources on the muddy bottoms of Maltese trawling grounds were found to be stratified in four main depth ranges: 83 to 166 m (outer continental shelf), 140 to 230 m (shelf break), 270 to 440 m (shallow slope), and 466 to 701 m (deep slope). Significant differences were detected between the inside and outside zones of the outer continental shelf. Stations from this stratum inside the protected zone had twice as much biomass as those outside as well as larger individuals of some species (e.g. elasmobranchs). The depth strata identified do not coincide with those sampled in existing trawl survey programmes in the Sicilian Channel, which were set up without reference to demersal assemblage structure and its relation to depth. It is therefore clear that characterisation of the biotic assemblages is important in order to obtain a better sampling representation of each depth-stratum/assemblage type, and this should be considered in the survey design.peer-reviewe

MEDITS-based information on the deep water red shrimps Aristaeomorpha foliacea and Aristeus antennatus (Crustacea: Decapoda: Aristeidae)

Special Volume: Mediterranean marine demersal resources: the Medits international trawl survey (1994-1999)The application of statistical models on a time series of data arising from the MEDITS International Trawl Survey, an experimental demersal resources survey carried out during six years (1994-1999) in the same season of the year (late spring - early summer) using the same fishing gear in a large part of the Mediterranean, has allowed for a study to compare, for the first time, the space-time distribution, abundance, and size structure of the two Aristeids Aristaeomorpha foliacea and Aristeus antennatus throughout most of the Mediterranean Sea. This research has shown a large variability among the six reference areas, that were arbitrarily defined within the basin. In particular the two shrimps do not seem to present any correlation or yield continuity in the years. The same lack of homogeneity was also observed in the time trend of the abundances and frequencies of each of the two species. These data seem to confirm the intrinsic variability of the species, the cause of which is still unknown and undocumented. Nevertheless, a longitudinal gradient of catches has been observed where A. antennatus is more abundant in the west and A. foliacea in the east of the basinVersión del editor1,006

Piano di Lavoro Nazionale Raccolta Dati Alieutici 2017-2019 Rapporto tecnico annuale

Campionamento biologico delle specie demersali e dei piccoli pelagici (GSA16

The Mediterranean Teuthofauna: towards a biogeographical coverage by regional census. 2: Strait of Sicily

Volume: 30Start Page: 161End Page: 17

The Mediterranean Teuthofauna: towards a biogeographical coverage by regional census. 2: Strait of Sicily

Volume: 30Start Page: 161End Page: 17