RESUMEN

The class Chondrichthyes (sharks, rays and chimeras) is one of the three lineages of fishes and the most evolutionary distinct radiation of vertebrates [...].

RESUMEN

Effectiveness of restocking programs in Marine Fully Protected Areas' (FPAs) can be highly affected by the movement behavior of the species to protect. We analyzed the data of 744 Palinurus elephas specimens tagged, relocated inside 12 FPAs, established in the seas surrounding Sardinia (central-western Mediterranean), and then recaptured. The overall aims were to characterize the individuals' movements after the relocation and to discuss strengths and weaknesses of the current FPAs' design. Almost 80% of tagged individuals travelled progressively increasing distances, as a function of the release distance, up to a maximum value of 11,500 m. Then, for larger release distances, individuals' mobility appeared reduced and more chaotic. A similar trend was found analyzing the distances travelled with respect to the FPAs with the highest number of recaptured individuals and to the size. These results allow to establish a threshold limit of the release distance, to take into account when designing FPAs, as a useful tool to keep a portion of the individuals into FPAs' borders, in order to both preserve the species and guarantee a spillover of individuals in the commercial areas.

Asunto(s)

RESUMEN

In 1990s, the European spiny lobster Palinurus elephas, one of the most commercially important species in the Mediterranean, exhibited a population decline. For this reason, fully protected areas (FPAs) appeared effective in re-establishing natural populations and supporting fishery-management objectives. Here, the reproductive parameters of P. elephas populations in two different FPAs (Su Pallosu and Buggerru, central-western Mediterranean), where a restocking programme was carried out, and in their surrounding commercial zones, were investigated from quantitative and qualitative perspectives. The comparison of fecundity between females collected inside and outside FPAs did not show statistical differences as well as the vitellogenin concentration, which did not vary among eggs of different size classes of females caught inside and outside the FPAs, indicating the same reproductive potential. The study demonstrated a benefit of overexploited populations in terms of enhancement of egg production overtime (15 years for Su Pallosu and 6 years for Buggerru) with a mean egg production 4.25-5.5 times higher at the end of the study than that observed at the beginning of the study. The main driver of eggs production appeared to be size, with larger lobsters more present inside the FPAs than outside. Given these results, the dominant contribution of the two studied FPAs to the regional lobster reproduction is remarkable.

RESUMEN

Oviducal glands (OGs) are distinct expanded regions of the anterior portion of the oviduct, commonly found in chondrichthyans, which play a key role in the production of the egg in-vestments and in the female sperm storage (FSS). The FSS phenomenon has implications for understanding the reproductive ecology and management of exploited populations, but little information is available on its taxonomic extent. For the first time, mature OGs from three lecithotrophic oviparous and four yolk-sac viviparous species, all considered at risk from the fishing impacts in the central western Mediterranean Sea, were examined using light microscopy. The OG microanatomy, whose morphology is generally conserved in all species, shows differences within the two reproductive modalities. Oviparous species show a more developed baffle zone in respect to viviparous ones because of the production of different egg envelopes produced. Among oviparous species, Raja polystigma and Chimaera monstrosa show presence of sperm, but not sperm storage as observed, instead, in Galeus melastomus and in all the viviparous sharks, which preserve sperm inside of specialized structures in the terminal zone.

RESUMEN

Cartilaginous fish are commonly recognized as key species in marine ecosystems for their fundamental ecological role as top predators. Nevertheless, effective management plans for cartilaginous fish are still missing, due to the lack of knowledge on their abundance, distribution or even life-history. In this regard, this paper aims at providing new information on the life-history traits, such as age, maturity, reproductive period, in addition to diet characteristics of eleven rare cartilaginous fish inhabiting the Central-Western Mediterranean Sea belonging to the orders Chimaeriformes (Chimaera monstrosa), Hexanchiformes (Heptranchias perlo and Hexanchus griseus), Myliobatiformes (Aetomylaeus bovinus and Myliobatis aquila), Rajiformes (Dipturus nidarosiensis and Leucoraja circularis), Squaliformes (Centrophorus uyato, Dalatias licha and Oxynotus centrina) and Torpediniformes (Tetronarce nobiliana), useful for their assessment and for future management actions. Particularly, the present paper provides for the first time the age estimation of D. nidarosienis and L. circularis which were both found capable of becoming older than ten years. In addition, the present study updates the sizes of first maturity of C. uyato and D. licha, which appeared to be capable of reproducing earlier than what was previously hypothesized, representing very valuable information for a better understanding of these rare species populations status and, eventually, their conservation. On the basis of the stomach content analysis, it was possible to identify five different predator groups.

RESUMEN

Despite being commonly recognized by the general public, knowledge about the biology and life-history of electric rays is still scarce. Globally, according to the International Union for Conservation of Nature, more of the 80% of the species belonging to the Torpedinidae family are, indeed, classified as Data Deficient, so as, in most of the cases, no proper management measures are available for the conservation of these species. For this reason, the main goal of this study is to provide new information on life-history traits of three species inhabiting the Mediterranean Sea. Age and growth were estimated through direct annuli count of 146 vertebral centra sections of Torpedo marmorata. Females' growth pattern was found to be better described by a S-shaped function (Gompertz L∞ = 622mm TL; k = 0.15; IP=2.75 years), while males' by a logarithmic one (von Bertalanffy L∞ = 485mm TL; k = 0.14; t0 = -2.28). The oldest female and male were aged 17 (560mm TL) and 11 (432mm TL), respectively. Females (L50=379mm TL and A50=5.5 years) appeared to mature later than males (L50=272mm TL and A50=3.8 years), also attaining bigger sizes. Despite the observation of late-pregnant females being found only in autumn and regressing ones in autumn and winter, the presence of juveniles during the whole year may indicate a longer reproductive period. The stomach content analysis identified T. marmorata as a top predator (TROPH=4.38) with a very narrow trophic niche (Bi=0.22), extremely specialized in feeding on bony fishes. In addition, this work provides new and updated information on T. torpedo and the rare Tetronarce nobiliana growth, reproductive features and diet. Therefore, offering new essential data to assess the population conditions of all Torpedinidae species that inhabit the Mediterranean Sea, will lead to effective conservation plans.

Asunto(s)

RESUMEN

As far as is known, in this paper the first case of lacking of skin-related structures (epidermis, stratum laxum, dermal denticles and teeth) in a free-swimming elasmobranch, the blackmouth catshark, Galeus melastomus, is reported. The individual was caught by trawl in Sardinian waters (central-western Mediterranean) in July 2019 at a depth of 500 m. Although this kind of morphological abnormality is potentially fatal, the observations suggested that the specimen was in good health and well developed.

Asunto(s)