Search

Eye lens of 196 Loligo vulgaris and 205 Loligo forbesii collected by trawl surveys from 2013 to 2015 in Sardinian waters (Mediterranean Sea) were analysed for age determination. In an alternative to the technique previously used in Sepia officinalis and Enteroctopus megalocyatus, in this study, we proposed the elimination of decalcification and dehydration steps to reduce the time of lens processing. In addition, lenses were included in epoxy resin, which was then subject to lapping, to ensure clear reading and counting of the increments. The number of increments counted in L. vulgaris (59–520) and in L. forbesii (51–543) was strongly related to mantle length and weight of the animals, with no statistical differences between the sexes. Assuming daily growth increments, L. vulgaris was estimated to have a life span of 17 months for males and 14 months for females, while L. forbesii males had an estimated life span of 18 and 16.5 months for females. The exponential model was the best fit for growth data for both species and sexes, showing higher growth for males in comparison with females. These results preliminarily indicate that the eye lens is a valid tool for age determination of the two Loliginidae species, but it would benefit from validation by additional studies. [ABSTRACT FROM AUTHOR]

T-bar anchor tags and Petersen discs were used during a preliminary mark–recapture experiment in the wild on 268 Octopus vulgaris. Discs, despite causing some injuries, were characterized by a quicker healing (within 5 days) and a higher retention rate than T-bar tags (about 97% versus 22%, respectively), therefore they were considered the best technique for tagging the animals in the subsequent growth studies. From 2010 to 2013, a total of 1604 O. vulgaris (74.4% with a total weight <300 g) were tagged with discs and released in an area of the central western Sardinian Sea (western Mediterranean Sea). Ninety-one specimens were recaptured after 4–63 days of freedom, 59 of which (31 males and 28 females) showed positive growth increments after a minimum time of 8 days at liberty. In general, a high individual variability (0.96–9.09 g day−1) and higher mean daily growth rates in females (3.07–3.65 g day−1) than in males (2.08–2.98 g day−1) were recorded, but this difference was not statistically significant. Using tag–recapture data, the first exponential growth curves for both sexes of Octopus vulgaris of small–medium size from the Mediterranean Sea were obtained, and compared with those available in the literature for the species. [ABSTRACT FROM PUBLISHER]

The article investigates the growth of spiny lobsters Palinurus elephas in an area where fishing is banned, in central western Sardinia, Italy. 4,044 lobsters were tagged and released between 1997 and 2004 in the area. The growth increments of 248 recaptured lobsters inside the no-take area and in the surrounding zones were recorded and analyzed and were estimated for each sex. Growth increments recorded inside and outside the no-take area did not reveal any density-dependent effects on females. Little and insignificant differences were found for males, showing faster growth in lobsters caught outside the no-take area.

• Life-history traits of Mediterranean Torpedo Rays are reported. • Annual band counts in Torpedinidae vertebrae is a highly reproducible process. • The deposition of a single band pair per year was confirmed in T. marmorata. • T. marmorata , differently from most of Batoids, matures relatively early. • Mediterranean Torpedoes feed mostly on demersal bony fishes. 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 ∞ = 622 mm TL; k = 0.15; IP = 2.75 years), while males' by a logarithmic one (von Bertalanffy L ∞ = 485 mm TL; k = 0.14; t 0 = -2.28). The oldest female and male were aged 17 (560 mm TL) and 11 (432 mm TL), respectively. Females (L 50 = 379 mm TL and A 50 = 5.5 years) appeared to mature later than males (L 50 = 272 mm TL and A 50 = 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. [ABSTRACT FROM AUTHOR]