The ovaries of 501 female eastern Atlantic bluefin tuna (Thunnus thynnus Linnaeus, 1758) captured in the Mediterranean Sea from May to September between 1998 and 2004 were analysed histologically. Body size at median sexual maturity (L-50) was 103.6 cm, fork length (FL), while 100% maturity was reached above 135 cm FL. The age analysis, based on the count of the translucent zones of the first spiniform ray of the first dorsal fin, showed that most of the specimens with FL = L-50 were 3 years old while 100% maturity was reached between 4 to 5 years. The reported evidence indicates that for the eastern Atlantic bluefin tuna stock, the size and age of first sexual maturity of females was lower than in the western Atlantic stock.\u

SummaryThe objective of the study was to describe the biometry of Mediterranean bluefin tuna, Thunnus thynnus, the biology of which is not yet well understood. A total of 504 specimens was collected from 1998 to 2005 in the central part of the Mediterranean basin. They were sexed and measured; fork lengths (FL) ranged from 51.0 to 255.0 cm while body weights (W) ranged from 2.6 to 247.0 kg. The first spiniform ray (spine) of the first dorsal fin was removed and cross-sectioned near the condyle base in order to count annuli for age estimation. The regression coefficient (b) of the female FL-W relationship was significantly higher than that of the male, and both sexes displayed a negatively allometric growth (b < 3); male regression equation: ln W = )2.942 + 2.730 ln FL; female regression equation: ln W = )3.660 + 2.878 ln FL. Based on counts of the translucent zones in the sections of the first ray of the first dorsal fin, estimated ages ranged from 1 to 15 years for males and 1 to 14 years for females. The correlation between the spine ray (R) and FL fit the allometric model best; the R-FL regression equations of the two sexes did not differ significantly and the overall equation was: ln FL = 3.721 + 0.851 ln R. Due to the R-FL allometric correlation, estimates of fork lengths at previous ages, FL i , were back-calculated with a body proportional hypothesis. Von Bertalanffy growth equations were derived from both observed and back-calculated FLs-at-age, which did not differ significantly. Moreover, no significant difference was found between the growth equations of the two sexes; the overall equation was FL t = 373.08 [1)e )0.07(t + 1.76) ]. Weight-at-age values were derived from the von Bertalanffy predicted FLs-atage by the FL-W correlation equations for males and females. The paper represents the first comprehensive study on the biometry, including age and growth, of bluefin tuna captured in the Mediterranean Sea.

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Melanomacrophage centres (MMCs), located in different organs of non-mammalian vertebrates, play a role in the destruction, detoxification or recycling of endogenous and exogenous materials. Cytochrome P450 monoxygenase 1A (CYP1A) is involved in xenobiotics biotransformation, and its liver expression is considered as a biomarker for detecting exposure to environmental pollutants. Atlantic bluefin tuna (ABFT), Thunnus thynnus L., liver samples were collected from: wild animals caught in the eastern Atlantic; juveniles reared in the central Adriatic; juveniles reared in the northern Adriatic; adults reared in the western Mediterranean. The samples were processed for basic histology, histochemistry and for CYP1A immunodetection. An unexpected high density of MMCs, containing ferric iron and lipofuscin-ceroids, was detected in the juveniles sampled in the northern Adriatic Sea. These individuals showed also a strong anti-CYP1A immunopositivity in hepatocytes and in the epithelium of bile ducts. This study supports the utility of MMCs as biomarkers of fish 'health status' and gives concern for a potential contaminant accumulation in ABFT.

The greater amberjack, (Risso, 1810), is a promising candidate for the diversification of European aquaculture production, but inconsistent reproduction in captivity prevents commercial production. Recent studies showed that greater amberjack confined in sea cages exhibited scarce gonad development and early interruption of gametogenic activity during the reproductive season. The aim of the present study was to improve our understanding of the observed impairment of spermatogenesis. Adult wild and captive-reared males were sampled during 3 different phases of the reproductive cycle: early gametogenesis (EARLY; late April to early May), advanced gametogenesis (ADVANCED; late May to early June), and spawning (SPAWNING; late June to July). Spermatogonial stem cells and proliferating germ cells were identified through the immunohistochemical localization of and proliferating cell nuclear antigen, respectively. Apoptotic germ cells were identified throughout the terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labeling method. Sperm quality of captive-reared fish was evaluated using computer-assisted sperm analysis. Captive-reared males exhibited seminiferous lobules of a smaller diameter, a precocious and progressive decrease of spermatogonial mitosis, and a high level of apoptosis at the beginning of the reproductive season, concomitant with a many-fold higher 17β-estradiol plasma concentration. The motile spermatozoa percentage of captive greater amberjack was lower than in other teleosts, and a drastic decrease of spermatozoa motility duration, velocity, and ATP content occurred along the reproductive season. An abnormal increase of sperm concentration as well as an increase of dead spermatozoa occurred during the SPAWNING phase, probably because of lack of sperm hydration and ejaculation and consequent sperm ageing. The present study demonstrates the extreme susceptibility of greater amberjack to rearing stress and underscores the need for improvement of the rearing and handling procedures to ameliorate gametogenesis dysfunctions in commercial aquaculture production.

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Incidental catches in pelagic longline fishing pose a serious threat to sea turtle\ud populations throughout the world’s seas and oceans. In this work, carried out in the framework of the EC-DG-Fisheries 98/008 project, information on sea turtle catch rates from swordfish and albacore longline fishing activities observed in Italian waters off the Ionian Sea during 1999 and 2000, are reported. In addition, biometric data, health status, and tagging return rate of sea turtles captured are provided. A total of 200 sea turtles were caught (198 loggerhead turtles and 2 green turtles), comprising\ud 0.5–15.7% of the total catch in number of individuals. The estimates of the sea turtles caught by the total fishing effort of both longlines in the whole study area were 1084 specimens in 1999 (95%\ud CI = 667–1502) and 4447 specimens in 2000 (95% CI = 3189–5705). Although all sea turtles were released alive, nearly half of them had hooks that could not be removed and remained deeply embedded\ud in the digestive tract

Summary The most commonly observed reproductive dysfunction in male fishes reared in captivity is reduction in sperm volume and quality. The Atlantic bluefin tuna Thunnus thynnus (Osteichthyes: Scombridae) is one of the few large pelagic and migratory marine fishes maintained in captivity with the purpose of establishing breeding populations to support an aquaculture industry. The objectives of the present study were to compare male germ cell proliferation and apoptosis between wild and captive individuals at two different phases of the spermatogenetic cycle, and to evaluate sperm motility characteristics of captive individuals. Histological observations were performed to analyze testicular activity, and germ cell proliferation and apoptosis were evaluated through the immunohistochemical detection of proliferating cell nuclear antigen (PCNA) and the terminal deoxynucleotidyl transferasemediated d'UTP nick end labeling (TUNEL) method, respectively. Computer‐assisted sperm analysis (CASA) was used to evaluate sperm motility. Results showed that germ cell proliferation was delayed and germ cell apoptosis increased in captive animals relative to wild individuals. Sperm motility of samples obtained from captive individuals was anomalous, both in terms of motility duration and swimming efficiency. Thus it appears that rearing in captivity impairs male reproductive function through, at least, changes in germ cell proliferation and apoptosis.