In this manuscript, thirty yellow-pigmented Gram-positive bacteria were isolated from natural intestine microflora and from sea water around the marine cage of a rearing tank of common dentex (Dentex dentex), in the Aegean Sea on the Turkish coast and were characterized. Eighteen isolates were assigned to the species Micrococcus luteus, the other twelve to the species Bacillus marisflavi. Eight representative strains, six from B. marisflavi and two from M. luteus, were chosen for further 16S rDNA analyses. A pathogenicity assay for the isolated bacterial strains was carried out in rainbow trout and it evidenced absence of pathogenicity in the tested strains. The isolated strains were tested for in vitro antagonistic activity against Listonella anguillarum, a pathogen bacterium diffused in Mediterranean aquaculture and affecting various fish species. The isolated bacterial strains showed antagonistic activity against the pathogenic bacterium, suggesting a possible role of isolates as probiotics. In this study, for the first time, bacterial strains of the species B. marisflavi, known as an environmental species, were recovered in the gut microbiota of a healthy fish. The use of the isolates characterized in this study, mainly the yellow-pigmented bacterium, is suggested as possible probiotics to improve fish health, along with alternative methods of maintaining a healthy environment.

The study aimed at identifying spawning season and potential year classes reaching maturity in the north-eastern Mediterranean, an area where little information on tuna spawning is available. Gonads (60 ovaries and 36 testis) were obtained from little tunny, Euthynnus alletteratus. The fish were caught between

Summary The criteria of testicular maturity during the spawning season and for maturity rates are described according to age for 140 male albacore (Thunnus alalunga, Bonnaterre, 1788) sampled between April and August, 2002–2008 in the Eastern Mediterranean Sea. Histology of gonad samples was used to determine maturity status. Spermatogenesis and its relation to reproductive biology are reported. Fish ranged in fork length (FL) from 63 to 90 cm. The reproductive classes were based upon changes in the testicular morphology and stages of the germinative cells, i.e. immature, developing, maturing, spawning, and spent. Mature stages of testes including the smallest sample of a 63 cm male were observed from May to August of each year during the study. The reported evidence indicates that the size and age of first sexual maturity values of males of the Eastern Mediterranean population are nearly the same as in the Western Mediterranean population, but lower than in the Atlantic stock. The results of this histological investigation, conducted for the first time on this species in the Mediterranean Sea, will enable more precise future estimations for sustainability of the male albacore stock in the Eastern Mediterranean.

Objective: Gilt-head seabream (Sparus aurata) is an important species for Turkish aquaculture and bacterial diseases are one of the limiting factors for the production of this species. The aim of this study is the identification of the bacterial disease agents in cultured gilt-head seabream in Turkey and the determination of their antibacterial susceptibilities. Materials and Methods:In this study, 27 diseased gilt-head seabream samples between 3-130 g, showing various clinical symptoms, were examined bacteriologically. Bacterial isolates recovered from moribund fish samples were identified by using standard bacteriological methods and API 20E rapid identification strips. Antibiotic susceptibility tests of 10 different substances against these isolates were determined by using Kirby-Bauer disc diffusion method.Results: Vibrio anguillarum, V. scophthalmi, V. logei, V. harveyi, Pseudomonas anguilliseptica, P. stutzeri, Staphylococcus sp. and Micrococcus luteus isolates were isolated from diseased fish samples as pure and mixed infection. It was detected that API 20E may give erroneous results for fish pathogenic bacteria since they are not included in the database of the kit. Generally, enrofloxacin, florphenicol and oxytetracycline were found to be the most effective antibiotics against bacterial isolates. Conclusion:This study is the first report for V. scophthalmi, V. logei, V. harveyi, P. stutzeri and M. luteus infections of gilt-head seabream in Turkey.

Larval fish have a relatively poorly developed immune system and hence they primarily rely on non-specific immune responses produced in the skin and gut. This study aims to illustrate the fine structure of gut development in common dentex (Dentex dentex) larvae and determine the initiation of pinocytic activity, which is an important early non-specific immune response in fish intestines, during various live-food feeding stages (yeast enriched rotifer, Artemia nauplii and metanauplii) from hatching (D0) to 25 days after hatching (D25) by using transmission electron microscopy (TEM). A total of 54 larvae were sampled and examined with electron microscopy. The results show that hind-gut intestine enterocytes have morphological features which suggest they play a role in absorption and intracellular digestion of nutrients in fish. The presence of vigorous pinocytic activity in the Artemia feeding stage between 17-25 days after hatching is evidence for the development of a nonspecific immune system. In the present study, the ultrastructural gut development of cultured common dentex was investigated for the first time and the data reported in this study may provide additional fundamental knowledge for improving larval rearing success in common dentex culture. The IJA appears exclusively as a peer-reviewed on-line open-access journal at http://www.siamb.org.il. To read papers free of charge, please register online at registration form. Sale of IJA papers is strictly forbidden.