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European sea bass, Dicentrarchus labrax L., groups reared under different conditions during larval stages (mesocosm and intensive rearing) were monitored during on-growing in sea cages until marketable size (350-400 g). Four caged groups were followed for a period of 17 months each at a pilot scale farm, where vertical distribution behaviour was monitored. This was performed while fish were under calm conditions, during feeding and when stress events occurred. Also during two specific periods: (i) spawning and (ii) high water temperature. Clear differences in the behavioural pattern of swimming depth, displacement and used space between the groups were observed. The individuals from the mesocosm rearing were more sensitive to human presence, showing stronger reactions (speed of displacement and vertical distribution). Most pronounced differences were observed during the 'extreme' warm period and the reproductive season. Within the seasons, European sea bass responded during feeding and stress showing a tendency to move deeper compared to calm conditions. The increased displacements were longer during feeding and stress. [ABSTRACT FROM AUTHOR]

The working hypothesis of the present study is to verify whether, the spatial distribution of sea bass fry remains invariable under the pressure of certain rearing conditions, due to its extended plasticity or, certain situations lead to specific distributions. for this reason, we investigated and com pared horizontal and vertical distribution of sea bass reared in aquaria, at three different stocking densities (5 ind. l-1, 10 ind. l-1 and 20 ind. l-1), two different temperatures (16 and 23°C) and two different feeding conditions (feeding fish and starving fish). the analysis of the video records and General Linear Models revealed a strong effect of stocking density, feeding condition, and day of experimentation on fish behavior interpreted by the vertical and horizontal distribution of fish. temperature also affected distribution when it was combined with stocking density and feeding condition. however, this effect seemed to be lessened by the effect of the other variables (i.e. stocking density, feeding condition and day of experimentation). the exposure time (chronic stress) to the stocking density, temperature and feeding condition as well as to their additive cumulative effect (variables interactions) was the cause of the development of stereotypic behaviors that increased in occurrence frequency and over an experimental time lapse and gradually led to the weakening and death of the fry (bad welfare). thus, it is assumed that stocking density, feeding condition, day of experimentation and temperature can have negative effects on sea bass "well being" and in order to maintain its welfare during rearing it is important to take all necessary pre cautions of handling when dealing with these variables in the fish environment. [ABSTRACT FROM AUTHOR]

Five cultures of microalgae ( C hlorella minutissima, T etraselmis chui, N annochloropsis sp., A rthrospira platensis and I sochrysis sp.) with no culturable bacteria were tested for their ability to inhibit the growth of six V ibrio bacterial strains ( V . parahaemolyticus, V . anguillarum, V . splendidus, V . scophthalmi, V . alginolyticus and V . lentus). The influence of light on the antibacterial activity of the microalgae was investigated. All microalgae cultures inhibited the growth of bacteria compared with the control treatments ( P < 0.05), and their antibacterial activity was not influenced by the presence or absence of light. In the control groups, the numbers of bacteria increased exponentially during the experimental period in the absence of microalgae cells demonstrating that the bacterial cells were able to utilize the growth medium of microalgae cultures. The present results may explain the low levels or absence of V ibrio strains in microalgae cultures, and the positive effect of addition of microalgae in rearing of fish larvae, and implicate the production of antibacterial compounds by microalgae cells. [ABSTRACT FROM AUTHOR]

The rotifer Brachionus plicatilis is a common brackish-water zooplankter, and one of the beststudied rotifer species. It is characterized by high growth rate, widespread distribution, ubiquity in aquatic systems, ease of culture, adequate size, ability to feed on a variety of feed types and a complex life cycle. It has been used extensively as a tool in aquaculture and ecotoxicology and constitutes a model organism in ecological and evolutionary studies. This paper explores other possible uses of this organism in various fields: environmental control of eutrophication and harmful algal blooms, containment of cholera, management of pollution and petroleum compounds, wastewater treatment, impact of climate change on biodiversity and transfer of useful substances. [ABSTRACT FROM AUTHOR]

In the present study the reproductive biology of Tonna galea (Linnaeus, 1758) was studied for the first time. In mid-September 2006 one individual was found laying a pale pink egg rosette of 39.5 cm length. Number of embryos, stages of development, shape and dimensions were studied in relation to time and measured on microphotographs of randomly sampled capsules. Each oval or spherical shaped capsule of 3.61 mm total length contained 101 developing embryos. The embryo diameter ranged from 297.5 µm of the unsegmented egg to 489 µm of the free veliger. At 21°C eclosion occurred 34 days after capsule deposition, at a free-swimming veliger stage. The duration of each developmental stage, from one cell to veliger, is reported. Results are discussed in relation to possible culture and use for ecological purposes. [ABSTRACT FROM AUTHOR]

Red porgies ( Pagrus pagrus) of 20.6±1.5 g mean weight were reared in tanks under four delayed self-feeding conditions (0=control, 7, 30 and 90 s) after rod activation. The time intervals were chosen to simulate the time taken for a commercial pelleted feed to transit the tube linking a surface-mounted feed hopper and the depth at which a cage might be submerged. Daily feeding rate, growth, food conversion index and condition factor were quite similar but fish behaviour differed among conditions. Fish remained close to the feeding point in the first two treatments (0 and 7 s delay) but foraged more widely in the remaining treatments (30 and 90 s delay), only reconsolidating around the feeding point a few seconds before feed was released. Results are discussed in relation to learning capacity and adaptation of fish to feeding behaviour flexibility, in order to develop reliable self-feeding systems suitable for submerged cages. [ABSTRACT FROM AUTHOR]

The freshness of red porgy slaughtered in ice slurry and stored in melting ice was evaluated instrumentally, biochemically and sensorialy. Additionally, postmortem skin colour changes were monitored, in an attempt to demonstrate the use of chromaticity parameters as a reliable and convenient approach to quality assessment. Dielectric properties showed a statistically significant decrease ( P<0.05) from 12±0 on day 0 to 7.85±0.31 on day 7; there was also a significant decrease in muscle polyamines with more than two amino groups (spermidine and spermine) and an increase in the di-amine putrescine. The sensorial score was significantly decreased from 30±0 to 4.33±0.21 on day 7. Minimal lightness ( L) and hue ( H° ab) at the dorsal skin area were observed on days 1 and 3 following harvesting. Finally, there was a marked decrease in the entire colour index (ECI - a combination of skin hue and chroma) of both the dorsal and the ventral area in day 3 onwards to day 7, as well as a statistically significant correlation between all the estimated freshness indices and ECI. Based on all these, we inferred that the total polyamines (or putrescine to spermidine and spermine ratio) and ECI could be reliable estimators of freshness, at least under the experimental conditions applied. [ABSTRACT FROM AUTHOR]

Unicellular green alga Chlorella minutissima, grown under extreme carbon dioxide concentrations (0.036–100%), natural temperature and light intensities (Mediterranean conditions), strongly increase the microalgal biomass through photochemical and non-photochemical changes in the photosynthetic apparatus. Especially, CO2 concentrations up to 10% enhance the density of active reaction centers (RC/CSo), decrease the antenna size per active reaction center (ABS/RC), decrease the dissipation energy (DIo/RC) and enhance the quantum yield of primary photochemistry (Fv/Fm). Higher CO2 concentrations (20–25%) combine the above-mentioned photochemical changes with enhanced non-photochemical quenching of surplus energy, which leads to an enhanced steady-state fraction of ‘open’ (oxidized) PSII reaction centers (qp), and minimize the excitation pressure of PSII (1 − qp) under very high light intensities (approximately 1700 μmol m−2 s−1 maximal value), avoiding the photoinhibition and leading to an enormous biomass production (approximately 2500%). In conclusion, these extreme CO2 concentrations – about 1000 times higher than the ambient one – can be easily metabolized from the unicellular green alga to biomass and can be used, on a local scale at least, for the future development of microalgal photobioreactors for the mitigation of the factory-produced carbon dioxide. [ABSTRACT FROM AUTHOR]

The article presents a study that aims to determine whether the hybrids produced by the protandous gilthead seabream (Sparus aurata) and the protogynoyus Mediterranean red porgy (Pagrus pagrus) display sterile gonadal development. Sparids are characterized by peculiar bisexual gonads consisting of a medio-dorsal ovarian area and a latero-ventral testicular area. The female sex dominated in the hybrids with differentiated gonads. Female dominance is a common characteristic to both parental species when they are 2-3 years old. Female hybrids mature with delay compared with parental species regardless of their normal gonadal development.

Two series of experiments were conducted for the evaluation of the effect of dietary taurine supplementation on survival, growth performance and feed preference of sea bass Dicentrarchus labrax fry when fed with demand-feeders a fish/soybean meal-based diet. In the first experiment, fish were imposed one of four diets supplemented with taurine (0, 0.1, 0.2 or 0.3% taurine on a dry weight basis), while in the second they had simultaneous free access to the four diets supplemented with taurine. When not allowed to choose, fish exhibited better specific growth rate of 3.2 and 3.2% per day with diets supplemented with 0.2 and 0.3% taurine than those of 2.3 and 2.2% per day of 0 and 0.1% taurine, respectively. When fish were free to access the diets, they selected more actively the 0.2 and 0.3% taurine-supplemented diets than the 0 and 0.1% taurine. As survival was not significantly different among trials, the results indicate that sea bass fry require a 0.2% taurine in the diet for better growth when fish meal and soybean meal are the primary sources of protein. The positive correlation between growth performance and nutrient preference is discussed as a method for improvement of fry food formulation. [ABSTRACT FROM AUTHOR]

This paper describes severe mortalities recorded in sharpsnout sea bream Diplodus puntazzo larvae reared in mesocosms. The mortalities were attributed to epitheliocystis infection. The pathology associated with the disease is described using histological techniques. Microscopical examination showed a massive infection of the skin, fins, and oral cavity, with impaired feeding, respiration, and osmoregulation being the most likely cause of death. This is the first report of epitheliocystis disease in sharpsnout sea bream and in fish at such an early developmental stage.

Unicellular green alga Chlorella minutissima, grown under extreme carbon dioxide concentrations (0.036-100%), natural temperature and light intensities (Mediterranean conditions), strongly increase the microalgal biomass through photochemical and non-photochemical changes in the photosynthetic apparatus. Especially, CO(2) concentrations up to 10% enhance the density of active reaction centers (RC/CS(o)), decrease the antenna size per active reaction center (ABS/RC), decrease the dissipation energy (DI(o)/RC) and enhance the quantum yield of primary photochemistry (F(v)/F(m)). Higher CO(2) concentrations (20-25%) combine the above-mentioned photochemical changes with enhanced non-photochemical quenching of surplus energy, which leads to an enhanced steady-state fraction of 'open' (oxidized) PSII reaction centers (q(p)), and minimize the excitation pressure of PSII (1 - q(p)) under very high light intensities (approximately 1700 micromol m(-2) s(-1) maximal value), avoiding the photoinhibition and leading to an enormous biomass production (approximately 2500%). In conclusion, these extreme CO(2) concentrations - about 1000 times higher than the ambient one - can be easily metabolized from the unicellular green alga to biomass and can be used, on a local scale at least, for the future development of microalgal photobioreactors for the mitigation of the factory-produced carbon dioxide.

The temperature sex determination (TSD) mechanism in the European sea bass (Dicentrarchus labrax L.) was studied in respect to: a) the TSD sensitivity during the different developmental stages; and b) the intrapopulation correlation of sex determination with the growth rate up to the end of the TSD-sensitive period. At the stage of half-epiboly, eggs from the same batch were divided into four groups and subjected to different thermal treatments: a) 15 degrees C (G15 group) and b) 20 degrees C (G20 group) up to the middle of metamorphosis stage; c) 15 degrees C up to the end of yolk-sac larval stage and subsequently to 20 degrees C (G15-5 group); and d) 15 degrees C up to the end of the preflexion stage and then to 20 degrees C (G15-10 group). At the end of the treatments, size grading was applied and four additional populations were established from the upper (L) and lower (S) size portions of the G15 and G20 populations: G15L, G15S, G20L, and G20S. During the following growing phase, all populations were subjected to common rearing conditions. The sex ratios of each population were macroscopically determined at 190-210 mm mean total length. Female incidence was significantly affected (P < 0.05) by the different thermal treatments: 66.1% in the G15, 47.1% in the G15-10, 37.6% in the G15-5, and 18.1% in the G20 group. In addition, sex ratio was correlated with the growth rate of the fish up to the end of the TSD-sensitive period, with the larger fish presenting a significantly higher (P < 0.01) female incidence than the smaller fish in both thermal regimes tested: 73.1% in G15L vs. 57% in G15S, and 36.6% in G20L vs. 22.5% in G20S group. Results provide, for the first time, clear evidence that the sea bass is sensitive to TSD during all different ontogenetic stages up to metamorphosis, and that sex ratio is correlated with the growth rate of the fish well before the differentiation and maturation of the gonads., (Copyright 2002 Wiley-Liss, Inc.)