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Introduction For some years now, IMTA (Integrated MultiTrophic Aquaculture) concept has gained worldwide attention. Integrating complementary species such as fed aquaculture species (e.g. finfish), inorganic extractive aquaculture species (e.g. phytoplankton and seaweeds) and organic extractive species (e.g. bivalves, sea-urchins, and sea-cucumbers) is an attractive concept to enhance the efficiency of aquaculture (Neori et al., 2004). IMTA has the potential to increase profitability while simultaneously act as bioremediator of effluents. The environmental and economic costs of feed are high and the expected increase of aquaculture in the future, demands a more efficient use of nutrients highlighting the potential role of recycling mass and energy in the systems (Naylor et al., 2000). Some advantages of the use of IMTA are (1) decrease the dependence on external inputs, (2) increase the system efficiency by optimizing the use of nutrients and energy in the production loop, (3) decrease the waste effluents and bio-deposit impacts by limiting the loss of nutrients (in water, sediments and air), (4) diversify farm- products and generate a more robust source of income (less dependent on mono-product markets), and (5) generate and use different types and levels of ecosystem functions and services. Despite the potential benefits of IMTA its development is still limited in Europe. Many factors can explain this situation and among them, the performance of the extractive organisms and the economic performance of the systems (Hughes and Black, 2016). The lack of knowledge, expertise and reference data for dimensioning and optimizing the systems, and their intrinsic complexity are still prevalent. There is need for greater body of evidence of the financial benefit to the farmer, better ways to reduce the system complexity, and better support from policy and regulation to reinforce the increase in social license associated with IMTA. The proof of concept has to be established and confirmed in different systems' configuration. Material and methods IMTA-EFFECT (Integrated MultiTrophic Aquaculture for EFFiciency and Environmental ConservaTion) is an EU ERA-NET project aiming to evaluate the performance of several European systems (and also few tropical systems) in order to provide references data for implementing IMTA. Several IMTA approaches were integrated for this purpose. Experiments are conducted in different countries and contexts: multitrophic marine systems (in Portugal, France and Greece) combining fish, algae, filter and/or deposit feeders; and fresh water polyculture systems (in Romania, France, Indonesia and Madagascar) combining fish and plants (micro and macrophytes). These systems were conceived according to two modalities: 1- species reared separately in different structures allowing a precise measurement of each species activities and their role in nutrient and energy cycling, 2- species reared all together in the same structure, showing an overall performance of species interactions. Modelling is the common methods to evaluate the fate of nutrient and energy in the system and among the different species. Mass balance has been established in each system. ECOPATH (Christensen and Pauly , 1992; Pauly et al ., 2000) is being used in the systems where species are reared all together to assess the interactions of trophic levels, including the produced species (Gamito and Erzini, 2005; Xu et al., 2011). Dynamic Energy Budget modelling is used mostly in the systems where species are reared separately to investigate how different types of food (quality and quantity) will affect growth performances and nutrient excretion of cultivated species (Pouvreau et al., 2006). Both methods are being calibrated and validated using carbon and nitrogen stable isotopes and fatty acid analyses, which help to characterize the different pathways of energy and nutrients between the species and compartments, and therefore the efficiency of the studied IMTA systems. In a more advanced stage of the project, Emergy accounting (Odum, 1996) and Life Cycle Assessment (Wilfart et al., 2013) will permit to characterize economic and environmental performances at a more global level. Finally, the perception of stakeholders including aquaculture farmers and policy makers, for ecosystem services provided by IMTA will be studied to draw specific future prospects of development. Results IMTA Effect project is still in progress. The implementation of the several IMTA approaches will contribute to better integrate and root the production system in the territory, particularly in the ecosystem, and the socioeconomic environment. Main features of different systems under study and preliminary results will be presented.

A strain of the lineage Brachionus 'Nevada' was batch cultured with two diets, differing in biochemical composition: baker's yeast (treatment 1), which has higher protein:lipid ratio compared with CULTURE SELCO (treatment 2). The biochemical composition (DNA, RNA, lipid, protein content) and fatty acid profile of rotifers of both treatments was analysed and related to previously published population structure data. CULTURE SELCO-fed rotifers showed higher DNA, RNA, lipid, n-3 highly unsaturated fatty acids (HUFA) average content, compared with yeast-fed rotifers, which had higher protein content. Rotifer lipid content showed significant diurnal variation in yeast-fed rotifers. Rotifer lipid and n-3 HUFA content was associated with reproductive output. DNA and RNA content was related to embryonic development while protein content, to somatic growth and mixis. The saturated and monounsaturated fatty acid rotifer content was stable irrespective of feed, in contrast to eicosapentanoic acid (EPA) and DHA. The levels of AA were similar in both rotifer populations, but those of EPA and docosahexaenoic acid (DHA) were about half in yeast-fed compared with CULTURE SELCO-fed rotifers. CULTURE SELCO resulted in a temporally stable rotifer lipid profile and a better enriched parthenogenetic population. © 2013 John Wiley & Sons Ltd.

The distribution and biometry of commercial sponges (Porifera) in coastal areas of the central and southeastern Aegean Sea was investigated to estimate the recovery progress of the populations eight years after the first appearance of sponge disease. Signs of the disease were detected only in 1.6% of the harvested sponges. Multivariate analysis on the percentage abundance of sponges showed two distinct groups among the sixteen fishing grounds studied: the eight deep (50-110 m) and the eight shallow ones (

Three parthenogenetic brine shrimp Artemia populations from saltworks in Greece (Messolongi, Milos and Polychnitos) were studied with regard to their biochemical composition and the activity of digestive enzymes in four developmental stages from decapsulated cysts to nauplii instar III. The content of protein and RΝΑ was highest in nauplii instar II (65.10 and 6.23% dry weight, respectively), while that of total lipid was highest in nauplii instar I (11.40% dw). The carbohydrate content was highest in decapsulated cysts (10.30% dw) and about one half that value in nauplii instar I. The DNA content was ten-fold higher in nauplii instar I than in decapsulated cysts with the highest levels in nauplii instar III (3.67% dw). The activity of alkaline phosphatase, leucine aminopeptidase, valine aminopeptidase, cystine aminopeptidase, β-galactosidase, β-glucosidase, esterase lipase (C8), esterase (C4), N-acetyl-β-glucosaminidase, α-fucosidase, acid phosphatase and naphthol-AS-BI-phosphohydrolase increased significantly from decapsulated cysts to nauplii instar II and remained constant or decreased in nauplii instar III. In nauplii instar II, leucine aminopeptidase, β-galactosidase, alkaline phosphatase and esterase (C4) demonstrated higher activity levels (140.90, 133.62, 66.01 and 45.47 nmoles/100 μg dw within 5 min, respectively) of the aforementioned enzymes. The Artemia population of Messolongi had significantly higher levels of DNA, protein and alkaline phosphatase activity per individual, as well as body weight, compared to the Artemia populations of Milos and Polychnitos. The latter population showed the lowest level of lipid and the highest esterase activity (C4) per individual. There was a reverse relationship between the protein content and leucine aminopeptidase activity, lipid content and esterase (C4) activity, carbohydrate content and β-galactosidase activity among the three Artemia populations. The variations observed in the biochemical composition and the activity of some specific enzymes should be taken into consideration in selecting these Artemia populations from Greece for application in aquaculture. © 2008 Elsevier B.V. All rights reserved.

The aim of this study was to investigate changes in the ribonucleic acid (RNA)/deoxyribonucleic acid (DNA) ratio and the fatty acid composition of cultured Octopus vulgaris (50-750 g) in relation to recent (last 30 days) specific growth rate (SGR). Wild animals (80-500 g), collected in the field throughout the year (Aegean Sea, Mediterranean), were also examined for the aforementioned biochemical parameters. Octopuses were reared in a closed seawater system at three different temperatures (15, 20 and 25°C). The octopuses were fed on squid (Loligo vulgaris). The cultured animals showed a high n-3 (33-52.9%) and n-6 (3.3-13.7%) polyunsaturated fatty acid content, but with a high variation for 22:6n-3 [docosahexaenoic acid (DHA)], 20:5n-3 [eicosapentaenoic acid (EPA)] and 20:4n-6 [arachidonic acid (AA)]. The proportion of these fatty acids (% total fatty acids) and the RNA/DNA ratio were linearly (P

Evaluation of a new-to-science Artemia population and comparison with four other existing populations were carried out. Five parthenogenetic Artemia populations from the following Greek saltworks were studied: Alyki (a new population), Kalloni, Milos, Polychnitos and Messolongi. The diameters of non-decapsulated and decapsulated cysts as well as the lengths of nauplii instar stages I, II and III were measured. In addition, the fatty acid composition of decapsulated cysts was estimated. The cyst size of the Alyki population was the smallest, with the largest chorion found in Greece so far. The Messolongi population had the largest cysts, with the smallest chorion of all five populations. The diameter of the non-decapsulated cysts was highly related (P

The content (% wet mass) in water, ash, lipid, crude protein, DNA and RNA of different tissues was determined during sexual maturation of bonitos Sarda sarda from the Aegean Sea. A total of 220 specimens were collected in the following stages of sexual maturity: immature, resting, developing, mature, spawning and spent. Highest lipid levels in the white muscle, red muscle and liver were measured in immature specimens, while lowest levels were found in spawning bonitos. The gradual percentage of lipid reduction from immature to spawning bonitos was relatively higher in the liver (females 71.2% and males 64.4%) than in the white (females 59.2% and males 53.5%) and red (females 62.1% and males 51.7%) muscle. Lipid levels in the gonads increased gradually from the immature to spawning stage. The decrease of lipid in the somatic tissues was more intense in females than in males, and gonadal lipid content was higher in females than in males. There was a strong reverse correlation between water and lipid percentage in all tissues. Protein content decreased significantly only in spawning bonitos. The percentage of protein reduction from immature to spawning stage was relatively higher in males than in females in both white (females 3.4% and males 4.6%) and red (females 4.6% and males 5.1%) muscles. Protein content in the liver was significantly lower than in the other tissues, being highest in mature females. Gonadal protein content in females increased with maturation and decreased after spawning. The content in ash exhibited considerable stability. The RNA:DNA ratio exhibited a similar pattern of variation in both muscles. The RNA:DNA ratio increased during gonadal development gradually from the developing to spent stage. It was concluded that in S. sarda during gonadal development, there was an increase in gonadal lipid accompanied by a decrease in somatic tissue lipid reserves. Thus, reproductive inactive bonitos have more lipid in their edible part and a higher nutritional value than active ones. © 2006 The Authors.

Two experiments were conducted examining the population structure of Brachionus 'Nevada' under feeding conditions commonly applied in hatcheries, using 4-day rotifer batch cultures. In the first experiment two diets were supplied: yeast with Tetraselmis suecica (treatment A) or Culture Selco® with T. suecica (treatment B). The second experiment (treatments C, D, E) differed in the phytoplankton quantity used (20 times higher): treatment C was analogous to A and treatments D and E to B. Initial rotifer density differed among treatments and was about 200 individuals ml-1 in A, C and E, and 60 individuals ml-1 in B and D. Multivariate analysis discriminated A and C from B, D and E. In treatments A and C, a 24-h cycle in ovigerous females, immature individuals and E/F ratio was observed, showing a high reproductive rate. Treatments B, D and E displayed a 48-h cycle in the aforementioned parameters, indicating a lower reproductive rate. The latter treatments had a significantly higher number of females with multiple eggs for most of the samplings, compared to A and C, except for treatment E until 40 h of sampling. Specific growth rate was significantly higher in treatments B and D (Culture Selco® diet) compared to A and C (yeast diet), while treatment E had intermediate rates. Initial rotifer density influenced the abundance of females with multiple eggs, but resulted in slight variations in growth rate and population structure. The type of dry food greatly affected the population structure of rotifers, leading to significant differences in the growth rate. © Springer Science+Business Media B.V. 2006.

Octopus vulgaris is considered a serious candidate for rearing, in terms of its biological and market potential: easy adaptation to captivity conditions, high growth rate and high market price. The aim of this study was to examine the combined effects of temperature and body weight on specific growth rate (SGR, % day- 1), absolute growth rate (AGR, g day- 1), absolute feeding rate (AFR, g day- 1), feed efficiency (FE, %), protein retention efficiency (PRE: [g protein gain g protein ingested- 1] × 100), energy retention efficiency (ERE: [kJ gain kJ ingested- 1] × 100), proximate composition and P/E ratio (protein/energy) of the common octopus. The experiments were performed in a closed system with controlled temperature (15, 20 and 25°C). The octopuses were fed on squids (Loligo vulgaris). In the multiple regression equations estimated for SGR, AGR, AFR, FE, PRE and ERE, the linear and quadratic effects of temperature, as well as the linear effects of body weight were significant. In addition, the interaction effects of temperature and body weight were significant for SGR, AGR, FE, PRE and ERE; the temperature for maximum response decreased with increasing size, being 25°C for octopuses of 50-150 g and 15°C for animals of 200-600 g. The weight exponent in the relationships of these indices vs. body weight decreased with increasing temperature. The levels of SGR, FE, PRE and ERE varied slightly with temperature in individuals of 150-200 g, and the respective response surfaces showed a plateau within this range of body sizes independently of temperature. The temperature for maximum AFR was estimated to be 21.88°C independently of body weight. Proximate composition and P/E ratio of octopuses were not affected by temperature or body weight. It is concluded that temperature should be adjusted according to the body weight of O. vulgaris for optimizing the economic viability of rearing. Temperature should be high for small individuals (50-150 g) and should be reduced gradually in order for animals larger than 200 g to be reared at low temperature. Therefore, O. vulgaris should be reared in closed systems with temperature control. © 2005 Elsevier B.V. All rights reserved.

The common octopus, Octopus vulgaris Cuvier, is of great scientific and commercial importance and its culture is becoming an area of increasing interest. In this study, the combined effects of temperature (T) and body mass (M) on the routine oxygen consumption rate (R) and ammonia excretion rate (U) in O. vulgaris were quantified. The experiments were conducted in a closed seawater system, and great care was taken to reduce handling stress of the animals. Temperature, salinity, pH and ammonia, nitrite, nitrate and phosphate concentrations were monitored and controlled during the experiment. The following predictive equations were evaluated: R (μmol h-1) = e25.24-6952.8/Ta × M0.901 at temperatures between 13°C and 28°C and U (μmol h-1) = e 14.77-4324.7/Ta × M0.896 at temperatures between 15.5°C and 26°C (Ta is degrees Kelvin and M in gram). O/N ratios showed that O. vulgaris has a protein-dominated metabolism. No significant relationship between the O/N ratio and body mass or temperature was found. Sex had no significant effect on the oxygen consumption rate or on the ammonia excretion rate. For other octopod species, the dependence of metabolic rate on temperature does not differ with that for O. vulgaris. © Springer-Verlag 2004.

1. A survey was undertaken (1995) on the Mediterranean coast of Egypt that investigated four sponge fishing grounds. These fishing banks suffered from sponge disease between 1987 and 1990, causing a mass mortality of commercial sponges in the eastern and central Mediterranean. 2. Adult commercial sponges (length > 10 cm) were harvested by divers in the infralittoral zone (depth range 17-36 m). The substratum at most of the sampling stations was hard, consisting mainly of plaques, rocks and heavy stones, sometimes covered by Posidonia oceanica. 3. Two commercial sponge species were detected, Hippospongia communis and Spongia cfr zimocca; the former was more prevalent and abundant. Light penetration in the area surveyed was high. The two commercial sponge species detected seemed to be well adapted to these conditions, as indicated by the colour of their external membranes, which were almost black due to enhanced pigment formation. The absence of Spongia officinalis, in the area surveyed may also be related to light penetration, since S. officinalis is a more sciaphilous species. 4. The shape of H. communis was almost spherical, and the average dimensions (length, width, height, circumference) increased with increasing depth of the fishing grounds. At shallower depths (< 30 m), adult H. communis occurred in lower densities, whereas young commercial sponges were abundant. No signs of sponge disease were found. 5. It is concluded that the recovery of the four sponge fishing grounds was in progress, and that the repopulation of commercial sponges in the infralittoral zone showed a gradient from deeper to shallower waters. It is recommended to prohibit destructive fishing methods in the deeper waters in order to protect the population and its ability to regenerate. Copyright © 2005 John Wiley & Sons, Ltd.

Feeding causes an increase of metabolic rate, which initially escalates rapidly, reaches a peak value and then gradually declines to the pre-feeding rate. This phenomenon, termed "specific dynamic action" (SDA), reflects the energy requirements of the behavioral, physiological and biochemical processes that constitute feeding. The effect of temperature on SDA of the common octopus, Octopus vulgaris, was evaluated, by measuring the temporal pattern of the oxygen consumption rates of octopuses, after feeding, at two constant temperatures, 20°C and 28°C. At 20°C, the relative increase in the oxygen consumption rate after feeding (relative SDA) was significantly greater than at 28°C. The peak of the relative SDA occurred 1 h after feeding, and it was 64% at 20°C and 42% at 28°C. However, the SDA absolute peak, SDA duration (9.5 h) and SDA magnitude (the integrated postprandial increase in oxygen uptake) did not differ significantly between the two temperatures, indicating that the energetic cost of feeding was the same at both temperatures. The SDA response in O. vulgaris was much faster than it was in polar species, which have extended SDA responses due to low temperatures, and was also relatively fast in relation to the response in other temperate species, which is probably connected to the remarkably high growth rates of the species. A possible explanation of the observed summer migration of large octopuses from shallow to deeper areas is given, based on the effect of temperature on the energetic requirements of octopuses. © Springer-Verlag 2004.

For a period of 1 year, some blood parameters were evaluated on a monthly basis in a population of adult European sea bass (Dicentrarchus labrax L.) intensively reared in floating marine cages (Ionian Sea, Mediterranean). From April (13 months old) to July (16 months old) males (35-50%) and sexually indeterminate individuals were collected. From August to March (24 months old) only males were sampled. During this period the percentage of spermiated males was highest (100%) from November (20 months old) to January (22 months old). Plasma testosterone in males was inversely related to sunlight (h month-1) and was elevated between October and January, when males first achieved sexual maturity. Testosterone showed the highest value (0.49 ± 0.02 ng ml-1) in January and the lowest (0.09 ± 0.02 ng ml-1) in March. Haematocrit, red blood cell counts and haemoglobin concentration were elevated from November to March, being inversely related to sunlight. The two latter parameters were also inversely related to daily food intake. Haematocrit, red blood cell counts and haemoglobin concentration were highest in December [53 ± 1%, (5.36 ± 0.06) × 106 mm-3, 10.08 ± 0.14 g 100 ml-1, respectively] and lowest in June [35 ± 1%, (3.33 ± 0.05) × 106 mm-3 , 6.47 ± 0.13 g 100 ml-1, respectively]. White blood cell counts were not correlated with sea water temperature, sunlight or daily food intake. They were highest in February [(8.45 ± 0.20) × 104 mm-3] and lowest in April [(6.07 ± 0.14 × 104 mm-3]. Total plasma protein concentration (4.88 ± 0.11-5.93 ± 0.10 g 100 ml-1) and mean cell volume (93.3 ± 0.9-105.5 ± 1.8 μm3) showed small fluctuations throughout the year. Sexual maturity appears to be a major factor that significantly affects haemopoiesis of D. labrax. This study contributes to the evaluation of normal levels of some blood parameters in European sea bass, which are helpful for the assessment of physiological status and health of this species. © 2004 Blackwell Verlag, Berlin.

Acute toxicity studies, using two organotin compounds, tributyltin chloride (TBTCl) and triphenyltin chloride (TPhTCl), were performed on gilthead seabream, Sparus aurata, fertilized eggs. The tests were static and run for 24h (temperature = 19±1°C, salinity = 39.5g/L). Three replicate egg groups were incubated in solutions containing different concentrations of the toxicants. The (24h)LC50 value for TBTCl was 28.3μg/L and for TPhTCl was 34.2μg/L, when the embryos were at the morula and late blastula stage at the start of the experiment. The value for TBTCl was 38.6μg/L, when the embryos were at the gastrula stage at the start of the experiment. The results reconfirm the expected toxicity of TBT to this euryhaline fish species and introduce TPhT as a toxicant of potentially similar impact on teleosts. © 2002 Elsevier Science (USA). All rights reserved.

A lot of micro-organisms can been found in the sponge body. In the present study, bacteria and fungi were isolated from the massive commercial sponge Spongia officinalis Linnaeus, 1759 (Porifera, Demospongiae). Samples (sponge extract and sea water) were collected from several areas of the Aegean Sea (ports, beaches, eutrophic gulf and open sea) with different levels and types of contamination. Bacteria identified in sponge extract belong to the genera Escherichia, Morganella, Proteus, Pasteurella, Aeromonas, Pseudomonas and Acinetobacter. Two fungal genera, Trichosporum and Fisarium, were identified in sponge extract. Bacterial load was greater in sponge extract than in proximal sea water, reflecting the sponge ability to concentrate bacteria in its body. The assessment of bacteria associated with the sponge S. officinalis as indicators of contamination is proposed. © 2003 Elsevier Science Ltd. All rights reserved.

Concerns have been raised on the impact of bottom-fishing activities in the shallow Gulf of Kalloni (Lesvos Island, Aegean Sea). Fishing with demersal gears was banned in 1995, but the Gulf was reopened in 1998 only for scallop dredging using the "lagamna" gear. Two series of samplings were done with this gear in 1998 and 1999 (October) before the beginning of scallop-fishing period (from November up to March), aiming to investigate possible changes in sponge assemblages. Sponges (Porifera) were the most abundant mesomegafaunal benthic organisms in the Gulf, besides scallops and other bivalves. Total abundance, number of species, species diversity, species richness and evenness of sponge assemblages reduced significantly from the year 1998 to 1999. The population of the excavating Cliona celata, the only infaunal sponge species found in the Gulf, decreased. Multivariate analysis on the abundance data of epibenthic sponge species revealed a clear separation of samples collected during the 2 years, indicating changes in the structure of sponge assemblages. The distinguishing species included a variety of growth forms: massive (Mycale massa, Suberites domuncula and Tethya citrina), lobose (Suberites massa, Tedania anhelans and Halichondria panicea), erect branching (Raspailia viminalis), encrusting (Crambe crambe) and cushion-shaped (Mycale contarenii and Chondrilla nuculla) sponges. Among these species, only S. massa increased its abundance in 1999. All others decreased. No significant loss of information occurred when multivariate analysis was applied to abundance data of genera or families. This comparative study demonstrated that the time interval between two consecutive scallop-fishing periods was insufficient for the recovery of sponge assemblages. It is concluded that scallop dredging causes long-term changes in the structure and biodiversity of sponge assemblages in the Gulf of Kalloni. An improved strategy of fishery management is required in future for the conservation of living resources in this Gulf. © 2003 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.

Growth performance, carcass composition, liver and blood parameters of scaled carp (C), Cyprinus carpio, and blue tilapia (T), Oreochromis aureus, reared for eight weeks in two monoculture (100% C and 100% T) and two polyculture (60%C-40% T and 40%C-60% T) conditions were investigated. In polyculture 40%C-60% T both species achieved the highest levels of specific growth rate and the lowest levels of food conversion ratio and carcass lipid content. In addition, they exhibited the highest values of plasma pO(2) and pH and the lowest values of plasma pCO(2), cholesterol and albumin, although the differences among treatments were not significant in the case of tilapia. Tilapia showed significantly lower plasma Cl- levels than under the other conditions. Carp in monoculture and tilapia in polyculture 60%C-40% T had the lowest levels of specific growth rate and significantly higher levels of liver lipids and plasma triglycerides than in the other groups. In addition, carp in monoculture exhibited a significantly higher haematocrit than in polyculture. No significant variations among treatments were observed concerning plasma cortisol, glucose, osmolality, Na+,K+, HCO3- and HCO3-/H2CO3 in either species. The combination of scaled carp and blue tilapia, in which blue tilapia were the main species, proved to be the best for both species. It was suggested that growth and physiological changes under mono- and polyculture rearing, in an intensive system, seem to be as a result of a different state of stress related to fish behavior.

The effects of formaldehyde preservation on biometrical characters, biomass and biochemical composition of the marine copepod Acartia clausi were studied using the relevant values of fresh unpreserved animals as reference. Acartia were collected in the southern parts of Saronicos Gulf in early May (16.5°C) and late June (21°C). Formalin was found to cause significant shrinkage of cephalothorax length, abdomen length and total length. The sex of individuals, as well as the temperature of seawater at the time of collection seem to influence dimensional losses. Females and animals collected at 16.5°C presented heavier losses. Dry weight is drastically reduced after formaldehyde preservation. Final losses are more severe for females and animals collected at 21°C. Two of the measured biochemical constituents, carbohydrates and neutral lipids, seem to be unaffected by formaldehyde. DNA and RNA although initially affected seem to be stabilized towards the end of the experimental period (30 days). The other biochemical parameters, viz proteins, total lipids and sugars, are profoundly affected by preservation.

1. The copepod Tisbe holothuriae was collected from the Saronicos gulf in the laboratory, under different combinations of temperature and salinity and as well as different types of food. 2. The content of C, H and N in females was measured. 3. As temperature increases and salinity declines from 38 parts per thousand, the content of C, H and N per individual decreases. 4. The type of food influences the carbon and hydrogen content per individual, while the nitrogen content is relatively constant. 5. The percentage content of C, H and N in females without egg sacs and females carrying their first newly formed egg sacs do not differ significantly.

The harpacticoid copepod Tisbe holothuriae was collected from Saronicos Gulf (Greece) and reared under constant laboratory conditions. In order to study the effects of food on the population dynamics, seven diets were tested: the seaweed Ulva; five artificial compound feeds: the liquid Fryfood® (Waterlife), a powder of Mytilus, yeast, soya and Spirulina, respectively; and a mixed diet consisting of Ulva and Fryfood. The life cycle parameters (mortality, sex ratio, generation time, offspring production) were measured, and the demographic variables [mean generation time (T), net reproductive rate (Ro), and intrinsic rate of natural increase (rm)] were determined. As to their efficiency regarding population dynamics, the diets ranked as follows: (1)Ulva+Fryfood, (2), Ulva, (3) Fryfood, (4)Mytilus, (5) soya, (6) yeast, and (7)Spirulina. In this order they cause a progressive increase of both larval mortality and generation time, a progressive decrease of sex ratio, number of offspring per egg sac, number of egg sacs per female and, consequently, of Ro and rm. The observed differences between diets were most pronounced with respect to offspring production. Of the compound diets, those containing animal extracts were more efficient than those containing vegetable materials. Ulva plays an important role in the nutrition of T. holothuriae, favouring offspring production as well as larval survival, development and pigmentation. Ulva in combination with Fryfood led to a greater copepodid survival and offspring production. This mixed diet proved to be the most favourable for rearing the Greek population of t. holothuriae, resulting in an efficient intrinsic rate of natural increase (rm=0.304) of the population. © 1991 Biologische Anstalt Helgoland.

1. The influence of temperature (14, 19, 24-degrees-C), salinity (26, 32, 38, 44 parts per thousand) and food type (artificial diets: Fryfood, Mytilus, Soya, Yeast, Spirulina) on the respiratory rate of Tisbe holothuriae has been studied. 2. Oxygen consumption decreased with decreasing temperature, but with a greater rate at supra- or subnormal salinities. 3. Multiple-regression analysis showed the quadratic effect of temperature and the linear effect of salinity to be the more important factors affecting respiration. 4. The food type also seems to exert an important effect on oxygen consumption. 5. A significant lowering of respiration was observed for all food tested when the animals were starved.