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The aim of this study was to test the effect of copper supplementation in a formulated feed on the growth, feed efficiency, and nutritional composition of subadults Octopus vulgaris, with particular reference to the differences in the content of copper in the tissues (muscle, digestive gland, and hemolymph). Two formulated feeds were supplied to subadults octopuses kept individually for 56 days: Basal diet [11.6 mgCu/kg dry weight (dw)], and another feed with a similar composition but including a copper supplementation (copper diet: 115.2 mgCu/kg dw). No significant differences (P > 0.05) were detected in the respective growth rates (0.88% body weight/day), FE (79.5%–82.1%), proximate composition, hemolymph hemocyanin (1.6–1.8 mmol/L), hemolymph copper (0.19–0.20 mgCu/mL), or muscle copper levels (22.7–23.2 mgCu/kg dw). No significant changes were detected on proximate composition, hemocyanin and hemolymph, and muscle copper levels between animals fed formulated feeds and an initial group fed nat...

Growth, feed efficiency and proximate and lipid class composition of subadults Octopus vulgaris (788 ± 133 g; 18.5°C) fed formulated diets of low lipid (LL: 8 g kg−1) and high lipid levels (HL: 84 g kg−1) and each one of these with three different levels of glutamate supplementation (0, 5 and 20 g kg−1) were compared. All the animals accepted the diets with a survival of 100%. The addition of glutamate did not stimulate feeding rates in any of the assays (2.48–2.64 and 1.86–2.01%Body weight day−1 for LL and HL, respectively; P > 0.05). The best growth, feed efficiency and protein productive value were observed in the groups fed 5 or 20 g kg−1 glutamate supplementation at both lipid levels, with significant differences for LL diet (P

Spider crab, Maja brachydactyla, is a crustacean with interesting biological characteristics for intensive aquaculture. However, physiological studies are needed to establish the optimal conditions for its culture and maintenance. We analyzed the oxygen consumption response of spider crab to gradual hypoxia in relation to animal weight (W: 0.42–1.62 kg) and water temperature (T: 17.8–26.3 C), along with its ability to recover. Spider crab behaved as an oxygen regulator, maintaining its oxygen consumption constant until it reached critical oxygen saturation. This value varied between 24.1 and 53.3% oxygen saturation (42.4 ± 7.4% Sat.; 2.95 ± 0.43 mgO2/L), and significantly depended on the temperature (P < 0.01). The lethal oxygen saturation varied from 6.8 to 19.3% Sat. (12.57 ± 4.25% Sat.; 0.88 ± 0.29 mgO2/L) depending on temperature and body weight (P < 0.05). When oxygen levels were re-established after exposure to acute hypoxia, the animals recovered, oxygen consumption remaining above the routine value for up to 15–20 h. We suggest survival oxygen saturation levels for spider crab of between 100 and 65% in the experimental conditions of this study.

The rate of total ammonia excretion ( U , mg TAN d − 1 ) in relation to body weight ( W , 490–3460 g) and absolute protein feeding rate (APFR, 0.00–11.90 g d − 1 ) was studied in octopus ( Octopus vulgaris ). Using multiple regression analysis, the data obtained were fitted to the equation U = 13.91 + 0.07 W + 0.02 W × APFR, which explained 95% of the variance observed. According to this equation, there was a significant interaction between W and APFR ( W × APFR), the coefficient of W varying linearly with APFR ( b ' = 0.07 + 0.02APFR). When U was expressed as a function of body weight (Ur, mg TAN kg − 1 body weight d − 1 ), Ur basically varied as function of APFR, showing a value of 84 mg TAN kg − 1 body weight d − 1 when the octopus was not fed and 265 mg TAN kg − 1 body weight d − 1 when protein intake was 9 g d − 1 . U increases linearly with body weight from 10 to 57 g TAN kg − 1 feed dry matter d − 1 when APFR is 9 g d − 1 .

In experimental culture conditions in tanks, the effect of weight (W: 11–452 g) and temperature (T: 14–29°C) on the growth rate (SGR, % bw day−1) and maximum daily food intake (SFR, % bw day−1) in sharpsnout sea bream (Diplodus puntazzo) was studied. The possible combined effect of both independent variables (W and T) was also analyzed by multiple regression analysis, fitting the data to the equation Ln Y = Ln a + b Ln W + cT + dT2 + eT Ln W. Both SGR and SFR, and therefore feed efficiency (FE = SGR/SFR), were significantly influenced by the interaction between temperature and weight and may be expressed by means of the following equations: Ln SGR = −6.1705 + 0.5809T − 0.0087T2 − 0.0249T Ln W (\( R_{\text{adj}}^{2} \) = 0.949; ANOVA P < 0.0001); Ln SFR = −4.8257 + 0.4425T − 0.0063T2 − 0.0163T Ln W (\( R_{\text{adj}}^{2} \) = 0.964; ANOVA P < 0.0001).The results suggest that the optimum temperature for SGR and FE (TSGRopt and TFEopt), and the temperature at which the maximum SFR (TSFRmax) is reached, decreases with body weight, in accordance with the equations: TSGRopt = 33.297 − 1.435 Ln W; TFEopt = 29.332 − 1.890 Ln W; and TSFRmax = 34.941 − 1.304 Ln W, respectively. In this way, TSGRopt is 28.4, 26.7, and 24.7°C; TSFRmax is 30.5, 28.9, and 27.1°C and TFEopt is 22.9, 20.6, and 18°C for 30, 100 and 400 g body weight, respectively.

Spider crab ( Maja brachydactyla ) is considered a species of potential interest for intensive aquaculture, although physiological studies are necessary before the optimal conditions for its culture can be established. In this paper we develop equations to explain the oxygen consumption of the species as a function of weight ( W : 15–1414 g), temperature ( T : 13.5–27.9 °C), sex ( S ) and daily light–dark cycle (14L/10D to 10L/14D). The measurements were carried out over three days on single animals receiving one meal of mussels to satiation only on the first day of the measurements. The oxygen consumption values were divided into routine (MO 2routine ), post-prandial (MO 2sda ), maximum peak (MO 2peak ) and daily average between 0–24 h (MO 2; 0–24 h ), 24–48 h (MO 2;24–48 h ) and 48–72 h (MO 2;48–72 h ) post-feeding. Feeding led to an increase in oxygen consumption 1.7–7.3 (2.90 ± 1.25) times the routine value, with maximum peaks between 2 and 16 h post-feeding (7.94 ± 4.12 h) the effect lasting 10–24 h (19.80 ± 3.56 h). The different levels of oxygen consumption were expressed as lnMO 2routine = 0.206 + 0.837ln W + 0.302 T − 0.006 T 2 − 0.153S, lnMO 2sda = 0.294 + 0.736ln W + 1.372ln T − 0.171S, lnMO 2peak = 3.032 + 0.667ln W + 0.083 T − 0.158 S and lnMO 2; 0–24 h = 0.403 + 0.769ln W + 1.305ln T − 0.147 S , all to a statistically significant degree ( P

Four ongrowing cycles of common octopus (Octopus vulgaris), each with two stocking densities, were carried out in an offshore area in order to evaluate the effect of the following variables on growth (G, % body weight day−1) and mortality (M, % day−1): weight (W, 0.5–3.0 kg), temperature (T, 14–26 °C), stocking density (SD, 6–46 kg m−3), size dispersion, expressed as coefficient of variation (CV, 13–42%) and significant wave height (SWH: 0.4–1.2 m). The assays were performed in an 8 m3 stainless-steel floating cage divided into two compartments of 4 m3 each. For the range of temperatures considered (14–26 °C), G depended significantly on T and SWH, with maximum G values being obtained at 18.5 °C and with an important negative effect of SWH. M depended significantly on T, W and CV, mortality being minimal at 18 °C. The two other variables had an antagonistic effect, mortality increasing with greater size dispersion – suggesting that animals should be graded throughout the process – although the effect diminished as the sizes increased. The results point towards two alternatives for the commercial ongrowing of octopus under the particular conditions of the present study: (A) two ongrowing cycles of 3.5 months to reach a final weight of 2.5 kg or (B) one 5-month cycle to reach a final weight of 3.5 kg.

In the present study, the growth, feed efficiency and condition of Octopus vulgaris (0.58 to 1.02 kg; 17 to 21 °C) fed two formulated moist diets based on fish and prawn mixed with alginate (group A) or gelatin (group G) as binders, and a control diet based on a crab diet (group C) are compared. The animals showed a suitable degree of acceptance of both formulated diets, grew and produced faeces, with 100% survival in all groups. The best results were obtained with group C, where the animals showed a specific growth rate, specific feeding rate and feed efficiency of 1.61% BW/day, 4.67% BW/day and 33.95%, respectively. They were followed by the animals of group A (0.71% BW/day, 3.10% BW/day and 22.51%) and group G (0.22% BW/day, 1.31% BW/day and 16.06%). No significant difference was observed between groups C and A with regard to feed efficiency or protein productive value (PPV values of 49.01 and 28.49%, respectively), although differences were significant ( P

This study established different oxygen level categories (optimal, sub-optimal, dangerous and lethal) for Dentex dentex according to ventilatory frequency ( V f ) and oxygen consumption ( M O 2 ) in response to gradually decreasing dissolved oxygen levels for different fish masses (117–745 g) and water temperatures (13.9–28.1 °C). Initial and maximum ventilatory frequency ( V f0 and V fmax , respectively) and oxygen saturation at which ventilatory frequency was altered ( S Vf ) ranged from 31.3 to 71.3 beats/min, 58.0 to 129.7 beats/min and 48.1 to 81.7%, respectively. D. dentex maintained a constant M O 2 rate, until a critical oxygen saturation ( S crit ) was reached. The S crit and lethal oxygen saturation (LS50) ranged from 26.5 to 40.6% and 12.3 to 18.9%, respectively. V f0 , V fmax , S crit and LS50 were correlated positively and significantly with temperature, but only V fmax was correlated with body mass, pointing to a higher V f response in small than large fish. In the range of fish masses and temperatures tested, our findings suggest an optimal dissolved oxygen saturation of above 70–75% (constant V f and M O 2 ), a sub-optimal value of between 70 and 35% (altered V f but not M O 2 ), with anything below 35% being dangerous (altered V f and M O 2 ). We conclude that suitable oxygen levels for D. dentex are similar with respect to other species of interest in aquaculture.

Although the ongrowing of Octopus vulgaris shows great economic potential, to date, no commercially available diet exists so that trawled fish species of low economic value, which would otherwise be discarded, are used. Crustaceans form an important part of the diet of natural populations of O. vulgaris and, in captivity, they seem to be equally important for growth and survival. However, both the availability of crustaceans and their price seriously affect the profitability of O. vulgaris farming, particularly in the Mediterranean area. In the present study, we look at the optimal percentage of crabs and fish in the O. vulgaris diet, and different patterns of food distribution, taking into account biological and economic factors. For this, we used five experimental groups of octopus (only males), each of which followed a distinct pattern of feeding, representing five different diets: (i) crab provided every day (Group C); (ii) crab provided on 3 consecutive days followed by bogue for 1 day (Group 3C1B); (iii) crab and bogue provided on alternate days (Group 1C1B); (iv) crab provided on 1 day, followed by bogue for 3 days (Group 1C3B); and (v) bogue provided every day (group B). According to the macronutrient composition of the diet supplied and the quantity of crab and/or bogue consumed by each individual octopus, the mean macronutrient consumed each day was calculated, along with the gross energy and P/E ratio. The protein content of each diet was similar, 19–20% (wet substance), while the lipid content varied linearly from 0.79% in Group C to 6.11% in Group B. The optimal diet was reached in group 1C1B, with a growth rate of 1.98 ± 0.30% and a feeding efficiency of 39.35 ± 4.40%. The diet had a 2.65% lipid content and a P/E ratio of 31.68 g protein/MJ. However, from an economic point of view, the feeding strategy of group 1C3B seems to be the most adequate with a conversion index of 3 €/kg of octopus produced.

The dissolved oxygen level is an essential parameter for defining water quality in aquaculture. However, the optimal values of this gas can vary greatly depending on the species, body weight, or water temperature. In this study, different oxygen level categories (optimal, suboptimal, dangerous, and lethal) were established for Octopus vulgaris (0.18–2.20 kg; 15.5–27.4 °C) according to ventilatory frequency (Vf) and oxygen consumption (MO2) in response to gradually decreasing dissolved oxygen levels. Initial and maximum ventilatory frequency (Vf0 and Vfmax, respectively) and oxygen saturation at which ventilatory frequency is altered (SVf) showed mean values of 17.7±3.29 bts/min, 33.3±5.86 bts/min, and 62.8±15.94% (4.5±0.95 mgO2/l), respectively, and all variables were positively correlated with temperature (P