B. García

Growth and food intake models in Octopus vulgaris Cuvier (1797): influence of body weight, temperature, sex and diet

Multiple regression analysis was used to develop mathematical models applicable to the growth and food intake of Octopus vulgaris. The variables considered were: body weight (Bw: 175–3,500 g), temperature (T: 13–28 °C), sex (S: male = 0, female = 1) and diet (D: bogue fish = 0, crabs = 1). Growth and food intake may be succesfully expressed by means of the following equations: Ln (AGR + 14) = −2.0135 + 0.0895 Ln Bw + 0.5087 T − 0.0142 T2 + 0.2997 D (R2 = 71.79; ANOVA p < 0.0001) and Ln (AFR) = − 5.6577 + 0.5137 Ln Bw + 0.5266 T − 0.0132 T2 + 1.1135 D (R2 = 78.71; ANOVA p < 0.0001), where AGR: absolute growth rate, AFR: absolute feeding rate, Bw: body weight, T: temperature and D: diet. In our experimental conditions, sex did not affect growth or food intake. The optimum temperature for growth (17.5 °C) and food intake (20 °C) was independent of body weight. Growth and food intake were higher with the crab diet. Nevertheless, food efficiency was better for animals fed on fish (bogue). Maximum food efficiency was reached at 16.5 °C for both diets. When the temperature was above 23 °C, weight losses and mortality were recorded; the temperature at which this occurred depending on body weight and diet, so that smaller and bogue-fed individuals were more sensitive to increasing temperatures. O. vulgaris growth may provide optimum economic performance from 16 to 21 °C. This range is too narrow, considering the wide natural range (12–29 °C) in some Mediterranean areas. Therefore, O. vulgaris growth will be limited by seasonality of temperature or must be carried out with other systems (e.g. recirculation in closed systems with temperature control) for it to be economically viable.Multiple regression analysis was used to develop mathematical models applicable to the growth and food intake of Octopus vulgaris. The variables considered were: body weight (Bw: 175–3,500 g), temperature (T: 13–28 °C), sex (S: male = 0, female = 1) and diet (D: bogue fish = 0, crabs = 1). Growth and food intake may be succesfully expressed by means of the following equations: Ln (AGR + 14) = −2.0135 + 0.0895 Ln Bw + 0.5087 T − 0.0142 T2 + 0.2997 D (R2 = 71.79; ANOVA p < 0.0001) and Ln (AFR) = − 5.6577 + 0.5137 Ln Bw + 0.5266 T − 0.0132 T2 + 1.1135 D (R2 = 78.71; ANOVA p < 0.0001), where AGR: absolute growth rate, AFR: absolute feeding rate, Bw: body weight, T: temperature and D: diet. In our experimental conditions, sex did not affect growth or food intake. The optimum temperature for growth (17.5 °C) and food intake (20 °C) was independent of body weight. Growth and food intake were higher with the crab diet. Nevertheless, food efficiency was better for animals fed on fish (bogue). Maximum food efficiency was reached at 16.5 °C for both diets. When the temperature was above 23 °C, weight losses and mortality were recorded; the temperature at which this occurred depending on body weight and diet, so that smaller and bogue-fed individuals were more sensitive to increasing temperatures. O. vulgaris growth may provide optimum economic performance from 16 to 21 °C. This range is too narrow, considering the wide natural range (12–29 °C) in some Mediterranean areas. Therefore, O. vulgaris growth will be limited by seasonality of temperature or must be carried out with other systems (e.g. recirculation in closed systems with temperature control) for it to be economically viable.

Seasonal condition and body composition changes in sharpsnout seabream (Diplodus puntazzo) raised in captivity

Abstract Changes in biological indices (weight, length, gonadosomatic index, condition factor, hepatosomatic index, intraperitoneal fat ratio and fillet portion), and body composition were examined in sharpsnout seabream (30 to 500 g) maintained in culture for one and a half years. Growth was rapid during May–September, and slow from October to April. Gonadal development took place between August and October, and gonadosomatic index peaked in October (GSI: 1.14%). The condition factor, the hepatosomatic index and the intraperitoneal fat ratio varied (CF: 1.83–2.51, HSI: 0.80–2.47%, IPF ratio: 1.27–2.95%, minimum and maximum values, respectively), falling during the warmer months of the year (May–Oct). The fillet portion (the eviscerated fish with the head, fishbone and tail removed), represented a 55% of body mass. There were inverse correlations between relative fat and moisture contents associated with growth periods and sexual maturation (fat: 13.5–18.5%, moisture: 59.9–64.6%, minimum and maximum values, respectively), whereas proportions of minerals and protein were more stable (ash: 3.8–4.8%, proteins: 17.5–21.4%, minimum and maximum values, respectively).

Sensory evaluation of farmed sharpsnout seabream (Diplodus puntazzo)

The first attempts at applying aquacultural techniques to sharpsnoutseabream (Diplodus puntazzo) have proved very promising.One of the factors to keep in mind when analysing the viability of a speciesforindustrial farming is that of consumer acceptance of the product, a variablethat can be measured by sensory evaluation tests. To that end, 107 participantsfrom a number of work centres were assessed with hedonic sensory tests usingsharpsnout seabream samples. For reference purposes, the tasting also includedgilthead seabream samples. Participants were asked to fill out a questionnairethat included questions concerning their preferences for any one fish. Weanalysed the sensory attributes of both fish species using a hedonic scale, andalso their acceptability (disposition to purchase) to consumers. The resultsproved fairly encouraging with a view to sharpsnout seabream large-scaleproduction. All attributes tested in the sensory profile analysis werepositively rated. About 60% of the surveyed population would consider buyingsharpsnout seabream at a price similar to that of gilthead seabream (10∈),and 85% found it to be pleasing to the eye. Aside from flavour, its texture,juiciness and fat level are the most important appraisal attributes. Efforts toimprove the organoleptic characteristics of the species should focus mainly onthese attributes.