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[EN] Currently, microalgae are used in fish diets, but their long-term growth effect is unknown. In this experiment, juvenile seabream specimens were fed with microalgae-enriched diets for three months, and then transferred to a microalgae-free diet for 10 months to assess long-term effects up to commercial size (≈27 cm and ≈300 g). The juvenile diets contained Nannochloropsis gaditana at 2.5 or 5% inclusion levels, either raw (R2.5 and R5 groups) or cellulose-hydrolyzed (H2.5 and H5 groups). The body length and weight were measured in 75 fish group-1 at commercial stage. The size, number, and fibrillar density of white muscle fibers and the white muscle transverse area were measured in nine fish group-1 at commercial stage. The results showed the highest body weight in H5 at commercial stage. The white muscle transverse area and the white fibres hyperplasia and density also showed the highest values in H5, followed by H2.5. In contrast, the highest hypertrophy was observed in C and R2.5, being associated with the lowest muscle growth in both groups. These results showed a microalgae concentration-dependent effect in hydrolyzed diets as well as an advantageous effect of the hydrolyzed versus raw diets on the long-term growth of Sparus aurata.

Common name Umbrina cirrosa specimens (mean weight 9.5 g, mean length 9 cm) were categorized in three densities (4, 9 and 15 kg m-3 ) in order to study the influence of stocking density on the growth, survival rate and feed conversion rates. The body and muscle parameters were studied at 0, 43 and 84 days of the experiment. After 43 days, the highest body parameters values (body length and weight) were found in specimens reared at 9 kg m-3 , followed by the specimens reared at 4 kg m-3 , showing the specimens reared at 15 kg m-3 the lowest growth. These results showed a negative effect of high density on the growth, being the intermediate density (9 kg m-3 ) the most favorable density for the growth at this stage. Muscle cellularity was different among the groups, being the hypertrophy values higher at high density of rearing (15 kg m-3 ) than at 4 and 9 kg m-3 . In contrast, the hyperplasia was higher at 4 kg m-3 than in the rest of densities. The group reared at 9 kg m-3 showed intermediate values of hypertrophy and hyperplasia. At 84 days of the experiment, the muscle cellularity was similar at 4 and 9 kg m-3 , this indicating a compensatory hypertrophic growth at 4 kg m3 . The highest values of body weight were reached at 9 kg m-3 . Moreover, the feed conversion rates and the percentage of survival rate were better at 9 than at 4 kg m-3 .

Seven-month-old shi drum (Umbrina cirrosa) specimens (mean weight 18.98 g, mean length 11.80 cm) were classified into 2 groups, a control group (C) fed a standard diet and a vegetal group (V) fed a diet with partial replacement of fish meal and fish oil by vegetable products. The body and muscle parameters were studied on days 0, 27, and 62 of the experiment. On day 27, body length was similar in both groups, but body weight was significantly lower in group V than in group C. The transverse area of the white muscle was also significantly lower in V than in C. Hypertrophy was higher in C than in V, whereas hyperplasia was higher in V than in C. On day 62, the body parameters showed similar results to those found on day 27. Muscle cellularity was different from that found on day 27, since hypertrophy was higher in V than in C and hyperplasia was higher in C than in V. The feed conversion rate and specific growth rate were similar in both groups, but the daily intake rate was lower in V than in C. Therefore, it seems that the percentage of vegetables in the vegetal feed was excessively high and this caused less acceptance by the fish. The hepatosomatic, viscerosomatic, and intestinal length indices were similar in both groups. Survival was nearly 100% in both groups.

Seven-month-old shi drum (Umbrina cirrosa) specimens (mean weight 18.98 g, mean length 11.80 cm) were classified into 2 groups, a control group (C) fed a standard diet and a vegetal group (V) fed a diet with partial replacement of fish meal and fish oil by vegetable products. The body and muscle parameters were studied on days 0, 27, and 62 of the experiment. On day 27, body length was similar in both groups, but body weight was significantly lower in group V than in group C. The transverse area of the white muscle was also significantly lower in V than in C. Hypertrophy was higher in C than in V, whereas hyperplasia was higher in V than in C. On day 62, the body parameters showed similar results to those found on day 27. Muscle cellularity was different from that found on day 27, since hypertrophy was higher in V than in C and hyperplasia was higher in C than in V. The feed conversion rate and specific growth rate were similar in both groups, but the daily intake rate was lower in V than in C. Therefore, it seems that the percentage of vegetables in the vegetal feed was excessively high and this caused less acceptance by the fish. The hepatosomatic, viscerosomatic, and intestinal length indices were similar in both groups. Survival was nearly 100% in both groups., Verrugatos (Umbrina cirrosa) de 7 meses (peso medio de 18.98 g, longitud media de 11.80 cm) fueron clasificados en 2 grupos: un grupo control (C), que fue alimentado con una dieta estándar, y un grupo vegetal (V), que fue alimentado con una dieta con reemplazo parcial de harina y aceite de pescado por productos vegetales. Los parámetros corporales y musculares se estudiaron en los días 0, 27 y 62 del experimento. En el día 27, la longitud corporal fue similar en ambos grupos, pero el peso fue significativamente menor en el grupo V que en el C. El área transversa del músculo blanco fue significativamente menor en V que en C. La hipertrofia fue mayor en C que en V, mientras que la hiperplasia fue mayor en V que en C. En el día 62, los parámetros corporales mostraron resultados similares a los encontrados en el día 27. La celularidad muscular fue diferente a la encontrada en el día 27, de manera que la hipertrofia fue mayor en V que en C y la hiperplasia fue mayor en C que en V. La tasa de conversión de alimento y la tasa específica de crecimiento fueron similares en ambos grupos, pero la tasa diaria de alimentación fue menor en V que en C. Así, parece ser que el porcentaje de vegetales en la dieta vegetal fue excesivamente alto y ello causó menor aceptación por los peces. Los índices hepatosomáticos, digestosómaticos e intestinales fueron similares en ambos grupos. La supervivencia fue próxima al 100% en ambos grupos.

A 90-d feeding trial was conducted in which five groups of gilthead seabream (11.96 g initial body weight) were fed with a microalgae-free diet (control group, C) or four diets containing the microalgae Nannochloropsis gaditana at two inclusion levels (2.5% or 5%), either raw (R2.5 and R5 batches) or cellulose-hydrolyzed (H2.5 and H5 batches), to study their effect on the body and muscle growth. At 40 days, the highest values of body length and weight were reached in R5 group, but at 64 and 90 days, these were reached in R2.5. However, feed conversion rate, specific growth, daily intake, and survival (100%) were similar in all the groups. The acquisition of a discoid body shape was accelerated depending on the inclusion level of N. gaditana in the diets. Moreover, H5 diet affected the fish geometric morphology compared to R5 diet. The white muscle transverse area was similar in all groups at 40 days, with the exception of H2.5 group, which showed the lowest area. At day 90, C and R2.5 displayed the highest muscle growth, attributable to increased hyperplasia in C, and higher hypertrophy in R2.5. However, the highest proportion of small and medium fibers was observed in R5 and H5.

A 90-d feeding trial was conducted in which five groups of gilthead seabream (11.96 g initial body weight) were fed with a microalgae-free diet (control group, C) or four diets containing the microalgae Nannochloropsis gaditana at two inclusion levels (2.5% or 5%), either raw (R2.5 and R5 batches) or cellulose-hydrolyzed (H2.5 and H5 batches), to study their effect on the body and muscle growth. At 40 days, the highest values of body length and weight were reached in R5 group, but at 64 and 90 days, these were reached in R2.5. However, feed conversion rate, specific growth, daily intake, and survival (100%) were similar in all the groups. The acquisition of a discoid body shape was accelerated depending on the inclusion level of N. gaditana in the diets. Moreover, H5 diet affected the fish geometric morphology compared to R5 diet. The white muscle transverse area was similar in all groups at 40 days, with the exception of H2.5 group, which showed the lowest area. At day 90, C and R2.5 displayed the highest muscle growth, attributable to increased hyperplasia in C, and higher hypertrophy in R2.5. However, the highest proportion of small and medium fibers was observed in R5 and H5

The muscle and textural parameters were analyzed in four myotome zones (epaxial upper, hipoaxial upper, epaxial bottom, and hipoaxial bottom) in seven diploids (D) and seven triploids (T) turbot specimens. Diploid specimens showed the highest values of the size and number of white fibers in the epaxial zones, being such values higher in female than male specimens. In triploid specimens, the highest fibers sizes were found in the upper zones (epaxial and hipoaxial), whereas the lowest number and density of fibers were found in the epaxial upper zone. In this latter group (T), the lowest fibers sizes were found in female specimens, whereas the rest of the parameters were usually higher in female than male specimens. When comparing both groups, the hypertrophy was higher in T than D in all zones. In both ploidy groups, the highest textural values were usually observed in the upper epaxial fillet, being slightly higher in female than male specimens. The values of standard length, total weight, gonad weight, gonadosomatic index and gutted weight were higher in female than male specimens in both groups (D and T)

Sparus aurata specimens of 11 months of age (mean weight: 90.2 g, mean length: 18.3 cm) were classified in two diet groups: one control group was fed with conventional diet, and one experimental group was fed with an organic diet. The body and muscle parameters were studied at 0, 41 and 71 days of the experiment. The results showed the highest values of body length and weight as well as the best biological feed conversion rates in the organic group. The transverse area of white muscle, the hyperplasia and the muscle fibres density were also higher in the organic than in the conventional group (P>0.05). In contrast, hypertrophy was greater in the conventional than in the organic group (P<0.05). Survival was 100% in both groups. In conclusion, the organic feeding regime was more favourable for growth than conventional feeding.

Sparus aurata specimens of 11 months of age (mean weight: 90.2 g, mean length: 18.3 cm) were classified in two diet groups: one control group was fed with conventional diet, and one experimental group was fed with an organic diet. The body and muscle parameters were studied at 0, 41 and 71 days of the experiment. The results showed the highest values of body length and weight as well as the best biological feed conversion rates in the organic group. The transverse area of white muscle, the hyperplasia and the muscle fibres density were also higher in the organic than in the conventional group (P>0.05). In contrast, hypertrophy was greater in the conventional than in the organic group (P<0.05). Survival was 100% in both groups. In conclusion, the organic feeding regime was more favourable for growth than conventional feeding.

Shi drum (Umbrina cirrosa L.) larvae were maintained under three photoperiod regimes: a natural photoperiod regime (16L:8D), continuous light (24L) and equal durations of light and dark (12L:12D) from the end of the vitelline phase to the end of the metamorphosis. Muscle and body parameters were studied at hatching and at 4, 10, 14, 39 and 55 days post hatching (dph). During the vitelline phase, the total body length growth was scarce, whereas the muscle grew significantly, being the hypertrophy of the main mechanism involved. Both the total body length and the hypertrophy were significantly greater at 16L:8D than in the rest of photoperiod regimes. At 10 and 14 dph, the greatest body length was reached at 16L:8D, followed by the 24L group, showing the 12L:12D group the lowest values. At 14 dph, the hypertrophy and hiperplasia were also higher at 16L:8D than in the rest of groups. At 39 dph, the highest values of body length were reached in both 16L:8D and 12L:12D regimes, this latter group reaching the highest values of hypertrophy, thus showing a compensatory growth when comparing with the previous stages. The end of the metamorphosis took place at 50–55 dph in all the groups, with 2.7–3.1 cm of body length (P > 0.05). At this stage, the transverse area of the White muscle was similar among the groups, but the greatest hypertrophy was reached at 16L:8D, whereas the highest hyperplasia was reached at 24L.

Three groups of shi drum Umbrina cirrosa L. were reared with different photoperiod regimes: 24L, 12L:12D and 16L:8D (natural photoperiod) during the larval period and then all of them were transferred to a natural photoperiod. At 11.8 and 20 months of age, the body growth and the muscle parameters reached the highest values in the 24L and 12L:12D groups. The 16L:8D group showed the lowest growth. When comparing 24L with 12L:12D, the highest number of white fibres was found in the 24L group, whereas the greatest fibres size was reached in the 12L:12D group. Commercial size (28-30 cm; 290-340 g) was reached at 20 months of age in the 24L and 12L:12D groups, but at 23 months in the 16L:8D group. When comparing the three groups at the commercial stage, the larval photoperiod effect was still observed, such that the highest fibres number was again found in the 24L group, whereas the greatest fibres size was reached in the 12L:12D group. The highest values of textural hardness were observed in the 16L:8D and 24L groups. A nutritional analysis was carried out in the 16L:8D group, which showed the following percentage values: 2.66, 21.2, 74.4, and 1.46 of fat, protein, moisture and ash, respectively.