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Systematic granulomatosis is a chronic disease that affects the majority of farmed meagre (A. regius). Nutritional imbalances and overcrowding can increase the risk to suffer oxidative stress, and consequently impact the incidence of granulomatosis. In order to evaluate this, juvenile meagre were fed five isolipidic (16.7 %) and isoproteic (49.6 %) fish meal and fish oil-based feeds prepared by adding different levels of vitamin C, minerals (Mn, Zn, Se) with constant vitamin E and K (300 and 35 mg kg-1, respectively): Diet KEC (100 mg kg-1C), Diet KEC+Mn/Zn/Se (100 mg kg-1C, 40 mg kg-1Mn, 200 mg kg-1Zn, 1.5 mg kg-1Se), Diet KECC (600 mg kg-1C), Diet KECCC (1,200 mg kg-1C), Diet KECCCC (3,200 mg kg-1C). All diets were tested at 3.20 kg m-3, but diets KECC and KECCCC was also tested at 6.20 kg m-3. Growth performance was only affected by stocking density, being lower at high density. Percentage of fish with granulomas was significantly lower in fish fed with the highest dietary vitamin C contents (KECCC and KECCCC) at low density. TBARS content was correlated with the percentage of granulomas in liver (R2=0.9439, y=0.003x-0.1242) denoting the involvement of an imbalance oxidative status in the appearance of granulomas. The present results show that high levels of vitamin C (1,200-3,200 mg kg-1C) and low stock density (3.20 kg m-3) favours the growth of juvenile meagre, reducing the lipid peroxidation indicators and decreasing the incidence of granulomas, which confirms that this pathology is mostly triggered by deficiency of antioxidant nutrients, particularly vitamin C.

Five isoproteic (54.8%) and isolipidic (24.1%) microdiets, which varied in their docosahexaenoic acid (DHA) content (0.25%, 0.75%, 1.64%, 1.99% and 3.17%; dw), were manufactured to determine its effects on longfin yellowtail Seriola rivoliana larvae in terms of fish biological performance, whole body fatty acid profile and incidence of skeletal anomalies from 30 dah (11.31 ± 1.79 Total Length, TL) to 50 dah (19.80 ± 0.58 mm TL). The inclusion of dietary DHA up to 3.17% (dw) improved larval resistance to air exposure, although DHA did not significantly affect fish final growth or final survival. Indeed, high levels of dietary DHA (1.99% and 3.17%, dw) tended to increase the incidence of skeletal anomalies in S. rivoliana larvae, albeit no significant differences were observed. Furthermore, the occurrence of severe anomalies such as kyphosis and lordosis, was mainly associated to the larvae fed the highest levels of dietary DHA. In terms of survival, increasing dietary DHA levels did not significantly affect longfin yellowtail survival rate, despite a tendency for enhanced survival. The results of the present study proved that the inclusion of dietary DHA in inert diets up to a 3.17% (dw) and a DHA/EPA ratio above 3.1 increased the final survival and stress resistance in S. rivoliana larvae.

The present study aimed to evaluate the effect of the supplementation of different crab zoeas to enriched Artemia basal diet for Octopus vulgaris paralarvae during the first month of life. Paralarvae were fed using enriched Artemia nauplii alone and Artemia co-fed either first zoea stages of Grapsus adscensionis or Plagusia depressa. The experiment was carried out over a period of 28 days, in 0.12 m3 tanks with a flow-through rearing system. Growth in dry weight as well as mantle length and width were assessed weekly. Additionally, prey and paralarvae fatty acid composition and digestive gland (DG) histology were evaluated. Addition of low amounts of crab zoeas (approx. 100 indv. L−1 day−1) provided during critical life stages of O. vulgaris proved to be good enough to improve paralarvae growth and survival in comparison with those fed exclusively on enriched Artemia. These results were supported by the finding of a higher number of glycoprotein absorption vacuoles in the DG from paralarvae co-fed crab zoeas, suggesting a higher feeding activity. In addition, fatty acid analysis of crab zoea showed that these are good sources of dietary arachidonic and eicosapentaenoic acids during the octopus planktonic life stage, whereas the low docosahexaenoic (DHA) content suggests the use of additional DHA sources or higher zoea densities to meet paralarvae nutritional demand to carry out a successful metamorphosis to benthic life.

The objective of this study was to evaluate three products derived from krill as sources of essential fatty acids, protein and, particularly, phospholipids in microdiets for larval gilthead seabream (Sparus aurata). Their effect on larval performance, biochemical composition and histological development was investigated. The addition of krill phospholipids, rich in highly unsaturated fatty acids, improved larval sea bream growth in terms of weight and length, enhanced hepatic utilization of dietary lipids and reduced the incidence of enterocyte injuries. These results confirm the higher nutritional value of marine phospholipids for the early development of marine fish larvae in comparison with soybean phospholipids.