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Marine research at CNRFigure 5: Haematocrit values in Dicentrarchus labrax cultured in submerged (sub) andsurface (surf) cages. Reported are the result of the Student t-test: ∗ = p < 0.05,∗∗ = p < 0.01, no indications is reported when difference is not significant.the increased requirement of energy occurringduring stress conditions.Haematocrit value is also consistent withother parameters, showing significanthigher value (p ≤ 0.01) in surface cages inJune (Figure 5).In general haematocrit value rises in fishexposed to stress as a direct consequenceof the increase in hearth-beat and the needof higher oxygen uptake [12].The increase of lactate is used as a stressindex and is related to glycolysis anaerobicthat occurs when muscular activity isintense [30, 31], but statistical differenceswere not observed between cages.It is also important underline that in D.labrax reared in submerged cages all consideredparameters are maintained in therange of basal values reported in literatureon the contrary fish of surface cages oftenexceed this range.3.3 Immunological parametersThe non-specific or innate immune systemis the most important resistance mechanismin fish [32, 33] and some of itscomponents (e.g., lysozme, haemolytic andhaemagglutinating activity) are used as indicatorsof immunocompetence in fish exposedto stress [34, 35].As shown in Figure 6, fish of submergedcages showed significant higher values(p ≤ 0.01) in non specific haemolytic activity(SH50), in June and September.Lysozyme content was measured in differenttissues or organs (mucus, plasma andkidney) but higher and significant difference(p ≤ 0.05) was found in the mucus ofseabass cultured in submerged cage only inSeptember (Figure 7).Mucus lysozyme represents the first defencemechanism against foreign agents[32, 26].The detection of different immunologicaldefence ability lead us to suppose thatsubemergence could have a positive effect2155