Untitled - CNR

Fishery and Sea ResourcesNevertheless, the rearing techniques fromhatchlings (0 day old paralarvae) to thebenthic stage are not yet well established,limiting the development of its culture[3, 5, 10]. Therefore, in order to achievea profitable long term commercial productionof O. vulgaris, it is necessary to focusthe efforts on growth and maintenance ofsub-adult wild individuals, for which anadequate feeding development programmeis necessary.Several formulated artificial diets havebeen tested for feeding sub-adult individuals,but the cephalopod growth rates onthose diets have been poor compared withnatural diets [11, 12, 13, 14, 15, 16, 17],and this may be due to the lack of palatabilityof the diets or to their poor nutritionalcomposition. However, some researchgroups have recently obtained formulasthat octopus find acceptable and which producesignificant growth [17, 18].On the other hand the growth and feed efficiencyof O. vulgaris, fed on natural diets,can vary widely depending on the exactspecies used as a diet [19, 20].The aim of this study was to investigate theinfluence of diet on growth and biochemicalprofile of O. vulgaris fed with naturaldiets. In order to develop an optimalfeeding programme, which could improvenutritional value of cephalopods, these resultsrepresent important basic knowledgefor the future development of feeding techniquesfor O. vulgaris.2 Materials and methods2.1 Experimental rearing of O.vulgarisThe feeding trial was conducted at Institutefor Coastal Marine Environment-CNRof Taranto, Italy. Octopus juveniles werecaught in the coastal waters of Gulf ofTaranto (Ionian Sea, Italy) by using trapnets. In the laboratory, each animal wasweighed with a professional balance to thenearest g. Before the experiments started,the octopuses were kept together, for 24h,in a tank of 7 m 3 with an open seawaterflow (37.5-39.0 g·L −1 ) system.During the experimental period, the octopuses,weighing 500–650 g, were keptapart both to avoid cannibalistic behaviourand for an exact determination of food intake.For this reason, the octopuses wereplaced in cages of 1 cm mesh size and 2.5m 3 capacity, having an open recirculatingwater system, so that dissolved oxygen wasmaintained at above 90% saturation.In order to reproduce its natural habitat,in each tank was placed a PVC tube asrefuge. The females were rejected, in orderto avoid reproductive processes, suchas gonad maturation, which influences thephysiological state of the animals. Thephotoperiod, water temperatures (18±2°C)and salinity (38±2 g·L −1 ) with a diurnalvariation were natural.2.2 Experimental design offeeding treatmentsThe feeding treatments were conducted inthe laboratory during the spring months(2008). Octopuses were divided in threeexperimental groups, each group consistedof six animals, each animal was kept individuallyin a cage. Each group representeda different feeding regime, and all diet hasbeen composed by natural preys. The experimentaldiets were assayed in a feedingtrial lasting 30 days.Diet group I, fed on 80% crab Carcinusmediterraneus, 15% bogue fish Boops2032