Differential growth and health situation of thicklip grey mullets (Chelon labrosus) fed on different diets

[EN] Aquaculture produces fish organisms for food, aquarium or scientific purposes, whose one of the major challenges have always been feed costs. Chelon labrosus has been proposed as an aquacultural species in the Basque Country. They may be promising due to their extensive and abundant distribution, omnivorous (and increasingly herbivorous) diet, eurythermal and euryhaline nature and gastronomical value. The AKURA project aims to design process for their farming, including a proper diet that avoids less sustainable and more expensive compounds like fishmeal. In this study, C. labrosus individuals were exposed to 4 different diets in order to determine the biometrical and histological effects of the different nutritional compositions, for which some indices were also calculated. This was related to the health condition of mullets. Feed containing a high amount of protein and lipids resulted in the highest growth rates for both length and weight. Fish fed on the lowest amount of protein had the lowest growth rates but presented the highest efficiency in utilising protein. High dietary carbohydrate concentrations were related to bigger livers and higher vacuolisation levels. Therefore, it was suggested that plant-based carbohydrates could be a suitable compound of feed for C. labrosus, but only if proteins were to be added. Good quality fats would also be necessary for being the principal energy source of fishes. Other methods like the biofloc system were proposed as well.[EUS] Akuakulturak oganismo itsastarrak ekoizten ditu elikagaigintza, akuario edo asmo zientifikoetarako, eta haren erronka nagusietako bat betidanik izan da pentsuen kostu altua. Euskal Herrian​ Chelonlabrosus akuikulturarako espezie bezala sartzea proposatu da. Etorkizun oparoa izan dezakete, besteak beste, haien banaketa zabala eta ugaria, dieta-eredu omniboroa (eta gero eta herbiboroagoa), hedapen euritermiko eta eurihalinoa eta balio gastronomikoa direla medio. AKURA proiektuak haien hazkuntzarako prozesu bat diseinatzea du helburu, horren barne arrain-irina bezala osagaiez hain sostengarri eta garestiak saihesten dituen dieta bat egonez. Ikerketa honetan,​ C. labrosus​enbanakoak 4 dieta ezberdinen bidez elikatu eta haietako bakoitzaren konposaketa nutrizionalak zituen eragin biometriko eta histologikoak aztertu ziren, horretarako zenbait indize ere kalkulatuz. Hori korrokoien osasun-egoerarekin erlazionatu zen. Proteinen eta lipidoen portzentai handiak zeuzkan pentsuari egokitu zitzaizkion luzera zein pisurako hazkunde-tasa altuenak.Proteina-kopuru txikiena ingeritu zuten arrainek hazkunde-tasa baxuenak aurkeztu zituzten,baina efizienteenak izan ziren proteina erabiltzeko orduan. Karbohidratoenkontzejatorri begetaleko karbohidratoak​ C. labrosus​entzako pentsuaren konposatu egokia izandaitezkeelairadokida,beti ere proteinak gehitzen badira.Kalitate oneko gantzak beharrezkoak izango lirateke ere arrainenenergia-iturri nagusia izateagatik. Biofloc sistema bezalako beste metodo batzuk ere proposatu ziren