Osobine obrade soma (silurus glanis) iz spoljašnjih protočnih i unutrašnjih recirkulacionih uzgojnih jedinica

Wels (European) catfish, Silurus glanis L., is a high valued fish of European pond aquaculture. Recently, the quality of its flesh, suitability of very good growth performance in high stocking densities and ability to ingest artificial pelleted diets, led to its wider utilisation under conditions of intensive warm-water farming units including recycling systems. The evaluation of processing yields was performed using fish cultured in two different farming units – (1) outdoor pond aquaculture system (PAS) with flow-through regime (24.6±0.2°C) and (2) the indoor tank aquaculture system (TAS) with recirculation regime (26.0±1.0°C). Despite no significant differences appeared in their processing traits, the condition coefficients (based on eviscerated body weight) were significantly higher in PAS fish. However these coefficients were almost identical when calculated from the total weight of fish. Visceral, ventral and dorsal fat deposits were significantly higher in TAS fish in comparison to PAS fish and also in females as compared to males.Evropski som, Silurus glanis L., je visoko vredna riba koja se gaji u Evropskim rubnjacima. U poslednje vreme, kvalitet njegovog mesa, pogodnost veoma dobrih performansi rasta u velikoj gustini nasada, kao i sposobnost korišćenja peletirane veštačke hrane, dovela je do povećanog obima gajenja u intenzivnim toplovodnim uzgojnim jedinicama, uključujući i recirkulacione sisteme. Procena prinosa prerade je obavljena ispitivanjem prerađenog proizvoda ribe gajene u 2 različita sistema: (1) ribnjačkom jezeru na o tvorenom (PAS) sa protočnim režimom (24.6±0.2°C) i (2) u tankovima u zatvorenom sistemu (TAS) sa recirkulacionim režimom (26.0±1.0°C). Iako nije bilo značajnih razlika u osobinama obrade, koeficijent kondicije (zasnovan na telesnoj masi bez viscere) je bio značajno viši kod riba iz PAS sistema. Ovi su koeficijenti bili gotovo identični kada bi se preračunali iz ukupne težine ribe. Visceralni, ventralni i dorzalni depoziti masti su bili značajno viši u riba iz RAS sistema u odnosu na ribe iz PAS, kao i kod ženki u poređenju sa mužjacima

Le développement durable : un défi pour l'aquaculture marine en Méditerranée

L'aquaculture marine méditerranéenne s'est développée à un rythme soutenu (25 % par an) et elle représente une réelle alternative à la pêche. Aujourd'hui, elle doit prendre en compte le développement durable (DD) qui constitue un véritable défi pour cette aquaculture " entrepreneuriale ". La question est donc de savoir si les entreprises aquacoles peuvent relever ce défi et avec quelles conséquences. Afin de répondre à cette question, des enquêtes ont été menées en Méditerranée. Elles visaient : i) à établir une typologie en fonction des logiques d'exploitation, des pratiques observées et des contraintes rencontrées ; et ii) à étudier les représentations des acteurs de la filière vis-à-vis du DD. Elles confirment que les entreprises sont dans une logique dominée par les contraintes de marché, mais montrent aussi que leurs pratiques ne sont, pour le moment, pas trop éloignées du concept de DD. Cependant, la participation des aquaculteurs au DD passe par la mise en place d'innovations, en particulier organisationnelles, et par la constitution d'un métier qui permettrait de mettre en oeuvre l'action collective nécessaire. (Résumé d'auteur

Is total serum protein a good indicator for welfare in reared sea bass (

Reared sea bass were submitted to six stressful situations: hyperoxia with or without hypercapnia, increased stocking density in an open flow or recirculating system, transfer to another tank and nodavirus injection. The potentially negative impact of these factors on the lives of sea bass was investigated by measuring 9 water parameters and 19 fish parameters including total serum protein (TSP). TSP has already been used to evaluate stress. The present study investigates data of previous and new experiments, concentrating on the potential use of TSP as a routine indicator to assess welfare in sea bass reared on fish farms. In the current experiment, oxygen and carbon dioxide were seen to affect levels of TSP, but alterations were too erratic to enable proper comparison, probably because they are normal components of the fish environment and become toxic only by dose increase. TSP decreased when stocking density increased. After transfer to another tank, TSP decreased to 14% for three weeks and then increased during the fourth week through compensative overproduction, before returning to normal levels after 2 months. The results confirmed that transfer is an important stress factor for fish, with cumulative effects for successive transfers. TSP alteration of nodavirus-injected fish depends on the type of symptoms, which can be divided into 3 groups: (i) dying fish, in which TSP increased sharply due to over-production of protein involved in non-specific defences and inflammation, then decreased dramatically before death; (ii) whirling fish, a group that included both fish that later died, in which TSP decreased, and fish that subsequently survived, in which TSP increased due to development of specific immunity; and (iii) asymptomatic fish, in which TPS was similar to control levels and which were probably insensitive to nodavirus and/or had developed defences. In this paper, different mechanisms of TSP alteration are proposed and the interest of TSP as a field parameter is discussed. TSP is a non-destructive parameter that is robust, easy to measure everywhere and cheap, representing a suitable way of monitoring the overall welfare of fish by its regular increase. It can be used only as a “warning” of poor rearing conditions, however, and further investigations would be needed to identify the specific stress or health disorder

Effect of dietary water content on European sea bass (Dicentrarchus labrax) growth and disease resistance

The effect of dietary water content on Dicentrarchus labrax growth parameters and resistance to Vibrio anguillarum infection was investigated using commercial pellets with identical energy contents and different moisture levels. The first experiment hypothesis was that moisturizing pelleted ration can have an impact on Dicentrarchus labrax growth performance by the osmoregulation energy cost reduction. In a second time, the experiment explores the effect of water addition in pellets on the fish resistance to a disease. A specific device was built to uniformly moisturize dry pellets to different moisture levels, i.e. 8%, 20%, 40% and 60%. After an acclimation period and a 54-day rearing period, the control fish had grown from 72.7 +/- 17.9 g to 133.3 +/- 29.4 g. No significant differences were recorded for fish growth parameters. After the growth period, the tagged fish were mixed and challenged by bath exposure to live Vibrio anguillarum in triplicate. After 7 days, mortality was significantly lower in the group of fish fed with pellets containing 60% water. Adding water to Dicentrarchus labrax feed did not affect fish growth parameters but increase its resistance to a Vibrio anguillarum infection. The moisturizing process could be used to add specific compounds (such as probiotics or vitamins) to pellets just before fish feeding and could have a positive effect on fish rearing

Effect of oxidation–reduction potential on performance of European sea bass (Dicentrarchus labrax) in recirculating aquaculture systems

The direct impact of oxidation–reduction potential (ORP) on fish welfare and water quality in marine recirculating aquaculture systems (RAS) is poorly documented. In this study, the effects of the fish size (S1, S2, S3) and ORP level (normal, four successive levels) on the performance of European sea bass (Dicentrarchus labrax) were investigated. Three size fish were distributed into two RAS (RAS and RAS O3). Ozone was injected into RAS O3 to increase the ORP level. The ORP was stabilized to four successive levels: 260–300, 300–320, 320–350, and 300–320 mV in fish tanks during four periods (P1–4). At the last day of each period, the hematological parameters, plasma protein and mortality of sea bass were analyzed. Two-way ANOVA revealed that several hematological parameters, including pH, hematocrit, concentrations of oxygen, carbon dioxide, glucose (Glu), ionized calcium, kalium, and hemoglobin, were significantly influenced by the increased ORP levels over the experimental period. The alteration in blood Glu and plasma protein concentration showed that ORP around 300–320 mV started to stress sea bass. Once the ORP exceeded 320 mV in the tanks during the P3 period, mortality occurred even when total residual oxidants/ozone-produced oxidants was only 0.03–0.05 mg L−1 in the fish tanks. At the same time, plasma protein decreased notably due to appetite depression. After the decrease in ORP during the P4 period, mortality continued. In conclusion, the results strongly suggest that for European sea bass in RAS, the ORP should not exceed 320 mV in the tanks. Once ozonation damaged fish, the effect seemed to be irreversible. However, how ORP affected related hematological parameters still need the further investigations