Evaluation of spawning induction, egg incubation, and larval rearing of sea bass (Dicentrarchus labrax) in groundwater and seawater resources through different water management systems

Abstract

This study evaluated the viability of using groundwater (GW) compared to seawater (SW) in European sea bass (Dicentrarchus labrax) aquaculture. Wild broodstock were captured 2 months before spawning and acclimated to tanks with either SW or GW 1 week prior. Females received HCG injections in both water types. Fertilized eggs were collected into six conical tanks supplied with SW or GW. At 7 days post-hatch (dph), larvae were transferred to 12 rearing tanks with SW or GW, using either flow-through or static water systems (three replicates per treatment). Growth performance and survival were monitored up to 60 dph. The results revealed that spawning induction of European sea bass broodstock failed in GW while succeeded with egg fertilization and hatchability up to 97 ± 1% in SW. Hatching was 96 ± 1% for the fertilized eggs transferred from SW to GW incubators. However, the newly hatched larvae suffered high mortality up to 7 dph, which gradually decreased with the start of exogenous feeding. During the period from 7 to 60 dph, larvae and post-larvae showed normal viability and survival with either flow-through or static water systems in SW and GW. At the end of the experiment, the results indicated that water sources in combination with the water-rearing systems significantly affected post-larvae performance. Larval survival was significantly higher in both GW systems (static: 88.8 ± 2.1%, flow-through: 89.9 ± 5.6%) and in the static SW system (84.15 ± 2.8%) compared to the flow-through SW system (70.4 ± 5.8%). Moreover, the final length of larvae at 60 dph was significantly higher in the static GW system (2.27 ± 0.09 cm). In addition, larvae reared in static GW had higher final weight (140. 00 ± 4.24 mg). Total protein and total lipid contents were significantly higher in larvae reared in GW than those reared in SW for both water systems. The study suggested a static GW system for European sea bass larval rearing starting from 7th dph onwards to achieve better larval quality and higher survival. Future research is needed to enhance GW with new technologies to accommodate D. labrax–induced spawning and newly hatched larval rearing.