Ontogenic effects of early feeding of sea bass (Dicentrarchus labrax) larvae with a range of dietary n-3 HUFA levels on the functioning of PUFA desaturation pathways

Four replicated groups of sea bass (Dicentrarchus labrax) larvae were fed diets containing an extra-high level of highly unsaturated fatty acids (HUFA) (XH; 3·7% EPA + DHA), a high level of HUFA (HH; 1·7 %), a low level of HUFA (LH; 0·7%) or an extra-low level of HUFA (XLH; 0·5%) from day 6 to day 45 (experiment 1; XH1, HH1, LH1, XLH1). After a subsequent 1-month period feeding a commercial diet (2·7% EPA + DHA), the capacity of the four initial groups to adapt to an n-3 HUFA-restricted diet (0·3% EPA + DHA; R-groups: XH2R, HH2R, LH2R, XLH2R) was tested for 35 d. Larval dietary treatments had no effect on larval and juvenile survival rates. The wet weight of day 45 larvae was higher in XH1 and HH1 (P < 0·001), but the R-juvenile mass gains were similar in all treatments. D-6-desaturase (D6D) mRNA level was higher in LH1 and XLH1 at day 45 (

Influence of temperature, ammonia load and hydraulic loading on the performance of nitrifying trickling filters for recirculating aquaculture systems

[EN] In recirculating aquaculture systems, performance of nitrifying biofilters for total ammonia nitrogen (TAN) removal from the culture water and thus minimizing eutrophication depends on numerous elements of design. In this article the combined effect of three of these process parameters (temperature, hydraulic loading and TAN load) is evaluated. Ammonia removal rates (N-TAN divided by biofiltration area and day) were measured for every combination of five different temperatures, three different hydraulic loadings and three different ammonia loads. Every one of the process parameters were influential on nitrification rates and the lowest process parameters values corresponded with significantly lower N-TAN removal rates. A significantly higher mean N-TAN removal rate (0.241 gN-TAN removed m¿2 day-1) was found for the combination of the highest water temperature (27¿°C), the highest hydraulic loading (11 m3¿m¿2¿h-1) and the highest TAN load (9 gTAN m-3 day-1), suggesting a positive synergy of the three process parameters on the achievement of greater biofilter performances.This research work was made possible by the funding of the national project "Design of a recirculating aquaculture system for aquaculture plants (2011-2014)" by Ministry of Science and Innovation, Spain.Godoy-Olmos, S.; Martínez-Llorens, S.; Tomas-Vidal, A.; Monge-Ortiz, R.; Estruch-Cucarella, G.; Jover Cerda, M. (2019). Influence of temperature, ammonia load and hydraulic loading on the performance of nitrifying trickling filters for recirculating aquaculture systems. Journal of Environmental Chemical Engineering. 7(4):1-8. https://doi.org/10.1016/j.jece.2019.103257S187

Reproduction and respiration of a climate change indicator species: effect of temperature and variable food in the copepod Centropages chierchiae

The abundance of the calanoid copepod Centropages chierchiae has increased at the northern limits of its distribution in recent decades, mainly due to oceanic climate forcing, suggesting this as a key species in monitoring climate change. Laboratory experiments were conducted to study the combined effect of temperature, food type and concentration on the egg production rate (EPR) and hatching success (HS) of C. chierchiae. Females were fed on two monoalgal diets (Gymnodinium sp. and Phaeodactylum tricornutum) at two food concentrations and at three different temperatures (13, 19, 24C). Respiration rates of both genders were measured at four different temperatures (8, 13, 19, 24C). EPR was significantly different between temperatures and food concentrations, the maximum EPR being attained when the copepods were exposed to high food levels and at 19C. Prey type significantly influenced EPR; feeding on P. tricornutum resulted in higher egg production than Gymnodinium sp. HS was significantly lower at 13C than at 19 and 24C and higher with Gymnodinium sp. Respiration rates were sex independent and increased exponentially with temperature. To maintain basal metabolism, the minimum food intake of P. tricornutum ranged between 0.4 and 1.8 g C and for Gymnodinium sp. between 0.03 and 0.13 g C. Food intake was always higher than the metabolic demands, except for the highest temperature tested (24C). The present results confirm the sensitivity of C. chierchiae to temperature variations and may help in understanding the successful expansion of its distribution towards northern latitudes.Portuguese Science and Technology Foundation (FCT) [PTDC/MAR/098643/2008, PTDC/MAR/111304/2009, PTDC/MAR/0908066/2008]; FCT [SFRH/BD/28198/2006]; [SFRH/BPD/38332/2007

Estimation of Fish Biomass Using Environmental DNA

Environmental DNA (eDNA) from aquatic vertebrates has recently been used to estimate the presence of a species. We hypothesized that fish release DNA into the water at a rate commensurate with their biomass. Thus, the concentration of eDNA of a target species may be used to estimate the species biomass. We developed an eDNA method to estimate the biomass of common carp (Cyprinus carpio L.) using laboratory and field experiments. In the aquarium, the concentration of eDNA changed initially, but reached an equilibrium after 6 days. Temperature had no effect on eDNA concentrations in aquaria. The concentration of eDNA was positively correlated with carp biomass in both aquaria and experimental ponds. We used this method to estimate the biomass and distribution of carp in a natural freshwater lagoon. We demonstrated that the distribution of carp eDNA concentration was explained by water temperature. Our results suggest that biomass data estimated from eDNA concentration reflects the potential distribution of common carp in the natural environment. Measuring eDNA concentration offers a non-invasive, simple, and rapid method for estimating biomass. This method could inform management plans for the conservation of ecosystems

Effects of structural environmental enrichment on welfare of juvenile seabream (Sparus aurata)

Current production systems of finfish aquaculture, and in particular intensive farming systems, can cause welfare problems leading not only to poor condition of the fish but also to a decrease in product quality. Adding structural environmental enrichment (EE) to bare rearing environments may improve the welfare of certain cultured fish. In this study we experimentally demonstrate the positive effects of adding structural EE on rearing environments of juvenile seabream (Sparus aurata). Fish maintained for 35 days with EE showed less aggression and interactions with the net pen, and lower erosion of pectoral and caudal fins, compared to fish kept in bare conditions (non-enriched, NE). In addition, EE modified the horizontal distribution of fish in the experimental cage, increasing the use of the inner areas. Non-significant effects of EE were observed on fish body condition and growth, and on brain monoamines levels and mortality. Nevertheless, this work highlights the potential use of structural EE to improve welfare of juvenile seabream, which might be feasible to apply at larger-commercial scale.Agência financiadora Aquicultura Balear S.A.U (Grupo Culmarex) Portuguese Foundation for Science and Technology UID/Multi/04326/2019 Spanish national funds from MINECO (R+D project: PHENOFISH) CTM2015- 69126-C2-1-Rinfo:eu-repo/semantics/publishedVersio

Tissue-Specific Orchestration of Gilthead Sea Bream Resilience to Hypoxia and High Stocking Density

Two different O-2 levels (normoxia: 75-85% O-2 saturation; moderate hypoxia: 42-43% O-2 saturation) and stocking densities (LD: 9.5, and HD: 19 kg/m(3)) were assessed on gilthead sea bream (Sparus aurata) in a 3-week feeding trial. Reduced O-2 availability had a negative impact on feed intake and growth rates, which was exacerbated by HD despite of the improvement in feed efficiency. Blood physiological hallmarks disclosed the enhancement in O-2-carrying capacity in fish maintained under moderate hypoxia. This feature was related to a hypo-metabolic state to cope with a chronic and widespread environmental O-2 reduction, which was accompanied by a differential regulation of circulating cortisol and growth hormone levels. Customized PCR-arrays were used for the simultaneous gene expression profiling of 34-44 selected stress and metabolic markers in liver, white skeletal muscle, heart, and blood cells. The number of differentially expressed genes ranged between 22 and 19 in liver, heart, and white skeletal muscle to 5 in total blood cells. Partial Least-Squares Discriminant Analysis (PLS-DA) explained [R2Y(cum)] and predicted [Q2Y(cum)] up to 95 and 65% of total variance, respectively. The first component (R2Y = 0.2889) gathered fish on the basis of O-2 availability, and liver and cardiac genes on the category of energy sensing and oxidative metabolism (cs, hif-1 alpha, pgc1 alpha, pgc1 beta, sirts 1-2-4-5-6-7), antioxidant defense and tissue repair (prdx5, sod2, mortalin, gpx4, gr, grp-170, and prdx3) and oxidative phosphorylation (nd2, nd5, and coxi) highly contributed to this separation. The second component (R2Y = 0.2927) differentiated normoxic fish at different stocking densities, and the white muscle clearly promoted this separation by a high over-representation of genes related to GH/IGF system (ghr-i, igfbp6b, igfbp5b, insr, igfbp3, and igf-i). The third component (R2Y = 0.2542) discriminated the effect of stocking density in fish exposed to moderate hypoxia by means of hepatic fatty acid desaturases (fads2, scd1a, and scd1b) and muscle markers of fatty acid oxidation (cpt1a). All these findings disclose the different contribution of analyzed tissues (liver >= heart > muscle > blood) and specific genes to the hypoxic- and crowding stress-mediated responses. This study will contribute to better explain and understand the different stress resilience of farmed fish across individuals and species

The Acclimation of European Sea Bass (Dicentrarchus labrax) to Temperature: Behavioural and Neurochemical Responses

Studies on fish behavioural and neurophysiological responses to water temperature change may contribute to an improved understanding of the ecological consequences of global warming. We investigated behavioural and neurochemical responses to water temperature in European sea bass (Dicentrarchus labrax) acclimated to three temperatures (18, 22 and 28°C). After 21 d of acclimation, three groups of 25 fish each were exposed to four behavioural challenges (foraging, olfactory, aversive and mirror tests). The expression of choline acetyltransferase (ChAT) was then analysed by Western blotting in CNS homogenates (from a subset of the same fish) as a marker for cholinergic system activity. In both foraging and olfactory tests, fish acclimated to 28°C exhibited significantly higher arousal responses than fish acclimated to lower temperatures. All specimens showed fright behaviour in the aversive test, but the latency of the escape response was significantly less in the fish at 28°C. Finally, the highest mirror responsiveness was exhibited by the fish acclimated to 22°C. As in the case of cholinergic neurotransmission, significantly higher ChAT levels were detected in the telencephalon, diencephalon, cerebellum and spinal cord of fish acclimated to 22 or 28°C in comparison with those maintained at 18°C. Lower ChAT levels were detected in the mesencephalon (optic tectum) at 22 and 28°C than at 18°C. These data indicate that neuronal functions are affected by water temperature. Increases or decreases in ChAT expression can be related to the functional modulation of brain and spinal cord centres involved in behavioural responses to temperature change. Overall, the results of this study suggest that the environmental temperature level influences behaviour and CNS neurochemistry in the European sea bass.Studies on fish behavioural and neurophysiological responses to water temperature change may contribute to an improved understanding of the ecological consequences of global warming. We investigated behavioural and neurochemical responses to water temperature in European sea bass (Dicentrarchus labrax) acclimated to three temperatures (18, 22 and 28 degrees C). After 21d of acclimation, three groups of 25 fish each were exposed to four behavioural challenges (foraging, olfactory, aversive and mirror tests). The expression of choline acetyltransferase (ChAT) was then analysed by Western blotting in CNS homogenates (from a subset of the same fish) as a marker for cholinergic system activity. In both foraging and olfactory tests, fish acclimated to 28 degrees C exhibited significantly higher arousal responses than fish acclimated to lower temperatures. All specimens showed fright behaviour in the aversive test, but the latency of the escape response was significantly less in the fish at 28 degrees C. Finally, the highest mirror responsiveness was exhibited by the fish acclimated to 22 degrees C. As in the case of cholinergic neurotransmission, significantly higher ChAT levels were detected in the telencephalon, diencephalon, cerebellum and spinal cord of fish acclimated to 22 or 28 degrees C in comparison with those maintained at 18 degrees C. Lower ChAT levels were detected in the mesencephalon (optic tectum) at 22 and 28 degrees C than at 18 degrees C. These data indicate that neuronal functions are affected by water temperature. Increases or decreases in ChAT expression can be related to the functional modulation of brain and spinal cord centres involved in behavioural responses to temperature change. Overall, the results of this study suggest that the environmental temperature level influences behaviour and CNS neurochemistry in the European sea bass