Bendik Fyhn Terjesen

Free amino acid and protein content in the planktonic copepod Temora longicornis compared to Artemia franciscana

Abstract Previous studies have indicated that natural zooplankton, the natural prey organisms of marine fish larvae, is superior to enriched Artemia spp. nauplii in supporting survival, growth and normal development of pigmentation and eye migration in Atlantic halibut larvae. The present study was designed to compare the amino acid dynamics in copepods harvested from a natural lagoon with that of enriched Artemia franciscana nauplii. The natural zooplankton in the present study was dominated by Temora longicornis , but varied in its developmental stage composition, apparent nutritional quality, amount and availability. The protein content in natural zooplankton varied from 31% to 54% of dry mass (DM) compared to 31% in enriched Artemia nauplii. The amount of free amino acids (FAA) in relation to protein was 14% in enriched Artemia nauplii and varied between 16% and 27% in zooplankton in two consecutive seasons. The FAA composition of zooplankton in 1996 was unaffected by stage and season, and showed a species-specific pattern. In response to starvation, two patterns in the amino acid dynamics of copepods were found. The first, exhibited by the major nonessential amino acids (NEAA), showed a continuous reduction in individual amount, while the second pattern, exhibited by the minor nonessential amino acids and all the essential FAA, had an initial increase followed by a reduction. It is suggested that the protein amount in DHA Selco™ (INVE)-enriched Artemia nauplii is too low in order to maximise the growth potential of some marine fish larvae as cod and halibut.

Purine-induced expression of urate oxidase and enzyme activity in Atlantic salmon (Salmo salar). Cloning of urate oxidase liver cDNA from three teleost species and the African lungfish Protopterus annectens.

The peroxisomal enzyme urate oxidase plays a pivotal role in the degradation of purines in both prokaryotes and eukaryotes. However, knowledge about the purine‐induced expression of the encoding gene is lacking in vertebrates. These are the first published sequences of fish urate oxidase, which were predicted from PCR amplified liver cDNAs of Atlantic salmon (Salmo salar), Atlantic cod (Gadus morhua), Atlantic halibut (Hippoglossus hippoglossus) and African lungfish (Protopterus annectens). Sequence alignment of different vertebrate urate oxidases revealed amino acid substitutions of putative functional importance in the enzyme of chicken and lungfish. In the adult salmon, expression of urate oxidase mRNA predominated in liver, but was also identified in several nonhepatic organs including brain, but not in skeletal muscle and kidney. Juvenile salmon fed diets containing bacterial protein meal (BPM) rich in nucleic acids showed a significant increase in liver urate oxidase enzyme activity, and urea concentrations in plasma, muscle and liver were elevated. Whereas salmon fed the 18% BPM diet showed a nonsignificant increase in liver mRNA levels of urate oxidase compared with the 0% BPM‐fed fish, no further increase in mRNA levels was found in fish receiving 36% BPM. The discrepancy between urate oxidase mRNA and enzyme activity was explained by rapid mRNA degradation or alternatively, post‐translational control of the activity. Although variable plasma and liver levels of urate were detected, the substrate increased only slightly in 36% BPM‐fed fish, indicating that the uricolytic pathway of Atlantic salmon is intimately regulated to handle high dietary purine levels.

Molecular and physiological responses to long-term sublethal ammonia exposure in Atlantic salmon (Salmo salar)

The objective of this study was to determine the underlying physiological and molecular responses to long-term sublethal ammonia exposure in Atlantic salmon (Salmo salar) parr. Previous studies have predominately focused on mechanisms during acute, short-term exposure. For that purpose Atlantic salmon parr were exposed to four ammonia concentrations between 4 and 1800 μmol l(-1) total ammonia nitrogen (TAN), and subjected to two feeding regimes for 15 weeks. Elevated environmental ammonia and full feeding strength caused an initial increase in plasma ammonia levels ([T(amm)]) after 22 days of exposure, which thereafter declined and remained similar to the control animals towards the end of the study. On the other hand, a progressive decrease in plasma urea levels was evident throughout the entire exposure period and depended on the concentration of environmental ammonia, with the largest decrease in urea levels observed at the highest ammonia concentrations (1700 and 1800 μmol l(-1) TAN). We hypothesized that the successful adaptation to long-term elevated ammonia levels would involve an increased capacity for carrier-facilitated branchial excretion. This hypothesis was strengthened by the first evidence of an up-regulation of branchial transcription of the genes encoding the Rhesus (Rh) glycoproteins, Rhcg1 and Rhcg2, urea transporter (UT) and aquaporin 3a (Aqp3a), during long-term exposure. Of the Rhesus glycoprotein (Rh) mRNAs, Rhcg1 was up-regulated at all tested ammonia levels, while Rhcg2 showed a concentration-sensitive increase. Increased transcription levels of V-type H(+)-ATPase (H(+)-ATPase) were observed at the highest ammonia concentrations (1700 and 1800 μmol l(-1) TAN) and coincided with an up-regulation of Rhcg2 at these concentrations. Transcription of UT and Aqp3a was increased after 15 weeks of exposure to low ammonia levels (470 and 480 μmol l(-1) TAN). A significant increase in brain glutamine (Gln) concentration was observed for full fed Atlantic salmon after 22 days and in fish with restricted feeding after 105 days of exposure to 1800 and 1700 μmol l(-1) TAN, respectively, without any concomitant decrease in brain glutamate (Glu) concentrations. These results suggest that Gln synthesis is an ammonia detoxifying strategy employed in the brain of Atlantic salmon parr during long-term sublethal ammonia exposure. Full feed strength had an additive effect on plasma [T(amm)], while the restricted feeding regime postponed the majority of the observed physiological and molecular responses. In conclusion, Atlantic salmon parr adapts to the long-term sublethal ammonia concentrations with increased branchial transcription levels of ammonia and urea transporting proteins and ammonia detoxification in the brain.

Modelling growth performance and feeding behaviour of Atlantic salmon (Salmo salar L.) in commercial-size aquaculture net pens: Model details and validation through full-scale experiments

We have developed a mathematical model which estimates the growth performance of Atlantic salmon in aquaculture production units. The model consists of sub-models estimating the behaviour and energetics of the fish, the distribution of feed pellets, and the abiotic conditions in the water column. A field experiment where three full-scale cages stocked with 120,000 salmon each (initial mean weight 72.1 ± SD 2.8 g) were monitored over six months was used to validate the model. The model was set up to simulate fish growth for all the three cages using the feeding regimes and observed environmental data as input, and simulation results were compared with the experimental data. Experimental fish achieved end weights of 878, 849 and 739 g in the three cages respectively. However, the fish contracted Pancreas Disease (PD) midway through the experiment, a factor which is expected to impair growth and increase mortality rate. The model was found able to predict growth rates for the initial period when the fish appeared to be healthy. Since the effects of PD on fish performance are not modelled, growth rates were overestimated during the most severe disease period. This work illustrates how models can be powerful tools for predicting the performance of salmon in commercial production, and also imply their potential for predicting differences between commercial scale and smaller experimental scales. Furthermore, such models could be tools for early detection of disease outbreaks, as seen in the deviations between model and observations caused by the PD outbreak. A model could potentially also give indications on how the growth performance of the fish will suffer during such outbreaks. Statement of relevance We believe that our manuscript is relevant for the aquaculture industry as it examines the growth performance of salmon in a fish farm in detail at a scale, both in terms of number of fish and in terms of duration, that is higher than usual for such studies. In addition, the fish contracted a disease (PD) midway through the experiment, thus resulting in a detailed dataset containing information on how PD affects salmon growth, which can serve as a foundation to understanding disease effects better. Furthermore, the manuscript describes an integrated mathematical model that is able to predict fish behaviour, growth and energetics of salmon in response to commercial production conditions, including a dynamic model of the distribution of feed pellets in the production volume. To our knowledge, there exist no models aspiring to estimate such a broad spectre of the dynamics in commercial aquaculture production cages. We believe this model could serve as a future tool to predict the dynamics in commercial aquaculture net pens, and that it could represent a building block that can be utilised in a future development of knowledge-driven decision-support tools for the salmon industry.

Description of Embryogenesis of Atlantic Cod Gadus Morhua

This paper presents a description of the embryonic development of Atlantic cod Gadus morhua. In addition, an equation describing the effect of temperature on developmental rate was developed. The whole period of embryogenesis was divided into 6 subperiods and 75 specific stages based on the distinctive characteristics. Temperature effects on the developmental rate of Atlantic cod embryos were studied at 5 different regimes of constant temperature in the range 1.912.25C. During somitogenesis no less than 46 somites from a total number of 52-53 appear at equal time intervals. Embryos within single temperature batches showed very high synchronism of development: the deviation was no more than 1% from fertilization till hatching. In order to unify the developmental time under different temperature regimes, the age of embryos was measured in the relative units of S (“tau somite”), which correspond to the time of formation of a single somite pair. The empirical S values determined at different temperature regimes were used to define an equation describing the dependence of the developmental rate on temperature in Atlantic cod embryos. This dependence was expressed as: log S (t) = 2.62025-0.06803t + 0.00087t , where t is the temperature.

Hydrodynamics of octagonal culture tanks with Cornell-type dual-drain system

Abstract Large culture tanks of several hundred or thousand m 3 size are generally encouraged for economic advantages in Recirculating Aquaculture Systems (RAS). Out of numerous possibilities in designing the inlet and outlet configurations in octagonal culture tanks, the inlet pipes near the corner walls and the outlets at the tank’s center and/or on side wall are some of the widely-used configurations. The use of wall drain to achieve a controlled flow pattern in the tank, however, influences distinct flow features such as pressure, velocity, uniformity and turbulence in the tank, which are of theoretical interest as well as practical importance. A finite volume description of the flow in an octagonal culture tank at full-scale was therefore developed using Realizable turbulence model with second order accuracy in space and time. The tank was equipped with an inlet pipe near the corner wall and dual-drain outlet system of Cornell-type. The base case had a flow configuration of 45% of flow through central bottom drain, and the rest through the wall drain. Model verification was performed using grid convergence tests, and validation was conducted using Acoustic Doppler velocimetry (ADV) based velocity measurements. The effect of wall drain on the large-scale and small-scale turbulent structures was studied using the distribution of turbulent kinetic energy and vorticity respectively. The parametric study on the flow-split between the two outlets was analyzed using different flowfield indicators, such as flow velocity, uniformity, vorticity strength, maximum absolute vorticity and swirl number. Such an inclusive analysis not only explores the hydrodynamics in the commercial culture tanks with Cornell-type dual-drain but also recommends the farmers with the suitable flow-split between such outlet systems.