Coping with unpredictability: Dopaminergic and neurotrophic responses to omission of expected reward in Atlantic salmon (Salmo salar L.).

Comparative studies are imperative for understanding the evolution of adaptive neurobiological processes such as neural plasticity, cognition, and emotion. Previously we have reported that prolonged omission of expected rewards (OER, or 'frustrative nonreward') causes increased aggression in Atlantic salmon (Salmo salar). Here we report changes in brain monoaminergic activity and relative abundance of brain derived neurotrophic factor (BDNF) and dopamine receptor mRNA transcripts in the same paradigm. Groups of fish were initially conditioned to associate a flashing light with feeding. Subsequently, the expected food reward was delayed for 30 minutes during two out of three meals per day in the OER treatment, while the previously established routine was maintained in control groups. After 8 days there was no effect of OER on baseline brain stem serotonin (5-HT) or dopamine (DA) activity. Subsequent exposure to acute confinement stress led to increased plasma cortisol and elevated turnover of brain stem DA and 5-HT in all animals. The DA response was potentiated and DA receptor 1 (D1) mRNA abundance was reduced in the OER-exposed fish, indicating a sensitization of the DA system. In addition OER suppressed abundance of BDNF in the telencephalon of non-stressed fish. Regardless of OER treatment, a strong positive correlation between BDNF and D1 mRNA abundance was seen in non-stressed fish. This correlation was disrupted by acute stress, and replaced by a negative correlation between BDNF abundance and plasma cortisol concentration. These observations indicate a conserved link between DA, neurotrophin regulation, and corticosteroid-signaling pathways. The results also emphasize how fish models can be important tools in the study of neural plasticity and responsiveness to environmental unpredictability

Brain serotonergic activation in growth-stunted farmed salmon: adaption versus pathology

Contains fulltext : 158865.pdf (publisher's version ) (Open Access

Salmon welfare index model 2.0: an extended model for overall welfare assessment of caged Atlantic salmon, based on a review of selected welfare indicators and intended for fish health professionals

Here, we present an extended version of a semantic model for overall welfare assessment of Atlantic salmon reared in sea cages. The model, called SWIM 2.0, is designed to enable fish health professionals to make a formal and standardized assessment of fish welfare using a set of reviewed welfare indicators. SWIM 2.0 supplements SWIM 1.0, which was designed for application by fish farmers. We searched the literature for documented welfare indicators that could be used by fish health professionals. The selected indicators are eyes, cardiac condition, abdominal organs, gills, opercula, skeletal muscles, vaccine-related pathology, aberrant fish, necropsy of the dead fish and active euthanasia. Selection criteria for the SWIM 2.0 indicators were that they should be practical and measureable on salmon farms by fish health professionals and that each indicator could be divided into levels from good to poor welfare backed up by relevant scientific literature. To estimate each indicator's relative impact on welfare, all the indicators were weighted based on their respective literature reviews and according to weighting factors defined as part of the semantic modelling framework. This was ultimately amalgamated into an overall SWIM 2.0 model that can be used to calculate welfare indexes for salmon in sea cages, taking into account the available fish health expertise. Using this model, an example calculation based on recordings and samplings done from an Atlantic salmon sea cage containing 106 000 fish yielded an overall welfare index of 0.81 of a maximum of 1.0

Metabolic and transcriptional responses of gilthead sea bream (Sparus aurata L.) to environmental stress: New insights in fish mitochondrial phenotyping

The aim of the current study was to phenotype fish metabolism and the transcriptionally-mediated response of hepatic mitochondria of gilthead sea bream to intermittent and repetitive environmental stressors: (i) changes in water temperature (T-ST), (ii) changes in water level and chasing (C-ST) and (iii) multiple sensory perception stressors (M-ST). Gene expression profiling was done using a quantitative PCR array of 60 mitochondria-related genes, selected as markers of transcriptional regulation, oxidative metabolism, respiration uncoupling, antioxidant defense, protein import/folding/assembly, and mitochondrial dynamics and apoptosis. The mitochondrial phenotype mirrored changes in fish performance, haematology and lactate production. T-ST especially up-regulated transcriptional factors (PGC1a, NRF1, NRF2), rate limiting enzymes of fatty acid ß-oxidation (CPT1A) and tricarboxylic acid cycle (CS), membrane translocases (Tim/TOM complex) and molecular chaperones (mtHsp10, mtHsp60, mtHsp70) to improve the oxidative capacity in a milieu of a reduced feed intake and impaired haematology. The lack of mitochondrial response, increased production of lactate and negligible effects on growth performance in C-ST fish were mostly considered as a switch from aerobic to anaerobic metabolism. A strong down-regulation of PGC1a, NRF1, NRF2, CPT1A, CS and markers of mitochondrial dynamics and apoptosis (BAX, BCLX, MFN2, MIRO2) occurred in M-ST fish in association with the greatest circulating cortisol concentration and a reduced lactate production and feed efficiency, which represents a metabolic condition with the highest allostatic load score. These findings evidence a high mitochondrial plasticity against stress stimuli, providing new insights to define the threshold level of stress condition in fish

Efficiency of salmon production in submerged cages with air domes matches standard surface cages when environments are similar

Efficiency of salmon production in submerged cages with air domes matches standard surface cages when environments are simila

Salmon Welfare Index Model (SWIM 1.0): a semantic model for overall welfare assessment of caged Atlantic salmon: review of the selected welfare indicators and model presentation

A semantic model for overall welfare assessment of Atlantic salmon reared in sea cages is presented. The model, called SWIM 1.0, is designed to enable fish farmers to make a formal and standardized assessment of fish welfare using a set of selected welfare indicators. In order to cover all welfare relevant aspects from the animals’ point of view and to create a science-based tool we first identified the known welfare needs of Atlantic salmon in sea cages and searched the literature for feasible welfare indicators. The framework of semantic modelling was used to perform a structured literature review and an evaluation of each indicator. The selected indicators were water temperature, salinity, oxygen saturation, water current, stocking density, lighting, disturbance, daily mortality rate, appetite, sea lice infestation ratio, condition factor, emaciation state, vertebral deformation, maturation stage, smoltification state, fin condition and skin condition. Selection criteria for the indicators were that they should be practical and measureable on the farm, that each indicator could be divided into levels from good to poor welfare backed up by relevant scientific literature. To estimate each indicator’s relative impact on welfare, all the indicators were weighted based on their respective literature reviews and according to weighting factors defined as part of the semantic modelling framework. This was ultimately amalgamated into an overall model that calculates welfare indexes for salmon in sea cages. More importantly, the model identifies how each indicator contributes (negatively and positively) to the overall index and hence which welfare needs are compromised or fulfilled