Proactive coping style in early emerging rainbow trout carries a metabolic cost with no apparent return.

The timing with which salmonid larvae emerge from their gravel nests is thought to be correlated with a particular suite of behavioural and physiological traits that correspond to the stress coping style of the individual. Among these traits, aggressiveness, dominance and resilience to stress, are potentially interesting to exploit in aquaculture production. In the present study a series of experiments were performed, with the purpose of characterising behavioural, metabolic and production related traits in rainbow trout juveniles from different emergence fractions. Newly hatched rainbow trout were sorted according to their emergence time from an artificial redd. The early, middle, and late fractions were retained and assessed for their physiological response to stress, growth performance, metabolism, fasting tolerance, and potential for compensatory growth. The early emerging fraction showed proactive behavioural traits; they were faster to reappear following startling, showed a reduced cortisol response following stress, and a reduced metabolic cost of recovery. Emergence time was not correlated with any differences in standard or maximum metabolic rates, but was however, correlated with higher routine metabolic rates, as demonstrated by significantly bigger weight losses during fasting in the early emerging group. Growth rates and feed conversion efficiencies were not significantly different when fish were co-habitated under a restrictive feeding regime, suggesting that early emerging fish are not able to monopolise food resources. The intermediate emerging group, which makes up the bulk of a population and is often ignored, appears to possess the best growth performance traits, possibly because they do not expend excessive energy on dominance behaviour such as the early emerging group, while they are also not overly timid or stress prone such as the late emerging group.

Formation of PFAAs in fish through biotransformation: A PBPK approach.

A physiologically-based pharmacokinetic (PBPK) model for perfluorinated alkyl acids (PFAAs) in rainbow trout has been updated to include formation of perfluorooctanoic acid (PFOA) from the biotransformation of 8:2 fluorotelomer carboxylic acid (8:2 FTCA). The updated model is dynamic and simulates both uptake and depuration phases. Two empirical studies are used to parameterize and test the model. In the first case, parameters related to fecal elimination and protein binding were optimized. In the second case, parameters were sourced either from literature or from optimized values based on the first study to test model performance. Optimization of parameters resulted in a decrease in the difference between experimental data and simulation results by 57 and 23 percent for the first and the second case, respectively, compared to the original case. Sensitivity analysis was performed to identify important parameters, and uncertainty in model prediction propagated by these parameters was assessed using Monte Carlo analysis. For each case, 80 and 89 percent, respectively, of median predicted values were within the limits of experimental error when comparing simulated and experimental data. This is the first toxicokinetic model that incorporates biotransformation of PFAA precursors and simultaneously predicts the distribution of the precursor and metabolite in different tissues. The model is mechanistic, and could be applied to simulate a variety of scenarios by using the organism-specific physiological properties compiled here with other chemical-specific parameters (e.g. protein interactions).

Physiological and biochemical effects of nickel on rainbow trout (Oncorhynchus mykiss) tissues: Assessment of nuclear factor kappa B activation, oxidative stress and histopathological changes.

We investigated changes in nuclear factor kappa B (NFkB) activity, antioxidant responses and histopathological effects in the liver, gill and kidney tissues of rainbow trout exposed to nickel chloride (Ni). Two different concentrations (1 mg/L and 2 mg/L) were administrated to fish for 21 days. Tissues were taken from all fish for NFkB activity, histopathological examination and determination of superoxide dismutase (SOD), catalase (CAT) enzyme activity and of lipid peroxidation (LPO), and glutathione (GSH) levels. The findings of this study indicated that Ni exposure led to a significant increase in LPO indicating peroxidative damage and antioxidant enzymes SOD and CAT activity in tissues (p < 0.05), but 2 mg/Ni concentration caused a significant decrease in CAT activity in kidney tissues (p < 0.05). One of mechanism in the antioxidant defense system seems to be GSH, which increased in gill and kidney tissues of fish exposed to Ni (p < 0.05). NFkB immunopositivity was detected in all tissues. Ni exposure caused lamellar thickening, cellular infiltration in gill tissues, hydropic degeneration of hepatocytes in liver tissues, hyalinous accumulation within the glomeruli and tubular degeneration in kidney tissues. Our results suggested that Ni toxicity may disturb the biochemical and physiological functions of fish by causing changes in NFkB activity and oxidative and histopathological damage in the tissues of rainbow trout. This study can provide useful information for understanding of Ni-induced toxicity.

Environmental indicators in effluent assessment of rainbow trout (Oncorhynchus mykiss) reared in raceway system through phosphorus and nitrogen / Indicadores ambientais na avaliação de efluentes de truta arco-íris (Oncorhynchus mykiss) criados em sistema de raceway através do fósforo e nitrogênio

Abstract The phosphorus and nitrogen discharge via effluent of intensive trout farming system was quantified through the use of environmental indicators. The nutrient loads, the mass balance, the estimated amount of nutrients in feed and the amount of nutrients converted in fish biomass were calculated based on the concentrations of phosphorus (P) and nitrogen (N) in the feed and in the water. Of the offered feed, 24.75 kg were available as P and 99.00 kg as N, of these, 9.32 kg P (38%) and 29.12 kg N (25%) were converted into fish biomass and 15.43 kg P (62%) and 69.88 kg N (75%) were exported via effluent. The loads and the mass balance show the excessive discharge of nutrients via effluent, corroborated by the feed conversion ratio (2.12:1) due to the low efficiency of feed utilization, therefore, it is proposed the use of this zootechnical parameter as environmental indicator. In addition, feed management practices are not adequate, highlighting the low frequency of feeding during the day, excessive amount and low quality of feed offered. These results demonstrate the need for adequate feed management and the need for careful monitoring of effluent.

Resumo A descarga de fósforo e nitrogênio via efluente do sistema intensivo de truticultura foi quantificada através da utilização de indicadores ambientais. As cargas de nutrientes, o balanço de massa, a quantidade estimada de nutrientes na ração e a quantidade de nutrientes convertidos em biomassa de peixes foram calculados com base nas concentrações de fósforo (P) e nitrogênio (N) na ração e na água. Da ração oferecida, 24,75 kg estavam disponíveis como P e 99,00 kg como N, destes, 9,32 kg de P (38%) e 29,12 kg de N (25%) foram convertidos em biomassa de peixe e 15,43 kg P (62%) e 69,88 kg N (75%) foram exportados via efluente. As cargas e o balanço de massa mostram a descarga excessiva de nutrientes via efluente, corroborado pela taxa de conversão alimentar (2,12:1), devido à baixa eficiência na utilização da ração, portanto, propõe-se a utilização deste parâmetro zootécnico como indicador ambiental. Além disso, as práticas de manejo alimentar não são adequadas, destacando a baixa frequência de alimentação durante o dia, quantidade excessiva e baixa qualidade da alimentação ofertada. Esses resultados demonstram a necessidade de manejo alimentar adequado e de monitoramento do efluente.

Environmental indicators in effluent assessment of rainbow trout (Oncorhynchus mykiss) reared in raceway system through phosphorus and nitrogen.

The phosphorus and nitrogen discharge via effluent of intensive trout farming system was quantified through the use of environmental indicators. The nutrient loads, the mass balance, the estimated amount of nutrients in feed and the amount of nutrients converted in fish biomass were calculated based on the concentrations of phosphorus (P) and nitrogen (N) in the feed and in the water. Of the offered feed, 24.75 kg were available as P and 99.00 kg as N, of these, 9.32 kg P (38%) and 29.12 kg N (25%) were converted into fish biomass and 15.43 kg P (62%) and 69.88 kg N (75%) were exported via effluent. The loads and the mass balance show the excessive discharge of nutrients via effluent, corroborated by the feed conversion ratio (2.12:1) due to the low efficiency of feed utilization, therefore, it is proposed the use of this zootechnical parameter as environmental indicator. In addition, feed management practices are not adequate, highlighting the low frequency of feeding during the day, excessive amount and low quality of feed offered. These results demonstrate the need for adequate feed management and the need for careful monitoring of effluent.

Acute Toxicity Assessment of Reactive Red 120 to Certain Aquatic Organisms.

Laboratory experiments were conducted to evaluate the acute toxicity of a widely used textile dye namely Reactive Red 120 (RR 120) on certain aquatic species such as Pseudokirchneriella subcapitata (green alga), Lemna gibba (duck weed), Daphnia magna (water flea) and Oncorhynchus mykiss (Rainbow trout). All experiments were performed as per the OECD Guidelines for Testing of Chemicals. The toxicity end points of EC50, LC50, NOEC and LOEC for RR 120 were determined with 95% confidence limits using TOX STAT version 3.5. The EC50 of RR 120 for green alga, duck weed and water flea are >100.00, 64.34, 10.40 mg L(-1), respectively and LC50 for Rainbow trout is 78.84 mg L(-1). Based on the results, the test item RR 120 could be classified as non-toxic to green alga, harmful to duck weed and Rainbow trout, toxic to water flea.

Evaluating the efficiency of advanced wastewater treatment: target analysis of organic contaminants and (geno-)toxicity assessment tell a different story.

At a pilot scale wastewater treatment plant ozonation and powdered activated carbon filtration were assessed for their efficacy to remove trace organic contaminants from secondary treated effluents. A chemical analysis of 16 organic compounds was accompanied by a comprehensive suite of in vitro and in vivo bioassays with the focus on genotoxicity to account for the potential formation of reactive oxidation products. In vitro experiments were performed with solid phase extracted water samples, in vivo experiments with native wastewater in a flow through test system on site at the treatment plant. The chemical evaluation revealed an efficient oxidation of about half of the selected compounds by more than 90% at an ozone dose of 0.7 g/g DOC. A lower oxidizing efficiency was observed for the iodinated X-ray contrast media (49-55%). Activated carbon treatment (20 mg/L) was less effective for the removal of most pharmaceuticals monitored. The umuC assay on genotoxicity delivered results with about 90% decrease of the effects by ozonation and slightly lower efficiency for PAC treatment. However, the Ames test on mutagenicity with the strain YG7108 revealed a consistent and ozone-dose dependent increase of mutagenicity after wastewater ozonation compared to secondary treatment. Sand filtration as post treatment step reduced the ozone induced mutagenicity only partly. Also the fish early life stage toxicity test revealed an increase in mortality after ozonation and a reduced effect after sand filtration. Only activated carbon treatment reduced the fish mortality compared to conventional treatment on control level. Likewise the in vivo genotoxicity detected with the comet assay using fish erythrocytes confirmed an increased (geno-)toxicity after ozonation, an effect decrease after sand-filtration and no toxic effects after activated carbon treatment. This study demonstrates the need for a cautious selection of methods for the evaluation of advanced (oxidative) treatment technologies and of the effectiveness of post-treatments for elimination of adverse effects caused by oxidative treatments case by case.

The capacity to detect change stream fish communities characteristics at the site-level in the Lake Ontario basin.

We investigate natural inter-annual variability of fish community measures within streams of the Lake Ontario basin. Given this variability, we examined coefficients of variation (CV) among the community measures and three scenarios pertaining to the capacity of biologists to detect changes in the fish community at the stream site level. Results indicate that Ontario's stream fish communities are highly variable in time. Young-of-the-year rainbow trout growth was the least variable whereas biomass density scored the highest CV of 0.50 among streams (range 0.22-0.99). Given the CVs and relatively equal sample sizes, our measures of the fish community can be ranked from least to most powerful: biomass, density, richness, diversity, and growth of young-of-the-year rainbow trout. Only large changes in measures can typically be detected. For instance, it would take 4-6 years of monitoring before and after a pulse perturbation to detect a 50 % change in species richness or diversity. We suggest that monitoring abundance is unlikely to result in the detection of small impacts within a short period of time and that large effects can be masked by low statistical power. This evidence voices the need for more research into better sampling methods, experimental designs, and choice of indicators to support monitoring programs for flowing waters.

A spatially and temporally explicit risk assessment for salmon from a prey base exposed to agricultural insecticides.

This risk assessment applied a framework for determining probable co-occurrence of juvenile spring Chinook salmon (Oncorhynchus tshawytscha) with agricultural pesticides in the Willamette Basin, Oregon (Teply et al. this issue) to characterize risk to the threatened population. The assessment accounted for spatial and temporal distribution of 6 acetylcholinesterase-inhibiting insecticides in salmonid habitat within the basin and their relative contributions to mixture toxicity estimated from chemical monitoring data. The 6 insecticides were chlorpyrifos, diazinon, malathion, carbaryl, carbofuran, and methomyl. Seasonal distributions of the juvenile salmon prey base across the basin were determined and compared to co-occurrence with the insecticide mixture to determine the probability of prey reduction and reduced production of juvenile fish. Probability of effect on freshwater aquatic invertebrates was based on acute toxicity species sensitivity distributions (normalized to the most potent compound, chlorpyrifos) using a novel approach to apply the toxicological concept of concentration addition to species sensitivity distributions with differing slopes. The chlorpyrifos distribution was then used to determine relative sensitivity among various species tested within the important taxa making up the prey base. A prey base index was devised, incorporating diet composition and prey availability, to evaluate the indirect effects of the insecticide mixture on juvenile salmon production occurring as a result of a reduction in the prey base. Our analysis targeted fish use of backwater and off-channel habitat units, because they generally coincide with agricultural lands in lowlands and represent shallow habitat with limited water exchange. The percentage of agricultural land use within 300 m of critical habitat stream reaches was used to scale chemical measurement data from a site with high agricultural land use across the full extent of the basin to provide estimates of chemical exposure in each reach. Seasonal impacts were evaluated from mean monthly concentrations. Stressor impact on 5 key taxa was evaluated at each time step and for each reach, and the outcome was compared to a conservation threshold assigned to the prey base index. Only 13% of juveniles reared in backwater, off-channel habitat within 300 m of agricultural land. Percent reduction of carrying capacity as a consequence of reduced prey was estimated to be 5% over the entire brood year. This can be considered lost capacity that is probably compensated elsewhere via increased occupancy (emigration to other habitat units within the reach), which is not accounted for in the model.

An ecological risk assessment of the acute and chronic effects of the herbicide clopyralid to rainbow trout (Oncorhynchus mykiss).

Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) is a pyridine herbicide frequently used to control invasive, noxious weeds in the northwestern United States. Clopyralid exhibits low acute toxicity to fish, including the rainbow trout (Oncorhynchus mykiss) and the threatened bull trout (Salvelinus confluentus). However, there are no published chronic toxicity data for clopyralid and fish that can be used in ecological risk assessments. We conducted 30-day chronic toxicity studies with juvenile rainbow trout exposed to the acid form of clopyralid. The 30-day maximum acceptable toxicant concentration (MATC) for growth, calculated as the geometric mean of the no observable effect concentration (68 mg/L) and the lowest observable effect concentration (136 mg/L), was 96 mg/L. No mortality was measured at the highest chronic concentration tested (273 mg/L). The acute:chronic ratio, calculated by dividing the previously published 96-h acutely lethal concentration (96-h ALC(50); 700 mg/L) by the MATC was 7.3. Toxicity values were compared to a four-tiered exposure assessment profile assuming an application rate of 1.12 kg/ha. The Tier 1 exposure estimation, based on direct overspray of a 2-m deep pond, was 0.055 mg/L. The Tier 2 maximum exposure estimate, based on the Generic Exposure Estimate Concentration model (GEENEC), was 0.057 mg/L. The Tier 3 maximum exposure estimate, based on previously published results of the Groundwater Loading Effects of Agricultural Management Systems model (GLEAMS), was 0.073 mg/L. The Tier 4 exposure estimate, based on published edge-of-field monitoring data, was estimated at 0.008 mg/L. Comparison of toxicity data to estimated environmental concentrations of clopyralid indicates that the safety factor for rainbow trout exposed to clopyralid at labeled use rates exceeds 1000. Therefore, the herbicide presents little to no risk to rainbow trout or other salmonids such as the threatened bull trout.

Depletion of selected polychlorinated biphenyl, dibenzodioxin, and dibenzofuran congeners in farmed rainbow trout (Oncorhynchus mykiss): a hint for safer fish farming.

Farmed fish can be exposed to persistent organic contaminants--such as polychlorinated biphenyls (PCBs), dibenzodioxins (PCDDs), and dibenzofurans (PCDFs)--via feed, this eventually resulting in accumulation levels of health concern. To study the correlation between feed contamination, chemical accumulation in fish muscle (fillet), and chemical depletion, an all-vegetal base (or blank) feed was prepared and fortified with a commercial PCB mixture (Aroclor 1254) and six PCDD and PCDF congeners (namely, 2,3,7,8-T(4)CDD, 2,3,7,8-T(4)CDF, 1,2,3,7,8-P(5)CDD, 1,2,3,7,8-P(5)CDF, O(8)CDD, and O(8)CDF) to reproduce realistic low, medium, and high contamination levels. After a 1-month exposure, trout (Oncorhynchus mykiss) were fed with the blank feed and sacrificed every 0.5 months over a 3-month period from exposure end; fillet specimens were sampled at each time. In all groups, the average fish weight increased linearly through the observation period. The chemical diminishing patterns observed were due to the combined effect of clearance and growth dilution: for 10 PCB and four PCDD and PCDF congeners, patterns were described with an empirical one-compartment (fish muscle) model. The canonical pseudo-first-order kinetic equation used was also modified into the form C=[C(0)exp(-k(C)t)] (m(W)t+1)(-1) to distinguish between the contributions to depletion from clearance, exp(-k(C)t), and growth dilution, (m(W)t+1)(-1). Most mean clearance half-life (HL(C)) estimates appear to be greater than 4 months, in a number of cases reaching magnitudes well over 10 months or even negative, thus clearly indicating a non-negligible contribution from a second compartment. Based on means and their 95% confidence intervals, the depletion HL(D) estimates of the 14 selected congeners seem to be comprised between 1.2-3.4 and 1.0-5.0 months, respectively: these values, accounting for both clearance and growth dilution, provide an indication of the relevance of a blank feed as a management option to reduce the overall PCB, PCDD, and PCDF content in farmed trout. Due to a lack of bioaccumulation, O(8)CDD and O(8)CDF yielded no results for evaluation, whereas for many PCB congeners results were insufficient for empirical modelling.

Effluent profile of commercially used low-phosphorus fish feeds.

Excess phosphorus (P) in aquaculture feeds contributes to the eutrophication of natural waters. While commercially available low-P (LP) fish feeds have been developed, there is uncertainty about their potential to reduce effluent P while maintaining fish growth relative to regular P (RP) feeds. We therefore simulated commercial aquaculture conditions and fed for 55 days rainbow trout (approximately 190 kg/raceway, n = 3 raceways/diet) RP (1.4% total P) and LP (1.0%) feeds then determined effluent P levels, fish growth, and feed costs. Excretions of fecal-P and soluble-P, but not particulate-P, in effluents were greater in RP than in LP ponds. Fish growth, bone-P and plasma-P were similar between diets, demonstrating that LP feeds can lower effluent P levels without compromising growth. Costs were 0.97 dollars/kg fish production for LP feeds, and 0.74 dollars/kg for RP. Because feed is the largest variable cost in commercial aquaculture, the use of LP feeds can significantly increase production costs.