Christopher Good

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.

Growth Performance, Fillet Quality, and Reproductive Maturity of Rainbow Trout (Oncorhynchus mykiss) Cultured to 5 Kilograms within Freshwater Recirculating Systems

Rainbow trout are commonly cultured within aquaculture systems to one pound or less and marketed as pan- sized fillets. Production of larger rainbow trout provides a distinguishable product. Research that describes the growth performance and fillet quality of large rainbow trout is limited, particularly for trout cultured in recirculating aquaculture systems. A study was conducted evaluating the growth performance and fillet quality attributes of all- female rainbow trout reared using freshwater recirculating systems operated at a mean water temperature of 13°C, under constant lighting, and with around-the-clock feeding. Rainbow trout grew to 4.8 kg in 22 months post-hatch. Growth rates declined with the onset of reproductive maturity. Rainbow trout weighed 5.2 kg at 26 months. The mean ratio of feed provided to biomass gain was 1.36:1 from first feeding to 22 months but increased substantially from 23-25 months. As rainbow trout approached reproductive maturity, 10 fish were collected at specified intervals for assessment of fillet quality attributes. Fillet yield peaked at 20-22 months when trout were 3.8-4.8 kg. Cook yield, cooked fillet firmness, and crude fat decreased; while fillet moisture and raw fillet firmness increased from 24-26 months. Changes in fillet quality coincided with reduced growth rates, decreased feed efficiency, and increasing gonadosomatic index. Two principal components were identified that explained more than 73% of the variation in growth and fillet attribute responses: principal component 1, the growth variable (length, weight, fillet thickness, belly flap thickness, and cook yield) and principal component 2, the quality variable (fillet moisture, fillet fat, and cooked fillet firmness). This research provides rainbow trout growth performance and fillet quality results that can be referenced for the development of recirculating system production plans and for selection of harvest endpoints that balance the requirements of fish farmers and the food industry sector .

Flavobacterium branchiophilum and F. succinicans associated with bacterial gill disease in rainbow trout Oncorhynchus mykiss (Walbaum) in water recirculation aquaculture systems

Bacterial gill disease (BGD) is a common and occasionally devastating disease that affects numerous cultured fish species throughout the world (Starliper & Schill 2012). Outbreaks of BGD tend to occur when environmental conditions deteriorate, and opportunistic pathogens can more readily cause overt disease (Bullock 1972; Schachte 1983). The putative causative agent, Flavobacterium branchiophilum, has been shown to induce BGD under laboratory conditions (e.g. Lumsden et al. 1995; Ostland et al. 1995); however, diagnosis of BGD in the field is generally carried out through light microscopy and/or observation of clinical signs. Therefore, the identity of the bacterial specie(s) present on the gills of BGD-affected fish in culture settings is most often based on visual assessment alone. The observed bacteria using microscopy are presumed to be F. branchiophilum based on organism morphology (numerous long, thin rods; Fig. ​Fig.1.),1.), with this presumption supported by previous BGD research (e.g. Byrne et al. 1995; Ostland et al. 1997; Derksen, Ostland & Ferguson 1998) and various F. branchiophilum-specific diagnostic approaches that have been developed. The latter include ELISA (MacPhee et al. 1995), IFAT (Heo, Kasai & Wakabayashi 1990), and PCR (Toyama, Kita & Wakabayashi 1996). A comprehensive examination of bacterial species present on the gills of naturally infected fish, however, has not been carried out and is desirable to enhance our understanding of BGD and to inform further research (e.g. potential vaccine development). We therefore sought to induce BGD through environmental manipulation (as opposed to pathogen challenge) and to identify the bacterial species involved in typical BGD outbreaks. Our findings are presented in this short communication.

The Impact of Water Exchange Rate and Treatment Processes on Water- Borne Hormones in Recirculation Aquaculture Systems Containing Sexually Maturing Atlantic Salmon Salmo salar

A controlled seven-month study was conducted in six replicated water recirculation aquaculture systems (WRAS) to assess post-smolt Atlantic salmon (Salmo salar) performance in relation to WRAS water exchange rate. Unexpectedly high numbers of precocious sexually mature fish were observed in all WRAS toward the end of the study period; therefore, a separate investigation was conducted to quantify the levels of water-borne hormones (cortisol (C), testosterone (T), 11-ketotestosterone (11-KT), progesterone (P), and estradiol (E2)) to determine the impact of WRAS exchange rate, as well as transit through the unit processes, on soluble hormone concentrations.Triplicate water samples were collected at three separate sites in each of the six WRAS: pre-unit processes, post-unit processes, and at the makeup water influent. Water samples were concentrated and separate quantifications were carried out for each target hormone using enzyme immunoassay kits. Results indicated that among the hormones examined, only T was associated with higher concentrations in low exchange WRAS compared to high exchange WRAS. Water passage through the unit processes was associated with a significant reduction in concentration of 11-KT, in both high and low exchange WRAS. Water-borne concentrations of T, 11-KT, and E2 were significantly higher than influent makeup water; the majority of C and P concentrations were not significantly different between WRAS and makeup water samples. No significant differences were noted in the prevalence of apparently sexually mature fish or gonadosomatic indices in either sex between treatments, except a significantly higher prevalence of apparently mature female fish in low exchange WRAS. Overall, these findings suggest that, under the conditions of this study, C, P, E2, and 11-KT do not accumulate in lower exchange WRAS, and that, aside from 11-KT, the WRAS unit processes do not impact hormone concentration. Furthermore, the observed precocious sexual maturation was mostly unrelated to WRAS exchange rate.

Low-Dose Hydrogen Peroxide Application in Closed Recirculating Aquaculture Systems

Abstract The aim of the present work was to simulate water treatment practices with hydrogen peroxide (HP) in recirculating aquaculture systems (RAS). Six identical 1,700-L pilot-scale RAS were divided into two experimental groups based on daily feed allocation and operated under constant conditions for a period of 3 months. The organic and nitrogenous loadings of the systems differed fourfold between the two groups and were achieved by predefined constant daily feed loads and constant additions of water. The fixed cumulative feed burden was 1.6 × 103 mg feed/L in the low-intensity RAS and 6.3 × 103 mg/L in the high-intensity RAS. The decay of HP in rearing tanks and disconnected biofilter units was investigated by means of HP spiking experiments. The decay in high-intensity RAS rearing units and biofilters was orders of magnitude faster than that in low-intensity units. The application of HP impaired biofilter nitrite oxidation in low-intensity RAS but not in high-intensity RAS. The impact of HP exposure...

Observations on Side-Swimming Rainbow Trout in Water Recirculation Aquaculture Systems

Abstract During a controlled 6-month study using six replicated water recirculation aquaculture systems (WRASs), it was observed that Rainbow Trout Oncorhynchus mykiss in all WRASs exhibited a higher-than-normal prevalence of side swimming (i.e., controlled, forward swimming but with misaligned orientation such that the fishs sagittal axis is approximately parallel to the horizontal plane). To further our understanding of this abnormality, a substudy was conducted wherein side swimmers and normally swimming fish were selectively sampled from each WRAS and growth performance (length, weight), processing attributes (fillet yield, visceral index, ventrum [i.e., thickness of the ventral “belly flap”] index), blood gas and chemistry parameters, and swim bladder morphology and positioning were compared. Side swimmers were found to be significantly smaller in length and weight and had less fillet yield but higher ventrum indices. Whole-blood analyses demonstrated that, among other things, side swimmers had significantly lower whole-blood pH and higher Pco 2. Side swimmers typically exhibited swim bladder malformations, although the positive predictive value of this subjective assessment was only 73%. Overall, this study found several anatomical and physiological differences between side-swimming and normally swimming Rainbow Trout. Given the reduced weight and fillet yield of market-age side swimmers, producers would benefit from additional research to reduce side-swimming prevalence in their fish stocks. Received March 20, 2014; accepted May 20, 2014

Assessing the Suitability of a Partial Water Reuse System for Rearing Juvenile Chinook Salmon for Stocking in Washington State

To assess the suitability of water reuse technology for raising Pacific salmon Oncorhynchus spp. for stocking purposes, fish health and welfare were compared between two groups of juvenile Chinook salmon O. tshawytscha from the same spawn: one group was reared in a pilot partial water reuse system (circular tanks), and the other group was reared in a flow-through raceway. This observational study was carried out over a 21-week period in Washington State. Reuse and raceway fish were sampled repeatedly for pathogen screening and histopathology; fin erosion and whole-blood characteristics were also evaluated. By the studys end, no listed pathogens were isolated from either cohort, and survival was 99.3% and 99.0% in the reuse and raceway groups, respectively. Condition factor was 1.28 in raceway fish and 1.14 in reuse fish; this difference may have been attributable to occasional differences in feeding rates between the cohorts. Fin indices (i.e., length of the longest dorsal or caudal fin ray, standardized by fork length) were lower in reuse fish than in raceway fish, but fin erosion was not grossly apparent in either cohort. The most consistent histological lesion was gill epithelial hypertrophy in reuse fish; however, blood analyses did not suggest any corresponding physiological imbalances. Overall, results suggest that water reuse technology can be employed in rearing juvenile anadromous salmonids for stocking purposes.

Genetic Line by Environment Interaction on Rainbow Trout Growth and Processing Traits

AbstractGenetic line-by-environment (G×E) interactions were determined for growth and processing traits of five genetic lines of Rainbow Trout Oncorhynchus mykiss reared in four environments. Genetic lines included (1) a mixed pool of 109 families selectively bred for improved growth (Growth Line) at the U.S. Department of Agriculture (USDA) National Center for Cool and Cold Water Aquaculture (NCCCWA; Kearneysville, West Virginia), (2) a mixed pool of 52 randomly bred families (Synthetic Control) and fish from three commercial sources, identified as (3) Commercial A, (4) Commercial B, and (5) Commercial C. Two study locations (NCCCWA and The Conservation Fund’s Freshwater Institute [FI], Shepherdstown, West Virginia) contained all five genetic lines of fish while the remaining two sites (USDA National Cold Water Marine Aquaculture Center, Franklin, Maine, and Casta Line Trout Farm, Goshen, Virginia) contained only the Growth Line and Commercial A fish. Fish were PIT-tagged and allowed to comingle at all l...

Assessing the Utility of Ultraviolet Irradiation to Reduce Bacterial Biofilms in Fish Hatchery Well Water Supplies

The accumulation of bacterial biofilms and consequent clogging of screens, pipes, and heat exchanger equipment is problematic for water supply systems contaminated with iron bacteria and other slime forming bacteria. Despite the ubiquitous threat posed by iron bacteria contamination in groundwater sources, limited research has focused on physical treatments to address this issue. We sought to investigate the effectiveness of ultraviolet (UV) irradiation on inactivating iron bacteria and slime forming bacteria in a fish hatchery supply water known to have issues with bacterial biofilms. Biological activity reaction tests (BART) were used to analyze the presence or absence of iron related and slime forming bacteria in raw well water at UV dosages of 0 mJ/cm2, 15 mJ/cm2, 30 mJ/cm2, 45 mJ/cm2 and 60 mJ/cm2. Results suggest that UV treatment decreases iron bacteria survival, with the highest percent of non-reactive BARTTM test vials resulting from 45 mJ/cm2 and 60 mJ/cm2 UV exposure; however, data regarding UV inactivation of slime forming bacteria were inconclusive. These initial ‘proof of concept’ findings can be used to design pilot UV water treatment systems for fish hatcheries known to have iron bacteria problems. Pilot treatment system testing can then provide the necessary results to ensure that UV treatment is effective against site-specific iron bacteria populations before full-scale treatment systems are implemented.