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The increasing demand for pikeperch (Sander lucioperca) from recirculating aquaculture systems (RAS) has raised the need for detailed knowledge on water quality parameters. Nitrate thresholds are of interest as nitrate accumulates in RAS and influences fish physiology. The trial was conducted in a recirculating aquaculture respirometer with pikeperch (average body weight (BW) 367 ± 1.1 g) successively reared at three different nitrate-nitrogen (NO3–N) concentrations (N30: 30 mg L−1, N120: 120 mg L−1 and N240: 240 mg L−1) and compared to a control group reared at the lowest possible nitrate-nitrogen concentration (N0: 5 mg L−1). Pikeperch were fed once per day with a commercial diet at three different feeding levels corresponding to 0.3% BW, 0.6% BW and 0.9% BW in triplicates for 8 days at either nitrate-nitrogen concentration before fasting for additional 3 days. Oxygen consumption and ammonia excretion were measured for 22-h in fed and fasting pikeperch to examine the influence of nitrate on energy metabolism. Metabolisable energy, retained energy and digestible energy requirements for maintenance (DEm) as well as the efficiency for energy utilisation (kg) and relative protein utilisation for energy metabolism (as ammonia quotient (AQ)) were determined. Specific dynamic action (SDA) was calculated to estimate the amount of energy spend on ingestion, digestion, absorption and assimilation of feed at different nitrate levels. SDA was significantly increased in the N240 treatment. Results of DEm showed a significant difference between N30 and N120 with DEm of N120 being about 73% higher than DEm of N30. The efficiency kg was significantly decreased between N240 and both N120 and N30 by 10% and 11% respectively. Increased values in AQ in the feed depleted fish in the N240 treatment indicates that fasting pikeperch in the high nitrate treatment had to use body protein to fuel an average of 46 ± 7% of their energy metabolism. The results of this trial show that pikeperch tolerate NO3–N concentrations of up to 240 mg L−1 but energy requirements are most favourable at concentrations of 30 mg L−1 NO3–N.

This study examines the effects of swim bladder inflation failure, a common developmental abnormality in finfish aquaculture, on the energy allocation, growth, and development of California Yellowtail (Seriola dorsalis). Health and fitness metrics including oxygen consumption, aerobic scope, critical swimming speed, feed conversion ratio, and growth rate, were monitored over a 32-week growout period in three groups of S. dorsalis: aquaculture-reared fish that failed to inflate their swim bladders (uninflated), aquaculture-reared fish with properly inflated swim bladders (inflated), and wild-caught individuals (wild). After the growout period, the uninflated fish had significantly lower body mass (636.1 ± 80.4 g vs. 758.6 ± 92.7 g inflated), shorter body length (36.5 ± 1.9 cm vs. 39.6 ± 2.0 cm inflated), and smaller girth (21.5 ± 1.2 cm vs. 23.2 ± 1.1 cm inflated) than the inflated fish. In addition, the uninflated fish had the least efficient feed conversion ratio (2.08 uninflated vs. 1.49 inflated, 1.41 wild), needing 39.8% more feed than the inflated fish, and 47.8% more feed than the wild fish to gain equivalent mass. These differences in growth and feed conversion appear to be primarily attributed to differences in energy allocation. Measures of oxygen consumption using a swim tunnel respirometer at two time points during the growout period showed that uninflated fish had significantly higher metabolic costs than both the inflated and wild groups over a large range of the swimming speeds tested. In addition, the uninflated fish were often observed swimming faster in their growout tank, likely to generate enough lift to compensate for the lack of a buoyant swim bladder. The wild-caught fish had the lowest feed conversion ratios and had significantly lower metabolic costs than both the inflated and uninflated aquaculture-reared fish at the beginning of the growout period (shortly after capture from the wild). The results of this study show that rearing S. dorsalis without a functional swim bladder is not economically feasible based on their poor growth and feed conversion ratios, and suggest that there is room for improvement in the metabolic efficiency of cultured S. dorsalis with properly inflated swim bladders.

Aspects of swimming and metabolic physiology were measured in aquaculture-reared California Yellowtail (Seriola dorsalis) in comparison to wild-caught individuals in order to examine potential differences in health and fitness associated with captive rearing, and to help identify areas for targeted improvement in Seriola aquaculture. Incremental swimming velocity trials using a swim tunnel respirometer on small yellowtail (mean body length = 18.9 cm, mass = 80.1 g) showed that aquaculture-reared fish had a significantly slower mean maximum sustainable swimming speed (Ucrit) (4.16 ± 0.62 BL s−1) in comparison to that of wild-caught fish (4.80 ± 0.52 BL s−1). In addition, oxygen consumption (ṀO2) measurements at varying swimming speeds allowed for estimation of standard metabolic rate, which was significantly higher in aquaculture-reared yellowtail (7.31 ± 2.32 vs. 3.94 ± 1.60 mg O2 kg−1 min−1 at 18 °C). Aquaculture fish also had a lower aerobic scope (9.20 ± 3.44 mg O2 kg−1 min−1) in comparison to wild-caught yellowtail (15.80 ± 5.78 mg O2 kg−1 min−1), which likely contributed to their reduced capacity for fast sustainable swimming. Reduced physical fitness is commonplace in aquaculture-reared fishes, and the examination of wild-caught yellowtail in this study provides baseline metrics that can be used to gauge the health and fitness of future S. dorsalis production. In particular, the lower standard metabolic rate and higher aerobic scope of wild-caught fish represent desirable metabolic characteristics that if achievable in aquaculture through better-rearing practices could allow for increased feed conversion efficiencies and potentially faster growth. At a minimum, a 35–40% reduction in metabolic costs at low swimming speeds (to those observed for wild-caught yellowtail) should result in substantial cost savings for feed in aquaculture operations.

Pikeperch ( Sander lucioperca ) is a popular fish for human consumption and decreasing wild catches increase the demand for aquaculture production. Limited knowledge of the species' requirements under intense recirculating aquaculture system (RAS) culture conditions has motivated this study to focus on the effect of elevated carbon dioxide (CO 2 ) levels on pikeperch metabolism. The trial was conducted in a recirculating aquaculture respirometer system with pikeperch (average body weight 251.9 g) and three hypercapnia regimes over 58 feeding days. Food grade CO 2 gas was gradually added to the medium (15 mg L − 1 ) and high (30 mg L − 1 ) treatments while no gas was added to the low treatment (hence 4 mg L − 1 ). Fish were fed daily for 10 min with a commercial diet (ALLER Metabolica). O 2 , T, pH, CO 2 were measured individually for each tank and logged every 2 h to calculate oxygen consumption rates of each treatment. Total Ammonia-Nitrogen was measured monthly for individual tanks and used to calculate TAN excretion. Results showed a linear decrease of 6% in final body weight with increasing CO 2 levels between the low and the high CO 2 treatment. Feed intake was linearly increased after four weeks of the experiment from 0.97 ± 0.07% in the low CO 2 treatment to 0.86 ± 0.03% in the high CO 2 treatment but the effect faded after eight weeks, indicating a habituation to the hypercapnia conditions. High levels of CO 2 were associated with reductions in haematocrit and metabolic oxygen consumption. The results suggest that adult pikeperch can survive carbon dioxide concentrations of up to 30 mg L − 1 when other water quality parameters are in acceptable levels but will be affected in metabolism already at moderate CO 2 levels of 15 mg L − 1 .

We compared oxygen consumption (MO 2 , mg/kg/h) of c. 80 g rainbow trout ( Oncorhynchus mykiss ) in an intermittent-flow swim respirometer at 15 °C. Before the tests the fish were grown in flow through tanks (15 °C) with either fishmeal (FM) or corn gluten meal (CGM) based diets (c. 52% protein) for a period of 3–4.5 months. Ten individuals from both treatment groups were fasted for 48 h before the swim test, which consisted of 18 loops of 210 s over three different periods: acclimation period (6 loops at 0.5 body lengths per s, BL/s), exercise period (8 loops at increased speed from 1 to 2.5 BL/s with recovery loops at 0.5 BL/s), and a recovery period (four loops at 0.5 BL/s). We did not observe significant differences in MO 2 between the two groups at any of the three measurement periods (repeated measures-Anova). The maximum (mean ± SE) MO 2 values, measured during the last exercise period at 2.5 BL/s, did not differ significantly between the treatments: 404 ± 18.7 mg/kg/h and 427 ± 50.6 mg/kg/h in FM and CGM groups, respectively. Our result supports an earlier finding that origin of the protein does not affect MO 2 during swimming in salmonids. This is the first report of the effect of a plant protein on MO 2 of a carnivorous fish during forced swimming, and these data lend support to further development of sustainable diets to replace fishmeal with plant proteins.

Land-based aquaculture is an increasingly important method of fish production, and fish grown in such systems may be exposed to substantially higher carbon dioxide concentrations than fish in the wild. Chronic exposure to elevated CO2 levels in recirculated aquaculture systems can correlate with lower growth and condition indices for many fish species, however, the physiological basis behind this loss of performance is largely unknown. The aim of this study was to investigate the growth, condition and protein catabolism rates of juvenile turbot (55-176 g) reared for 8 weeks at three different dissolved carbon dioxide concentrations: 5, 26, and 42 mg l(-1) (-3000, 15000, 25000 mu atm; pH 7.37, 6.66, 6.44). A commercial diet was administered once per day until satiation, and uneaten food was collected from a solids collector. Oxygen consumption and ammonia excretion were measured weekly using high precision automated methods in a recirculating aquaculture respirometer system. Increased CO2 levels were associated with reduced condition factor, feed intake and weight gain. Compared to the low CO2 treatment, the specific growth rates under the medium and high treatments were reduced by 21% and 58%, respectively. Feed conversion ratios were similar between treatments. The oxygen consumption rates broadly followed a dose-response pattern, where fish in the low CO2 treatment exhibited the highest respiration rates. Comparison of ammonia quotients over time and at comparable feed intake showed the rates of protein catabolism correlated with CO2 exposure levels. By the end of the 8 week trial fish from the high CO2 treatment exhibited up to 3 times the protein catabolism rates observed in the low treatment, and the medium treatment was approximately intermediate between the two. The conclusion from the study was that the loss of growth and condition of turbot reared at elevated CO2 concentrations (relevant to land-based aquaculture systems) can be traced to decreased feed intake and an increased reliance on protein as a fuel source. (C) 2015 Elsevier B.V. All rights reserved.

Two stocking densities, “low” (L, between ~ 19 and ~ 25 kg m − 3 ) and “high” (H, between ~ 75 and ~ 100 kg m − 3 ) were compared for effects on specific growth rate (SGR), feed conversion, energetics and welfare of rainbow trout reared at 14 °C either in static water (S) or swimming in a gentle current of ~ 0.9 bodylengths s − 1 (C). Trout (initial mass ~ 110 g) were reared for 9 weeks in circular tanks (volume 0.6 m 3 ), in triplicate of four conditions (LS, LC, HS, HC). Fish were fed ad-libitum daily; waste pellets were swirl-collected at the outflow to calculate feed intake. SGR was measured each three weeks for the last six weeks of the trial. The tanks functioned as intermittent-stopped flow respirometers, to permit metabolic rate to be measured as instantaneous oxygen uptake once per hour. Mean (± SD) SGR was significantly lower at H than L (1.51 ± 0.03 vs 1.44 ± 0.04% day − 1 , respectively, n = 6) and lowest in HC. When compared over a similar interval of mass gain, H groups had approximately 25% higher metabolic rates than L, with the highest rates in the HC condition. As a result, fish in the H groups dissipated a greater amount of feed energy as metabolism and, across all groups, there was a direct negative relationship between the quantity of energy dissipated and their SGR. There was no evidence of a neuroendocrine stress response, plasma cortisol was around 1 ng ml − 1 in all conditions. An acute crowding stress increased plasma cortisol to above 120 ng ml − 1 in all groups, but C groups recovered to control levels within 8 h whereas S groups required 20 h. Respirometry on individuals revealed that H fish had approximately 14% higher metabolic rates than L fish, indicating that increased metabolic rate in rearing tanks was in part physiological. The H groups had approximately 15% lower critical swimming speeds than the L groups which, together with their raised metabolic rate, indicated a physiological impairment. Thus, high density reduced SGR by raising energy dissipation, at least partially as a physiological response by the fish, although there was no evidence of an endocrine stress response. The only beneficial effect of C was in recovery from acute stress.

Cultured adults of ezo abalone, Haliotis discus hannai (shell length, 89.3 ± 6.4 mm and flesh dry weight, 13.0 ± 1.6 g; n = 12) were exposed to different temperatures (10 and 25 °C) to determine whether respiration effects were induced by artificial closure of the second and third tremata (respiratory pores). A respirometer was used to determine the oxygen consumption rates (OCRs) as measures of metabolic activity. The closed tremata were the second and third of the four open tremata anterior to the head of the abalone. The OCRs of starved abalone were measured under constant conditions (CC: constant dark and constant temperature) during a 240-h period, consisting of 120 h before and 120 h after the closure of tremata. The endogenous rhythm of the OCRs in cultured ezo abalone exhibited a dominant circadian rhythm (unimodal rhythm) in the latter half of the experimental period and occasionally showed a weaker but similar circatidal rhythm (bimodal rhythm) in the first half of the experimental period regardless of temperature. The results from the present study indicate that the rhythmicity of the OCRs in starved abalone is not affected by closure of the second and third tremata. This study offers essential physiological information for utilizing tremata in developing a tagging technique in abalone.

This study investigated whether two farmed rainbow trout families that differed in two production traits, size at age (SA) and condition factor (CF), also differed in aspects of their physiological energetics and cardiorespiratory performance. Five groups of a family with large SA (LSAF) and six groups of a family with smaller SA (SSAF) were reared in tank respirometers in freshwater at 14 °C for 84 days. The LSAF grew from a mean (± SD) mass of 182 ± 6 g to 449 ± 24 g, a significantly higher mass gain than the SSAF, which grew from 77 ± 4 g to 307 ± 22 g. The LSAF had a higher lifetime specific growth rate (SGR) but, contrary to expectations, exhibited a lower SGR than the SSAF when compared over a mean mass interval of approximately 180 g to 300 g. This was a result of lower daily rates of feed intake coupled with higher metabolic rates in the LSAF during daylight feeding hours, this latter apparently due to increased spontaneous activity. Thus, a higher lifetime SGR in the LSAF presumably reflected rapid growth at earlier life stages, and a large familial SA may bring a tendency to increased aggressive behavioural interactions as fish approach marketable size. Instantaneous fluxes of O 2 , CO 2 and waste nitrogen in the tank respirometers immediately after feeding revealed that lipid fuelled over 50% of metabolism, protein approximately 40% and carbohydrates less than 10% in the families. When, however, feed had been withheld for 24 h, protein fuelled less than 20% of metabolism and carbohydrate increased to over 20%. The LSAF exhibited higher critical swimming speeds, maximum metabolic rates and aerobic metabolic scopes than the SSAF, indicating that selecting broodstock for large SA does not necessarily compromise functional integrity. The SSAF had a more rounded ventricular morphology than the LSAF, and also a higher CF. These results are consistent with other literature reports whereby familial CF in farmed trout is an indicator of ventricular morphology and cardiorespiratory performance.

We are unaware of any assessments of fish welfare during live-hauling of adult salmon in very high numbers (> 10,000 fish) and at high density (∼100 kg/m 3 ) and yet live transport of adult salmon from sea cages to processing plants is now a common practice. Here we report on the bulk metabolic rate of adult Atlantic salmon (S almo salar L.) during transport from a sea farm off the west coast of Vancouver Island, BC, Canada, on board a state-of-the-art live-haul vessel, the Sterling Carrier . Monitoring the oxygen concentrations of the water entering and leaving the flooded holds revealed that oxygen uptake decreased from > 8 mg O 2 /min/kg to an average 2 /min/kg within the first 20 min of the vessel being underway. During the fourth hour of transport, oxygen uptake averaged 3.1 mg O 2 /min/kg, a value comparable with routine oxygen uptake values measured under laboratory and field conditions for single adult salmon in a swim respirometer. This finding suggests that adult Atlantic salmon quickly recovered from the stress of loading on to the Sterling Carrier . This conclusion was corroborated by visual observations of the fish in the live holds, which revealed that fish faced the water flow and ventilated lightly while slowly cycling their position in a schooling behavior during the 11-h journey. Thus, the live transport conditions on board the Sterling Carrier appeared to promote good welfare of adult Atlantic salmon during the 11-h journey from a sea farm to a processing plant.

Kuruma prawns (Penaeus japonicus) are immobilised by cooling and then handled individually when packed for live shipment out of water. An automatic respirometer, with modifications to improve water circulation, was used to measure the respiration rate of settled and handled adult P. japonicus at 12, 17 and 22°C. Handling increased the respiration rate of the prawns at the two highest temperatures but had no effect at 12°C. Thus, the contribution that handling normally made to metabolic rate was removed when the prawns were cold “anaesthetised”.

This paper outlines a simple, rapid, potentiometric method for the determination of respiration rates of aquatic organisms weighing from 10 μg to 10 mg dry weight. The procedure employs the oxygen electrode of a Radiometer Blood Gas Analyzer. Syringes serve as the respirometry chambers. The sample volume of the Blood Gas Analyzer is 200 μl, allowing the determination of respiration rates of small animals in respirometer volumes as small as 1 ml. Since the method is potentiometric, it allows the determination of the oxygen-dependent respiration rate for these small animals.

The use of fish farm production and fry tanks as large-scale respirometers proved very effective. The high stocking densities maintained in the tanks, resulted in a rapid decline in dissolved oxygen saturation after water and oxygen supplies were interrupted. The measurement of this decline together with fish biomass and number, water temperature, salinity and atmospheric pressure enabled the oxygen consumption rate of the fish to be calculated as a function of body weight. Fish size on the farm ranged from 4 to 1000 g and over a period of 2 years, oxygen consumption determinations were made at temperatures ranging from 7 to 16°C. The relationship between oxygen consumption rate and mean weight of the fish was fitted statistically into five temperature groups of 2°C spread, i.e. 7–8°C, 9–10°C, 11–12°C, 13–14°C, 15–16°C. The relationship between oxygen consumption rate, fish size and temperature was similar to that of salmonids, although the rates of oxygen consumption were only about one half.

The effects of population density and dissolved oxygen tension on the routine metabolism of 2 kg, 2-year-old white sturgeon, Acipenser transmontanus, were investigated, using a closed respirometer. The routine metabolic rate of post-absorptive fish averaged 94.3±3.4 mg O2/kg0.66h−1 (x±SE) at 18°C, and overall metabolism increased (P 130 mm Hg) metabolic rates were not significantly different within a stocking density. Feeding and handling fish significantly increased their metabolic rate compared with starved fish (P

An automatic continuous-flow respiration system which allows the monitoring of oxygen consumption in six chambers (five experimental and one control) for ca. 10 min every hour is described. The valve system (a teflon inner disk and a perspex holder) is described and illustrated and specifications listed in table form.

Bioenergetic relations of body weight and feeding level in C. lazera were studied in open circuit balance respirometers to elucidate the physiological background of the highly efficient feed conversion in this fish. It was found that changes in proximate body composition that occurred at different feeding levels were largely attributable to concurrent changes in weight. The various body components were allometrically related to body weight. The same was true for the daily oxygen consumption where the weight exponent equalled 0.86 ± 0.02 (S.E.) for fasting fish and 0.75 ± 0.01 (S.E.) for feeding fish. The primary effect of feeding level was in the overall level of metabolism, which increased more than 3-fold from fasting to satiation feeding. The metabolic “scope for growth” was 0.346·W0.75−0.145·W0.83(kJ/day). The metabolizability of the feed energy was about 70% decreasing with the feeding level. ME utilization for energy gain above maintenance was 80% efficient, independent of body weight and feeding level. The intake of ME for gain was calculated to decrease from 6.9 to 2.8 times the maintenance requirement for fish of 1 to 200 g. This high ME p ME m ratio largely explains C. lazera's efficient utilization of the feed for growth.

A description is given of an open circuit balance respirometer for bioenergetic studies of fish growth using indirect calorimetry. The installation was designed to enable the determination of gas and matter balances of fish, including air breathing species, during prolonged experimental periods. Design requirements, as well as constructional and operational characteristics, are given.