Effects of oxygen supersaturation on the culture of cutthroat trout, Oncorhynchus clarki Richardson, and rainbow trout, Oncorhynchus mykiss Richardson

Abstract. Two studies were conducted to determine the effects of rearing Snake River cutthroat trout, Oncorhynchus clarki Richardson, and Eagle Lake rainbow trout, Oncorhynchus mykiss Richardson, in oxygen supersaturated water. The performance of cutthroat trout held at oxygen saturation as high as 172% was compared with that of control fish held in water at or below saturation. At an oxygen saturation level of 172%, total gas pressure reached 117% in late afternoon, and nitrogen saturation was reduced to 93%. The rainbow trout were held at a maximum of 150% oxygen saturation; total gas pressure did not exceed 112% in late afternoon and nitrogen saturation was reduced to 99%. Fish growth, fin quality and feed conversions were not significantly affected in either species. At the termination of the study gas bubble disease was observed in 94% of the cutthroat trout held in oxygen supersaturated water. Gas bubble disease was not observed in rainbow trout.     

Oxygen-induced gas bubble disease in rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract. An Aquatector oxygen injection unit was used to supersaturate a hatchery water supply to 200% oxygen saturation (18–20mg/l) and increase the total gas pressure to 120% of saturation. Nitrogen saturation was reduced to near 100%. Rainbow trout, Oncorhynchus mykiss (Walbaum), held in the treated water developed signs of gas bubble disease in 4 days, and 50% died within 20 days. We demonstrated that supersaturated total gas pressure due to excessive oxygen saturation causes gas bubble disease in the absence of supersaturated nitrogen gas. It is recommended that users of oxygen injection systems closely adjust the amount of oxygen added to the water to keep the total gas pressure near saturation.     

Total gas pressure and oxygen and nitrogen saturation in warmwater ponds aerated with airlift pumps

Gas bubble disease and improper inflation of swim bladders in larval striped bass Morone saxatilis have been recently related in laboratory studies to very low levels of gas supersaturation. In other species, kills resulting from gas supersaturation have been reported in natural waters as large as Galveston Bay. We monitored warmwater ponds during spring to determine the extent of naturally occurring gas supersaturation and compared these levels with levels of gas saturation in ponds equipped with airlift pumps. Total gas pressure averaged 110% in the morning at the surface of non-aerated ponds and in the afternoon in ponds with airlift pumps. At other times of the day total gas pressure averaged 106–107% at the surface and bottom, morning and afternoon, in both aerated and non-aerated ponds. No evidence of gas bubble disease was found in 15-day-old striped bass fry cultured for 42 days in either aerated or non-aerated ponds.     

The tolerance threshold of Chinese sucker to total dissolved gas supersaturation

Total dissolved gas (TDG) supersaturation generated in the river may result in gas bubble disease to Chinese sucker (Myxocyprinus asiaticus Bleeker) and cause their mortality. To assess the effects of TDG supersaturation on Chinese suckers in laboratory, juvenile fish were exposed to different levels of TDG supersaturated water. All of the fish died when the TDG saturation reached and exceeded 125%, but none died at TDG of 120% saturation in 96 h. To evaluate the effects of intermittent exposure of TDG supersaturation, Chinese suckers were exposed to TDG of 130% for a specific duration and then provided a recovery period at 100% saturation. The results showed that some remission is possible for intermittent exposure. Because of the characteristics of natural rivers, experiments exploring the TDG supersaturation detection and avoidance abilities of Chinese suckers were conducted and demonstrated the fish can avoid TDG supersaturation in both the horizontal and vertical directions when higher TDG levels were available. The results indicate the tolerance threshold of juvenile Chinese suckers is a TDG level of 120% saturation.     

长薄鳅对过饱和总溶解气体的回避特征研究

高坝泄洪过程中,高速水流造成下游水体的总溶解气体(Total Dissolved Gas,TDG)过饱和极易使得水体中的鱼类患上气泡病,进而对下游水体的鱼类生存造成威胁。为了探究长薄鳅(Leptobotia elongate)幼鱼对TDG过饱和水体的探知回避能力,本实验以2月龄的长薄鳅为研究对象,记录其在不同TDG饱和度水体中的反应和趋向。结果表明,在120%TDG过饱和水体中,长薄鳅回避率为-20%,其对该饱和度下的水体表现出了一定的趋向性;TDG饱和度为130%时,长薄鳅回避率为-2%,无明显回避能力;TDG饱和度为140%时,长薄鳅展现出微弱的回避特征,其在清水与过饱和水体之间往复游动,最终回避率为12%;150%TDG过饱和水体中,长薄鳅体现出敏锐的探知能力,1~2 min后开始频繁游动,同时具有一定的回避能力,回避率为34%。长薄鳅的回避率与过饱和水体浓度呈现较强的线性相关关系,水体TDG饱和度越高,实验鱼回避现象越明显。     

The effect of free ammonia nitrogen,pH and supplementation with oxygen on the growth of South African abalone,Haliotis midae L. in an abalone serial‐use raceway with three passes

The farming of abalone, Haliotis midae L., can be intensified in serial‐pass systems, but water re‐use increases the concentration of NH₃ (free ammonia nitrogen, FAN) and reduces water pH. Changing the percentage dietary protein from 33% to 26% reduced the concentration of FAN (F_{42, 252} = 2.79; P < 0.0001) in a serial‐pass system and did not reduce weight gain (F_{1, 12} = 1.09; P = 0.31) or length gain (F_{1, 12} = 1.08; P = 0.31). Low water pH was the most important variable to contribute to a reduction in abalone growth (weight gain: F_{1, 19} = 64.5; P < 0.0001; r² = 0.76; length gain: F_{1, 19} = 41.9; P < 0.0001; r² = 0.67). In addition, supplemental oxygen (103% saturation) improved length gain (t = 3.45, P = 0.026) in abalone exposed to an average FAN concentration of 2.43 ± 1.1 μg L^?1) and an average pH value of 7.6 ± 0.13, relative to a treatment with no oxygen supplementation. Thus, in an abalone serial‐use raceway with three passes, FAN was not the first growth‐limiting variable. It is suggested that future studies should examine the major causes of reduced water pH in serial‐use systems and their effect on the growth and health of H. midae.     

Effects of adult stocking density on egg production and viability in cultures of the calanoid copepod Acartia tonsa (Dana)

The effect of stocking density of the calanoid copepod Acartia tonsa was evaluated in a 96 h rearing experiment. Possible density‐dependent egg production and egg viability were analysed at stocking densities of 100, 200, 300, 400 and 600 adults L⁻¹. Temperature, oxygen saturation and algal concentration were kept optimal. A non‐density‐dependent mortality rate of 15–19% day⁻¹ was documented. A non‐significant density‐dependent egg production was observed between 100 and 600 adults L⁻¹. The average egg production was 22.5±8.8 egg female⁻¹ day⁻¹ in all densities. The average egg hatching success was 84.7±4.8% and was never observed below 76.1%, with no significant differences across the stocking densities. Conclusively, as a practical recommendation for the aquaculture industry, copepod cultures with densities ranging from 100 to 600 adults L⁻¹ and presumably even more dense cultures are possible with the studied species obtaining a steady egg production and still high egg viability.     

An explanation for the high resistance of incubating salmonid eggs to atmospheric gas supersaturation of water

Embryonic stages of development within the salmonid egg are more resistant to the effects of atmospheric gas supersaturation, compared with later stages following hatching. We show that the hydrostatic pressure maintained under the capsule (zona radiata) of the egg is sufficient to compensate for a substantial portion of the excess total gas pressure to which the egg may be exposed in supersaturated water. That is, total gas pressure thresholds for gas bubble trauma are raised above those applying to later developmental stages, following hatching, as a result of normal infracapsular pressure.     

Effects of Water Hardness and Calcium: Magnesium Ratios on Reproductive Performance and Offspring Quality of Macrobrachium rosenbergii

This study evaluated the effect of specific calcium and magnesium ratios at two hardness values on reproductive performance and offspring quality of Macrobrachium rosenbergii brood‐females. Hatchery water containing 110.5 mg/L CaCO3 hardness was considered baseline as it has been used successfully to hatch and rear larvae and was used as the control treatment. At each hardness value of 150 and 190 mg/L CaCO₃, four experimental water treatments were made in triplicate. Each treatment was adjusted using soluble salts (CaCl₂·H₂O, MgSO₄·7H₂O, and MgCl₂·6H₂O) to provide the hardness and calcium to magnesium ratios of 0:20, 20:80, 50:50, and 80:20 needed. Each of the experimental tanks (140 L) were stocked with six females and one male. The results indicated that both hardness and Ca:Mg ratios affect brood‐female reproductive qualitative parameters such as intermolt period, egg hatchability, egg dry weight, and egg‐clutch somatic index (ESI) parameters (P < 0.05) but not fecundity and eggs per spawn. The results revealed that brood‐females at 150 mg/L hardness showed greater reproductive performance than at 190 and 110.5 mg/L hardness. The findings also demonstrated that the treatment 50Ca50Mg at 150 mg/L hardness with 38.8 mg/L calcium and 12.9 mg/L magnesium had optimum reproductive performance and offspring quality for M. rosenbergii brood‐females.     

高密度养鱼增氧方法分类与溶解氧超饱和度及水中气泡直径大小阈值的关系研讨

每一种增氧机,都依照一定的增氧原理进行增氧。对增氧有关基础理论的深入探讨,有助于机器增氧效率的提高和一代机型的更新,这对高密度养鱼业和环保业的发展,将具有重要的意义。为此,本文首先阐明了溶氧饱和度和超饱和度的概念,将溶氧在水中的物理状态与饱和度的关系作了深入的探讨,并由此提出增氧方法可按溶解度的特性分为“液     

Dietary vitamin C and E supplementation and reproduction of milkfish Chanos chanos Forsskal

Milkfish Chanos chanos Forsskal broodstock (11 years old, average body weight 5.23–5.73 kg) reared in 10‐m‐diameter by 3‐m‐deep floating net cages (31–36 fish per cage) at SEAFDEC AQD's Igang Marine Substation in Guimaras Island, central Philippines, were fed daily at 3% of total body weight formulated diets (36% protein, 7–8% lipid) supplemented with 0.1% vitamin C, 0.05% vitamin E, both vitamin C and E or no vitamin supplementation (control) for 3 years. Reproductive performance was assessed in an attempt to determine the optimum nutrition for successful spawning of milkfish. The total egg production, mean number of eggs per spawning, number of spawns and mean egg diameter were not affected by dietary vitamin C and E supplementation. However, broodstock given dietary supplementation of vitamin C alone or in combination with vitamin E had a higher percentage of spawns with higher (> 90%) percentage egg viability, hatching and cumulative survival rate than those of the control. Broodstock given dietary vitamin E supplementation alone had few spawns, which made the results difficult to analyse. The results confirm the essentiality of vitamin C supplementation in producing more spawns with good egg and larval quality. The production of an adequate volume of good quality eggs and larvae to support hatchery operation is necessary to offset the huge investment in broodstock development, as it takes at least 5 years for milkfish to attain sexual maturation and spawning.     

Hatching rate of Chinese sucker (Myxocyprinus asiaticus Bleeker) eggs exposed to total dissolved gas (TDG) supersaturation and the tolerance of juveniles to the interaction of TDG supersaturation and suspended sediment

Flood discharge containing excessive suspended sediments (SS) can result in total dissolved gas (TDG) supersaturation downstream of dams. It has been confirmed that high TDG levels and excessive SS cause serious threats to fish survival. To explore the effects of TDG supersaturation on the hatchability of Chinese sucker (Myxocyprinus asiaticus Bleeker) eggs, eggs were exposed to 100%, 125%, 130% and 135% TDG supersaturated water. The results showed that the hatching rates were 78.25%, 75.35%, 71.30% and 67.50% at the 100%, 125%, 130% and 135% TDG respectively. The hatching rate decreased with increasing TDG levels. Furthermore, acute lethality experiments were carried out to investigate the interaction of TDG supersaturation and SS on Chinese sucker. Half‐year‐old juveniles were exposed to TDG supersaturated water with SS concentrations of 0, 200, 600 and 1,000 mg/L, and the TDG levels were 125%, 130%, 135% and 140% respectively. The fish exhibited abnormal behaviours and signs of gas bubble disease. Mortality increased with increasing TDG levels and SS concentrations. The Chinese suckers only survived for 2.5 hr at 140% TDG and 1,000 mg/L SS. Moreover, an increase in SS in TDG supersaturated water could cause a decrease in the median lethal time (LT₅₀). When the TDG level reached 140%, the LT₅₀ declines significantly at 600 and 1,000 mg/L SS. The interaction of TDG supersaturation and SS was significant at LT₅₀ (F = 22.81, df = 9, p < 0.001). The results indicate that the combined effect of TDG and SS could be great on Chinese sucker.     

Hypoxic conditions induce centrum defects in red sea bream Pagrus major (Temminck and Schlegel)

A previous study elucidated that an extreme hypoxia during somitogenesis induced the most frequent skeletal malformation centrum defects in red sea bream (RSB), Pagrus major. In this study, details of the hypoxic conditions to induce them in RSB, dissolved oxygen (DO) concentration and exposure time to hypoxia, were investigated. Fertilized eggs were exposed to seawater of six DO concentrations (0%, 10%, 25%, 50%, 75% and 100% of saturation) for seven different periods (5, 10, 30, 60, 120, 240 and 360 min) during somitogenesis. Somitic disturbances in newly hatched larvae were induced by exposure to 0% and 10% DO concentration for 10 and 120 min and longer respectively. Rearing eggs exposed to hypoxic condition of 10% DO for 240 min for 40 days post‐hatch showed that the location and the frequency of somitic disturbances in larvae and centrum defects in juveniles were significantly correlated (P<0.01). Dissolved oxygen concentration of the interstitial water in the egg high density layer formed at the water surface in a stationary state abruptly decreased to 3.7% within 7 min. Centrum defect induction by exposure of eggs to extreme low DO concentrations for a short period, which is the probable situation in the practical juvenile production, suggests that careful maintenance of DO concentration is important in the incubating water of fertilized eggs during egg sorting and transportation, where eggs are made into a pile and undergo hypoxia, for the prevention of centrum defects.     

Some effects of gas-supersaturated seawater on Spisula solidissima and Argopecten irradians

Two size classes of the surf clam, Spisula solidissima, and the bay scallop, Argopecten irradians, were exposed to different concentrations of gas-supersaturated seawater in a flowing seawater system. Both species tested experienced no mortality when held in the control treatment maintained at 96% oxygen and 109% nitrogen. Mortality, gill tissue damage, gas emboli, membranous tissue blisters, and abnormal secretion of shell material were induced experimentally at elevated levels of gas supersaturation. Results indicate significant mortalities of surf clams and scallops held at 114% O₂ and 195% N₂, and at higher levels of gas concentration. These values suggest a point of reference for the bivalve culturist in identifying potential problems which can be caused by gas-supersaturated seawater.     

不同氨氮和溶解氧条件下循环海水养殖系统生物滤池对氨氮、化学耗氧量及颗粒悬浮物的处理效果

为了建立优化的循环海水养殖系统,采用水质国标检测方法分析了珊瑚石生物滤池在不同氨氮和溶解氧(DO)负荷实验条件下对养殖废水中氨氮、化学耗氧量(COD)及颗粒悬浮物(SS)的处理效果。结果显示,进水氨氮浓度对出水氨氮(正相关)、COD(正相关)均有极显著的影响(P0.01),对SS处理效果影响不显著。当进水氨氮浓度为0.45~0.65 mg/L时,滤池对水体处理效果最优(氨氮平均清除率为82.1%±3.3%;COD平均清除率为7.1%±1.5%;SS平均清除率为5.8%±1.6%)。DO浓度对水体氨氮(负相关)和COD(负相关)处理效果的影响显著(P0.05),对SS处理效果影响不显著。DO浓度为5.0~7.0 mg/L时,水体处理效果最优(氨氮平均清除率为78.7%±3.5%;COD平均清除率为23.0%±5.3%;SS平均清除率为7.1%±2.0%)。因此,本实验环境下的循环海水养殖系统珊瑚石生物滤池在氨氮浓度为0.45~0.65 mg/L,DO浓度为5.0~7.0 mg/L时,对水体中的氨氮、COD、SS的综合处理效果最优。     

Effects of oxygen supersaturation and temperature on juvenile greenlip, Haliotis laevigata Donovan, and blacklip, Haliotis rubra Leach, abalone

Growth and survival of juvenile greenlip (39.03 (SD 3.80) mm (n=524)) and blacklip (31.92 (SD 4.19) mm (n=531) abalone were investigated at high dissolved oxygen levels (95–120% saturation) between 17 and 19°C. Abalone were fed the same artificial diet and each species was contained in groups of approximately 30 individuals within triplicate tanks for each of six treatments and were exposed to flow through water adjusted to give experimental conditions for up to 75 days. Blacklip abalone held at 16.9°C and 97% oxygen saturation grew in shell length significantly faster than all other treatments of blacklip abalone held at 19°C, and significantly faster than blacklip abalone maintained at 111% oxygen saturation and 17.5°C. Both temperature and oxygen saturation significantly affected the survival of this species. Blacklip abalone held at 19°C had significantly lower survival for both 96% oxygen saturation and 120% oxygen saturation, compared with blacklip abalone maintained at either 110% oxygen saturation and 19°C, or for any 17°C treatment. No significant differences were noted for greenlip abalone within the range tested in terms of growth rate, food consumption rate or survival, indicating that greenlip abalone tolerated these conditions better than did blacklip abalone.     

Effects of Intensification of the Amazon River Prawn,Macrobrachium amazonicum,Grow‐out on Effluent Quality

Studies to determine suitable levels of intensification are essential for developing sustainable aquaculture. The objective of this study was to evaluate the quality of effluents discharged from ponds stocked with 10 (D10), 20 (D20), 40 (D40), and 80 (D80) postlarvae of Macrobrachium amazonicum/m². Intake and effluent water samples were taken throughout a 5.5‐mo grow‐out cycle. In that study, twelve 0.01‐ha earthen ponds were stocked postlarvae with 0.01 g. Average water exchange rate was 15%/d; water was discharged from the bottom of the ponds. Prawns were fed a commercial feed with 38% crude protein according to their biomass (3–10%) and the concentration of dissolved oxygen (DO). In our research, temperature, turbidity, total suspended solids, conductivity, DO, pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), N‐ammonia, N‐nitrite, N‐nitrate, N‐Kjeldahl nitrogen, total phosphorus, and soluble orthophosphate were measured every 15 d throughout the experiment in the early morning (0630 to 0730 h). Turbidity was lower in D10 than in D20 and D40 and total phosphorus was higher in D80 than in D10 and D20. An analysis of principal components comparing treatments and intake water showed three groups: intake, D10 and a cluster of D20, D40, and D80. On the basis of the water characteristics found in our study it appears that the farming of M. amazonicum is likely to have a low environmental impact, at least up to a stocking density of 80 prawns/m².     

Relationship between biological characteristics of eggs and female brood stocks of Persian sturgeon <Emphasis Type="Italic">Acipenser</Emphasis><Emphasis Type="Italic">persicus</Emphasis>: a comparison with other fish species

We have determined a number of biological characteristics of the Persian sturgeon egg (including diameter, surface-to-volume ratio, yolk sphere and perivitelline space) and of female brood stocks (including age, length, weight, condition and absolute fecundity) in 420 specimens of the migratory population of Acipenser persicus in Gorgan bay of Iran from 2001 to 2004. In the hydrated egg, the average egg diameter, yolk diameter, surface-to-volume ratio and yolk sphere-to-perivitelline space ratio values were: 3.64 ± 0.17 mm, 3.26 ± 0.25 mm, 1.65 ± 0.08 and 0.75 ± 0.01, respectively. In this chondrostean species, the egg surface and volume were found to increase with increasing egg diameter, but the egg surface-to-volume ratio decreased. In Persian sturgeon, the surface-to-volume ratio and yolk sphere-to-perivitelline space ratio is very high; therefore, the metabolic rate is low and female spawning occurs in low-temperature waters. The statistical Pearson correlation between egg diameter relative to a number of brood stock characteristics, including fork length (r = 0.059), weight (r = 0.140), age (r = 0.081) and absolute fecundity (r = 0.095), were not significantly different (P > 0.05). An extensive comparison of these results with data published on other fish species is presented and discussed.     

Effect of Environmental Factors on Development of Rotifer and Copepod Nauplii Populations in Sunshine Bass Morone chrysops×M. saxatilis Nursery Ponds without Fish

Knowledge of the effect of environmental factors on timing and production of zooplankton populations would enable sunshine bass Morone chrysops × M. saxatilis farmers to stock fry when live food is most available and thereby increase fry survival. Relationships of morning water temperature, morning and average daily air temperature, day length, number of rain days and daily rain fall, and dissolved oxygen concentrations to time required for rotifer and copepod nauplii populations to peak in freshly filled freshwater nursery ponds was determined. Relationships of the same independent variables to concentrations of rotifers and copepod nauplii at the peak were also determined. For rotifers, day length, dissolved oxygen, and water and air temperatures were highly correlated with time to the peak density, but not concentration of rotifers. Time required for copepod nauplii densities to peak was associated with rain events; whereas, nauplii concentration was related to day length, dissolved oxygen levels and, to a lesser extent, water and air temperatures. Regression equations of the independent variables had very low predictive value for rotifer or nauplii densities or time to reach initial peak nauplii populations. Regressions of day length, morning water temperature, morning and average daily air temperature had moderate values ( r ² > 0.7) for predicting time to initial peak rotifer densities.     

Induced Spawning and Egg Quality Evaluation of Red Snapper, Lutjanus campechanus

Brood red snapper, Lutjanus campechanus, were captured from the wild and induced to ovulate by human chorionic gonadotropin (hCG) injection; eggs and sperm were manually stripped; and the eggs were artificially fertilized. Eggs were evaluated by the following egg quality parameters: buoyancy, fertilization, egg size, and oil globule size and number. The relationship of these egg quality parameters and brood characteristics (female size, fecundity, time of year, and response time to ovulation) to 36 h posthatch larval survival was considered. Injection of wild‐caught red snapper females with 1100 IU/kg of hCG resulted in 75% of the females ovulating. The average fecundity was 343,377 ± 30,805 eggs/kg, with a mean percent fertilization of 79.0 ± 1.74%. The mean percentage of floating eggs per spawn was 91.8 ± 1.75%. Mean egg diameter for floating eggs was 778.3 ± 2.09 μm, with a mean oil globule diameter of 117.5 ± 1.53 μm. Brood‐related characteristics were a better predictor of larval survival than postovulation egg characteristics. The percentage of floating eggs in a spawn was not correlated to larval survival. Spawns with eggs having a single oil globule had a similar larval survival as those eggs where multiple globules were common. No clear relationships were found for any one factor and larval survival, but rather a combination of factors was more predictive of survival, most notably spawn date, fecundity, and response time following hCG injection.