Effect of salinity and body weight on ecophysiological performance of the Pacific white shrimp (Litopenaeus vannamei)

Ecophysiological responses of Litopenaeus vannamei were evaluated as functions of environmental salinity and animal size. Growth rate, routine metabolic rate, limiting oxygen concentration, and marginal metabolic scope were determined for L. vannamei acclimated to, and tested at, salinities of 2, 10, and 28 ppt, all at 28 °C. Routine metabolic rate (RMR), estimated as oxygen-consumption rate per unit body weight for fasted, routinely-active shrimp, was independent of salinity but decreased with increasing shrimp weight. Limiting oxygen concentration for routine metabolism (LOCr) decreased with increased shrimp weight for the 10 and 28 ppt treatments, but not for the 2 ppt treatment. Marginal metabolic scope (MMS = RMR/LOCr) also decreased with increasing shrimp weight and was independent of salinity. Growth rate was significantly less at 2 ppt than at either 10 or 28 ppt, which gave similar growth rates.     

The metabolic rate of roach in relation to body size and temperature

Standard and routine metabolic rates of roach Rutilus rutilus for a wide size and temperature range (3–200 g, 5–23° C) were analysed by automated, computerized intermittent flow respirometry. The mass exponent b ranged from 0·68 to 0·82 for standard metabolism, and from 0·65 to 0·92 for routine metabolism depending on the experimental temperature. For routine metabolism b was lowest at 10° C. At both decreasing and increasing temperatures, b increased significantly. Roach were exponentially temperature-dependent for both metabolic levels. For roach <20 g, however, an asymptotic relationship was observed between temperature and routine metabolic rate. The 'flattening of the curve' in the latter case may be explained by reduced spontaneous activities at the lower threshold of the preferred temperature range.     

Influences of body mass,temperature, oxygen tension,and salinity on respiratory oxygen consumption of cyprinodontoid fishes of three families

This review evaluates the current state of knowledge of influences of body mass, ambient temperature, P_O2, and salinity on routine metabolic rates of members of three families, Fundulidae, Cyprinodontidae, and Poeciliidae, belonging to the order Cyprinodontiformes. The study was motivated by Winberg’s (Fisheries Research Board of Canada, Translation Series No. 194. Distributed by the Fisheries Research Board of Canada Biological Station, Nanaimo, BC, 1960) conclusion that the Cyprinodontiformes (Winberg included only live-bearing poeciliids) generally have lower metabolic rates that do other fishes. Based on available information Winberg’s conclusion was borne out that live-bearing freshwater poeciliids show lower than average routine metabolic rates compared to other freshwater fish groups. This is also true of poeciliids from saline waters, and of both freshwater and saline-water members of the related families Fundulidae and Cyprinodontidae. However, considerable variation in metabolic patterns was noted within and among these three families. There were geographic variations between subspecies of some species. Some island groups/species showed lower routine metabolic rates than did allied mainland groups/species. Thermal responses (Q₁₀ values) in routine metabolic rates of these fishes showed variations with geographic location, P_O2, salinity and size. Values of P_O2crit were altered among species by temperature, body size/age, and possibly salinity. Influences of ambient salinity on routine metabolic rates of these cyprinodontoid fishes also showed variations with temperature and size/age of individuals. The patterns of metabolic responses in these cyprinodontoid fishes to environmental conditions were generally similar to those of other species. Unfortunately, the available information on these fishes lacks the uniformity that would allow for critical and quantitative comparisons between and among the cyprinodontoids and with other species.     

Effect of body size, temperature, and salinity on the routine metabolism of larval and juvenile spotted seatrout

Routine oxygen consumption rates of young spotted seatrout Cynoscion nebulosus (Sciaenidae) were measured over a range of temperatures (24, 28, 30 and 32° C) and salinities (5, 10, 20, 35 and 45). Larvae and juveniles, 4·1–39·5 mm standard length ( L _S), ranging several orders of magnitude in dry body mass were used to estimate the mass–metabolism relationship. Oxygen consumption (μl O₂ larva⁻¹ h⁻¹) scaled isometrically with body mass for larvae <5·8 mm L _S(phase I, slope = 1·04) and allometrically thereafter (phase II, slope = 0·78). The inflection in the mass–metabolism relationship coincided with the formation of the hypural plate and an increase in the relative tail size of larvae. Salinity did not have a significant effect on routine metabolism during phase I. Temperature and salinity significantly affected routine metabolism during phase II of the mass–metabolism relationship. The effect of salinity was temperature dependent, and was significant only at 30° C. Response surfaces describing the environmental influences on routine metabolism were developed to provide a bioenergetic basis for modelling environmental constraints on growth.     

Effect of salinity and temperature on the growth of yearling Arctic cisco (Coregonus autumnalis) of the Alaskan Beaufort Sea

The growth of 1-year-old Arctic cisco ( Coregonus autumnalis ) was monitored under laboratory conditions for fish acclimated to one of two temperatures (5 and 10° C) and one of five salinities (6, 12, 18,24, 30‰). Fish were maintained for 43 days at rations of 3% wet body weight per day at 5° C and 5% wet body weight per day at 10° C, with rations adjusted for weight gain every 7–12 days. Fish increased 9–11% in length and 55–71% in weight at 5° C, and 23–27% in length and 141–161% in weight at 10° C. Length and weight increased linearly over 43 days. There was a statistically significant effect of temperature on growth but no statistically significant effect of salinity. Higher growth rates at 10° C were partially attributable to significantly greater gross conversion efficiency at the higher temperature. Over the course of the experiment, the condition (weight per unit length) of all fish increased by 3·2 to 63·6% at 5° C and by 5·6 to 46·0% at 10° C. There was no discernible effect of salinity on condition at either temperature. These results demonstrate that, with salinity acclimation and high food ration, 1-year-old Arctic cisco can grow at equivalent rates across salinities ranging from 6 to 30‰. The ecological implications of the results are discussed.     

Tolerance, behaviour and oxygen consumption in the sand goby, Pomatoschistus minutus (Pallas), exposed to hypoxia

Behavioural and metabolic reactions of Pomatoschistus minutus (Pallas) exposed to various degrees of hypoxia were studied. At 15°C and 20‰ mortality was 50% at 15.2% oxygen saturation. Avoidance and oxygen saturation showed a linear inverse relationship. At levels lower than 60% saturation increased activity occurred; avoidance was significant at 30% saturation. Active, routine and standard MO₂ correlated linearly with weight at 6 and 15°C (salinity = 19‰). During hypoxia at 15°C routine MO₂ rose significantly at 60–50% and 40–30% saturation expressed either as MO₂ during longer periods at night or MO₂ at shorter intervals during the day. Standard MO₂ was unaffected by hypoxia at 15°C. Haemoglobin concentration was significantly increased when P. minutus was acclimatized to 35% saturation.     

Temperature- and salinity-dependent development of a Nordic strain of Ichthyophthirius multifiliis from rainbow trout

During the twentieth century evidence was presented which suggested the presence of various strains and races of the parasite Ichthyophthirius multifiliis Fouquet. However, ecological profiles of various parasite isolates from different climatic zones are sparse. Such stringent characterizations of parasite development at defined abiotic conditions could provide valuable criteria for the different races; profile comparison from various localities is one way to differentiate these strains. Baseline investigations were therefore performed on the associations between abiotic factors (temperature/salinity) and the development of theronts in tomocysts of I. multifiliis isolated from rainbow trout in a Danish trout farm. It was shown that tomocyst formation and theront development took place between 5 and 30°C. Development rates and sizes of theronts were clearly affected by temperature: theronts escaped tomocysts already after 16–27 h at 25°C and 30°C, whereas this process took 8–9 days at 5°C. Likewise, theront size decreased steadily from a maximum of 57.4 × 28.6 μm at 5°C to 28.6 × 20.0 μm at 30°C. This size variation was only partly associated with the number of theronts that appeared at different temperatures. The lowest number of theronts escaping from one tomocyst was indeed found at 5–7°C (mean 329–413). At 11.6, 17.0 and 21°C, the highest number of theronts appeared (mean 546–642). However, at 25 and 30°C, the number decreased (458 and 424, respectively). Additional studies on the salinity dependent development of the parasite (at 11.6°C) showed that salinities above 5 p.p.t. totally inhibited development. Even at 5 p.p.t. the developmental time significantly increased and the number of theronts produced from one tomocyst decreased.     

Changes in body composition and morphology of young-of-the-year gulf menhaden, Brevoortia patronus Goode, in Fourleague Bay, Louisiana

Body composition (lipid, water, protein, energy content) and metamorphosis of young-of-the-year gulf menhaden, Brevoortia patronus Goode, were examined over a yearly cycle in Fourleague Bay, Louisiana. Metamorphosis from larvae to juveniles, as indicated by the body depth to length ratio, was completed by 30 mm S.L. Analysis of the length/weight relationship indicated separate equations for larvae/postlarvae (< 30 mm S.L.) and juvenile/subadults (30–100 mm S.L.). Major body composition changes from larvae to subadult included an increase in lipid content, a corresponding increase in energy content, and a decrease in nitrogen content. Young-of-the-year gulf menhaden did not exhibit the seasonal pattern of condition factors typical of adult clupeids. There may be a shift in energy allocation away from protein growth to lipid storage associated with attainment of a larger size. Initiation of emigration may be related to lipid storage and temperature change, with higher lipid content fish migrating first. End-of-year variations in fish size and lipid storage may be related to environmental conditions, such as water temperature and salinity.     

The potential impact of dryland salinity on the threatened flora and fauna of New South Wales

Summary We used digital map overlays in a geographical information system (GIS) to quantify the potential impact of dryland salinity on the threatened flora and fauna of New South Wales (NSW). Geographical areas of conservation priority were identified based on richness of threatened species with distribution records overlapping dryland salinity. Two alternative schemes – Interim Biogeographical Regionalization for Australia (regions) and catchment boundaries (catchments) – were used to subdivide NSW. Sydney Basin, North Coast and South-western Slopes regions – and Hunter, Sydney, Macquarie, Murrumbidgee and Lachlan catchments – were identified as priority areas with more than 10 salinity-overlap species present. Five threatened plant species were identified as priority species due to more than half of their known distributions overlapping areas of dryland salinity. Threatened animal species of most concern had 10–50% of their records overlapping areas of dryland salinity. Our findings demonstrate that landscape exposure to dryland salinity should be used in conjunction with total richness of threatened species for prioritizing conservation of geographical areas with respect to the potential impact of dryland salinity on threatened species.     

Effects of temperature, salinity, irradiance and diurnal periodicity on growth and photosynthesis in the diatom Nitzschia americana: light-limited growth

The effects of variations in temperature (10, 15, 20, 25, 30C)and salinity (8, 15, 20, 26, 32 p.p.t.) on cell size and ratesof photosynthesis and population growth were evaluated in axenic,light-limited (30 µE m^–2 s^–1) cultures ofan estuarine clone of the diatom ^{Nitzschia americana}. Experimentalconditions were chosen to reflect the range of natural conditionswhich occur in the clone's native environment, the Cape FearRiver Estuary, Nqrth Carolina. Rates of light-limited grossphotosynthesis; or photosynthetic efficiency (PSE), were determinedfrom short-term (1 h) ¹⁴C incubations. Diurnal variation inPSE was analyzed using ¹⁴C samples taken during times of estimatedmaximum and minimum rates of diurnal photosynthesis. The salinity-dependenttemperature response of PSE is characterized by a gradual increasein rates up to a temperature optimum at –25C, beyondwhich rates rapidly decline to zero at an upper lethal limit(30–40C). A similar pattern was observed in populationgrowth rates as a function of salinity and temperature. Independentof temperature, optimum salinity for growth was 26 p.p.t. Amaximum growth rate of 2.4 div d^–1 was measured at 25Cand 26 p.p.t. The effect of non-optimum salinity is a reductionin growth rates relative to a predicted temperature-dependentmaximum. Salinity-dependent patterns of variation in cell volume,in general, mirrored the response of population growth suchthat cultures with relatively high growth rates were dominatedby small cells. Significant diurnal variation was observed inPSE; maximum diurnal rates were generally 1.5–3.5 timesgreater than minimum diurnal rates.     

Metabolic response of juvenile gray snapper (Lutjanus griseus) to temperature and salinity: Physiological cost of different environments

Juvenile gray snapper (Lutjanus griseus) occupy a wide range of estuarine and nearshore habitats that differ in physico-chemical properties. To quantify the energetic cost of inhabiting these different habitats, routine metabolism of individual gray snapper was measured in the laboratory at 20 combinations of temperature (18, 23, 28, and 33 °C) and salinity (5, 15, 25, 35, and 45 psu). An open, flow-through respirometer was used, enabling trials to be run for long periods (∼16 h), while maintaining water quality (dissolved O₂>70% saturation), and providing fish sufficient time to habituate to the chambers undisturbed. Video recordings of fish in the respirometer chambers were analyzed to quantify the spontaneous activity rate of individuals. Analysis of covariance, using fish weight and mean activity rate as covariates, indicated significant temperature and salinity effects on oxygen consumption. Oxygen consumption was significantly higher at high salinities, and the salinity effect was temperature dependent. A polynomial equation describing oxygen consumption as a function of temperature and salinity indicated the increase due to salinity from 5 to 45 psu at high temperatures (30-33 °C) was equivalent to a 3 °C increase in temperature. At intermediate temperatures (24-26 °C), the increase due to salinity from 5 to 45 psu was less dramatic, equivalent to a 2 °C increase in temperature. At the lowest temperatures (18 °C), salinity did not have a significant effect on oxygen consumption. The increased metabolic costs in high salinities (∼7% at the high temperature) represent a significant energy cost for juveniles, that would need to be balanced by lower predation risk or greater food availability to result in similar juvenile production compared to lower salinity environments.     

Inosine Mediates the Protective Effect of Adenosine in Rat Astrocyte Cultures Subjected to Combined Glucose-Oxygen Deprivation

Abstract: Preliminary evidence suggests adenosine, a neuromodulator, has neuroprotective properties during cerebral ischemia. It is unclear, however, if adenosine has glioprotective effects. We studied the effect of adenosine on cellular injury in astroglial cultures subjected to combined glucose-oxygen deprivation. Adenosine (100–1,000 µ M ) dramatically reduced astroglial injury, whereas the adenosine agonists 2-chloroadenosine (10 n M –100 µ M ), N ⁶-cyclopentyladenosine (1 n M –10 µ M ), 5'- N -ethylcarboxamidoadenosine (10 n M –100 µ M ), and N ⁶-2-(4-aminophenyl)ethyladenosine (10 n M –100 µ M ) had no effect. Furthermore, the adenosine antagonists 8-cyclopentyl-1,3-dipropylxanthine (1 n M –1 µ M ), xanthine amine congener (10 n M –10 µ M ), and 8-( p -sulfophenyl)-theophylline (10–300 µ M ) failed to reverse the protective effect of 200 µ M adenosine. Next, adenosine degradation products were studied. Inosine proved to be glioprotective at concentrations nearly identical to those of adenosine, but hypoxanthine and ribose had no effect. The protective effect of 200 µ M inosine was not reversed by 8-( p -sulfophenyl)theophylline (10–300 µ M ). Adenosine deaminase (1 unit/ml) had no effect on protection produced by adenosine, whereas erythro -9-(2-hydroxy-3-nonyl)adenine hydrochloride (10 µ M ) reversed the protective effect of adenosine. Dipyridamole (4 µ M ) inhibited the protective effect of both adenosine and inosine. We conclude that adenosine dramatically decreases astroglial injury during combined glucose-oxygen deprivation and that this protective effect appears to be mediated by inosine.     

Effect of salinity and ration size on macrophage phagocytosis in juvenile black sea bream (Mylio macrocephalus)

The effects of salinity adaptation and ration size on macrophage phagocytosis were assessed in black sea bream ( Mylio macrocephalus ) juveniles. Salinity had no effect on phagocytosis in fish that were fed a 10% ration size. Reducing ration size from 10 to 5% resulted in a significant reduction in splenic and pronephric macrophage phagocytosis of fish adapted to hyper-(33 p.p.t.) and hypo-osmotic (6 p.p.t.) salinities. The fish that were adapted to an iso-osmotic salinity (12 p.p.t.) and fed a 5% ration size were able to maintain macrophage phagocytic activity at levels comparable to those of fish that were fed a 10% ration size. It is proposed that the adaptation of sea bream to an iso-osmotic medium is beneficial in that it stimulates the immune response through activation of macrophage phagocytosis.     

Plasma osmolality and oxygen consumption of perch Perca fluviatilis in response to different salinities and temperatures

The present study determined the blood plasma osmolality and oxygen consumption of the perch Perca fluviatilis at different salinities (0, 10 and 15) and temperatures (5, 10 and 20° C). Blood plasma osmolality increased with salinity at all temperatures. Standard metabolic rate (SMR) increased with salinity at 10 and 20° C. Maximum metabolic rate (MMR) and aerobic scope was lowest at salinity of 15 at 5° C, yet at 20° C, they were lowest at a salinity of 0. A cost of osmoregulation (SMR at a salinity of 0 and 15 compared with SMR at a salinity of 10) could only be detected at a salinity of 15 at 20° C, where it was 28%. The results show that P. fluviatilis have capacity to osmoregulate in hyper‐osmotic environments. This contradicts previous studies and indicates intraspecific variability in osmoregulatory capabilities among P. fluviatilis populations or habitat origins. An apparent cost of osmoregulation (28%) at a salinity of 15 at 20° C indicates that the cost of osmoregulation in P. fluviatilis increases with temperature under hyperosmotic conditions and a power analysis showed that the cost of osmoregulation could be lower than 12·5% under other environmental conditions. The effect of salinity on MMR is possibly due to a reduction in gill permeability, initiated to reduce osmotic stress. An interaction between salinity and temperature on aerobic scope shows that high salinity habitats are energetically beneficial during warm periods (summer), whereas low salinity habitats are energetically beneficial during cold periods (winter). It is suggested, therefore, that the seasonal migrations of P. fluviatilis between brackish and fresh water is to select an environment that is optimal for metabolism and aerobic scope.     

The influence of salinity on oxygen consumption and plasma electrolytes in grass carp, Ctenopharyngodon idella Val.

Fingerling grass carp, Ctenopharyngodon idella , 90–160 mm t.l. , were acclimated to experimental salinities of < 1 (fresh water), 91, 195 and 317 mOsm/kg. Oxygen consumption rates of fish declined, as salinity increased, from 0.16 mg O₂/g-h in fresh water to 0.11 mg O₂/g-h at an ambient concentration of 317 mOsm/kg. Plasma electrolytes (Na⁺ and Cl⁻¹) and total plasma ionic concentrations increased slightly following 10 days of exposure to ambient salinities greater than 195 mOsm/kg. At 317 mOsm/kg fish appeared to lose control of plasma electrolyte concentrations. As the osmotic gradient was reduced between the fish and the external medium it might have become advantageous to the maintenance of the osmotic equilibrium to reduce blood circulation to the gills, thus imposing a reduction in metabolic rate.     

Development time and survival of Verrallina funerea (Theobald) (Diptera: Culicidae) immatures and other brackish water mosquito species in southeast Queensland, Australia

Abstract  Verrallina funerea (Theobald) is a brackish water mosquito that is recognised as an important pest and vector in southeast Queensland, Australia. Immature development time and survival of Ve. funerea was defined in the laboratory in response to a range of temperatures (17–34°C) and salinities (0–35 parts per thousand (p.p.t)). The expression of autogeny in this species was also assessed. Salinity only had a slight effect on mean development time from hatching to adult emergence (7.0–7.4 d at salinities of 0, 17.5 and 31.5 p.p.t) and survival was uniformly high (97.5–99.0%). Mean development times were shorter at 26, 29 and 32°C (7.0, 6.8 and 6.8 d, respectively) and longest at 17°C (12.2 d). The threshold temperature ( t ) was 5.8°C and the thermal constant ( K ) was 142.9 degree-days above t . Survival to adulthood decreased from >95% (at 17–29°C) to 78% (at 32°C) and 0% (at 34°C). No expression of autogeny was observed. Immature development times of Ve. funerea , Ochlerotatus vigilax (Skuse) and Oc. procax (Skuse) were then determined under field conditions at Maroochy Shire. Following tide and rain inundation, cohorts of newly hatched larvae were monitored daily by dipping, and time until pupation was noted. Tidal inundation triggered hatching of Ve. funerea and Oc. vigilax larvae whereas Oc. procax larvae were found only after rain inundation. Estimates of Ve. funerea and Oc. vigilax field development times were similar (8–9 d) while Oc. procax development time was slightly longer (9–10 d). Based on these survey results, control activities targeting Ve. funerea must be initiated 4 d (if using Bacillus thuringiensis var. israelensis de Barjac) or 5 d (if using s -methoprene) after inundation. However, Casuarina glauca Sieber canopy and branchlets covering breeding habitats may present a problem for the penetration of such treatments.     

基于Landsat系列数据的盐分指数和植被指数对土壤盐度变异性的响应分析——以新疆天山南北典型绿洲为例

基于不同地理区域,借助目前已有或者构建新的盐分和植被指数定量评估研究区的土壤盐度状况。但多数指数并未在盐渍化较为严重的中国新疆地区进行系统性对比分析。因此,以新疆阜北地区(采样数=37),玛纳斯河绿洲(采样数=68)和渭干河-库车河绿洲(采样数=38)为研究区,以灌区农田和盐渍地采样数据和Landsat TM/ETM+/OLI为数据源,利用线性模型和多个非线性模型(10个)测试上述指数(14个指数)和原始波段对于研究区土壤盐度的敏感性。结果显示,阜北地区基于遥感获取的扩展的增强型植被指数Extented Enhanced Vegetation Index(EEVI)在全样本和部分样本(盐渍化样本,土壤盐度0.3%)两种模式下(0—10cm),较其他指数和波段而言较为敏感。在全样本和部分样本(土壤饱和溶液电导率2ds/m)两种模式下,与玛纳斯流域各层土壤盐度最为敏感的为band 2,部分样本模式下土壤盐度变异性显著性探测最大下探深度为30cm。渭干河-库车河绿洲全样本模式下,最大土壤盐度变异性显著性探测深度为40cm,0—10cm和10—20cm深度表现最为敏感的是土壤盐分指数SI-T,20—40cm深度则为植被指数TGDVI。部分样本下(土壤饱和溶液电导率2ds/m),0—10cm深度最为敏感的为band5,10—20cm深度最为敏感的为TGDVI,20—40cm深度则为EEVI。其他指数因地理环境的差异性(气候,土壤盐分类型,土壤类型,采样时间),与土壤盐度之间并未达到显著性(sig=0.05或者0.01)的水平。以上结果只是初步结论,但也暗示其中的某些指数在本区具有一定土壤盐度的识别潜力。此外,由于土壤本身的复杂性,需要采集更多的样本以深入分析不同盐度等级下上述指数的具体表现。     

Tolerance of Pomacanthus imperator to hypoosmotic salinities: changes in body composition and hepatic enzyme activities

Emperor angel fish Pomacanthus imperator were acclimated to various salinities (33, 22, 15, 10 and 7%) for 1 month and changes in serum chemistry, body composition and liver enzyme activities were monitored. No mortality was observed in fish adapted throughout the salinity range of 7–33% and the limit of survival was around 5%. Serum Na^+; and Cl ^– exhibited a stepwise decrease as the salinity was reduced from 33–7% but no concomitant tissue hydration could be observed. Branchial Na-K-ATPase activity was generally higher in hypoosmotic (7–15%) than in hyperosmotic salinities (22–33%o). Serum concentrations of glucose, lipid, α-amino acids and protein as well as the haematocrit value were all elevated in the salinity range of 15–22%. Serum cortisol was markedly lower but serum thyroxine was significantly elevated at 15–22%. Fish adapted to 15–22% had higher hepatosomatic indices, liver glycogen and muscle lipid contents and hepatic glucose-6-phosphate dehydrogenase activity. These data indicate that Pomacanthus imperator is a' physiologically euryhaline' species and metabolism in isoosmotic salinities has been fundamentally re-organized to favour carbohydrate and lipid retention.     

Effects of salinity and temperature on oxygen consumption in a freshwater population of Palaemonetes antennarius (Crustacea,decapoda)

• 1.1. After step-like increases in salinity the shrimps exhibit the smallest increase in oxygen consumption in the lower salinity range. At higher salinities the shrimps show longer recovery times and greater increases in the metabolic rate after salinity shock.
• 2.2. In steady-state experiments, the shrimps display the lowest oxygen consumption rates near the isosmotic point. The lowest metabolic rates occur at salinities of 3‰ and 10‰ At salinities of 20‰ and above the rate of metabolism increases by 20–30%.
• 3.3. The calculated osmoregulatory work for animals in fresh water amounts to only 2.7% of routine metabolism and drops to 1.1% for shrimps in 3‰ and 0.7% in 5‰ salinity.
• 4.4. Locomotory activity in the form of position change was not responsible for the increased oxygen consumption of the animals after salinity shocks. A “tentative swimming activity” by fast and frequent beating of the pleopods without position change may be an important factor in the increase of metabolic rates.
• 5.5. In its temperature response, the brackish water population has a higher metabolic rate than the freshwater one. Between 5 and 35°C Q ₁₀-values range from 4.01 to 1.37.

     

Saline groundwater as an aquaculture medium: physiological studies on the red drum, Sciaenops ocellatus

Physiological responses of the euryhaline red drum, Sciaenops ocellatus, to chloride salt addition, low salinity, and high sulfate concentration were measured. Survival was increased by addition of calcium chloride (CaCl₂) or magnesium chloride (MgCl₂) to dilute artificial seawater (0.2 ppt salinity). Although survival and routine metabolic rates were greater in MgCl₂ treatments, growth and feed efficiency were greater in CaCl₂ treatments. Marginal metabolic scope increased when CaCl₂ or MgCl₂ were added to dilute artificial seawater. There was a strong positive linear relationship (p=0.0001, r=0.91) between fish survival and salinity of artificial seawater dilutions over the salinity range 0.1 to 3.0 ppt. Monovalent ion concentrations in red drum plasma varied; whereas, divalent ion concentrations were relatively constant. Survival and growth were not affected by high sulfate concentrations (2000 mg l^-1) in 3.0 ppt artificial seawater supplemented with either sodium sulfate or magnesium sulfate. Routine metabolic rate and marginal metabolic scope of red drum exposed to high sulfate concentrations were slightly, but not significantly, lower than those of red drum in 3 ppt artificial seawater.