Effects of temperature and salinity on oxygen consumption of tawny puffer Takifugu flavidus juvenile

The respiratory rates of Tawny puffer Takifugu flavidus juvenile were measured at four temperatures (20, 23, 26 and 29 °C) and seven salinities (5, 10, 15, 20, 25, 30 and 35 g L^?1). The results showed that both temperature and salinity significantly affected the oxygen consumption of tawny puffer juvenile. The oxygen consumption rate (OCR) increased significantly with an increase in the temperature from 20 to 29 °C. Over the entire experimental temperature range (20–29 °C), the Q₁₀ value was 1.59, and the lowest Q₁₀ value was found between 23 and 26 °C. The optimal temperature for the juvenile lies between 23 °C and 26 °C. The OCR at 25 g L^?1 was the highest among all salinity treatments. The OCRs show a parabolic relationship with salinity (5–35 g L^?1). From the quadratic relationship, the highest OCR was predicted to occur at 23.56 g L^?1. The optimal salinity range for the juvenile is from 23 to 25 g L^?1. The results of this study are useful towards facilitating an increase in the production of the species juvenile culture.     

Effects of temperature on food consumption, growth and oxygen consumption of freshwater prawn Macrobrachium rosenbergii (de Man 1879) postlarvae

Effects of temperature on food consumption, growth and oxygen consumption were estimated for the freshwater prawn Macrobrachium rosenbergii postlarvae at 23 °C, 28 °C and 33 °C in the laboratory. The results showed that the animal's initial body weight had a close linear relationship with food consumption and growth. Food consumption increased directly with temperature. Consumption rates (C; mg day^?1 ind^?1 ) of the 28 °C and 33 °C groups were much higher than that of the 23 °C group (P < 0.001), and the 33 °C group's consumption rate was higher than that of the 28 °C group (P < 0.05). The relationship of food consumption with temperature and initial body weight (W; mg) could be described as: C = 0.0679W + 0.185t? 3.17. Growth increased significantly with increased temperature. The relationship among specific growth rate, temperature and initial body weight was as follows: SGR = ?0.110W + 0.213t + 0.176. However, temperature showed no effect on growth efficiency. Oxygen consumption increased significantly with temperature (P < 0.01). The weight‐specific oxygen consumption rates (mg O₂ g^?1 h^?1) at 23 °C, 28 °C and 33 °C were 0.83, 1.16 and 1.49 mg O₂ g^?1 h^?1 for 61.92 mg M. rosenbergii.     

Effect of temperature and salinity on virulence of Edwardsiella tarda to Japanese flounder, Paralichthys olivaceus (Temminck et Schlegel)

Experiments were designed to determine the effects of temperature and salinity on the virulence of Edwardsiella tarda to Japanese flounder, Paralichthys olivaceus. In the temperature experiment, a two‐factor design was conducted to evaluate the effects of both pathogen incubation temperature and fish cultivation temperature on pathogen virulence. E. tarda was incubated at 15, 20, 25 and 30±1°C, and the fish (mean weight: 10 g) were reared at 15, 20 and 25±1°C respectively. The fish reared at different temperatures were infected with the E. tarda incubated at different temperatures. The results of a 4‐day LD₅₀ test showed that temperature significantly affected the virulence of E. tarda (P<0.01) and the interaction between the two factors was also significant (P<0.01). For fish reared at 15°C the virulence of E. tarda was the highest at 25°C of pathogen incubation, followed by 20, 15 and 30°C. When the fish rearing temperature was raised to 20 and 25°C, the virulence of E. tarda incubated at all temperatures increased. Isolation testing demonstrated results similar to those of LD₅₀. The higher rearing temperature increased the proliferation rate of the pathogen in fish. In the salinity experiment, the incubation salinity of E. tarda was at 0, 10, 20 and 30 g L^?1, respectively, and the fish with mean weight of 50 g were cultured in natural seawater of 30 g L^?1. The results of one‐way anova in 4‐day LD₅₀ test showed that incubation salinity significantly affected virulence. Virulence was lower when the salinity of the incubation medium was at 0 and 30 g L^?1, higher at 10 and 20 g L^?1. The results of isolation test were in accordance with those of LD₅₀. At 20 g L^?1E. tarda had a faster proliferation rate than that at 10 g L^?1.     

Effects of temperature and salinity on oxygen consumption and ammonia excretion in different colour strains of the Manila clam,Ruditapes philippinarum

The metabolic responses of different colour strains of Ruditapes philippinarum in terms of oxygen consumption and ammonia excretion to changes in temperature (15–35°C) and salinity (20–40) were investigated. In our range of temperatures (15–35°C), oxygen consumption rate (OCR) increases in cultivated strains (White and Zebra) in opposition to the effect in the wild strain which reach a maximum at 25°C. The highest Q₁₀ coefficients were 2.741 for zebra strain, 4.326 for white strain, and 1.944 for wild at temperatures of 25–30, 30–35 and 20–25°C respectively. In our range of salinity (20–40°C), OCRs of white strain and zebra strain firstly decreased to lowest level at 25 and 30, and then increased to highest level at 35 and 40 respectively. When the salinity is beyond 35, the OCR decreased and the turning point was found in the white strain and wild, but the zebra strain OCR still increased to a highest level (1.906 mg g^?1 h^?1) at 40 (P < 0.05). These results show that the cultivated colour strains of R. philippinarum were different from wild in terms of metabolic responses, and information on its response to different temperature and salinity have implications in the aquaculture industry.     

Effects of temperature and salinity on the survival and development of mud crab, Scylla serrata (Forsskål), larvae

The combined effects of temperature and salinity on larval survival and development of the mud crab, Scylla serrata, were investigated in the laboratory. Newly hatched larvae were reared under 20 °C temperature and salinity combinations (i.e. combinations of four temperatures 25, 28, 31, 34 °C with five salinities 15, 20, 25, 30, 35 g L⁻¹). The results showed that temperature and salinity as well as the interaction of the two parameters significantly affected the survival of zoeal larvae. Salinity at 15 g L⁻¹ resulted in no larval survival to the first crab stage, suggesting that the lower salinity tolerance limit for mud crab larvae lies somewhere between salinity 15 and 20 g L⁻¹. However, within the salinity range of 20–35 g L⁻¹, no significant effects on survival of zoeal larvae were detected (P>0.05). The combined effects of temperature and salinity on larval survival were also evident as at low salinities, both high and low temperature led to mass mortality of newly hatched larvae (e.g. 34 °C/15 g L⁻¹, 34 °C/20 g L⁻¹ and 25 °C/15 g L⁻¹ combinations). In contrast, the low temperature and high salinity combination of 25 °C/35 g L⁻¹ resulted in one of the highest survival to the megalopal stage. It was also shown that at optimal 28 °C, larvae could withstand broader salinity conditions. Temperature, salinity and their interaction also significantly affected larval development. At 34 °C, the mean larval development time to megalopa under different salinity conditions ranged from 13.5 to 18.5 days. It increased to between 20.6 and 22.6 days at 25 °C. The effects of salinity on larval development were demonstrated by the fact that for all the temperatures tested, the fastest mean development to megalopa was always recorded at the salinity of 25 g L⁻¹. However, a different trend of salinity effects was shown for megalopae as their duration consistently increased with an increase in salinity from 20 to 35 g L⁻¹. In summary, S. serrata larvae tolerate a broad range of salinity and temperature conditions. Rearing temperature 25–30 °C and salinity 20–35 g L⁻¹ generally result in reasonable survival. However, from an aquaculture point of view, a higher temperature range of 28–30 °C and a salinity range of 20–30 g L⁻¹ are recommended as it shortens the culture cycle.     

Effect of salinity on survival, growth, oxygen consumption and ammonia-N excretion of juvenile whiteleg shrimp, Litopenaeus vannamei

In this study, we tested the lower salinity tolerance of juvenile shrimps (Litopenaeus vannamei) at a relatively low temperature (20 °C). In the first of two laboratory experiments, we first abruptly transferred shrimps (6.91 ± 0.05 g wet weight, mean ± SE) from the rearing salinity (35 000 mg L^?1) to salinities of 5000, 15 000, 25 000, 35 000 (control) and 40 000 mg L^?1 at 20 °C. The survival of L. vannamei juvenile was not affected by salinities from 15 000 to 40 000 mg L^?1 during the 96‐h exposure periods. Shrimps exposed to 5000 mg L^?1 were significantly affected by salinity, with a survival of 12.5% after 96 h. The 24‐, 48‐ and 96‐h lethal salinity for 50% (LS₅₀) were 7020, 8510 and 9540 mg L^?1 respectively. In the second experiment, shrimps (5.47 ± 0.09 g wet weight, mean ± SE) were acclimatized to the different salinity levels (5000, 15 000, 25 000, 35 000 and 40 000 mg L^?1) and then maintained for 30 days at 20 °C. Results showed that the survival was significantly lower at 5000 mg L^?1 than at other salinity levels, but the final wet weight under 5000 mg L^?1 treatment was significantly higher than those under other treatments (P<0.05). Feed intake (FI) of shrimp under 5000 mg L^?1 was significantly lower than those of shrimp under 150 00–40 000 mg L^?1; food conversion efficiency (FCE), however, showed a contrasting change (P<0.05). Furthermore, salinity significantly influenced the oxygen consumption rates, ammonia‐N excretion rates and the O/N ratio of test shrimps (P<0.05). The results obtained in our work provide evidence that L. vannamei juveniles have limited capacity to tolerate salinities <10 000 mg L^?1 at a relatively low temperature (20 °C). Results also show that L. vannamei juvenile can recover from the abrupt salinity change between 15 000 and 40 000 mg L^?1 within 24 h.     

Filtration and oxygen consumption rates on various growth stages of Scapharca broughtonii spat

To investigate the effects of temperature and salinity on filtration and oxygen consumption rate of Scapharca broughtonii spat with different growth stages. This study was conducted under six different water temperatures and five different salinity conditions. The spat were divided into three groups of different shell sizes and filtration rates were estimated by Neutral red. The results showed that in all of the three groups, the highest filtration rates appeared at 20 °C, and the highest one was 1.89±0.12 L g h^?1 in the group with the lowest shell length (11.8±2.1 mm). The filtration rates in every group increased with the rise of salinity in the range from 10 to 40 g L^?1, and the highest one is 2.62±0.21 L g h^?1 in the lowest shell length group. The trends of oxygen consumption rates were similar to filtration rates. The highest rates were 0.189±0.003 mg g h^?1 at 20 °C and 0.308±0.018 mg g h^?1 at a salinity of 40 g L^?1 in the group with the lowest shell length. And the results showed that the smaller the shell size, the higher the filtration and oxygen consumption rate.     

Effects of salinity and temperature during incubation on hatching and development of lingcod Ophiodon elongatus Girard, embryos

The interactive effects of salinity and temperature on development and hatching success of lingcod, Ophiodon elongatus Girard, were studied by incubating eggs at four temperatures (6, 9, 12 and 15°C) and five salinities (15, 20, 25, 30 and 35 g L^?1). Hatch did not occur in any of the 15°C treatments. Degree days (°C days) to first hatch was not influenced by temperature or salinity, however, calendar days to first hatch differed significantly for temperature (P<0.0001, 61±1, 44±1 and 35±1 days for 6, 9 and 12°C respectively). Degree days to 50% (427.1±4.2) hatch was not significantly influenced by temperature but was by salinity (P=0.0324). Viable hatch (live with no deformities, 74.1±4.0%) was greatest at 9°C and 25 g L^?1 but not significantly different in the range of 20–30 g L^?1. Larval length (9.4±0.13 mm) was greatest at 9°C and 20–30 g L^?1. Temperature and salinity significantly influenced all categories of deformities with treatments at the upper (12°C and 35 g L^?1) and lower limits (6°C and 15 g L^?1) producing the greatest deformities. The optimal temperature and salinity for incubating Puget Sound lingcod eggs was found to be 9°C and 20–30 g L^?1.     

Growth of juvenile common snook (Centropomus undecimalis Bloch, 1792) reared at different temperatures and salinities: Morphometric parameters,RNA/DNA,and protein/DNA ratios

We investigated the growth of juvenile common snook (Centropomus undecimalis) reared at 25°C and 28°C and salinities of 0.3, 15, and 32 g L^?1. Total length, weight, RNA/DNA, and protein/DNA ratios were determined after 90 days of experiment. Higher growth was observed at 28ºC compared with 25°C, at the same salinity. At 28°C and 15 g L^?1 salinity, the weight (25.14 g) of juveniles was twice that of the juveniles reared at the lower temperature. At different salinities, only higher temperature affected growth, with higher weight values obtained at 15 g L^?1 in comparison with 0.3 and 32 g L^?1. Length was similar at 0.3 and 15 g L^?1. The RNA/DNA ratio was greater in juveniles reared at a salinity of 15 g L^?1 when compared with 0.3 and 32 g L^?1. This study shows that the combination of higher temperature and intermediate salinity promotes better growth of common snook juveniles.     

Temperature preference and oxygen consumption of the largemouth bass Micropterus salmoides (Lacépède) acclimated to different temperatures

The behavioural and metabolic responses of the largemouth bass Micropterus salmoides (Lacépède) to temperature were determined to define optimal thermal conditions. The final preferendum of largemouth bass juveniles determined with acute and gravitation methods was independent of the method (29.0–28.1 °C). The displacement velocity in the horizontal thermal gradient of bass juveniles was 22.4 cm h⁻¹ in the light phase and 22.6 cm h⁻¹ in the dark phase. Oxygen consumption rates in the largemouth bass increased significantly (P<0.05) from 48.8 to 69.4 mg O₂ Kg⁻¹ h⁻¹ with an increase in the acclimation temperature from 20 to 33 °C. The temperature quotient (Q₁₀) in the juveniles was 1.37–2.00 in the range of acclimation temperatures of 26–29 and 29–32 °C. The optimum temperature range for growth calculated using Jobling's equation was 28.1–28.6 °C and for Q₁₀ values 26–29 °C. The results are discussed in relation to the use of this information in aquaculture.     

Standard oxygen consumption of seasonally acclimatized cownose rays, Rhinoptera bonasus (Mitchill 1815), in the northern Gulf of Mexico

Standard oxygen consumption rate (MO₂) was determined for 19 cownose rays (Rhinoptera bonasus) using flow-through respirometry. Rays ranged in size from 0.4 to 8.25 kg (350–790 mm DW). Respirometry experiments were conducted on seasonally acclimatized rays at temperatures from 19.0 to 28.8 °C. Estimates of mass-dependent MO₂ ranged from 55.88 mg O₂ kg⁻¹ h⁻¹ for an 8.25 kg ray to 332.75 mg O₂ kg⁻¹ h⁻¹ for a 2.2 kg animal at 22–25°C. Multiple regression analysis examining the effect of temperature, salinity, and mass on standard mass-independent MO₂ found temperature (P < 0.01), and mass (P < 0.0001) to have a significant effect on oxygen consumption, whereas salinity did not (P > 0.05). Q ₁₀ was calculated as 2.33 (19–28 °C), falling between the estimates determined for two other batoid species, the bull ray (Myliobatos aquila; Q ₁₀ = 1.87) and the bat ray (Myliobatis californica; Q ₁₀ = 3.00). The difference in the Q ₁₀ estimates may be attributed to the use of seasonally acclimatized as opposed to laboratory-acclimated animals.     

The effect of temperature on the resting and post-exercise metabolic rates and aerobic metabolic scope in shortnose sturgeon <Emphasis Type="Italic">Acipenser brevirostrum</Emphasis>

The effects of acclimation temperature (15, 20, 25 °C) on routine oxygen consumption and post-exercise maximal oxygen consumption rates (MO₂) were measured in juvenile shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818). The routine MO₂ of shortnose sturgeon increased significantly from 126.75 mg O₂ h^?1 kg^?1 at 15 °C to 253.13 mg O₂ h^?1 kg^?1 at 25 °C. The temperature coefficient (Q ₁₀) values of the routine metabolic rates ranged between 1.61 and 2.46, with the largest Q ₁₀ values occurring between 15 and 20 °C. The average post-exercise MO₂ of all temperature groups increased to a peak value immediately following the exercise, with levels increasing about 2-fold among all temperature groups. The Q ₁₀ values for post-exercise MO₂ ranged from 1.21 to 2.12, with the highest difference occurring between 15 and 20 °C. Post-exercise MO₂ values of shortnose sturgeon in different temperature groups all decreased exponentially and statistically returned to pre-exercise (resting) levels by 30 min at 15 and 20 °C and by 60 min at 25 °C. The aerobic metabolic scope (post-exercise maximal MO₂-routine MO₂) increased to a maximum value ～156 mg O₂ h^?1 kg^?1 at intermediate experimental temperatures (i.e., 20 °C) and then decreased as the temperature increased to 25 °C. However, this trend was not significant. The results suggest that juvenile shortnose sturgeon show flexibility in their ability to adapt to various temperature environments and in their responses to exhaustive exercise.     

Inter‐ and intra‐individual variability in growth and food consumption in pikeperch,Sander lucioperca L., larvae revealed by individual rearing

We examined short‐term, inter‐ and intra‐individual variability in rates of growth and food consumption in fish early life stages to gain a mechanistic understanding of why larvae in the same environments often grow at vastly different rates. We made parallel measurements of growth rate in standard length (GR_SL) and food consumption rate (C), and provide estimates of weight growth rate (GR_DW) and gross growth efficiency (GGE = 100*GR_DW/C) of individually reared larvae of pikeperch, Sander lucioperca L., fed Artemia nauplii at 20°C and a salinity of 2.0 g L^?1. Within two trials, GR_SL, C and GGE were obtained for 108 larvae over a maximum period of 28 days. Mean (±SD) initial size, GR_SL, C and GGE were 19.49 (9.19) mm, 0.68 (0.21) mm day^?1, 0.85 (0.44) mg day^?1 and 36.5 (10.2)% respectively. The vast majority (91%) of the variability in growth was explained by differences in food consumption. When isolated from conspecifics for 28 days, relatively small larvae grew faster than relatively large ones, partially mitigating initial differences in size‐at‐age.     

Effects of changes in environmental factors on the non-specific immune response of Nile tilapia, Oreochromis niloticus L.

Lysozyme acts as a non‐specific defence substance and is found in the peripheral blood, cutaneous mucus and certain tissues of marine and freshwater fishes. In the present study, we examined the effect of various environmental factors (water temperature, salinity, pH and suspended sediments) on plasma lysozyme activity in the Nile tilapia, Oreochromis niloticus L. When the fish were reared at different water temperatures (18.4, 23, 28 and 33°C), plasma lysozyme activity increased at 28°C after 2 and 4 weeks. A significant decrease in lysozyme activity was found in the fish reared at 33°C for 4 weeks. These results suggest that there is a water temperature range that affects the amount of plasma lysozyme activity that can be detected. Fish cultured at 24 g L^?1 of salinity for 2 and 4 weeks and 12 g L^?1 for 4 weeks resulted in significantly increased plasma lysozyme activity, suggesting that environmental salinity also affects the amount of plasma lysozyme that can be detected. Lysozyme activity also significantly increased when the fish were held in acidic water at pH 4.0 and in suspended sediments at 2000 mg L^?1 for 2 weeks. It was concluded that changes in some aquatic environmental factors affect the non‐specific immune responses of Nile tilapia.     

Physiological responses of largemouth bass to acute temperature and oxygen stressors

Abstract Temperature and oxygen gradients exist in nearly every water body, but anthropogenic activities can subject fish to rapid changes in these important environmental variables. These rapid changes in temperature and oxygen (generally referred to as temperature or oxygen shock) may have sub‐lethal consequences depending upon the magnitude and the fish species. This study quantified physiological changes in largemouth bass, Micropterus salmoides (Lacepède), exposed to two levels of heat and cold shocks and to two levels of hypoxic and hyperoxic shocks. Following a cold shock from 20 °C to 8 °C, plasma cortisol and glucose increased after 1 h and lactate dehydrogenase activity increased after 6 h. Plasma glucose and K⁺ concentrations increased 1 h after a heat shock from 20 °C to 32 °C but not after 6 h. Bass subjected to a hypoxic shock from 8 to 2 mg O₂ L^?1 showed decreased plasma K⁺ and increased plasma glucose and white muscle lactate. No changes in physiological parameters were observed in bass subjected up to 18 mg O₂ L^?1 hyperoxia. Results from this study suggest that largemouth bass can tolerate a wide range of temperature and oxygen shocks, but temperature decreases of 20 to 8 °C and hypoxia as low as 4 mg O₂ L^?1 should be avoided to minimise physiological perturbations.     

Effects of temperature,salinity and body size on the physiological responses of the Iwagaki oyster Crassostrea nippona

The physiological responses of the juvenile Crassostrea nippona in terms of filtration, oxygen consumption and ammonia excretion to changes in temperature (16–32°C), salinity (15–35 psu) and body size (small, medium and large) were investigated. In this study, the values of filtration rate (FR), oxygen consumption rate (OCR) and ammonia excretion rate (AER) increased with temperature rising from 16°C to 24°C, reaching the highest values at 24°C and 28°C; with any further increase in temperature above this limit, these values decrease drastically (p < .05). The highest Q₁₀ coefficients were 2.75 for large, 3.54 for medium at 16–20 and 3.47 for small size at 20–24°C respectively. Moreover, the responses of FR and OCR were found to be influenced significantly by salinity, tending to increase concomitantly with salinity up to 25–30 psu, though the values of these parameters were diminished dramatically (p < .05) above this level, showing a reverse pattern from that observed in AER, which firstly decreased to the lowest level at 25 and 30 psu, and then severely (p < .05) increased to the highest level at 35 psu. In addition, the low O:N ratios of all sizes of C. nippona at 16°C and 30–35 psu were indicative of a protein‐dominated catabolism, whereas the O:N ratios of large size at 20–32°C and all sizes at 20–30 psu, indicating that the metabolic energy from protein diminished and lipid and carbohydrate were used as the energy substrates. Physiological rates of C. nippona were well correlated with its size. The average values of mass exponents (b‐values) estimated in the present study were 0.657 for OCR and 0.776 for AER at different temperatures, and 0.647 for OCR and 0.767 for AER at varying salinities, signifying that physiological process of C. nippona becomes relatively slower with increasing body size regardless of temperature or salinity. Finally, our results confirm that the optimal temperature and salinity for juvenile C. nippona lie within 24–28°C and 25–30 psu respectively. The results of physiological traits in response to environmental factors of this species are informative in site selection for the cultivation.     

Feeding,egg production and laboratory culture of Schmackeria poplesia Shen (Copepoda: Calanoida)

Copepods are candidates with great potential as live prey for rearing fish larvae and juveniles in aquaculture; however, the techniques for a large‐scale culture of copepods are yet to be developed. In this study, we examined the effects of water temperature, salinity, prey concentration and algal species on the grazing and egg production rates of a calanoid copepod Schmackeria poplesia (Copepoda: Calanoida). The results showed that the grazing rate of S. poplesia was the highest when the copepods were cultured in seawater with temperature of 25 °C, salinity of 20 g L^?1, prey concentration at 10⁵ cells mL^?1 and supplied with Platymonas helgolandica as the prey. The egg production rates, however, was the highest when copepods were fed with a mixed prey of Isochrysis galbana and Phaeodactylum tricornutum (cell ratio 1:1, prey concentration 10⁵ cells mL^?1) at 25 °C, 20 g L^?1 of salinity. A 100 L cultural system was established to culture S. poplesia under the condition optimized for egg production. The total number of copepods increased 40–43‐fold with the production rates of 87–290 copepods L^?1 day^?1 in 14 days. This research was the first attempt for a large‐scale culture of S. poplesia and the technique established can be further applied in aquaculture.     

Incubation of European Squid (Loligo vulgaris Lamarck, 1798) eggs at different salinities

Loligo vulgaris is a commercially important squid throughout the Mediterranean region and is a candidate species in biomedical and aquaculture research. Some loligo species (L. opalescens, L. forbesi, Sepiteuthis lessoniana) have now been cultured through some successive generations in closed, recirculating seawater systems. The effects of salinity on hatching European Squid (L. vulgaris Lamarck, 1798) eggs were investigated during November 2004. The egg capsules were incubated directly in salinity of 32, 34, 36, 38, 40, 42 and 37 g L^?1 (control group) at 19.8°C (SD 1.2°C), and a photoperiodicity of 12 h light:12 h dark for 16–23 days before hatching. In all treatments, the eggs were developed and hatched normally after 16–22 days at 32 g L^?1, 17–22 days at 34, 18–21 days at 42 g L^?1, 18–22 days at 36 and 40 g L^?1, 19–22 days at 37 g L^?1 and 19–23 h at 38 g L^?1. In the experiments, the highest hatching rate and hatching success (HS) of the eggs were obtained at 38 g L^?1 (hatching rate: 100% (SD 0%) and HS: 96.7% (SD 3.5%)) and the lowest hatching rate at 42 g L^?1 (hatching rate: 3% (SD 6%) and HS: 0%). Dorsal mantle lengths (DML) of new hatchlings ranged from 2.08 to 2.80 mm. The present study showed that salinity affects the hatching rate and HS of eggs and first hatching time and DML of paralarvae in L. vulgaris. The squid eggs at stage 11 (I) can tolerate 5 g L^?1 reduction and 3 g L^?1 increase in salinity.     

Acute toxicity of ammonia in Pacu fish (Piaractus mesopotamicus,Holmberg, 1887) at different temperatures levels

Piaractus mesopotamicus juveniles (total length 12 ± 0.5 mm) were exposed to different concentrations of ammonia‐N (un‐ionized plus ionized ammonia as nitrogen), using the static renewal method at different temperature levels (15, 20 and 25°C) at pH 7. The 24, 48, 72, 96 h LC₅₀ values of ammonia‐N in P. mesopotamicus juveniles were 5.32, 4.19, 3.79 and 2.85 mg L^?1 at 15°C; 4.81, 3.97, 3.25 and 2.50 mg L^?1 at 20°C; and 4.16, 3.79, 2.58 and 1.97 mg L^?1 at 25°C respectively. The 24, 48, 72, 96 h LC₅₀ values of NH₃‐N (un‐ionized ammonia as nitrogen) were 0.018, 0.014, 0.013, 0.009 mg L^?1 at 15°C temperature; 0.023, 0.019, 0.016 and 0.012 mg L^?1 at 20°C; 0.029, 0.026, 0.018 and 0.014 mg L^?1 at 25°C. The temperature increase from 15 to 25°C caused an increase of ammonia‐N susceptibility by 21.80%, 9.55%, 31.92% and 30.87%, after 24, 48, 72 and 96 h exposure respectively. Furthermore, we found that exposure of fish to ammonia‐N caused an elevation in total haemoglobin and blood glucose with an increase of 2 mg L^?1 concentration. Ammonia levels tolerated, especially in different temperatures levels, have important implications for the management of aquaculture.     

The effect of temperature on the energy budget of the Manila clam, <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis>

In this study, the energy budget of the Manila clam, Ruditapes philippinarum, was evaluated after one-week acclimation periods at 5, 10, 15, 20, and 25°C. Small clams (151 ± 12 mg DW) and large clams (353 ± 16 mg DW) were fed with the microalgae, Isochrysis galbana. Filtration rate, ingestion rate, assimilation efficiency, oxygen-consumption rate, and ammonia excretion rate were measured. Both filtration rate and ingestion rate of small and large clams were found to be related to temperature. The highest Q ₁₀ values were measured in the range 15–20°C for both small and large clams. Assimilation efficiency of both small and large clams was not significantly influenced by temperature, although the maximum mean values were detected at 20°C. Oxygen consumption rate and ammonia excretion rate of small and large clams were found to be related directly to temperature over the entire range, with a maximum being detected at 25°C. The highest Q ₁₀ value was estimated in the range 10–15°C with regard to oxygen consumption rate, and in the range of 15–20°C with regard to ammonia excretion rate. Scope for growth (SFG) was positive at all temperatures, achieving a maximum value at 20°C in both small and large clams, primarily as a consequence of the enhanced ingestion rate which offset the concomitant elevation in the metabolic rate. In this study we have estimated the thermal optimum for this species at 20°C.