Temperature and salinity effects on the respiratory metabolism of the first zoeal stage of Macrobrachium holthuisi Genofre & Lobão (decapoda: Palaemonidae)

Oxygen consumption rates of stage I Macrobrachium holthuisi Genofre & Lobão zoeae were measured in 24 different temperature and salinity combinations using Cartesian diver microrespirometers. Metabolic rates varied little with salinity at 15°C while at 20°C a marked elevation occurred in 0 and 35‰ At 25°C, a slight elevation occurred in 0‰; rates remained constant, however, in the other salinities. At 30°C, respiratory rates were similar to those recorded at 25°C except for decreases at 0 and 28‰ salinity. Q₁₀ values in the different salinities were usually highest between 15 and 20°C. Statistical analyses showed that while both temperature, salinity and their interaction significantly influenced larval respiratory rates, temperature had the more pronouced effect. Larval metabolism is salinity independent over the salinity range encountered in the larval biotope (7–21‰) at temperatures of 15–30°C.     

Exposure of goldsinny, rock cook and corkwing wrasse to low temperature and low salinity: survival, blood physiology and seasonal variation

Wrasse used as cleaner fish with farmed Atlantic salmon Salmo salar can be subjected to large and rapid temperature and salinity fluctuations in late autumn and early winter, when summer-warmed surface water is affected by early snowmelt episodes. Because of their containment in sea cages, wrasse which are essentially acclimated to summer temperatures may be rapidly exposed to winter conditions. Short-term tolerance of low temperature and low salinity by three species of wrasse, goldsinny Ctenolabrus rupestris rock cook Centrolabrus exoletus corkwing Crenilabrus melops caught during the summer, and winter-caught corkwing, was investigated. A 3–day period at 30 or 32‰ salinity and temperature 8, 6 or 4° C (for summer-caught fish; 4° C only for winter-caught) was followed by a decline in salinity to 24, 16 or 8‰ over c. 36 h, followed by a further 24 h at these salinities held constant, at each of the three temperatures. Controls in 30 or 32‰ were maintained at 8, 6 or 4° C. Mortality of summer-caught corkwing and rock cook was high at 4° C, whereas the influence of salinity on mortality was small. Mortality of goldsinny was low or zero in all treatments. Surviving corkwing and rock cook after 3 days at 4° C and 32‰ salinity had elevated plasma osmolality: in summer-caught corkwing, plasma [Cl°] and [Na⁺] were high, whereas in rock cook only [Na⁺] was high. Haematocrit was low in summer-caught corkwing, high in rock cook. In survivors of all three species at the end of the experiment, values of all these parameters were comparable with those of fish at the beginning of the experiment, except that survivors at low salinity (8, 16‰) had low plasma osmolality, at all temperatures, and in surviving rock cook in these treatments haematocrit was high and plasma [Cl^?] was low. Winter-caught corkwing had higher osmolality, [Na⁺] and [Cl^?] than summer-caught corkwing; there was no difference in haematocrit. Survival of wintercaught corkwing exposed to four salinities at 4° C was much higher than that of summercaught corkwing under the same conditions. Little change in blood physiology was recorded for winter-caught corkwing, with only fish subjected to 8‰ and 4° C showing signs of osmoregulatory stress. The interspecific and seasonal differences in survival and blood physiology at low temperature and low salinity are discussed in relation to wrasse survival over winter, both in the field and in salmon farms.     

Effects of salinity and cyclic temperature on survival of two sympatric species of grass shrimp (Palaemonetes), and their relationship to natural distributions

Survival and respiration of the grass shrimp Palaemonetes pugio Holthuis and P. vulgaris (Say) from the Newport River estuary were measured after exposure to cyclic and constant winter temperatures, to rapid decreases in temperature, and to various temperature-salinity combinations. Both species were subjected to nine temperature-salinity combinations including temperature regimes of cyclic 7–13°C, constant 7° and 10°C, and salinities of 5, 20, and 35%.. Based on the laboratory and field results, the differences in physiological tolerance to winter temperatures and salinities were examined in relation to habitat partitioning by these sympatric species.Survival after continuous exposure to cyclic temperature regimes at medium to high salinities was similar to that observed for comparable constant temperatures; however, at low salinities mortality was significantly lower under the cyclic regime than under either constant regime. This suggests that cyclic temperatures may be detrimental in combination with some other stress. A rapid, transient decrease in temperature from either 7° or 10°C to 2°C had no measurable effect on survival or rate of oxygen consumption at any temperature-salinity acclimation. Neither salinity (except in areas intermittently subjected to salinities below 3 %.) nor winter temperatures appear to affect habitat partitioning in grass shrimp.     

Effects of salinity,pH, and temperature on the spores and sporelings ofDictyopteris australis,an alginophyte

Effects of changes in salinity, pH, and temperature on tetraspores and sporelings ofDictyopteris australis were investigated under laboratory conditions, The spores and sporelings showed a narrow range of tolerance to salinity (30.0‰ to 32.2‰). The spores did not germinate beyond this range. Growth of the sporelings was almost the same at salinities 30.6‰ and 32.2‰, but mortality was higher at 32.2‰. The alga showed a tolerance to pH from 7.5 to 8.4. However, growth of the viable sporelings was maximum at pH 8.2. The optimal temperature for survival and growth of the sporelings of the alga is 23°C. Temperatures above 28°C and below 18°C were found to be highly detrimental.     

The combined effects of temperature,salinity, and declining oxygen tension on oxygen consumption in the marine pulmonate Amphibola crenata (Gmelin, 1791)

Oxygen consumption of Amphibola crenata (Gmelin) was measured in various salinity-temperature combinations (< 0.1‰ to 41‰ salinity and 5 to 30°C) in air, and following exposure to declining oxygen tensions. In all experimental conditions, respiration varied with the 0.44 power of the body weight (sd = 0.14). The aquatic rate was consistently higher than the aerial rate of oxygen consumption, although at 30 °C the two rates were similar. Oxygen consumption increased with temperature up to 25 °C in all salinities; the lowest values were recorded at temperatures below 10 °C and at 30 °C in the most dilute medium. At all exposure temperatures, the oxygen consumption of Amphibola decreased regularly with salinity down to 0.1 ‰, and following exposure to concentrated sea water (41‰). Salinity had the least effect at 15 °C which was the acclimation temperature. In general, all of the temperature coefficients (Q₁₀ values) were low, < 1.65. However, Q₁₀ values above 2.8 were recorded at a salinity of 17.8‰ between 10 and 15 °C. Oxygen consumption of all size classes of Amphibola was more temperature dependent in air than in water and small individuals show a greater difference between their aerial and aquatic rates than larger snails. The rates of oxygen consumption in declining oxygen tensions were expressed as fractions of the rates in air saturated sea water at each experimental salinity-temperature combination. The quadratic coefficient B₂ becomes increasingly more negative with both decreasing salinity and temperatures up to 20 °C. At higher temperatures (25 and 30 °C) the response is reversed such that O₂ uptake in snails becomes increasingly independent of declining oxygen tensions at higher salinities. On exposure to a salinity of 4‰, Amphibola showed no systematic response to declining oxygen tension with respect to temperature. The ability of Amphibola to maintain its rate of oxygen consumption in a wide range of environmental conditions is discussed in relation to its potential for invading terrestrial habitats and its widespread distribution on New Zealand's intertidal mudflats.     

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.     

Salinity affects growth but not thermal preference of adult mummichogs Fundulus heteroclitus

The effects of an ecologically relevant range of salinities (2, 12, 22, 32) on thermal preferences and growth of adult mummichogs Fundulus heteroclitus were determined for fish from a southern Chesapeake Bay population. Salinity did not affect the mean temperature selected by F. heteroclitus in a thermal gradient, which was identified as 26.6°C based on observations of 240 individuals. Salinity and temperature had significant and interacting effects on growth rates of F. heteroclitus measured over 12 weeks. Growth rates were highest overall and remained high over a broader range of temperatures at moderate salinities (12 and 22), while high growth rates were shifted toward lower temperatures for fish grown at a salinity of 2 and higher temperatures at a salinity of 32. Significant reductions in growth relative to the optimal conditions (28.6°C, salinity of 22) were observed at the coolest (19.6°C) and warmest (33.6°C) temperature tested at all salinities, as well as temperatures ≥ 26.6°C at a salinity of 2, ≥ 28.6°C at a salinity of 12 and ≤ 26.6°C at a salinity of 32. Growth rates provide a long-term, organismal measure of performance and results of this study indicate that performance may be reduced under conditions that the highly euryhaline F. heteroclitus can otherwise easily tolerate. The combination of reduced salinity and increased temperature that is predicted for temperate estuaries as a result of climate change may have negative effects on growth of this ecologically important species.     

Hydromineral regulation in the saline water corixid Trichocorixa reticulata (Hemiptera: Corixidae)

The aquatic corixid Trichocorixa reticulata (Guerin-Meneville) inhabits coastal marshes, brackish water ponds and salt ponds of high salinity, suggesting the presence of well developed mechanisms for hydromineral regulation.Groups of corixids acclimated in salinities ranging from fresh water to just above 300% sea water (100‰) were analyzed for total body water content, haemolymph ionic and osmotic levels, and haemolymph free amino acids.Results indicate an excellent ability to maintain haemolymph Na⁺, Cl^?, Mg²⁺ and K⁺ hyperosmotic to the medium at low salinities and hyposmotic at high salinities. Calcium appears to conform closely to changes in external medium, becoming hyposmotic at very high salinities (80‰).Total haemolymph osmotic pressure was well regulated, the freezing point depression varying from 0.75°C in distilled water to 1.15°C in salinities of 100‰. Total body water was maintained at approx. 75% of the total animal wet weight at all salinities tested.Free amino acids were maintained between 40–60 mM in all tests and did not appear to change with salinity.     

Effects of light,temperature and salinity on the growth rate of harmful marine diatoms,Chaetoceros convolutus and C. concavicornis that kill netpen salmon

Chaetoceros convolutus and C. concavicornis have been implicated in the death of salmon in netpens in the Pacific Northwest by damaging the salmon's gills. To better understand how environmental factors affect the distribution of these two species, the interacting effects of light, temperature and salinity on growth rate were examined by growing these species under a range of temperatures (4–18 °C), light (10–175 μmol photon m⁻² s⁻¹) and salinities (10–30‰). For C. convolutus, the growth rate showed a hyperbolic relationship with irradiance at 8, 14 and 18 °C and light saturation occurred at 9, 14 and 20 μmol photon m^t s⁻¹ respectively. At 4 °C for C. convolutus and 8 °C for C. concavicornis, cells grew at μ_max, even at the lowest irradiances tested (10 μmol photon m⁻² s⁻¹). For C. convolutus, the amount of light required to saturate growth rate increased with temperature in an approximately linear fashion. The Q₁₀ was 1.88, calculated by averaging over both species. C. concavicornis was the more euryhaline species growing at salinities as low as 17.5‰, while C. convolutus grew only at 25‰ and above.     

Effects of temperature and salinity on the eggs and early larvae of Caranx mate (Cuv. & Valenc.) (pisces: carangidae) in Hawaii

Eggs and larvae of the carangid fish, Caranx mate (Cuv. & Valenc.), were incubated at various temperature (17.2 to 33.1 °C) and salinity (10 to 42 ‰) combinations in five experiments. The following rates were directly proportional to temperature: embryonic development, yolk absorption, eye and jaw development, and increase in length. Unfed C. mate larvae attained a maximum size at 25 °C and 20 ‰ Eyes and jaws of larvae were functional by the end of the yolk sac stage at all temperature and salinity levels tested.Hatching success and larval survival at the end of the yolk sac stage were generally greater than 50 % between 22° and 32°C. Hatching success and larval survival at the end of the yolk sac stage were reduced at salinity extremes, especially in low temperature-low salinity and high temperature-high salinity combinations. The frequency of morphological abnormalities was also high at extreme temperatures and salinities.The incipient upper thermal TL_m for unfed C. mate larvae acclimated to 23.8°C increased from 31.5°C for newly hatched larvae, to 34.2°C for 72 h larvae, but decreased to 32.0°C for starving larvae after the exhaustion of the yolk supply.     

Photosynthetic and respiratory responses of Gracilaria parvispora from the southeastern Gulf of California

Photosynthetic and respiratory responses (P–E curves) of Gracilaria parvispora from the southeast Gulf of California were studied at four temperatures (20, 25, 30, 35 °C) and salinity (25, 30, 35, 40 psu) combinations. The alga showed acclimation in its photosynthetic and respiratory responses to tropical temperature as well as to oceanic salinity. A positive effect of temperature on photosynthetic rate (P _max) was observed for all salinities. Photosynthetic rates for treatments at 20 and 25 °C were lower (<9.2 mg O₂?g dry weight (dw)^?1?h^?1) than for treatments at 30 and 35 °C (>12 mg O₂ g dw^?1?h^?1). G. parvispora showed limited tolerance to low salinities (25 psu) and low temperatures (20 °C) and the interaction between temperature and salinity was significant (analysis of variance, P?<?0.05). Responses to salinity indicated adaptation to oceanic salinity. Photosynthetic responses were lower at 25 psu than at higher salinities. The lowest P _max values (6.2–8.2 mg O₂?g dw^?1?h^?1) were observed at the lowest salinity (25 psu) regardless of temperature. Compensation and saturation irradiances (26–170 and 57–149 μmol photons m^?2?s^?1, respectively) indicate adaptation to lower irradiances in shallow (1–2 m depth) habitats, where turbidity can be high, and the capacity of shade adaptation has been developed. Results suggest distribution of this species is mainly related to salinity or temperature. The potential mariculture efforts of G. parvispora would be limited by low temperatures in winter, and indicate that this species will probably not be able to spread further due to low temperatures (<15 °C) in the upper part of the Gulf of California.     

Adaptivity of the bivalve Mytilus trossulus larvae to short-and long-term changes in water temperature and salinity

Adaptivity to short-term and long-term changes in water temperature and salinity was studied in larvae of the bivalve mollusk Mytilus trossulus. It was shown that water temperature of 4°C mostly suppressed growth and development of larvae. A temperature of 20°C promoted an enhanced larval growth and development. Though a temperature of 20°C caused enhanced larval growth, the temperature was not optimal, while its effect caused quality diversity of larval development, owing to the difference in their growth rates. Such diversity was not observed at moderate temperatures of 10 and 15°C. At 20°C, fast-growing mussel larvae were very sensitive to temperature drops. Growth of slowly-growing individuals did not depend on temperature in the range of 10 to 20°C. Daily temperature variations by 3–8°C did not markedly affect growth and development of the larvae. A continuous 24-h exposure to temperature drops by 3–8°C did not influence these very important physiological characteristics either. A salinity drop down to 8‰ exerted an adverse effect only on early larvae. Later on, the larvae showed their ability to adapt to such a strong desalination. The negative effect of reduced salinity (to 8‰) upon mussel larvae was increased at a temperature increase to 20°C.     

A laboratory investigation of temperature and salinity tolerances of juvenile Metapenaeus bennettae Racek and Dall (Crustacea: Penaeidae)

Temperature and salinity tolerances of juvenile Metapenaeus bennetlae Racek and Dall were estimated by abrupt exposure to critically high or low levels of each factor following acclimation to 12 combinations of temperature (17, 22, 27 and 32°C) with salinity (5, 20 and 35‰.). No significant differences were found between tolerances of males and females. Acclimation temperature influenced both temperature and salinity tolerances, while acclimation salinity affected only the salinity tolerance. Irrespective of temperature and salinity acclimation levels, juvenile M. bennettae were able to tolerate temperatures from 8.1 to 32.9°C and salinities from 1.0 to 62.0‰ These findings are discussed in relation to similar published studies.     

EFFECTS OF TEMPERATURE,SALINITY, IRRADIANCE AND DIURNAL PERIODICITY ON GROWTH AND PHOTOSYNTHESIS IN THE DIATOM NITZSCHIA AMERICANA; LIGHT-SATURATED GROWTH1

The physiological response of an estuarine clone of Nitzschia americana Fryx3ell was measured under experimental conditions of temperature and salinity which represent the average range of these variables in the Cape Fear River Estuary, North Carolina. The influence of temperature (10, 15, 20, 25, 30°C) and salinity (8, 15, 20, 26, 32‰) on specific growth rates, μ, and parameters of photosynthesis-irradiance curves, α, and P_max were measured during maximum and minimum rates of diurnal photosynthesis using axenic semi-continuous batch cultures maintained at an irradiance saturating for photosynthesis (140 μE m^-2·s-1). There was an increase in μ with increasing temperature up to a broad uptimum (25 ± 2.5°C), above which μ gradually declined. At the predicted optimum temperature of 25°C, μ increased as a linear function of salinity. oth light-limited (α) amd light-saturated (P^max) rates of photosynthesis increased as salinity decreased. The effect of temperature on a and P^max was complex and dependent on salinity. P^max exhibited a diurnal periodicity, whereas estimates of a were not significantly different between sampling periods. Growth efficiencey opf N. americana, calculated as the ratio between specific growth rates and rates of gross photosynthesis, increased with an increase in salinity with a maximum at the predicted optimum temperature and salinity of 25°C and 32‰, suggesting and uncoupling between photosynthesis and growth at nonoptimum growth conditions.     

Ecological physiology of arctic marine invertebrates. Temperature and salinity relationships of the amphipod Onisimus affinis H. J. Hansen

Effects of temperature and salinity upon the survival, locomotion and metabolism of the Arctic marine amphipod Onisimus affinis H. J. Hansen have been investigated. The LD₅₀ for temperature is ≈ 18.7 °C. The metabolic rate-temperature curve shows a distinct plateau of relative temperature insensitivity the position of which varies seasonally to include a lower temperature range in winter than in summer. Similar shifts in the plateau can be induced in the laboratory by acclimating the animals at summer- and winter-like temperatures.Optimal locomotory activity was between 5° and 8 °C and included a combination of swimming and crawling. Above 12 °C the swimming component was increasingly inhibited.Onisimus is euryhaline and appears to be most successful in brackish water habitats. It tolerates elevated salinities better at low temperatures. The metabolic rate varies inversely with salinity during short-term exposures, but, if the animals are pre-adapted to the experimental salinities for 10 days, the metabolic rate is essentially independent of salinity between 10%. and 25%.The significance of these physiological responses in relation to the general ecology of the species is discussed.     

Adaptive significance of hatching rhythms and dispersal patterns of estuarine crab larvae: avoidance of physiological stress by larval export?

Estuarine crabs commonly display two larval dispersal patterns in which larvae are either exported from or retained within estuaries. The semiterrestrial fiddler crab Uca minax (LeConte, 1855) hatches on nocturnal spring high tides in the upper estuary and larvae are rapidly transported downstream. The mud crab Rhithropanopeus harrisii (Gould, 1841) hatches on nocturnal high tides of any amplitude and larvae are retained behaviorally in the upper estuary throughout development. If larvae are exported from the estuary to avoid environmental stress, then exported larvae should be less tolerant of high temperatures and low salinities than retained larvae. Larvae of these two species of estuarine crabs were hatched at 20‰ and 25 °C and subjected to salinities of 0, 5, 10,20, and 30‰, temperatures of 25 and 35 °C, and exposure times of 2, 6, 12, and 48 h. Larvae of both species reared at 30 or 20‰ survived well, while those reared in fresh water all died within 2 h regardless of temperature. Mud crab larvae reared at 5 and 10‰ survived better at the lower temperature (25 °C), higher salinity, and shorter exposure times. There was no significant effect of temperature or salinity on the survival of fiddler crab larvae, although survival decreased with increasing exposure time. Thus, the hypothesis that fiddler crab larvae are exported into stable coastal waters to reduce physiological stress is not supported. However, fiddler crab larvae may have evolved to be very tolerant of extreme temperature and salinity stress because they, unlike mud crabs, often release their larvae into shallow creeks. Most fiddler crab larvae are released on nocturnal spring high tides, which facilitates dispersal from tidal creeks. However, freshwater runoff and heat transferred from the marsh surface to flooding waters may still create stressful conditions for larvae soon after they are released. Larval release on spring high tides may facilitate dispersal from tidal creeks.     

The effect of temperature-salinity combinations on the functional well-being of adult Lytechinus variegatus (Lamarck) (Echlnodermata,Echinoldea)

The activity coefficient (1000/righting time in sec) was measured to indicate the functional state of Lytechinus variegatus (Lamarck) after exposure to combinations of temperature (22°, 28°, and 34°C) and salinity (25, 30, 35, and 40 ‰). Environmental levels of these variables were 30–33°C and 34–35 ‰. The results indicate that the species lives closer to the upper than lower lethal limits of temperature and salinity. The maximal activity coefficient (18 ± 8) was at 28°C and 35 ‰. A reduction in salinity was probably responsible for a recent mass mortality of the echinoid reported in the eastern Gulf of Mexico.     

Survival,osmoregulatory ability,and respiration of idotea chelipes (Crustacea,Isopoda) from lake veere in different salinities and temperatures

1. An ecological and physiological study ofI. chelipes from Lake Veere, The Netherlands, was made.
2. Both osmoregulatory capacity and survival decrease with increasing temperature as well as with decreasing salinity.
3. Respiration experiments suggest that the need of energy by osmoregulatory activity may be supplied at the cost of other physiological processes, at any rate at temperatures of 10°C and higher.
4. It may be expected that, if temperatures higher than 15°C and salinities lower than 8‰ coincide, the population ofI. chelipes will be affected negatively.

     

Effect of temperature and salinity on the gastric evacuation of juvenile sole Solea solea and Solea senegalensis

The juveniles of Senegal sole, Solea senegalensis, Kaup 1858, and common sole, Solea solea (Linnaeus 1758) concentrate in estuarine and coastal nurseries of widely differing temperatures and salinities. Yet, little is known about the effect of these physiologically important variables on the gastric evacuation rates of these species. Gastric evacuation experiments were performed on juveniles of S. senegalensis and S. solea. Three temperatures were tested, 26, 20 and 14°C at a salinity of 35‰. A low salinity experiment was also carried out at 15‰, at 26°C. Experimental conditions intended to reflect conditions in estuarine and coastal nurseries where juveniles of these species spend their first years of life. The relation between stomach contents and time was best described by exponential regression models for both species. An analysis of covariance (ancova ) was performed in order to test differences in evacuation rate due to temperature and salinity (slope of evacuation time against stomach contents) for each species. While increasing temperature increased evacuation rates in both species (although not at 26°C in S. solea), the effect of low salinity differed among species, leading to a decrease in gastric evacuation rate in that of S. senegalensis and an increase in S. solea. Differences in gastric evacuation rate between species were related to its metabolic optimums and to its distribution in the nursery area where fish were captured. Implications for the habitat use of estuarine and coastal nurseries are discussed.     

Acetylcholinesterase activity of the polychaete Nereis diversicolor: effects of temperature and salinity

In order to estimate the potential use of the mean wholebody acetylcholinesterase (AChE) activity from the ragworm Nereis diversicolor for the biological assessment of pollution by anticholinesterase agents in estuarine areas, we measured the effects of the main abiotic factors (i.e. temperature and salinity) on AChE activity. We report here that AChE activity tends to decrease in individuals sampled in tanks at a salinity of 30‰ as temperature increases. No tendencies in the evolution of AChE activity were observed in individuals sampled in tanks at a salinity of 15‰. In contrast, salinity seems to have a greater effect on AChE activity than temperature. At a temperature of 12°C, a salinity of 30‰ provokes a significant transient increase of AChE 2 days after the beginning of the maintenance period compared with a salinity of 15‰. The effects are short-term stress effects. We noticed only a transient increase of AChE activity between 2 days for individuals maintained in tanks at temperature of 20°C and salinity of 15 and 30‰, respectively, and 8 days for individuals maintained in tanks at salinity of 30‰ and at a temperature of 12°C after the beginning of the maintenance period, confirming the more pronounced effect of salinity over temperature.