The effect of food quality on glycogen content,the fatty acid profile and winter mortality in cultivated oyster spat (Ostrea edulis)

Winter mortality in hatchery reared oyster spat (Ostrea edulis) that received three different diets during the summer period was investigated. Oysters fed a natural type diet had a winter mortality of 18.3 ± 6.3% while oysters fed cultivated algae (a mixture of Tetraselmis suecica, Isochrysis galbana and Chaetoceros muelleri) had a mortality of 73.0 ± 9.7%. A group of oysters fed a mix between the two diets had a mortality of 54.7 ± 10.6%. Tissue samples were taken at the start of the experiment, after the summer period and after the winter period in order to determine growth and the content of glycogen and fatty acids. The glycogen content decreased for all groups during the winter but the decrease was highest in oysters fed the natural diet. This group also contained the largest variety of fatty acids, but there was no difference in the content of the essential fatty acids EPA, DPA and DHA between the groups. It is concluded that transplantation of spat to the sea in spring and early summer may reduce winter mortality since the feeding period on a more varied natural algal diet is prolonged compared to transplantation of spat later in the season.     

Interacting effects of dietary lipid level and temperature on growth, body composition and fatty acid profile of rohu, Labeo rohita (Hamilton)

Three isonitrogenous (320 g kg^?1 crude protein, casein and gelatine) semi‐purified diets with 80 (L8), 130 (L13) and 180 (L18) g kg^?1 lipid (sunflower oil at increasing levels and cod liver oil fixed at 50 g kg^?1) at three digestible energy levels (12 096, 13 986 and 15 876 kJ kg^?1 dry weight) and were tested, in triplicate, on rohu fingerlings (3.2 ± 0.08 g) at two different temperatures (21 and 32 °C). Fish were fed to apparent satiation, twice daily, at 09.00 and 15.00 h, 7 days a week for 56 days. Maximum growth was obtained at a lipid level of 80 g kg^?1 (L8) at 21 °C (439.37%) and 130 g kg^?1 (L13) at 32 °C (481.8%). In general growth rate was higher at 32 °C than at 21 °C at all lipid levels. Tissue monounsaturated fatty acid (MUFA) contents decreased with increasing lipid level at 32 °C, but the reverse occurred at 21 °C. At 21 °C, Polyunsaturated fatty acid (PUFA) level increased significantly (P > 0.05) over initial values, but was affected insignificantly by dietary lipid level. At 32 °C, fish fed diet L13 had more n‐3 fatty acid (FA) in liver and muscle than the other two dietary groups while at 21 °C, both liver and muscle FA profiles exhibited significant change (P > 0.05) in n‐3 and n‐6 FA content which corresponded to variation in percent addition of dietary lipid. However, n‐3/n‐6 ratio was higher for fish fed diet L13 at 32 °C and diet L8 at 21 °C and may be correlated with fish growth.     

Temperature-dependent lipid levels and components in polar and temperate eelpout (Zoarcidae)

Total lipid content, lipid classes and fatty acid composition were analysed in tissues from two eelpout species fed on the same diet, the Antarctic Pachycara brachycephalum and the temperate Zoarces viviparus, with the aim of determining the role of lipids in fishes from different thermal habitats. The lipid content increased with decreasing temperature in the liver of both species, suggesting enhanced lipid storage under cold conditions. In P. brachycephalum, lipid composition in the liver and muscle was strongly dominated by triacylglycerols between 0 and 6°C. In contrast, in the temperate species, lipid class composition changed with changes in the temperature. When acclimatized to 4 and 6°C Z. viviparus not only displayed a shift to lipid anabolism and pronounced lipid storage, as indicated by high triacylglycerol levels, but also a shift to patterns of cold adaptation, as reflected by an increased content of polyunsaturated fatty acids in the lipid extract. Unsaturated fatty acids were also abundant in the Antarctic eelpout, but when compared to Z. viviparus at the same temperatures, the latter had significantly higher ratios of polyunsaturated to saturated fatty acid levels, whereas the Antarctic eelpout showed significantly higher ratios of monounsaturated to saturated fatty acid levels. High δ-¹⁵N values of the Antarctic eelpout reflect the high trophic level of this scavenger in the Weddell Sea food web. Stable carbon values suggest that lipid-enriched prey forms a major part of its diet. The strategy to accumulate storage lipids in the cold is interpreted to be adaptive behaviour at colder temperatures and during periods of irregular, pulsed food supply.     

Changes in lipid class and fatty acid composition of adult male Litopenaeus vannamei (Boone) in response to culture temperature and food deprivation

The effects of culture temperature and food deprivation on lipid class and fatty acid composition of adult male Litopenaeus vannamei (Boone) were investigated. Shrimp were maintained in recirculating seawater systems at temperatures of 26 and 32°C and fed 75% dry commercial feed and 25% fresh‐frozen squid for 42 days. Additionally, groups of fed and non‐fed shrimp were maintained at 26°C for 17 days. In shrimp fed at either 26 or 32°C, polar lipids were the main constituents of total identified lipid classes in muscle tissue (66–71%), while neutral lipids were more abundant in hepatopancreas (82–88%). Higher levels of triglycerides were observed in lipids of shrimp hepatopancreas kept at 32°C, but no other lipid class was affected by temperature. A significantly higher proportion of 22:6n‐3 was consistent in muscle and hepatopancreas polar and neutral lipids of shrimp maintained at 26°C. In response to food deprivation, the amount of polar lipids, but not neutral lipids, was reduced by approximately 28% in muscle tissue, whereas all lipid reserves were almost depleted in the hepatopancreas. The variable consumption of some individual fatty acids was observed in polar and neutral lipids of both tissues.     

Tetraploid induction in tropical oysters,Crassostrea belcheri (Sowerby) and Crassostrea iredalei (Faustino)

Tetraploid induction has been conducted on temperate oysters but not on tropical oysters. In this study, different heat shocks (32, 35 and 38°C) and cold shocks (1, 4 and 7°C) were used to induce tetraploidy in two tropical oyster species, Crassostrea belcheri and Crassostrea iredalei, through meiosis I inhibition. Temperature shocks were applied on the newly fertilized eggs at 8–10 min post fertilization and terminated when second polar bodies began to form in the control eggs. The ploidy of the larvae and spat was determined via direct chromosome count. The percentage of larval survival until Day 20 was low (between 0.4% and 42.9%) for both temperature shocks and oyster species. No surviving larva was recorded for induction at 1, 4 and 38°C. Tetraploid spat was only recorded in C. iredalei but the percentage is low through heat shock induction of 32 and 35°C. This study shows that the tetraploid induction success rate was slightly higher in C. iredalei compared to C. belcheri. No surviving tetraploid spat were recorded for both oyster species through the cold shock method. This study shows that heat shock can be used to inhibit meiosis for the production of tetraploids but more experiments need to be conducted to determine the optimum temperature when dealing with tropical oysters.     

Long‐chain PUFA enrichment in microalgae and metabolic dynamics in Tapes philippinarum larvae

The possibility of increasing n‐3 and n‐6 long‐chain polyunsaturated fatty acids (PUFA) content in microalgal mixtures used to feed Tapes philippinarum larvae was explored by lowering culture temperature from 26 to 14 °C. Although fatty acid composition of different microalgal species has a genetic basis, the algal cultures grown at 14 °C significantly increased the content of long‐chain n‐3 PUFA in Isocrysis galbana and in Thalassiosira pseudonana, while in Tetraselmis tetrathelo, the PUFA increase only involved shorter chain PUFA, namely 16:4n‐3 and 18:4n‐3. However, larvae fed on the PUFA enriched microalgal mixture did not show improvements in growth and survival performances with respect to the control group fed the microalgal mixture grown at 26 °C. From a biochemical perspective, two key aspects emerged from the results: (i) clam larvae have adequate biotransformation and selection skills to adjust fatty acid profile to their requirements as they can even modulate the incorporation of essential long‐chain PUFA as 20:5n‐3 and 22:6n‐3 when the dietary supply exceeds the physiological requirements; (ii) bivalve can biosynthesize non‐methylene‐interrupted dienoic (NMID) fatty acids as confirmed by the constancy of relative proportion with larvae growth in spite of the NMID fatty acid absence in the diet.     

Comparative low temperature tolerance of small juvenile European, Ostrea edulis L., and Pacific oysters, Crassostrea gigas Thunberg

The present investigation was carried out to measure the survival of juvenile oysters (spat) of a native species, European oyster, Ostrea edulis L., and an introduced species, Pacific oyster, Crassostrea gigas Thunberg, at typical winter seawater temperatures in the British Isles. Two size groups of each species were maintained either unfed or with low algae rations at 3, 6 and 9^oC for up to 11 weeks. The majority of O. edulis juveniles survived for 11 weeks at all temperatures. Unfed animals utilized biochemical reserves and lost organic weight during this period. Fed O. edulis showed a small weight loss at 3^oC, but increased in weight at 6^oC and 9^oC. At all temperatures, O. edulis preferentially utilized lipid reserves in treatments in which organic weight was lost. In contrast, C. gigas juveniles preferentially utilized protein as an energy source. All C. gigas juveniles survived at 9 and 6^oC, but high mortalities (> 95%) occurred after 3-7 weeks at 3^oC. Both fed and unfed C. gigas juveniles lost weight, reserves and condition at 3^oC. Juveniles grew when fed at 6 and 9^oC. In both oyster species, the proportion of phospholipid (n-6) fatty acids, principally 20 : 4 (n-6) increased in those juveniles which showed a decrease in organic weight. Food cell consumption rates were lower at lower temperatures and were higher in O. edulis at 9^oC than in C. gigas. The results are discussed with respect to recruitment and winter survival of small juveniles.     

Comparative growth and survival of spat of the Caribbean pearl oyster,Pinctada imbricata cultivated indoor with microalgae diets and outdoor with natural diet

We report the results of survival and growth in size and dry mass of spat of the Caribbean pearl oyster Pinctada imbricata cultivated under outdoor (field culture) and indoor (Laboratory) conditions. Field group fed on environmental seston. Laboratory groups were fed with mono, binary and ternary mixtures of three cultivated algae: Isochrysis galbana (Ig), Tetraselmis chuii (Ig) and the Chaetoceros sp. (Ch‐A, isolated from north‐eastern Venezuela). After 30 days of trial, fatty acid profiles of spat were determined along with growth in length and height shell, adductor muscle and soft tissue dry mass. During the field grow‐out phase (field culture), samplings were performed at days 1, 15 and 30 to measure environmental variables of phytoplankton biomass (chlorophyll a), dissolved oxygen, seston, temperature and salinity. A significant increase in size and soft tissue mass occurred in spat fed the diets including the tropical diatom (Chaetoceros sp.). In contrast, monoalgal diets of Tc and Ig yielded no significant differences in size and mass of spat, compared with the field culture. These results suggest that nutritional requirements of cultivated spat for specific fatty acids of physiological importance for marine bivalves, such as: 16:0, 16:1n‐7, 18:2n‐6, 20:4n‐6, 18:3n‐3 and 20:5n‐3, were satisfied from microalgal diets with Ch‐A, alone or in combination, compared with spat fed from the field culture.     

Dietary lipid sources affect the performance of Nile tilapia at optimal and cold,suboptimal temperatures

Five sources of dietary fatty acids (fish, linseed, sunflower, olive and coconut oils) were evaluated in juvenile Nile tilapia in two trials: at optimal (28°C) and suboptimal (22°C) temperatures lasting 9 and 12 weeks, respectively. At 28°C, there was no clear effect of dietary source on fish growth, but at 22°C, the highest daily weight gain occurred in fish fed sunflower, linseed and fish oil. Feed efficiency and apparent net protein utilization increased as the amount of unsaturated fatty acids, especially n‐3 polyunsaturated fatty acids (PUFA), in the diet increased. Coconut oil, which is rich in saturated fatty acids (SFA), led to the worst growth results, especially at 22°C, with the lowest weight gain, feed intake and feed utilization by tilapia. The body fatty acid profile, in % of total fatty acids, was dependent on diet composition. However, for all treatments, PUFA body content increased with the decrease in temperature, but SFA and monounsaturated fatty acids remained the primary contributors to the body profile. Either fish oil or vegetable oil may be used as sources of dietary fatty acids for Nile tilapia, but at suboptimal temperatures, a dietary source containing more PUFA and less SFA improves performance.     

Diet and water temperature affect growth and body deformities in juvenile tench Tinca tinca (L.) reared under controlled conditions

The experiment was designed to determine the combined effect of fish diet and water temperature on juvenile tench Tinca tinca (L.). Three diets were used: commercial dry diet for fish Aller Futura (diet F); frozen Chironomidae larvae (diet C); and Aller Futura substituted with Chironomidae at a ratio of 3:2 (dry weight; diet FC). Daily food rations and duration of the experiment were adjusted to temperatures of 20°C, 23°C and 26°C based on a correction factor q equal to 1.000, 0.779 and 0.609 respectively. The experiment lasted 92, 72 and 56 days for the respective temperatures. No mortality occurred. The highest relative growth rates were found at 26°C in diets F and FC. The lowest food conversion ratio of 1.12–1.22 (recalculated for dry weight of feed diet) was determined in fish fed diet F at 23°C and 26°C. A high value of condition index appeared to be the early warning of decreasing biological quality of fish and deformities. The lowest incidence of fish with deformities (IDef) was found in groups fed diet C (<1%), while the highest (90%) in fish fed diet F at 26°C. A lower share of dry diet in the fish food and a lower water temperature led to a lower IDef. Thus, amount of dry feed in fish diet was the major factor inducing body deformities, while water temperature only modified the effects of the dietary factor. Diet C at 23–26°C was the most cost‐effective of the tested combinations of diet and temperature.     

The effect of temperature and dietary fat level on tissue lipid composition in Atlantic salmon (Salmo salar) fed wax ester‐rich oil from Calanus finmarchicus

Copepod oil (CO) from the marine zooplankton, Calanus finmarchicus, is a potential alternative to fish oils (FOs) for inclusion in aquafeeds. The oil is composed mainly of wax esters (WE) containing high levels of saturated fatty acids (SFAs) and monounsaturated fatty alcohols that are poorly digested by fish at low temperatures. Consequently, tissue lipid compositions may be adversely affected in salmon‐fed CO at low temperatures. This study examined the lipid and FA compositions of muscle and liver of Atlantic salmon reared at two temperatures (3 and 12 °C) and fed diets containing either FO or CO, supplying 50% of dietary lipid as WE, at two fat levels (～330 g kg^?1, high; ～180 g kg^?1, low). Fish were acclimatized to rearing temperature for 1 month and then fed one of four diets: high‐fat fish oil (HFFO), high‐fat Calanus oil (HFCO), low‐fat fish oil (LFFO) and low‐fat Calanus oil (LFCO). The fish were grown to produce an approximate doubling of initial weight at harvest (220 days at 3 °C and 67 days at 12 °C), and lipid content, lipid class composition and FA composition of liver and muscle were determined. The differences in tissue lipid composition between dietary groups were relatively small. The majority of FA in triacylglycerols (TAG) in both tissues were monounsaturated, and their levels were generally higher at 3 °C than 12 °C. Polyunsaturated fatty acids (PUFA), particularly (n‐3) PUFA, predominated in the polar lipids, and their level was not significantly affected by temperature. The PUFA content of TAG was highest (～26%) in the muscle of fish fed the HFCO diet at both temperatures. Tissue levels of SFAs were lower in fish‐fed diets containing HFCO than those fed HFFO, LFFO or LFCO, particularly at 3 °C. The results are consistent with Atlantic salmon being able to incorporate both the FA and fatty alcohol components of WE into tissue lipids but, overall, the effects of environmental temperature on tissue lipids were more pronounced in fish fed the CO diets than FO diets.     

Use of premature New Zealand dredge oyster Tiostrea lutaria Hutton larvae for spat production

The New Zealand dredge oyster Tiostrea lutaria Hutton is an incubatory ostreid species that produces fully developed pediveliger larvae, which typically settle shortly after release from the parent. Broods of larvae obtained by opening incubating oysters provide a potential method of spat production, but only a small proportion of the broods obtained in this way are the late‐stage, ready‐to‐settle pediveligers. The majority of the broods are gastrula‐, trochophore‐ and veliger‐stage larvae. Experiments were undertaken to determine whether these early stages, as well as the pediveliger stage, could be reared through to settlement, and so make spat production based on opening incubating oysters much more efficient. Experiments conducted at three temperatures (ambient, ambient + 3 °C and ambient + 6 °C) and under three food regimes (with and without cultured microalgae and without dissolved organics) were unsuccessful in ex‐parent rearing of early larvae (gastrulae and trochophores). Later stage larvae, both veligers and pediveligers, were successfully reared, and high (> 75%) but variable levels of settlement were achieved. Ex‐parent rearing did not benefit from elevated temperatures or the presence of food, and settlement of spat from these prematurely released larvae may be reduced in the presence of food. The ability to rear veliger larvae, as well as pediveligers, greatly increases the potential to use the opening of incubating adult oysters during the breeding season as a source of dredge oyster spat.     

Growth of the oyster Crassostrea corteziensis (Hertlein, 1951) in Sonora, Mexico

This is the first evaluation of growth and survival of spat of the Cortez oyster Crassostrea corteziensis (Hertlein) produced under controlled conditions in a coastal area in the state of Sonora, Mexico for aquaculture purposes. A suspended culture technique, used for the Pacific oyster C. gigas, was used. The Cortez oyster has an isometric shell growth during the first 13 months, reaching 71.3±1.9 mm length, 52.6±1.3 mm thickness and 25.1±0.8 mm width. Allometric growth was found between total weight and length, thickness and width (survival was 70%). The relationships between particulate organic, inorganic material, chlorophyll a and environmental parameters with growth are described. Growth rates of C. corteziensis were affected by temperature with retardation at less than 18°C. For aquaculture purposes, it is recommended that spat be sowed after winter, and oyster harvest occur at the end of autumn. According to the von Bertalanffy equation, Cortez oysters would reach the traditional exploitation size of 65 mm (mean length) at harvest. Finally, the results of this study have shown that C. corteziensis is a good candidate for aquaculture projects in this region.     

Growth and survival of juvenile spider crabs,Maja brachydactyla (Balss, 1922), fed with fresh or frozen mussels

The effects of diet freezing on the growth, survival and biochemical composition of the diets and juvenile spider crabs (Maja brachydactyla) were studied. Fresh and frozen (at ?20 °C for 21 days) mussels, Mytilus edulis, were used as food. Two experiments were conducted and in each, spider crabs were placed in individual trays. During experiment I, 40 juvenile spider crabs (2 months old) were used. Twenty animals (9 ± 2 mg) were fed fresh mussels, and 20 animals (8 ± 2 mg) were fed frozen mussels. Spider crabs fed fresh mussels grew larger than the ones fed frozen mussels (304.0 ± 118.0 and 70.0 ± 40.1 mg respectively). During experiment II, 16 juvenile spider crabs (5 months old) were used. Eight animals (3.4 ± 0.8 g) were fed fresh mussel and eight animals (4.1 ± 1.3 g) were fed frozen mussel. Spider crabs fed with fresh mussels were larger than the ones fed with frozen mussels (92.5 ± 41.7 and 41.5 ± 17.7 g respectively). There were no significant differences in the protein, amino acids and fatty acid composition between fresh and frozen mussels. The freezing procedure makes mussels less adequate for the culture of 2‐month‐old early juveniles of M. brachydactyla up to 5 months, although they promoted acceptable growth and good survival in older animals (>5 months old).     

Effects of high carbohydrate and high lipid diets on growth,body composition and glucose metabolism in southern catfish at two temperatures

The effects of high carbohydrate and high lipid diets on the growth, body composition and glucose metabolism in the southern catfish were determined at 17.5 °C and 27.5 °C. At each temperature, the feeding rate, specific growth rate and protein productive value decreased with increasing dietary carbohydrate (P<0.05). Feed efficiency and protein efficiency ratio were lower in the fish fed a high dietary carbohydrate diet at 17.5 °C, but were not significantly different between diets at 27.5 °C. Plasma glucose and activities of pyruvate kinase and glucose‐6‐phosphate dehydrogenase were higher in fish reared at 27.5 °C than those reared at 17.5 °C, and within each temperature, they were higher in fish fed the high‐carbohydrate diet. Hepatosomatic index was higher in fish fed the high‐carbohydrate diet than those fed the high‐lipid diet at 27.5 °C, but no significant difference was found at 17.5 °C. The results indicate that higher temperatures enhance glycogen deposition and lipogenous enzyme activities when fed with a high‐carbohydrate diet; thus, at higher temperatures, this fish uses carbohydrate more efficiently for protein sparing.     

Dietary ratios of n‐3/n‐6 fatty acids do not affect growth of Nile tilapia at optimal temperatures (28°C) nor at temperatures that simulate the onset of winter (22°C)

Nile tilapia (Oreochromis niloticus) juveniles were fed diets containing 13 g/kg total polyunsaturated fatty acids (PUFAs) at different n‐3/n‐6 dietary ratios (0.2, 0.5, 0.8, 1.3 and 2.9) for 56 days, at 28°C. Subsequently, fish were submitted to a winter‐onset simulation (22°C) for 33 days. PUFA n‐3/n‐6 dietary ratios did not affect fish growth at either temperature. At 28°C, tilapia body fat composition increased with decreasing dietary PUFA n‐3/n‐6. Winter‐onset simulation significantly changed feed intake. The lowest dietary n‐3/n‐6 ratio resulted in the highest feed intake. At both temperatures, body concentrations of α‐linolenic acid, docosahexaenoic acid, eicosatrienoic acid and docosapentaenoic acid decreased as dietary n‐3/n‐6 decreased. Body concentrations of eicosapentaenoic acid (EPA, 20:5 n‐3) increased with decreasing concentrations of dietary EPA. The n‐6 fatty acids with the highest concentrations in tilapia bodies were linoleic acid and arachidonic acid (ARA, 20:4 n‐6). At 28°C, SREBP1 gene expression was upregulated in tilapia fed the lowest n‐3/n‐6 diet compared to tilapia fed the highest n‐3/n‐6 ratio diet. Our results demonstrate that a dietary PUFA of 13 g/kg, regardless of the n‐3/n‐6 ratio, can promote weight gains of 2.65 g/fish per day at 28°C and 2.35 g/fish per day at 22°C.     

Effect of water temperature and chlorophyll abundance on shell growth of the Japanese pearl oyster, Pinctada fucata martensii, in suspended culture at different depths and sites

To understand the relationships between shell growth and some environmental factors, we examined the relationships between water temperature or chlorophyll abundance and the shell growth of the Japanese pearl oyster, Pinctada fucata martensii, suspended at three different depths at two sites. Growth in height, length and thickness of the shells were limited by water temperature during winter (< 20 °C), whereas growth in thickness correlated with food abundance, measured as chlorophyll, during early summer (> 20 °C). These results suggest that the shell of P. fucata martensii could grow well at locations with greater abundance of food and adequate water temperatures (20–26 °C), resulting in a longer growing season.     

Dietary strategies to improve the growth and feed utilization of barramundi,Lates calcarifer under high water temperature conditions

Several dietary strategies to ameliorate poorer growth observed to occur at temperatures above the upper thermal optima were examined with juvenile barramundi (Lates calcarifer). A reference (REF) and three experimental diets, one with an increased protein to energy ratio (PRO), another with an increased level of the amino acid histidine (HIS) and a third with supplementation of dietary nucleotides (NUC), were each fed to fish at either 30 °C or 37 °C for a 28‐day period. Growth was affected by both temperature and diet. Fish fed the PRO diet at 30 °C grew fastest, but not faster than those fed the NUC diet at the same temperature. The addition of the amino acid histidine to the diet did not improve growth rates at either temperature. At water temperatures of 37 °C, only the fish fed the PRO diet had growth rates equivalent to those of fish at the 30 °C temperatures. Other key factors including feed intake, feed conversion rate, nutrient and energy retention and plasma enzymology were also all affected by temperature and diet. This study shows that the use of a diet with an increased protein to energy ratio provides significant benefits in terms of reducing the impact of growth retardation at higher temperatures.     

Rearing of European grayling, Thymallus thymallus L., larvae using dry and live food

Abstract. European grayling, Thymallus thymallus L., larvae, after hatching, were fed solely on a dry food diet and compared to those fed live zooplankton. After 28 days of rearing at temperatures ranging from 15·0°C to 18·3°C (mean, 16·4°C) fish fed the dry diet reached 0·21 g individual wet weight and 31mm in total length; those fed zooplankton reached 0·13g and 27·5 mm respectively. The survival rate of fish fed the dry diet was higher (56·6%) than that of fish fed the live food (40·7%). Results are discussed in the light of the development of the alimentary tract in the early ontogeny of grayling.     

Feeding physiology and scope for growth of the oyster Crassostrea corteziensis (Hertlein, 1951) acclimated to different conditions of temperature and salinity

There is a particular interest in Mexico for the grow-out and breeding in captivity of the native oyster Crassostrea corteziensis. However, there is a lack of knowledge of the effect of temperature and salinity on the feeding physiology that maximizes the growth and eventually achieves the maturation of C. corteziensis. Our aim was to evaluate the filtration and clearance rates, oxygen consumption, ammonium excretion rates, assimilation efficiency, and scope for growth of the oyster C. corteziensis acclimated during 2 weeks to different combinations of temperature (23, 26, 29, and 32 °C) and salinity (20, 30, 40, and 50 psu). Oysters were fed with a standard suspension of the microalga Chaetoceros muelleri as total particulate matter, which was supplied at 4.2 L h^?1 into 10 1-L tanks used as experimental chambers. The results showed that filtration and clearance rates increased with increasing temperature and decreased with increasing salinity, with the highest values obtained at 29 °C and 20 psu. Ammonium excretion and, to lesser extent, oxygen consumption matched with the variations in the feeding rate. The values of the scope for growth (SFG) suggested that C. corteziensis is able to grow out in all combinations of temperatures and salinities tested in this work. However, the SFG decreased at higher salinity (50 psu) in both extreme temperatures (23 and 32 °C), with highest value occurring at intermediate temperature and the lowest salinity. The SFG increased with increasing temperature and decreased with increasing salinity, which was explained by the increase in the feeding rates and ammonium excretion, coupled with higher absorption efficiency of the food. We concluded that higher filtrations and scope for growth of oysters occurred at 29 °C in brackish-water (20 psu) rather than in marine-water conditions. The results obtained can be considered highly useful information for aquacultural management of this oyster species, and useful to establish suitable sites to enhance their cultivation and maximize the growth of C. corteziensis.