Juvenile Australian Red Claw Crayfish Research Articles

Methodology for assessing the food attractiveness of feeding objects on the example of juvenile Australian red claw crayfish

The aim of the work: to identify behavioral responses that make it possible to characterize the food attractiveness of potential feeding objects for juveniles of the crayfish Cherax quadricarinatus.Used methods: the study was conducted on the juvenile Australian red-clawed crayfish C. quadricarinatus, in the aquarium room of aquaculture invertebrate department at VNIRO. 11 types of feeding objects of plant and 4 types of animal origin were studied, as well as TetraWaferMix compound feed as a control. A total of 616 experiments were performed.Newness: on the juveniles of the Australian red-clawed crayfish C. quadricarinatus, the methodology for assessing the nutritional attractiveness of feeding objects by the nature of behavior during feed consumption was tested.Result: the experiments conducted showed that a large proportion of individuals who threw, crumbled, held food with their oral limbs for a long time without attempting to mechanical processing it or did not eat the food, indicates its unsatisfactory nutritional qualities. The time spent by crayfish on eating food depends on the hardness of the proposed components, the rate of their softening in water, the size of individuals and therefore cannot directly characterize the nutritional attractiveness of the feed. Most of the proposed forage objects (11 out of 15) had attractive nutritional characteristics for juveniles of C. quadricarinatus crayfish. The most active juveniles consumed animal feed (larvae of Chironomus sp. and Hermetia illucens, squid meat, Gammarus sp.), and among the feeds of plant origin, the seeds of oats, wheat and fried buckwheat, as well as beets and potatoes had the greatest attractiveness.

The effectiveness of using the microbial synthesis protein “Gaprin” in feeding juvenile Australian red-clawed crayfish

In the conditions of the scientific center “Breeding valuable breeds of sturgeon” of the Volgograd State Agrarian University, the effectiveness of replacing 75% of fishmeal in the feed for juvenile Australian red claw crayfish with microbial protein - haprin has been experimentally proven. The influence of experimental feeds on weight gain, linear indicators and survival of individuals was studied, and their economic efficiency was determined. Practical recommendations have been developed to allow the implementation of the developed recipe at aquaculture enterprises containing Australian red-claw crayfish.

Efficiency assessment of the use of compound feeds with protein different levels for juveniles Australian red claw crayfish in RAS conditions

The aim of the work is to investigate the effect of compound feeds with different levels of protein on the growth of juveniles of the Australian red claw crayfish Cherax quadricarinatus. Used methods: To solve this problem, two experiments were carried out in the aquariums of aquaculture invertebrate department at VNIRO: the first was on juveniles weighing 0.017 ± 0.004 g and 0.87 ± 0.08 mm long; the second one was on juveniles weighing 0.31 ± 0.14 g and 23.7 ± 3.9 mm long. The duration of the experiments was 30 and 40 days, respectively. Feeding of juveniles was carried out with three variants of compound feed recipes with an estimated protein content of 25 %, 35 % and 45 %. The main part of the formulations consisted of components of plant origin. Tetra Wafer Mix food for fish and crustaceans (Germany) with a protein content of 45 % was used as a control. The duration of the experiments was 30 and 40 days, respectively. Feeding of juveniles was carried out with three variants of compound feed recipes with an estimated protein content of 25 %, 35 % and 45 %. The main part of the formulations consisted of components of plant origin. Tetra Wafer Mix food for fish and crustaceans (Germany) with a protein content of 45 % was used as a control. Newness: Development of a feed formulation for rearing juveniles of the Australian red claw crayfish in recirculating aquaculture systems (RAS). Results: These experiments showed that the growth rate of juvenile Australian red claw crayfish is directly dependent on the proportion of protein in the feed. It was established that the relative content of protein in the muscles of crayfish depends on its content in compound feed. An analysis of our own and published data indicates that feeds with protein content below 35 % cannot be recommended for growing of juveniles’ Australian red claw crayfish. Feeds with a protein content of 45 % are optimal for the growth of juveniles. It was established that the effectiveness of compound feeds depends not only on the protein content and energy value, but also on their taste attractiveness. Practical significance: The obtained results will be used in the development of mixed feed for juveniles Australian red claw crayfish.

Effects on growth, survival, body composition, processing traits and water quality when feeding a diet without vitamin and mineral supplements to Australian red claw crayfish (Cherax quadricarinatus) grown in ponds

To be profitable, producers must reduce diet costs, which can be as high as 80% of the variable costs of an aquaculture expense. As vitamin and mineral premixes represent a significant cost, eliminating addition of these premixes could reduce diet costs if no adverse effects were observed for growth and production parameters. A 105-day feeding trial was conducted with juvenile Australian red claw crayfish (Cherax quadricarinatus) to evaluate the effects of growth, survival, body composition, processing traits and water quality when red claw were fed a supplemental diet containing 28% crude protein (CP) without vitamin and mineral premixes (and supplemented alfalfa hay) compared with red claw fed a diet (control diet) containing 42% CP, vitamin and mineral premixes, and with supplemented alfalfa hay, and compared with red claw only fed alfalfa hay when grown in ponds. Juvenile red claw (mean weight of 15.7 ± 1.0 g) were randomly stocked into nine 0.02-ha ponds at a rate of 640 per pond (3.2 per m2), and each treatment was used in three ponds. There were two feedings per day, each consisting of one-half of the total daily ration. At harvest, individual weight, percentage weight gain, specific growth rate, survival and total yield of red claw fed a control diet was significantly higher (P < 0.05) (83.0 g, 398%, 1.53% day−1, 65.1%,and 1708 kg ha−1 respectively) compared with red claw only fed alfalfa hay (44.9 g, 202%, 1.04% day−1, 30.3% and 431 kg ha−1, respectively), but not different (P > 0.05) from red claw fed the supplemental diet without vitamin and mineral premixes (76.2 g, 367%, 1.47% day−1, 57.2% and 1378 kg ha−1). There were no significant differences (P > 0.05) in feed conversion ratio (FCR) among treatments, which averaged 5.0 (based on prepared diet input). These results indicate that vitamin and mineral supplementation in a diet is not necessary when diet containing 28% CP and alfalfa hay are used in combination for pond grown red claw. These results may help reduce diet costs and possibly increase producers’ profits which might allow for industry expansion.

Effect of Dietary Carbohydrate‐to‐lipid Ratios on Growth Performance, Body Composition, Hepatic Enzyme Activities, and Digestive Enzyme Activities of Juvenile Australian Redclaw Crayfish, Cherax quadricarinatus (von Martens)

AbstractA growth experiment was conducted to determine the optimal dietary carbohydrate‐to‐lipid (CHO : L) ratio for the Australian redclaw crayfish, Cherax quadricarinatus (von Martens). Specimens were divided into five treatment groups and fed twice a day to apparent satiation with isonitrogenous and isoenergetic diets with dietary CHO : L ratios of 10.75:1, 5.99:1, 3.60:1, 2.18:1, or 1.33:1. Over the 8‐wk growth trial, redclaw crayfish fed the 2.81:1 and 3.60:1 diets exhibited better weight gain (WG), specific growth rate (SGR), and feed conversion ratio (FCR) than specimens fed the other diets (P &lt; 0.05). Activities of hexokinase and pyruvate kinase were stimulated by elevated levels of dietary carbohydrate, whereas activities of lipase and alkaline phosphatase were stimulated by elevated levels of dietary lipid. Dietary CHO : L ratios significantly affected digestive enzyme activities (P &lt; 0.05), except for trypsin (P &gt; 0.05). On the basis of the analysis of growth, FCR, and costs of culturing redclaw crayfish, the optimal growth and costs occurred when the dietary carbohydrate and lipid levels were 290.10 g/kg and 80.70 g/kg, respectively, corresponding to a CHO : L ratio of 3.60:1. These results indicate that a CHO : L ratio of 3.60:1 is optimal for rearing redclaw crayfish and that this species uses carbohydrate more efficiently than lipid.

Acute effects of ammonia on antioxidative response and gill Na+/K+ ATPase activity of juvenile Australian red claw crayfish (Cherax quadricarinatus)

The acute toxicity of ammonia to juvenile Cherax quadricarinatus was evaluated. The 24-, 48-, 72-, and 96-h LC50 values of total ammonia nitrogen (TAN) were 51.02 (44.58–58.43), 24.99 (19.17–32.89), 17.83 (13.50–37.22), and 15.38 (8.50–27.94) mg L−1 while the LC50s of un-ionized ammonia nitrogen (NH3–N) were 1.19 (1.04–1.37), 0.58 (0.45–0.77), 0.42 (0.32–0.87), and 0.36 (0.20–0.65) mg L−1, respectively. The safe concentration of ammonia (NH3) for juvenile C. quadricarinatus was TAN = 1.8 mg L−1 (NH3–N = 0.04 mg L−1, pH 7.6, 26°C). LC50 of NH3 decreased significantly with time and fitted a hyperbolic decay model well. Based on the LC50 values, a 96-h NH3 exposure was then conducted, using four test concentrations (4, 8, 12, and 16 mg L−1 TAN) plus a control group. Hepatopancreas catalase (CAT) and superoxide dismutase (SOD) activities fluctuated with time and NH3 concentration and had a similar trend at 24 and 48 h. Both exhibited a peak after 24 h of exposure to 8 mg L−1 TAN and did not change significantly at 48 h. At 96 h, SOD activity significantly decreased with increasing NH3 concentration while CAT activity remained unchanged. Malondialdehyde (MDA) level in hepatopancreas did not change in any groups at 24 h. At 48 and 96 h, it increased as NH3 concentration increased. There was no significant interaction between time and NH3 concentration on SOD, CAT, nor MDA. After 96 h, notable depressions of the gill Na+/K+ ATPase activity were observed in high NH3 concentration groups. The results suggest that the observed lethal toxicity of NH3 could be related to a gradual dysfunction of antioxidant systems and Na+/K+ ATPase activity leading to antioxidant system and osmoregulatory depression. The results will be helpful to aquaculture farmers in preventing depression of productivity caused by elevated NH3.

Dietary non-protein energy sources: growth,physiology and biochemisty by the juvenile Australian redclaw crayfish, Cherax quadricarinatus(Von Martens)

A growth experiment was conducted to determine the optimal carbohydrate-to-lipid(CHO∶ L)ratio for juvenile Australian redclaw crayfish[initial weight(1.72±0.01) g(mean±SD)]cultured in indoor recirculating aquaculture system.Five isonitrogenous[(31.130±0.004) g/kg]and around isoenergetic[(17.490±0.396) MJ/kg]diets with dietary CHO∶ L ratios are 10.75∶ 1,4.81∶ 1,2.66∶ 1,1.52∶ 1 and 0.87∶ 1,were fed twice a day to apparent satiation.Over 8-week growth trial,the best final weight,weight gain,specific growth rate and feed conversion ratio value(P0.05)were observed in redclaw crayfish fed diets with a CHO∶ L ratio of 2.66∶ 1.Redclaw crayfish fed either the lowest(0.87∶ 1)or highest(10.75∶ 1)CHO∶ L ratio tended to produce lower growth and poorer feed conversion ratio.Dietary lipid levels was 40-145 g/kg,the lipase and alkaline phosphatase activities were stimulated by elevated levels of dietary lipid.However,the activities of hexokinase and pyruvate kinase showed opposite trend.The pepsin and intestine amylase activities were significantly(P0.01)affected by CHO∶ L ratios.The higher activity of pepsin were observed when the CHO∶ L were 2.66∶ 1 and 1.52∶ 1(P0.05).The intestine amylase activity was significantly increased(P0.01)as dietary CHO levels(156.3-360.4 g/kg)increased.Based on a second-order polynomial regression analysis of WG against dietary carbohydrate and lipid levels,growth maximum was observed when the dietary carbohydrate and lipid levels were 268.82 g/kg and 122.20 g/kg,corresponding to a CHO∶ L ratio of 2.20∶ 1.These results indicated that the utilization of dietary lipid and carbohydrate was moderate in redclaw crayfish and the preferential utilization of carbohydrate was higher than that of lipid.

Carbohydrate and lipid digestibility of animal and vegetal ingredients and diets for juvenile Australian redclaw crayfish, Cherax quadricarinatus

Carbohydrate and lipid digestibility of three vegetal and four animal ingredients, and diets in which they were included, were evaluated for juvenile Australian redclaw crayfish, Cherax quadricarinatus. The ingredients were: soy paste, textured wheat, sorghum meal, sardine meals (67% and 58% crude protein), squid meal and red crab meal. A basal diet was formulated, and then seven experimental diets were created, including 150 g kg[superscript [-]1] of each ingredient in the reference diet. Digestibility was measured in vivo, using chromic oxide as marker. A single-factor, completely randomized experimental design with three replicates per treatment was performed. Mean carbohydrate digestibility of vegetal ingredients and the corresponding diets was better than carbohydrate digestibility of animal ingredients. Sorghum meal had a carbohydrate digestibility over 94%, and the diet in which it was included over 92%. Soy paste and wheat meals also presented excellent carbohydrate digestibility (around 88% for ingredients and over 90% for diets). Mean carbohydrate digestibility of animal ingredients and their corresponding diets were very poor (from 18% to 32%) and this affected the carbohydrate digestibility of diets in which they were included (87-89%). Lipid digestibility was also better for vegetal ingredients. Soy paste and wheat meal recorded values over 93% and their diets over 94%. Sorghum lipid presented slightly lower digestibility. Some of the animal ingredients, especially red crab, had an excellent lipid digestibility (92.1%).

Effect of different dietary protein and lipid levels on growth and survival of juvenile Australian redclaw crayfish, Cherax quadricarinatus (von Martens)

This study determined the effect of different dietary protein and lipid levels on growth and survival of juvenile redclaw Cherax quadricarinatus. Nine practical test diets were formulated to contain three crude protein (CP) levels [260, 310 and 360 g kg )1 , equivalent to 225, 260 and 296 g kg )1 digestible protein (DP) respectively] at three crude lipid (CL) levels (40, 80 and 120 g kg )1 , equivalent to 38, 67 and 103 digestible lipids respectively), with digestible protein : digestible energy (DP : DE) ranging from 14.6 to 22.6 mg protein kJ g )1 . Three replicate groups of 15 crayfish (initial weight mean ± SD, 0.71 ± 0.13 g) per diet treatment were stocked in 40 L tanks, at 28 � C for 60 days. The highest mean weight, specific growth rate and biomass, with values of 7.0 g, 3.67% day )1 , and 370.2 g m )2 , respectively, were achieved by feeding a diet with P : L ¼ 310 : 80 (P < 0.05). The treatments resulted in a survival rate of 80–91%, feed conversion ratio of 1.08–1.61 and protein efficiency ratio of 2.24–3.08. Results indicated that a diet containing 270 g kg )1 DP (equivalent to 320 g kg )1 CP), 75 g kg )1 DL 1 with a DP/DE of 18.4 mg protein kJ )1 , and 0.031 g protein per animal per day was optimum for juvenile C. quadricarinatus under the tested experimental conditions.

Evaluation of practical diets containing different protein levels, with or without fish meal, for juvenile Australian red claw crayfish ( Cherax quadricarinatus)

Six practical diets containing increasing percentages of crude protein (CP) (30%, 35%, and 40%) with or without anchovy fish meal (FM) were fed to juvenile red claw crayfish (mean individual weight=1.12 g) during an 8-week feeding trial. Growth, survival, feed conversion ratio, and amino acid composition of tail-muscle meat of juvenile red claw were determined. At the conclusion of the experiment, specific growth rate (SGR) and percent survival among treatments, which averaged 3.91%/day and 80.7%, overall, were not significantly different among treatments. The percent weight gain of red claw fed a diet containing 20% fish meal and 40% crude protein was significantly higher (1352%) than that of red claw fed a diet containing 0% fish meal and 30% crude protein (828%), but not different from red claw fed all other diets. Red claw fed Diet 3 had significantly higher FCR (5.73) compared to red claw fed Diet 6 (3.03) but not different from red claw fed the other four diets. Results from this study indicate that juvenile red claw can be fed a practical diet containing 35% CP with 0% FM if a combination of less expensive plant protein ingredients (SBM, wheat, BGY, and milo) is added. CP levels can be reduced to 30% if 15% anchovy fish meal is included. Reducing CP levels and the reliance of fish meal in Australian red claw diets may help reduce operating costs and thereby increase producers profits.

Effects of feeding practical diets containing various protein levels on growth, survival, body composition, and processing traits of Australian red claw crayfish (Cherax quadricarinatus) and on pond water quality

A 117-day feeding trial was conducted in ponds with juvenile Australian red claw crayfish (Cherax quadricarinatus) to evaluate the effects on growth, survival, body composition, and processing traits when fed diets containing three different protein levels (22%, 32%, and 42%), and the effects of feeding these diets on pond water quality. Juvenile crayfish (mean weight of 4.6±2.2 g) were randomly stocked into nine 0.02-ha ponds at a rate of 500 per pond (25 000 ha−1), and each diet was fed to three ponds. There were two feedings per day, each consisting of one-half of the total daily ration. At harvest, there were no significant differences (P>0.05) in the individual weight, percentage weight gain, or specific growth rate among treatments, which averaged 75.3 g, 1535%, and 2.38% day−1 respectively. Red claw fed the 42% crude protein diet had significantly higher (P<0.05) feed conversion ratio (7.34) compared with crayfish fed diets containing 22% (5.18) or 32% (5.13) crude protein, and had significantly lower percentage survival (46.1%) compared with red claw fed diets with 22% (61.1%) or 32% (58.2%) protein. Total yield was significantly lower (P<0.05) in red claw fed the 42% protein diet (640 kg ha−1) compared with red claw fed diets containing 22% (920 kg ha−1) or 32% (904 kg ha−1) protein. Mean total ammonia nitrogen (TAN) levels were significantly higher (P<0.05) in ponds with red claw fed the 42% protein diet (0.55 mg L−1) compared with ponds with red claw fed diets containing 22% (0.32 mg L−1) or 32% (0.38 mg L−1) protein. Mean total nitrite concentrations in ponds with red claw fed the 42% protein diet was significantly higher (0.05 mg L−1) compared with red claw fed diets containing 22% (0.01 mg L−1) or 32% (0.02 mg L−1) protein. These results indicate that a practical diet containing 22% (as fed basis) protein may be adequate for pond production of red claw when stocked at the density used in this study, and that a diet containing 42% protein adversely affected levels of TAN and nitrite, possibly reducing overall survival of red claw. Use of a diet with 22% protein may allow red claw producers to reduce diet costs and thereby increase profits.

Partial and total replacement of fish meal with soybean meal and brewer's grains with yeast in practical diets for Australian red claw crayfish Cherax quadricarinatus

Three feeding studies were conducted to evaluate the effects of total replacement of fish meal (FM) with a combination of soybean meal (SBM) and brewer's grains with yeast (BGY) in diets for two separate strains of juvenile Australian red claw crayfish. In Experiment 1, three practical diets were formulated to be isonitrogenous (40% protein) and isocaloric (4.0 kcal available energy/g diet) and contained either 25%, 10%, or 0% fish meal. Variable percentages of SBM (35%, 46.8%, and 79.8%, respectively) and BGY-35 (0%, 30%, and 5%, respectively) replaced the fish meal. In Experiments 2 and 3, four practical diets were formulated to be isonitrogenous (40% protein) and isocaloric (4 kcal available energy/g diet) containing 24% or 0% fish meal. Diet 1 contained 24% fish meal, 23% SBM, and 0% BGY-35. A variable percentage of SBM (56.75%, 47.75%, and 40.75%, respectively) and BGY-35 (10%, 20%, and 30%, respectively) replaced the fish meal in the remaining three diets. In Experiment 1, after 8 weeks, juvenile red claw fed all three diets had no significant difference ( P>0.05) in final weight, percentage weight gain, or survival, which averaged 7.90 g, 3848%, and 83%, respectively. In Experiment 2, after 8 weeks, juveniles fed all four diets had no significant difference in final weight, percentage weight gain, or specific growth rate which averaged 11.46 g, 977%, and 3.08%/day, respectively. Percentage survival was not significantly different among treatments and averaged 79%. In Experiment 3, after 8 weeks, juvenile red claw fed all four diets had no significant difference in final weight, percentage weight gain, or specific growth rate which averaged 16.22 g, 457%, and 2.34%/day, respectively. Percentage survival was not significantly different among treatments and averaged 98%. These results indicate that fish meal and shrimp meal can be totally replaced with soybean meal and BGY in diets for juvenile red claw crayfish. This may allow for less expensive diets by red claw producers, which may increase profitability.

Quality Changes in Australian Red Claw Crayfish, Cherax quadricarinatus, Stored at 0°C

Shell-on tails of 70 juvenile Australian red claw crayfish, Cherax quadricarinatus, were separately packaged in seven sealed plastic freezer bags (10 in each) and stored on ice (0°C) for 0, 1, 3, 5, 7, 10, and 14 days. At the end of each storage period, raw muscle homogenate from five tails (pooled) were analyzed for lipid peroxidation, proteolysis (electrophoreis), and thermal stability (differential scanning calorime-try). The other five tails were individually cooked (2 minutes boiling) to determine cooking yield and toughness (Warner-Bratzler shear). Lipid oxidation occurred during storage (e.g., TBA values increased from 0.341 mg/kg on day 0 to 1.492 mg/kg on day 14, P< 0.05). Myofibrillar and sarcoplasmic proteins were generally resistant to proteolysis, but were destabilized during storage. Transition temperatures for myosin head and actin decreased (P# 0.05) from 50.2°C and 72.6°C on day 0, to 39.4°C and 60.3°C by day 14, respectively; while enthalpy of denatur-ation for myosin head reduced from 0.324 J/g to 0.116 J/g during this pe-riod. Storage also resulted in a gradual loss in cooking yield, which correlated (R = 20.82, P >0.05) with progressive toughening of cooked meat. The results indicate that red claw muscle is susceptible to protein denaturation and lipid oxidation, and these chemical changes may be responsible for decreased cooking yield and reduced tenderness of meat during extended refrigeration storage.

Effects of Temperature and Salinity on Weight Gain, Oxygen Consumption Rate, and Growth Efficiency in Juvenile Red‐Claw Crayfish Cherax quadricarinatus

Abstract.— Weight gain and metabolic rates, as determined by oxygen consumption rates, were examined in juvenile Australian red‐claw crayfish Cherax quadricarinatus exposed to different temperatures (16–32 C in 2 C increments) or salinities (0–30 ppt in 5 ppt increments). Mean weight gain, molting frequency, and survival (%) were dependent on temperature and salinity. In freshwater (0 ppt), maximal weight gain and molting frequency were observed at 28 C with maximal survival observed over the temperature range of 24–30 C. Metabolic rates in freshwater were temperature dependent (mean Q10= 2.44). Maximal weight gain and molting frequency were observed at salinities of 0 and 5 ppt (28 C); however, survival was reduced at salinities ≥ 5 ppt. Metabolic rates were not salinity dependent and did not differ significantly over the salinity range from 0–20 ppt. Growth efficiencies, calculated by dividing weight gain by total metabolic energy expenditure (i.e., weight gain + metabolic rate), were highest at a temperature of 20 C (0 ppt) and at salinities of 0 and 5 ppt (28 C). These data suggest that, at higher culture temperatures, maximal weight gain of red‐claw juveniles may be reduced when food resources are limited. Maximal weight gain, at optimal temperatures (28 C) with unlimited food supply, does not appear to be effected by low salinity conditions. Because of the potential commercial value of red‐claw, culturists, should be aware of the relationship between environmental condition and metabolic energy requirements to ensure maximal weight gain and survival of juveniles.

Evaluation of Several Commercial Feeds and Crustacean Reference Diet for Juvenile Australian Red Claw Crayfish,Cherax quadricarinatus

In preliminary experiments, juvenile (20 mg) Australian red claw crayfish, Cherux quadricarinatus, were fed ten commercially available diets to determine the best diets for use in recirculating systems. Of these diets, three were selected for additional trials. A second series of test diets consisted of a shrimp diet supplemented with Artemia nauplii for either one, two, or three weeks. A fourth diet combined a commercial shrimp diet and a catfish diet. Performance of each diet was compared to that of a proposed standard crustacean reference diet. After 28 days, mean final weight gains for the Artemia nauplii, shrimp diet plus two-week Artemia nauplii, and shrimp diet plus fish diet treatments (20 mg, 17 mg, 19 mg, respectively) were significantly higher (P < 0.05) than the reference diet (10 mg). The lowest survival (40%) was recorded for the shrimp diet plus fish diet treatment, while highest survival (80%) occurred using the one-week feeding of Artemia nauplii plus shrimp diet treatment. Survival in al...

Heat and oxygen flux as a function of environmental po2 in juvenile Australian crayfish, Cherax quadricarinatus

AbstractOxygen and heat flux of the juvenile Australian red claw crayfish, Cherax quadricarinatus, were measured in parallel respirometry and calorimetry systems at 28°C at varying levels of environmental po2. Juvenile crayfish maintained an average oxygen flux of 5.0 ± 0.4 (SEM) pmol O2/(s*mg fresh weight) over the po2 range from 20.7 to 5 kPa. At approximately 4 kPa po2, oxygen flux decreased, conforming to decreasing oxygen tensions. Juvenile crayfish maintained an average heat flux of −2.2 ± 0.2 μW/mg fresh weight when exposed to 100 and 50% air saturated conditions (18.1 to 20.7 and 7.8 to 10.4kPa po2, respectively). The ratio of the amount of heat dissipated per oxygen consumed, called the calorimetric/respirometric (CR) ratio, at 100 and 50% air saturated conditions averaged −440 kJ/mol O2. When crayfish were exposed to 25% air saturated conditions (2.5 to 5.2 kPa po2), heat flux decreased initially to −1.1 ± 0.4 μW/mg fresh weight. Within 4 hr, however, heat flux returned to normoxic values. When crayfish were exposed to anoxic conditions, heat flux decreased to zero. Most juvenile crayfish did not survive short‐term (1–2 hr) anoxic stress. These data suggest that juvenile C. quadricarinatus are excellent oxygen regulators over a wide range of environmental po2. These data indicate also that juvenile C. quadricarinatus can compensate metabolically, possibly via aerobic and/or anaerobic adjustments, in order to maintain metabolic rate at critically low po2. Last, this crayfish appears limited in its ability to utilize anaerobic pathways to maintain metabolic rate in anoxic environments. © Wiley‐Liss, Inc.