Comp. Biochem. Physiol., 1975, Vol. SlA, pp. 151 to 153. Pergamon Press. Printed in Great Britain
SEASONAL
CHANGES IN HEMATOLOGY OF RAINBOW TROUT, SALMO GAIRDNERP
JOAN E. DENTING AND M. K. YOUSEF Department of Biological Sciences, University of Nevada, Las Vegas, Nevada 89109 and Laboratory of Environmental
Patho-Physiology,
Desert Research Institute, University of Nevada, Boulder City, Nevada 89005, U.S.A. (Received
11 February 1974)
Abstract-l, A study on hematology of rainbow trout was conducted to test whether or not seasonal changes are due to changes in water temperature. 2. Although water temperature was maintained about the same throughout the study, seasonal changes were evident in hemoglobin, hematocrit, serum protein, mean cell volume, mean cell hemoglobin and mean cell hemoglobin concentration. 3. In conclusion, water temperature does not seem to be responsible for variations in hematology of rainbow trout. Diet, metabolic adaptations and activity are suggested as probable causes of seasonal
INTRODUCTION
HEMATOL~C~CAL values in rainbow trout have been shown to be influenced by age and season. Bamhart (1969) observed that red blood cell (BBC) counts, hematocrit (Hct), hemoglobin (Hb) and sedimentation rate are highly correlated to age. During the tirst 3 years of life, Hb increased in trout (Zubina, 1966; Aider, 1970); also, serum protein (SP) increased with age and exhibited seasonal fluctuations corresponding to gonadal development (Sano, 1960). Seasonal variations in hematological characteristics have been observed in trout. Aider (1970) reported that in immature 2-year-old trout, Hb was highest at the beginning of the year and lowest at the end of the year. Haider (1971) noted that a maximum concentration of SP in trout occurred in February and March while the lowest concentration occurred in July and August. Similar seasonal variation has also been reported in other fishes. The Hb and Hct values of carp (Qprinus curpio) were lower in winter than spring and the mean cell hemoglobin concentration (MCHC) was higher in winter than in spring (Murachi, 1959). Preston (1960) reported that in the plaice (Pleuronectes plutessu L.), hemodilution occurred in late summer and winter and hemoconcentration was evident in late spring and early summer. It was suggested that these changes were attributed to a change in water temperature. As water temperature decreased, hemodilution occurred and as water temperature increased, hemoconcentration resulted. * Supported in part by NSF grant GB-25381. 7 P&&t address: Institute -of Environmental Stress, University of California. Santa Barbara. California 93106. -
In the following report, this suggestion was tested by investigating the effect of season on some hematological parameters of l-year-old rainbow trout kept at a constant water temperature throughout the year.
MATERIALS AND METHODS Rainbow trout, Salmo gairdneri, were obtained from Willow Beach National Fish Hatchery, Willow Beach, Arizona. The age of the trout varied from 11 to 14 months. The experimental period extended from March 1972 to January 1973, where water temperature remained constant at 11-13°C. Five to seven trout were captured each month throughout the study period. Each trout was anaesthetixed in a 0.1 g/l. concentration of MS 222
(tricaine methanesulfonate). Blood was drawn by cardiac puncture through the pectoral girdle with a 27G hypodermic needle and a 1 ems tuberculin heparinized syringe. Any sample less than 0.1 ml was discarded. Then the trout were weighed and the body length was measured. The differential stain used for blood cell measurements was processed immediately, Hb was determined within 6 hr and all other tests were completed within 24 hr after withdrawal of blood. Each sample was analyzed in duplicate. The concentration of Hb in g/lOOml was measured using the cyanethemoglobin method and the Fisher Flo-Thru Hemophotometer. Hct was determined using precalibrated, 75 mm heparinized tubes and an Adams Readacrit Centrifuge. The concentration of SP was measured using an American Optical Total Solids No. 10400 Refractometer. Differential stain and RBC count were made using standard methods (Hepler, 1966). The length and width of erythrocytes, lymphocytes and platelets were determined by using an ocular micrometer and by counting ten different cells for each type. The mean cell volume (MCV), mean cell hemoglobin (MCH) 151
152
JOAN E. DENTON AM, M. K. YOUSEF
and mean cell hemoglobin concentration (MCHC) were calculated using standard formulas (Hepler, 1966):
MCV (c(cLp)= (Hb, g) (lO)/(RBC x 10% MCH (cp) = (Hct) (lO)/(RBC x 103, MCHC (%) = (Hb, g)/Hct . RESULTS
Data on body weight, length and blood hematology of rainbow trout throughout the experimental period are summarized in Table 1. Although the age of trout ranged between 11 and 13 months, body weight and length varied from 80 to 164 g and 18 to 24 cm, respectively. The trout used for each month’s analyses were captured randomly. Although water temperature was maintained between 11 and 13”C, there was some evidence of seasonal changes in Hb, Hct and SP. Values in winter (November-January) and summer (JuneAugust) were rather similar but higher than values obtained in March-April. The lowest values in Hb, Hct and SP were obtained in March and the highest values were in January for Hb and Hct and in July for SP. Also, since diet was approximately the same during this study, it is suggested that these seasonal changes in Hct, Hb and SP are related to factors other than diet. Mean corpuscular volume (MCV) was high in July as 393.2 CCL and low in March as 192.1 cp. Mean cell hemoglobin (MCH) was higher in January as 62.4 ppg than in March as 35.3 ppg. Mean cell hemoglobin concentration (MCHC) was high in April as 18.9% and low in July as 14.2%. It is interesting to note that MCHC values on trout are less than one-half of the value reported on mammals. Also the RBC count is only about one-third of the value reported on mammals. The low MCHC may be related to the fact that the rate of oxygen consump-
tion of trout is much lower than that of mammals. The low RBC count and the high Hct were shown to be related to the size of the RBC in several species of fish (Smith et al., 1952), therefore we studied the size of the blood cells of rainbow trout. The dry red blood cells measured an average of 13.3 p long and 9.5 p wide and thrombocytes measured 14.6 p long and 4.0 p wide. Lymphocytes and monocytes measured 57 and 10.2 p in diameter, respectively. Thus, the low RBC count is related to the large size of the RBC as previously reported. DISCUSSION
The range of Hb in our data (Table 1) was similar to reported values for trout by DeWilde & Houston (1967); Love (1970). The wide range reported for Hb may be due to the different techniques used by different investigators. In this study, Hct ranged from 34.8 to 56.9% (Table 1) which is slightly higher than values reported by others (Field et al., 1943; Schiffman &Fromm, 1959; Sniezko, 1960; McCarthy et al., 1973). The discrepancy between thevarious values reported represent the use of different methods and may be related to effects of age, diet and season. Seasonal fluctuations were evident for Hb and Hct. The highest values were found in January and the lowest in March. DeWilde & Houston (1967) found that Hct and Hb increased in fall and winter but decreased in summer. Aider (1970) found that Hb and Hct values were high in January-February and low in October-November. In other species of fish seasonal variations have been found in Hct and Hb (Murachi, 1959; Preston, 1960). Preston (1960) credited seasonal fluctuations to changes in ‘water temperature although water temperature was not measured during his study. Since water temperature varied only 2°C throughout the year in our study, it
Table 1. Seasonal changes in hematology of l-year-old rainbow trout
N
X$E. 5 -
24.2 f. 0.8
Length (4 Weight (9) Hemoglobin (g/100 ml)
6
164.3 +
16.4
9-s+ 0.2 56.9 + Hct (%) 1.5 1.5t_ RBC (millions/n-&) 0.1 Plasma protein (g/100 ml) 3*9rf: 0.2 MCV (cp) 3734 MCH hg) 624 MCHC (“/,) 16.7
18.0+ 1.4 83.0+ 5.2 6.4+ 0.5 34.8 + 1.6 1.8+ 0.1 2.9+ 0.3 192.1 35.3 18.4
X, Mean; S.E., Standard error.
Apr. Bf. S.E. 6
May 8+ S.E.
19.85 0.6 81.3rf: 9.3 8-O& 0.3 42.3+ 1.6 1*5t 0.1 3*5+ 0.1 281.1 53.2 18.9
20.7 + 0.6 947+ 5.9 7.9+ 0.2 51.9+ 1.2 1.6? 0.1 4.55 0.2 316.3 48.1 15.2
I
June x+ S.E. 6
July ;9+ S.E. 6
Aug. 8+ S.E. 5
81i, SE.
19.6-+ 0.5 80.2 + 3.6 7*1* 0.1 45.2+ 1.5 1.4* 0-l 4.75 0.3 321.5 50.5 15.7
23.4+ 0.7 141.3 + 13.3 7.7 ? 0.2 543 + 1.4 1.4+ 0.1 5.1+ 0.3 393.2 55.8 14.2
22.4 + 0.8 119.6k 12.0 8.6? 0.1 56.4+ 2.8 1.5+ 0.1 4.2+ 0.3 389.2 59.4 15.2
21.1& 0.6 104*0& 6.8 8.5+ 0.3 52.6 + 4.6 1.4* 0.1 4.65 3.2 376.0 60.8 16.2
5
Seasonal changes in hematology of rainbow trout is unlikely that seasonal variations in Hct and Hb are due to temperature changes and may represent differences in activity and metabolic adaptations. The MCH values shown in Table 1 are well within the range reported by other workers (Field et al., 1943; McCarthy et al.,. 1973) but MCHC in this study was lower than has been reported. Our data indicate that seasonal changes in MCH and MCHC are not associated with water temperature. This conclusion contradicts data reported by DeWilde & Houston (1967) who observed that as water temperature increased, there were higher levels of Hb and MCHC. MCV ranged from 192 to 393 CCLand the highest values were found in July while the lowest values were found in March. This is a wider range than reported by Field et al. (1943) and McCarthy et al. (1973). The wide range in our data is probably due to seasonal variation not associated with water temperature and also may be related to variation in RBC count. A similar seasonal effect of MCV was reported by DeWilde & Houston (1967). The highest values of SP were found in July and the lowest in March. On the contrary, Haider (1971) found the maximum plasma protein concentration to be in February and March and the minimum in July and August. This apparent discrepancy of seasonal effects on SP is probably due to differences in the strain of trout, type of management and diet. In conclusion, under our experimental conditions seasonal changes in hematology of rainbow trout are not related to water temperature or diet. It is suggested that these seasonal changes are probably related to degree of activity and to metabolic adaptations. Acknowledgements-The authors wish to thank the US. Fish and Wildlife Service and the Willow Beach National Fish Hatchery, Willow Beach, Arizona, for the use of their facilities and for providing the rainbow trout used in this study. REFERENCES
AIDER G. (1970) Hematological observations on rainbow trout (Salmo gairdneri Rich.)--I. Changes of the hemoglobin level caused by age and season. Zool. Anz. 185, 36-46.
153
BARNHARTR. A. (1969) Effects of certain variables on haematological characteristics of rainbow trout. Trans. Am. Fish. Sot. 98,411-418.
DEWILDEM. A. & HOUSTON A. H. (1967) Haematological aspects of the thermoacchmatory process in the rainbow trout, Salmo gairdneri. J. Fish. Res. Bd Can. 2267-2281. FOLD J. B., ELVEHJEMC. A. & JUDAYC. (1943) A study of the blood constituents of carp and trout. J. biol. Chem. 148,261-269. HAIDERG. (1971) Changes related to age and season in the serum protein of rainbow trout (Salmo gairdneri Rich.). 2. Fisch Hirfswiss l&107-124. HEPLER 0. E. (1966) Manual of Clinical Laboratory Methodr. Thomas, Springtield, Ill. Love R. M. (1970) The Chemical Biology of Fishes. Academic Press, New York. MCCARTHYD. H., STEVENSON J. P. & ROBERTSM. S. (1973) Some blood parameters of the rainbow trout (Salmo gairdneri Richardson). J. Fish Biol. 5, 1-8. MURACHI, S. (1959) Hemoglobin content, erythrocyte
sedimentation rate and hematocrit of the blood in young carp (Cyprinus carpio), J. Fat. Fish. Anim. Hub. Hiroshima Univ. 2,241~247. F’RMTON A. (1960) Red blood values in the plaice (Pleuro-
nectesplatessa L.). J. mar. Biol. Ass. U.K. 39, 681-687. studies of the culture fishes in Japan-2. Seasonal variation of the blood constituents of rainbow trout. J. Tokyo Univ. Fish. 46, 67-75. SCHIFFMAN R. H. & FROMMP. 0. (1959) Measurement of some physiological parameters in rainbow trout (Salmo gairdneri). Can. J. Zool. 37,25-32. SMITH C.-G., LEWIS W. M. & KAPLAN H. M. (1952) Comparative morphologic and physiologic study of fish blood. Prog. Fish-Cult. 14, 169-172. SNIEZKOS. F. (1960) Microhematocrit as a tool in fishery research and management. In USDI Fish and Wildlife Service Special Sci&tific Report. Fish. 341, pp. l-15. ZUFIINAN. F. (1966) Variation with age of blood volume and hemoglobin level in hatchery reared rainbow trout. In Tezisy dokladov Vsesoyusnogo soveshchaniva po ekologii ijiziologii ryb, pp. 92-93. Moscow. SANO T. (1960) Haematological
Key Word Index-Water temperature; hematocrit ; hemoglobin; serum protein; mean cell volume; mean cell hemoglobin; mean cell hemoglobin concentration; size of red blood cell; lymphocytes; platelets; rainbow trout; Salmo gairdneri.
SEASONAL
CHANGES IN HEMATOLOGY OF RAINBOW TROUT, SALMO GAIRDNERP
JOAN E. DENTING AND M. K. YOUSEF Department of Biological Sciences, University of Nevada, Las Vegas, Nevada 89109 and Laboratory of Environmental
Patho-Physiology,
Desert Research Institute, University of Nevada, Boulder City, Nevada 89005, U.S.A. (Received
11 February 1974)
Abstract-l, A study on hematology of rainbow trout was conducted to test whether or not seasonal changes are due to changes in water temperature. 2. Although water temperature was maintained about the same throughout the study, seasonal changes were evident in hemoglobin, hematocrit, serum protein, mean cell volume, mean cell hemoglobin and mean cell hemoglobin concentration. 3. In conclusion, water temperature does not seem to be responsible for variations in hematology of rainbow trout. Diet, metabolic adaptations and activity are suggested as probable causes of seasonal
INTRODUCTION
HEMATOL~C~CAL values in rainbow trout have been shown to be influenced by age and season. Bamhart (1969) observed that red blood cell (BBC) counts, hematocrit (Hct), hemoglobin (Hb) and sedimentation rate are highly correlated to age. During the tirst 3 years of life, Hb increased in trout (Zubina, 1966; Aider, 1970); also, serum protein (SP) increased with age and exhibited seasonal fluctuations corresponding to gonadal development (Sano, 1960). Seasonal variations in hematological characteristics have been observed in trout. Aider (1970) reported that in immature 2-year-old trout, Hb was highest at the beginning of the year and lowest at the end of the year. Haider (1971) noted that a maximum concentration of SP in trout occurred in February and March while the lowest concentration occurred in July and August. Similar seasonal variation has also been reported in other fishes. The Hb and Hct values of carp (Qprinus curpio) were lower in winter than spring and the mean cell hemoglobin concentration (MCHC) was higher in winter than in spring (Murachi, 1959). Preston (1960) reported that in the plaice (Pleuronectes plutessu L.), hemodilution occurred in late summer and winter and hemoconcentration was evident in late spring and early summer. It was suggested that these changes were attributed to a change in water temperature. As water temperature decreased, hemodilution occurred and as water temperature increased, hemoconcentration resulted. * Supported in part by NSF grant GB-25381. 7 P&&t address: Institute -of Environmental Stress, University of California. Santa Barbara. California 93106. -
In the following report, this suggestion was tested by investigating the effect of season on some hematological parameters of l-year-old rainbow trout kept at a constant water temperature throughout the year.
MATERIALS AND METHODS Rainbow trout, Salmo gairdneri, were obtained from Willow Beach National Fish Hatchery, Willow Beach, Arizona. The age of the trout varied from 11 to 14 months. The experimental period extended from March 1972 to January 1973, where water temperature remained constant at 11-13°C. Five to seven trout were captured each month throughout the study period. Each trout was anaesthetixed in a 0.1 g/l. concentration of MS 222
(tricaine methanesulfonate). Blood was drawn by cardiac puncture through the pectoral girdle with a 27G hypodermic needle and a 1 ems tuberculin heparinized syringe. Any sample less than 0.1 ml was discarded. Then the trout were weighed and the body length was measured. The differential stain used for blood cell measurements was processed immediately, Hb was determined within 6 hr and all other tests were completed within 24 hr after withdrawal of blood. Each sample was analyzed in duplicate. The concentration of Hb in g/lOOml was measured using the cyanethemoglobin method and the Fisher Flo-Thru Hemophotometer. Hct was determined using precalibrated, 75 mm heparinized tubes and an Adams Readacrit Centrifuge. The concentration of SP was measured using an American Optical Total Solids No. 10400 Refractometer. Differential stain and RBC count were made using standard methods (Hepler, 1966). The length and width of erythrocytes, lymphocytes and platelets were determined by using an ocular micrometer and by counting ten different cells for each type. The mean cell volume (MCV), mean cell hemoglobin (MCH) 151
152
JOAN E. DENTON AM, M. K. YOUSEF
and mean cell hemoglobin concentration (MCHC) were calculated using standard formulas (Hepler, 1966):
MCV (c(cLp)= (Hb, g) (lO)/(RBC x 10% MCH (cp) = (Hct) (lO)/(RBC x 103, MCHC (%) = (Hb, g)/Hct . RESULTS
Data on body weight, length and blood hematology of rainbow trout throughout the experimental period are summarized in Table 1. Although the age of trout ranged between 11 and 13 months, body weight and length varied from 80 to 164 g and 18 to 24 cm, respectively. The trout used for each month’s analyses were captured randomly. Although water temperature was maintained between 11 and 13”C, there was some evidence of seasonal changes in Hb, Hct and SP. Values in winter (November-January) and summer (JuneAugust) were rather similar but higher than values obtained in March-April. The lowest values in Hb, Hct and SP were obtained in March and the highest values were in January for Hb and Hct and in July for SP. Also, since diet was approximately the same during this study, it is suggested that these seasonal changes in Hct, Hb and SP are related to factors other than diet. Mean corpuscular volume (MCV) was high in July as 393.2 CCL and low in March as 192.1 cp. Mean cell hemoglobin (MCH) was higher in January as 62.4 ppg than in March as 35.3 ppg. Mean cell hemoglobin concentration (MCHC) was high in April as 18.9% and low in July as 14.2%. It is interesting to note that MCHC values on trout are less than one-half of the value reported on mammals. Also the RBC count is only about one-third of the value reported on mammals. The low MCHC may be related to the fact that the rate of oxygen consump-
tion of trout is much lower than that of mammals. The low RBC count and the high Hct were shown to be related to the size of the RBC in several species of fish (Smith et al., 1952), therefore we studied the size of the blood cells of rainbow trout. The dry red blood cells measured an average of 13.3 p long and 9.5 p wide and thrombocytes measured 14.6 p long and 4.0 p wide. Lymphocytes and monocytes measured 57 and 10.2 p in diameter, respectively. Thus, the low RBC count is related to the large size of the RBC as previously reported. DISCUSSION
The range of Hb in our data (Table 1) was similar to reported values for trout by DeWilde & Houston (1967); Love (1970). The wide range reported for Hb may be due to the different techniques used by different investigators. In this study, Hct ranged from 34.8 to 56.9% (Table 1) which is slightly higher than values reported by others (Field et al., 1943; Schiffman &Fromm, 1959; Sniezko, 1960; McCarthy et al., 1973). The discrepancy between thevarious values reported represent the use of different methods and may be related to effects of age, diet and season. Seasonal fluctuations were evident for Hb and Hct. The highest values were found in January and the lowest in March. DeWilde & Houston (1967) found that Hct and Hb increased in fall and winter but decreased in summer. Aider (1970) found that Hb and Hct values were high in January-February and low in October-November. In other species of fish seasonal variations have been found in Hct and Hb (Murachi, 1959; Preston, 1960). Preston (1960) credited seasonal fluctuations to changes in ‘water temperature although water temperature was not measured during his study. Since water temperature varied only 2°C throughout the year in our study, it
Table 1. Seasonal changes in hematology of l-year-old rainbow trout
N
X$E. 5 -
24.2 f. 0.8
Length (4 Weight (9) Hemoglobin (g/100 ml)
6
164.3 +
16.4
9-s+ 0.2 56.9 + Hct (%) 1.5 1.5t_ RBC (millions/n-&) 0.1 Plasma protein (g/100 ml) 3*9rf: 0.2 MCV (cp) 3734 MCH hg) 624 MCHC (“/,) 16.7
18.0+ 1.4 83.0+ 5.2 6.4+ 0.5 34.8 + 1.6 1.8+ 0.1 2.9+ 0.3 192.1 35.3 18.4
X, Mean; S.E., Standard error.
Apr. Bf. S.E. 6
May 8+ S.E.
19.85 0.6 81.3rf: 9.3 8-O& 0.3 42.3+ 1.6 1*5t 0.1 3*5+ 0.1 281.1 53.2 18.9
20.7 + 0.6 947+ 5.9 7.9+ 0.2 51.9+ 1.2 1.6? 0.1 4.55 0.2 316.3 48.1 15.2
I
June x+ S.E. 6
July ;9+ S.E. 6
Aug. 8+ S.E. 5
81i, SE.
19.6-+ 0.5 80.2 + 3.6 7*1* 0.1 45.2+ 1.5 1.4* 0-l 4.75 0.3 321.5 50.5 15.7
23.4+ 0.7 141.3 + 13.3 7.7 ? 0.2 543 + 1.4 1.4+ 0.1 5.1+ 0.3 393.2 55.8 14.2
22.4 + 0.8 119.6k 12.0 8.6? 0.1 56.4+ 2.8 1.5+ 0.1 4.2+ 0.3 389.2 59.4 15.2
21.1& 0.6 104*0& 6.8 8.5+ 0.3 52.6 + 4.6 1.4* 0.1 4.65 3.2 376.0 60.8 16.2
5
Seasonal changes in hematology of rainbow trout is unlikely that seasonal variations in Hct and Hb are due to temperature changes and may represent differences in activity and metabolic adaptations. The MCH values shown in Table 1 are well within the range reported by other workers (Field et al., 1943; McCarthy et al.,. 1973) but MCHC in this study was lower than has been reported. Our data indicate that seasonal changes in MCH and MCHC are not associated with water temperature. This conclusion contradicts data reported by DeWilde & Houston (1967) who observed that as water temperature increased, there were higher levels of Hb and MCHC. MCV ranged from 192 to 393 CCLand the highest values were found in July while the lowest values were found in March. This is a wider range than reported by Field et al. (1943) and McCarthy et al. (1973). The wide range in our data is probably due to seasonal variation not associated with water temperature and also may be related to variation in RBC count. A similar seasonal effect of MCV was reported by DeWilde & Houston (1967). The highest values of SP were found in July and the lowest in March. On the contrary, Haider (1971) found the maximum plasma protein concentration to be in February and March and the minimum in July and August. This apparent discrepancy of seasonal effects on SP is probably due to differences in the strain of trout, type of management and diet. In conclusion, under our experimental conditions seasonal changes in hematology of rainbow trout are not related to water temperature or diet. It is suggested that these seasonal changes are probably related to degree of activity and to metabolic adaptations. Acknowledgements-The authors wish to thank the US. Fish and Wildlife Service and the Willow Beach National Fish Hatchery, Willow Beach, Arizona, for the use of their facilities and for providing the rainbow trout used in this study. REFERENCES
AIDER G. (1970) Hematological observations on rainbow trout (Salmo gairdneri Rich.)--I. Changes of the hemoglobin level caused by age and season. Zool. Anz. 185, 36-46.
153
BARNHARTR. A. (1969) Effects of certain variables on haematological characteristics of rainbow trout. Trans. Am. Fish. Sot. 98,411-418.
DEWILDEM. A. & HOUSTON A. H. (1967) Haematological aspects of the thermoacchmatory process in the rainbow trout, Salmo gairdneri. J. Fish. Res. Bd Can. 2267-2281. FOLD J. B., ELVEHJEMC. A. & JUDAYC. (1943) A study of the blood constituents of carp and trout. J. biol. Chem. 148,261-269. HAIDERG. (1971) Changes related to age and season in the serum protein of rainbow trout (Salmo gairdneri Rich.). 2. Fisch Hirfswiss l&107-124. HEPLER 0. E. (1966) Manual of Clinical Laboratory Methodr. Thomas, Springtield, Ill. Love R. M. (1970) The Chemical Biology of Fishes. Academic Press, New York. MCCARTHYD. H., STEVENSON J. P. & ROBERTSM. S. (1973) Some blood parameters of the rainbow trout (Salmo gairdneri Richardson). J. Fish Biol. 5, 1-8. MURACHI, S. (1959) Hemoglobin content, erythrocyte
sedimentation rate and hematocrit of the blood in young carp (Cyprinus carpio), J. Fat. Fish. Anim. Hub. Hiroshima Univ. 2,241~247. F’RMTON A. (1960) Red blood values in the plaice (Pleuro-
nectesplatessa L.). J. mar. Biol. Ass. U.K. 39, 681-687. studies of the culture fishes in Japan-2. Seasonal variation of the blood constituents of rainbow trout. J. Tokyo Univ. Fish. 46, 67-75. SCHIFFMAN R. H. & FROMMP. 0. (1959) Measurement of some physiological parameters in rainbow trout (Salmo gairdneri). Can. J. Zool. 37,25-32. SMITH C.-G., LEWIS W. M. & KAPLAN H. M. (1952) Comparative morphologic and physiologic study of fish blood. Prog. Fish-Cult. 14, 169-172. SNIEZKOS. F. (1960) Microhematocrit as a tool in fishery research and management. In USDI Fish and Wildlife Service Special Sci&tific Report. Fish. 341, pp. l-15. ZUFIINAN. F. (1966) Variation with age of blood volume and hemoglobin level in hatchery reared rainbow trout. In Tezisy dokladov Vsesoyusnogo soveshchaniva po ekologii ijiziologii ryb, pp. 92-93. Moscow. SANO T. (1960) Haematological
Key Word Index-Water temperature; hematocrit ; hemoglobin; serum protein; mean cell volume; mean cell hemoglobin; mean cell hemoglobin concentration; size of red blood cell; lymphocytes; platelets; rainbow trout; Salmo gairdneri.
