Search

Search Results

• 21. [Article] Laboratory studies on the food consumption, growth, and activity of juvenile coho salmon

  Citation × Citation Citation Abstract Copy Title: Laboratory studies on the food consumption, growth, and activity of juvenile coho salmon Author: Carline, Robert F. Title: Laboratory studies on the food consumption, growth, and activity of juvenile coho salmon Author: Carline, Robert F. Close

• 22. [Article] Influence of temperature on energy and material utilization by juvenile coho salmon

  Citation × Citation Citation Abstract Copy Title: Influence of temperature on energy and material utilization by juvenile coho salmon Author: Averett, R. C. Title: Influence of temperature on energy and material utilization by juvenile coho salmon Author: Averett, R. C. Close

• 23. [Article] The influence of dissolved oxygen concentration on the swimming performance of juvenile coho salmon at different temperatures

  Citation × Citation Citation Abstract Copy Title: The influence of dissolved oxygen concentration on the swimming performance of juvenile coho salmon at different temperatures Author: Davis, Gerald E. Title: The influence of dissolved oxygen concentration on the swimming performance of juvenile coho salmon at different temperatures Author: Davis, Gerald E. Close

• 24. [Article] Effects of inbreeding Coho salmon (oncorhynchus kisutch)

  Effects of inbreeding coho salmon (Oncorhynchus kisutch) on survival during early life history, growth, feed efficiency, and resistance to gas bubble disease were studied. No effect of inbreeding could ...

  Citation × Citation Citation Abstract Copy Title: Effects of inbreeding Coho salmon (oncorhynchus kisutch) Author: Solazzi, M. F. (Mario Frank) Effects of inbreeding coho salmon (Oncorhynchus kisutch) on survival during early life history, growth, feed efficiency, and resistance to gas bubble disease were studied. No effect of inbreeding could be associated with either F=0.25 or F=0.125. Tetraploidy may help explain the absence of inbreeding depression at these levels. Title: Effects of inbreeding Coho salmon (oncorhynchus kisutch) Author: Solazzi, M. F. (Mario Frank) Effects of inbreeding coho salmon (Oncorhynchus kisutch) on survival during early life history, growth, feed efficiency, and resistance to gas bubble disease were studied. No effect of inbreeding could be associated with either F=0.25 or F=0.125. Tetraploidy may help explain the absence of inbreeding depression at these levels. Close

• 25. [Article] Factors affecting coho salmon production in Oregon

  Eight scale characters of known hatchery and wild coho salmon (Oncorhynchus kisutch) were compared, and a linear discriminant function was used to determine if hatchery and wild adult coho salmon could ...

  Citation × Citation Citation Abstract Copy Title: Factors affecting coho salmon production in Oregon Author: Scarnecchia, Dennis Leslie Eight scale characters of known hatchery and wild coho salmon (Oncorhynchus kisutch) were compared, and a linear discriminant function was used to determine if hatchery and wild adult coho salmon could be correctly identified by their scales. Eighty-two percent of the hatchery and 89% of the wild fish were correctly identified. Based on analysis of scales from adult salmon of unknown origin (hatchery or wild) and the estimated catch of hatchery coho (marked) taken by the Oregon sport fishery, concluded that 74.9% of the fish caught in the ocean from mid-June to mid-September 1977 had been released as smelts from hatcheries. Percentages of hatchery fish in the catch ranged from 85% near the mouth of the Columbia River to 61% at Winchester Bay on the southern Oregon coast. Fisheries on the south and central Oregon coast may have fished on higher percentages of wild coho salmon later in the season, probably because wild fish from coastal streams remained off of these ports while most fish destined for Columbia River hatcheries had already migrated northward. Scales from coho salmon were used to determine if location on the body from which they were taken would affect the values of five scale characters. Scales obtained from within a relatively small area above the lateral line between the dorsal and adipose fins differed widely in total radius, in radius of the freshwater zone, and in number of circuli in the freshwater zone. Scales taken farther above the lateral line had significantly lower values for all five characters observed. I conclude that substantial error can be introduced into interpretation of scale data if care is not taken to insure that scales from each fish come from precisely the same area of the body. A well chosen scrape sample yielded a result as satisfactory as that of a "preferred" or "key" scale. To investigate the relationship between streamflow and abundance of coho salmon, I correlated flow from several Oregon coastal rivers with catch of coho salmon from these rivers and with catch from the Oregon commercial troll fishery. I found a highly significant relationship between total streamflows during the freshwater residency of the fish for five Oregon coastal rivers combined and pounds of adult coho salmon caught by the Oregon commercial troll fishery from 1942 to 1962. There is also a significant relationship between total combined annual (January-December) flows for these rivers and a catch 2 years later. Conversely, I found a poor relationship between the lowest 60 consecutive days of summer flow and 2 two years later. I also found significant relationships between annual flows and catch in Tillamook Bay from 1934 to 1946. Only on the Siletz River from 1927 to 1940 do find a significant relationship between summer flows and catch. Higher flows during the freshwater stages of coho salmon probably provide more habitat and better conditions for growth as well as lessen susceptibility of fry and smelts to predation. I concluded that the relationships I found should probably not be used now to predict abundance of wild coho salmon because of (l) the unknown interaction between wild and hatchery fish, and (2) the preponderance of hatchery fish in the catch. Title: Factors affecting coho salmon production in Oregon Author: Scarnecchia, Dennis Leslie Eight scale characters of known hatchery and wild coho salmon (Oncorhynchus kisutch) were compared, and a linear discriminant function was used to determine if hatchery and wild adult coho salmon could be correctly identified by their scales. Eighty-two percent of the hatchery and 89% of the wild fish were correctly identified. Based on analysis of scales from adult salmon of unknown origin (hatchery or wild) and the estimated catch of hatchery coho (marked) taken by the Oregon sport fishery, concluded that 74.9% of the fish caught in the ocean from mid-June to mid-September 1977 had been released as smelts from hatcheries. Percentages of hatchery fish in the catch ranged from 85% near the mouth of the Columbia River to 61% at Winchester Bay on the southern Oregon coast. Fisheries on the south and central Oregon coast may have fished on higher percentages of wild coho salmon later in the season, probably because wild fish from coastal streams remained off of these ports while most fish destined for Columbia River hatcheries had already migrated northward. Scales from coho salmon were used to determine if location on the body from which they were taken would affect the values of five scale characters. Scales obtained from within a relatively small area above the lateral line between the dorsal and adipose fins differed widely in total radius, in radius of the freshwater zone, and in number of circuli in the freshwater zone. Scales taken farther above the lateral line had significantly lower values for all five characters observed. I conclude that substantial error can be introduced into interpretation of scale data if care is not taken to insure that scales from each fish come from precisely the same area of the body. A well chosen scrape sample yielded a result as satisfactory as that of a "preferred" or "key" scale. To investigate the relationship between streamflow and abundance of coho salmon, I correlated flow from several Oregon coastal rivers with catch of coho salmon from these rivers and with catch from the Oregon commercial troll fishery. I found a highly significant relationship between total streamflows during the freshwater residency of the fish for five Oregon coastal rivers combined and pounds of adult coho salmon caught by the Oregon commercial troll fishery from 1942 to 1962. There is also a significant relationship between total combined annual (January-December) flows for these rivers and a catch 2 years later. Conversely, I found a poor relationship between the lowest 60 consecutive days of summer flow and 2 two years later. I also found significant relationships between annual flows and catch in Tillamook Bay from 1934 to 1946. Only on the Siletz River from 1927 to 1940 do find a significant relationship between summer flows and catch. Higher flows during the freshwater stages of coho salmon probably provide more habitat and better conditions for growth as well as lessen susceptibility of fry and smelts to predation. I concluded that the relationships I found should probably not be used now to predict abundance of wild coho salmon because of (l) the unknown interaction between wild and hatchery fish, and (2) the preponderance of hatchery fish in the catch. Close

• 26. [Article] Hormonal and osmoregulatory aspects of smoltification in coho salmon, Oncorhynchus kisutch

  Coho salmon smolts (Oncorhynchus kisutch) were transported at low and high densities. (12 and 120 g/L) for short and long periods (4 and 12 h). Because smolts can be transplanted directly to seawater, ...

  Citation × Citation Citation Abstract Copy Title: Hormonal and osmoregulatory aspects of smoltification in coho salmon, Oncorhynchus kisutch Author: Specker, Jennifer Lee Coho salmon smolts (Oncorhynchus kisutch) were transported at low and high densities. (12 and 120 g/L) for short and long periods (4 and 12 h). Because smolts can be transplanted directly to seawater, half of the fish in each treatment were transported to tanks containing seawater and half to tanks containing freshwater. Plasma corticosteroids and glucose were elevated at unloading in all groups. Corticosteroids were still above the resting levels 24 h later, whereas glucose had returned to basal levels at this time. Potential smoltification indicators such as plasma thyroxin concentration and gill Na-K-ATPase activity were not affected by transportation. Increased corticosteroids were correlated to increased mortality in transported salmon compared to acclimated control fish when subjected to a bioassay of stress severe confinement. It is concluded that transportation induced stress in the fish regardless of hauling regimen, that increased corticosteroids may have potential as indicators of reduced performance capacity, that the greatest stress occurred during loading and the first few hours en route, and that transported coho salmon smolts seem to be equally fit for entry into freshwater or seawater. Hormones of the hypothalamic-pituitary system probably mediate the environmental changes and endogenous rhythms that regulate the timing and physiological alterations of smoltification. Because thyroid hyperactivity is a major endocrine component of smoltification, yearling coho salmon were injected with mammalian prolactin (PRL) and thyrotropin (TSH) to determine their effect on plasma thyroxin concentrations. The response of plasma thyroxin to TSH is similar from January through May in coho salmon, suggesting that the thyroid does not change in sensitivity to TSH. A dose of 0.04 to 0.07 I.U. TSH is the minimum dose sufficient to significantly increase plasma thyroxin concentration. PRL (1 to 9 I.U.) depressed plasma thyroxin levels in coho salmon parr, smolts, and post-smolts. Increased plasma thyroxin and gill Na-K-ATPase levels tentatively are considered indicative of smoltification, migratory readiness, and hence, seawater adaptability. In an experiment to consider a methodology which could be implemented at a culture facility to enhance the survival of ocean-going smolts and perhaps mitigate losses due to stunting, an abnormality of smoltification, coho salmon parr were maintained for 3 wk in water supplemented with sodium or calcium salts. Prolonged residence in sodium - supplemented freshwater increased plasma thyroxin levels and tended to elevate gill Na-K-ATPase activity. In contrast, acute exposure (24 h) to 75% seawater halved plasma thyroxin levels in coho salmon parr. Gradual acclimation to increased ambient salinity may accelerate changes in, or enhance, plasma thyroxin levels and gill Na-K-ATPase activity, and thus potentially improve the growth and survival of outmigrating smolts and reduce losses due to stunting. Plasma corticosteroid levels were determined during smoltification and in response to mammalian PRL and TSH. The interrenal tissue, which synthesizes corticosteroids, becomes hyperactive during smoltification. Exogenous PRL and TSH have no effect on plasma corticosteroid levels at any time during smoltification. Plasma corticosteroid levels increase eight-fold between early April and late May in coho salmon, concurrent with increasing gill Na-K-ATPase and seaward migration. Generally, plasma levels of thyroxin and corticosteroids are related inversely. Thyroxin levels are maximum in early April, with the onset of silvering, and corticosteroids are at minimal concentrations at this time. Thereafter, thyroxin levels decline and corticosteroids increase. Title: Hormonal and osmoregulatory aspects of smoltification in coho salmon, Oncorhynchus kisutch Author: Specker, Jennifer Lee Coho salmon smolts (Oncorhynchus kisutch) were transported at low and high densities. (12 and 120 g/L) for short and long periods (4 and 12 h). Because smolts can be transplanted directly to seawater, half of the fish in each treatment were transported to tanks containing seawater and half to tanks containing freshwater. Plasma corticosteroids and glucose were elevated at unloading in all groups. Corticosteroids were still above the resting levels 24 h later, whereas glucose had returned to basal levels at this time. Potential smoltification indicators such as plasma thyroxin concentration and gill Na-K-ATPase activity were not affected by transportation. Increased corticosteroids were correlated to increased mortality in transported salmon compared to acclimated control fish when subjected to a bioassay of stress severe confinement. It is concluded that transportation induced stress in the fish regardless of hauling regimen, that increased corticosteroids may have potential as indicators of reduced performance capacity, that the greatest stress occurred during loading and the first few hours en route, and that transported coho salmon smolts seem to be equally fit for entry into freshwater or seawater. Hormones of the hypothalamic-pituitary system probably mediate the environmental changes and endogenous rhythms that regulate the timing and physiological alterations of smoltification. Because thyroid hyperactivity is a major endocrine component of smoltification, yearling coho salmon were injected with mammalian prolactin (PRL) and thyrotropin (TSH) to determine their effect on plasma thyroxin concentrations. The response of plasma thyroxin to TSH is similar from January through May in coho salmon, suggesting that the thyroid does not change in sensitivity to TSH. A dose of 0.04 to 0.07 I.U. TSH is the minimum dose sufficient to significantly increase plasma thyroxin concentration. PRL (1 to 9 I.U.) depressed plasma thyroxin levels in coho salmon parr, smolts, and post-smolts. Increased plasma thyroxin and gill Na-K-ATPase levels tentatively are considered indicative of smoltification, migratory readiness, and hence, seawater adaptability. In an experiment to consider a methodology which could be implemented at a culture facility to enhance the survival of ocean-going smolts and perhaps mitigate losses due to stunting, an abnormality of smoltification, coho salmon parr were maintained for 3 wk in water supplemented with sodium or calcium salts. Prolonged residence in sodium - supplemented freshwater increased plasma thyroxin levels and tended to elevate gill Na-K-ATPase activity. In contrast, acute exposure (24 h) to 75% seawater halved plasma thyroxin levels in coho salmon parr. Gradual acclimation to increased ambient salinity may accelerate changes in, or enhance, plasma thyroxin levels and gill Na-K-ATPase activity, and thus potentially improve the growth and survival of outmigrating smolts and reduce losses due to stunting. Plasma corticosteroid levels were determined during smoltification and in response to mammalian PRL and TSH. The interrenal tissue, which synthesizes corticosteroids, becomes hyperactive during smoltification. Exogenous PRL and TSH have no effect on plasma corticosteroid levels at any time during smoltification. Plasma corticosteroid levels increase eight-fold between early April and late May in coho salmon, concurrent with increasing gill Na-K-ATPase and seaward migration. Generally, plasma levels of thyroxin and corticosteroids are related inversely. Thyroxin levels are maximum in early April, with the onset of silvering, and corticosteroids are at minimal concentrations at this time. Thereafter, thyroxin levels decline and corticosteroids increase. Close

• 27. [Article] Relationship Between Temperature and Ceratomyxa shasta–Induced Mortality In Klamath River Salmonids

  This is the publisher’s final pdf. The published article is copyrighted by American Society of Parasitologists and can be found at: http://amsocparasit.org/.

  Citation × Citation Citation Abstract Copy Title: Relationship Between Temperature and Ceratomyxa shasta–Induced Mortality In Klamath River Salmonids Author: Bartholomew, Jerri L., Holt, Richard A., Ray, R. Adam This is the publisher’s final pdf. The published article is copyrighted by American Society of Parasitologists and can be found at: http://amsocparasit.org/. Title: Relationship Between Temperature and Ceratomyxa shasta–Induced Mortality In Klamath River Salmonids Author: Bartholomew, Jerri L., Holt, Richard A., Ray, R. Adam This is the publisher’s final pdf. The published article is copyrighted by American Society of Parasitologists and can be found at: http://amsocparasit.org/. Close

• 28. [Article] Exposure of coho salmon (Oncorhynchus lisutch) to petroleum hydrocarbons : effect on lipid metabolism and aryl hydrocarbon hydroxylase activity

  Coho salmon (Oncorhynchus kisutch) were exposed to sublethal levels of a water-soluble fraction (WSF) of Cook Inlet crude oil for periods ranging from 18 to 31 days, at four acclimation temperatures. The ...

  Citation × Citation Citation Abstract Copy Title: Exposure of coho salmon (Oncorhynchus lisutch) to petroleum hydrocarbons : effect on lipid metabolism and aryl hydrocarbon hydroxylase activity Author: Caldarone, Elaine Marie Coho salmon (Oncorhynchus kisutch) were exposed to sublethal levels of a water-soluble fraction (WSF) of Cook Inlet crude oil for periods ranging from 18 to 31 days, at four acclimation temperatures. The fatty acid composition of phospholipids extracted from muscle, gill, liver, and brain tissues, and, at three of the temperatures, the activity of the hepatic microsomal aryl hydrocarbon hydroxylase (AHH) system in the salmon, were determined. Induction of the ARE system due to exposure of the fish to the toxicant was observed in the warm acclimated (20.0 C) fish only. With minor exceptions, the fatty acid composition of phospholipids in all of the tissues analyzed, including those from the warm acclimated fish, were unaltered by exposure of the fish to the crude oil WSF. In both control and exposed fish, AHH activity was greater in fish acclimated to 7.8 C than to 20.0 C. The phospholipids from both exposed and control cold acclimated fish contained a higher percentage of polyunsaturated fatty acids than the phospholipids from the corresponding warm acclimated fish. The studies reported here indicate that exposure of coho salmon (O. kisutch) to sublethal levels of petroleum hydrocarbons does not appreciably alter the fatty acid composition of tissue phospholipids or affect the normal change in fatty acid composition associated with a change in acclimation temperature. The data obtained are insufficient to permit any conclusion regarding the possibility of an interaction between the MFO system and the metabolsim of polyunsaturated fatty acids in oil exposed salmon. Title: Exposure of coho salmon (Oncorhynchus lisutch) to petroleum hydrocarbons : effect on lipid metabolism and aryl hydrocarbon hydroxylase activity Author: Caldarone, Elaine Marie Coho salmon (Oncorhynchus kisutch) were exposed to sublethal levels of a water-soluble fraction (WSF) of Cook Inlet crude oil for periods ranging from 18 to 31 days, at four acclimation temperatures. The fatty acid composition of phospholipids extracted from muscle, gill, liver, and brain tissues, and, at three of the temperatures, the activity of the hepatic microsomal aryl hydrocarbon hydroxylase (AHH) system in the salmon, were determined. Induction of the ARE system due to exposure of the fish to the toxicant was observed in the warm acclimated (20.0 C) fish only. With minor exceptions, the fatty acid composition of phospholipids in all of the tissues analyzed, including those from the warm acclimated fish, were unaltered by exposure of the fish to the crude oil WSF. In both control and exposed fish, AHH activity was greater in fish acclimated to 7.8 C than to 20.0 C. The phospholipids from both exposed and control cold acclimated fish contained a higher percentage of polyunsaturated fatty acids than the phospholipids from the corresponding warm acclimated fish. The studies reported here indicate that exposure of coho salmon (O. kisutch) to sublethal levels of petroleum hydrocarbons does not appreciably alter the fatty acid composition of tissue phospholipids or affect the normal change in fatty acid composition associated with a change in acclimation temperature. The data obtained are insufficient to permit any conclusion regarding the possibility of an interaction between the MFO system and the metabolsim of polyunsaturated fatty acids in oil exposed salmon. Close

• 29. [Article] The antibody response of juvenile coho salmon (Oncorhynchus kisutch) to Aeromonas salmonicida, the causative agent of furunculosis

  This research was initiated to investigate the effects of various parameters on the immune response of juvenile coho salmon to Aeromonas salmonicida. The antibody response and development of protective immunity ...

  Citation × Citation Citation Abstract Copy Title: The antibody response of juvenile coho salmon (Oncorhynchus kisutch) to Aeromonas salmonicida, the causative agent of furunculosis Author: Paterson, William Douglas This research was initiated to investigate the effects of various parameters on the immune response of juvenile coho salmon to Aeromonas salmonicida. The antibody response and development of protective immunity in juvenile coho salmon were followed after a single intraperitoneal injection of formalin killed A. salmonicida cells emulsified in Freund's (complete) adjuvant. The first elevated antibody levels and protective immunity were detected four weeks after injection. High antibody titers were observed for a year after injection. Animals as small as 1.2 g were immunologically competent to administration of this antigen preparation. In a representative experiment, 96.7 percent of the animals injected with this preparation produced high levels of antibody. Selected methods of infection with A, salmonicida were investigated. Variability of culture virulence was demonstrated by injected LD₅₀ values, which ranged from a single cell to 10⁸ cells. Endotoxin was extracted from A. salmonicida cells with trichloroacetic acid. This endotoxin was found to be non lethal, but was antigenic to juvenile coho salmon at doses ranging from 1 to 5, 000 μg when administered intraperitoneally with and without an aluminum hydroxide carrier. The A. salmonicida endotoxin was lethal to white mice when administered by this same route. LD₅₀ values for several preparations ranged from 232 to 536 μg per mouse. An antibody response to A. salmonicida endotoxin was demonstrated in juvenile coho salmon held at 6.7°C, 12.2°C and 17.8°C. At these temperatures the first elevated antibody levels were observed at four, two and one week, respectively. Title: The antibody response of juvenile coho salmon (Oncorhynchus kisutch) to Aeromonas salmonicida, the causative agent of furunculosis Author: Paterson, William Douglas This research was initiated to investigate the effects of various parameters on the immune response of juvenile coho salmon to Aeromonas salmonicida. The antibody response and development of protective immunity in juvenile coho salmon were followed after a single intraperitoneal injection of formalin killed A. salmonicida cells emulsified in Freund's (complete) adjuvant. The first elevated antibody levels and protective immunity were detected four weeks after injection. High antibody titers were observed for a year after injection. Animals as small as 1.2 g were immunologically competent to administration of this antigen preparation. In a representative experiment, 96.7 percent of the animals injected with this preparation produced high levels of antibody. Selected methods of infection with A, salmonicida were investigated. Variability of culture virulence was demonstrated by injected LD₅₀ values, which ranged from a single cell to 10⁸ cells. Endotoxin was extracted from A. salmonicida cells with trichloroacetic acid. This endotoxin was found to be non lethal, but was antigenic to juvenile coho salmon at doses ranging from 1 to 5, 000 μg when administered intraperitoneally with and without an aluminum hydroxide carrier. The A. salmonicida endotoxin was lethal to white mice when administered by this same route. LD₅₀ values for several preparations ranged from 232 to 536 μg per mouse. An antibody response to A. salmonicida endotoxin was demonstrated in juvenile coho salmon held at 6.7°C, 12.2°C and 17.8°C. At these temperatures the first elevated antibody levels were observed at four, two and one week, respectively. Close

• 30. [Article] Properties of anti- Aeromonas salmonicida antibodies from juvenile coho salmon (Oncorhynchus kisutch)

  After parenteral immunization with Aeromonas salmonicida cells, the agglutination activity in juvenile coho salmon (Oncorhynchus kisutch) serum was associated with the macroglobulin serum fraction. Antibody ...

  Citation × Citation Citation Abstract Copy Title: Properties of anti- Aeromonas salmonicida antibodies from juvenile coho salmon (Oncorhynchus kisutch) Author: Cisar, John Ormond After parenteral immunization with Aeromonas salmonicida cells, the agglutination activity in juvenile coho salmon (Oncorhynchus kisutch) serum was associated with the macroglobulin serum fraction. Antibody activity was diminished by 30 minutes exposure to 50 C but not 45 C. Reduction with 2-mercaptoethanol and alkylation markedly lowered but did not completely destroy agglutination activity. The residual activity appeared to be maintained by noncovalent forces. The minimum antibody concentration required for agglutination of A. salmonicida cells was approximately 0.04 μgm protein/ml. The extreme sensitivity of this bacterial agglutination system is an important consideration in the interpretation of coho salmon anti- A. salmonicida titers. Specific antibodies were isolated from pooled coho salmon serum by dissociation of bacterial cell wall immune complexes with 15 percent NaCI. The procedure resulted in the recovery of about 30 percent of the total anti- A. salmonicida antibody. The purified antibodies had a sedimentation coefficient of approximately 17S. They migrated with the slowest moving serum component in alkaline polyacrylamide gel electrophoresis, and were restricted to the anodic portion of the serum immunoglobulin arc in immunoelectrophoretic separations. In spite of the restriction in electrophoretic mobility, the antibodies were quite heterogeneous and a minimum of 11 electrophoretic subpopulations of light chains were observed. Electron microscopy and sodium dodecyl sulfate-acrylamide gel electrophoresis revealed that the coho salmon anti- A. salmonicida rnacroglobulin was composed of four IgM-like subunits. No evidence for a low molecular weight antibody was obtained. Title: Properties of anti- Aeromonas salmonicida antibodies from juvenile coho salmon (Oncorhynchus kisutch) Author: Cisar, John Ormond After parenteral immunization with Aeromonas salmonicida cells, the agglutination activity in juvenile coho salmon (Oncorhynchus kisutch) serum was associated with the macroglobulin serum fraction. Antibody activity was diminished by 30 minutes exposure to 50 C but not 45 C. Reduction with 2-mercaptoethanol and alkylation markedly lowered but did not completely destroy agglutination activity. The residual activity appeared to be maintained by noncovalent forces. The minimum antibody concentration required for agglutination of A. salmonicida cells was approximately 0.04 μgm protein/ml. The extreme sensitivity of this bacterial agglutination system is an important consideration in the interpretation of coho salmon anti- A. salmonicida titers. Specific antibodies were isolated from pooled coho salmon serum by dissociation of bacterial cell wall immune complexes with 15 percent NaCI. The procedure resulted in the recovery of about 30 percent of the total anti- A. salmonicida antibody. The purified antibodies had a sedimentation coefficient of approximately 17S. They migrated with the slowest moving serum component in alkaline polyacrylamide gel electrophoresis, and were restricted to the anodic portion of the serum immunoglobulin arc in immunoelectrophoretic separations. In spite of the restriction in electrophoretic mobility, the antibodies were quite heterogeneous and a minimum of 11 electrophoretic subpopulations of light chains were observed. Electron microscopy and sodium dodecyl sulfate-acrylamide gel electrophoresis revealed that the coho salmon anti- A. salmonicida rnacroglobulin was composed of four IgM-like subunits. No evidence for a low molecular weight antibody was obtained. Close