Various aspects of rainbow trout (Salmo gairdneri) predation on migrating sockeye salmon (Oncorhynchus nerka) fry and rainbow trout eggs were studied during 1970-71 in specially-constructed artificial streams, and in the laboratory. Tests involving sockeye fry as prey were conducted near Babine Lake, British Columbia, while those using rainbow trout eggs were done near Abbotsford, British Columbia. Examination of the effects of physical factors such as water velocity, water turbidity, and light intensity on predation on migrating sockeye fry showed mortality to be inversely related to water velocity and water turbidity; inversely related to light intensity at low light levels but directly related at very low levels. Other stream tests showed mortality to be inversely related to the amount of exposure of predators to fry, before the beginning of a nightly fry migration. Exposing predators to abnormal light for varying periods of time, immediately prior to fry migration, reduced over-all mortality during fry migration. Mortality was not proportional to the length of exposure of predators to abnormal light. Fry experience with predators was shown to increase the ability of fry to escape or avoid predation on subsequent predator encounters. Additional experience served to further increase their ability to escape or avoid predators. Conclusions drawn from stream tests and a behavioral study are that experienced fry migrate in a manner rendering them less susceptible to predation and the migration pattern (compact and in mass) is influenced in part, or completely, by encounter and escape from predator-prey interactions experienced earlier. "Handling" or other fright-evoking stimuli appeared to have similar effects. Rainbow trout feeding on colored fish eggs indicated color preference patterns which are influenced by background coloration (color contrast between food and background), and light intensity. Preference was for colors showing the most contrast with the background at a particular light intensity. At low light levels, on a pale-blue background, preference was for lighter colors, while it was for darker colors at high light levels. Mortality differences increased proportionately with contrast between colors. Finally, trout displayed what appears to be a behavioral preference for red, and possibly blue, regardless of surrounding environmental conditions. In a food deprivation study rainbow trout displayed an S-shaped hunger response curve when fed on eggs. Indications were that rainbow trout will feed to gut capacity when given the opportunity. Finally, beyond an upper limit of food deprivation, the amount of food eaten by an individual remains fairly constant. / Science, Faculty of / Zoology, Department of / Graduate

Mitochondria were isolated from heart and mosaic muscle of rainbow trout (Salmo qairdneri R.). State 3 respiratory rates were determined at 5 and 15°C using pyruvate, malate, lactate, glutamate or acetyl—carnitine as substrate. The final three substrates were used to generate pH profiles. Pyruvate was oxidized at high rates in all cases, indicating good potential for aerobic carbohydrate metabolism. At 15°C, malate was an equally good substrate for heart mitochondria, while all substrates were oxidized at similar rates to pyruvate in muscle mitochondria. Maximal oxidation rates of heart mitochondria were greater than or equal to those of muscle. State 3 Q₁₀ for oxidation of most substrates in heart was approximately 2, except for malate which had a Q₁₀ of 3. Mitochondrial oxidation tended to be more sensitive to decreased temperature in muscle than in heart, particularly with respect to acetyl—carnitine and glutamate oxidation which in muscle had Q₁₀ values of 4 and 7, respectively. Based on RCR values at 5 and 15°C, there was no indication that membrane permeability to H⁺ ions was altered by a 10°C change in temperature in mitochondria from either tissue. At pH above 7.6 respiratory rates decreased with increasing pH. State 3 respiratory rate increased in heart mitochondria as pH decreased, below 7.6 while in muscle mitochondria, no such pH dependence was observed. RCR values were above 4 in all experiments except at high pH. Muscle mitochondria were the more sensitive to extreme pH with respect to RCR. Heart mitochondria had higher oxidative rates than those of muscle and were less sensitive to decreased temperature, in keeping with the greater oxidative demands of that tissue relative to mosaic muscle. Muscle mitochondria which typically face larger fluctuations in extramitochondrial pH in vivo than do those of heart, were less sensitive to pH in vitro. It was concluded that substrate utilization patterns and response to changes in temperature and extramitochondrial pH in the two mitochondrial populations was different and reflected both the intracellular environment of the mitochondria and the different needs of each tissue for aerobic energy supply. / Science, Faculty of / Zoology, Department of / Graduate

The response of rainbow trout (Salmo gairdneri) to lures was investigated in trolling experiments at Loon Lake, British Columbia. The "action" of a lure was found to be an important parameter in determining its efficiency: of four actions tested, the flatfish caught the greatest number of fish. Although the color of lure was not significant, red lures were more efficient than yellow, green, and blue, and more efficient than various color patterns of red and white. The presence of a dodger with lures did not affect their efficiency, but larger fish were caught. No size selection occurred with either colors or actions of lures. In laboratory feeding experiments using dyed trout eggs as food, red was selected first or second more often than yellow, green, or blue. The color of background against which the fish were fed, and individual differences among fish caused significant changes in the preference shown for various colors of food. Combining two colors also affected the selection intensity, depending upon the contrast between the two colors. Preferences for different colors of food were not influenced by the hunger level of the fish, measured in terms of the quantity of food in the fish's gut. In the course of the experiments it was incidentally observed: (1) that rainbow trout possess a striking ability to match the hue of their skin (mainly in the dorsal region) to that of the background in which they are kept; (Z) the color of background affects the activity level of rainbow trout: yellow produces the highest level of activity and green the lowest. / Science, Faculty of / Zoology, Department of / Graduate

The role of carbonic anhydrase in carbon dioxide excretion and acid-base regulation in the rainbow trout, Salmo gairdneri has been investigated. While a significant amount of carbonic anhydrase was found in the blood of the trout, calculations based on red cell hemolysates suggest that the probable circulating levels of carbonic anhydrase activity in blood may not be sufficient to account for the observed carbon dioxide excretion. An analysis of carbonic anhydrase activity in whole blood from the trout revealed that intact fish erythrocytes, unlike mammalian erythrocytes totally fail to facilitate the dehydration of extracellular bicarbonate. The possible mechanism of this phenomenon has been examined; however the salient point was that fish red blood cells do not appear capable and therefore by implication apparently not necessary for the excretion of carbon dioxide at the gills of trout. The observed excretion of carbon dioxide in the trout was found to be accounted for by the gills and their compliment of carbonic anhydrase. This finding was based on the following observations. (1) Depletion of circulating blood carbonic anhydrase levels during severe anemia was without effect on carbon dioxide excretion rates or blood acid-base status. (2) Introduction of the carbonic anhydrase inhibitor, diamox into anemic fish produced a severe acid-base disturbance associated with a fall in observed carbon dioxide excretion. (3) Isolated perfused gill preparations excrete carbon dioxide at rates comparable to those observed in vivo from free swimming fish. (4) Carbon dioxide excretion in isolated gill preparations is abolished by diamox. The excretion of carbon dioxide in fish occurs via the movement of plasma bicarbonate into the branchial epithelium, where it is subsequently dehydrated into molecular carbon dioxide and excreted. A model is proposed and supportive evidence presented to account for the coupling of ionic exchange occurring across the gill with carbon dioxide excretion. The proposed model distinguishes between control of plasma hydrogen ion activity and regulation of plasma total carbon dioxide concentration per se. The functional significance of this pattern of carbon dioxide excretion for aquatic animals is discussed along with the implications for air breathing fish. / Science, Faculty of / Zoology, Department of / Graduate

Juvenile rainbow trout (Oncorhynchus mykiss) were fed either 5 or 20 μg 2,2′,4,4′,5,5′‐hexachlorobiphenyl (245‐HxCB)/g diet (wet wt.) for 4, 8, or 12 weeks. Hepatic xenobiotic‐metabolizing enzyme activities and dietary 245‐HxCB accumulation in liver, muscle, and remaining carcass were determined. Liver‐to‐body weight ratios were not altered by either of the two 245‐HxCB concentrations. Relative growth rate increased with time but was not altered by 245‐HxCB concentration. Bioaccumulation of 245‐HxCB was dose and time dependent in all tissues without reaching apparent steady state. Hepatic arylhydrocarbon hydroxylase (AHH) activities increased with 245‐HxCB dose and with time. Ethoxyresorufin‐O‐deethylase (EROD) activities also increased in fish fed 20 μg 245‐HxCB/g diet. No 245‐HxCB‐induced changes in uridine diphosphoglucuronosyl transferase (UDP‐GT) or NADPH‐cytochrome‐c reductase (NCCR) activities were determined. High‐resolution GC‐MS analysis of the 245‐HxCB standard revealed trace (0.4‐0.5%) contamination by two mono‐ortho pentachlorobiphenyls (PnCBs): 2,3,3′,4,4′‐PnCB and 2,3,4,4′,5‐PnCB. Total liver accumulation of these contaminants was inversely related with corresponding EROD and AHH activities and estimated to contribute minimally to their induction. Results from this study suggested that long‐term dietary 245‐HxCB exposures induced cytochrome P4501A activities in rainbow trout liver.

<p> Knowledge into uptake rate and interactions of the metals via the gastrointestinal tract of freshwater fish is vital, in order to provide tools to protect and to sustain aquatic biota. An in vitro stomach and gut sac technique was utilized to investigate uptake rates of essential metals (copper, zinc and nickel) and non-essential metals (cadmium, lead and nickel) at luminal concentrations of 50fJ.M via the gastrointestinal tract Metals had no effect on the fluid transport rates via the gastrointestinal tract except for copper at the stomach. The stomach emerged as small but important site for metal absorption and interaction. Essential metals were absorbed at approximately the same rate as nonessential metals via the gastrointestinal tract. Copper, zinc, nickel, silver, and lead showed statistical correlation between rate of absorption and mucus binding via gastrointestinal tract, an important first finding for the development of a Biotic Ligand Model (BLM) for the gastrointestinal tract of trout. </p> <p> There was an antagonistic effect of calcium on cadmium uptake at the stomach but not at the intestine. Zinc and calcium exhibited synergistic interaction at the stomach but no interaction at the intestine. These results showed the possibility of the transporters DMTl to mediate copper and cadmium uptake via the intestine; hZip 2 to mediate copper and zinc uptake at the stomach; and Mzip 4 or ZTLl to mediate zinc uptake via the gastrointestinal tract of trout. These results can be used to develop a BLM for the gastrointestinal tract of fish. </p> / Thesis / Master of Science (MSc)

<p> Juvenile rainbow trout (Oncorhynchus myldss) were chronically exposed (90 days) in synthetically softened water ([Ca2+]=50, [Na+]=100 J.tequiv·L-1), to sublethal low pH (5.2) and a simulated global warming scenario (+20C), added to the natural summer thermal cycle ofinshore Lake Ontario. Two studies were conducted over the periods June September 1993 and 1994 in order to examine the effects ofthe sublethal stressors under conditions ofunlimited food ration (satiation feeding twice daily= 10% dry body weight·day-1), and a limited food ration (4% dry body weight·day-1) respectively. The addition of 2°C and sulphuric acid was designed to result in four treatment conditions: i) Control conditions; ambient water temperature and pH; ii) ambient water temperature and pH 5.2; iii) simulated global warming at ambient pH; iv) a combination of simulated global warming and pH 5.2. Year to year variation in temperature provided the trout in the satiation-fed study with an ambient ~peraturerange of 13-24°C, while those in the limited ration study experienced a range of 16.5-21°C. Consequently, the trout in the treatments with an additional 2°C experienced temperatures close to the upper incipient lethal level, particularly the trout in the satiation feeding study. Apparent specific dynamic action raised routine metabolic rates in all treatments to -75% and 55% M02(max) in the satiation and limited ration studies respectively, the difference of 20% indicating the influence of an unlimited feeding regime on metabolism. Trout in the satiation feeding study increased in wet body mass by 30-50 g, while trout in the limited ration study increased by only 3-4 g. Whole body proximate composition of the trout fed to satiation changed over time with large increases in lipid content, small increases in protein content, and compensating decreases in water content in all treatments. No such changes occurred in the limited ration trout, although whole body lipid and carbohydrate were highly variable. In both studies, the addition of20C resulted in decreased growth, with an accompanying depression in appetite in the satiation fed trout, especially at peak temperatures. Surprisingly, trout exposed to low pH alone exhibited improved growth in both treatments. Energy budgets indicated that the addition of 2°C reduced gross energy intake and increased fecal (and Ulllidentified) energy losses resulting in lowered conversion efficiencies, while in limited ration trout, energy expenditure was slightly higher. Trout exposed to low pH exhibited higher gross energy intake and gain, and more efficient energy conversion under unlimited food conditions while trout with limited rations expended the least metabolic energy and exhibited lower nitrogen energy losses. The surprising lack of ionoregulatory disturbance in these pH 5.2 exposed trout in both studies suggests tbat the availability of NaCl in the diet was compensating for branchial ion losses, and perhaps driving appetite in the satiation fed trout Where ration was limited, reductions in activity level may have contributed to energy conservation and consequently improved growth. A 22Na+ flux experiment conducted at the end of the limited ration exposure, in which the fish were exposed to a challenge concentration of H+ (pH 4.2), provided evidence for improved recovery of ionoregulatory balance in trout which had been chronically exposed to low pH. Overall, the combination ofincreased global temperatures and sublethal low pH results in increased physiological costs for juvenile rainbow trout, most noticeably when summer temperatures peak. Ration level is of integral importance when considering the degree of impact of such environmental conditions. </p> / Thesis / Master of Science (MSc)

Largely through the use ofin vitro preparations there is now a generally accepted theory for ion transport for the seawater (SW) gill. However, to date there is no generally accepted freshwater (FW) model for the mechanisms of NaCl transport in the teleost gill. By using an Ussing chamber approach with the opercular epithelia of Fundulus heteroclitus and Oreochromis niloticus, and the urinary bladder of Oncorhynchus mykiss, all acclimated to FW, we hoped to establish one as a possible model for the study of FW ion regulation. FW Fundulus opercular epithelia displayed a serosal negative transepithelial potential (Vₜ) of-43.9 mV, transepithelial conductance (Gₜ) of 1.94 mS·cm⁻², and active transport of Cl⁻ from the mucosal FW against a strong electrochemical gradient. Na⁺ movement was dominated by passive diffusion. The opercular epithelia of Fundulus adapted to 10% SW exhibited properties similar to SW Fundulus by actively extruding Cl⁻ while Na⁺ moved passively into the mucosal 10% SW. With FW bathing the mucosal surface, FW Oreochromis opercular epithelia displayed a serosal positive Vₜ of +8.0 mV, Gₜ of 1.78 mS·cm⁻², and active reabsorption of Na⁺, Cl⁻ and Ca²⁺ against large electrical and/or chemical gradients. The FW Oreochromis opercular epithelia is the only FW in vitro preparation to date that exhibits active absorption (albeit at small absolute rates) of both Na⁺ and Cl⁻. FW 0. mykiss urinary bladders mounted in vitro under symmetrical saline conditions exhibited a transepithelial conductance (Gₜ) of-9.15 mS·cm⁻² and electroneutral active absorption of Na⁺ and Cl⁻ from the mucosal urine side. The transport of Na⁺ and Cl⁻ was a partially coupled process whereby removal of Na⁺ from the mucosal saline decreased Cl⁻ absorption by a 56% and removal of Cl⁻ inhibited Na⁺ absorption by 69%. However, active net absorption of both ions persisted when the counter-ion was replaced with a non-permeant ion. Under more realistic conditions with artificial urine bathing the mucosal surface, Vₜ increased to a serosal positive ~+7.6 mV and Gₜ decreased to ~1.47 mS·cm⁻² Unidirectional influx rates of both Na⁺ and Cl⁻ were much lower, but active absorption of both ions still occurred. Replacement of Na⁺ in the mucosal artificial urine caused no change in unidirectional influx of Cl⁻ and vice versa. The mucosal addition of DIDS, amiloride or bumetanide (10⁻⁴M) all had no affect on absorption rates of Na⁺ and/or Cl⁻, under either artificial urine or symmetrical saline conditions. When the mucosal surface was bathed in artificial urine, removal of mucosal Cl⁻· significantly reduced the maximum transport rate (Jₘₐₓ of Na⁺ (6.1 ~2.1 μmol·cm⁻²·h⁻¹) but had no effect on affinity for Na⁺ (Kₘ~27 mM). Similarly, removal of mucosal Na⁺ significantly reduced the Jₘₐₓ for Cl⁻ uptake (11.4 ~2.4 μmol·cm⁻²·h⁻¹) but had no effect on Cl⁻ Kₘ(~37 mM). The anterior portion of the urinary bladder transported Na⁺ and Cl⁻ at a faster rate than the posterior portion under symmetrical saline conditions, but there was no difference in measured Na⁺/K⁺ -ATPase activities between the two portions. In conclusion, opercular epithelia of Fundulus and Oreochromis demonstrated transport properties believed to be typical of FW teleosts; either preparation may eventually prove to be a good working model for studying FW transport mechanisms. The urinary bladder of Oncorhynchus mounted in vitro did not behave characteristically as the teleost gill is thought to function, but this model may be useful in characterizing various other mechanisms of ionic transport. / Thesis / Master of Science (MSc)

This thesis examined the function of the urinary bladder in vivo in the freshwater rainbow trout. In the first part of the study two new techniques were developed to examine the possible urine storage and ionoregulatory roles of the bladder in vivo. An indirect approach, using non-catheterized fish, involved "spot sampling" from the bladder to determine urine composition, and measurement of the appearance of ^3H polyethylene glycol-4000 (a glomerular filtration marker) in surrounding water to quantify urination events. The direct approach employed a new external catheterization technique to collect naturally discharged urine. Both methods demonstrated that resting trout urinate in intermittent bursts at 20-30 min intervals, and that natural urine flow rate (U.F.R.) is at least 20 % lower and urinary Na^+ and Cl^- excretion rates at least 40% lower than determined by the traditional internal bladder catheter technique. The urine is stored for approximately 25 min prior to discharge, and significant reabsorption of water and ions (Na^+, Cl^-, K^+, urea, and possibly other substances) occurs via the bladder epithelium during this period; a small residual volume is likely always maintained. The second part of the study employed the new external catheter and the traditional internal catheter to quantify the responses of the bladder, relative to those of the kidney, to two experimental disturbances. Chronic (32 h) infusion with 140 mM NaCl produced isosmotic volume loading without a change in plasma [Na^+], [Cl^-], or acid-base status. The kidney responded with a large increase in glomerular filtration rate (G.F.R.), a smaller increase in U.F.R., and increased reabsorption of water and ions. The bladder responded with a small increase in urination burst volume, a larger increase in burst frequency, and therefore a decreased urine storage time. Despite this increased throughput, Na^+ and Cl^- reabsorption rates across the bladder epithelium actually increased. Reabsorption of urea and K^+ remained constant, despite expected decreases due to decreased urine storage time. A similar infusion with 140 mM NaHCO_3 produced isosmotic volume loading together with metabolic alkalosis reflected m increased blood pH, increased plasma [HCO_3^-], decreased plasma [Cl^-], with no change in plasma [Na^+]. The response of the kidney was similar, though HCO_3^- filtration, reabsorption, and excretion rates all increased, while rates for Cl^- were proportionately lowered; renal Na^+ handling was unaffected. Bladder urination patterns and Na^+ reabsorption were also similar, but there was no evidence of bladder involvement in HCO_3^- secretion or reabsorption (ie. in acid-base regulation). It is concluded that previous studies using internal catheterization have greatly underestimated the ionoregulatory effectiveness of the entire renal system by negating bladder function. The external catheterization technique developed in this thesis provides researchers with a method to collect naturally vented urine, and thereby evaluate the role of the entire renal system, including the bladder, in response to experimental manipulations. / Thesis / Master of Science (MS)

Three hundred rainbow trout from each of two strains (Wytheville and the Soap Lake) were exposed in equal numbers to three non-overlapping wavebands of light (red, green, blue). One hundred fish from each strain were used as a control. These fish were exposed to unfiltered light of intensity equal to that of the three spectral treatments (21.4 lux). All fish were exposed to continuous light of the assigned experimental spectra for 53 days. Fish were fed trout chow twice daily at a rate previously found to maximize growth and efficiency. This feeding rate was determined by consulting hatchery records and the feeding charts developed by Haskell (1959). Mean length and mean weight of test animals may be affected by the rearing of individuals under specific wavebands of light (α = .001). Fish grown under blue or green light had the greatest mean length and fish grown under control or green light had the greatest mean weight while those reared under red light had the lowest mean length and mean weight. Although differences in coefficient of condition, yield, ferd conversion ratio, and survival were not Significant between light treatments (α = 0.05) in my study, significant differences may possibly be found in studies with a larger sample size. Although high variability and small sample size limit interpretation, this study suggests that certain light treatments used in conjunction with certain strains of fish could improve hatchery production. / Master of Science