Canadian Science Publishing
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Chemical Changes During the Seasonal Cycle of Growth and Decay in Eelgrass (<i>Zostera marina</i>) on the Atlantic Coast of Canada In a submerged bed of eelgrass, newly formed leaves in winter and spring had their maximum levels of total organic matter (90% of dry weight), soluble organic fraction (45%), carbon (42%), and nitrogen (4.8%). These components all decreased as the leaves matured, aged, and died. Soon after death, a leaf had only 70% total organic matter, 28% soluble organic matter, 30% carbon, and 1.5% nitrogen. Intact dead leaves showed little further change in chemical composition. The commonly used crude protein determination (6.25 × nitrogen content) overestimated true protein by up to 180%. The carbon to nitrogen ratio (C:N) was an unreliable index of the nutritional value of the plant. Two growth forms were present, most probably in response to wave action and substrate composition. Daylength, not temperature, most probably controls the seasonal cycle of growth.
Canadian Science Publishing - Tập 32 Số 5 - Trang 615-621 - 1975
Physiological Response of Juvenile Coho Salmon (<i>Oncorhynchus kisutch</i>) and Rainbow Trout (<i>Salmo gairdneri</i>) to Handling and Crowding Stress in Intensive Fish Culture Moving 4–5-in. coho salmon (Oncorhynchus kisutch) held in soft (20 ppm CaCO3 ) water from the relatively light loading density of 0.5 lb/ft3 to 1, 2, or 4 lb/ft3 (density index, DI = 0.1, 0.2, 0.4, 0.8) caused significant stress as indicated by loss of feeding behavior, but only minimal physiological disturbances, as indicated by lack of hyperglycemia or hypochloremia. However, moving them to 6 or 12 lb/ft3 (DI = 1.2, 2.4) caused significant physiological stress which required at least a week for recovery. Smolting coho salmon were physiologically stressed by population densities of 1 lb/ft3 or more and a subclinical corynebacterial kidney infection was activated. Rainbow trout (Salmo gairdneri) (4–5 in.) were physiologically stressed when moved and held at 1 lb/ft3 or more but retained normal feeding behavior. This indicates that handling and crowding stress will be minimized in softwater areas if densities in fish distribution trucks or in ponds or raceways during disease treatments are held to 0.1–0.5 lb/gal.
Canadian Science Publishing - Tập 33 Số 12 - Trang 2699-2702 - 1976
Comparative Agonistic and Feeding Behavior of Hatchery-Reared and Wild Salmon in Aquaria When hatchery-reared and wild landlocked Atlantic salmon (Salmo salar) parr of the same age and size were permitted to compete for social dominance and for food in aquaria, twice as many hatchery salmon attained dominance as wild salmon. Dominant hatchery salmon also showed a higher intensity of aggressiveness than dominant wild salmon, displaying a higher and more variable mean nipping rate. Socially dominant salmon ate more food per fish than subordinates, but there were no statistically significant differences in feeding rate between dominant hatchery and dominant wild salmon, or between subordinate hatchery and subordinate wild salmon.Hatchery salmon displayed lower feeding rates than wild salmon when they were held in separate compartments of an aquarium and compared at three temperatures. This difference in feeding rate probably was not a reflection of differences in adaptation to temperature or food preference, but, rather, was the result of interference with feeding caused by the more intense social interaction among hatchery fish.It is suggested that high levels of aggressiveness may contribute to mortalities of hatchery-reared salmon planted in streams because of loss of feeding time, excessive use of energy, and increased exposure to predators.
Canadian Science Publishing - Tập 25 Số 1 - Trang 1-14 - 1968
Theoretical and Experimental Analysis of the <sup>14</sup>C Technique and Its Use in Studies of Primary Production Theoretical and experimental field studies of 14 C uptake by marine phytoplankton were carried out to determine environmental conditions required for the technique to measure net photosynthesis. Results of theoretical studies indicate that rapidly metabolizing populations (rate constants for gross photosynthesis and respiration of 0.1 h−1 and 0.007 h−1 respectively) may saturate with 14 C after about 30 h of continuous irradiation. Results of field studies indicate that a minimum of 24 h are required for net photosynthesis to be measured when daily irradiations exceed 20 cal cm−2 and nutrient limitation of photosynthesis does not occur. Additional measurements that may be made to aid in interpreting results obtained by the 14 C technique are briefly discussed.
Canadian Science Publishing - Tập 33 Số 8 - Trang 1715-1721 - 1976
Effects of Constant Temperatures and Diel Temperature Fluctuations on Specific Growth and Mortality Rates and Yield of Juvenile Rainbow Trout, <i>Salmo gairdneri</i> Specific growth and mortality rates of juvenile rainbow trout (Salmo gairdneri) were determined for 50 days at seven constant temperatures between 8 and 22 °C and six diel temperature fluctuations (sine curve of amplitude ±3.8 deg C about mean temperatures from 12 to 22 °C). For constant temperature treatments the maximum specific growth rate of trout fed excess rations was 5.12%/day at 17.2 °C. An average specific mortality rate of 0.35%/day was observed at the optimum temperature and lower. At temperatures in excess of the growth optimum, mortality rates were significantly higher during the first 20 days of this experiment than the last 30 days. The highest constant temperature at which specific growth and mortality rates became equal (initial biomass remained constant over 40 days) was 23 °C. The upper incipient lethal temperature was 25.6 °C for trout acclimated to 16 °C. A yield model was developed to describe the effects of temperature on the living biomass over time and to facilitate comparison of treatment responses. When yield was plotted against mean temperature, the curve of response to fluctuating temperatures was shifted horizontally an average 1.5 deg C towards colder temperatures than the curve of response to constant temperature treatments. This response pattern to fluctuating treatments indicates that rainbow trout do not respond to mean temperature, but they acclimate to some value between the mean and maximum daily temperatures. These data are discussed in relation to establishment of criteria for summer maximum temperatures for fish. Key words: constant temperature, fluctuating temperature, specific growth rate, specific mortality rate, yield, lethal temperature, zero net biomass, rainbow trout, thermal criteria
Canadian Science Publishing - Tập 34 Số 5 - Trang 639-648 - 1977
Review of Studies on Feeding of Aquatic Invertebrates Conducted at the Institute of Biology of Inland Waters, Academy of Science, USSR The main results obtained at the Borok Institute during the last decade are reviewed. Food and methods of feeding by various aquatic invertebrates (Rotatoria, Oligochaeta, Mollusca, Cladocera, Copepoda, Chironomidae larvae), daily food consumption, and assimilation of food have been investigated. Most invertebrates are omnivores although some species live on only one type of food. Daily food consumption changes with food concentration, temperature, and size of consumer. At 15–22 C and a concentration of food close to optimum, mean daily rations of most invertebrates studied usually range from 25 to 100% of body weight. Only in pulmonary Gastropoda and silt-eating Tubificidae does it greatly exceed body weight. In rare cases, at very high concentration of food unusual in nature, the so-called "extra feeding" may take place under experimental conditions. For most invertebrates feeding on natural food at optimum concentrations, index of assimilation varies widely, but rarely exceeds 50%. The assimilability of plant food was 45–55% in the majority of investigated species and appears to be considerably higher when animal food is used.
Canadian Science Publishing - Tập 29 Số 4 - Trang 363-383 - 1972
Formulating Practical Diets for Fish Formulas for balanced fish diets must include an energy source plus sufficient indispensable amino acids, essential fatty acids, and specific vitamins and minerals to support life and to promote adequate growth. Tentative requirements for the 10 indispensable amino acids and evaluation of the sparing effect of several others have been reported for only a few species of fish held under specific experimental conditions. These findings must be confirmed for other species and other rearing conditions, since the protein requirement and amino acid balance is the major determinant for growth, and is the greatest food source problem. Essential fatty acid needs for fish reared indicate that this component may be the second limiting factor for future practical diets. Water-soluble and fat-soluble vitamin needs have been reported for only a few fish and these data must be extended to include other species and fish reared in different waters. Digestion coefficients of diet ingredients, measured for terrestrial animals, must be confirmed in fish before data banks of nutrient ingredient sources can be translated into least-cost computer diet formulas. Specific nutrient requirements vary with species, size, water temperature, stress, and nutrient balance; thus, economical rations must be programmed accordingly. Techniques that have been developed for determining metabolizable energy and digestibility of diet components for several species can be expanded to develop diets and rations for scientific fish husbandry.
Canadian Science Publishing - Tập 33 Số 4 - Trang 1032-1039 - 1976
Polycyclic Aromatic Hydrocarbon Carcinogens in Commercial Seafoods Fresh and processed commercial seafoods were analyzed for the polycyclic aromatic hydrocarbon carcinogen benzo(a)pyrene using a thin-layer chromatographic separation technique and quantitation by fluorescence. Commercial samples of vertebrate fish did not contain detectable levels, except where fish were packed with vegetable oil, an exogenous source of carcinogens. Levels in most shellfish samples were generally less than 10 ng/g wet weight, but occasional samples contained up to 36 ng/g. Crab and shrimp samples contained little or no benzo(a)pyrene (ND to 0.5 ng/g). Commercial lobsters contained 0.8 to 7.9 ng/g. The source of contamination of lobsters was further investigated, utilizing high pressure liquid chromatography to measure 13 polycyclic aromatic hydrocarbon isomers. Freshly caught lobsters had less than 1 ng/g benzo(a)pyrene. Lobsters which had been kept in a commercial tidal pound constructed of creosoted timber contained highly elevated levels of benzo(a)pyrene and other carcinogenic hydrocarbons, including chrysene, benzo(a)anthracene, benzo(b)fluoranthene, dibenz(a,h)anthracene, and indeno(1,2,3-cd)pyrene The maximum level of benzo(a)pyrene was 2300 ng/g wet weight in digestive gland, and 281 ng/g in edible tail meat. These levels are substantially higher than previously reported for any foodstuff, and are most probably attributable to creosote contamination during impoundment. Key words: benzo(a)pyrene, polycyclic (polynuclear) aromatic hydrocarbon, carcinogen, seafood, lobster, shellfish, creosote
Canadian Science Publishing - Tập 36 Số 12 - Trang 1469-1476 - 1979
Some Relations Between Zooplankton and Bunker C Oil in Chedabucto Bay Following the Wreck of the Tanker <i>Arrow</i> Zooplankton ingested small particles of oil that were found dispersed throughout the water column in Chedabucto Bay following the wreck of the tanker Arrow. As much as 10% of the bunker C in the water column was associated with zooplankton and their feces contained up to 7% bunker C. The oil had no apparent effect on the organisms. In addition to the particulate oil which was exported from the bay by hydrodynamic processes, perhaps 20% more was sedimented to the bottom as zooplankton feces.
Canadian Science Publishing - Tập 28 Số 9 - Trang 1327-1330 - 1971
A Simple Mechanism that Causes Collapsing Stability Regions in Exploited Salmonid Populations Depensatory predation mortality on salmon when added to a Ricker production model can create a system with at least two stable equilibria and two domains of attraction. The behavior of such a fish system is different from a single equilibrium situation and a simple mechanism is described through which commercial exploitation changes the ability of such multiple-equilibrium fish populations to respond to perturbations in survival rates. Furthermore, it is shown that this change in size of stability regions is proportional to the exploitation rate and that classically defined maximum sustainable yield (MSY) exploitation rates are inevitably close to the rates that would cause a drastic decrease in the population. The uncertainties inherent in environmental effects on survival and in achievement of desired exploitation rates precipitate the need to back away from the usual MSY exploitation rates and set up (through enhancement) a system of stocks whereby feedback information is provided to the manager. This approach of adaptive management seeks reasonable yields while gaining information about the state (or changes in state) of the system. Some applications of catastrophe theory are discussed, especially with reference to harvesting multiple-stock salmon systems. Key words: stability, resilience, exploitation, salmon, depensation, multiple equilibria, adaptive management, enhancement, catastrophe theory
Canadian Science Publishing - Tập 34 Số 8 - Trang 1130-1142 - 1977
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