Donald V. Rottiers

Movement of Underyearling Walleyes in Response to Odor and Visual Cues

Abstract Underyearling walleyes, allowed to move freely in a Y-shaped chamber into which various substances were added to one arm or another, were attracted to sodium chloride, sucrose, glutathione, vitamin B12, betaine, arginine, Daphnia slurries, some fish slurries, washings from live Daphnia and Artemia, and some commercial fish foods. They avoided cysteine, glycine, glycine-betaine, Artemia slurries, some fish slurries, and fish mucus; and showed little reaction to valeric and caproic acid, and some commercial fish foods. Tests of visual response, in which beakers containing live food organisms were placed in the arms of the chamber, indicated that walleyes respond strongly to the movement of food organisms. Walleyes usually surrounded the beakers containing live food organisms and repeatedly struck the glass. They were attracted more strongly to Artemia than to Daphnia. Results indicate that odor plays an important role in movement of walleyes to food and that there is a potential for attracting inte...

Elemental composition of a migratory and a land-locked strain of Atlantic salmon Salmo salar

Abstract 1. 1. The growth and elemental composition of an anadromous strain and a land-locked strain of Atlantic salmon (Salmo salar) were compared. 2. 2. All fish were raised from the egg stage under identical conditions. 3. 3. The land-locked strain was significantly higher in lipids than the anadromous strain throughout the study. 4. 4. Results of exposure to seawater at 2-week intervals between days 431 and 512 of the study indicated that neither strain produced smolts. 5. 5. Strains could not be separated by discriminant analysis into separate groups, based on concentrations of the six most abundant elements or all ten elements sampled during the expected period of smolting (days 440–550). 6. 6. The laboratory fish differed significantly in composition from those collected in the Merrimack River. 7. 7. The loge of the whole-body element content increased significantly with loge of wet body wt in both strains.

Energy Budget for Yearling Lake Trout, Salvelinus namaycush

ABSTRACT Components of the energy budget of yearling lake trout (Salvelinus namacush) were derived from data gathered in laboratory growth and metabolism studies; values for energy lost as waste were estimated with previously published equations. Because the total caloric value of food consumed by experimental lake trout was significantly different during the two years in which the studies were done, separate annual energy budgets were formulated. The gross conversion efficiency in yearling lake trout fed ad libitum rations of alewives at 10°C was 26.6% to 41%. The distribution of energy with temperature was similar for each component of the energy budget. Highest conversion efficiencies were observed in fish fed less than ad libitum rations; fish fed an amount of food equivalent to about 4% of their body weight at 10°C had a conversion efficiency of 33% to 45.1%. Physiologically useful energy was 76.1–80.1% of the total energy consumed. Estimated growth for age-I and -II lake fish was near that observed ...

Articles: Lack of Dietary Effects on the Timing of Smoltification in Atlantic Salmon

Abstract Six commercially available diets varying in lipid, protein, water, ash, and carbohydrate contents were fed to Atlantic salmon (Salmo salar) for 2 years to determine if diet affected smoltification. Each month, from March to September of the second year, sampled fish were exposed to 33‰ seawater for 24 h to determine smolt readiness, defined as the ability to maintain water and salt balance in a seawater challenge. Regardless of diet, Atlantic salmon were able to regulate plasma sodium and chloride ions (smoltify) only during early May. It is unlikely that hatchery managers could effectively use high-energy diets to control the time of smoltification in Atlantic salmon.

Towable Cage for Studies of Smoltification in Atlantic Salmon

Abstract The floating towable cage described in this report was used successfully to hold and transport Atlantic salmon (Salmo salar) in estuarine waters. These rugged and versatile cages, constructed from readily available, inexpensive materials, were tied singly and in clusters to floating docks in fresh and brackish water, where they withstood strong currents, winds, floods, and tides for 2.5 months without visible damage.

Volitional Migration of Atlantic Salmon from Seasonal Holding Ponds

Abstract For 5 years we used seawater tolerance tests (seawater challenges) to identify smolts, and tunnel fish counters to record the time of migration, of Atlantic salmon Salmo salar that volitionally left holding ponds on the Merrimack River near Litchfield, New Hampshire. We compared timing of Atlantic salmon movements with environmental conditions and blood composition of migrating and nonmigrating fish. None of the pan from the Nashua National Fish Hatchery (NFH) tested in seawater in 1984–1986 and from the North Attleboro NFH tested in 1987–1988 smoltified in the ponds. Yet, smolts were seemingly produced because 50 of 135 Atlantic salmon with radio transmitters from these ponds were traced to the ocean, and 9 of the 20,680 Atlantic salmon marked in 1984 from Litchfield subsequently returned to spawn. In all years except 1987, we forced Atlantic salmon out of the ponds by mid-May because of high water temperatures. In 1987, all Atlantic salmon from the North Attleboro NFH left the smolt-holding pon...

Growth of tiger muskellunge fed different amounts of protein at three water temperatures

Abstract Growth rates of tiger muskellunge (muskellunge Esox masquinongy ♀ x northern pike E. lucius ♂) fed diets containing 35, 45, or 55% crude protein for 5 weeks at 17, 20, or 23°C were compared. Fish fed diets containing 45 or 55% protein grew faster at all temperatures than those fed 35% protein. Growth of tiger muskellunge fed a diet containing either 45 or 55% protein did not increase significantly at optimum growth temperatures (20 or 23°C). At 17°C, below the optimum temperature range, growth did increase when the percentage of protein in the diet was increased.

Effects of Day Length and Cleaning Regimen on the Growth of Yearling Parr Atlantic Salmon

Abstract Yearling Atlantic salmon (Salmo salar) were reared with 8 or 16 h of light each day in laboratory tanks that were cleaned daily or weekly, and growth was measured weekly for 10 weeks. Growth was greatest for fish on the 16-h light and weekly cleaning routine. Reduced frequency of tank cleaning (weekly) significantly enhanced growth but accounted for only 8.5% of the partitioned variance, compared with 78.9% for increases in day length alone. Results of this study suggest that the increased growth observed at longer day lengths was primarily due to the stimulatory effects of increased amounts of light.

Support rack for portable water chillers

Abstract Construction and use of a polyvinyl chloride pipe rack that provides a safe, convenient, and versatile way of handling and storing portable 746-W water chillers are described.

Survival of Caged Atlantic Salmon in the Merrimack River

Abstract Because it is difficult to locate parr and smolts of Atlantic salmon Salmo salar in the lower Merrimack River in order to measure survival and evaluate physiological changes, 1 held hatchery fish in 122 × 46 ×61-cm cages at three sites for up to 70 d in 1988 and 1989, beginning each year in early April. Stationary cages were placed at two freshwater sites (3 and 7.8 km above the mouth of the river) and at a tidal freshwater–seawater site, and then stocked with fish. Movable cages were placed in the river at the most upstream stationary-cage site, stocked with fish, and later moved downstream by boat at irregular intervals. At the most upstream site mortality gradually increased through the season, reaching the highest level (about 60%) during a period of rising temperatures in late May. Although extremes in temperature and salinity were greatest at the freshwater–seawater site, mortality was lowest in the stationary cage there, The number of Atlantic salmon infected with Aeromonas salmonicida inc...