Young Atlantic Salmon Research Articles

Tetrachloro-o-benzoquinone as a Component in Bleached Kraft Chlorination Effluent Toxic to Young Salmon

Evidence is given that tetrachloro-o-benzoquinone is involved in the toxicity of bleached kraft chlorination effluent (BKCE) to young Atlantic salmon, Salmo salar. The main experimental support was isolation of tetrachlorocatechol from whole BKCE and from a BKCE fraction toxic to salmon, after reduction of both with sodium borohydride. Tetrachloro-o-benzoquinone was shown to be toxic to salmon at low concentrations. Instability of the toxic component in BKCE and substantial loss of toxicity upon treatment of BKCE with sulfur dioxide agreed with the properties of tetrachloro-o-benzoquinone in water solution.

Effects of Forest Spraying with DDT in New Brunswick on Food of Young Atlantic Salmon

Food in stomachs of young Atlantic salmon from the Northwest Miramichi River, N.B., changed following aerial DDT spraying of the surrounding watershed. Before spraying, young salmon typically ate immature aquatic insects, fry (underyearlings) concentrating on Diptera and small Ephemeroptera, and parr (overyearlings) on Diptera, Trichoptera, and all sizes of Ephemeroptera. Reduction of all aquatic insects by DDT was soon followed by resurgence of Chironomidae and other Diptera, and surviving fry fed heavily on these; parr fed on Diptera but also ate snails, worms, and fish, previously unimportant in their diet. Five years after the last spraying the pre-spray complexity of young salmon food was being approached. Trichoptera were slowest of the major fish-food types to reappear in stomachs.In fry stomachs Ephemeroptera, and in parr stomachs Ephemeroptera and Trichoptera, were relatively more abundant than in the surrounding stream fauna. Greater availability of these insects and active selection by fish are discussed as possible causes of these relationships.

Fish Losses After Forest Sprayings with Insecticides in New Brunswick, 1952–62, as Shown by Caged Specimens and other Observations

The survival of young Atlantic salmon and eastern brook trout, held in cages and free-living, was observed in New Brunswick streams inside and outside forested areas sprayed operationally and experimentally from aircraft with DDT and other insecticides for budworm control. DDT-in-oil in a single application at [Formula: see text] caused heavy loss of underyearling salmon and parr within 3 weeks. DDT-in-oil at [Formula: see text] had no apparent short-term effects on salmon parr, but killed many underyearlings; two applications 10 days apart were about as harmful as a single application at [Formula: see text]. DDD at [Formula: see text] and [Formula: see text], and malathion at [Formula: see text], were no more harmful to young salmon than DDT at [Formula: see text]. Replacing Stearman airplanes with larger aircraft in operational spraying and associated changes in spraying procedure sometimes caused heavy fish losses even for single applications of DDT at [Formula: see text]. Experimental spraying of phosphamidon-in-water at 1 lb/acre had no apparent harmful effects on young salmon and trout.Observations at a counting fence across the Northwest Miramichi 12 miles below the lower boundary of the forested area sprayed with DDT at [Formula: see text] in 1954 showed extensive killing of suckers and cyprinids; also, the numbers of these species moving through the fence were abnormally low for several years after spraying.Wild young salmon were found dead in streams when autumn water temperatures approached freezing after June sprayings of watersheds with DDT.

Some Factors Influencing the Distributions of Brook Trout and Young Atlantic Salmon

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Responses to Light of Young Atlantic Salmon (Salmo salar) and Brook Trout (Salvelinus fontinalis)

Responses of young Atlantic salmon (Salmo salar L.) and of brook trout (Salvelinus fontinalis (Mitchill)) to different levels of illumination and to overhanging and submerged cover were compared in the laboratory. At surface illuminations between 0.4 and 160 ft-c trout were either slightly photopositive or showed no preference for light or dark areas, while salmon were photopositive. At illuminations above 300 ft-c both species were photonegative when the light area had a smooth, unbroken substrate. Under these conditions starvation induced salmon into the light, but trout remained photonegative, although slightly less so than well-fed trout. With submerged cover (plants, broken flowerpots, etc.) in the light area, salmon were strongly photopositive, while trout were photonegative. Salmon were less photopositive, but still preferred the light area, with submerged cover in both dark and light areas, in most experiments trout maintained position at the edge of the shadow caused by overhead cover, looking out into the light area from the dark.The significance of these results to habitat segregation by the two species where they are sympatric in nature is discussed.

New Methods for Reducing the Toxicity of Kraft Mill Bleachery Wastes to Young Salmon

Kraft pulp mill bleachery effluents and those from the unbleached screening operation were tested, separately and in combination in the proportions as they would exist in the main effluent of a particular mill, for toxicity to young Atlantic salmon, Salmo salar.The bleachery component from the chlorination stage, tested under neutral pH conditions, was considerably more toxic than the other components.Major reductions in the toxicity of the chlorination stage component were accomplished by treating it with small quantities of sulphur dioxide. Lesser but still appreciable toxicity reductions were observed in the whole effluent when the chlorination component was thus treated before combination with the other components.The toxicities of laboratory-produced filtrates from certain modified first-stage (chlorination) bleaching procedures were also evaluated. Notably, much less toxic filtrates resulted when substantial mixtures of chlorine dioxide and chlorine were substituted for the normal chlorine dosage in the first bleaching stage.A number of other treatments, methods, and their relative effectiveness are discussed.

Adjustment of Buoyancy in Young Atlantic Salmon and Brook Trout by Changes in Swimbladder Volume

The adjustment of swimbladder volume and the consequent effects on buoyancy in young Atlantic salmon and brook trout at various stages of development were measured in relation to current velocity. This was done by measuring pressure of neutral buoyancy — the pressure at which an anesthetized fish just reached neutral buoyancy as the total (atmospheric plus hydrostatic) pressure was gradually reduced — or by measuring flotation pressure — the ratio of volume of gas in the swimbladder to weight of the gas-free fish in water. Whether in static or flowing water, salmon parr were less buoyant than brook trout. Individuals of both species were more buoyant when held in still water than when held in rapidly flowing water. Adjustment in buoyancy took place when these fishes were subjected to a change in water current. Buoyancy was reduced if they were moved from still water to rapidly flowing water and was increased if they were moved from flowing to still water. Salmon smolts were more buoyant than salmon parr. This greater buoyancy of smolts is not owing to their being larger than parr. Initial filling of the swimbladder in salmon alevins can be delayed by subjecting them to strong water currents.

Effect of DDT on Temperature Selection by Young Atlantic Salmon, Salmo salar

Exposure of Atlantic salmon underyearlings for 24 hr to sublethal doses of DDT, ranging from 5 to 50 ppb, resulted in changes in the selected temperature. Low doses produced a downwards shift in the selected temperature whereas higher doses produced an upwards shift. The DDT effect appeared to be more marked for warm-acclimated fish (17 °C) than for cold-acclimated ones (8 °C). In addition exposure of warm-acclimated fish to 10 ppb DDT or more appeared to make them extremely sensitive to cold water and there was some evidence to suggest that the lower lethal limit may have been raised. It is suggested that DDT may interfere with the normal thermal acclimation mechanism.

Growth of Young Atlantic Salmon, Salmo salar, in the Gander River System, Newfoundland

Growth of Young Atlantic Salmon, Salmo salar, in the Gander River System, Newfoundland

Movements of Young Atlantic Salmon in a Small Stream

The locations of tagged parr and fin-clipped fry were observed from summer through early winter in a 1000-ft (328-m) study area of a small coastal stream. Tagged parr were usually found in or near places of original capture which are herein designated as homes. Parr whose homes were in pools, which appeared to be as suitable habitats as riffles, and those in adjacent riffles appeared to stay in their respective habitats. Some returned to their homes after having been moved as much as 700 ft (213 m) upriver or downriver. Fry were most numerous in shallow riffles and appeared to remain within small areas of the stream during summer but moved into parr habitats, the pools and deep riffles in autumn.

Lethal Concentrations of Copper and Zinc for Young Atlantic Salmon

The toxicity of copper and zinc sulphates to immature Atlantic salmon (Salmo salar L.) was tested in soft water.The relation between concentration of metal and survival-time could be fitted by a straight line when logarithms were used. A sharp break in this relation marked the incipient lethal level, where survival became indefinitely long. Incipient lethal levels were 48 μg/l of copper and 600 μg/l of zinc.In solutions containing both copper and zinc, fish died twice as fast as would occur if the 2 metals were simply additive in their lethal action. Resistance-times in zinc solutions were increased at pH 7.9–9.3, and results fitted the hypothesis that dissolved zinc was toxic, but not suspended zinc. Survival in a given concentration of zinc was 4 times as long at 5° as at 15 °C, and the incipient lethal level was at least 1.5 times higher, with fish acclimated to each temperature.

Territorial Behaviour of Juvenile Atlantic Salmon (Salmo Salar L.)

1. The territorial behaviour of young Atlantic salmon is described from observations made in the field and the laboratory. Six agonistic activities occur during the defence of territories; these are charging, nipping, chasing, frontal display, lateral display and fleeing. Certain colour changes of the fish are associated with extremes of aggression and submission. 2. The causation of the six agonistic acts is discussed. Charging, nipping and chasing result from high attack tendencies; fleeing is a result of high escape tendencies. Frontal and lateral displays occur as a result of conflict between attack and escape and are most common during fights between two aggressive fish when conflict is presumed to be high. Frontal display indicates relatively high levels of the tendency to attack; lateral display of the tendency to escape. 3. Agonistic behaviour among aquarium-held fish fluctuates with several factors. Territories are not defended actively until after a period of adaptation to new surroundings, particularly if the fish have been kept in crowded holding tanks for some time. Agonistic encounters increase with more frequent feeding, due probably to better condition and greater activity of the fish, resulting in more frequent infringements of territories. Gradual increase in numbers of fish in an aquarium leads first to an increase, then to a falling off in agonistic activity, as the non-territory-holding fish, which are moderately active with small numbers of fish present, form a closely-knit, stabilized group as the aquarium becomes crowded. 4. The territories of young salmon appear to be primarily feeding territories. The behaviour associated with their maintenance is important for optimum growth and survival and for maintaining position for long periods in fast flowing streams. The fate of hatchery-reared fish planted in rivers may be related to their ability to secure and maintain territories in competition with wild fish.