摘要:

The routine of resting oxygen consumption of Arctic char (Salvelinus alpinus) from a high arctic lake (74°42′N) was measured at 2 (acclimated) and 6 C (unacclimated). The oxygen uptake versus wet weight relation at 2 C was: Log O2uptake = 0.7316 Log weight – 1.0944. Oxygen uptake was low, not showing any evidence of "cold adaptation," and was comparable to projections of oxygen uptake versus temperature relations of other salmonid fish from lower latitudes.The short term metabolic response to a rise in temperature of 4 C was independent of body size except with fish with yolk sacs and weighing less than 0.125 g.

ISSN:0706-652X    

DOI:10.1139/f73-128

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Movements of single goldfish (Carassius auratus) were monitored in a free choice situation comprising zones of laboratory water or copper-containing water (0.010 ppm as CuCl2) each at two temperatures, 21.1 ±.1 and 21.5 ±.1 C.Fish entered the copper zone at 21.1 C significantly less frequently and spent less time there per entry as compared to the noncopper zone ("avoidance" behavior). The copper zone at 21.5 C became significantly "attractive" to the fish in terms of both frequency of entry and time spent.In the same terms, laboratory water at 21.5 C was "attractive" to the fish but became significantly more so in the presence of copper ions at the concentration of 0.010 ppm.

ISSN:0706-652X    

DOI:10.1139/f73-129

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Description of, and keys to, 10 species ofLepeophtheirus(Copepoda:Caligidae), parasitic on fishes of British Columbia, are given. Diagnostic value of different morphological details is discussed. Nine of the species included were previously known (L.bifidus,L.breviventris,L.hospitalis,L.nanaimoensis,L.parvicruris,L.parviventris,L.paulus,L.pravipes, andL.salmonis) and one is described for the first time (L.oblitus).

ISSN:0706-652X    

DOI:10.1139/f73-130

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Observations by SCUBA in Georgian Bay and Algonquin Park, Ont., indicate fish have specific habits of diurnal, crepuscular, and nocturnal activity in freshwater lakes. Of 21 species investigated, 17 either schooled or aggregated in the daytime, but only one (Osmerus mordax) schooled at night. The number of fish apparent at night in shallow water was greater than in the daytime primarily because of the influx of offshore species and lack of cover for resting diurnal species. Color changes parallel those reported in tropical oceans; at night a barred or mottled pattern was assumed by some fish resting on the bottom and bold daytime horizontal patterns faded. The parallel evolution of these color patterns in fresh and salt water suggests a strong evolutionary pressure for prey animals to disguise body shape when at rest at night, and that bold color patterns are disadvantageous when swimming at night.

ISSN:0706-652X    

DOI:10.1139/f73-131

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Lobster’s feeding response to cod and lobster muscle extracts is temporarily eliminated by satiation with flounder. Satiated lobsters respond to water from tanks containing other lobsters except that from intermolt females. Dilute urine from molted lobsters is stimulatory to satiated males; otherwise, urines cause little or no response. The responses by satiated animals are presumed to be social. Rather than a sex specific response only, there appears to be a general chemical communication among lobsters, mediated by a pheromone or pheromones.

ISSN:0706-652X    

DOI:10.1139/f73-132

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Data collected from 1954 to 1971 show that the recent decline in Miramichi River Atlantic salmon (Salmo salar) abundance has been accompanied by changes in the ratio of grilse to large salmon (2-sea-years and older) entering the river. From 1954 to 1962 trap samples were composed of about equal numbers of grilse and large salmon. Since 1963 the grilse catch has averaged 87%. Large declines in abundance of the fall-run grilse portion of the spawning stock occurred in 1968 and similar declines occurred in the fall-run large salmon component in 1969. An increase in commercial fishing mortality of large salmon is believed responsible for shifting the river escapement in favor of grilse. The result has been a reduction in reproductive potential and declines in the fall-run stocks of both large salmon and grilse.

ISSN:0706-652X    

DOI:10.1139/f73-133

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A model is developed to describe the risk of aquatic prey to visual predators in general, and is evaluated with particular reference to rainbow trout (Salmo gairdneri). The equation system uses several principles of visual mechanics to determine predation rates and therefore requires statistics on the physical properties of the food resource, besides the visual acuity and other searching constraints of the predator.Application of the model to an independent set of field data accounted for 47% of the seasonal variation in the occurrence of four benthic invertebrate prey in the diet of trout from Marion Lake, B.C. Considerably better agreement — 70% of the variation — was obtained using a three prey system. Sequential comparisons between the predicted and observed pattern of predation suggest that prey activity, prey exposure, prey density, and prey size are four of the major determinants of prey risk in benthic food chains.

ISSN:0706-652X    

DOI:10.1139/f73-134

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Embryonic development of lake herring (Coregonus artedii) was observed in the laboratory at 13 constant temperatures from 0.0 to 12.1 C and in Pickerel Lake (Washtenaw County, Michigan) at natural temperature regimes. Rate of development during incubation was based on progression of the embryos through 20 identifiable stages.An equation was derived to predict development stage at constant temperatures, on the general assumption that development stageis a function of time (days, D) and temperature (T). The equation should also be useful in interpreting estimates from future regressions that include other environmental variables that affect egg development.A second regression model, derived primarily for fluctuating temperatures, related development rate for stage, expressed as the reciprocal of time, to temperature (x). The generalized equation for a development stage is:In general, time required for embryos to reach each stage of development in Pickerel Lake agreed closely with the time predicted from this equation, derived from our laboratory observations. Hatching time was predicted within 1 day in 1969 and within 2 days in 1970.We used the equations derived with the second model to predict the effect of the super-imposition of temperature increases of 1 and 2 C on the measured temperatures in Pickerel Lake. Conceivably, hatching dates could be affected sufficiently to jeopardize the first feeding of lake herring through loss of harmony between hatching date and seasonal food availability.

ISSN:0706-652X    

DOI:10.1139/f73-135

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Calanus plumchrusdid not feed during the last 7 months of its life cycle and the fecundity of each female was dependent on the size of the animal. Each female produced an average of 535 eggs from 9.5 broods over a breeding period of 85 days. Eggs were released in water deeper than 300 m and were calculated to move towards the surface about 26 m/day. Growth from egg to stage V took about 100 days. Growth rate was calculated to be 10.6%/day.

ISSN:0706-652X    

DOI:10.1139/f73-136

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The selectivity of gillnets is usually estimated "indirectly" from comparisons of catches by two or more mesh sizes, assuming that the selectivity curves for all meshes have the same shape and amplitude. We estimated selectivity "directly" by fishing marked walleye (Stizostedion vitreum vitreum) with gillnets of(3.81–11.43-cm) mesh. The selectivity curves were bimodal but each could be resolved into two unimodal components representing fish caught by wedging and tangling, respectively. We fitted the selectivity of each mesh to a pair of Pearson’s Type I curves. As the mesh size increased, amplitude of the selectivity curves increased rapidly and tangling occurred over a progressively narrower range of (fish girth)/(mesh perimeter) ratio. Our estimates agreed with data from four out of seven other gillnetting studies, indicating a wider applicability but also a need to consider additional variables or to standardize fishing methods. Because the assumption of equal amplitudes is not realistic, the indirect methods overestimate selectivity curves on the left and underestimate them on the right.

ISSN:0706-652X    

DOI:10.1139/f73-137

出版商:NRC Research Press    

年代:1973

数据来源: NRC