摘要:

By infusing various natural waters into noses of homing salmon (Oncorhynchus tshawytschaandO.kisutch) and recording electroencephalographic (EEG) patterns from the olfactory bulb, data were collected showing responsiveness to waters along the freshwater migratory route. The largest responses always were evoked by the home water for each of the three spawning groups. Generally, the responses to various waters along the migrating route were equivalent, or did not vary in any recognizable progression. Accordingly, it does not seem that homing salmon are following a single olfactory clue in increasing concentration. Instead, they appear to be responding olfactorily to individual loci along the route.

ISSN:0706-652X    

DOI:10.1139/f69-197

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The horizontal distribution of planktonic crustaceans was determined in Lake Ontario at monthly intervals from June to October 1967, based on net hauls from 50 to 0 m at 32–62 stations. A separate study conducted over a 24-hr period at one station showed that on the average 90% of the zooplankters occupied the 0–50-m stratum through which the net was hauled. Eleven species of copepods and 11 species of cladocerans were found. The most abundant forms wereCyclops bicuspidatus thomasi,Daphnia retrocurva,Bosmina longirostris,Bosmina coregoni coregoni,Tropocyclops prasinus mexicanus, andCeriodaphnia lacustris. Most species appeared in the collections during June–July in the eastern part of the lake with abundance patterns later moving westward, contrary to the general movement of wind and water. At the time of maximal population density there was a strong positive correlation between zooplankton abundance and heat content of the water column from 0 to 25 m. The eastern part of the lake averaged 1.7 times more specimens/cm2than the western part of the lake. Upwelling was responsible for low numbers of zooplankters along the northwestern shore. Abundance patterns similar to generalized current flows were observed in the northern and southern parts of the lake. Flow from the Niagara River was associated with increased abundance of zooplankters in spring and summer, but decreased abundance in autumn. A detailed study of the abundance and distribution of zooplankton offshore from Toronto Harbour showed that harbour water does influence zooplanktonic populations in the vicinity. Temperature and depth of the epilimnion as influenced by the general direction of wind motion were key factors in understanding the zooplanktonic community of Lake Ontario.

ISSN:0706-652X    

DOI:10.1139/f69-198

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In laboratory tests, brown trout were most active between dusk and dawn from spring to autumn, but the percentage of the total activity that occurred during daylight was higher in the summer than in the other two seasons. Analysis of the variation in the weight of stomach contents during 24 hr in the three seasons showed a higher peak in weight at noon in summer than in the other seasons. The difference was related to an increased consumption of material of terrestrial origin, which other work showed to be most available to the fish between 09.00 and 12.00 hr. No relationship was found between the times of maximum occurrence of benthic and emergent items in the stream and of their consumption by trout. The increase in daytime activity during the summer was also evidently related to increased consumption of terrestrial material.

ISSN:0706-652X    

DOI:10.1139/f69-199

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In the spring and summer of 1965, 26 white bass,Roccus chrysops(Rafinesque), were displaced to open water on Lake Mendota, Wisconsin, and their paths traced by means of ultrasonic transmitters carried in the stomachs of the fish and receiving gear located on boats. Seventeen fish captured by fyke nets on their spawning ground were displaced 1.6 km west-southwest to a mid lake release point. Two months after the spawning season nine fish, captured by hook-and-line, were displaced 3.1 km east-northeast from their capture area to the same release point. The mean tracking time for all 26 fish was 7.31 hr.Both the spawning and nonspawning fish maintained steady courses over long distances, and both groups showed a distinct directional preference for the eastern half of the lake where the spawning grounds are located. This open-water orientation helps explain the rapid homing performance, observed in previous experiments, of displaced spawning white bass, and also demonstrates that white bass possess mechanisms for orienting to directional cues present in their natural environment.Water currents, wind-generated surface waves, and the sun were examined as possible directional cues used by the fish. Although there was some evidence supporting the use of each of these cues, the problem of orientation mechanisms remains obscure. It was determined, however, that the observed movements of the fish cannot be explained as simply passive drift by the water currents.

ISSN:0706-652X    

DOI:10.1139/f69-200

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Organophosphate poisoning in fish and mammals has always been associated with the inhibition of acetylcholinesterase in both neuromuscular and brain tissues. This inhibition resulted in the apparent death of the organisms by asphyxia. Rarely have other effects been reported.In the present study, 1-inch rainbow trout larvae were treated for 16 hr with from 10 to 100 ppm Dylox, or for 40 hr with 5 ppm. This treatment produced a marked acetylcholinesterase inhibition that was reflected by their abnormal behaviour patterns. Histological examination revealed pathological changes in the heart, liver, blood cells, pseudogills, and muscular tissues; this pathology could not be explained on the basis of acetylcholinesterase inhibition.

ISSN:0706-652X    

DOI:10.1139/f69-201

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

White whales,Delphinapterus leucasPallas, were tagged in the estuary of Seal River, Man., in western Hudson Bay in the summers of 1967 and 1968. Seven hundred harpoon tags were applied to the dorsal part of the body while chasing the animals, and 118 Petersen disc tags through the dorsal ridge after stranding the animals in shallow water on a falling tide. Three recovered harpoon tags include one observed on a living whale at the same site after a year, and two taken from netted whales at fisheries northward along the western coast of Hudson Bay, 300–800 km from the site of tagging and 5–7 weeks after tagging.

ISSN:0706-652X    

DOI:10.1139/f69-202

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The white whale or beluga (Delphinapterus leucasPallas) has been found wintering in the numerous open leads adjacent to small islands in James Bay. The spacing of the islands apparently allows year-round open water through tidal and wind action in the narrow channels.

ISSN:0706-652X    

DOI:10.1139/f69-203

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Although ciguatoxin, prepared from the liver and flesh of the moray eelGymnothorax javanicus, is an in vitro anticholinesterase, it has not been found to be an in vivo anticholinesterase. Respiratory failure and death due to ciguatoxin is not a function of cholinesterase inhibition as previously speculated, although the toxin may have a widespread action at cholinergic junctions.

ISSN:0706-652X    

DOI:10.1139/f69-204

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Yellowtail rockfish (Sebastodes flavidus) aggregated along the southern edge of the Astoria Canyon, probably in response to the increased availability of mesopelagic food. The myctophidStenobrachius leucopsaruswas the dominant food organism.

ISSN:0706-652X    

DOI:10.1139/f69-205

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Infection of two English sole,Parophrys vetulus, probably byGlugea hertwigi, is described. NumerousGlugeacysts (xenomas), measuring 0.5–1.0 mm in diameter, were located throughout the entire intestine distal to the stomach and including the pyloric caecae. A few cysts were located in the mesentery, pancreas, and liver. Microscopically, the cysts were composed of a hyaline connective tissue capsule, enclosing an intermediate layer of syncytium and a central mass of mature spores.

ISSN:0706-652X    

DOI:10.1139/f69-206

出版商:NRC Research Press    

年代:1969

数据来源: NRC