摘要:

Dolly Varden (Salvelinus malma) smolts were enumerated and sampled in 1967, 1968, and 1969 at Hood Bay Creek, a nonlake system on Admiralty Island, and in 1962, 1963, and 1964 at Eva Lake, on Baranof Island.Dolly Varden smolts left Hood Bay Creek from early May to late June and from early September to mid-November. At Eva Lake, a smolt migration occurred in May and June but not during the fall. Most of the smolts at Hood Bay Creek belonged to age-groups II, III, and IV and at Eva Lake to age-groups III and IV. Smolts from the two systems were similar in size, varying from 100 to 180 mm in fork length, with annual mean lengths ranging from 134 to 136 mm.Insects and fry of chum (Oncorhynchus keta) and pink salmon (O.gorbuscha) were the principal food items of Dolly Varden and coho salmon (O.kisutch) smolts sampled at the Hood Bay Creek weir in May and June. Dolly Varden smolts leaving Hood Bay Creek in the fall fed primarily on salmon eggs, whereas insects were the principal food items of smolts sampled at the Eva Lake weir.Suggestions for management of Dolly Varden are given. The number of eggs, fry, or smolts necessary to maintain a given run of Dolly Varden indicates a high return from smolts and a low return from eggs or fry. Transplanting smolts from one system to another to establish or enhance a population in a depleted system is suggested.

ISSN:0706-652X    

DOI:10.1139/f70-116

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Spawning of the lake chub,Couesius plumbeus(Agassiz), was investigated at Lac la Ronge from 1966 to 1968. Nonadhesive eggs were freely dispersed in rocky shallows in the tributary Montreal River during May and along rocky shores of the lake in late June. Temperature played a regulating role and most breeding activity occurred after the water reached 10 C. Some 4000 individuals were marked by finclipping and subsequent recaptures revealed that chubs migrated as much as 3 km in order to spawn in the river.Early arrivals in the river were cryptic. Males were somewhat aggressive during spawning but no territoriality was observed in the field. No nests were built and there was no parental guarding. Males outnumbered females on the spawning grounds and spawning activity was polyandrous. Males courted females by a combination of persistent pursuit and specially directed nudging. Sexual dimorphism was apparent in the larger pectoral fins, the more distinct dark lateral stripe, and the greater development of nuptial tubercles and orange breeding marks on males.Age-group III females made up 68% of the spawning population in 1968 and contributed 54% of potential recruitment. These fish were spawning for the first time at a mean total length of 95.1 mm. Age-groups V and over constituted 6% of the spawning females and contributed 13% of potential recruitment. The largest female captured was 147 mm total length.Certain fundamental aspects of the breeding behaviour were found to be inconsistent with that reported among established species in the genusHybopsis. Inclusion of the lake chub withinHybopsisas has been suggested by some investigators is accordingly considered indefensible.

ISSN:0706-652X    

DOI:10.1139/f70-117

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Ninety-eight percent of 5391 F1splake recovered from a 1966 planting of 49,000 yearlings in Burnt Island Bay (45°50′N, 82°57′W) on the south shore of Manitoulin Island were taken within 32 km (20 miles) of the planting site. Remaining recaptures were made at distances up to 322 km (200 miles).Growth rates of the hybrids in Lake Huron exceeded those reported for native and planted lake trout. A commercial size of 0.9 kg (2 lb) round weight was attained by the fall of their 2nd year in the lake. The splake grew rapidly through the winter months. Yearlings fed mainly on invertebrates and 2- to 4-year-olds fed almost entirely on fish.Eight percent of 3054 hybrids examined had one or more lamprey marks. Fish less than 30 cm (12 inches) bore no evidence of lamprey attack; larger hybrids showed frequencies of lamprey marks increasing from 5.4% for 30- to 40-cm fish to 11.6% for those larger than 40 cm. The incidence of fresh lamprey marks was minimal in spring and early summer and reached a peak in September when more than 20% of the specimens bore fresh marks.Of the 2- and 3-year-old splake recovered, 50 and 40%, respectively, were males. The onset of sexual maturity in both sexes occurred at age II. By age III, 86% of the males and 58% of the females were mature. Ripe 3-year-old hybrids of both sexes were captured over former lake trout spawning grounds. Fecundity of 3-year-old females averaged 2512 eggs. Although survival to age IV was low, a substantial number of the hybrids attained sexual maturity.A total of 8.4% of the planting of 49,000 yearling hybrids was reported taken by sport and commercial fisheries during a 3-year period.

ISSN:0706-652X    

DOI:10.1139/f70-118

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Evaluation of avoidance of Miller samplers towed at 8 mph indicated that avoidance began when yellow perch fry were less than 8 mm long and increased as fry grew larger. Catches were increased by increasing towing speed to 11 mph, by using an electric shocking grid in front of the sampler, by using clear and translucent rather than dark, opaque samplers, and by night sampling. A sampler with an aperture 1.5 times as large as the conventional Miller sampler was not more effective. Avoidance by walleye fry occurred, but was less well defined. Application of the results to the development of sampling techniques is discussed.

ISSN:0706-652X    

DOI:10.1139/f70-119

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Three parasites, the monogeneanUrocleidius adspectus, the copepodErgasilus confusus, and the glochidia ofLampsilis radiata, were common on the gills of the yellow perch collected from the Bay of Quinte, Lake Ontario, from May 1967 to April 1968. No correlation was found between the incidences of infestation of these three parasites. Except for the glochidia, more parasites were found on the second and third gill arches than on the first and fourth. Other records from the gills were the glochidia ofElliptio complanatus, the myxosporidianHenneguyasp., and nonparasitic mites belonging toHydrozetessp.

ISSN:0706-652X    

DOI:10.1139/f70-120

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Autoradiographs of tissues of euphausiids and shrimps fed65Zn through a food chain showed the isotope located primarily in the interstitial spaces between muscle fibers, in the eye mainly between the rhabdoms and crystalline cones of adjacent ommatidia, within the exoskeleton, and on the interior surface of the exoskeleton. Comparisons of the autoradiographic evidence with concentrations of radiozinc and stable zinc in the various dissected tissues were in good agreement. The specific areas of65Zn localization were much the same as those seen in an earlier study of similar organisms that accumulated65Zn directly from sea water; thus, it appears that65Zn, and therefore zinc, is highly labile in marine crustaceans and will accumulate in certain specific locations regardless of the mode of uptake. The rates at which various tissues became saturated with65Zn were dependent upon mode of uptake, however. Because most of the65Zn was located intercellularly, and not intracellularly, most ingested zinc apparently accumulates in excess of the animals' needs and is not used metabolically.

ISSN:0706-652X    

DOI:10.1139/f70-121

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A device is described to directly observe fish behavior beneath the ice of a shallow lake. The viewing device, a 1.9-m tall plexiglass tube (14.0 cm inside diameter) sealed at the bottom, worked on the principle of a periscope. It was frozen into place in the center of a net enclosure. A man in a darkened hut lowered a mirror into the tube to observe the fish in the enclosure.Vertical distributions and behavior of 5 adult northern pike (Esox lucius), 6 yellow perch (Perca flavescens), and 13 bluegill (Lepomis macrochirus) were compared with the levels of dissolved oxygen, free carbon dioxide, hydrogen sulfide, and water temperature. Observations in Mystery Lake, Wisconsin, were from December 29, 1968, through January 30, 1969, during a period when environmental conditions worsened beneath the ice and resulted in a winterkill.Yellow perch were the most active, northern pike the least. Bluegill remained farther beneath the ice than did the other two species. Northern pike took up residence in domes that they formed in the undersurface of the ice. Northern pike and yellow perch frequently sounded into the anoxic layers.We conclude that differences in fish behavior were significant in prolonging survival. A combination of little locomotory activity and a position immediately beneath the ice apparently favored the longer survival of northern pike over bluegill and yellow perch.

ISSN:0706-652X    

DOI:10.1139/f70-122

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The effects of large changes in hemoglobin concentration were studied in rainbow trout in fresh water between 8 and 14 C. Anemia was produced by injecting phenylhydrazine hydrochloride or by replacing blood with either saline or plasma.No significant changes were observed in the rate of oxygen consumption, arterial or venous oxygen tensions, ventilation volume, inspired and expired water oxygen tensions, or dorsal aortic blood pressure. The primary compensatory mechanism invoked was an increase in the cardiac output, which was accomplished almost entirely by increases in stroke volume. Although the viscosity of the blood was reduced, there must also be large changes in the peripheral resistance to blood flow, since greatly increased cardiac output was achieved without significant increase in blood pressure.The change in blood oxygen capacity and increase in cardiac output caused significant lowering of the ventilation–perfusion ratio, but the capacity–rate ratio of water to blood varied only a little. A small rise occurred at low hematocrit values, due to small changes in a number of parameters.The experiments illustrate what happens when blood oxygen capacity is reduced, but do not elucidate the mechanism for control of stroke output of the heart. They also indicate that a species' hemoglobin level is maintained at a level that allows cardiac output to vary over an optimal range of its efficiency curve.

ISSN:0706-652X    

DOI:10.1139/f70-123

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The August standing crop of harvestable brown trout (Salmo trutta, 90%), and brook trout (Salvelinus fontinalis, 9%) in the upper Sydenham River, Ont., was estimated at 499 trout/ha (63.2 kg/ha) during 1966 and 1967. Brown trout were of age I (68%), age II (23%), and the remainder of ages III, IV, V, and XIII. Brook trout were ages I (95%) and II only.The average annual harvest by 1501 anglers was 1135 fish (64% brown, 35% brook trout) at a rate of 0.34 fish/hr. Exploitation of the preseason standing populations of brown and brook trout was 23 and 59%, respectively. Catch per unit effort from the downriver section (all brown trout of ages II–IV and mean length of 34.0 cm) averaged 0.10 at an angling pressure of 264 hr/ha. An upriver section occupied predominantly (90%) by brown trout of age I–III and mean length of 26.8 cm yielded 0.67 trout/hr at an angling pressure of 251 hr/ha.The population structure, growth, and exploitation rate of naturalized brown trout favours its use in providing continuous angling of creditable quality in heavily fished headwater streams. Coexistence of self-sustaining populations of brown and brook trout provide a sustained, high-quality mixed fishery.

ISSN:0706-652X    

DOI:10.1139/f70-124

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Comparison of locomotor responses of blinded goldfish with those reported for normal animals on approaching the walls of an experimental tank demonstrated that although visual perception of the walls played no role in the modification of frequency distribution of size of angles of turns, it was necessary for the observed change in velocity of locomotion. Observations on fish blinded in only one eye suggested that perspective vision was required for the control of turning frequency.

ISSN:0706-652X    

DOI:10.1139/f70-125

出版商:NRC Research Press    

年代:1970

数据来源: NRC