Lake Chub Research Articles

Retinal and extraretinal entrainment action spectra for the activity rhythms of the lake chub, Couesius plumbeus

The roles of retinal, pineal, and other extraretinal photoreceptors in determining light responses and the entrainment of circadian locomotor activity rhythms were investigated with a cyprinid fish, the lake chub, Couesius plumbeus. Determinations were made of the action spectra for inducing activity responses and entraining circadian activity. In normal, intact fish entrainment occurred over 368 to 742 nm with maximal sensitivity at wavelength bands centered at 538 to 568 nm (10−6−10−4 μw cm−2). In blinded and blinded-pinealectomized fish extraretinal photoreception and entrainment was restricted to approximately 568 to 742 nm. In all cases the energy fluence rates for entraining activity were significantly greater than those required for effecting activity responses.

Multivariate analysis of hybridizing Cyprinidae from the Kananaskis Reservoirs, Alberta

Principal components and canonical variates analyses of hybridizing Couesius plumbeus (lake chub) and Rhinichthys cataractae (longnose dace) from Upper and Lower Kananaskis Reservoirs, Alberta, using 21 morphological characters, revealed two parental groups bridged continuously by an intermediate hybrid group. This morphological overlap between the hybrids and the parental species indicates that it is not always possible to positively identify "pure" parental individuals from the Kananaskis. Neither backcross nor hybrid F2 individuals could be identified from the analyses, although the Kananaskis R. cataractae showed effects suggestive of either selection or introgression, relative to known R. cataractae from widespread Alberta localities. Rhinichthys cataractae has also declined in numbers relative to C. plumbeus since last studied in 1961. Couesius plumbeus does not show similar effects suggestive of selection or introgression.

Pineal control of ultradian rhythms and short-term activity in a cyprinid fish, the lake chub, Couesius plumbeus

The role of the pineal organ in the control of ultradian rhythms and short-term activity was investigated in a cyprinid fish, the lake chub, Couesius plumbeus (Agassiz). Photoperiodically entrained and free-running circadian activity under constant darkness was composed of nonrandomly distributed short-term activity components (0.5–3.5 hr) with a significant ultradian frequency at 1.5 hr. Pinealectomy eliminated ultradian frequencies and led to a random distribution of residual short-term activity in both entrained and free-running circadian activity. These observations are considered in relation to the various hypotheses proposed for the origins and control of ultradian frequencies. It is suggested that the disruptive effects of pinealectomy occur through alterations of circadian organization and possible disruptions of circadian modulation of short-term activity.

Pineal involvement in the control of circadian rhythmicity in the lake chub, Couesius plumbeus

AbstractRemoval of the pineal organ from the lake chub, Couesius plumbeus, had significant effects on circadian locomotor activity. In fish kept in continuous darkness the absolute length of the circadian period was significantly altered; the variability of the period was increased; and ultradian rhythms were eliminated. These findings indicate that the pineal organ is involved in the control of circadian rhythmicity in this teleost fish.

Seasonal changes in the circadian period of the lake chub, Couesius plumbeus

Systematic seasonal and annual changes are present in the length of the circadian period, τ, of the lake chub, Couesius plumbeus. Maximum and minimum period values of 28.1 and 24.8 h were recorded under constant darkness from fish obtained at the times of the winter and summer solstices, respectively. There was an asymmetric annual pattern in the τ values obtained from the increasing and decreasing photoperiods of spring and fall. Annual variations in τ were relatively independent of temperature. They were interpreted as being aftereffects of natural photoperiodic entrainment. Relations of annual changes in the length of the period to models of circadian organization and entrainment are examined.

Metazoan arasites of fish from the Smallwood Reservoir, Labrador, Canada

Three‐hundred and thirty‐two fish of eight species (5 Salmo salar, 68 Salvelinus fontinalis, 32 S. namaycush, 102 Coregonus clupeaformis, 1 Prosopium cylindraceum, 107 Esox lucius, 14 Catostomus catostomus, 3 Couesius plumbeus) from the Smallwood Reservoir, Labrador, Canada, were examined for metazoan parasites, using conventional parasitological techniques.Fifteen genera of parasites were recovered (two of Monogenea, two of Digenea, four of Cestoda, three of Nematoda, two of Acanthocephala and two of Copepoda), these including seven new host records.Significant differences were noted in the prevalence of the various parasites which were common to the different species of fish examined. No differences were recorded in the parasite burden of male and female fish. There was no correlation between the number of parasite species per infected fish and host age except in the case of Salvelinus namaycush. Food items of the fish examined were also noted.

Distribution of Fish Species in Great Bear Lake, Northwest Territories, with Reference to Zooplankton, Benthic Invertebrates, and Environmental Conditions

Benthic invertebrates in Great Bear Lake are most highly concentrated in the upper 20 m. Densities between 20 and 100 m are low; below 100 m only Mysis relicta and Myoxocephalus quadricornis exist at measurable densities. All benthic organisms exhibit a high degree of patchiness.Lake trout, Salvelinus namaycush, and M. quadricornis are two species that inhabit the lake at all depths (3–400 m) and temperatures (13.2 C for M. quadricornis and 15 C for S. namaycush).Whitefish, Coregonus clupeaformis, inhabit only the bays, seldom being caught in water over 20 m deep. The distribution of whitefish is considered to be restricted mainly by the density of benthic organisms.Three species are confined to the periphery of the lake, Stizostedion vitreum, Lota lota, and Catostomus catostomus. Two species, Couesius plumbeus and Percopsis omiscomaycus, are present in the headwaters and Great Bear River but have not been able to establish themselves in Great Bear Lake. Extreme oligotrophy is considered to have had the effect of reducing species diversity.

Morphological differences between the Teleosts Couesius plumbeus (Lake chub) and Rhinichthys cataractae (Longnose dace) and their hybrids from Alberta.

Marked external and osteological differences exist between the related cyprinids Couesius plumbeus and Rhinichthys cataractae. C. plumbeus differs from R. cataractae in several external features, such as eye size and mouth shape, any one of which permits identification of individuals. C. plumbeus has postcleithral and nasal bones while R. cataractae does not. Many differences in bone shape also exist. Natural hybrids between the two species from Upper and Lower Kananaskis reservoirs, southwestern Alberta, are intermediate in the average of their external and osteological characters. Some characters in the hybrids, however, are so variable that they fall within the range of both parental species. An individual hybrid may resemble one parental species in one diagnostic character and the other parental species in another. The largest individuals known of the three forms from the Kananaskis system are hybrids.

The North and Central American Species of Rhabdochona Railliet 1916 (Nematoda: Rhabdochonidae) of Fishes, Including Rhabdochona canadensis sp.nov.

The systematics of the representatives of the genus Rhabdochona, parasitic in fishes of North and Central America, is revised. Rhabdochona cascadilla Wigdor 1918, R. kidderi Pearse 1936, R. decaturensis Gustafson 1949, R. cotti Gustafson 1949, R. ovifilamenta Weller 1938, R. milled Choquette 1951, and R. canadensis sp.nov. are considered as the valid species of this region. The first six species are redescribed and illustrated. The new species, R. canadensis, is described from the cyprinids Hybopsis gracilis (flathead chub; type host), H. plumbea (lake chub), and Rhinichthys cataractae (longnose dace) of Alberta; the latter form is characterized largely by the presence of one or two long filaments at each pole of the eggs, by 14 teeth in the prostom, by the presence of the cuticular spike at the tip of the tail, and by the character of the spicules. The species R. pellucida Gustafson 1949 is regarded as a synonym of R. cascadilla Gustafson 1949, and R. laurentiana Lyster 1940 as a synonym of R. ovifilamenta Weller 1938. Rhabdochona serrata (Wright 1879) Ko and Anderson 1969 is transferred to the genus Cystidicola as species inquirenda. The hosts and geographical distribution of the current members of the genus are reviewed. The paper is supplemented by a key for the identification of the species parasitic in fishes of North and Central America.

Breeding Biology of the Lake Chub, Couesius plumbeus, at Lac la Ronge, Saskatchewan

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 genus Hybopsis. Inclusion of the lake chub within Hybopsis as has been suggested by some investigators is accordingly considered indefensible.

ACTH EFFECT OF PITUITARY GLANDS OF PACIFIC SALMON DEMONSTRATED IN THE HYPOPHYSECTOMIZED COUESIUS PLUMBEUS

This report deals with the cytology of the interrenal and chromaffin tissue in a small freshwater cyprinid, Couesius plumbeus. As in most teleosts, in this species, too, the two components were found to be intimately associated. After removal of the pituitary, the interrenal cells showed atrophy which could be reversed by injection of pituitary extracts of Pacific salmon (Oncorhynchus tshawytscha and O. kisutch). This extract was injected intraperitoneally in a series of six doses of 0.1 ml every second day, beginning 4–6 weeks after hypophysectomy. The fish were autopsied 2 days after the last injection. Mammalian ACTH, similarly injected in six doses of 0.25 or 0.50 international units per gram weight, exerted only a doubtful effect. In view of the transitory nature of the ACTH effect in similar experiments as reported in the literature, it is suggested that the time lapse between the last injection and the time of autopsy may have been too long to detect such an effect in our fish. The chromaffin cells did not react to any of the treatments in this investigation.

Effects of gonadotropic hormones on male hypophysectomized lake chub, Couesius plumbeus.

In lake chub, Couesius plumbeus, hypophysectomy causes marked regression in the testes, suppresses the mitotic ability of the spermatogonia, completely blocks their transformation into spermatocytes, and affects the normal secretory activity of the lobule boundary cells. Spermatogenesis is largely reinitiated and secretory activity of lobule boundary cells is restored by injections of a partially purified salmon pituitary extract, by mammalian luteinizing hormone, and by crude extracts of whole pituitary of salmon. The gonadotropin responsible for testicular maturation is similar to mammalian luteinizing hormone; a factor like mammalian follicle-stimulating hormone is probably not physiologically active in this fish. Although gonadotropin is primarily responsible for gonadal maturation, other factors such as thyrotropin and somatotropin probably have a stimulatory effect by acting synergistically with the gonadotropin. The paper presents details of a technique for hypophysectomy.

CYCLICAL CHANGES IN THE TESTICULAR ACTIVITY OF THE LAKE CHUB, COUESIUS PLUMBEUS (AGASSIZ)

The cyclical changes in the activity of the testes of a teleost, the lake chub, from a north temperate latitude have been studied by histological and histochemical methods with a quantitative evaluation of the different spermatogenetic stages. The annual testicular cycle is divided into live stages and cyclical changes in the spermatogenetic activity have been related to the changing environmental factors, namely day length and water temperature. The annual cycle consists of a prolonged mitotic phase during the fall and winter, and a shorter meiotic phase during the spring. Lobule boundary cells have been examined and changes in their activity have been recorded. Continued spermatogenetic activity during spawning enables repeated spermiation, which is advantageous since the males are comparatively fewer than the females.

EFFECTS OF TEMPERATURE AND LIGHT ON THE CYCLICAL CHANGES IN THE SPERMATOGENETIC ACTIVITY OF THE LAKE CHUB, COUESIUS PLUMBEUS (AGASSIZ)

Lake chub obtained from their natural habitat, at three different periods of their annual reproductive cycle, were subjected to four combinations of photoperiod and temperature. Temperature is the major environmental factor controlling spermatogenesis. Higher temperatures (16–21 °C) promote prespermatocytal changes (proliferation of spermatogonia) and hasten or terminate spermiation in prespawning fish; low temperatures (5–12 °C) are essential for normal gonadal proliferation and formation of the primary spermatocytes. Temperature effects are not overridden by either of the two contrasting photoperiods, but at lower temperatures a definite, although slight, photoperiodic effect is evident in the terminal part of all three experiments, Photoperiod does not appear to dominate spermatogenetic processes at any stage. Evidence is presented that an endogenous rhythm of activity is also present and may be partly responsible for the timing of the various testicular changes.

Effects of Fish Introductions and Hydroelectric Development on Fishes in the Kananaskis River System, Alberta

Changes occurred in the abundance and distribution of fishes in the Kananaskis River system, Alberta, in conjunction with fish introductions and hydroelectric development. Data from surveys from 1936 to 1961 indicate the probable chronology of events.Dolly Varden (Salvelinus malma), brook trout (S. fontinalis), cutthroat trout (Salmo clarkii), and rainbow trout (S. gairdneri) decreased in abundance, probably due to the introduction of brown trout (Salmo trutta), longnose suckers (Catostomus catostomus), and white suckers (C. commersonii), to the cooling of the Kananaskis River from reservoir construction, and to sport fishing. Hybridization between rainbow and cutthroat trout was also important in the decrease of the latter species. After introduction by man, brown trout, rainbow trout, longnose suckers, white suckers, lake chub (Hybopsis plumbea), and longnose dace (Rhinichthys cataractae) greatly increased in abundance. Prior to the increase in numbers of white suckers, a reduction in the numbers of longnose suckers occurred in Lower Kananaskis Reservoir. Little change in the distribution of mountain whitefish (Prosopium williamsoni), longnose dace, and brook sticklebacks (Culaea (= Eucalia) inconstans) occurred over the 25 years. Changes in the physicochemical environment and invertebrate fauna in the reservoirs appeared to be of secondary importance to the interaction among fish in causing the changes in species abundance and distribution.

Distribution and Taxonomy of Fishes in the Mackenzie Drainage of British Columbia

New and previously published records are listed for 28 species of freshwater fishes in tributaries of the Mackenzie River in northern British Columbia. Distribution patterns are discussed for all species reaching the continental divide at the Peace River headwaters; some are restricted to one or other side, but 17 species are common to the Peace and Fraser Rivers, suggesting that mountain ranges have served as a check but not an insurmountable obstacle to postglacial expansion. Five species indigenous to the Pacific slope—Catostomus macrocheilus, Richardsonius balteatus, Ptychocheilus oregonense, Mylocheilus caurinum, and Cottus asper—have evidently penetrated to the Peace River in comparatively recent times. Three species—the flathead chub Platygobio gracilis, the trout-perch Percopsis omiscomaycus, and the spoon-head sculpin Cottus ricei—have not previously been recorded from the province. Evidence is presented that subspecific distinctions are invalid in Couesius plumbeus (Agassiz) and Lota lota (Linnaeus). Coregonus coulieri and Hybognathus hankinsoni are reported for the first time from the Mackenzie drainage.

Limnology and Trout Angling in Charlotte County Lakes, New Brunswick

Limnological conditions were studied in eight lakes ranging in area from 20 to 73 ha. and in mean depth from 2.4 to 7.0 m. Summer thermal stratification occurred in five, while three were subject to mixing throughout by winds. August mean water temperatures varied from 14.9° to 22.0 °C. Lowest mean dissolved-oxygen content was 71 per cent saturation although pronounced summer hypolimnal deficits developed in the stratified lakes. The lakes lie in a wooded area of poor soils, underlaid with granite rocks. Bicarbonate content ranged from 5.1 to 11.1 mg./l. Phosphate P was usually < 10 mg./cu. m., even in hypolimnia. Total P averaged about 15 mg./cu. m. with extremes of 5 and 34 mg. Allochthonous humic extractives coloured the waters in varying degree (5 to 59 p.p.m.). Adverse edaphic factors conditioned a low level of productivity. Desmids were qualitatively prominent in the plankton. Rooted aquatic vegetation was generally a minor feature. Dominant bottom organisms were Hyalella, Amnicola and sphaeriids in shallow and Chaoborus and chironomid larvae in deeper water. Fish fauna consisted of 18 species; at least speckled trout, eel, lake chub and banded killifish were common to all lakes.Yields of speckled trout to anglers were assessed by creel censuses. Rate of capture averaged 0.3 per rod-hour over a seven-year period. Average annual yield was 0.65 kg./ha. Trout in their third (22 cm., 130 g.) and fourth (29 cm., 263 g.) years of age made up 85 per cent of catches. Growth rates were similar in all lakes. Introduced trout contributed little unless planted at angling size and cropped within a year. The supply of young native trout was apparently sufficient to utilize full trout-producing capacities of these lakes.