摘要:

The Mink and Valley rivers, Manitoba, contain two sympatric species of dace (Cyprinidae:Rhinichthys). These fishes, although interfertile, have never been reported to hybridize in nature.Seasonal isolation is only partially developed, since overlap in time of spawning exists. During spawning, adults of the two species tend to occupy different habitats, the Great Lakes longnose daceRhinichthys cataractae cataractaebeing most abundant in water velocities faster than 45 cm/sec and the western blacknose daceR.atratulus meleagrisin water velocities less than 45 cm/sec; but some overlap exists. However, the place of spawning of the two species is distinctly different. Nests of longnose dace were found in water velocities exceeding 45 cm/sec with large stones, whereas nests of blacknose dace were found in slower water velocities in gravel. The patterns of spawning behaviour of these two cyprinids reveal marked differences and obvious incompatibilities. Males of both species actively defend territories prior to spawning but show distinct preferences for conspecific females over other females. Observations further indicate that females are receptive only to patterns of courtship behaviour shown by males of their own species.The combination of different places of spawning and patterns of behaviour is considered to be a powerful barrier to hybridization.

ISSN:0706-652X    

DOI:10.1139/f70-242

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The changes in population density and individual size distribution in a population of the trumpet wormPectinaria hyperboreaMalmgren were observed on eight occasions in 20 months at a station 60 m deep on a soft muddy substrate in St. Margaret's Bay, N.S. Production proceeded rapidly during the early life stages while loss due to mortality (elimination) was low, so that biomass increased and reached a maximum at 170 days. Between 30 and 370 days the rate of elimination was nearly constant at about 0.9 g/m2wet weight per 50-day period in spite of changing biomass. After 370 days the rate of production, rate of elimination, and biomass decreased. It was estimated that 80% of mortality was due to predation. Almost 90% of total production of the cohort took place in the first year of life. The ratio between annual production and biomass present in May 1967 in the study area was used to estimate annual production at 24 stations in the bay.

ISSN:0706-652X    

DOI:10.1139/f70-243

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

In Newfoundland waters, shorthorn sculpins,Myoxocephalus scorpius(L.), live to age 15 and attain a maximum size of just over 50 cm. The growth rates of males and females are little different below age 4, but above age 4 the females grow faster than the males, and the difference between average length-at-age for males and females gets progressively larger with age. Males mature at a younger age and at a smaller size than females. In any age-group where there are mature and immature individuals the mature ones are larger.

ISSN:0706-652X    

DOI:10.1139/f70-244

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Brachiella lageniformis, hitherto known only from the Atlantic coast of Argentina, was found off the east coast of Vancouver Island, on the gills ofMerluccius productus. Both male and female are described and illustrated in detail. The significance of this find for Szidat's views on the origin of the genusMerlucciusis discussed. A proposal is made to suppress the genusParabrachiellaand to place all its five species (P.rostrata,P.insidiosa,P.australis,P.spinicephala, andP.incurva) in the genusBrachiella.

ISSN:0706-652X    

DOI:10.1139/f70-245

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Starch-gel electrophoretic characteristics of the hemoglobins, muscle myogens, serum transferrins, and serum esterases from two species of mouth brooders,T.mossambicaPeters andT.hornorumTrewavas, and two species of substratum spawners,T.zilliiGervais andT.melanopleuraDumeril, are described in detail. The mobility characteristics of lactate dehydrogenases (LDH) from 11 tissues of these four species are also described.The two mouth brooders possess virtually identical LDH zymograms, whereas the unique mobility difference of the skeletal muscle type subunit distinguishesT.zilliifromT.melanopleuraand from the two mouth brooders. The LDH subunit specific for the eye tissue comprised the major diagnostic feature distinguishing the mouth brooders and the substratum spawners.No mobility differences in serum esterases were found between the two substratum spawners, whereas the mouth brooders did possess different mobilities.Tilapia mossambicapossessed a single serum transferrin zone, andT.hornorumone major and one minor zone.The hemoglobins and muscle myogens completely separated all four species ofTilapiaindicating that these are the protein groups of choice as diagnostic tools in their identification. These proteins are likewise sufficiently diagnostic to point out that the specimens ofT.mossambicaand particularlyT.hornorumused in these studies were not always biochemically uniform, emphasizing their further value in the selection of parental stocks for breeding purposes. The need for new approaches such as these for supplementing the classical morphometric techniques in fish farming is outlined.

ISSN:0706-652X    

DOI:10.1139/f70-246

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The preparation and properties of the bis-Girard P derivative of canthaxanthin are described and its surfactant character demonstrated with respect to the formation of an electrostatically stabilized complex with ovalbumin.

ISSN:0706-652X    

DOI:10.1139/f70-247

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Pathological changes attributable to cadmium poisoning were observed in the intestinal tract, the kidney, and the gills ofFundulus heteroclitusafter exposure to 50 ppm of the metal. Microscopic examination revealed pathological changes of the intestinal tract as early as 1 hr after exposure, in the kidney after 12 hr, and in the gill filaments and respiratory lamellae after 20 hr. These manifestations of cadmium poisoning bear resemblance to the pathological changes that have been demonstrated clinically and experimentally in mammals.The examination of circulating blood elements revealed rapid and striking changes among cells of the eosinophil lineage. The abundance of eosinophils increased steadily to a level approximately 45% above the usual amount. Indications of the cellular increase occurred as an early rise 4 hr after exposure.A reduction in the relative numbers of mature eosinophils was evident in imprints of head kidney tissue. Nuclear anomalies were associated with the thrombocytes of specimens after 8 hr exposure; however, these changes were not noticeable at either earlier or later time periods.

ISSN:0706-652X    

DOI:10.1139/f70-248

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Among the fertilized eggs arising from a series of intraspecific and interspecific crosses involving sockeye, pink, and chum salmon, time from fertilization to hatching was longest for crosses involving sockeye males, less for those involving pink males, and least for those involving chum males. For crosses of females of the three species with males of a single species, eggs from pink females took longest to hatch, those from sockeye females took less time, and those of chums took the least. Larva size at hatching was greatest for larvae emerging from chum eggs, irrespective of male parent, less for those emerging from sockeye eggs, and least for those from pink eggs. There were only small differences in the size of larvae at hatching from the eggs of females of one species that had been fertilized by males of each of the three species. Among the pre-hatched embryos developing in eggs of a single species, those with a sockeye male parent grew slowest, those with a pink male parent grew faster, and those involving a chum male parent fastest. In eggs from females of the three species fertilized by the males of one species, embryos in eggs of chum females grew fastest, those in eggs of sockeye females slower, and those in eggs of pink females slowest. Gross malformation among hybrid offspring was not pronounced — only chum male × sockeye female and chum male × pink female hybrids displayed markedly greater proportions of malformed individuals than did the combined intraspecific crosses involving the same parents. It is possible that observed differences in time from fertilization to hatching between eggs of different parental origin are brought about by the interaction of growth rates inherited mainly from the male parents and a critical embryo size related to the size of eggs of the female parent. Identification of parental determinants of early development of salmon should make it possible to create salmon forms capable of exploiting new or changed environments.

ISSN:0706-652X    

DOI:10.1139/f70-249

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Regular research vessel surveys in Trinity Bay, Nfld., during 1967–68 indicated that significant biological changes occurred in coastal capelin from the over-wintering to the spawning period. During their over-wintering period in February–March mature capelin had a high fat content, a low feeding intensity, a low nematode incidence, and were heavy at length. The gonads were in a resting stage, secondary sexual characteristics were absent, and the sexes were integrated. During the prespawning period in April–May the feeding intensity increased and the gonads and secondary sexual characteristics began to develop, whereas the fat content declined. At this time the schools were segregated by sex. By the start of the spawning season in mid-June the capelin had ceased feeding, the fat content was low, and the weight at any particular length was less than that during the over-wintering period. The incidence of nematodes was high and the sexes were readily distinguished by the conspicuous secondary sexual characteristics. These changes are discussed in relation to the seasonal distribution pattern of coastal capelin in Trinity Bay and the feasibility of a commercial fishery.

ISSN:0706-652X    

DOI:10.1139/f70-250

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Endrin incorporated into the diet of mature male goldfish for 3–4 months affected growth, gonad development, thyroid activity, serum characteristics, total and differential body fat, behavior, and mortality. A biphasic response to endrin dosage was characteristic. The low doses (4.3–43 μg/kg body weight per day) either caused no detectable effect or were stimulatory, as seen from increased rates of growth and higher total body fat contents. The two highest doses (143 and 430 μg) caused mortality, lowered growth rates, and other chronic symptoms of endrin intoxication; they also caused decreased thyroid cell heights, decreased gametogenesis, and lowered total body fat, as well as less vacuolization in liver cells.All doses except the highest caused elevated serum Na concentrations. The fish receiving the highest dose suffered osmoregulatory failure. Induced spermiation was not affected; fish receiving 143 or 430 μg/kg had greatly reduced, but functional testes.

ISSN:0706-652X    

DOI:10.1139/f70-251

出版商:NRC Research Press    

年代:1970

数据来源: NRC