Variations de la fécondité et de la structure des populations chez Bithynia tentaculata L. (Gastropoda: Prosobranchia)

1983 ◽  
Vol 61 (11) ◽  
pp. 2417-2423 ◽  
Author(s):  
B. Vincent ◽  
M. Gaucher
Keyword(s):  
Growth Rate ◽  
Population Structure ◽  
Sexual Maturity ◽  
Temporal Variations ◽  
Bithynia Tentaculata ◽  
Poor Recruitment ◽  
One Year ◽  
Iteroparous Species ◽  
St Lawrence River

In 1982, we studied three populations of the snail Bithynia tentaculata living in a cold environment in the upper estuary of the St. Lawrence River (Quebec), with particular emphasis on the population structure and the fecundity of the different generations. This and other studies show that large variations can occur in the age of sexual maturity from year to year; these are caused by variations in the growth rate and could cause important changes in the growth rate of the populations. Also, there does not appear to be an adequate mechanism to compensate poor recruitment in one year and thus an unbalance in the population structure can be seen for at least 7 years. Fecundity varies from one population to another and from one year to the next. Differences are greater between populations, but both phenomena often interact. These results show the relevance of long-term observations, still quite rare, in order to interpret spatial and temporal variations in the bionomics of iteroparous species.[Journal translation]

Variations inter-populations de la structure d'âge et de la croissance du Prosobranche Bithynia tentaculata L.

1985 ◽  
Vol 63 (6) ◽  
pp. 1345-1353 ◽  
Author(s):  
B. Vincent ◽  
C. Létourneau
Keyword(s):  
Age Structure ◽  
Sexual Maturity ◽  
Abiotic Factors ◽  
Temporal Variations ◽  
Population Densities ◽  
Bithynia Tentaculata ◽  
Spatio Temporal ◽  
Sudden Decrease ◽  
Velocity Water ◽  
St Lawrence River

The main variations in age structure and growth of different generations were studied in 25 populations of the prosobranch Bithynia tentaculata in the St. Lawrence River (Québec). The general unbalanced age structures of the populations reflect a low recruitment encountered during an odd year because of a general disturbance in the environment. The age structure is correlated to temperature, sediments, and current velocity. Water chemistry is largely responsible for the spatial variations in lengths of the adults, but these variations do not seem to influence the age at sexual maturity. Population densities may be regulated by an increase in the growth rate of young which would reduce the age at sexual maturity in populations with low densities; this mechanism would, however, be of little use to compensate a sudden decrease in density or an unbalanced age structure in a population. These results and those of previous studies on this species reveal the important role played by abiotic factors in regulating the spatio-temporal variations of the demographic profile of this prosobranch which possesses a high phenotypic plasticity.[Journal translation]

Cycle de développement, croissance et production de Pisidium amnicum (Mollusca: Bivalvia) dans le Saint-Laurent (Québec)

1981 ◽  
Vol 59 (12) ◽  
pp. 2350-2359 ◽  
Author(s):  
B. Vincent ◽  
G. Vaillancourt ◽  
N. Lafontaine
Keyword(s):  
Population Dynamics ◽  
Sexual Maturity ◽  
Dry Weight ◽  
Mortality Rates ◽  
The Other ◽  
Annual Production ◽  
Bithynia Tentaculata ◽  
The Mean ◽  
Total Dry Weight ◽  
St Lawrence River

The population dynamics of Pisidium amnicum have been studied in one population of the St. Lawrence River over a 2-year period during which 19 samples were taken. The species can live up to 3 years and it is iteroparous; individuals generally attain sexual maturity after 1 year and they reproduce twice, once at 2 and once at 3 years of age. In adults, mortality is lower in winter than during the rest of the year and mortality rates are twice as high during the 1st year than during the 2nd year. Total dry weight (PT, in milligrams) is related to maximum length (L, in millimetres) according to the equation PT = 0.0283∙L3,80 and flesh dry weight (PC, in milligrams) is related to length as follows: PC = 0.007∙L3,18. The annual production to mean biomass (P/B) ratio is 1.4, the mean annual production being 1.298 mg/m2 of total dry weight and 107 mg/m2 of flesh weight. Comparing these results with those obtained for the gastropod Bithynia tentaculata in the same environment and at the same period of the year has shown that the growth of Pisidium amnicum is far less influenced by the temperature regime than that of the other species and that its production is at least 10 times lower.

Body growth and its implications in population dynamics of Acanthodactylus erythrurus (Schinz, 1834) in the Eastern Iberian peninsula

2019 ◽  
Vol 40 (3) ◽  
pp. 305-312
Author(s):  
Robby Marcel Drechsler ◽  
Juan Salvador Monrós
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Statistical Significance ◽  
Growth Curves ◽  
High Statistical Significance ◽  
General Data ◽  
One Year ◽  
Best Fit ◽  
Logarithmic Growth

Abstract We calculated growth rate for the spiny-footed lizard (Acanthodactylus erythrurus) inhabiting coastal eastern Spain from long-term mark-recapture data. Growth curves differ between sexes, with males growing faster than females and achieving larger size maximums. In this population each sex reaches maturity at about 300 days of age, approximately 34% faster than males, and 28% faster than females studied in a population further south and west in Iberia. Our logarithmic growth model has an accuracy of 96.8% and high statistical significance ( for males and for females). Although both the exponential curve of “best fit” for growth estimated for males (), and the linear curve of “best fit” estimated for females () in a population from Cádiz (Busack and Jaksic, 1982) are also significant. The overlap between growth curves and the general data cloud of the population showed that at the end of the year the proportion of individuals younger than one year was 80% and the proportion of individuals older than one year was 20%. Our data, in agreement with calculated maximum life spans for males (1.9 years) and females (2.1 years) in Cádiz, suggest a life span of approximately two years for both sexes. Females seem to reproduce only in a unique season in their lives, at this locality, as in Cádiz (Busack and Klosterman, 1987) they likely lay only one clutch, whereas females in Morocco (Bons, 1962) may produce two.

Cycle de développement, croissance, effectifs, biomasse et production de Bithynia tentaculata L. (Gastropoda : Prosobranchia) dans le Saint-Laurent (Québec)

1981 ◽  
Vol 59 (7) ◽  
pp. 1237-1250 ◽  
Author(s):  
B. Vincent ◽  
G. Vaillancourt ◽  
M. Harvey
Keyword(s):  
Life Cycle ◽  
North America ◽  
Reproductive Strategy ◽  
Sexual Maturity ◽  
Individual Growth ◽  
Bithynia Tentaculata ◽  
St Lawrence River

The life cycle of Bythinia tentaculata has been studied over a period of 2 years in five localities of the freshwater estuary of the St. Lawrence River. Sexual maturity is attained after 2 years and the species is iteroparous; this might prove to be a particularly advantageous reproductive strategy in this river. The main phases of individual growth are related to age and thermal variations of the water and they occur during the months of May, June, and July of the first 2 years. Eggs are laid once a year and growth stops during winter for about 6 months. These results on the life cycle and growth of B. tentaculata, particularly in the fluvial section of the St. Lawrence River, are more similar to those obtained in Europe than to those obtained elsewhere in North America. Numbers, biomass, and production are markedly higher here than the values found by other investigators on the same species.[Journal translation]

scholarly journals The effects of long-term translocation on population genetic structure of Ayu in Japan: Management implications for a recreationally fished iconic species

2021 ◽  
Author(s):  
Shuichi Kitada
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Genetic Structure ◽  
Population Genetic Structure ◽  
Population Genetic ◽  
Recreational Fishing ◽  
Plecoglossus Altivelis ◽  
In The Wild ◽  
One Year

Ayu (Plecoglossus altivelis altivelis), an important freshwater fisheries resource and popular recreational fishing species, lives for only one year and has a single breeding season. To supplement increased recreational fishing demand, huge numbers of wild–born landlocked juvenile Ayu have been translocated from Lake Biwa into most Japanese rivers for more than 50 generations. Hatchery-born amphidromous fish (including amphidromous and landlocked form hybrids) have also been released for many generations. Hatchery–born fish have low survival and maladapted behaviour in the wild. Landlocked and amphidromous forms of Ayu easily hybridise, but survival of progeny of landlocked forms is very low in seawater. Repeat backcrossing may cause introgression of landlocked forms into amphidromous populations, but this has not been previously identified. Study objectives using genetic data from Ayu from 118 locations throughout the distribution of this species in Japan are to describe contemporary population structure, genetic diversity, and admixture proportions of Ayu forms in populations, and to evaluate how human-induced translocation has affected population genetic structure. The analyses of published genotypes of 12 microsatellite markers provide strong evidence for very high gene flow between populations, but population structure has been retained in several regions, and several populations are nested. Genetic diversity is surprisingly homogeneous. Hybridisation between landlocked and amphidromous forms has occurred in all populations, with a mean hybrid proportion (± standard deviation) of 37 ± 10%, ranging 15%–60%. Results are discussed in relation to the conservation and management of this species. Recommendations are made to reduce translocation and hatchery releases, by establishing rivers and/or areas in every prefecture where translocation does not occur. Release of juveniles is of value for short–term management objectives, but management of spawning escapements, and improving the spawning and nursery habitat are important for this species long–term sustainability.

Resource quality controls detritivore consumption, growth, survival and body condition recovery of reproducing females

2014 ◽  
Vol 65 (10) ◽  
pp. 910 ◽  
Author(s):  
Aitor Larrañaga ◽  
Ana Basaguren ◽  
Jesús Pozo
Keyword(s):  
Growth Rate ◽  
Population Structure ◽  
Protein Content ◽  
Body Condition ◽  
Secondary Production ◽  
Biomass Growth ◽  
Dissolved Nutrients ◽  
Resource Quality ◽  
Consumption Growth ◽  
Iteroparous Species

Although the effect of resource quality on density, biomass, growth rate and secondary production of consumers has been frequently documented, the direct repercussion of resource quality on reproduction has been less investigated. Here we tested the hypothesis that resource quality can limit body-condition recovery of reproducing individuals. For this, we reared ovigerous females of the freshwater amphipod Echinogammarus berilloni in the laboratory and fed them with leaves differing in quality (native Alnus, Quercus, or the exotic Eucalyptus) conditioned in three streams differing in the concentration of dissolved nutrients. Both consumption and growth rate, as well as the length-corrected mass and protein content of females after the release of the eggs, were negatively related to the C : N and C : P ratios of the resource. Survival was significantly lower with the exotic eucalypt leaf litter compared to native alder and oak, a result likely explained by the toxicity of the leaves. The conditioning of the leaves in the different streams did not affect the measured variables, although it interacted with survival. The present study suggests that resource quality can affect the recovery of body condition of reproducing females and shape the population structure of iteroparous species.

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