Estimation of population parameters by optimizing catch effort allocation

1. In this study, we have developed a new method to estimate population parameters and applied it to a concrete example on the situation that there are two fisheries resources which are depleted only by catch, and that these two resources are not caught equally because of the difference of prices.
2. Switching function, which is originally used to describe the effort allocation that one predator eats two preys, has been introduced. We have constructed a model of fishery in which each fisherman pursues economical optimum.
3. The population size of two species at the beginning of the fishing season, catchability coefficient and parameters of switching function are estimated by the criterion of minimum error sum of squares between CPUE (catch per unit effort) of data and that by model.
4. We have applied it to the diver fishery of abalone in Ojika Island, Nagasaki Prefecture. The model describes well the situation during the season that CPUE of the less expensive species increases gradually as the population of the other species is depleted.

     

A simulation study of population interaction between the greenhouse whitefly,Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) and the parasitoidEncarsia formosa Gahan (Hymenoptera: Aphelinidae) II. Simulation analysis of population dynamics and strategy of biological control

Simulation studies were performed to analyze factors affecting the population dynamics of the system with the greenhouse whitefly (Trialeurodes vaporariorumWestwood ) and the parasitoid Encarsia formosaGahan and to develop strategies for the introduction of E. formosa. The reduction of parasitization efficiency with an increase in parasitoid density promotes the stability of the system, which coincides with the prediction from current theory. The stability of the system is also shown to be promoted by the effect of host feeding. The population levels of the system are remarkably suppressed with an increase in searching efficiency and a decrease in host oviposition. The control effect of the parasitoids is enhanced when the number of parasitoids is divided among many introductions. An optimal time, an optimal density ratio of parasitoids to hosts and optimal densities of hosts and parasitoids exist in the introduction programme of parasitoids.     

The dynamics of laboratory populations ofCallosobruchus chinensis andC. Maculatus (Coleoptera: Bruchidae) in patchy environments

Experiments are described showing the long-term dynamics of two species of bruchid beetles (Callosobruchus chinensis and C. maculatus) in arenas in which the resource of 50 black-eyed beans is divided between 5, 10 or 50 ‘patches’. Both species of adult beetles exhibit clumped distributions between patches. Within a patch there is a tendency for a density dependent reduction in (1) eggs laid per female, (2) the proportion of eggs hatching per bean (C. chinensis only) and (3) larval survival which is strongly overcompensating (particularly in C. maculatus). A discrete generation model is used as a framework to draw these results together and show how the different factors affecting natality and mortality can influence the population dynamics. Finally, the importance of the resource renewal interval in influencing the period of the population cycles is discussed.     

羊草种群种子生产的初步研究

 本文报道了国产优良牧草——羊草,在不同人为干扰的环境条件下,种群种子生产数量性状变化的若干规律。种群密度是成穗率的限制因素之一,在平均为604.7株／m2中等密度的数年割草场上,成穗率随密度增加呈幂函数y=dx-b形式下降,而在平均为1604.9株／m2高密度的长期连续割草场上,成穗率随密度增加呈直线y=a-bx形式下降。种子发芽率与千粒重呈显著正相关(r＝0.9768**)。放牧对成穗有不良影响,但对籽粒的干物质积累过程有一定的促进作用。长期连续割草对种群生殖生长的整个过程均不利,停刈后,自然恢复的速度缓慢。     

Predator-prey populations with parasitic infection

A predator-prey model, where both species are subjected to parasitism, is developed and analyzed. For the case where there is coexistence of the predator with the uninfected prey, an epidemic threshold theorem is proved. It is shown that in the case where the uninfected predator cannot survive only on uninfected prey, the parasitization could lead to persistence of the predator provided a certain threshold of transmission is surpassed.Support by the Central Research Fund of the University of Alberta is gratefully acknowledgedResearch partially supported by the Natural Sciences and Engineering Research Council of Canada, Grant No. NSERC A4823     

Statistical measures of intrasample variability

We have implemented a multivariate statistical methodology to assess the degree and pattern of variability in skeletal samples. Specifically, it is designed to test whether variability in a skeletal sample exceeds that of a local breeding population, defined in the present instance as variability present among crania from an endogamous village. It involves the use of covariance matrices derived from hypothesis and reference samples. The methodology has been applied to subsamples of a Plains Indian craniometric database consisting of 80 variables taken on some 1000 individuals. The subsamples are assumed to reflect varying patterns and degrees of intrasample variability. The assumed group structures are assembled posthoc and subject to various analyses. The excellent results attest to the great potential of the methodology.     

The role of medium conditioning in the population dynamics of the housefly

The role of larval medium conditioning on the behavior of larvae and of ovipositing adults of the housefly, Musca domestica L., was investigated through behavioral preference tests. Larvae were strongly attracted to medium conditioned by themselves or other larvae, while adult females overwhelmingly oviposited in fresh medium. Medium conditioning occurs within a few hours after hatching of an egg cohort and is effective in preventing overcrowding of a single site by shutting off further oviposition within 24 hours after eggs are initially deposited. A model of medium conditioning optimizes density for developing larvae and could also provide for regulation of local larval populations.     

A computer simulation of the epidemiology of the rice dwarf virus

An epidemiological system model was developed to evaluate the role of factors which were responsible for the prevalence of rice dwarf virus (RDV) transmitted by the green rice leafhopper, Nephotettix cincticeps. Simulation tests were conducted by varying values of the following three parameters: the vector density, the coefficient of the efficiency of feeding acquisition of RDV of the vector, and that of efficiency of RDV transmission by the vector. The effect of each parameter was assessed in terms of changes in percentages of infected insects and of infected rice hills. Both the percentages of infected insects and of infected rice hills increased rapidly with increasing vector density within a range of low vector density. The former increased linearly when the acquisitive coefficient was increased. But the percentage of infected rice hills was affected to a lesser extent. The percentage of infected insects and that of infected rice hills increased exponentially with increasing values of the transmission coefficient. The results obtained from the simulation tests were discussed in relation to the ecological factors which caused the recent prevalence of RDV.     

An approach to the edge effect in proof of the validity ofDice's assessment lines in small-mammal censusing

A second fieldwork for the sake of solving the edge-effect subject was carried out in almost the same ways and plans in summer of 1971 in succession to that of 1970. It was found out that the population density was reduced to two-thirds, but the data were sufficient to form the subsequent conclusions:

1. The initial population estimated by the removal census method turned out to be well compatible with the numbers of survivals and emigrants of marked voles calculated byJolly 's method.
2. The natural, entire home ranges of both sexes reached by determining observed range length and width with 24 voles, selected on rigid conditions, agreed with those of the range-conservative type in 1970 in both acreage and elliptic shape.
3. In the majority of the select specimens, considered to reveal the natural ranges, the random distribution in number of captures per station within range was proved by means of I_σ so far as such capture density as treated here is concerned. On the ground of the empirical evidence, the above range size approached by the routine observational method could be made surprisingly accordant with the range size in terms of r-values calculated byWierzbowska 's method.
4. From these proofs, the validity ofDice 's assessment lines makes evident, and besides, it could be further substantiated by use ofMarten 's notion of mouse-equivalents through the mediation ofWierzbowska 's method.
5. Consequently, I have largely come to the conclusion thatDice 's assessment lines stand on justifiable basis from theoretical and empirical angles.

     

Fission-fusion and lineal effect: aspects of the population structure of the Semai Senoi of Malaysia.

Analysis of histories and genealogies from seven relatively unacculturated, swidden-farming Semai settlements shows that the composition of local groups fluctuates through time. This instability is similar to a pattern which Neel and his colleagues have suggested is typical of primitive society, the fission-fusion model. In addition, the individuals comprising Semai fission groups are kinsmen which implies that the number of independent genomes represented is markedly less than the number of individual migrants (the lineal effect). Fission groups may form new villages or fuse with an established settlement. In either case, the genetic effects of such migration are more pronounced than would be expected on the basis of founder effect or random migration. Despite several conspicuous differences in social organization between the Semai and the South American Indians (e.g., bilateral vs. unilineal descent) whose population structure provided the empirical basis for the fission-fusion, lineal effect model, the basic similarities are striking. The Semai case thus lends support to the proposition that this pattern may be of some generality in technologically primitive populations.