Estimation of Catchabilities and Population Sizes of Lobsters

1963 ◽  
Vol 20 (1) ◽  
pp. 59-88 ◽  
Author(s):  
J. E. Paloheimo
Keyword(s):  
Environmental Factors ◽  
Population Size ◽  
Atlantic Coast ◽  
Temperature Data ◽  
New Method ◽  
Bottom Temperature ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Estimate Population Size ◽  
Size Estimates

Techniques of estimating population size, level of fishing, and the degree of dependence of fishing success on environmental factors are examined on the basis of tagging, catch and effort data. A new method is developed to estimate population size from catch, effort, and temperature data when the catchability varies with temperature.The methods of estimation discussed are applied to data collected from a number of lobster fisheries on Canada's Atlantic coast. Analysis confirms a relationship between the catchability of lobsters and bottom temperature. Differences in this relationship are found between areas and between tagged and untagged lobsters within areas. It is suggested that these differences are attributable to the differences in densities as well as to aggregations of lobsters and fishing. The effect of these aggregations on population size estimates is considered.Calculated average catchabilities at comparable temperatures are different for different areas. These differences are correlated with the numbers of trap hauls per day per square miles fished. It is suggested that the differences in the catchabilities might be due to interactions between units of gear not predicted by the customary relationship between catch and effort.

Mark-release-recapture studies on three anthropophilic populations of Aedes (Stegomyia) simpsoni comple(Diptera: Culicidae) in Uganda

1994 ◽  
Vol 84 (4) ◽  
pp. 521-527 ◽  
Author(s):  
J.J. Lutwama ◽  
L.G. Mukwaya
Keyword(s):  
Population Size ◽  
Human Population ◽  
Yellow Fever Virus ◽  
Survival Rates ◽  
Estimated Parameters ◽  
Mark Release Recapture ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Size Estimates ◽  
Aedes Simpsoni

AbstractMultiple mark-release-recapture experiments were carried out on females of three anthropophilic populations of Aedes simpsoni (Theobald) complex at Nkokonjeru and Bwamba in Uganda to determine and compare the population size, survival rates and longevity of the adult stages. There were high recapture rates (26.23%, 2 7.42% and 28.28%) at the different sites. The population sizes, estimated by Jolly's stochastic method for the three sites (465, 561 and 675 female mosquitoes) were not significantly different, neither were the survival rates of the females (0.6026, 0.7145 and 0.8152). Other parameters estimated for the three populations were also similar. Population size estimates by Jolly's stochastic model and the simple Lincoln Index methods were not in agreement. The other method over-estimated population size. Since the estimated parameters for the Nkokonjeru population are similar to those of the Bwamba populations, there is a potential for the transmission of yellow fever virus to the human population at Nkokonjeru, as at Bwamba.

Live-trapping of the northern hairy-nosed wombat (Lasiorhinus krefftii): population-size estimates and effects on individuals

1995 ◽  
Vol 22 (6) ◽  
pp. 741 ◽  
Author(s):  
SD Hoyle ◽  
AB Horsup ◽  
CN Johnson ◽  
DG Crossman ◽  
H McCallum
Keyword(s):  
Population Size ◽  
Confidence Limit ◽  
Mark Recapture ◽  
Population Size Estimate ◽  
Live Trapping ◽  
Population Size Estimates ◽  
Minimum Number ◽  
Estimate Population Size ◽  
Second Period ◽  
Size Estimates

The northern hairy-nosed wombat, one of the most endangered large mammals known, occurs only in Epping Forest National Park, central Queensland. The results of a 3-stage trapping programme, carried out between 1985 and 1993, were used to estimate population size by means of three separate modelling approaches: minimum number alive (MNA), mark-recapture, and trapping effort. Trapping procedure varied among sessions, and each estimator was applied to sessions only where its use was appropriate. The population-size estimate for 1985-86 was 67 (trap effort) with MNA of 58; for 1988-89 it was 62 (Jolly-Seber mark-recapture estimate), with MNA of 48 and upper 95% confidence limit of 77; and for 1993 it was 65 (Chao mark-recapture and trap effort), with MNA of 43 and upper 95% confidence limit of 186 (Chao mark-recapture). No population trends were observed, although variability in estimates and wide confidence intervals meant that power to do so was limited. Trapping affected the health and behaviour of wombats. Animals that were trapped twice within 10 nights lost an average of 0.62 kg (P = 0.006) between captures. Wombats that were trapped twice within the first four nights of traps being set on a burrow showed less weight loss than those trapped for the second time after 5-7 nights (0.23 kg v. 1.54 kg). The effects of trapping appeared to remain with animals for some time, since animals trapped twice more than 30 nights apart and within six months weighed an average of 0.5 kg less (P = 0.013) on second capture. When areas were trapped twice in succession with a 3-week gap, population-size estimates were lower for the second period of trapping. Thus, some wombats may have temporarily left areas disturbed by trapping. The deleterious impact of trapping may be reduced by restricting trapping to periods of four nights. Trapping effectiveness may be increased by minimising disturbance immediately before trapping and by moving traps between periods of trapping.

Population-size estimators and unequal catchability in painted turtles

1998 ◽  
Vol 76 (3) ◽  
pp. 458-465 ◽  
Author(s):  
Nicola Koper ◽  
Ronald J Brooks
Keyword(s):  
Population Size ◽  
Sampling Methods ◽  
Ecological Research ◽  
Closed Population ◽  
Painted Turtles ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Almost All ◽  
Size Estimates ◽  
True Population

Most methods of estimating population size from mark-recapture data assume equal catchability. Failure to meet this assumption may have profound effects on population-size estimates. We used 3 sampling methods to compare population-size estimates derived from Petersen, Schumacher and Eschmeyer, and Jolly-Seber models with the true size of a closed population of painted turtles (Chrysemys picta) in Algonquin Park, Ontario. We found significant variation in capture probabilities, and almost all population-size estimates were far below the true population size. To try to improve the accuracy of the estimates, we applied 4 techniques commonly recommended for reducing bias when catchability is unequal: (i) changing sampling methods, (ii) using several sampling methods simultaneously, (iii) dividing the population by sex, and (iv) calculating population sizes using the computer program CAPTURE. None of the 4 methods reduced the error that resulted from unequal catchability in any of the estimates sufficiently for these methods to be suitable for management of populations or for ecological research.

scholarly journals Conservation of Northwestern and Southwestern Pond Turtles: Threats, Population Size Estimates, and Population Viability Analysis

2021 ◽  
Author(s):  
Stephanie Manzo ◽  
E. Griffin Nicholson ◽  
Zachary Devereux ◽  
Robert N. Fisher ◽  
Chris W. Brown ◽  
...  
Keyword(s):  
Natural Disasters ◽  
Population Size ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Population Declines ◽  
Viability Analysis ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Size Estimates

Accurate status assessments of long-lived, widely distributed taxa depend on the availability of long-term monitoring data from multiple populations. However, monitoring populations across large temporal and spatial scales is often beyond the scope of any one researcher or research group. Consequently, wildlife managers may be tasked with utilizing limited information from different sources to detect range-wide evidence of population declines and their causes. When assessments need to be made under such constraints, the research and management communities must determine how to extrapolate from variable population data to species-level inferences. Here, using three different approaches, we integrate and analyze data from the peer-reviewed literature and government agency reports to inform conservation for northwestern pond turtles (NPT) Actinemys marmorata and southwestern pond turtles (SPT) Actinemys pallida. Both NPT and SPT are long-lived freshwater turtles distributed along the west coast of the United States and Mexico. Conservation concerns exist for both species; however, SPT may face more severe threats and are thought to exist at lower densities throughout their range than NPT. For each species, we ranked the impacts of 13 potential threats, estimated population sizes, and modeled population viability with and without long-term droughts. Our results suggest that predation of hatchlings by invasive predators, such as American bullfrogs Lithobates catesbeianus and Largemouth Bass Micropterus salmoides, is a high-ranking threat for NPT and SPT. Southwestern pond turtles may also face more severe impacts associated with natural disasters (droughts, wildfires, and floods) than NPT. Population size estimates from trapping surveys indicate that SPT have smaller population sizes on average than NPT (p = 0.0003), suggesting they may be at greater risk of local extirpation. Population viability analysis models revealed that long-term droughts are a key environmental parameter; as the frequency of severe droughts increases with climate change, the likelihood of population recovery decreases, especially when census sizes are low. Given current population trends and vulnerability to natural disasters throughout their range, we suggest that conservation and recovery actions first focus on SPT to prevent further population declines.

Fish population size estimates from a small intermittently open estuary in South Africa, based on mark-recapture techniques

2001 ◽  
Vol 52 (3) ◽  
pp. 283 ◽  
Author(s):  
P. D. Cowley ◽  
A. K. Whitfield
Keyword(s):  
Population Size ◽  
Total Population ◽  
Fish Population ◽  
Minimum Size ◽  
Population Estimates ◽  
Likelihood Estimator ◽  
Mark Recapture ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Size Estimates

Population sizes of the migratory marine-spawning fishes in the small intermittently open East Kleinemonde Estuary (33º32′S, 27º03′E) were estimated during two independent mark–recapture studies between 1994 and 1996. Seines were used to sample fishes during the closed-mouth phase of the estuary. All individuals above a stipulated minimum size were marked by fin-clipping. Population estimates were obtained by use of two mark–recapture models (Schnabel and a maximum-likelihood estimator) and a derived method. The total population size was estimated at ~18 000 and ~133 000 individuals during the two study periods respectively. The large temporal (interannual) variability was ascribed to both abiotic (estuary mouth conditions) and biotic-conditions. The dominant species during both periods was Rhabdosargus holubi, which accounted for ~75% and ~80%of the total population of marine fishes in the estuary. The success of this species is attributed to an extended breeding season and the ability to recruit during mouth overwash events.

Estimating the population size of people who inject drugs in Ho Chi Minh City, Vietnam: A two-survey capture-recapture exercise (Preprint)

2019 ◽  
Author(s):  
Abu Abdul-Quader
Keyword(s):  
Population Size ◽  
Illicit Drugs ◽  
People Who Inject Drugs ◽  
Care Service ◽  
Ho Chi Minh City ◽  
Size Estimation ◽  
Population Size Estimates ◽  
Capture Recapture ◽  
The City ◽  
Size Estimates

BACKGROUND Population size estimation of people who inject drugs (PWID) in Ho Chi Minh City (HCMC), Vietnam relied on the UNAIDS Estimation and Projection Package and reports from the city police department. The two estimates vary widely. OBJECTIVE To estimate the population size of people who inject drugs in Ho Chi Minh City, Vietnam METHODS Using Respondent-driven sampling (RDS), we implemented two-source capture-recapture method to estimate the population size of PWID in HCMC in 2017 in 7 out of 24 districts. The study included men or women aged at least 18 years who reported injecting illicit drugs in the last 90 days and who had lived in the city the past six months. We calculated two sets of size estimates, the first assumed that all participants in each survey round resided in the district where the survey was conducted, the second, used the district of residence as reported by the participant. District estimates were summed to obtain an aggregate estimate for the seven districts. To calculate the city total, we weighted the population size estimates for each district by the inverse of the stratum specific sampling probabilities. RESULTS The first estimate resulted in a population size of 19,155 (95% CI: 17,006–25,039). The second one generated a smaller population size estimate of 12,867 (95% CI: 11,312–17,393). CONCLUSIONS The two-survey capture-recapture exercise provided two disparate estimates of PWID in HCMC. For planning HIV prevention and care service needs among PWID in HCMC, both estimates may need to be taken into consideration together with size estimates from other sources.

scholarly journals Microsatellite Development and First Population Size Estimates for the Groundwater Isopod Proasellus walteri

PLoS ONE ◽  
2013 ◽  
Vol 8 (9) ◽  
pp. e76213 ◽  
Author(s):  
Cécile Capderrey ◽  
Bernard Kaufmann ◽  
Pauline Jean ◽  
Florian Malard ◽  
Lara Konecny-Dupré ◽  
...  
Keyword(s):  
Population Size ◽  
Microsatellite Development ◽  
Population Size Estimates ◽  
Size Estimates

scholarly journals Estimating population size of the cave shrimp Troglocaris anophthalmus (Crustacea, Decapoda, Caridea) using mark–release–recapture data

2015 ◽  
Vol 38 (1) ◽  
pp. 77-86
Author(s):  
J. Jugovic ◽  
◽  
E. Praprotnik ◽  
E. V. Buzan ◽  
M. Luznik ◽  
...  
Keyword(s):  
Population Size ◽  
Aquatic Invertebrates ◽  
Anthropogenic Activities ◽  
Age Distribution ◽  
Mark Release Recapture ◽  
Population Size Estimates ◽  
Cave Ecosystems ◽  
Size Estimates ◽  
Abundant Population ◽  
Population Numbers

Population size estimates are lacking for many small cave–dwelling aquatic invertebrates that are vulnerable to groundwater contamination from anthropogenic activities. Here we estimated the population size of freshwater shrimp Troglocaris anophthalmus sontica (Crustacea, Decapoda, Caridea) based on mark–release–recapture techniques. The subspecies was investigated in Vipavska jama (Vipava cave), Slovenia, with estimates of sex ratio and age distribution. A high abundance of shrimps was found even after considering the lower limit of the confidence intervals. However, we found no evidence of differences in shrimp abundances between summer and winter. The population was dominated by females. Ease of capture and abundant population numbers indicate that these cave shrimps may be useful as a bioindicator in cave ecosystems.

scholarly journals Unbiased estimation of linkage disequilibrium from unphased data

2019 ◽  
Author(s):  
Aaron P. Ragsdale ◽  
Simon Gravel
Keyword(s):  
Linkage Disequilibrium ◽  
Population Size ◽  
Evolutionary History ◽  
Unbiased Estimation ◽  
Sequencing Data ◽  
Unbiased Estimators ◽  
Population Size Estimates ◽  
Wide Range ◽  
The Common ◽  
Size Estimates

AbstractLinkage disequilibrium is used to infer evolutionary history and to identify regions under selection or associated with a given trait. In each case, we require accurate estimates of linkage disequilibrium from sequencing data. Unphased data presents a challenge because the co-occurrence of alleles at different loci is ambiguous. Commonly used estimators for the common statistics r2 and D2 exhibit large and variable upward biases that complicate interpretation and comparison across cohorts. Here, we show how to find unbiased estimators for a wide range of two-locus statistics, including D2, for both single and multiple randomly mating populations. These provide accurate estimates over three orders of magnitude in LD. We also use these estimators to construct an estimator for r2 that is less biased than commonly used estimators, but nevertheless argue for using rather than r2 for population size estimates.

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