scholarly journals Population size estimates of pink river dolphins (Inia geoffrensis) using mark-recapture methods on photo-identification

2014 ◽  
Vol 9 (2) ◽  
pp. 132-139 ◽  
Author(s):  
Catalina Gómez-Salazar ◽  
Hal Whitehead ◽  
Fernando Trujillo
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Freshwater Ecosystems ◽  
Mark Recapture ◽  
Photo Identification ◽  
Population Size Estimate ◽  
Population Size Estimates ◽  
Inia Geoffrensis ◽  
Colombian Amazon ◽  
Size Estimates

Population size estimates of pink river dolphins (Inia geoffrensis) are critical to assess the conservation status of this species and the impacts of increasing human stressors in freshwater ecosystems. Photo-identifications of Inia dolphins were collected between February 2007 and August 2009 in two locations of the Colombian Amazon and Orinoco river basins. Population sizes of Inia were obtained by using the closed (Petersen) mark-recapture model on photo-identifications. The total population size estimate for right/left side individuals was 129/71 Inia dolphins (CV=0.36/0.35) in the Amazon location and 125/58 Inia dolphins (CV=0.77/0.69) in the Orinoco location. The survey and analysis protocols were designed to try to meet mark-recapture assumptions. However, photo-identification was incomplete in both study areas, and there could be recruitment and unequal probabilities of capture due to preferences of individuals for certain areas. Further effort should be focused towards expanding the photo-identification catalogues and creating long-term monitoring programs.

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.

scholarly journals Estimates of abundance and apparent survival of coastal dolphins in Port Essington harbour, Northern Territory, Australia

2014 ◽  
Vol 41 (1) ◽  
pp. 35 ◽  
Author(s):  
Carol Palmer ◽  
Lyndon Brooks ◽  
Guido J. Parra ◽  
Tracey Rogers ◽  
Debra Glasgow ◽  
...  
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Local Population ◽  
Northern Territory ◽  
Systematic Sampling ◽  
Northern Australia ◽  
Apparent Survival ◽  
Photo Identification ◽  
Population Size Estimates ◽  
Sampling Protocols

Context Three dolphin species occur in coastal waters of monsoonal northern Australia: the Australian snubfin (Orcaella heinsohni), humpback (Sousa sp.) and the bottlenose (Tursiops sp.). Their overall population size and trends are poorly known, and their conservation status has been difficult to resolve, but can be expected to deteriorate with likely increased development pressures. Aims We sought to provide an estimate of abundance, and apparent survival, of the three dolphin species at the largely undeveloped harbour of Port Essington (325 km2), Northern Territory, with repeated sampling over a 2.9-year period. Given increasing obligations to undertake population assessments for impact studies at proposed development sites, we assess the strengths and limitations of a systematic sampling program. Methods We used photo-identification data collected during systematic boat-based transect surveys undertaken from 2008 to 2010 and Pollock’s robust capture–recapture design model. Key results Total abundance estimates for the three species were variable across different sampling periods. The estimated number of individuals in the sampled area varied per sampling episode from 136 (s.e. 62) to 222 (s.e. 48) for snubfin, from 48 (s.e. 7) to 207 (s.e. 14) for humpbacks and from 34 (s.e. 6) to 75 (s.e. 9) for bottlenose dolphins. Apparent survival was estimated for snubfin at 0.81 (s.e. 0.11), humpbacks at 0.59 (s.e. 0.12) and bottlenose at 0.51 (s.e. 0.17) per annum. Key conclusions (1) The values derived here provide some of the only estimates of local population size for these species across monsoonal northern Australia; (2) population-size estimates varied considerably among seasons or sampling episodes; (3) the low apparent survival probabilities indicated that many individuals may move at scales larger than the study area; (4) density of snubfin and humpback dolphins in the present study area exceeded the few other estimates available for these species elsewhere in Australia. Implications The present study provided the first baseline estimates of abundance and apparent survival for three coastal dolphin species in monsoonal northern Australia. Such information is becoming increasingly important as development pressures intensify in coastal areas. Sampling protocols for future monitoring and impact assessment need an enhanced consideration of seasonality and scale issues.

scholarly journals Effects of Social Organization, Trap Arrangement and Density, Sampling Scale, and Population Density on Bias in Population Size Estimation Using Some Common Mark-Recapture Estimators

2017 ◽  
Author(s):  
Manan Gupta ◽  
Amitabh Joshi ◽  
T. N. C. Vidya
Keyword(s):  
Population Density ◽  
Social Organization ◽  
Population Size ◽  
Robust Design ◽  
Population Size Estimation ◽  
Size Estimation ◽  
Mark Recapture ◽  
Social Species ◽  
Population Size Estimates ◽  
Size Estimates

AbstractMark-recapture estimators are commonly used for population size estimation, and typically yield unbiased estimates for most solitary species with low to moderate home range sizes. However, these methods assume independence of captures among individuals, an assumption that is clearly violated in social species that show fission-fusion dynamics, such as the Asian elephant. In the specific case of Asian elephants, doubts have been raised about the accuracy of population size estimates. More importantly, the potential problem for the use of mark-recapture methods posed by social organization in general has not been systematically addressed. We developed an individual-based simulation framework to systematically examine the potential effects of type of social organization, as well as other factors such as trap density and arrangement, spatial scale of sampling, and population density, on bias in population sizes estimated by POPAN, Robust Design, and Robust Design with detection heterogeneity. In the present study, we ran simulations with biological, demographic and ecological parameters relevant to Asian elephant populations, but the simulation framework is easily extended to address questions relevant to other social species. We collected capture history data from the simulations, and used those data to test for bias in population size estimation. Social organization significantly affected bias in most analyses, but the effect sizes were variable, depending on other factors. Social organization tended to introduce large bias when trap arrangement was uniform and sampling effort was low. POPAN clearly outperformed the two Robust Design models we tested, yielding close to zero bias if traps were arranged at random in the study area, and when population density and trap density were not too low. Social organization did not have a major effect on bias for these parameter combinations at which POPAN gave more or less unbiased population size estimates. Therefore, the effect of social organization on bias in population estimation could be removed by using POPAN with specific parameter combinations, to obtain population size estimates in a social species.

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.

scholarly journals Conservation status of threatened and endemic birds of New Britain, Papua New Guinea

2017 ◽  
Vol 28 (3) ◽  
pp. 439-450
Author(s):  
ROBERT A. DAVIS ◽  
GUY DUTSON ◽  
JUDIT K. SZABO
Keyword(s):  
Population Size ◽  
Papua New Guinea ◽  
Oil Palm ◽  
Conservation Status ◽  
Bird Species ◽  
New Guinea ◽  
Old Growth Forest ◽  
Population Size Estimates ◽  
New Britain ◽  
Size Estimates

SummaryNew Britain in the Bismarck Archipelago of Papua New Guinea supports 14 endemic bird species and together with New Ireland, forms an Endemic Bird Area that supports 38 restricted range species. Extensive conversion of lowland forest to oil palm plantations resulted in the loss of over 20% of forest under 100 m altitude between 1989 and 2000. However the rate of loss has subsequently slowed (2.2% loss across all altitudes between 2002 and 2014), and much forest remains at higher altitudes: 72% of New Britain remained forested (including secondary forest) in 2014. Despite the ongoing high threat and rich endemic bird fauna, the state of knowledge of the conservation status of birds in New Britain is very poor. We use an unprecedented dataset based on 415 hours of bird surveys conducted in oil palm plantations, as well as primary and secondary forests at all altitudes, to revise the IUCN status of New Britain’s birds. These data indicate that six species of elevated conservation concern are less dependent on old-growth forest than previously assessed. We recommend reduced population size estimates for one species, New Britain Kingfisher Todiramphus albonotatus. We recommend increased population size estimates for seven species: Pied Cuckoo-dove Reinwardtoena browni, Yellowish Imperial Pigeon Ducula subflavescens, Green-fronted Hanging Parrot Loriculus tener, Blue-eyed Cockatoo Cacatua opthalmica, Violaceous Coucal Centropus violaceous, New Britain Boobook Ninox odiosa and New Britain Thrush Zoothera talaseae. Despite our comprehensive surveys, Slaty-backed Goshawk Accipiter luteoschistaceus, New Britain Sparrowhawk Accipiter brachyurus, New Britain Bronzewing Henicophaps foersteri and Golden Masked-owl Tyto aurantia remain very rarely recorded and require further assessment. With ongoing habitat loss, particularly in lowland areas, New Britain’s birds urgently require more attention.

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.

The closed-subpopulation method and estimation of population size from mark-recapture and ancillary data

2000 ◽  
Vol 78 (2) ◽  
pp. 320-326 ◽  
Author(s):  
Frank AM Tuyttens
Keyword(s):  
Population Size ◽  
Ancillary Data ◽  
Mark Recapture ◽  
Animal Populations ◽  
Accuracy And Precision ◽  
Population Size Estimates ◽  
Minimum Number ◽  
Flexible Framework ◽  
And Performance ◽  
Better Than

The algebraic relationships, underlying assumptions, and performance of the recently proposed closed-subpopulation method are compared with those of other commonly used methods for estimating the size of animal populations from mark-recapture records. In its basic format the closed-subpopulation method is similar to the Manly-Parr method and less restrictive than the Jolly-Seber method. Computer simulations indicate that the accuracy and precision of the population estimators generated by the basic closed-subpopulation method are almost comparable to those generated by the Jolly-Seber method, and generally better than those of the minimum-number-alive method. The performance of all these methods depends on the capture probability, the number of previous and subsequent trapping occasions, and whether the population is demographically closed or open. Violation of the assumption of equal catchability causes a negative bias that is more pronounced for the closed-subpopulation and Jolly-Seber estimators than for the minimum-number-alive. The closed-subpopulation method provides a simple and flexible framework for illustrating that the precision and accuracy of population-size estimates can be improved by incorporating evidence, other than mark-recapture data, of the presence of recognisable individuals in the population (from radiotelemetry, mortality records, or sightings, for example) and by exploiting specific characteristics of the population concerned.

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

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.

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