Recapture Techniques Research Articles

Enumeration of non-communicable disease in rural South Africa by electronic data linkage and capture-recapture techniques.

Non-communicable diseases (NCDs) are becoming increasingly common and important in developing countries, yet their enumeration is problematic. We have attempted to enumerate NCD patients in a rural district of KwazuluNatal, South Africa, using the techniques of electronic data linkage and capture-recapture (CR). We examined four major NCDs (hypertension, diabetes, asthma and epilepsy). Basic patient details were recorded onto EpiInfo software over a 6-week period, from the main hospital clinic at Hlabisa, as well as the 10 outlying peripheral health clinics. Using electronic data linkage of lists from the main hospital, the peripheral clinics, and repeat prescription cards, a district NCD register was produced of 2455 patients. The mean age was 51 +/- 16 years (1 SD) and 76% were female. Of the total NCD patients, 62% had hypertension (age 57 +/- 12 years, 82% female), 16% epilepsy (age 35 +/- 17 years, 49% female), 13% asthma (age 45 +/- 19 years, 60% female) and 12% diabetes (age 54 +/- 13 years, 61% female). Estimated population crude prevalence rates for known NCD cases on the register were 7.4% for hypertension, epilepsy 0.2%, asthma 0.2% and diabetes 0.2%. We also attempted a CR analysis to assess completeness of data, by comparing overlap between patients attending peripheral clinics, and the central Hlabisa Hospital clinic. Matching by name, age, and diagnosis proved feasible, but there was little overlap, and CR calculations were invalid because of the relative independence of sources. We conclude that NCDs are common in rural Africa, and that a simple NCD district register is a potentially feasible and inexpensive option. Capture-recapture analysis is feasible, but requires suitable lists with acceptable overlap of patients.

Methods for studying spatial behaviour of freshwater fishes in the natural environment

Spatial behaviour of fishes in fresh and brackish water ranges in temporal scales between localized diel movements, often associated with foraging and predator evasion, to seasonal or life‐cycle related events involving movements between freshwater habitats or freshwater and marine biotopes. Recent technological advances have resulted in dramatic improvements in the range of techniques available for the study of spatial behaviour of freshwater fishes in the natural environment, and broadly may be divided into two categories: capture dependent and capture independent. The former incorporates those methods that rely on sampling marked fish (mark–recapture) or unmarked fish (density estimates, catch per unit effort) over defined scales of time and space in order to derive information on distribution and movement. Captured fish may also be tagged with transmitters that radiate energy, enabling the fish to be tracked and/or environmental data to be gathered. Biochemical analysis of samples from fish, requiring non‐destructive sampling (genetic analysis and scale microchemistry) or destructive sampling (otolith microchemistry) may also provide information on migration and ontogenetic processes. Capture independent techniques include visual observation and video techniques, hydroacoustics and automated fish counting. Catch per unit effort and mark–recapture techniques are most efficient where long‐term fishery or monitoring studies are in place and data on crude spatial and temporal scales are acceptable. They also have the advantages of low technical requirements and low equipment costs. Where specific management or ecological questions are pertinent, recapture independent techniques may be more appropriate. Telemetric methods can provide high resolution information at the individual level, while hydroacoustics is increasingly providing information at the population level in large lake and river environments. Biochemical methods are becoming increasingly useful in determining the extent of population segregation, where DNA analysis is used, and in the study of migration and ontogenetic changes in behaviour, where otolith microchemistry and stable isotope analysis is used.

Biases associated with population estimation using molecular tagging

Although capture–recapture techniques are often used to estimate population size, these approaches are difficult to implement for a wide variety of species. Highly polymorphic microsatellite markers are useful in individual identification, and these ‘molecular tags’ can be collected without having to capture or trap the individual. However, several sources of error associated with molecular identification techniques, including failure to identify individuals with the same genotype for these markers as being different, and incorrect assignment of individual genotypes, could bias population estimates. Simulations of populations sampled for the purpose of estimating population size were used to assess the extent of these potential biases. Population estimates tended to be biased downward as the likelihood of individuals sharing the same genotype increased (as measured by the probability of identity (PI) of the multi-locus genotype); this bias increased with population size. Populations of 1000 individuals were underestimated by ≥5% when the PI was as small as 1.4 × 10−7. A similar-sized bias did not occur for populations of 50 individuals until the PI had increased to approximately 2.5 × 10−5. Errors in genotype assignment resulted in overestimates of population size; this problem increased with the number of samples and loci that were genotyped. Population estimates were often >200% the size of the simulated populations when the probability of making a genotyping error was 0.05/locus and 7–10 loci were used to identify individuals. This bias was substantially reduced by decreasing genotyping error rate to 0.005. If possible, only highly polymorphic loci that are critical for the identification of the individual should be used in molecular tagging, and considerable efforts should be made to minimize errors in genotype determination.

Biases associated with population estimation using molecular tagging

AbstractAlthough capture–recapture techniques are often used to estimate population size, these approaches are difficult to implement for a wide variety of species. Highly polymorphic microsatellite markers are useful in individual identification, and these ‘molecular tags’ can be collected without having to capture or trap the individual. However, several sources of error associated with molecular identification techniques, including failure to identify individuals with the same genotype for these markers as being different, and incorrect assignment of individual genotypes, could bias population estimates. Simulations of populations sampled for the purpose of estimating population size were used to assess the extent of these potential biases. Population estimates tended to be biased downward as the likelihood of individuals sharing the same genotype increased (as measured by the probability of identity (PI) of the multi‐locus genotype); this bias increased with population size. Populations of 1000 individuals were underestimated by ≥5% when the PI was as small as 1.4 × 10−7. A similar‐sized bias did not occur for populations of 50 individuals until the PI had increased to approximately 2.5 × 10−5. Errors in genotype assignment resulted in overestimates of population size; this problem increased with the number of samples and loci that were genotyped. Population estimates were often >200% the size of the simulated populations when the probability of making a genotyping error was 0.05/locus and 7–10 loci were used to identify individuals. This bias was substantially reduced by decreasing genotyping error rate to 0.005. If possible, only highly polymorphic loci that are critical for the identification of the individual should be used in molecular tagging, and considerable efforts should be made to minimize errors in genotype determination.

MODELING DIFFUSIVE SPREAD IN A HETEROGENEOUS POPULATION: A MOVEMENT STUDY WITH STREAM FISH

Using a mark–recapture technique in a small temperate stream, we described the movement of four fish species over a five-month period and developed a mathematical model that described the observed movement patterns. The movement distributions were generally leptokurtic, and two of the four species demonstrated some degree of upstream bias. There was little difference in movement among species or through time. There were no temporal correlations in probability of movement, movement direction, or distance moved. The spatial spread of the most abundant species, bluehead chubs, over a four-month period was characterized by upstream bias, diffusion-like spread, and persistent leptokurtosis. Bluehead chubs demonstrated complex relationships between probability of movement and size and growth, while creek chubs showed only an effect of size on probability of movement. Further, growth of individual bluehead chubs was correlated through time. These empirical results suggest the hypothesis that heterogeneity in phenotypic attributes, such as size and growth, is related to heterogeneity in movement behavior. A diffusion–advection model of bluehead chub movement, structured with two subgroups that dispersed at different rates (“fast fish” and “slow fish”), was parameterized and validated with the field data. This model with heterogeneity in movement rates generated the leptokurtic pattern observed in the field data, in contrast to the classic diffusion model without population heterogeneity, which produces a normal distribution. The results from this work suggest that heterogeneity in fitness-influencing attributes such as size and growth could explain heterogeneity in individual-level movement behavior and might underlie the leptokurtic patterns that have been observed at the population level in numerous field studies.

Modeling Diffusive Spread in a Heterogeneous Population: A Movement Study with Stream Fish

Using a mark–recapture technique in a small temperate stream, we described the movement of four fish species over a five-month period and developed a mathematical model that described the observed movement patterns. The movement distributions were generally leptokurtic, and two of the four species demonstrated some degree of upstream bias. There was little difference in movement among species or through time. There were no temporal correlations in probability of movement, movement direction, or distance moved. The spatial spread of the most abundant species, bluehead chubs, over a four-month period was characterized by upstream bias, diffusion-like spread, and persistent leptokurtosis. Bluehead chubs demonstrated complex relationships between probability of movement and size and growth, while creek chubs showed only an effect of size on probability of movement. Further, growth of individual bluehead chubs was correlated through time. These empirical results suggest the hypothesis that heterogeneity in phenotypic attributes, such as size and growth, is related to heterogeneity in movement behavior. A diffusion–advection model of bluehead chub movement, structured with two subgroups that dispersed at different rates (“fast fish” and “slow fish”), was parameterized and validated with the field data. This model with heterogeneity in movement rates generated the leptokurtic pattern observed in the field data, in contrast to the classic diffusion model without population heterogeneity, which produces a normal distribution. The results from this work suggest that heterogeneity in fitness-influencing attributes such as size and growth could explain heterogeneity in individual-level movement behavior and might underlie the leptokurtic patterns that have been observed at the population level in numerous field studies.

Complex life histories of fishes revealed through natural information storage devices: case studies of diadromous events as recorded by otoliths

Diadromous fishes – species that move across salinity gradients as part of their life repertoire – form a major part of coastal and inland fisheries. Conventional mark–recapture techniques have long been used to track their movements, but give incomplete information at best. On the other hand, otoliths (ear-stones) of fishes can provide a complete record of major life history events, as reflected both in their microstructure and elemental composition. Strontium, which substitutes for calcium in the aragonite matrix of otoliths, is a powerful tracer of salinity histories in many migratory fishes. We measured Sr and Ca with a nuclear microprobe (PIXE) and show examples (eel, Anguilla anguilla; brown trout, Salmo trutta; American shad, Alosa sapidissima) of how the technique has solved several mysteries within fisheries biology.

POPULATION AND COMMUNITY ECOLOGY OF SMALL RODENTS IN MONTANE FOREST OF WESTERN MEXICO

Abstract This study reports results of a 14-month live-trap study of small-rodent communities in 2 habitats, cloud forest and disturbed areas, at Las Joyas Scientific Station of the Sierra de Manantlan Biosphere Reserve, western Mexico. Seven taxa of 2 families (Muridae, Heteromyidae) of small rodents were captured (Hodomys alleni, Liomys pictus, Oryzomys couesi, Peromyscus aztecus, Reithrodontomys fulvescens, R. sumichrasti, and Sigmodon alleni). Information about age structure, population dynamics, biomass, and reproduction were obtained with mark–recapture techniques for the most abundant species (P. aztecus and R. fulvescens) in both habitats. These species comprised 80.3% of the 707 captures in the cloud forest (P. aztecus, 51.2%; R. fulvescens, 29.1%), whereas, in the disturbed areas, R. fulvescens represented 81.7% of the 916 captures. Species varied in population density, relative abundance, and timing of reproduction, which was seasonal. Reproductive activity for P. aztecus peaked in the middle o...

Australian fur seals at Seal Rocks, Victoria: pup abundance by mark - recapture estimation shows continued increase

The abundance of Australian fur seal pups was determined at Seal Rocks, Westernport, Victoria in late December 1997 using a mark–recapture procedure with repeated recapture sessions. Pups (n = 1291) were marked by clipping the black guard hair on the head to reveal lighter underfur. Recaptures from the whole colony were made on eight occasions 1–3 days later. In the recapture sessions, a mean of 32% of sighted pups had been marked. Estimates of pup numbers over the eight recapture sessions were calculated using the Petersen estimate and then combined by taking their arithmetic mean. The combined estimate was 4024 (95% confidence range 3908–4141). In 1991–92, a similar procedure led to an estimate of pup numbers of 2817 (95% confidence range 2703–2930). For both breeding seasons, estimates of pup numbers from each recapture session were also combined assuming a joint hypergeometric distribution; there was little difference in the results from the two procedures, although the confidence intervals for the hypergeometric mean were smaller than those for the arithmetic mean. From 1991–92 to 1997–98, pup numbers increased by 43%, at an exponential rate of 0.059 (95% confidence range 0.0526–0.0664), equivalent to 6.1% per annum (5.4–6.9%). This is greater than the rate of increase of pups at the colony between 1968–69 and 1991–92, which was 0.023 (95% confidence range 0.0198–0.0268), equivalent to 2.4% per annum (2.0–2.7%). Because of the rapid rate of increase of the Australian fur seal colony at Seal Rocks and the importance of the locality for tourism, we recommend that the abundance of pups there be determined every 3–5 years using a mark–recapture technique.

Estimating the number of remaining defects after inspection

An essential component of all software inspection processes is a well-founded decision about continuing or stopping the current process. This decision should be based upon directly relevant quantitative information — the number of defects remaining in the artefact. This quantity can be estimated by the use of capture–recapture methods. Several software engineering papers have explored this topic, but the question of which capture–recapture technique is best still remains unresolved. This paper attempts to shed further light upon this question. After reviewing the relevant capture–recapture models and previous evaluations within a software engineering context, the paper proceeds to evaluate the models by using data collected from subject-based experiments on software inspection. The experiments used artefacts where the number of defects was known and hence a direct measure of the accuracy of the various capture–recapture techniques was available. The paper reports that most heterogeneity models show, in general, superior performance — especially the Jackknife estimator. However, the paper concludes that further work is required to correct the limitations of the current models if reliable estimates are to be achieved. Copyright © 1999 John Wiley & Sons, Ltd.

ADVANCES IN APPLIED ECOLOGICAL TECHNIQUES A novel mark–recapture technique and its application to monitoring the direction and distance of local movements of rangeland grasshoppers (Orthoptera: Acrididae) in the context of pest management

Summary 1. Rangeland grasshopper movement was studied in Wyoming, USA, with respect to the biological and ecological factors (population density, developmental stage and weather) influencing net displacement and directionality. 2. A novel adaptation of the mark–recapture method was developed to monitor grasshopper dispersal. The method used fluorescent powder and resighting marked grasshoppers in the field with ultraviolet light, rather than physical recapturing of individuals. 3. Rangeland grasshoppers exhibited a strong tendency for directional movement. Adult grasshoppers demonstrated a significant tendency for dispersal in a north‐westerly direction across a range of population densities (5–8, 10–15 and ≥ 18 grasshoppers m–2). Although not a definitive explanation, weather might have influenced this behaviour, as the grasshoppers consistently moved upwind. 4. The mean displacement of grasshoppers in a 36‐h period ranged from 2·3 m in nymphs to 3·7 m in adults, with the distance of displacement being positively correlated with population density. 5. An understanding of grasshopper movement in terms of directionality and displacement has immediate applicability to reduced agent–area treatments for rangeland grasshopper management.

Population Structure, Behaviour and Selection of Oviposition Sites of an Endangered Butterfly, Parnassius Mnemosyne, in Litovelské Pomoravíl. Czech Republic

A population of Parnassius mnemosyne L., an endangered butterfly species, was studied for two seasons by mark–release–recapture (MRR) techniques in the Litovelske Pomoravi Protected Landscape Area, Czech Republic. There were four distinct colonies in the area; the MRR data indicate that the largest colony contained over 1000 adult males during peak flight in 1996 suggesting that the area harbours one of the largest populations of the species in the Czech Republic. The detected rate of intercolony movements showed that the individual colonies were not genetically isolated, but the interchange of individuals was limited. Capture sex ratio and estimated sex ratios were both consistently male-biased. We suggest that this might be caused by different behaviour of the sexes which renders the males more catchable: the females spent most of their time either egg laying or resting, which makes them inconspicuous compared to the patrolling males. Preferred oviposition sites were open, sunny patches such as forest clearings which may be due to different hostplant quality compared to hostplants under closed canopy. The heliophily of the species and the dependency of females on open oviposition sites render the butterfly vulnerable due to a decline in coppice management and replacement of fine mosaic of sunny and shady patches by even-aged forest stands.

A Population Survey of the Italian Subterranean Termite Reticulitermes lucifugus lucifugus Rossi in Bagnacavallo (Ravenna, Italy), Using the Triple Mark Recapture Technique (TMR)

Abstract The present paper presents an application of the Triple Mark Recapture technique on two Italian populations of the subterranean termite (Reticulitermes lucifugus). Two large infested areas in the historical center of the town Bagnacavallo (Ravenna) were chosen. Two dye markers were utilized, Nile Blue A or Neutral Red respectively for the two sites. The first population was estimated at 1,085,000 ± 92,000 insects, foraging on a surface of 1500 m2; the second, smaller, population has been estimated to be 640,000 ± 33,000 insects, foraging on an area of 675 m2. Maximum linear distance observed in both sites was 45-50 m. Population dynamics look different in the two sites: in the first site the spread distribution with a few insects at each feeding point probably indicates an old, well established, population which grows slowly in all directions during the hot season. In the second site the expansion was much more rapid and it is possible to hypothesise that the termite colony settled in this area m...

Road Crossings as Barriers to Small-Stream Fish Movement

We used mark–recapture techniques to examine the effects of four types of road crossings on fish movement during spring base flows and summer low flows in small streams of the Ouachita Mountains, west-central Arkansas. We assessed movement for 21 fish species in seven families through culvert, slab, open-box, and ford crossings and through natural reaches. We detected no seasonal or directional bias in fish movement through any crossing type or the natural reaches. Overall fish movement was an order of magnitude lower through culverts than through other crossings or natural reaches, except no movement was detected through the slab crossing. In contrast, open-box and ford crossings showed little difference from natural reaches in overall movement of fishes. Numbers of species that traversed crossings and movement within three of four dominant fish families (Centrarchidae, Cyprinidae, and Fundulidae) also were reduced at culverts relative to ford and open-box crossings and natural reaches. In spring, retention of fishes was consistently highest in stream segments upstream of crossings and lowest in downstream segments for all crossing types, a response attributed to scouring associated with spring spates. Water velocity at crossings was inversely related to fish movement; culvert crossings consistently had the highest velocities and open-box crossings had the lowest. A key requirement for improving road crossing designs for small-stream fish passage will be determination of critical levels of water velocity through crossings.

Seasonal and annual growth rates in the Antarctic fish Notothenia coriiceps Richardson

Growth in Antarctic fishes is assumed to be seasonal but quantitative data are scarce. Growth rates in juvenile Notothenia coriiceps, a typical Antarctic fish, were measured using mark–recapture techniques and found to be greater when periods of liberty included summer and early autumn months and least when liberty was restricted to winter months. Weight specific growth rates ranged from −0.08–0.26% body weight day −1. Year class analysis and cohort analysis were attempted on serial samples of the population but proved ineffective methods for detecting seasonal growth in these slow growing fishes. A tentative description of the seasonal growth profile is proposed. Seasonality in growth indicates that some form of growth limitation is active; competing hypotheses of temperature and resource limitation are discussed. Annual growth rates in three year classes showed an inverse relationship with age. Parameters of the Pütter-von Bertalanffy growth equation were estimated. Comparison with other studies show the growth characteristics of N. coriiceps differ with geographical location but have not changed substantially at Signy Island over the past 25 years.

The ecology of brown trout and Arctic charr in two lakes in Høylandet

Food consumption, growth, fish length distributions,population sizes and habitat use of the salmonids intwo lakes in the Hoylandet area were studied in1986–89. The allopatric brown trout (Salmotrutta L.) in the tarn Royrtjonna (27 ha) fed mainlyon organisms at the lake surface , crustaceanplankton, Trichoptera and Chironomidae. Only 5% ofthe trout reached an age of 6 years and a length of25 cm. Sexual maturation started at age 3 and a lengthof 14 cm. Through mark – recapture technique thenumber of trout >10 cm was estimated to 115 ha-1.Growth, fish length frequencies and sexualmaturation of the sympatric brown trout and Arcticcharr (Salvelinus alpinus (L.)) in LakeStorgronningen (530 ha) were not much different. TheStorgronningen charr fed chiefly on zooplankton whichby volume represented 33% for the trout. The foodconsumption of Storgronningen trout was at maximum inJuly with 2.06 mg food (d.w.) per g live fish and forcharr in September with 1.26 mg food. The maximumsize-independent growth rate of trout was 5.2%day-1 in late June, and for charr 4.1%day-1 in late July. Seventy percent of theirseasonal growth took place before 15 August. The charrstayed mainly deeper than 3-4 m, at water temperatures<15 °C. Brown trout stayed mainly the littoralzone and in near surface water of the pelagic. Thenumber of pelagic charr was estimated hydroacusticallyto 50 ind. ha-1. The charr spawn in thelake. Mean numbers of juvenile trout in the twolargest tributaries were 26 and 48 per 100 m2.Their annual length increment was 2.8–3.4 cm. Noindication of acidification or other human inducedimpacts were found. The lakes and their tributariesrepresent complex aquatic systems, representative forpristine oligotrophic Norwegian lowland lakes.

Preweaning mortality of Weddell seal pups

We examined mortality prior to weaning of Weddell seal pups (Leptonychotes weddellii), using resighting data collected from 1984 to 1993 on the annual ice of McMurdo Sound, Antarctica. Mortality rates were estimated using counts of dead pups found on the surface and mark–recapture techniques. The standard Jolly–Seber model for open populations fit the recapture data best and corresponded well to the known biology of these animals. Yearly mortality rates estimated by mark–recapture techniques ranged from 6 to 22%, with a mean across years of 13%. These values are twice as high as those previously reported for Weddell seals and those calculated from counts of dead pups in this study. This suggests that there is significant unseen mortality due either to undiscovered fatalities on the ice surface or to significant mortality occurring in the water.

Prevalance of diabetes in elderly patients requiring permanent cardiac pacemaker insertion

Diabetes mellitus increases the rate of atrioventricular block after a myocardial infarction; right bundle branch block is more common than expected in the diabetic outpatient population. We decided to assess whether diabetic subjects were more likely to need permanent cardiac pacemaker insertion. Data from patients in Leicestershire who had undergone permanent cardiac pacemaker insertion during a 4-year period were analysed. The capture recapture technique was used: Hospital Activity Analysis data as capture, ward admission book and case note confirmation as recapture. Diabetes coding accuracy was confirmed from the central register and from an analysis of 100 sets of case notes. The number of these patients with diabetes was then recorded. Data for the reference population was obtained using a survey of a market town in Leicestershire. There were 688 patients, most (79%) aged over 65 years. Our analysis was performed on this group. Of this age group undergoing pacemaker insertion. 11.1% was diabetic. In the same age group, 8.3% of the controls were diabetic: a relative risk of 1.34 (P < 0.01, 95% confidence interval 1.25-1.44). This relative risk is likely to be an underestimate. The aetiology of this excess risk is uncertain: it is most likely due to ischaemic heart disease, but microangiopathy or increased cholinergic sensitivity may play a role.

Capture-Recapture Methods in Epidemiological Studies

Medical researchers often are faced with the challenge of estimating the total number of cases in a population based on incomplete samples. Because of a lack of explicit methods for determining if all cases have been counted, indirect methods for estimating the abundance of disease have been developed. Capture-recapture models are an indirect method of estimating population sizes that have been employed in recent epidemiological studies. These methods, derived from techniques developed for studies of animal abundance, estimate the true population size by evaluating the degree of overlap among incomplete lists of cases from existing data sources. Although intuitively appealing, the successful application of these methods is dependent upon a clear understanding of the biology of the disorder involved, the dynamics of the reference population, and the assumptions and robustness of the specific models used. Failure to address these issues can lead to inaccurate and sometimes misleading results. This article describes some of the strengths and limitations of recapture techniques and provides the reader with a foundation from which to explore the methods in further detail.

Capture-Recapture Methods in Epidemiological Studies

AbstractMedical researchers often are faced with the challenge of estimating the total number of cases in a population based on incomplete samples. Because of a lack of explicit methods for determining if all cases have been counted, indirect methods for estimating the abundance of disease have been developed. Capture-recapture models are an indirect method of estimating population sizes that have been employed in recent epidemiological studies. These methods, derived from techniques developed for studies of animal abundance, estimate the true population size by evaluating the degree of overlap among incomplete lists of cases from existing data sources. Although intuitively appealing, the successful application of these methods is dependent upon a clear understanding of the biology of the disorder involved, the dynamics of the reference population, and the assumptions and robustness of the specific models used. Failure to address these issues can lead to inaccurate and sometimes misleading results. This article describes some of the strengths and limitations of recapture techniques and provides the reader with a foundation from which to explore the methods in further detail.