Relative Abundance Index Research Articles

Spatial and Temporal Habitat Use by the Main Prey Species of Tigers in Two Protected Areas of Thailand’s Southern Western Forest Complex

Tigers (Panthera tigris) have disappeared from over 90% of their historical range, and extant populations face habitat loss, direct poaching, and prey depletion in otherwise suitable habitats. In Thailand, tiger numbers continue to decline due to prey depletion, yet a few strongholds remain. Recently, tigers have been detected in the Southern Western Forest Complex (sWEFCOM), following intensification of conservation efforts. However, there is still a lack of primary data on the status of tigers and their prey in the sWEFCOM. To fill this knowledge gap, we conducted camera trapping surveys between 2019 and 2020 in Khuean Srinagarindra National Park (KSR) and Salakphra Wildlife Sanctuary (SLP). Located near a tiger source population in Thungyai Naresuan and Huai Kha Khaeng, these areas are potential areas for tiger recovery. In particular, our study assessed the status of prey, a prerequisite to the persistence and recovery of tigers. Based on relative abundance indices, time overlap and occupancy models, we analysed the effect of anthropogenic and ecological factors on the spatial and temporal habitat use of the main prey species. We highlight that anthropogenic factor impacted species-specific habitat relationships. Mainly, shifts in ungulate temporal and spatial habitat use was linked to human activities. These relationships, however, differed between the two protected areas. As tiger recovery depends on prey recovery, we suggest that increased conservation law enforcement and greater engagement with villages within and adjacent to protected areas are essential to minimising unsustainable resource use practices that currently affect prey.

A spatial analysis of longline survey data for improved indices of Atlantic halibut abundance

Abstract Atlantic halibut (Hippoglossus hippoglossus) support an economically important fishery on the eastern coast of Canada. Like other species that are not well sampled by trawl surveys, halibut in this area are monitored using longline surveys. These surveys present challenges that can make obtaining indices of abundance difficult. Issues include gear saturation, which can result in a non-linear relationship between catch per unit effort and local abundance. The current approach to obtain a relative index consists of fitting a multinomial exponential model to a subset of hooks from each survey station. While this approach accounts for hook competition, it does not account for the presence of spatial patterns. We therefore extend the multinomial exponential model to include spatial random fields for both Atlantic halibut and non-target species, set-specific soak time, and data from the hooks. Furthermore, we propose a method for aggregating the resulting spatially varying indices to obtain an annual index for the entirety of the modelled area. This novel approach identifies Atlantic halibut hotspots in multiple years, while simultaneously providing relative abundance indices for 2017 through 2020. These outcomes demonstrate the widespread applicability of our methods for improving the scientific advice upon which fisheries management decisions are based.

Influence of landscape attributes on Virginia opossum density

AbstractThe Virginia opossum (Didelphis virginiana), North America's only marsupial, has a range extending from southern Ontario, Canada, to the Yucatan Peninsula, Mexico, and from the Atlantic seaboard to the Pacific. Despite the Virginia opossum's taxonomic uniqueness in relation to other mammals in North America and rapidly expanding distribution, its ecology remains relatively understudied. Our poor understanding of the ecology of this important mesopredator is especially pronounced in the rural southeastern United States. Our goal was to estimate effects of habitat on opossum density within an extensive multi‐year spatial capture‐recapture study. Additionally, we compared the results of this spatial capture‐recapture analysis with a simple relative abundance index. Opossum densities in the relatively underdeveloped regions of the southeastern United States were lower compared to the more human‐dominated landscapes of the Northeast and Midwest. In the southeastern United States, Virginia opossums occurred at a higher density in bottomland swamp and riparian hardwood forest compared to upland pine (Pinus spp.) plantations and isolated wetlands. These results reinforce the notion that the Virginia opossum is commonly associated with land cover types adjacent to permanent water (bottomland swamps, riparian hardwood). The relatively low density of opossums at isolated wetland sites suggests that the large spatial scale of selection demonstrated by opossums gives the species access to preferable cover types within the same landscape.

Dynamics of indices of the state of the blue king crab stock in the western part of the Bering Sea in 2005–2021

The aim of the research is a retrospective analysis of the stock of the blue king crab Paralithodes platypus inhabiting the western part of the Bering Sea, to show the prospects of using the relative abundance index (I%N) as an assessment characterizing the state of the stock of this species. Material and methods. It is based on the data of direct accounting of P. platypus during trawl and trap surveys in 2005–2021. For each year, an index of relative abundance was established, expressed as a percentage of the maximum number of crabs noted in the retrospective period. The I%N index was determined for different functional groups of the crab separately and for combined size and age groups. New data. The use of the relative abundance index I%N in quartiles makes it possible to apply a four-zonal evaluation characteristic of the stock status of P. platypus: the stock condition is good, satisfactory, uncertain and depressive. This indicative method displays the dynamics of the state of the stock in the studied period and visualizes its variability in the historical period. In the West Bering Sea population of P. platypus, there has recently been a decrease in the number, which is less than 40 % of the maximum number observed during the study period. In all functional groups of P. platypus, the estimate of abundance (stock) is currently characterized as uncertain. Practical significance. The retrospective dynamics of the relative abundance index I%N is an additional operational indicator in making a management decision when developing P. platypus as a commercial reserve unit in the western part of the Bering Sea.

Struktur Komunitas Kupu-Kupu (Lepidoptera: Rhopalocera) di KHDTK Wanadipa Undip Kabupaten Semarang, Jawa Tengah

Kawasan Hutan Dengan Tujuan Khusus (KHDTK) Wanadipa Undip is one part of the Penggaron forest that located in East Ungaran District, Semarang Regency. Part of the KHDTK Wanadipa Undip area has a variety of vegetation that has the potential as a habitat for butterflies. This study aims to analyze the community structure and identify the types of butterflies found in KHDTK Wanadipa Undip, Semarang Regency. Butterflies are one of the herbivores in terrestrial ecosystems that have several roles in the ecological and economic fields. The method used is roaming and point determination using a point count of 4 plots with a distance of 50 meters from each point and a time of ± 20 minutes. The results showed 31 types of butterflies belonging to 5 families. The highest relative abundance index value at 3 stations was found in the species Catopsilia pyranthe, while the lowest was at station 2, namely Euploea mulciber and Hypolimnas bolina species. The diversity index value is 1.43 – 3.12 which is classified as low to moderate. The evenness index value at all stations is classified as almost evenly, which is 0.74 – 0.93. The highest similarity index is found at stations 3 and 4 as well as environmental factor parameters at KHDTK Wanadipa Undip such as altitude, temperature, humidity, wind speed, and light intensity, which are sufficient for butterfly life.

POPULATIONAL ATTRIBUTES OF THE CENTRAL AMERICAN RED BROCKET DEER (Mazama temama) IN THE SIERRA DE ZONGOLICA, VERACRUZ, MEXICO

The Sierra de Zongolica is a biogeographic region with ecosystems and species of nearctic and neotropical affinity in the state of Veracruz, Mexico. However, no studies have been conducted on populations of the red brocket deer (Mazama temama Erxleben 1777) in this region. Such type of studies is essential to propose actions for sustainable management of the species and the habitat by the rural communities. The objective of this study was to describe the populational attributes of M. temama (distribution, population abundance, and patterns of activity) in the Sierra de Zongolica. Information was gathered through interviews, spoor detection and camera trapping from September 2014 to May 2015. To identify the sites where the deer is present, 76 inhabitants of four municipalities of the Sierra de Zongolica were interviewed. In the localities described with presence of the deer, 20 walking trails 300 m long by 1 m wide were identified. Six of the trails were in primary vegetation (1.8 km), 10 in secondary vegetation (3 km), and four in the area of cultivation (1.2 km) where 54 spoors were recorded (45 hoofprints and nine droppings), equivalent to nine signs of deer per km. The population of M. temama was higher in the farming area than in primary or secondary vegetation. In the 43 stations of camera traps, 71 independent images of M. temama were obtained. Of these images, 79 % were between 18:00 and 05:00 h, indicating a pattern of crepuscular and nocturnal activity. This species had a relative abundance index of 2.5 brockets per km2 in the Sierra de Zongolica, suggesting a population susceptible to management under the system of Management Units for Conservation and Sustainable Use of Wildlife (in Mexico, UMAs).

Potential Implications of Excluding Live‐Bottom Habitat from a Bottom‐Trawl Survey in the Eastern Gulf of Mexico

AbstractData provided by the Southeast Area Monitoring and Assessment Program (SEAMAP) shrimp/groundfish trawl survey have long been used in assessing diverse managed taxa, including several reef fishes; however, there are rising concerns over the impacts of trawling on live‐bottom habitats. Using data collected from summer SEAMAP trawl surveys (2009–2016; N = 1,103), we examined how avoiding areas of live‐bottom habitat might affect the survey's ability to assess interannual changes in abundance of managed reef fish taxa. Trawl samples at 48% of sampling sites contained <50 kg of sponge, and 12% of sampling sites contained at least 50 kg of sponge, while 40% of sites had zero sponge bycatch. Mean number of taxa, taxonomic richness, and taxonomic diversity were significantly higher as sponge bycatch increased, while the total number of individuals remained the same. To examine interannual variability of managed reef fish taxa, annual indices of relative abundance were calculated on different subsets of data (all data, data excluding sites with sponge bycatch ≥50 kg, and data excluding all sites with sponge bycatch). For Red Snapper Lutjanus campechanus and pink shrimp Farfantepenaeus duorarum, indices and general trends were largely unaffected by excluding sites with sponge, but for most selected taxa (e.g., Gray Triggerfish Balistes capriscus and Red Grouper Epinephelus morio), overall trends were affected by excluding sites that contained sponge bycatch, and in some cases the frequency of occurrence did not meet the requirement to calculate an index of abundance (i.e., <5%) when sponge sites were excluded (e.g., Hogfish Lachnolaimus maximus). Efforts to mitigate survey interactions with live‐bottom habitats will likely alter the utility of survey data and the ability to assess managed species, so careful consideration is needed to evaluate any trade‐offs between the benefits of the trawl survey for fishery assessments and the benefits of protecting the habitat.

Spatial distribution of potential wild turkey nest predators in west‐central Louisiana

AbstractWild turkey nest success is variable spatially and temporally, with predation being the primary driver of nest loss. Historically, characteristics of nest site vegetation have been used to predict the probability of a nest being successful, a corollary to not being preyed upon. Implicit in nest success studies is that the density, distribution, and habitat preferences of predator species, relative to wild turkey nest distribution, drive the predation risk of nests on the landscape. We quantified diversity of wild turkey nest predator species within 11‐ha incubation ranges centered on active nest sites, scent baited passive nest sites, and scent baited and unbaited random sites and developed a spatially explicit predictive model for potential nest predator distribution based on vegetation and landform characteristics that occurred within incubation ranges. We used 210 camera sites on passive (nesting area from previous year), active (nesting area same year), and random sites over 5,144 trap nights (TN) and recorded 2,925 photographs of potential nest predator species. Relative abundance indices (RAI) indicated greater abundance in passive (14.2/100 TN) and active (12.7/100 TN) nesting sites relative to random sites (3.13/100 TN). For active nesting sites, successful nests had lower RAI (1.8/100 TN) than unsuccessful nests (10.4/100 TN) and lower RAI than baited and unbaited random sites (2/100 TN and 4.3/100 TN, respectively). Our results indicate that potential wild turkey nest predator species regularly occurred within incubation ranges, but were more likely to occur in locations with nests than in random locations on the landscape. We did not document a strong relationship between potential nest predator occurrence and spatial vegetation metrics, which do not appear to affect the occurrence of generalist potential predator species. However, we did show evidence of avoidance by certain potential predators for certain vegetation types. Thus, our work indicated that the most important factor affecting a nest's outcome may be the placement of the nest on the landscape relative to use by potential predator species. We suggest future research evaluate how vegetation characteristics within wild turkey incubation ranges impact nest predator use.

Habitat provision is a major driver of native bird communities in restored urban forests.

Urbanization, and the drastic loss of habitat it entails, poses a major threat to global avian biodiversity. Ecological restoration of urban forests is therefore increasingly vital for native bird conservation, but control of invasive predators may also be needed to sustain native bird populations in cities where species invasions have been particularly severe.We evaluated restoration success by investigating changes in native bird communities along a restoration chronosequence of 25 restored urban forests representing 72 years of forest development, which we compared to two target reference systems and a control system. We hypothesized that total species richness and relative abundance of native forest birds would increase with the age of restoration planting. We further hypothesized that relative abundance of rats, possums and cats would negatively impact native birds, while amount of native forest in the surrounding landscape would have a positive effect.We used structural equation modelling (SEM) to investigate the relative influence of forest structure (complexity index, tree height, canopy openness, basal area, species richness and density), landscape attributes (patch area, perimeter length, landscape composition within three buffer zones, distance to the nearest road and water source) and invasive mammalian predator indices of relative abundance on total species richness and relative abundance of native forest birds.Species richness increased with age of restoration planting, with community composition progressing towards that found in target reference systems. SEM revealed that years restored was a direct driver of bird species richness but an indirect driver of abundance, which was directly driven by canopy openness. Contrary to our predictions, invasive mammals had no significant effect on native bird species richness or abundance.Our results demonstrate that provision and improvement of habitat quantity and quality through restoration is the vital first step to re‐establishing native forest bird communities in cities.

Bird Species Based on Tree Height Perched in the Liwa Botanical Garden, West Lampung Regency

Birds are one of the most diverse animals in the world, especially in Indonesia. Liwa Botanical Garden located in Pekon Kubu Perahu, Balik Bukit District, West Lampung Regency, is a conservation area with the theme of conservation and development of ornamental plants, representing the flora of Southern Sumatra. This research is a continuation of the collaboration between the Department of Biology and Balitbang UPTD Liwa Botanical Garden, West Lampung Regency. The presence of birds in the Liwa Botanical Garden is also a bioindicator of biodiversity for the environment in this area. By maintaining the presence of birds in the Liwa Botanical Garden means protecting their habitat and existing plants. The purpose of this study was to determine the species of birds based on the height of the perched trees in the Liwa Botanical Garden and the abundance of their species. The method used in this research is the point count with the observation time for 9 days in the morning and evening at the height of the tree in 3 different observation stations. Birds on KRL are mostly found on perches at an altitude of 2 - 7 meters, in the category of shrubs and trees, there are 19 out of 25 bird species found. The highest Relative Abundance Index (IKR) was Collocalia esculenta at 39.91% and the lowest IKR value was 7 bird species, each with 0.14% value. The conservation status of the 25 bird species based on IUCN is Least Concern (LC) and based on CITES there is one species that is included in Appendix II, namely Ictinaetus malayensis while based on the Regulation of the Minister of Environment and Forestry of the Republic of Indonesia No. P.20 / MENLHK / SETJEN / KUM.1 / 6/2018 there is one bird species that is included in the protection, namely species Ictinaetus malayensis

Density and Distribution of Principal Prey Species of Tigers and Leopards in Pench Tiger Reserve, Madhya Pradesh

<p>Conservation of large carnivores is dependent on a viable population of their principal prey species. Line transect based density estimation has been established as a robust method for monitoring prey population trend. Chital (<em>Axis axis</em>) and sambar (<em>Rusa unicolor</em>) are the major ungulates in Pench tiger reserve, Madhya Pradesh that are principal tiger and leopard prey. Estimated densities using line transect surveys were highest for chital in the study area with a range of 44–52 individuals per sq. km. from 2013–16. Sambar density remained stable ranging from 5–8 individuals per sq. km. over the three years (2013–16). Camera trap-based encounter rate was used to calculate the Relative Abundance Index of the principal prey species of tigers and leopards in the study area. Spatial distribution pattern using the Relative Abundance Index showed that 47.16% chital captures were congregated near the submergence area whereas 38.53% sambar captures were near rugged areas. Abundant resources and lack of competition from domestic livestock in the core zone contribute to such high estimates of prey population in the study area.</p>

Hyperstability in Electrofishing Catch Rates of Common Carp and Bigmouth Buffalo

AbstractElectrofishing catch per unit effort (CPUE) can be an effective index of relative abundance when CPUE is proportional to population density. However, the relationship between fish catch rates and density can be variable and not proportional because catchability may not be constant under a range of environmental conditions. Hyperstability occurs when catch rates change faster than population density, whereas hyperdepletion occurs when catch rates change slower than population density. We used capture–mark–recapture methods to estimate density of Common Carp Cyprinus carpio and Bigmouth Buffalo Ictiobus cyprinellus across 24 lake‐years. Next, we developed log‐linear mixed‐effects models to assess the relationship between catch rates and density to predict electrofishing CPUE based on density and environmental covariates. Common Carp and Bigmouth Buffalo electrofishing CPUE exhibited hyperstability; CPUE initially increased faster at low density but reached an asymptote as density continued to increase. Common Carp catch rates increased with water temperature and were negatively associated with season; highest catch rates occurred in the warmest temperatures of spring, whereas the lowest catch rates occurred in the coldest temperatures of fall. Bigmouth Buffalo electrofishing CPUE was negatively related to water temperature but had a quadratic relationship with season; catch rates were highest in the spring and fall when water temperatures were coldest. Secchi depth, shoreline length, and maximum depth did not influence our model predictions in either species. Electrofishing had little power to detect simulated changes in Bigmouth Buffalo density regardless of sampling effort, whereas power to detect changes in Common Carp density increase with population changes and sampling effort. At low population densities for both species, electrofishing CPUE is expected to increase or decrease faster than density and can obscure conclusions about population trajectories but may still be useful for monitoring population fluctuations if hyperstability is accounted for by a correction factor.

Catch and effort standardization for Taiwanese swordtip squid Uroteuthis edulis fisheries in the southern East China Sea

The swordtip squid Uroteuthis edulis is a neritic squid species that is widely distributed within the coastal waters of subtropical and tropical Indo-western Pacific regions. This squid is a commercially important species throughout its distribution range and plays a critical role in marine ecosystems. Stock assessments of the squid in the East China Sea (ECS) are scarce, although it is crucial information for the sustainability of the squid and relevant fisheries. The squid was harvested by various fisheries in the southern ECS, which could restrict methods for catch-effort standardization. In this study, catch-effort data of Taiwanese swordtip squid fisheries in the southern ECS between 2002 and 2013 were standardized by the relative catch per unit effort (CPUE) comparison method to examine annual abundance variations of the squid. The results revealed that the standardized CPUE of squid fisheries was lower than the nominal CPUE series. The standardized CPUE of the squid from Taiwanese torch-light vessels revealed slight variability between 2003 and 2009 and great inter-annual variations between 2010 and 2013. The effects of varying parameters on the relative power factor estimates of the vessels are examined and discussed. This study provides an alternative approach of CPUE standardization for swordtip squid fisheries in the southern ECS and a relative abundance index of the squid, which could support further stock assessment and management of fisheries in the region.

MEDIUM- AND LARGE-SIZED MAMMALS AT THE URUCUM MASSIF IN THE BRAZILIAN PANTANAL: CAMERA TRAP AS AN EFFECTIVE SAMPLING METHOD TO ESTIMATE SPECIES RICHNESS, RELATIVE ABUNDANCE, AND ACTIVITY PATTERNS

The Urucum Massif (UM) is recognized as a region of flora and fauna endemism, and it is one of the few mountain ranges found in the western edge of the Brazilian Pantanal, in Mato Grosso do Sul state. Despite the lack of knowledge on mammalian species occurrence, several mining companies established in this region has rapidly changed its landscape. Therefore, this study aims to carry out an inventory of medium- to large-sized mammals in the UM to estimate their relative abundance and activity patterns using data provided by camera trapping surveys. Two main camera-trapping surveys were carried between October 2014 and July 2015, in addition to a small survey in July 2016. Results showed 25 species from medium- to large-sized mammals. Dicotyles tajacu, Dasyprocta azarae and Dasypus novemcinctus presented the highest relative abundance indices. Overall, D. azarae, Nasua nasua and Euphractus sexcinctus were diurnal, while Tamandua tetradactyla, D. novemcinctus, Tapirus terrestris and Sylvilagus paraguensis were nocturnal, in turn, D. tajacu and Cerdocyon thous were associated with the crepuscular period. Overall, 28 % (N = 7) and 12 % (N = 3) of the recorded species are threatened nationally and globally, respectively. Due to the scarcity of protected areas in the UM, we recommend long term monitoring of mammals and ecological studies to support conservation actions for this group in the region

DISTRIBUIÇÃO ESPACIAL DA ICTIOFAUNA E SUA RELAÇÃO COM AS CARACTERÍSTICAS AMBIENTAIS NA MICROBACIA DO CÓRREGO TARUMÃ (ALTO RIO PARANÁ, BRASIL)

The Urucum Massif (UM) is recognized as a region of flora and fauna endemism, and it is one of the few mountain ranges found in the western edge of the Brazilian Pantanal, in Mato Grosso do Sul state. Despite the lack of knowledge on mammalian species occurrence, several mining companies established in this region has rapidly changed its landscape. Therefore, this study aims to carry out an inventory of medium- to large-sized mammals in the UM to estimate their relative abundance and activity patterns using data provided by camera trapping surveys. Two main camera-trapping surveys were carried between October 2014 and July 2015, in addition to a small survey in July 2016. Results showed 25 species from medium- to large-sized mammals. Dicotyles tajacu, Dasyprocta azarae and Dasypus novemcinctus presented the highest relative abundance indices. Overall, D. azarae, Nasua nasua and Euphractus sexcinctus were diurnal, while Tamandua tetradactyla, D. novemcinctus, Tapirus terrestris and Sylvilagus paraguensis were nocturnal, in turn, D. tajacu and Cerdocyon thous were associated with the crepuscular period. Overall, 28 % (N = 7) and 12 % (N = 3) of the recorded species are threatened nationally and globally, respectively. Due to the scarcity of protected areas in the UM, we recommend long term monitoring of mammals and ecological studies to support conservation actions for this group in the region

Comparing relative abundance models from different indices, a study case on the red fox

The correct interpretation of relative abundance indices provided by different sampling methods is essential to correctly estimate population size. Although multiple indices and models have been proposed, their ability to estimate relative abundances and their performance in models explaining abundance trends remains unclear. We used the red fox (Vulpes vulpes) as a model species to compare the relationship and derived models of relative abundance between three indices of relative abundance: RAI (number of captures/total occasions); NI (number of photo-identified individuals) obtained by camera-trapping, and NSE (number of segments with scats) obtained by the scat census sampling method. In addition, we modelled the relationship between a set of habitat predictors and fox relative abundance for each of the three estimated relative abundance indices. We compared the relative abundance models explained for each index against N-mixture models that estimate abundance controlled for variation in detection. Results showed a positive correlation between the RAI and NI indices, while both indices showed a negative relationship with the NSE index. Relative abundance models and N-Mixture models showed a different selection of predictors to explain abundance trends. NSE and RAI indices selected predictors that could explain variability in fox detection rather than fox abundance. In contrast, the NI index and N-Mixture models selected the same predictors to explain fox abundance. Our results suggest the use of the NI index for abundance models without the need to control for variation in detection. Relative abundance indices based on scats and captures per occasion are suboptimal indices for species abundance studies due to possible bias caused by animal behaviour. If count-based methods on captures per occasion (RAI) are selected, we suggest using session-based data processing to incorporate detectability variation in N-mixture models.

Diversity and vertical distribution patterns of wildlife in Tianzhushan, Shaanxi Province, China.

Biodiversity monitoring is an important means by which to evaluate management effectiveness and develop sound conservation plans. In this study, 52 cameras were installed in the study area of Tianzhushan to assess wildlife diversity and elevational patterns from 2018 to 2019. In total, 9 541 independent photos were collected within 26 565 camera-days. We analysed the relative abundance index (RAI), activity patterns and seasonal activity rhythms of the five most abundant species at 200-m elevational intervals throughout the study area (elevation range 1 400–2 000 m a.s.l.). Based on RAI results, the activity patterns of the five most abundant species (i.e. Susscrofa, Naemorhedusgriseus, Muntiacusreevesi, Arctonyxcollaris and Capricornismilneedwardsii) were analysed. Amongst the detected wild mammals, Susscrofa had the highest RAI value of 9.91, while the occurrence of Tamiopsswinhoei had the lowest RAI at 0.004. In addition, there were significant differences in species activity during the daytime and night-time. RAI of the ungulate community peaked at the 1 600–1 800 m a.s.l. elevational range, thus showing a mid-elevational peak pattern. Differences in vertical distribution patterns were detected for the five most abundant species. Mainland serows and wild boars preferred mid-elevation habitats (1 600–1 800 m a.s.l.), long-tailed gorals preferred mid- and high altitudes (1 600–2 000 m a.s.l.) elevation habitats and Chinese muntjacs and hog badgers preferred low elevation habitats (1 400–1 600 m a.s.l.). Taken together, this is the first study to reveal the five dominant species activity patterns in Tianzhushan, which is of importance for wildlife conservation.

Pengaruh Refugia Bunga Telekan (Tagetes erecta) dan Bunga Kertas (Zinnia elegans) pada Populasi Artropoda dan Hasil Tanaman Padi

This study aimed to determine the effect of refugia (Tagetes erecta and Zinnia elegans) plants on the relative abundance and diversity of Arthropod's dominance in the rice plant area and on rice yield. The Arthropods were observed by the visual control method at each rice growth stage. Observations were made during 15 minutes in five plots of rice area and one refugium block at three different times (08.00‒10.00, 12.00‒14.00, and 15.00‒17.00. The morphological features were identified and recorded to identify the species level and grouped according to their ecological niches. The relative abundance and Shannon Diversity Index were calculated. The rice plants' growth data and yield components were analyzed by ANOVA followed by DMRT if there were any significant differences among the treatments. Relative abundance of dominant arthropods on rice land planted with Zinnia elegans was Solenopsis geminata (11.07%), Leptocorisa oratorius (38.37%), and Hypolimnas bolina (0.17%) with species diversity index values of 3.25%; 2.94%, and 2.56%, respectively. In contrast, the relative abundance of arthropods in rice land planted with Tagetes erecta were Cardiochiles philippinensis (8.84%), Oxya chinensis (25.45%), and Scirpophaga incertulas (0.34%) with moderate diversity index values. The Tagetes erecta gave an equivalent result of rice yield with the control, namely 8,10 t/ha and 7,60 t/ha, respectively, while the Zinnia elegans offers rice yield of 6,30 t/ha.
 
 Keywords: arthropod diversity, paddy yield, Tagetes erecta L, Zinnia elegans

Application of Fishery-independent Data as an Alternative Source for Determining Relative Abundance Indices of Blue Marlin, Makaira nigricans (Actinopterygii: Perciformes: Istiophoridae) in the North-eastern Indian Ocean

The present study aimed to determine the abundance index of blue marlin, Makaira nigricans (Lacepède, 1802) utilizing fishery-independent data, i.e., scientific observer, and attempted to bridge the research's gap for low coverage information in the north eastern Indian Ocean. A total of 2,984 set-by-set observer data from 2006-2018, spatially disaggregated by one-degree blocks, were obtained from the Indonesian scientific observer program following commercial longline fleets. A delta-lognormal model was chosen to fit the dataset, using catch as the response variable with seven covariates. A backward procedure based on AIC, BIC and R2 were used to select the best model. Overall, the delta-Gamma performs better when modelling data with a high proportion of zeros than other traditional models. The blue marlin CPUE trend is relatively stable over time, despite the inter-annual fluctuations, which are likely a result of natural variation in the population as opposed to operational changes or inter-annual environmental variation. Given the low spatial coverage compared to logbook data, scientific observer data performed well and produced a robust abundance index of blue marlin in the northeastern Indian Ocean.

Reliable detection of low-density Pacific rats by using camera trapping

Context Long-term monitoring is essential for control and eradication of invasive mammalian predators. Relative abundance indices are increasingly used when assessing population changes. However, indexing assumes constant detectability, when, in fact, it varies depending on numerous factors, including the type and spacing of monitoring devices, seasons, vegetation types, and inter- and intra-specific interactions. Aims We studied a population of Pacific rat (Rattus exulans) and examined the influence of vegetation types, seasons and inter-specific interactions on their detection. Methods We deployed tracking-tunnels, live-traps, chew cards, and trail cameras in three vegetation types during summer and winter. Detection rates of Pacific rats, mice (Mus musculus), stoats (Mustela erminea) and weka (Gallirallus australis) were calculated and compared among vegetation types, seasons and devices. Key results Pacific rats were not detected by any monitoring devices in the farmland, despite their presence in this habitat. In the forest and shrubland, cameras had the highest detection rate among all of the monitoring devices, whereas live-trap and chew cards failed to detect rats. Tracking tunnels detected Pacific rats only in the shrubland. Camera detections of Pacific rats were lower in winter than in summer, and detections were dominated by weka and stoats for both seasons. The seasonal effects may have reflected the population cycle of Pacific rats. Weka and stoats caused substantial physical interference to the tracking tunnels, live-traps and chew cards, which is likely to have deterred Pacific rat interactions through imposing high predation risks. Conclusions Cameras were the most effective device at detecting Pacific rats in low density and under high predator disturbances. Tracking tunnels and chew cards that are successful at detecting other Rattus spp. might not be reliable for detecting Pacific rats. Implications We recommend using camera monitoring for rodents where population density is low, or predator disturbance is high, and species are identifiable from pictures. Studies that draw inferences from relative abundance indices on rodents should exercise caution when rodent detectability is unknown.