Estimate Population Abundance Research Articles

Estimating beluga whale abundance from space: using drones to ground‐validate VHR satellite imagery

AbstractRoutine monitoring of cetaceans is imperative for understanding their population trends and making informed management decisions. However, the inherent nature of cetaceans and the marine ecosystems they inhabit make annual population surveys logistically and economically challenging with current survey methods. One emerging solution is utilizing very high‐resolution (VHR) satellite imagery, which is a logistically efficient method for providing an instantaneous view of areas spanning hundreds of square kilometers. The objective of this study was to determine two factors required to reliably conduct beluga whale population abundance estimates with VHR satellite imagery: (1) depths that beluga whales are visible in VHR satellite images, which are used to define availability bias correction factors, and (2) a comparison of abundance estimates in VHR satellite imagery to current aerial methods. We submerged beluga whale models to different depths in two different water clarities and determined that beluga whales are distinguished only at the surface in turbid water (Secchi depth: 2.56 m) and at depths of 0–2 m in clear water (Secchi depth: 4.04 m). Based on the proportion of time beluga whales spend at these depths, an availability bias correction factor for Western Hudson Bay beluga whales was defined as 2.40 ± 0.16 for turbid water and 1.89 ± 0.05 for clear water. Synchronous ground‐validation surveys determined availability corrected beluga whale abundance estimates in 0.31 m VHR satellite imagery (n = 173 beluga whales) and imagery that was HD sharpened using a proprietary algorithm to approximate 0.15 m resolution (n = 170) to be comparable to drone imagery (n = 164). VHR satellite imagery has the potential to increase the frequency of beluga whale population surveys, which has become increasingly important as beluga whales face rapid ecosystem changes and increased anthropogenic disturbances.

Density estimation of the globally threatened fishing cat Prionailurus viverrinus through a participatory science approach in the Chilika lagoon, eastern India

The fishing cat Prionailurus viverrinus is an Indo-Malayan wetland-dependent felid which is listed as Vulnerable on the IUCN Red List. Its main prey, fish, has low energetic demands and is abundant in productive aquatic habitats. This facilitates high piscivore densities and potentially alters expected scaling patterns that link population density to the body mass of small cats. With local community participation, we estimated the density of the fishing cat in Chilika, Asia’s largest brackish water lagoon, located in the state of Odisha, eastern India, with community participation. The study was carried out in 2 phases in different habitats during 2021 and 2022: a homogeneous marshy habitat and its buffer (Northern Block), and a heterogeneous matrix of different land-use types (Southern Block). We deployed a total of 144 camera traps across 4380 trap nights. Using spatially explicit capture-recapture (SECR), we estimated mean (±SE) fishing cat density to be 0.69 ± 0.1 ind. km-2 in the Northern Block and 0.67 ± 0.33 ind. km-2 in the Southern Block. The population abundance estimates for the Northern and the Southern Blocks were 159 ± 23 and 185 ± 91 respectively. In the former, SECR modelling indicated an effect of anthropogenic habitat modification upon the species’ home range extent. Our density estimates are amongst the highest reported for the species outside protected areas. The results imply that Chilika holds an abundant population of the fishing cat, the continued persistence of which requires mitigation of local and external threats to fish populations. Furthermore, our study, with its inclusive approach, sets a precedent for the use of camera trapping for obtaining robust density estimates of species with uniquely marked individuals in wetland habitats.

Population Abundance and Density Estimates of Poorly Documented Near-Threatened Calabar Angwantibo (Arctocebus calabarensis) in Oban Hills Region.

Population abundance and density estimates play important roles in biodiversity conservation assessment and can lead to prioritization of conservation efforts, strategies, and management. The Calabar angwantibo (Arctocebus calabarensis) is a poorly studied, Near-Threatened nocturnal, arboreal mammal species occurring only in the lowland moist tropical rainforest blocks of southeastern Nigeria and southwestern Cameroon. Like other arboreal nocturnal mammals, there are gaps in knowledge of the distribution and abundance of this species, which may be facing population declines due to habitat loss and hunting. In this study, we investigated the abundance and density of A. calabarensis in the Oban Hills Region of Nigeria. We conducted systematic distance sampling survey along 32 transects in different habitats in a 1227 km of survey efforts. A total of 41 sightings of A. calabarensis were detected, resulting in an abundance of 7345 individuals (95% CI = 1.51-4.37) with an estimated density of 2.57 animals/km2. The estimated population abundance is 6515 individuals in closed-canopy forests and 830 individuals in secondary forests, with encounter rates of 0.52 individual/km2 and 0.60 individuals/km2 in the closed canopy and secondary forest habitats. The global estimates encounter rate of A. calabarensis across the habitat types is 0.33 individuals/km2 and population abundance of 4456 individuals. Our findings indicate that the A. calabarensis populations can adapt to low changes in forest habitat modifications resulting from increasing and widespread forest disturbance by human-dominated activity, which is giving way to forest clearance for agriculture cultivation and infrastructural development. Our findings help to fill a knowledge gap regarding this species and may help establish a baseline for future management, population monitoring, and conservation of the cryptic population of A. calabarensis in Cross-Sanaga Forests.

Using camera traps and N‐mixture models to estimate population abundance: Model selection really matters

Abstract Estimating the abundance or density of wildlife populations is a critical part of species conservation and management, but estimates can vary greatly in precision and accuracy according to the sampling and statistical methods, sampling and ecological variation, and sample size. We used images of moose (Alces americanus) from camera traps to parameterize N‐mixture models and tested the effect of ecological conditions, the spatial scale of measurement, and the criteria used to define independent detections on estimates of population abundance. We compared the model estimates to those generated empirically with aerial survey data, the standard method for many species of ungulate. We explored the sensitivity of estimates to model choice based on the common statistical criterion of parsimony. The two most parsimonious N‐mixture models (i.e. AICc) were considerably biased, producing implausibly large and considerably imprecise estimates of abundance. Most of the other models produced estimates of moose abundance that were ecologically realistic and relatively accurate. The accuracy of population estimates produced by N‐mixture models was not overly sensitive to the formulation of models, the scale at which ecological conditions were measured, or the criteria used to define independent detection and by extension sample size. Our results suggested that parsimony was a poor measure of the predictive accuracy of the population estimates produced with the N‐mixture model. We recommend using a suite of models to generate predictions of abundance instead of the single top‐ranked model. Collecting and processing data from the aerial survey was less expensive and took less time, but data from camera traps provided a broader set of insights into the behaviour of moose and the co‐occurrence of competitors and predators.

Abundance estimation of plains zebras via search–encounter sampling

Spatial capture–recapture (SCR) using search–encounter methods estimate population abundance from encounters of individually recognisable animals along an a priori-designated search path. We applied search–encounter SCR methods and photographic sampling to estimate the abundance of plains zebras (Equus quagga) at Telperion and Ezemvelo nature reserves, South Africa. We analysed encounter data by comparing four hazard-function models for the detection process. The abundance estimate under three models was just above 1000 animals (95% credible intervals c. 960, 1220) versus 811 (719, 917) for the remaining model. The former estimates were broadly similar to aerial counts conducted around the same time. Standard deviation in locations around individual activity centres (σmove\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma _{move}$$\\end{document}) was c. 0.8 km, with little difference between models. In situations where structured surveys are not possible, the approach presented here has the potential to estimate abundance from opportunistic animal encounters (e.g. generated via citizen science schemes) within an SCR framework.

Using Drones to Reveal the Distribution and Population Abundance of Threatened Dasyatid Rays at a Nursery Site in Seychelles

Drones are becoming increasingly valuable tools for studying species in marine environments. Here, a consumer-grade drone was used to elucidate the distribution and population abundance of two threatened dasyatid rays, Pastinachus ater and Urogymnus granulatus, in a remote marine protected area in the Republic of Seychelles. Over six weeks in March and April 2023, a total of 80 survey flights, covering an area of 3.2 km2, recorded 1262 P. ater and 822 U. granulatus. Findings revealed previously unresolved high-use areas for both species, which almost exclusively used sandy areas within the habitat and were found in greater abundances in areas closer to the shoreline. Spatial patterns in abundance were strongly correlated between species, with both often found in mixed-species groups. The site was shown to support large populations of both species with total population abundance estimates of 2524 (2029–3019 95% CI, 0.1 CV) for P. ater and 2136 (1732–2539 95% CI, 0.09 CV) for U. granulatus. This study highlights the applicability of drones in acquiring highly useful data for delineating critical habitats and informing the adaptive management of marine protected areas.

Accounting for unobserved population dynamics and aging error in close-kin mark-recapture assessments.

Obtaining robust estimates of population abundance is a central challenge hindering the conservation and management of many threatened and exploited species. Close-kin mark-recapture (CKMR) is a genetics-based approach that has strong potential to improve the monitoring of data-limited species by enabling estimates of abundance, survival, and other parameters for populations that are challenging to assess. However, CKMR models have received limited sensitivity testing under realistic population dynamics and sampling scenarios, impeding the application of the method in population monitoring programs and stock assessments. Here, we use individual-based simulation to examine how unmodeled population dynamics and aging uncertainty affect the accuracy and precision of CKMR parameter estimates under different sampling strategies. We then present adapted models that correct the biases that arise from model misspecification. Our results demonstrate that a simple base-case CKMR model produces robust estimates of population abundance with stable populations that breed annually; however, if a population trend or non-annual breeding dynamics are present, or if year-specific estimates of abundance are desired, a more complex CKMR model must be constructed. In addition, we show that CKMR can generate reliable abundance estimates for adults from a variety of sampling strategies, including juvenile-focused sampling where adults are never directly observed (and aging error is minimal). Finally, we apply a CKMR model that has been adapted for population growth and intermittent breeding to two decades of genetic data from juvenile lemon sharks (Negaprion brevirostris) in Bimini, Bahamas, to demonstrate how application of CKMR to samples drawn solely from juveniles can contribute to monitoring efforts for highly mobile populations. Overall, this study expands our understanding of the biological factors and sampling decisions that cause bias in CKMR models, identifies key areas for future inquiry, and provides recommendations that can aid biologists in planning and implementing an effective CKMR study, particularly for long-lived data-limited species.

Diadromous fish run assessment: a double-observer model using acoustic cameras to correct imperfect detection and improve population abundance estimates

IntroductionDiadromous fish populations have strongly declined over decades, and many species are protected through national and international regulations. They account for less than 1% of fish biodiversity worldwide, but they are among the most perceptible linkages between freshwater and marine ecosystems. During their migration back and forth, diadromous fish species are subjected to many anthropogenic threats, among which river damming can severely limit access to vital freshwater habitats and jeopardize population sustainability. Here, we developed a method based on a double-observer modeling approach for estimating the abundance of diadromous fish during their migration in rivers.MethodsThe method relies on two independent and synchronous records of fish counts that were analyzed jointly thanks to a hierarchical Bayesian model to estimate detection efficiencies and daily fish passage. We used simulated data to test model robustness and identify conditions under which the developed approach can be used. The approach was then applied to empirical data to estimate the annual silver eel run in the Touques River, France.ResultsThe analysis of simulated datasets and the study case gives evidence that the model can provide robust,accurate, and precise estimates of detection probabilities and total fish abundance in a set of conditions dependent on the information provided in the data (annual distribution of fish passage, annual number of observation, pairing period, etc.).DiscussionThen, the method can be applied to various species and counting systems, including nomad acoustic camera devices. We discuss its relevance for programs on river continuity restoration, notably to quantify population restoration associated with dam removals.

Overcoming data gaps using integrated models to estimate migratory species' dynamics during cryptic periods of the annual cycle

Abstract Environmental and anthropogenic factors affect the population dynamics of migratory species throughout their annual cycles. However, identifying the spatiotemporal drivers of migratory species' abundances is difficult because of extensive gaps in monitoring data. The collection of unstructured opportunistic data by volunteer (citizen science) networks provides a solution to address data gaps for locations and time periods during which structured, design‐based data are difficult or impossible to collect. To estimate population abundance and distribution at broad spatiotemporal extents, we developed an integrated model that incorporates unstructured data during time periods and spatial locations when structured data are unavailable. We validated our approach through simulations and then applied the framework to the eastern North American migratory population of monarch butterflies during their spring breeding period in eastern Texas. Spring climate conditions have been identified as a key driver of monarch population sizes during subsequent summer and winter periods. However, low monarch densities during the spring combined with very few design‐based surveys in the region have limited the ability to isolate effects of spring weather variables on monarchs. Simulation results confirmed the ability of our integrated model to accurately and precisely estimate abundance indices and the effects of covariates during locations and time periods in which structured sampling are lacking. In our case study, we combined opportunistic monarch observations during the spring migration and breeding period with structured data from the summer Midwestern breeding grounds. Our model revealed a nonstationary relationship between weather conditions and local monarch abundance during the spring, driven by spatially varying vegetation and temperature conditions. Data for widespread and migratory species are often fragmented across multiple monitoring programs, potentially requiring the use of both structured and unstructured data sources to obtain complete geographic coverage. Our integrated model can estimate population abundance at broad spatiotemporal extents despite structured data gaps during the annual cycle by leveraging opportunistic data.

Temporal patterns in the soundscape of the port area in an urban estuary

Soundscape ecology, facilitated by the collection of environmental sounds, enables the determination of the area used by specific species, estimation of population abundance, verification of habitat health, and assistance in management and monitoring processes. Estuaries are key environments in the life cycle of many species. As coastal ecosystems, they face potential impacts by human activities. This study aims to characterize the soundscape of the Patos Lagoon estuary (PLE), Brazil, examining its temporal and seasonal variations. Additionally, it seeks to investigate the influence of temperature and salinity on sound pressure levels (SPL) across three different frequency bands throughout the year. For data collection, two autonomous devices - a SoundTrap digital recorder and an F-POD sampler - were used. The data collection spanned from September 2020 to August 2021 and covered one consecutive week per season. The analysis of audio files was performed manually using Raven software. Sound emissions by Lahille's bottlenose dolphin (Tursiops truncatus gephyreus) and fish were observed throughout the sampling period, with peak detections occurring during the summer and spring, respectively. Boat noise was detected throughout the year but more intensely in the summer. Generalized linear models (GLMs) revealed that, for the three SPL frequency bands, the season significantly influenced the composition of the PLE soundscape, with positive fluctuations in the warmer seasons (summer > spring > autumn > winter). Salinity, in turn, showed a slightly negative relationship with the SPL values in the three models, suggesting a decrease in frequencies with increasing salinity. Our results also indicate that the low-frequency SPL, originating mostly from various sources of anthropogenic noise, constitutes the main component of the PLE soundscape. In conclusion, our study provides novel insights into the temporal patterns of the soundscape in an urban estuary, including biotic and anthropogenic sounds, and their relationships with selected environmental variables.

The first use of a photogrammetry drone to estimate population abundance and predict age structure of threatened Sumatran elephants

Wildlife monitoring in tropical rainforests poses additional challenges due to species often being elusive, cryptic, faintly colored, and preferring concealable, or difficult to access habitats. Unmanned aerial vehicles (UAVs) prove promising for wildlife surveys in different ecosystems in tropical forests and can be crucial in conserving inaccessible biodiverse areas and their associated species. Traditional surveys that involve infiltrating animal habitats could adversely affect the habits and behavior of elusive and cryptic species in response to human presence. Moreover, collecting data through traditional surveys to simultaneously estimate the abundance and demographic rates of communities of species is often prohibitively time-intensive and expensive. This study assesses the scope of drones to non-invasively access the Bukit Tigapuluh Landscape (BTL) in Riau-Jambi, Indonesia, and detect individual elephants of interest. A rotary-wing quadcopter with a vision-based sensor was tested to estimate the elephant population size and age structure. We developed hierarchical modeling and deep learning CNN to estimate elephant abundance and age structure. Drones successfully observed 96 distinct individuals at 8 locations out of 11 sampling areas. We obtained an estimate of the elephant population of 151 individuals (95% CI [124, 179]) within the study area and predicted more adult animals than subadults and juvenile individuals in the population. Our calculations may serve as a vital spark for innovation for future UAV survey designs in large areas with complex topographies while reducing operational effort.

Forest Bird Populations at the Big Island National Wildlife Refuge Complex, Hawai‘i

Abstract Endemic Hawaiian forest birds have experienced dramatic population declines. The Big Island National Wildlife Refuge Complex (Refuge Complex) was established for the conservation of endangered forest birds and their habitats. Surveys have been conducted at two units of the Refuge Complex to monitor forest bird populations and their response to management actions. We analyzed survey data from 1987 to 2019 at the Hakalau Forest Unit (HFU) and from 1995 to 2019 at the Kona Forest Unit (KFU). We analyzed three strata at HFU: open-forest, closed-forest, and afforested-pasture, and two strata at KFU: upper (>1,524 m elevation) and lower (<1,524 m). In all years, ‘i‘iwi Vestiaria coccinea, ‘apapane Himatione sanguinea, and Hawai‘i ‘amakihi Chlorodrepanis virens virens were the most abundant species at HFU. Three endangered forest bird species, Hawai‘i ‘ākepa Loxops coccineus, ‘alawī Loxops mana (also known as Hawai‘i creeper) and ‘akiapōlā‘au Hemignathus wilsoni, had much lower densities. The most abundant species at KFU was ‘apapane, followed by Hawai‘i ‘amakihi at much lower densities. We found a continuation of several trends observed in previous analyses at HFU up to 2012, with most species’ trends upward in afforested-pasture stratum, stable in the open-forest stratum, and downward in the closed-forest stratum. However, more species were showing downward trends in all three strata during the most recent decade. Results were mixed at KFU, with most species’ trends downward in the upper stratum and upward in the lower stratum. Populations of endangered species were either locally extirpated at KFU or in numbers too low to reliably estimate population abundance. The Refuge Complex is important for conservation of forest birds on Hawai‘i Island. Our results show that HFU supports the majority of three endangered forest bird species. Threats to forest birds at the Refuge Complex appear to be having a negative impact. These threats include habitat loss, disease, feral ungulates, and nonnative predators. Continuing and enhancing management actions, such as forest restoration and removal of invasive species, could help mitigate these impacts and allow the Refuge Complex to remain a key site for forest bird conservation in Hawai‘i.

Movement dynamics influence population monitoring and adaptive harvest management strategies in migratory birds

Informed population monitoring efforts are essential for sound management of harvested species, and adaptive strategies that provide detailed information to monitoring efforts often require data inputs from complimentary sources. Movement ecology information is seldom directly incorporated into population monitoring or adaptive harvest management strategies, yet can provide valuable information on species distributions, emigration and immigration rates, and aid in determining optimal population monitoring timing. The Rocky Mountain Population (RMP) of Sandhill Cranes is a harvested population subject to a stringent adaptive harvest management framework and an annual aerial survey to estimate population abundance, but movements of Sandhill Cranes during survey windows, and subsequent changes to harvest quotas based on their movement and distribution have not been investigated. We used seven years of GPS tracking data to estimate state-specific emigration and immigration rates, using a Bayesian multi-state capture-recapture model, among states within the RMP distribution to understand how seasonal crane movements may influence optimal aerial survey timing. We then leveraged these transition probabilities in conjunction with aerial survey count data to model how changes in aerial survey timing and movement-informed crane distribution would influence the current RMP Sandhill Crane adaptive harvest management model resulting in estimated changes to harvest allocation among states based on Sandhill Crane movement. We found that Sandhill Crane emigration from northern states began to increase the week of the aerial survey in late September, and continued to increase as autumn migration progressed into October. As expected, immigration to southern states began as emigration from northern states increased. Importantly, little movement among states occurred prior to the current aerial survey design timing. Overall, we found that current survey timing and shortly thereafter (∼1 week) did not greatly influence estimates of Sandhill Crane distribution, and did not greatly influence the harvest reallocation to each state until mid to late October (range of −42–+52 tag allocation change), much later than the current survey design would allow. Using GPS locations, we found that optimal population monitoring efforts could be improved to account for both detection and seasonal movements, while minimally influencing current adaptive harvest management strategies to stakeholders. Linking movement ecology with population monitoring efforts and subsequently adaptive harvest management strategies yields insightful information that can be beneficial for conservation planning, decision-making, and optimal species management of a migratory bird.

Population size and demographic parameters of pantropical spotted dolphin (Stenella attenuata graffmani) (Cetartiodactyla: Delphinidae) in Golfo Dulce, Costa Rica

Introduction: The coastal form of pantropical spotted dolphins (Stenella attenuata graffmani) is commonly found along the Pacific coast of Costa Rica. Within Golfo Dulce, a fiord-like-embayment bordering the Osa Peninsula, pantropical spotted dolphins are sympatric with inshore bottlenose dolphins (Tursiops truncatus) and these marine predators provide an important source of revenue for local communities through boat-based tours.
 Objective: Here we estimated the population size and demographic parameters of the coastal pantropical spotted dolphins in Golfo Dulce.
 Methods: The study area was surveyed using non-random boat surveys. Upon encounter, dolphins were individually photo-identified using natural marks in their dorsal fins to estimate population abundance and survival using three emigration scenarios.
 Results: A total of 280 dolphins were photoidentified, 65 % of which were observed only once. A total of 30 models were produced, and only two were considered to be parsimonious. Both models explain seasonal apparent survival and its variation due to heterogeneity in capture-recapture probability, one under no emigration (ΔQAICc = 0.00) and the other under random emigration (ΔQAICc = 1.72). We deemed the latter to be a more realistic model as it better reflects our in-situ observations. Under this preferred model the population size of pantropical spotted dolphins in Golfo Dulce varied from 187.30 individuals (CI: 168.67 – 208.02, CV: 0.11) to 367.88 individuals (CI: 341.51 – 396.31, CV: 0.07), with no significant differences in abundance due to seasonality and very high apparent survival (S = 0.98, CI: 0.68 – 0.99, SE: 0.02).
 Conclusions: The number of identified dolphins and the proportion of individuals seen only once suggest the fluid movement of the population in and out of the gulf. However, the population size and demographic estimates are characterized by several identified individuals regularly recaptured inside the gulf. This group of dolphins appears to favor the inner basin as a critical foraging habitat. Given the increase of anthropogenic impacts within Golfo Dulce, future management and conservation efforts will require the recognition of an ecologically discrete population unit of coastal pantropical spotted dolphins within the gulf.

Abundance and population growth estimates for bare-nosed wombats.

Wildlife managers often rely on population estimates, but estimates can be challenging to obtain for geographically widespread species. Spotlight surveys provide abundance data for many species and, when conducted over wide spatial scales, have potential to provide population estimates of geographically widespread species. The bare-nosed wombat (Vombatus ursinus) has a broad geographical range and is subject to spotlight surveys. We used 19 years (2002-2020) of annual spotlight surveys to provide the first estimates of population abundance for two of the three extant bare-nosed wombat subspecies: V. u. ursinus on Flinders Island; and V. u. tasmaniensis on the Tasmanian mainland. Using distance sampling methods, we estimated annual rates of change and 2020 population sizes for both subspecies. Tasmanian mainland surveys included habitat data, which allowed us to also look for evidence of habitat associations for V. u. tasmaniensis. The average wombat density estimate was higher on Flinders Island (0.42 ha-1, 95% CI = 0.25-0.79) than on the Tasmanian mainland (0.11 ha-1, CI = 0.07-0.19) and both wombat subspecies increased over the 19-year survey period with an estimated annual growth rate of 2.90% (CI = -1.7 to 7.3) on Flinders Island and 1.20% (CI = -1.1 to 2.9) on mainland Tasmania. Habitat associations for V. u. tasmaniensis were weak, possibly owing to survey design; however, we detected regional variation in density for this subspecies. We estimated the population size of V. u. ursinus to be 71,826 (CI = 43,913-136,761) on Flinders Island, which when combined with a previously published estimate of 2599 (CI = 2254-2858) from Maria Island, where the subspecies was introduced, provides a total population estimate. We also estimated 840,665 (CI = 531,104-1,201,547) V. u. tasmaniensis on mainland Tasmania. These estimates may be conservative, owing to individual heterogeneity in when wombats emerge from burrows. Although these two subspecies are not currently threatened, our population estimates provide an important reference when assessing their population status in the future, and demonstrate how spotlight surveys can be valuable to inform management of geographically widespread species.

Estimating abundance of Eastern Canada-West Greenland bowhead whales using genetic mark-recapture analyses

The Eastern Canada-West Greenland (EC-WG) bowhead whale (Balaena mysticetus) population is widely distributed across the eastern Canadian Arctic and across Baffin Bay to the western coast of Greenland. Their vast distribution makes obtaining population estimates via aerial surveys difficult, as coverage over their entire range is not possible. Genetic mark recapture analyses address this issue, as biopsy samples can be collected at various locales across the EC-WG bowhead whale population’s distribution and microsatellites can be analyzed to identify unique individuals. EC-WG bowhead whales were subject to intense commercial whaling pressure between the early 1700 s and early 1900 s, after which a moratorium on commercial whaling was put in place in 1915. We used available genetic samples from EC-WG bowhead whales in mark recapture models to estimate population abundance from 2012 to 2021 to gain insight on population dynamics ∼100 years post commercial whaling. The preferred model, using a Jolly-Seber structure, estimated the total abundance as 5173 individuals (CI: 3436–7788). Since the cessation of commercial whaling, the population has been thought to be rebounding, which is reflected by gradually increasing abundance estimates, from the low hundreds in the 1970 s and 1980 s, to ∼6000 in the early 2000 s, but our present estimate suggests population abundance may be plateauing well below the pre-commercial whaling carrying capacity estimate. This population estimate for EC-WG bowhead whales is required to update the population dynamics for conservation efforts.

Estimating Population Abundance Of Seahorse In Sebong Bay, Bintan Island

The decline in seahorse populations in the wild due to high fishing activity and habitat degradation prompted the inclusion of all seahorse species in Appendix II of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) in 2002. By being included in Appendix II of CITES, data and information on the abundance of seahorse populations become crucial as the basis for determining the quota for fishing and trade. Estimating population abundance of seahorse requires knowledge of habitat area, which can be modeled using the MaxEnt (maximum entropty). In this study, an estimation of the abundance of seahorses was carried out in the waters of Sebong Bay, Bintan Island. MaxEnt modeling was implemented with data on seahorse presence locations and environmental parameter maps consisting of chlorophyll-a as primary productivity parameter, benthic habitat as habitat type parameter, and dissolved oxygen, salinity, and pH as physiological parameters. From this model, the value of the area of suitable habitat for seahorses is 54,6 ha, while the density of seahorse in this area is 60 ind/ha, so it can be determined that the abundance of seahorses in the Sebong Bay is 3.276 individuals. Therefore, seahorse population in Sebong Bay is critically endangered since it is below the number of individuals that required to prevent the loss of quantitative genetic variation in a species.

Processes driving individual variation in environmental DNA deposition rates in Daphnia magna

AbstractThe abundance of environmental DNA (eDNA) in water samples has been proposed as a sensitive, cost‐efficient, and non‐invasive alternative to infer population abundance and biomass, regardless of the acknowledgment that a number of biotic and abiotic factors can lead to substantially varying rates of eDNA deposition among organisms in a population. We tested how metabolic, nutritional, and life history processes shape intraspecific eDNA deposition rates in the freshwater invertebrate Daphnia magna. We extracted water samples from individual D. magna raised in glass vials under a 2 × 2 longitudinal factorial manipulation of temperature and food levels over their entire lifespan, and quantified eDNA daily deposition rates using digital droplet PCR (ddPCR). Analyzed using a hypothesis‐driven nested mixed‐effect modeling framework, we showed that per individual D. magna eDNA deposition rate varied by an order of magnitude over the course of each individual's lifespan due to multiple causes. We identified that large and pregnant D. magna had the highest eDNA deposition rates, particularly under warmer conditions with higher food levels, and thus, should be considered a prime target for field detections. We found that recently deceased individuals could potentially bias eDNA monitoring efforts by releasing a relatively higher amount of eDNA through decomposition. Our work supplies a more nuanced understanding of myriad factors that shape eDNA deposition, suggesting new and more useful ways to interpret eDNA monitoring data. We recommend that future work using eDNA to estimate population abundance or biomass should account for both energetic conditions and the reproductive cycle facing their target organism and prioritize sampling effort toward metabolically active individuals, especially when working with size‐structured populations that exhibit wide variation in body mass.

Lake Sturgeon population trends in the St. Clair–Detroit River system, 2001–2019

AbstractObjectiveThe Lake Sturgeon Acipenser fulvescens is listed as threatened or endangered in 15 states or provinces within the species' native range. Accordingly, investments in habitat and population restoration for this species have increased throughout the Great Lakes. To aid in the evaluation of restoration efficacy, robust population parameters are needed to inform management decisions. The St. Clair–Detroit River system (SCDRS) contains one of the largest self‐sustaining Lake Sturgeon populations in the Great Lakes; however, recent estimates of population abundance and growth parameters have not been assessed.MethodsOur study used baited setline and mark–recapture data collected between 2001 and 2019 to estimate whether the number of Lake Sturgeon captured varied annually and/or with water temperature and whether population abundance and the population growth rate (λ) varied among three subpopulations located in the SCDRS.ResultTrends in the number of Lake Sturgeon captured on setlines varied among subpopulations and by life stage. Annual trends in the number of Lake Sturgeon captured remained consistent over time in the upper St. Clair River, decreased for adults and increased for subadults in the lower St. Clair River, and increased in the Detroit River. With subpopulation abundances of 20,184 (95% confidence interval [CI] = 12,533–27,816) in the upper St. Clair River/southern Lake Huron, 6523 (95% CI = 5720–7327) in the lower St. Clair River, and 6416 (95% CI = 4065–8767) in the Detroit River, our study confirms that the SCDRS contains the largest Lake Sturgeon population with unimpeded access to the Great Lakes. The geometric mean λ for all subpopulations indicated stable populations and ranged from 1.00 to 1.16.ConclusionOur study provides an updated assessment of Lake Sturgeon population parameters that serve as a baseline to evaluate habitat restoration efforts and to inform management of the SCDRS recreational Lake Sturgeon fishery.

SNP Panel and Genomic Sex Identification in Atlantic Halibut (Hippoglossus hippoglossus).

The ability to identify sex is necessary in population biology for a proper understanding of the dynamics of a population. In Atlantic halibut, phenotypic sex identification is not possible due to the lack of significant external morphological differences. We developed an Illumina SNP panel for Atlantic halibut with 4000 SNPs spread evenly throughout the genome with a minor allele frequency MAF ≥ 0.4, except for N = 249 SNPs located in a sex-determining region on chromosome 12, N = 176 of these SNPs were selected to genetically identify male and female individuals using a DAPC analysis. The genomic identification of sex allows for non-lethal sex determination and validation of sex identification in the field. The SNP panel is a new genomic resource for Atlantic halibut that will make it possible to generate the genotypic data for the large number of individuals needed to estimate population abundance using genomics and the Close Kin Mark Recapture (CKMR) approach, an emerging component of fisheries management and stock monitoring.