Harvest Management Strategies Research Articles

Urban water system of the National Capital Territory of Delhi: a comprehensive study

ABSTRACT This study examines the intricate relationship between Delhi's urban water system, with a specific emphasis on the challenges posed by urbanization, and environmental factors. The study investigates the present conditions of the water resources, infrastructure, and governance in the National Capital Territory (NCT) of Delhi. The study identifies significant difficulties, such as depletion of groundwater and inadequate access to water. Additionally, it examines innovative approaches to supply internalization such as rainwater harvesting, wastewater recycling, and demand management strategies. Therefore, this document establishes the path for future research endeavours and policy suggestions that attempt to promote a fair, effective, and environmentally sustainable water future in Delhi.

Alfalfa‐bermudagrass mixtures managed under contrasting harvest strategies in the southeastern US

AbstractThe incorporation of dual‐purpose alfalfa (Medicago sativa L.) cultivars into bermudagrass (Cynodon spp.) is a viable option to extend the grazing season in Southern forage systems. However, data are limited on which harvest management strategy (HMS) optimizes the use of alfalfa‐bermudagrass (ABG) mixtures in the Southern US. A two‐year study evaluated ABG mixtures under three HMS [cut only (CO), graze only (GO), or cut and graze (CG)].in Headland, AL and Tifton, GA. Alfalfa‐bermudagrass mixtures utilized in this evaluation were ‘Bulldog 805’ alfalfa that was interseeded into ‘Tifton 85’ bermudagrass. Treatments were evaluated for forage, animal, and total system performance. Herbage accumulation varied by year and location (p < .01), but the number of harvests ultimately determined the total forage produced. Forage allowance was never limiting but did differ among treatments at Tifton, GA (p = .02). The CG HMS allowed for similar daily (p > .06) and liveweight gains (p > .56) on fewer days of grazing as compared to the GO treatments. The greater alfalfa percentage in the CG HMS translated to greater total digestible nutrients (TDN) and crude protein (CP), though not always statistically different. The CO HMS maximized system performance when evaluated for total gain (actual gains + predicted gains). However, the CG management allowed for more production opportunities across the season, thereby reducing economic risk. Future research should focus on evaluating the economic implications of introducing each HMS into ABG systems.

Reproductive Capabilities of Female Nilgai (Boselaphus tragocamelus) in Southern Texas.

Free-ranging nilgai antelope (Boselaphus tragocamelus) are an understudied species, both on their native ranges of India, Pakistan, and Nepal and on their introduced ranges in southern Texas. Basic data related to population sizes, survival, reproduction, and recruitment are needed throughout their range to inform management and conservation decisions. We collected nilgai fetuses from 3 ranches in southern Texas, including East Foundation's El Sauz and Santa Rosa ranches, and the Norias Division of the King Ranch® from 2018-2021. We calculated the percentage of individuals that were pregnant in each of the sample years and overall. We determined monthly average, maximum, and minimum fetus length. Of 488 nilgai cows, we found 386 to be pregnant (79%) and 214 to be pregnant with twins (56%). We found nilgai cows as young as 1-year old to have fetuses and therefore to have reached sexual maturity. Sex ratios of fetuses during any sampling year did not differ. We found ample evidence supporting our hypothesis that nilgai are fecund on their introduced range of southern Texas. To prevent nilgai overpopulation and associated problems, harvest management strategies should be implemented, specifically on nilgai cows.

Pre-Harvest Corn Grain Moisture Estimation Using Aerial Multispectral Imagery and Machine Learning Techniques

Corn grain moisture (CGM) is critical to estimate grain maturity status and schedule harvest. Traditional methods for determining CGM range from manual scouting, destructive laboratory analyses, and weather-based dry down estimates. Such methods are either time consuming, expensive, spatially inaccurate, or subjective, therefore they are prone to errors or limitations. Realizing that precision harvest management could be critical for extracting the maximum crop value, this study evaluates the estimation of CGM at a pre-harvest stage using high-resolution (1.3 cm/pixel) multispectral imagery and machine learning techniques. Aerial imagery data were collected in the 2022 cropping season over 116 experimental corn planted plots. A total of 24 vegetation indices (VIs) were derived from imagery data along with reflectance (REF) information in the blue, green, red, red-edge, and near-infrared imaging spectrum that was initially evaluated for inter-correlations as well as subject to principal component analysis (PCA). VIs including the Green Normalized Difference Index (GNDVI), Green Chlorophyll Index (GCI), Infrared Percentage Vegetation Index (IPVI), Simple Ratio Index (SR), Normalized Difference Red-Edge Index (NDRE), and Visible Atmospherically Resistant Index (VARI) had the highest correlations with CGM (r: 0.68–0.80). Next, two state-of-the-art statistical and four machine learning (ML) models (Stepwise Linear Regression (SLR), Partial Least Squares Regression (PLSR), Artificial Neural Network (ANN), Support Vector Machine (SVM), Random Forest (RF), and K-nearest neighbor (KNN)), and their 120 derivates (six ML models × two input groups (REFs and REFs+VIs) × 10 train–test data split ratios (starting 50:50)) were formulated and evaluated for CGM estimation. The CGM estimation accuracy was impacted by the ML model and train-test data split ratio. However, the impact was not significant for the input groups. For validation over the train and entire dataset, RF performed the best at a 95:5 split ratio, and REFs+VIs as the input variables (rtrain: 0.97, rRMSEtrain: 1.17%, rentire: 0.95, rRMSEentire: 1.37%). However, when validated for the test dataset, an increase in the train–test split ratio decreased the performances of the other ML models where SVM performed the best at a 50:50 split ratio (r = 0.70, rRMSE = 2.58%) and with REFs+VIs as the input variables. The 95:5 train–test ratio showed the best performance across all the models, which may be a suitable ratio for relatively smaller or medium-sized datasets. RF was identified to be the most stable and consistent ML model (r: 0.95, rRMSE: 1.37%). Findings in the study indicate that the integration of aerial remote sensing and ML-based data-run techniques could be useful for reliably predicting CGM at the pre-harvest stage, and developing precision corn harvest scheduling and management strategies for the growers.

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.

Insights into the Mitochondrial Genetic Makeup and Miocene Colonization of Primitive Flatfishes (Pleuronectiformes: Psettodidae) in the East Atlantic and Indo-West Pacific Ocean.

The mitogenomic evolution of the Psettodes flatfishes is still poorly known from their range distribution in eastern Atlantic and Indo-West Pacific Oceans. The study delves into the matrilineal evolutionary pathway of these primitive flatfishes, with a specific focus on the complete mitogenome of the Psettodes belcheri species, as determined through next-generation sequencing. The mitogenome in question spans a length of 16,747 base pairs and comprises a total of 37 genes, including 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and a control region. Notably, the mitogenome of P. belcheri exhibits a bias towards AT base pairs, with a composition of 54.15%, mirroring a similar bias observed in its close relative, Psettodes erumei, which showcases percentages of 53.07% and 53.61%. Most of the protein-coding genes commence with an ATG initiation codon, except for Cytochrome c oxidase I (COI), which initiates with a GTG codon. Additionally, four protein-coding genes commence with a TAA termination codon, while seven others exhibit incomplete termination codons. Furthermore, two protein-coding genes, namely NAD1 and NAD6, terminate with AGG and TAG stop codons, respectively. In the mitogenome of P. belcheri, the majority of transfer RNAs demonstrate the classical cloverleaf secondary structures, except for tRNA-serine, which lacks a DHU stem. Comparative analysis of conserved blocks within the control regions of two Psettodidae species unveiled that the CSB-II block extended to a length of 51 base pairs, surpassing the other blocks and encompassing highly variable sites. A comprehensive phylogenetic analysis using mitochondrial genomes (13 concatenated PCGs) categorized various Pleuronectiformes species, highlighting the basal position of the Psettodidae family and showed monophyletic clustering of Psettodes species. The approximate divergence time (35-10 MYA) between P. belcheri and P. erumei was estimated, providing insights into their separation and colonization during the early Miocene. The TimeTree analysis also estimated the divergence of two suborders, Psettodoidei and Pleuronectoidei, during the late Paleocene to early Eocene (56.87 MYA). The distribution patterns of Psettodes flatfishes were influenced by ocean currents and environmental conditions, contributing to their ecological speciation. In the face of climate change and anthropogenic activities, the conservation implications of Psettodes flatfishes are emphasized, underscoring the need for regulated harvesting and adaptive management strategies to ensure their survival in changing marine ecosystems. Overall, this study contributes to understanding the evolutionary history, genetic diversity, and conservation needs of Psettodes flatfishes globally. However, the multifaceted exploration of mitogenome and larger-scale genomic data of Psettodes flatfish will provide invaluable insights into their genetic characterization, evolutionary history, environmental adaptation, and conservation in the eastern Atlantic and Indo-West Pacific Oceans.

Population dynamics and harvest management of eastern mallards

AbstractManaging sustainable harvest of wildlife populations requires regular collection of demographic data and robust estimates of demographic parameters. Estimates can then be used to develop a harvest strategy to guide decision‐making. Mallards (Anas platyrhynchos) are an important species in the Atlantic Flyway for many users and they exhibited exponential growth in the eastern United States between the 1970s and 1990s. Since then, estimates of mallard abundance have declined 16%, prompting the Atlantic Flyway Council and United States Fish and Wildlife Service to implement more restrictive hunting regulations and develop a new harvest strategy predicated on an updated population model. Our primary objective was to develop an integrated population model (IPM) for use in an eastern mallard harvest management strategy. We developed an IPM using annual estimates of breeding abundance, 2‐season banding and recovery data, and hunter‐harvest data from 1998 to 2018. When developing the model, we used novel model selection methods to test various forms of a sub‐model for survival including estimating the degree of harvest additivity and any age‐specific trends. The top survival sub‐model included a negative annual trend on juvenile survival. The IPM posterior estimates for population abundance tracked closely with the observed estimates and estimates of mean annual population growth rate ranged from 0.88 to 1.08. Our population model provided increased precision in abundance estimates compared to survey methods for use in an updated harvest strategy. The IPM posterior estimates of survival rates were relatively stable for adult cohorts, and annual growth rate was positively correlated with the female age ratio, a measure of reproduction. Either or both of those demographic parameters, juvenile survival or reproduction, could be a target for management efforts to address the population decline. The resulting demographic parameters provided information on the equilibrium population size and can be used in an adaptive harvest strategy for mallards in eastern North America.

Effect of plant spacing and cutting intensity on the morphology and productivity of forage cactus [Opuntia stricta (Haw.) Haw.

The forage cactus cultivar Mexican elephant ear (MEE) [Opuntia stricta (Haw.) Haw.] has been widely used in the semi-arid of Brazil because of its resistance to carmine mealybug. Therefore, it is necessary to establish planting and harvesting management strategies for this cultivar. This study evaluated the effect of cutting intensity (preservation mother cladode, and mother + primary cladodes) and different planting densities (55 555; 27 777; 13 888 and 6 944 plants ha−1) on the morphology and productivity of the forage cactus cv. MEE, in 10-year-old cultivation under rainfed conditions. A split-plot design was used where planting density was allocated to the main plots and harvesting intensity to the sub-plots. Each treatment combination was replicated four times. The data were submitted to ANOVA, Tukey’s test, and principal component analysis at 5% (p < 0.05). Post-harvesting preservation of the primary cladodes promoted greater dry matter production (9.2 t ha−1 year−1), crop water accumulation (86.6 t ha−1 year−1), and rainwater use efficiency (11.4 kg of DM mm−1) (p < 0.01). Primary cladodes preservation positively influenced the productive characteristics of the forage cactus, and the planting density of 13 888 plants ha−1 (0.72 m2) favoured the productivity of this cultivar. These findings can guide planting and harvesting strategies for cultivating MEE cactus.

Migratory connectivity of North American waterfowl across administrative flyways.

Management of waterfowl that migrate seasonally across North America occurs within four flyways that were delineated in the early 1900s to include the annual movements of populations. Movements may have changed over the past century since the administrative flyways were established, and may do so while management plans are in use, so information about transitions among flyways through time can illustrate how management assumptions may change. Today there are more than 12 million records from 60 years of migratory waterfowl band recoveries to assess adaptive management approaches that will be most effective when they account for movements within and between flyways. We examined how much the movement of North American waterfowl occurs between flyways, whether those movements have changed through time, and whether movements of mallards are representative of multiple species, as suggested by current harvest management strategies. We estimated the probability a duck would transition from one flyway to another and the strength of migratory connectivity (MC) for each species within and among flyways. We used capture-mark-recovery models to estimate population-specific movement within and among flyways (transition probabilities) for 15 migratory waterfowl species that were banded during breeding and recovered during winter. We developed new functionality in the R package MigConnectivity to estimate the species-specific strength of MC using transition probability samples from the capture-mark-recovery models. We found the regular movement of duck populations among flyways, overall weak MC, and no consistent change in migratory movements through time. Mallard movements were median among all duck species, but significantly different from many species, particularly diving ducks. Despite the significant movement between flyways, our work suggests flyway management of waterfowl matches many of the seasonal movements of these species when considering mid-continent flyway management. We recommend models accounting for all transition probabilities between populations and regularly estimating harvest derivations, transition probabilities, and MC metrics to verify that the current movements match model assumptions.

Pathogen‐mediated selection and management implications for white‐tailed deer exposed to chronic wasting disease

Abstract Pathogens can cause host extinction, affect population dynamics and influence natural selection. Host susceptibility to pathogens can vary by species, demographics and genetics which affect epizootic and population dynamics, ultimately determining population trends and evolution. Chronic wasting disease (CWD), a fatal neuro‐degenerative prion disease of cervids, has varying host susceptibility conferred by polymorphisms of the prion protein gene (PRNP) at codon 96 for white‐tailed deer Odocoileus virginianus. Deer with the homozygous Glycine allele (96GG) are most susceptible and a single Serine allele (96GS/96SS) reduces the risk of infection and mortality. We developed epizootiological models that demonstrate CWD infection and disease‐associated mortality were higher for the more susceptible (96GG) genotype; and, infection was higher for males than females. We used population models to evaluate future shifts in genotype frequencies under alternative harvest and infection rate scenarios. Genetic shifts towards less susceptible genotypes were predicted as CWD prevalence increased during the course of an outbreak. This further increased CWD prevalence, and likely environmental contamination from prion shedding, due to longer incubation periods. Alternative harvest management strategies directly influenced CWD prevalence and spread, the rate of genetic selection and deer population growth. Synthesis and applications. We show that chronic wasting disease (CWD) transmission varied by sex, age class and PRNP genotype, and that CWD disease‐associated mortality varied by genotype. Together, these forces lead to CWD‐mediated genetic selection for a white‐tailed deer population. We predict that genetic selection pressure increases when hunter harvest pressure is lowered, and conversely, increasing hunter harvest can reduce genetic selection rates of antlered deer. Our results support the control of CWD prevalence by aggressive harvest of adult males, because they have the highest infection rates. Our results have strong implications for evolution, disease ecology, geographical spread, disease mitigation and cervid population management.

Land-sharing logging is more profitable than land sparing in the Brazilian Amazon

Selective logging is pervasive across the tropics and a key driver of forest degradation. Two competing harvest management strategies have been proposed: Land sharing via low-intensity logging throughout a concession; and high-intensity land-sparing logging across a smaller area, protecting part of the concession as primary forest. Empirical research points to land sparing being more optimal for maintaining biodiversity and carbon, especially under secure land tenure, but a key question for forest-based economies is how each strategy affects the profitability of logging. We combine detailed financial data with harvest simulations to assess the profitability of land-sharing and land-sparing logging in the Brazilian Amazon. Under business-as-usual, land-sharing is significantly more profitable than land-sparing logging, whether sparing is conducted in a single block or targeting the highest-density timber stocks, highlighting a conflict between economic and conservation priorities. Land-sharing logging is also more profitable than hybrid strategies whereby a mix of land-sharing and land-sparing logging is employed. Conservation-based restrictions that apply quotas on species in different size classes reduces the opportunity cost of land sparing, but even under tight restrictions land sharing remains more profitable and land sparing often returns a loss. Additional financial incentives, including timber certification schemes and carbon-based payment for ecosystem services, are needed to bridge the opportunity cost of land-sparing logging and minimise ecological damage to tropical rainforests.

Eco-archaeological excavation techniques reveal snapshots of subterranean truffle growth

Despite its status as a highly-prized and coveted fungi in gastronomy, many aspects of the subterranean life cycle of the Burgundy truffle (Tuber aestivum) are still unknown, because in situ observations of the formation and maturation of truffle fruitbodies remain difficult. Here, we adopted a suite of archaeological fine-scale excavating techniques to provide unique spatiotemporal snapshots of Burgundy truffle growth at three sites in southern Germany. We also recorded the relative position, fresh weight, maturity level and genotype composition of all excavated fruitbodies. Varying by a factor of thousand, the fresh weight of 73 truffle ranged from 0.1 to 103.2 g, with individual maturity levels likely representing different life cycle stages from completely unripe to fully ripe and even decaying. While only a slightly positive relationship between fruitbody weight and maturity level was found, our results suggest that genetically distinct specimens can exhibit different life cycle stages at the same period of time and under the same environmental conditions. We therefore argue that truffles are likely able to grow, mature and ripe simultaneously between early summer and late winter of the following year. Our case study should encourage further eco-archaeological truffle excavations under different biogeographic settings and at different seasons of the year to gain deeper insights into the fungi's subterranean ecology. The expected cross-disciplinary findings will help truffle hunters and farmers to improve their harvest practices and management strategies.

Relationship and Distribution of In-Field Dry-Down and Equilibrium in Maize Grain Moisture Content

The selection of the appropriate harvest time and moisture content (MC) is very important for maize (Zea Mays L.) production, and selection is an essential step that balances the yield and comprehensive benefits. In this study, the process and final MC following a grain dry-down of sixteen maize hybrids was observed in 2017 and 2018. The Guggenheim-Anderson-de Boer (GAB) model, which is commonly used to describe the equilibrium moisture content (Meq) under controlled conditions, was used to evaluate the relationship between the field Meq and the final MC. The results showed that the MC reached a stable level after a long dry-down period in the field, indicating that an equilibrium was present between the grain and the atmosphere. The MC at the equilibrium state represented two characteristics, a “hysteresis effect” and a “convergence effect”, which were as follows: the change in MC always lagged behind the Meq in the atmosphere; and the MC fluctuated continuously with the Meq but could not reach its limit. The time of the “hysteresis effect” was estimated to be approximately 2-4 days. The time to reach equilibrium varied greatly in different maize hybrids, and it was related to the growth period and dry-down characteristics. Moreover, the various climatic types contributed to diverse Meq values, and the humid climate had a higher Meq than the dry-cold climate. The distribution of Meq values and the drying days on which the maize grain moisture content decreased from 30% to 25% (and 20%), guided the threshold for the delayed harvest of maize, as also estimated in various maize ecological areas in China. The optimal harvest time were significantly different in various regions due to different Meq values. Therefore, we suggest that the estimation of the Meq could be an important indicator for predicting the grain dry-down and harvest management strategies for a region.

Monitoring, modeling and harvest management of non-native invasive green iguanas on Grand Cayman, Cayman Islands

The green iguana (Iguana iguana) was most likely introduced as a pet and became overabundant during the last 20 years on Grand Cayman. Because negative impacts were unmanageable (e.g., damage to buildings and other infrastructure), a harvest management strategy was developed and implemented, and over 874,252 green iguanas were removed between October 2018 and August 2019. Distance sampling surveys were conducted to estimate abundance in February 2019 and annually in August 2014–2019. Abundance estimates were used to develop a Bayesian state-space logistic model, generate the posterior distributions of population and harvest management parameters, and make future predictions of abundance for August 2020–2030. Abundance increased over fivefold between August 2014 and 2018, from an average of 254,162 to 1,319,939 green iguanas. However, after harvesting for 5 months, abundance declined to an average of 600,113 green iguanas in February 2019; and after 11 months, abundance declined to an average of 103,020 green iguanas in August 2019. Maximum population growth rate averaged 1.552, carrying capacity averaged 1,611,013, equilibrium abundance averaged 805,506, maximum sustainable total harvest averaged 628,491, and maximum sustainable harvest rate averaged 0.776. With harvest rates between 0.600 and 0.800, predicted abundance averaged 28,751 green iguanas for August 2020–2030. However, harvest mortality may have unforeseen outcomes due to the release from density dependence and overcompensation through high survival and fecundity rates. Because natural resource managers have partial control over harvesting and incomplete understanding of green iguana population dynamics, monitoring and modeling are essential to assess population response and guide harvest management decisions.

Long‐Term Survival and Harvest of Resident Canada Geese in Virginia

ABSTRACTResident populations of Canada geese (Branta canadensis) are of particular management interest throughout the eastern United States given increased human‐wildlife conflicts due to regional increases in the Atlantic Flyway Resident Population. Within Virginia, USA, growth rates of resident goose populations have been reduced through extended harvest seasons and increased bag limits. Our objective was to investigate spatiotemporal patterns in survival rates and harvest rates of resident geese in Virginia over the past 25 years. We estimated annual survival, recovery, and harvest rates using mark‐recapture data from 1990–2015 for individuals that were banded as resident birds during summer throughout the state. We tested for differences in annual survival probability and harvest rates of resident geese banded and recovered in 3 distinct goose hunt zones: the Atlantic, Southern James Bay, and Western hunt zones, each of which had different hunting regulations. We also tested for differences in survival and harvest rates between individuals banded in rural or urban sampling locations, and between age classes (i.e., after hatch‐year or hatch‐year). In general, survival rates of resident geese over the past 25 years in Virginia are declining. Differences in survival among the 3 goose hunt zones also suggests that current harvest management strategies have reduced survival rates of resident geese. Upon closer examination, we found differences in survival among zones, with resident geese in the Atlantic and Southern James Bay hunt zones showing more negative declines compared to resident geese in the Western zone. Resident geese banded in rural areas had higher survival than urban‐banded geese. We also investigated the effects of sampling effort on survival estimates and found no difference in survival estimates among groups when using 75%, 50%, 25%, or 5% of the data randomly sampled from the full data set, suggesting that banding efforts of resident geese could be reduced and continue to inform adaptive management strategies for these populations throughout Virginia. © 2020 The Wildlife Society.

The Economic Impacts and Management of Spotted Wing Drosophila (Drosophila Suzukii): The Case of Wild Blueberries in Maine.

Drosophila suzukii (Matsumura), or spotted wing drosophila, has become a major pest concern for berry growers in the United States. In this study, we evaluated the economic impacts of D. suzukii on the Maine wild blueberry industry from two perspectives. The first analysis estimated the state-level economic impacts of D. suzukii on the wild blueberry industry in Maine in the absence of control. We found that D. suzukii could result in drastic revenue losses to the industry, which could be over $6.8 million under the worst-case scenario (assuming a 30% yield reduction). In the second analysis, we used Monte Carlo simulation to compare the expected revenues under different management strategies for a typical wild blueberry farm in Maine. The analysis focused on a decision-making week during the harvesting season, which the grower can choose in between three control strategies: no-control, early harvest, or insecticide application. The results suggested that insecticide applications are not economically optimal in most low infestation risk scenarios. Furthermore, although the early harvest strategy is one of the strategies to avoid D. suzukii infestations for wild blueberry production in Maine, the tradeoff is the revenue loss from the unripe crop. Using the simulation results, we summarized optimal harvest timing regarding the fruit maturity level under different D. suzukii infestation risk scenarios, which can minimize the revenue loss from adopting the early harvest management strategy.

Migratory Timing and Rates of Chinook Salmon Bound for the Kwethluk and Kisaralik Rivers

Abstract Detailed information regarding migratory behavior (i.e., phenology and rate of travel) of specific Pacific salmon Oncorhynchus spp. substocks can be used to design management strategies focused on protecting substocks from harvest when desired; however, this information is often lacking. The Kwethluk and Kisaralik rivers are two tributaries of the lower Kuskokwim River that originate and flow through the Yukon Delta National Wildlife Refuge in western Alaska. Although these two systems are the primary Chinook Salmon–producing tributaries within the Yukon Delta National Wildlife Refuge, little is known about migratory behavior of Chinook Salmon destined for these rivers. In 2015 and 2016, 119 Chinook Salmon tagged with radio telemetry transmitters entered either the Kwethluk or Kisaralik Rivers and were tracked throughout their migration to their assumed final spawning location using both ground- and aerial-based tracking methods. We compared migration timing and swim speeds between fish bound for these two rivers and between fish of different sizes and compared the consistency among the 2 y. In general, we found that fish bound for the Kwethluk and Kisaralik rivers exhibited similar migration behaviors in 2015 and 2016, including entry timing into the Kuskokwim River and migration rates once in the tributaries. A key finding was that Chinook Salmon swam fastest (range of means between years: 20–45 km/d) in the main-stem Kuskokwim River and slowed significantly (4–15 km/d) upon entry into lower portions of the tributaries. Our findings have relevance for harvest management strategies; for example, temporal fishery closures will impact Chinook Salmon bound for both the Kwethluk and Kisaralik rivers equally given their broad overlap in entry timing, and individuals will remain vulnerable to harvest for longer periods when located in tributaries rather than the portion of the main-stem directly below the tributary confluences.

Trophy Hunting and Possible Source-Sink Dynamics in Protected Areas: Insights from Trophy Size and Offtake Patterns in Southeast Zimbabwe

Developing harvest management strategies in designated hunting areas requires systematic and robust monitoring. We assessed the trophy size, quota utilization, and distribution of kill sites of African elephant, Cape buffalo, greater kudu, and leopard for the period 2007-2014 in Malapati Safari Area, southeast Zimbabwe. Trophy sizes for African elephant significantly increased over time albeit being below the expected minimum Safari Club International (SCI) score. Cape buffalo trophy sizes declined significantly over time but were not different from the SCI minimum score. However, greater kudu trophy sizes were higher than the SCI minimum score despite being constant over time. Leopard trophy sizes were higher than the SCI minimum score and increased with time. Quota utilization for African elephant and Cape buffalo increased while that of greater kudu and leopard did not change between 2007 and 2014. Some kill sites, in particular, for the African elephant and Cape buffalo, were within the buffer area with the state protected area, i.e., Gonarezhou National Park. Increased hunting pressure likely leads to poor trophy quality and hunting within the protected buffer areas. In contrast, effective adherence to hunting ethics and scientifically and conservatively set quotas largely does not compromise the trophy quality of harvested species. The observed trophy size patterns and kill sites distribution suggest the possible existence of source and sink dynamics of trophy species occurring in a protected area complex within the Zimbabwe’s component of the Greater Limpopo Transfrontier Park. To ensure sustainable trophy hunting in the study area and similar ecosystems the following are recommended: (i) scientifically robust, adaptable, and participatory quota setting process, (ii) enhanced adherence to good practice in terms of ethical hunting conduct, and (iii) development of a robust hunting monitoring system covering all elements of hunting for adaptive wildlife management.

Making do with less: must sparse data preclude informed harvest strategies for European waterbirds?

The demography of many European waterbirds is not well understood because most countries have conducted little monitoring and assessment, and coordination among countries on waterbird management has little precedent. Yet intergovernmental treaties now mandate the use of sustainable, adaptive harvest strategies, whose development is challenged by a paucity of demographic information. In this study, we explore how a combination of allometric relationships, fragmentary monitoring and research information, and expert judgment can be used to estimate the parameters of a theta-logistic population model, which in turn can be used in a Markov decision process to derive optimal harvesting strategies. We show how to account for considerable parametric uncertainty, as well as for different management objectives. We illustrate our methodology with a poorly understood population of Taiga Bean Geese (Anser fabalis fabalis), which is a popular game bird in Fennoscandia. Our results for Taiga Bean Geese suggest that they may have demographic rates similar to other, well-studied species of geese, and our model-based predictions of population size are consistent with the limited monitoring information available. Importantly, we found that by using a Markov decision process, a simple scalar population model may be sufficient to guide harvest management of this species, even if its demography is age structured. Finally, we demonstrated how two different management objectives can lead to very different optimal harvesting strategies, and how conflicting objectives may be traded off with each other. This approach will have broad application for European waterbirds by providing preliminary estimates of key demographic parameters, by providing insights into the monitoring and research activities needed to corroborate those estimates, and by producing harvest management strategies that are optimal with respect to the managers' objectives, options, and available demographic information.

Distance, environmental and substrate factors impacting recovery of bryophyte communities after harvesting

AbstractAimsBryophyte re‐colonization after disturbance is largely governed by environmental conditions within disturbed forests. In particular, distance to a forest edge is an important predictor of bryophyte community re‐colonization, through either direct constraints, such as dispersal limitation, or indirectly by altering environmental conditions. This study examines a range of factors – environmental, distance to an edge, substrate specific environment or local‐level environment – to determine which are important in the re‐colonization of bryophyte communities after forest harvesting. As bryophyte communities vary with the particular substrate inhabited, responses were examined across four substrates (rock, exposed roots, ground and CWD).LocationTasmanian southern forests, Australia.MethodsBryophyte composition was examined on four substrates (ground, coarse wood debris, exposed roots, rocks) within three ages (~7, ~27 and ~45 years post‐disturbance) of harvested wet eucalypt forest. Re‐colonization success of bryophyte communities was determined by comparing communities in regeneration forest to mature forest communities using axis scores from one‐dimensional constrained ordination. The importance of various environmental conditions for re‐colonization success was then modelled. Finally, path analysis was used to determine whether the impact of distance to a forest edge was meditated through its effects on key environmental variables.ResultsMultiple environmental factors impacted re‐colonization of mature bryophyte communities. Local‐level conditions such as microclimate (temperature, humidity and VPD) and LAI were the most important in determining re‐colonization across substrates. Path analysis showed that distance to a forest edge had a significant impact on re‐colonization success, but only a relatively small part of this was mediated through its impact on environmental factors.ConclusionsBryophyte re‐colonization is driven by a combination of microclimate conditions and factors related to distance from a forest edge (most likely dispersal distance). While some substrate‐specific factors impact bryophyte re‐colonization success, the consistent impact of local environmental factors across substrates suggests that harvesting management strategies that develop more ‘mature’ microclimate conditions and increase proximity to nearby mature forest patches will be beneficial for all bryophytes communities. As bryophyte re‐colonization was correlated with temporally dynamic environmental conditions, we suggest that forest age needs to be considered in future work.