Rate Of Population Increase Research Articles

Fitness‐related traits are maximized in recently introduced, slow‐growing populations of a global invasive clam

AbstractMany species are shifting their ranges and being forced to rapidly respond to novel stressful environmental conditions. Colonizing individuals experience strong selective forces that favor the expression of life history traits notably affecting dispersal and reproductive rates in newly invaded habitats. Limited information is currently available on trait variation within the invasive range despite being critical for understanding ecological and evolutionary factors that drive the process of range expansion of invasive species. Here we evaluated life history shifts in the widely introduced Asian clam Corbicula cf. C. fluminea within its invaded range. Through an exhaustive literature search, we obtained data for 17 invasive populations of this clam from different ecosystems worldwide. We tested the relationship between population and individual parameters relevant to the process of range expansion. Our main results are that recently introduced populations of clams were characterized by (a) low density and low rate of population increase, (b) earlier reproduction in slow‐growing populations of clams, and (c) no effect of density on population increase. All populations of the Asian clam analyzed in this study, which are fixed for one genotype (the lineage called Form A/R), experienced different selective environments in the introduced range. These findings support the perspective that adaptive phenotypic plasticity favored the expression of traits that maximize fitness in recently established populations, which faced stronger r‐selective forces relative to long‐established ones. We discuss the role of plasticity in facilitating rapid adaptation and in increasing the likelihood of populations to overcome difficulties associated with low densities and low population increase in newly invaded areas.

Effects of ancient allochthonous and contemporary autochthonous organic carbon on the growth and reproduction of lake zooplankton

Abstract Carbon with a radiocarbon age above 200 years before present (bp) generally is referred to as ancient carbon. Ancient organic carbon (OC) stored in glaciers, permafrost and unperturbed soil has been released with increasing temperatures resulting from climate warming and anthropogenic activities. Evidence suggests that ancient terrestrial OC can be incorporated by heterotrophic bacteria and consumers in many aquatic systems. However, it remains unknown whether ancient terrestrial OC promotes growth and reproduction of consumers. Ancient dissolved organic carbon (DOC) was extracted from frozen soils in the catchments of Lakes Tsochuolong (−216.9‰, 1,960 years bp) and Zhangnaitso (−384.1‰, 3,895 years bp) on the Tibetan Plateau, and was further degraded by heterotrophic bacteria. Degraded ancient DOC (containing bacteria) and Auxenochlorella (−161.6‰) were used exclusively or in combination as food (total 6 mg C/L) for Daphnia magna (D. magna) to compare their body length, mortality rate and offspring production. The mixed diets consisted of ancient DOC converted by bacteria at 4 mg C/L and Auxenochlorella at 2 mg C/L. The radiocarbon isotope (∆14C) value of D. magna fed on mixed diets was −293.0‰ for Lake Tsochuolong (group CA) and −265.9‰ for Lake Zhangnaitso (group CB), which was depleted than those fed exclusively on Auxenochlorella (−187.3‰, group 6C). This result suggests that 14C‐depleted DOC can be assimilated by zooplankton. Daphnia magna in group CB had the highest intrinsic rate of population increase (0.33/day) and number of neonates per individual (15.97/ind). The higher growth rate and offspring production in group CB than in CA (0.21/day and 7.68/ind) probably were because D. magna utilised more Auxenochlorella and phosphorus from diets in CB. However, there was no significant difference in the two indicators between CA and 6C (0.24/day and 12.30/ind) or between CB and 6C. Daphnia magna fed exclusively on degraded DOC plus bacteria had the lowest growth rate and offspring production. The results demonstrate that in the presence of algae with high nutritional value, degraded ancient DOC could support the growth and reproduction of zooplankton. Our findings extend the understanding of carbon sources and carbon cycling in food webs in lakes, particularly in high‐altitude and polar lakes in the context of climatic and environmental changes.

Does ancient permafrost-derived organic carbon affect lake zooplankton growth? An experimental study on Daphnia magna

The popular paradigm in trophic dynamic theory is that contemporary autochthonous organic matter (e.g., phytoplankton) sustains consumer growth, whereas aged allochthonous organic matter is conceptually considered recalcitrant resources that may only be used to support consumer respiration but suppress consumer growth. This resource-age paradigm has been challenged by a growing body of recent evidence that ancient (radiocarbon depleted) organic carbon (OC) released from glaciers and permafrost can be incorporated by consumers in aquatic systems. However, little information is available regarding the food quality of ancient terrestrial OC and how it impacts the growth of consumers in lakes. Here, ancient dissolved organic carbon (DOC) was extracted from frozen soils in an alpine lake catchment. The contents of polyunsaturated fatty acids (PUFAs) in soil DOC increased significantly after bioconversion by heterotrophic bacteria. The utilization of soil DOC by heterotrophic bacteria also increased the total phosphorus concentration in the systems. Gammaproteobacteria and Betaproteobacteria showed a strong negative correlation with the percentage contents of fluorescent components, including humic-like and tyrosine-like components. Daphnia magna were fed Auxenochlorella vulgaris and ancient DOC plus heterotrophic bacteria. The contents of PUFAs and the growth of zooplankton were influenced by the pre-conversion time of ancient DOC by bacteria. When ancient DOC was pre-converted by bacteria for 27 days, D. magna fed on the mixed diets showed the highest body length (3.40 mm) and intrinsic rate of increase in population (0.49 d−1). Our findings provide direct evidence that ancient terrestrial OC can be an important subsidy for lake secondary production, which have important implications for food webs in high-altitude and polar lakes.

Life tables of the ladybird beetles Harmonia axyridis, Cycloneda sanguinea and Hippodamia convergens reared on the greenbug Schizaphis graminum.

The Asian lady beetle Harmonia axyridis (Coleoptera: Coccinellidae) is a biological control agent that also may adversely impact other coccinellid species. Life table parameters were used to assess the population growth potential and the effects of interspecific competition between the invasive lady beetle H. axyridis and the native coccinellids Hippodamia convergens and Cycloneda sanguinea (Coleoptera: Coccinellidae) under laboratory conditions at 25 °C, using Schizaphis graminum (Hemiptera: Aphididae) as prey. The effects of the abiotic factors air temperature and humidity on these coccinellids by conducting a survey in a sorghum crop under average conditions of 18.1 °C and 53.5%, respectively, were also assessed. Fecundity was higher in C. sanguinea (1021.0 eggs per female) and H. axyridis (1029.2 eggs per female) than in H. convergens (484.5 eggs per female). The majority of the life table parameters showed no significant differences. The instantaneous rates of population increase (rm) of C. sanguinea, H. axyridis, and H. convergens were 0.195, 0.198, and 0.194 d-1, respectively. Based on the life table parameters obtained in this study, all three species of Coccinellidae showed a similar capacity to control a S. graminum population.

Significance of Autonomated Inspection for a Renewable Energy Production System

With the changing lifestyle of humans, the use of technologies increases, thus increasing the necessity of energy demand. Owing to limited nonrenewable energy sources, the demand for renewable energy is growing gradually. On the other hand, the waste generated increases with the increasing population rate. Wastes can be a useful source of energy demand, and environmental pollution can be reduced. This study explains a renewable energy production system. The proposed production system uses wastes as a source of raw material. Wastes are collected and transported from the collection center of a city to produce renewable energy. An autonomated inspection policy is used in the production system. The random rate of unusable wastes is scraped from the system, and the rest are sent for energy production. The total cost of the energy conversion plant is optimized analytically by a classical optimization method. Three numerical examples are given for uniform, triangular, and beta distribution of random scrap rate. The results show that adopting beta distribution for the proposed study is required to obtain the maximum amount of renewable energy at the minimum cost. The transportation cost is found as the most sensitive cost parameter among all cost parameters. The proposed study fulfills both the aims of renewable energy production and waste management.

Effects of Imunit Insecticide on Biological Characteristics and Life Table Parameters of Spodoptera cilium (Lepidoptera: Noctuidae).

Simple SummarySpodoptera cilium Guenee (Lepidoptera: Noctuidae) is one of the grass pests in some parts of the world, including the southern regions of Iran. The larvae of S. cilium feed on grasses and heavy infestations can severely destroy lawn grasses. In the present study, we monitored the effects of Imunit on some biological and demographic parameters of the offspring generation. Our results indicate that Imunit reduced the survival rate and fecundity of S. cilium and could be used in the management programs of this pest.Imunit is a mixture of alpha-cypermethrin + teflubenzuron, and has been launched for controlling caterpillars. In this study, the effects of Imunit at LC50 and LC30 were investigated on parental and offspring generation of S. cilium, according to age-stage, two-sex life table. The experiments were conducted by leaf dipping method at 25 °C and 60 ± 5% relative humidity, under a cycle of 16 h fluorescent light and 8 h darkness. LC30 and LC50 concentrations of Imunit increased the immature developmental time of S. cilium in the offspring generation, while the LC50 of Imunit significantly reduced the developmental time of adults. The adult pre-oviposition period and total pre-oviposition period considerably increased when offspring were treated with LC50 of Imunit. In offspring of S. cilium exposed to LC50 and LC30 concentrations of Imunit, the gross reproductive rate (GRR), net reproduction rate (R0), the intrinsic rate of population increase (r), and the finite rate of population increase (λ) significantly reduced compared to the control. This study showed that the application of Imunit at LC50 could suppress the S. cilium population and can be used in the integrated management program of this pest.

Fitness costs associated with chlorantraniliprole resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae) strains with different genetic backgrounds.

Spodoptera frugiperda (J.E. Smith) is a difficult pest to manage mainly because of its resistance to insecticides and Bt proteins. We evaluated fitness costs of S. frugiperda resistant strains to diamide insecticides with different genetic backgrounds aiming to highlight the importance of using isogenic strains. We established a near-isogenic strain of S. frugiperda resistant to diamides (Iso-RR), using a chlorantraniliprole resistant strain (RR) selected from a field-collected population and a susceptible reference strain (SS). Fitness costs were assayed using strains with close-related genetic backgrounds (Iso-RR and SS) and strains with distant-related genetic backgrounds (RR and SS). No fitness cost associated with chlorantraniliprole resistance in S. frugiperda was observed using the Iso-RR strain, based on life history traits. The only parameter that differs between Iso-RR and SS strains was the mean length of a generation (T), whereas the Iso-RR strain presented T=35.8 and SS strain showed T=34.6. On the other hand, a significant fitness cost was detected using the RR strain. All population growth parameters differ between RR and SS strains. Based on the intrinsic rate of population increase (rm ) parameter, the relative fitness estimated was 1.02 for the Iso-RR strain and 0.64 for the RR strain. The genetic background of the resistant strains alters fitness cost outcomes. The RR strain showed fitness costs associated with resistance, but the Iso-RR did not. Our work supports the decision-making process of resistance management programs and adds to the growing body of research that enlightens the importance of strain genetics in fitness cost experiments.

Intraspecific competition and persistence in Acanthoscelides macrophthalmus (Coleoptera: Chrysomelidae): an experimental analysis in a stage‐structured population

AbstractIntraspecific competition is an ecological process that can affect the structure of populations with important consequences for population persistence. In this study, we investigated (in the larval stage) the effect of intraspecific competition in the seed‐feeding beetle Acanthoscelides macrophthalmus on its population structure and persistence. By using Leslie matrices, which are useful to project future population sizes of structured populations, we conducted demographic analysis when competition was (more than one larva per seed) and was not (one larva per seed) present. The hypothesis that competition reduces the finite rate of population growth, the survival of the immatures and the fecundity of females, influencing population persistence, was tested. To understand whether intraspecific competition is a common process in this system, the oviposition pattern was also studied. We found that in the presence of competition, the larvae from the third instar were smaller than those in the absence of competition and, in the presence of competition, fewer larvae reached the adult stage. Larval survival was lower in the presence of competition, particularly from the third larval stage until the pupal stage, and the fecundity of females was also reduced in the presence of competition, which affected the population structure. Although we showed that populations may either grow geometrically or go extinct in absence and presence of competition, respectively, the finite rates of population increase did not differ from 1.0 when compared to the estimated confidence intervals. Therefore, although larval competition may affect the structure of this seed‐feeding beetle, there is no clear evidence that this ecological process can negatively affect its persistence. Furthermore, most seeds with eggs had just one egg per seed, which suggests that competition should occur with low frequency under natural conditions.

Lethal and sublethal toxicity of pesticides and vinasse used in sugarcane cultivation to Ceriodaphnia silvestrii (Crustacea: Cladocera).

With the growing use of agrochemicals in Brazil, there is also a growing need for more realistic toxicity assessments that aid in understanding the potential risks of environmental-realistic agrochemical (mixture) exposures in the natural ecosystems. The aim of the present study was therefore to evaluate the lethal and sublethal effects of environmental realistic (single and mixture) concentrations of the pesticides DMA® 806 BR (active ingredient - a.i. 2,4-D) and Regent® 800 WG (a.i. fipronil) and sugarcane vinasse to the Neotropical cladoceran Ceriodaphnia silvestrii. This evaluation was carried out through lethal (survival), sublethal (reproduction and intrinsic rates of population increase - r) and post-exposure (feeding rate and also reproduction) tests conducted in situ and with water from mesocosms contaminated with the recommended doses of these compounds. The results showed high acute toxicity for treatments containing fipronil and vinasse when acting in isolation, with survival rates only returning to control values on the last sampling day (75 days post application). Reproduction of surviving cladocerans was reduced in all treatments until the end of the experiment and were potentiated effect in the mixture of the three test compounds. The intrinsic rates of population increase were reduced in all treatments except the single 2,4-D treatment. Post-exposure feeding rate and reproduction, however, were not impaired under the conditions analyzed. The results show the high toxicity of recommended doses of fipronil and vinasse (and especially their mixture) and the importance of evaluating the risks of agrochemical mixtures at environmental-realistic concentrations.

A Study on Changes in Japanese Regional Industrial Structure Based on the Composition of Employees

Purpose: This study aims to analyze changes in the structure of local industries through changes in the number of employees by industry in Japan. This is to reason out the characteristics of the region through changes in the employment composition and labor productivity, noting that the region’s unique industrial structure is formed due to the natural environment and geographical conditions. Research design, data, and methodology: This study aims to characterize changes in the structure of local industries. The local economy varies in the pattern of changes in production structure depending on the type of production activity. To determine this, first, research design examines the situation of Japanese industrial structure. Second, the changes in local industries would be identified through changes in the composition of employees in each industry. Third, the relation with population changes that affect changes in industrial structure would be analyzed. Results: This study identified the characteristics of the local industrial structure by using variables such as employment composition, labor productivity, and population growth. As a result, first, the proportion of employed people in each industry was changing rapidly. Second, industrial structure change patterns appeared differently in areas of secondary industries and areas of tertiary industries. Third, there was a correlation between the rate of increase and decrease in population and employment. Each industry affected regional population changes in population inflow areas and population outflow areas in different ways, although the level of degree that regional population changes affects each industry was different. Implications: Industrial structure changes due to the various factors such as social structure. In particular, the composition of the local population by age plays an important role. This is because in the population inflow area, a virtuous cycle that attracts the new population is created by the ripple effect of the industry, but on the contrary, in the population outflow area, the decline of the industry quickly appears and it leads to a vicious cycle of the local economy.

Effects of Food Concentration and Photoperiod on Egg Production, Female Life Expectancy and Population Dynamics of the Paracalanid Copepod, Bestiolina amoyensis

The paracalanid copepod,Bestiolina amoyensis, is a widely distributed species occurring in subtropical inshore waters across the Pacific Ocean. Its small size, herbivorous feeding habit, and high adaptability make the species one of the most promising candidates as potential live feed for hatchery larval rearing. This study investigated effects of different feeding density of microalgaeIsochrysisspp. (1 × 105, 2 × 105, 3 × 105, 4 × 105, and 5 × 105cells ml–1) and photoperiod (8L:16D, 12L:12D, and 16L:8D) on productivity-related parameters, including egg production, female life expectancy and population dynamics ofB. amoyensis. Results showed that total egg output over female lifespan, final population size and intrinsic rate of population of 12L:12D photoperiod treatments were always the highest among three photoperiod conditions, especially at the food concentration of 4 × 105cells ml–1, indicatingB. amoyensishad high reproductive performance and the population was in a more stable status. The number of nauplii from 4 × 105cells ml–1algal concentration treatment accounted for 75% of the population, and the ratio of females to males approaching 1:1 when photoperiod was 12L:12D; female life expectancy was 10.5 ± 0.6 days. In conclusion, our results showed thatIsochrysisspp. is a suitable feed forB. amoyensiswith an optimal concentration at 4 × 105cells mL–1; the optimal photoperiod forB. amoyensisrearing is 12L:12D. The relatively long reproductive lifespan and high intrinsic population increase rate makeB. amoyensisa good candidate to develop culture techniques for hatchery larval rearing.

Introduction to the special edition on overabundant macropods

Introduction to the special edition on overabundant macropods

Effect of adult density on egg production, egg hatching success, adult mortality, nauplii cannibalism and population growth of the tropical calanoid copepod Acartia tropica

Present study evaluated the impacts of adult density on key biological parameters of a tropical estuarine calanoid copepod A. tropica. Egg production, egg hatching success (EHS), adult mortality (%), nauplii cannibalism (% hour−1), population growth and intrinsic rate of population increase in response to five different adult densities viz. 125, 250, 500, 1000 and 2000 adults/L were assessed. The highest individual egg production (IEP, eggs/female/day) was recorded at 125 adults/L treatment while relative egg production (REP, eggs/L/day) was highest at 1000 adults/L. EHS (24 h and 48 h) showed significant difference (p < 0.05) among the treatments with highest EHS recorded at 125 adults/L treatment and lowest EHS recorded at 2000 adults/L treatment. Moreover, the adult mortality and nauplii cannibalism were negatively correlated to adult density with significantly highest cumulative adult mortality (65 ± 3) and nauplii cannibalism (4.49 ± 0.27) recorded at 2000 adults/L. The highest population count after 8 days culture was recorded at 2000 adults/L treatment. However the lowest intrinsic rate of whole, live and adult population increase after 8 days culture was recorded at 2000 adults/L treatment. It is also observed that the population with an initial adult density of 2000/L decreases to a new stable equilibrium of 1000 adults/L after 8 days culture. Our results suggest to maintain A. tropica at a density of 1000 adults/L in batch culture with daily harvest of eggs and nauplii to maximise its productivity as live feed in aquaculture hatcheries.

Monitoring Spatiotemporal Environmental Changes in Dakahlia Governorate, Egypt Using Landsat Imagery

Dakahlia Governorate (Egypt) is considered an important area for plant diversity, facing three major problems, namely: high rate of population increase, limited renewable natural resources, limited production of food, forage, and raw materials for industrial purposes. Two multispectral Landsat imageries (TM and OLI 8) on 6th of March 1999 and 19th of March 2019 were calibrated and processed to produce LULC, different spectral indices (land surface temperature (LST), normalized difference vegetation index (NDVI), normalized difference Built-up Index (NDBI), normalized difference moisture index (NDMI), modified normalized difference of water index (MNDWI) and normalized difference salinity index (NDSI)). Furthermore, the surface temperature was obtained by processing the thermal bands of the Landsat image. Applying the indices on the raw digital numbers to produce a comparative study with the resulted values to detect the environmental change over the two last decades. According to the analysis, the results detected a loss in the vegetation areas and the bare land in favor of urban areas and water bodies to fulfill the requirements of the residents and the developers. That was confirmed with the analysis of the NDBI, NDSI, and LST that showed an increase as a result of urban sprawling. On the other hand, the NDVI explained that the uncontrolled urban sprawl caused the loss of agricultural lands. There was a slight expansion in the wild plant habitats, represented mainly by sparse class and partially by moderately dense class. Accordingly, this could be a result of the mutation in the habitats to favor the spreading of the moderate and sparse vegetation class, which MNDWI and NDMI confirmed.

Growth of Greater White‐Fronted Goose Goslings Relates to Population Dynamics at Multiple Scales

ABSTRACTThe abundance of greater white‐fronted geese (Anser albifrons frontalis) on the Arctic Coastal Plain (ACP) of northern Alaska, USA, has more than tripled since the late 1990s; however, recent rate of annual population growth has declined as population size increased, which may indicate white‐fronted geese on the ACP are approaching carrying capacity. We examined rates of gosling growth in greater white‐fronted geese at 3 sites on the ACP during 2012–2014 to assist with predictions of future population trends and assess evidence for density‐dependent constraints on recruitment. We marked goslings at hatch with individually coded webtags and conducted brood drives during early August to capture, measure, and weigh goslings. Annual estimates of gosling mass at 32 days old (range = 1,190–1,685) indicate that goslings had obtained &gt;60% of asymptotic size. This rate of growth corresponds with that of other goose species and populations with access to high‐quality forage and no limitations on forage availability, and is consistent with the overall increase in abundance of white‐fronted geese at the ACP scale. Contrary to most previous investigations, age‐adjusted mass of goslings did not decline with hatch date. Goslings grew faster in coastal areas than at inland freshwater sites. Taken together, these findings suggest forage was not limiting gosling growth rates in either ecosystem, but forage was of greater quality in coastal areas where goose foraging habitat is expanding because of permafrost subsidence. Spatial patterns of gosling growth corresponded with local‐scale patterns of population density and population change; the areas with greatest rates of gosling growth were those with the greatest population density and rates of population increase. We found little evidence to suggest forage during brood rearing was limiting population increase of white‐fronted geese on the ACP. Factors responsible for the apparent slowing of ACP‐wide population growth are likely those that occur in stages of the annual cycle outside of the breeding grounds. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Current Situation and Future Prospects for Plastic Waste in Maysan Governorate: Effects and Treatment During the COVID-19 Pandemic

Perils‏ ‏of plastic waste (PW) from polymers (ex: Polyethylene Terephthalate (PET), high-density polyethylene (HDPE), low-density ‎polyethylene (LDPE), polyvinyl chloride ‎‎(PVC), nylon, polystyrene (PS), etc.) ‎, the mechanism of its spread in ‎general and all of these types that are included ‎in our daily life system as a product expelled ‎continuously and/or frequently are 21st century crisis as reported from United Nations in 2019, and especially after the outbreak of the COVID-19 pandemic. PW is a very serious issue that has negative and harmful effects on the ecosystem, beside; health and the ‎economy through direct proportionality with the rate of increase in the state population, moreover, weak ‎environmental awareness and Energy International Administration (EIA) towards this dangerous issue. ‎ The aim of the current survey study is to shed light on the importance of plastics in our daily life needs for food packaging, single-use personal protective equipment's, laboratory tests, etc... PW problems by knowing the chemical composition, components, uses, and harms, as well as knowing the possibility of benefiting from these wastes within the solid waste management system (MSW / Municipal). By providing some suggestions that helps reduce the harm of this waste either recycling or disposal. This study will also include approximate theoretical equations to calculate the percentage of PW in particular at Maysan governorate, Iraq; because we haven't any physical mechanism at the operational level that deals with waste sorting, especially PW; as these statistics generally depend on the official information published by the competent authority about the total amount of waste presented at the governorate level.‎

Improving Outcomes for Patients with Age-Related Macular Degeneration and Cataracts: The Importance of Including an Assessment of Activities of Daily Life (ADL).

Age-related macular degeneration (AMD) is the leading cause of blindness in the developing world. AMD causes a substantial burden on patients, reducing independence, their ability to conduct daily activities, and increasing rates of cognitive decline and depression. There is a significant unmet need for patients with AMD, which will grow as the population ages and rates of disease increase. In the past, many studies have demonstrated a benefit when coexisting cataract formation is treated by removing the cloudy lens. AMD-lenses are intraocular implants designed to improve visual acuity in patients with AMD, avoiding the need for cumbersome manual vision aids and magnifiers. Many IOLs have been investigated in AMD, with differing mechanisms aimed at overcoming visual impairment. Most AMD studies use Early Treatment Diabetic Retinopathy Study (ETDRS) chart-based assessments of vision, but BCVA does not correlate with lesion size or pattern, especially in geographic atrophy, and may not be the most appropriate measure to effectively assess vision defects in AMD before or after a cataract surgery. One option is a simple functional assessment of vision related to activities of daily living (ADL), based on a reproducible, task-based questionnaire. The test consists of 6 assessments of ADL to be completed by patients before and after cataract surgery. Experiences highlight the importance of including an assessment of ADL in patients receiving an implant, which gives an effective measure of patient satisfaction. We would welcome the use of similar questionnaires in larger studies of patients, to validate its utility in a broader patient population. In this review article, we (Scandinavian-Austrian-cooperation) summarize lenses designed for implantation in patients with AMD, and how best to improve outcomes through proper patient selection, appropriate vision evaluation using quality-of-life related assessment, and pre- and post-operative care.

Projected lake sturgeon recovery in the Milwaukee River, Wisconsin, USA

Using a forward projecting population model, the timing and scale of Lake Sturgeon Acipenser fulvescens (LS) recovery and natural reproduction was estimated for the Milwaukee River in Wisconsin, USA for the years 2004–2048. LS, a widely distributed potamodromous Acipenseridae species in North America, have, like other sturgeon species, suffered population declines due to overharvest and other factors since the 1800s. LS recovery efforts were initiated in the early 1980s following the successful development of LS propagation techniques and stocking has become a widely utilized tool in LS recovery programs. Sturgeon recovery programs are long-term endeavors, with annual stocking usually planned for 25 plus years, along with population assessments and habitat improvements conducted over decades before project success can be verified. LS recovery activities on the Milwaukee River, a Lake Michigan tributary in southeast Wisconsin, began with barrier mitigation in 1997 and stocking in 2003. The modest size of the Milwaukee River, along with habitat improvements, and 17 years of stocking, provided an opportunity to model and predict LS population recovery trends. A forward projecting population model with an imbedded stochastic Ricker stock-recruitment relationship, adjusted for the estimated LS productive capacity of the Milwaukee River, estimated the timing and scale of LS recovery during 2004–2048 predicting a 18.3% annual average population rate of increase during the stocking period, and a 5.7% post-stocking rate. Accelerated LS growth and maturity due to goby consumption built into the model resulted in projections of gravid adult males present in 2012 and spawning adult females and natural recruitment in 2019. During the 2020 spawning period a group of adult-sized LS were observed in the Milwaukee River below an intermittent barrier on the river. The model predicted adult LS densities to grow from 22 in 2012 to 8088 in 2048, and annual natural recruitment to grow steadily from 76 yearlings in 2019 to an average of 4000 yearlings/year during 2039-2049. The estimated number of yearling recruits per spawning (gravid) female dropped steadily from 21 in 2019 to 8 recruits per gravid female in 2048 as a function of the Ricker stock-recruitment relationship built into the model. The model results indicate that significant LS recovery can possibly begin in a shorter time frame on Great Lakes tributaries than originally expected through systematic resolution of habitat issues and LS stocking. Results can also be used to help anticipate recovery trends, fine tune stocking and habitat strategies, and plan LS recovery assessments.

Management Implications for Skates and Rays Based on Analysis of Life History Parameters

The life history (age and growth and reproduction) parameters of 35 species (41 stocks) of skates and rays were analyzed using multivariate analyses. Three groups were categorized by cluster analysis (CA) based on principal component scores. Empirical equation was developed for each group to describe the relationships between the predicted a finite rate of population increase (λ′) and the life history parameters: growth coefficient (k), asymptotic length (L∞), age at maturity (Tm), annual fecundity (f/Rc), ratio between size at birth (Lb), and L∞ (Lb/L∞), and ratio between size at maturity (Lm) and L∞ (Lm/L∞). Group 1 included species with slow growth rates (k &amp;lt; 0.011 year–1), early maturity (Lm/L∞ &amp;lt; 0.62), and extended longevity (Tmax &amp;gt; 25 years); Group 2 included species with intermediate growth rates (0.080 year–1 &amp;lt; k &amp;lt; 0.190 year–1), intermediate longevity (17 years &amp;lt; Tmax &amp;lt; 35 years), and late maturity (Lm/L∞ &amp;gt; 0.60); Group 3 included species with a fast growth rate (k &amp;gt; 0.160 year–1), short longevity (Tmax &amp;lt; 23 years), and large size at birth (Lb/L∞ &amp;gt; 0.18). The λ′ values estimated by these empirical equations showed good agreement with those calculated using conventional demographic analysis, suggesting that this approach can be applied in the implementation of management measures for data-limited skates and rays in a precautionary manner.

On inferring population trends of mobile waterbirds from aerial transect surveys in variable environments

Monitoring waterbird populations in Australia is challenging for reasons of counting logistics, and because population aggregation and dispersion can shift rapidly in response to large spatio-temporal variations in resource availability. The East Australian Waterbird survey has conducted annual, aerial, systematic counts of waterbirds over eastern Australia for almost 40 years. It was designed to monitor waterbird populations using design-based inference though for many species this form of inference appears inadequate in the face of these challenges. Here we develop a state-space model-based Bayesian approach that, in addition to explicitly incorporating process noise and observation uncertainty, uses random effects and rainfall-derived covariates to model the year-to-year variation in the proportion of the total (super) population that is present on surveyed wetlands, and available to be counted. We use this model-based approach to estimate the superpopulation size of 45 waterbird species annually, and model the rate of population increase as a function of antecedent rainfall. The results confirm the strong positive effect of antecedent rainfall on population growth rates for nearly all species, and illustrate that species respond to rainfall differently in terms of habitat use, which influences whether they are present on surveyed wetlands. For many species, the year-to-year variation in the estimated proportion of the population on surveyed wetlands is very high. The results have implications for making inferences on population trends from these data, with the ability to model the year-to-year sampling variation a key requirement before the rate of population increase can be estimated with any precision. This study illustrates how to progress this approach, and infers that under average rainfall conditions, the general trend is for estimated superpopulation rates of increase to be negative, though for only a few species is this occurring with strong belief.