Minimum Abundance Research Articles

Diversity of Pentatomid Bug Fauna in Semi- Arid Western Rajasthan

The paper deals with the study of 15 species belonging to 13 genera under two subfamilies of family Pentatomidae in pearl millet and mungbean during kharif, 2022. 181 adults were identified into 15 species: Acrosternum gramineum, Adria parvula, Bagrada hilaris, Carbula biguttata, Carbula socia, Dolycoris indicus, Eysarcoris ventralis, Eysarcoris sp., Erthesina acuminata, Halys serrigera, Piezodorus hybneri, Placosternum taurus, Sciocoris indicus, Eocanthecona furcellata and Andrallus spinidens. The maximum relative abundance was observed for Eysarcoris ventralis (33.70%) followed by Piezodorus hybneri (20.99%). The minimum relative abundance was observed for Carbula biguttata, Carbula socia, Eysarcoris sp., Erthesina acuminata, and Placosternum taurus with the relative abundance of 0.55% each.

Spring resting egg production of the calanoid copepod, Eurytemora affinis, in a freshet-dominated estuary.

Seasonal peaks in river discharge, such as snowmelt-dominated freshets, are predictable events that can have a large effect on flushing rates and salinity in estuaries. Resting eggs, which many coastal and estuarine copepods produce for overwintering or aestivation, could also serve to bridge predictable peaks in river discharge. We assessed the timing of resting egg production of the egg-carrying estuarine copepod, Eurytemora affinis (Poppe), in relation to river discharge in the Fraser River Estuary, Canada. Approximately 30 field-collected females were individually incubated on 12 occasions over the period February 2015-May 2016. Eurytemora affinis abundance and population structure were investigated from vertical net tow samples collected twice monthly to monthly. Resting eggs occurred primarily in May 2015 and May 2016 (6.5 and 9.2 eggs day-1, respectively), a month prior to peak flows, and the proportion of offspring that were resting eggs increased with river discharge. Eurytemora affinis reached a minimum abundance in July 2015, when the population was dominated by adults (86%). Resting egg production in E. affinis is typically considered an overwintering mechanism but we suggest that the ultimate driver of resting egg production in this population is avoidance of flushing and/or low salinities.

Microbial dynamics and dehydrogenase activity in tomato (Lycopersicon esculentum Mill.) rhizospheres: Impacts on growth and soil health across different soil types

Abstract The dehydrogenase activity (DHA) in the rhizospheres of tomatoes grown in different soil types – Khor Abu-Habil (KA), Bara (B), and Greenhouse (Gr) – in North Kordofan, Sudan, was determined. In addition, the abundance of soil microbes in the tomato rhizospheres during the two growth stages, after 45 and 90 days (short and long term), was analyzed. The KA site (clay soil) showed the highest DHA (81.79 CFUs/g) followed by the B site (63.76 CFUs/g) (sandy loam) after 90 days of sowing, and the Gr site showed the lowest DHA (44.50 CFUs/g) (loamy sand soil) after 45 days. Moreover, the presence of high microbial activity (total density counts, total fungi, phosphate-solubilizing bacteria, Streptomycetes sp., Azotobacter sp., Azospirillum sp., and Pseudomonas sp. density counts) after 90 days and minimum microbial abundance after 45 days were identified at all sites. The measured growth parameters of fresh and dry weight, in addition to the root-to-shoot ratio, increased significantly at the same KA site dominated by a higher microbial density after 90 days. During the long term, the growth stage was positively affected by the abundance of adapted microbials that improve and enhance plant growth.

Zooplankton of Volga River reservoirs: structure, abundance and dynamics

The taxonomic structure and spatial distribution of the late-summer zooplankton in the Volga River from the upper Ivankovo reservoir to Volga Delta near Astrakhan during the period 2020–2021 were studied. Zooplankton biomass in the most of the Volga reservoirs was dominated by cladoceran Daphnia galeata and copepod Mesocyclops leuckarti (up to 45–84%). However different dominant species were observed in the Volgograd reservoir. Cladocerans Chydorus sphaericus and Bosmina cf. longispina formed there up to 43% of the total zooplankton biomass. Rotifers and Ponto-Caspian copepod Heteroscope caspian are dominated in the Volga River below the dam of the Volzhskaya hydropower plant (56% and 18% of the total zooplankton biomass respectively). Among the invasive species, most abundant are East Asian copepod Thermocyclops taihokuensis (up to 230 thsd. ind./m3 and locally 90% of the total biomass) and North American copepod Acanthocyclops americanus (up to 86 thsd. ind./m3 and 35% of the total biomass). The maximum abundance of the zooplankton (0.8–1.6 g/m3) was observed in the Upper Volga reservoirs while the minimum abundance (0.1–0.2 g/m3) – in the Lower Volga. The maximum abundance of zooplankton (0.8–3.3 g/m3) was recorded in the mouth areas of the reservoir tributaries, while the minimum abundance (0.1–1.4 g/m3) – in the pelagic zone of the reservoirs. A decrease in the zooplankton community biomass from Upper to Lower Volga was observed in all biotopes. A negative correlation between the community abundance and daily water inflow into the reservoirs and a positive correlation between the community abundance and water temperature were revealed. Long-term variations in zooplankton biomass and their relationship with water body trophic state, thermal and oxygen regimes were discussed.

Avian Diversity in and around Wetland of National Importance ‘Pariyej Community Reservoir’, Gujarat, India

The Pariyej Community Reservoir (PCR) is a freshwater reservoir in the Kheda district of Gujarat State, India. The PCR is also listed in Asian Directory of Wetlands. It is an important water storage reservoir; falls in the 4-B Gujarat Rajwara region of Central Gujarat, India. The present study was carried out for the period of one year (March, 2021 to February, 2022) to assess the status of avian diversity in terms of its species richness, abundance, and density. 116 bird species from 20 orders, 51 families, and 100 genera were documented. 75 species (64.4%) were resident, whereas 41 (35.3%) were migratory or seasonal. With respect to abundance, 41species (35.34%) were abundant, 39 species (33.6%) common, and 36 rare species (31.0%). The maximum total abundance (1707 individuals) was found at Site 1 in winter season with mean abundance of 427 individuals, total density (114 individuals/sq.km)and mean density (29 individuals/sq.km). The minimum total abundance (288 individuals) was recorded at Site2 in monsoon season with mean abundance of 72 individuals, total density (19individuals/sq.km) and mean density (5 individuals/sq.km).The present investigation reflects the good species richness of avian specieswith respect to order: family: genera: species ratioi.e., 1: 2.55: 5.0: 5.8. This indicates the flourishing harboring capability of PCR during peak winter period, which could be due to sustenance of rich biotic elements. The PCR has been declared as Sanctum sanctorumfor the refuge of migratory as well as local migrant birds, which is proved to be a wetland of national importance.

Vocal signatures affected by population identity and environmental sound levels.

Passive acoustic monitoring has improved our understanding of vocalizing organisms in remote habitats and during all weather conditions. Many vocally active species are highly mobile, and their populations overlap. However, distinct vocalizations allow the tracking and discrimination of individuals or populations. Using signature whistles, the individually distinct calls of bottlenose dolphins, we calculated a minimum abundance of individuals, characterized and compared signature whistles from five locations, and determined reoccurrences of individuals throughout the Mid-Atlantic Bight and Chesapeake Bay, USA. We identified 1,888 signature whistles in which the duration, number of extrema, start, end, and minimum frequencies of signature whistles varied significantly by site. All characteristics of signature whistles were deemed important for determining from which site the whistle originated and due to the distinct signature whistle characteristics and lack of spatial mixing of the dolphins detected at the Offshore site, we suspect that these dolphins are of a different population than those at the Coastal and Bay sites. Signature whistles were also found to be shorter when sound levels were higher. Using only the passively recorded vocalizations of this marine top predator, we obtained information about its population and how it is affected by ambient sound levels, which will increase as offshore wind energy is developed. In this rapidly developing area, these calls offer critical management insights for this protected species.

Optimizing backwash control using data on seasonal changes in the invertebrate community of granular activated carbon filters

Problems associated with the colonization and leakage of invertebrates in the granular activated carbon (GAC) filters of waterworks have received increased attention in recent years. To study the effect of environmental factors and water quality on invertebrate abundances, and the backwash control for minimizing invertebrate abundance. A survey of the invertebrate community of GAC filters was carried out monthly from March 2021 to May 2022. A pilot-scale GAC system established in the laboratory alongside a lake, with a volume of 35.3 L. 45 invertebrate species were detected, and 40 of these were rotifers. Significant variation in abundance was observed among seasons before and after GAC filtration, the average invertebrate abundance in the inlet water was 11.1 times that in the filtrate. The GAC filter contained invertebrates that might be responsible for the large number of organisms in the filtrate. Invertebrate abundance in the GAC filter decreased gradually with the carbon layer depth, which the mean invertebrate abundances were 6,926, 5,232, and 3818 ind./kg in the top layer (TL), middle layer (ML), and bottom layer (BL), respectively. Invertebrate abundance was correlated with water temperature and varied seasonally. Among eight water quality parameters, chlorophyll a (Chla) and the total plate count (TPC) were most significantly correlated with invertebrate abundance. According to the statistical modeling and the optimization process of response surface methodology (RSM). The predicted optimal values were a flow rate of 6.36 L/h, a backwash cycle of 3.26 d, and a backwash intensity of 14.97 L/(m2·s) for a minimum invertebrate abundance of 3013 ind./kg in the GAC filter. To maintain invertebrate abundance within an acceptable range, some of these measures might need to be modified depending on the actual conditions.

Impact of Physico-Chemical and Biological Parameters on Zooplankton Composition and Abundance in Freshwater Lake of Mulukanoor Karimnagar District, Telangana

The plankton constitutes the basic food sources of any aquatic ecosystem, which Supports fish and other aquatic animals. Zooplankton diversity is one of the most important ecological parameters in water quality assessment. Zooplankton is good indicator of the changes in water quality because they are strongly affected by environmental conditions and respond quickly to changes in water quality. In the present paper, Zooplankton diversity in relation to physico-chemical parameters of the Mulukanoor Lake located in Krimnagar District, Telangana state.The study was carried out for a period of one year from June 2015 to May 2016 to evaluate the relationship and influence between different water quality parameters and the abundance of zooplankton population. The physico-chemical parameters includes Temperature, Electrical Conductivity, Total Dissolved Solids, Water Transparency, PH, Dissolved Oxygen.Free Co2, Total Alkalinity, Total Hardness, Chloride, Biological Oxygen Demand, Phosphate, Nitrate and Ammonia were analyzed. All the values of these parameters were found within the prescribed standard limits. Therefore this lake has rich number of species biodiversity of aquatic animals. Four different groups of zooplankton were identified in this study which includes Rotifera, Cladocera, Copepoda and Ostracoda. Zooplankton diversity and abundance refers to variety within in the community. Numerically rotifers were dominant group throughout the study period. The season wise zooplankton analysis showed a maximum average abundance of species in Post-Monsoon season, minimum abundance in monsoon season due to the different environmental and inflow characteristics of the water body. The composition of zooplankton rotifers was dominant Rotifera(56%) followed by cladocera (23%), copepod (13%) and ostracoda (8%).Therefore it can be now concluded that this lake is highly potential to take up commercial fisheries.

Lotka-Volterra model with Allee effect: equilibria, coexistence and size scaling of maximum and minimum abundance.

The Lotka-Volterra competition model (LVCM) is a fundamental tool for ecology, widely used to represent complex communities. The Allee effect (AE) is a phenomenon in which there is a positive correlation between population density and fitness, at low population densities. However, the interplay between the LVCM and AE has been seldom analyzed in multispecies models. Here, we analyze the mathematical properties of the LVCM [Formula: see text] AE, investigating the coexistence of species interacting through neutral diffuse competition, their equilibria and stable points. Minimum viable population density arises as the threshold below which species go extinct, characteristic of strong Allee effects. Then, by imposing relationships of main parameters to body size, i.e. allometric scaling, we derive a general solution to the size-scaling maximum and minimum expected density under plausible scenarios. The scaling of maximum population density is consistent with the literature, but we also provide novel predictions on the scaling of the lower limit to population density, a critical value for conservation science. The resulting framework is general and yields results that increase our current understanding of how complex demographic processes can be linked to ubiquitous ecological patterns.

Quantifying old-growth forest of United States Forest Service public lands

Old-growth forests are globally valued for their ecological attributes, cultural significance, and in many cases their rarity. Yet, defining and quantifying these forests has been a difficult task. This study developed an approach to consistently estimate extent of old-growth forest on United States Department of Agriculture (USDA) Forest Service National Forest System (NFS) lands, using NFS regional old-growth definitions applied to the US national forest inventory (conducted by the USDA Forest Service Forest Inventory and Analysis [FIA] program). This method was developed in response to a presidential order (EO#14072, April 22, 2022) and federal laws (e.g., Infrastructure Investment and Jobs Act, 2021; Inflation Reduction Act, 2022). We worked with NFS experts to obtain regionally approved criteria for establishing old growth status based on NFS definitions, assessments, and related documents. NFS regional old growth definitions focus on structural characteristics of forests with criteria for old growth status commonly including minimum abundance of large live trees (in eight of nine regions), tree or stand age (in eight of nine regions), and dead large tree density (in three of nine regions). Determining the regional criteria to use was straightforward for some NFS regions where old-growth forest definitions were specific, and in some cases, had already been applied to FIA data to quantify old-growth forest area. In other NFS regions, such as where definitions have never been applied in an operational manner, or where there were merely assessments of remnant old-growth forest conditions, determining exact criteria was more difficult. We estimate that there are approximately 10 million ha of old growth across NFS forests, as defined by NFS criteria, with the preponderance in the western US states. This study produces the first old-growth forest assessment at the national scale based on NFS definitions and FIA’s statistically-rigorous national forest inventory of the US. These methods can be repeated with future inventories or modified when definitions change to produce updated estimates of old-growth forest attributes, and such work is already underway.

Inter-annual changes of zooplankton in the kultuk zone of the Volga River delta in the spring period

The studies conducted in spring have shown the main trends in changes in the structure of zooplankton in the kultuk zone of the Volga River delta in years that differ in hydrological and temperature regimes. It was revealed that in low-water years (2012, 2014), with a decrease in the volume of runoff, water level, and a reduction in the duration of floods, zooplankton was characterized by relatively low species richness, high biomass of Copepoda and Cladocera. At the same time, the highest rates of specific species richness, biomass and abundance of all zooplankton groups were observed at spring of a low-water year (2014), which was characterized by a runoff volume during the flood of 101 km3, a high pre-flood water levels, the absence of a sharp and significant dilution, as well as an early warm spring and gradual warming of the waters. In the year (2012), characterized by a volume of runoff during the flood period of 114 km3, a decrease in water level and a sharp increase in temperature before the flood, and then its rapid rise with dilution by cold waters, zooplankton was distinguished by the minimum species richness, a low number of ecological groups and low abundance of Cladocera, but a high proportion of juvenile copepods (fine filter feeders) and in terms of biomass of active euryphagous predators and euryphagous collectors. In a medium-water year (2013) with a large volume of runoff during the flood of 140 km3, with early and high and long floods, zooplankton was distinguished by a high total number of species encountered, but a minimum abundance and biomass, which is associated with the “dilution effect” and an increase in the areas of flooded rich in higher aquatic vegetation.

Diversity and functional annotation of microorganisms in anaerobic chamber treating nitrate-rich wastewater.

The vertical flow constructed wetlands (VFCW) for the treatment of domestic wastewater has become a conventional and cost effective treatment system with one of the major disadvantage of elevated nitrate concentrations. The present study makes an effort in providing a new design of anaerobic denitrification unit termed as anaerobic chamber (AC) whichwas introduced after two-stage VFCW to remove nitrates from the treated wastewater (WW). The AC provided all the essential conditions of effective denitrification such as anaerobic environment with enough carbon and nitrogen source. To understand the pollutant removal mechanism in AC, microbial diversity and functional annotation was studied by metagenomic analysis of sequences obtained from biofilm formed in AC. The efficiency of AC was measured with respect to physicochemical wastewater quality parameters. The removal efficiencies were 88, 65, 43 and 27% for total nitrogen, nitrate (NO3), ammoniacal-nitrogen (NH4) andortho-phosphate respectively. The microbial flora was much more diverse and unique pertaining to anaerobic microbes in AC compared to WW with total of 954 and 1191 genuses respectively with minimum abundance of 10 hits. The metagenomes exhibited 188% more Archaea in the AC than WW where Crenarchaeota, Euryarchaeota, Korarchaeota, Nanoarchaeota and Thaumarchaeota were major phyla with 60 genuses. The nitrogen metabolism was reported in terms of assimilatory nitrate reductase. As the class, Proteobacteria, Actinobacteria were prominent in WW, whereas Proteobacteria, Chloroflexi in AC were abundant. From functional annotation of sequences, the microbial flora in AC has the potential of removal of pollutants present in the form of carbon, nitrogen, and phosphorus.

SEASONAL TROPHIC NICHE BREADTH AND OVERLAP IN A GUILD OF SIX MOST FREQUENT BEE SPECIES IN BAHAWALPUR, PAKISTAN

Agonistic relationships in plant-pollinator assemblages are poorly understood as compared to mutualistic relationships. We estimated the floral resource competition in terms of seasonal trophic niche breadth and overlap among the guild of six most frequent bee species i.e., Ceratina smaragdula, Lasioglossum sp., Ceylalictus sp., Halictus sp., Apis dorsata and Apis florea in Bahawalpur (Punjab), Pakistan. The species exhibiting the maximum niche breadth had the minimum abundance in spring and summer seasons. The niche breadth of two solitary bees i.e., Lasioglossum sp. and C. smaragdula was higher than the social A. florae but they were much less abundant. Ceratina smaragdula showed the maximum pair-wise niche overlap with A. florea and Halictus sp. in spring and with Ceylalictus sp. in summer. Apis florea and A. dorsata had the maximum pair-wise niche overlap in both the autumn and winter seasons. No significant pair-wise niche overlap and interspecific competition was observed among all the six species in any season. This shows that pollination system in arid Bahawalpur is stable and less prone to competition and species loss.

Physico-chemical Parameters and Freshwater Fish Diversity of Sip River Madhya Pradesh, India

This study was carried out to analyze the variation in water quality and to investigate the current status of the fish fauna of the Sip river. Water samples and fish specimens were collected on monthly basis from six stations in the months of August 2017- July 2018. All the water quality attributes were found in the acceptable range that supports fish species, except stations IV and V, where pollution load was gradually increases. Seasonal changes in the physico-chemical parameters such as water temperature, pH, DO, free CO2 and total alkalinity revealed the effect on fish species diversity as well as health status of the river. The checklist of fish species recovered during the study was a total of 19 fish species belonging to 9 families, 13 genera and 4 orders. The family Cyprinidae dominant with 11 species, followed by Ambassidae 2 species, while as Bagridae, Channidae, Gobidae, Heteropneustidae, Nandidae and Siluridae each recorded 1 species, respectively. A total of 341 individuals of different fish species were caught from the different stations by using various fishing gears like cast net, gill net, hook and rod methods. Among all the stations studied, the maximum values of abundance 112 and 105 individuals was recorded from V and II stations, followed by I and VI stations having 57 and 51 individuals, while as minimum abundance 7 and 9 individuals was recorded from III and IV stations, respectively. Maximum values of Shannon-Weiner index (2.454) and Simpson’s index (0.906) were recorded from station-V (Pandagaon), while as minimum values of these indices (0.529 and 0.345) were recorded from stations-IV (Syampura). However, maximum values of Margalef’s index (2.793) and Pielou’s index (0.9898) were found from station-II (Ambhakadim) and station-III (Jiryna). The results of the study showed that the Sip river harbors rich ichthyofaunal diversity, but due to some anthropogenic pressure and illegal fishing practices adversely affected the fish diversity. The present study provide base line data initiative to update the current status of fish diversity and water quality parameters and will be useful to enhance the management and conservation strategies, for the fish species of Sip river. Therefore, important steps should be taken into consideration to increase the long-term sustainability of water health and fish activities in the river system

Prebiosignature Molecules Can Be Detected in Temperate Exoplanet Atmospheres with JWST

The search for biosignatures on exoplanets connects the fields of biology and biochemistry to astronomical observation, with the hope that we might detect evidence of active biological processes on worlds outside the solar system. Here we focus on a complementary aspect of exoplanet characterization connecting astronomy to prebiotic chemistry: the search for molecules associated with the origin of life, prebiosignatures. Prebiosignature surveys in planetary atmospheres offer the potential to both constrain the ubiquity of life in the galaxy and provide important tests of current prebiotic syntheses outside of the laboratory setting. Here, we quantify the minimum abundance of identified prebiosignature molecules that would be required for detection by transmission spectroscopy using JWST. We consider prebiosignatures on five classes of terrestrial planets: an ocean planet, a volcanic planet, a post-impact planet, a super-Earth, and an early-Earth analog. Using a novel modeling and detection test pipeline, with simulated JWST noise, we find the detection thresholds of hydrogen cyanide (), hydrogen sulfide (H2S), cyanoacetylene (HC3N), ammonia (NH3), methane (CH4), acetylene (C2H2), sulfur dioxide (SO2), nitric oxide (NO), formaldehyde (CH2O), and carbon monoxide (CO) in a variety of low-mean-molecular-weight (<5) atmospheres. We test the dependence of these detection thresholds on an M dwarf target star and the number of observed transits, finding that a modest number of transits (1–10) are required to detect prebiosignatures in numerous candidate planets, including TRAPPIST-1e with a high-mean-molecular-weight atmosphere. We find that the Near Infrared Spectrograph G395M/H instrument is best suited for detecting most prebiosignatures.

Seasonal Occurrence of Greater Banded Hornet (Vespa tropica Linn.) in Western Honey Bee (Apis mellifera Linn.) Colonies under Terai Agro-ecological Region of West Bengal

The present study was conducted during September, 2018 to August, 2020 on the seasonal incidence of Vespa tropica Linn. on Apis mellifera Linn. under terai agro-ecological region of West Bengal, India. Ten numbers of A. mellifera colonies of similar strength was placed in the apiary unit of Uttar Banga Krishi Viswavidyalaya, West Bengal, India in which no pest management strategies were carried out. Incidence of V. tropica was recorded higher during July to October peaking in the month of July (251.50±22.17 visits day-1) with annual average success rate of 57.23%±1.16%. From December to March little or no incidence was recorded. Minimum abundance of hornets was recorded at 07:00–09:00 hours. After that incidence started increasing with maximum incidence recorded at 13:00–15:00 hours i.e., 43.52±11.97 visits to the bee colonies day-1 during this time gap. Both maximum and minimum temperature and relative humidity showed significantly positive correlation with the incidence of V. tropica. However, rainfall was found to be detrimental for their incidence as it showed negative and non-significant correlation with their incidence. As V. tropica has been considered as a major enemy of honey bees, so the results obtained from the study can be used for designing integrated pest management strategies against this pest that will allow the beekeepers to focus on that particular time period when this pest is more abundant.

Observations of movement and site fidelity of white-beaked dolphins (Lagenorhynchus albirostris) in Icelandic coastal waters using photo-identification

The white-beaked dolphin (Lagenorhynchus albirostris) is the most commonly sighted delphinid species in Icelandic coastal waters. However, little is known about the species’ abundance, site fidelity and movements throughout its range. Photo-identification studies were conducted from April– October (2002–10) during whalewatching operations in Faxaflói and Skjálfandi bays on the southwest and northeast coasts of Iceland, respectively. Minimum abundance, annual site fidelity and movement between bays were calculated. A total of 154 and 52 individuals were identified in Faxaflói and Skjálfandi bays, respectively. The annual re-sighting rate was 21.4% in Faxaflói bay while only one individual was re-sighted in Skjálfandi bay (1.7%). A total of five dolphins (2.3%) were matched between Faxaflói and Skjálfandi bays with the period between re-sightings ranging from 272 to 821 days (mean 28.16 days, SD = 5.94). Low site fidelity rates observed likely signify a much larger home range than the present study area, into either other coastal or offshore zones, or alternatively may be explained by a large natural population size and/or the opportunistic nature of sampling during this study. Therefore, expansion of the study area is required. The matches between bays suggest that white-beaked dolphins inhabit a largescale coastal range of the Icelandic coast and can be considered highly mobile and transient possibly due to scarce and patchy resources. Alternatively it could be due to a large population size.

Review of contemporary cetacean stock assessment models

Model-based methods of analysis are widely used to conduct cetacean stock assessments, and to provide the operating models on which management strategy evaluation is based. This paper reviews recent assessments and management strategy evaluations for cetacean populations, with a view towards establishing ‘best practice’ guidelines for such analyses. The models on which these analyses are based range from simple exponential trend models that ignore density-dependence to complex multi-stock age-sex- and stage-structured models that form the basis for management strategy evaluation. Most analyses assume that density-dependence is on calf survival (which implicitly includes maturity and pregnancy rate), but it could also impact the survival rate of adults or the age-at-maturity. Cetaceans seldom have more than one calf per female each year, which limits the variation in calf numbers, and places an upper limit on the effects of density-dependent calf survival. The models differ in terms of whether the population projections start when substantial catches first occurred or whether allowance is made for time-varying carrying capacity by starting the model in a more recent year. Most of the models are deterministic, but account needs to be taken of variation in cohort strength for analyses that include age-composition data or for species that are relatively short-lived. A limited number of analyses include process variability using a statespace-like modelling framework. For some stocks, abundance is so low that ideally both demographic and environmental variability should be included in models. The primary source of data for parameter estimation is a time-series of estimates of absolute abundance, although some approaches considered used a variety of data types, including relative abundance indices, mark-recapture data and minimum abundance estimates based on haplotype counts. In general, at least one estimate of absolute abundance is needed for parameter estimation; this is because there is a lack of catch-induced declines in abundance captured by indices of relative abundance that could be used to provide information on absolute abundance. Similarly, information on abundance from age- and length- composition data is limited. Most of the analyses quantify uncertainty using Bayesian methods to allow information on biological parameters, particularly the intrinsic rate of growth and the relative population at which maximum production occurs, to be included in the analyses, along with sensitivity testing. The future for the models on which assessments and management strategy evaluations are based will often involve multi-stock models that include age-, sex- and spatial-structure and are fitted as state-space formulations, although at present such models are often too computationally intensive to be feasible for implementation or there is insufficient information in the data to estimate the parameters representing all the processes, leading to simplifications, with the result that the performance of some of the methods of assessment used for cetacean stocks needs to be better understood, including through simulation testing.

Evaluation of roost culling as a management strategy for reducing invasive rose-ringed parakeet (Psittacula krameri) populations

Rose-ringed parakeets (Psittacula krameri) are one of the most widespread invasive avian species worldwide. This species was introduced to the island of Kaua‘i, Hawai‘i, USA, in the 1960s. The rapidly increasing population has caused substantial economic losses in the agricultural and tourism industries. We evaluated the efficacy of a roost culling program conducted by an independent contractor from March 2020 to March 2021. We estimated island-wide minimum abundance was 10,512 parakeets in January 2020 and 7,372 in April 2021. Over 30 nights of culling at four roost sites, approximately 6,030 parakeets were removed via air rifles with 4,415 (73%) confirmed via carcasses retrieval. An estimated average of 45 parakeets were removed per hour of shooter effort. The proportion of adult females removed in 2020 was 1.9 × greater when culled outside of the estimated nesting season. Of the four roosts where culling occurred, the parakeets fully abandoned three and partially abandoned one site. Of the three fully abandoned roosts, an estimated average of 29.6% of birds were culled prior to roost abandonment. The roost culling effort was conducted during the COVID-19 pandemic, when tourist numbers and foot traffic were greatly reduced. It is unknown how public perception of roost culling in public areas may impact future efforts. Findings suggest roost culling can be utilized for management of nonnative rose-ringed parakeet populations when roost size is small enough and staff size large enough to cull entire roosts in no greater than two consecutive nights (e.g., if two shooters are available for three hours per night, roost culling should only be attempted on a roost with ≤ 540 rose-ringed parakeets).

Mollusc shell detritus affects benthic subtidal community dynamics in the Northern Wadden Sea

A shallow subtidal area in the northern Wadden Sea was monitored over 17 years (from 2003 to 2019) for sediment parameters and macrobenthic fauna. Due to the sheltered position of the study area, sediment composition remained rather stable with only minor annual and seasonal variations in sediment granulometry. An intermittend storm (‘Kyrill’) had no significant effect on sediment composition parameters; the construction of an artificial dune along the southern border of the study area had minor transient but no lasting effects on sediment composition. Faunal species richness and total abundance showed the typical seasonality with minimum abundance in late winter and a peak after recruitment in summer. Variations between years in autumn (post-recruitment) abundances were best explained by the number of days with a seawater temperature <1°C during the preceding winter. Temperature during other seasons, salinity, chlorophyll concentration and NAO showed no significant correlations with total abundance, nor did storm (‘Kyrill’) or construction of the artificial dune. Within-site faunal variability was best explained by water depth and velocity of the tidal currents while sediment granulometry was of minor importance. However, the amount of bivalve shell detritus mixed with the sandy sediment proved to be the strongest covariant of species numbers, total abundance, and species-specific abundances. At the sediment surface, shells provide the only anchorage for epibenthic species which in turn attract associated fauna. Shells inside the sediment hamper movement of infaunal predators and epibenthic predators are handicapped in rooting about for prey. Thus, shell material is a highly significant structural factor for the macrozoobenthos in these shallow waters. In a future with increasing ocean acidification, the availability of benthos as a food source for higher trophic levels will depend on the balance between pH-driven shell destruction and the compensatory power of shell-building species.