Wintering shorebird in sandy coasts of Catania’s gulf (Sicily, Italy): 2011-2020

Sandy coasts are specific habitats of high ecological significance for many species of shorebirds. The Gulf of Catania, in the Eastern coast of Sicily, is considered one of the most important sandy coastal areas of the region for the wintering of different species of Charadriidae and Scolopacidae, also due to the presence of River Simeto’s mouth and other freshwater streams. Since the area has been subject to many changes in the last few decades and recent data were not available, a ten-year monitoring of the wintering shorebird community has been carried out, from January 2011 to January 2020, to understand its current ecological role and to update the knowledge about numbers and trends of Sicilian wintering shorebirds along the coast. A total of 3,171 individuals and 16 different species were observed, including a considerable amount of individuals of Calidris alba and Charadrius alexandrinus, despite the latter showed an 80% decrease in number in the last 20 years in the area. For each species, maximum numbers observed per winter and related five-year averages, estimates, IKA (Index of Abundance per Kilometre) and percentages in relation to the national wintering population have been reported. Furthermore, data about species associations were collected and analysed. This survey shows how the ecological value of River Simeto’s mouth has decreased considerably in the last decades in favour of other locations, such as the mouth of Canale Arci, where almost 50% of the birds were observed.

Abundance and community structure of birds breeding in Kalahari woodland used as rangeland

The line transect method was applied to assess the linear index of abundance and community structure of birds breeding in an area of Kalahari woodland used as range land for cattle. Four transects were designed along roads traversing the ranch. Each transect was 2.5 km long and was surveyed three times in 2014 and 2015. A total of 47 bird species were recorded but only 25-31 species were recorded on any particular transect. In the neighbouring pristine Kalahari woodland, the number of bird species on a12 km long transect was much higher (n = 88), and ranged in some sections (each 1.2 km in length) from 35 to 53. On any particular section, the number of dominant species ranged from 5 to 7, and their cumulative dominance on each section was similar, ranging from 53-56 %, while the community dominance index ranged from 0.23 to 0.35. The most numerous species were the Cape turtle dove and emerald-spotted wood dove, which were dominant on all sections. Together they comprised 28 % of all breeding birds. The avian community in the Kalahari woodland in Sachinga LDC did not differ from the neighbouring pristine woodland either in terms of species diversity or evenness. However, it differed significantly in terms of species richness, the proportion of main ecological guilds, and linear index of abundance of particular species. These differences could be mainly due to the structure of woody vegetation, which is much thicker in Sachinga than in the pristine woodland not used as pasture for cattle. The thickening of this vegetation on the ranch could have been caused by heavy grazing pressure by the cattle. Data published through GBIF (Doi: https://doi.org/10.15470/rova7r)

CANIDAE CESTODES IN THE NATURAL TERRITORIES OF THE CENTRAL BLACK SOIL

Predators (Carnivora) have a large and diverse fauna of helminths, including higher cestodes (Cyclophyllidea). Among predators, the most representative group are canids (Canidae), which are of great importance in the circulation of these cestodes. Under the natural conditions of the Central Black Soil Region (Voronezh Reserve and adjacent territories), studies have been carried out to study the fauna and ecology of canine cestodes. According to the results of these studies, 10 species of higher cestodes were recorded in wild and domestic carnivores: Taenia hydatigena, T. pisiformis, T. crassiceps, T. krabbei, Hydatigera taeniaformis, Tetratirotaenia polyacantha, Mesocestoides lineatus, Dypilidium caninum, Echinococcus granulosus, E. multilocularis. The maximum number of cestode species was found in the fox – 9 species. Significantly less in other species of predators: in the wolf – 3 species, in the raccoon dog – 2 species, domestic dog – 2 species. The fox plays a leading role in the formation of the fauna of canine cestodes. Taenia (T. hydatigena and T. crassiceps) dominate in the composition of the cestodes fauna, they have the prevalence of infection and index of abundance, as well as M. lineatus. The fox has an actual zoonotic species E. multilocularis.

Estimating bobcat (Lynx rufus) abundance in Wisconsin during 1981-2015

Quantifying and estimating trends in wildlife abundance is critical for their management and conservation. Harvest-based indices are often used as a surrogate index for wildlife population. Sex-Age-Kill (SAK) models generally use the age-at-harvest of males and females, combined with annual mortality and reproduction rates to calculate a preharvest population estimate. We used and SAK model to estimate abundance for bobcats from 1981-2015. Pre-hunt population size ranged from approximately 1630-2148 during 1981-1995 after which the population increased to a maximum of 4439 in 2005 before declining to 2598 in 2013. Pre-hunt population size was highly correlated an index of abundance from winter track counts (r = 0.93). We found that the model, as currently implemented by WNDR, appears to provide an accurate trend of statewide bobcat abundance. SAK models more logistically feasible for long-term evaluations of population trends overbroad spatial extents than more intensive methods. While SAK models may be the only technique available to wildlife managers for estimating the abundance of harvested species, we encourage additional research to evaluate the effects of potential biases on estimates of abundance.

Preliminary data on density and habitat of carnivores in two protected areas of Burkina Faso (West Africa)

Apparent density [determined as kilometric index of abundance (KIA), by direct sightings and by droppings along line transects] and habitat use of some species of carnivore mammals were studied in two protected areas of Burkina Faso (Comoé-Leraba and Nazinga). Despite the fact that the dataset was collected throughout several years and with a very high field effort, the amount of data collected was relatively small, and confined just to a few species. There was no effect of the year on the average KIA estimates of the carnivores at this study area, and data from direct sightings along transects estimated lower densities than those coming from droppings collected along the same transects. In terms of habitat type, shrub savannah represented the best habitat type for carnivores, despite being relatively scarcely available along the line transects when compared with woody savannah (especially for Canis adustus and Civettictis civetta).

Hierarchical model detects decadal changes in calibration relationships of single-pass electrofishing indices of abundance of Atlantic salmon in two large Canadian catchments

Electrofishing is a commonly used technique to assess freshwater fish population abundance, and in many programs, there has been a shift in the sampling methodologies towards less laborious techniques. These new techniques usually only provide an index of abundance and require calibration with other sampling methods such as successive removal to be used for absolute abundance estimation. Using data for juvenile Atlantic salmon (Salmo salar) collected in 400 sites sampled over 21 years in two large Canadian river catchments with a single sampling protocol, we developed a hierarchical Bayesian model to account for effort, day of sampling, area of the site, and catchment effects on the relationship between the single-pass index of abundance and the fish densities, thereby illustrating the importance of carrying out a calibration exercise on a regular basis. Our work indicates that calibration relationships can change over time even with standardized sampling protocols and that these directional changes in important components of the sampling procedure can bias the estimate of population abundance and misinform the understanding of population dynamics.

Can a bottom-moored echo sounder array provide a survey-comparable index of abundance?

A small number of stationary echo sounders have the potential to produce abundance indices where fish repeatedly occupy localized areas (e.g., spawning grounds). To investigate this possibility, we deployed three trawl-resistant moorings with a newly designed autonomous echo sounder for ∼85 days during the walleye pollock (Gadus chalcogrammus) spawning season in Shelikof Strait, Alaska. Backscatter observed from the moorings was highly correlated with ship-based acoustic surveys, suggesting that the mooring observations reflect abundance over much larger areas than the observation volume of the acoustic beam. A retrospective analysis of a 19-year time series of prespawning walleye pollock surveys was used to select mooring locations and determine that three to five moorings can produce an index of walleye pollock backscatter comparable to that produced by a ship-based survey covering ∼18 000 km2 (mean prediction error of <11% for five moorings). The three moorings deployed in Shelikof Strait yielded a backscatter estimate that was within ∼15%–20% of that observed during the survey. Thus, it appears feasible to design a relatively sparse mooring array to provide abundance information and other aspects of fish behavior in this environment.

Combining data from bottom-trawl and acoustic-trawl surveys to estimate an index of abundance for semipelagic species

Fishery-independent surveys are useful for estimating abundance of fish populations and their spatial distribution. It is necessary in the case of semipelagic species to perform acoustic-trawl (AT) and bottom-trawl (BT) surveys to ensure that sampling encompasses both midwater and demersal components of the population. Abundance estimates from both survey types are negatively biased because of the blind zones associated with fish vertical distribution. These biases can vary spatially and temporally, resulting in confounded trends and additional variation in abundance estimates. To improve abundance estimates for semipelagic species we propose a new method for combining BT and AT survey data using environmental variables to predict the vertical overlap. Using walleye pollock (Gadus chalcogrammus) AT and BT surveys in the eastern Bering Sea as an example, we show that combined estimates provide more reliable whole water column and spatial distribution estimates than either survey can by itself. Although the combined estimates are still relative, they account for the uncertainty in the bias ratio between the two survey methods and the uncertainty associated with the extent of the water column sampled by both surveys. Our method of combining BT and AT data can be extended to other semipelagic species.

How do marine closures affect the analysis of catch and effort data?

Fishery managers increasingly use marine closures as a tool to conserve ecosystems, biodiversity, and fish abundance. Despite the suggested benefits of closed areas, the limited or no data collection within them leads to difficulties assessing the population status. We investigated how spatial closures impacted the reliability of indices of abundance obtained from standardization methods applied to catch per unit effort data. The presence of closed areas generally introduced a bias in the derived index of abundance, and the magnitude of bias increased as the portion of the population in closed areas increased. In general, restricting the data to the areas that have been continuously fished over time performed best when spatial closures protected a small to medium portion of the population. However, as the portion of the population that was protected increased, the time series bias associated with this approach increased, and the use of an imputation approach was needed for adequate performance. Similarly, the collection of ancillary data in the closed area reduced bias in the estimate of final year depletion when area closures protected a large portion of the population.