Highly oxygenated organic molecule cluster decomposition in atmospheric pressure interface time-of-flight mass spectrometers

Identification of atmospheric molecular clusters and measurement of their concentrations by atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometers may be affected by systematic error due to possible decomposition of clusters inside the instrument. Here, we perform numerical simulations of decomposition in an APi-TOF mass spectrometers and formation in the atmosphere of a set of clusters which involve a representative kind of highly oxygenated organic molecule (HOM), with the molecular formula C10H16O8. This elemental composition corresponds to one of the most common mass peaks observed in experiments on ozone-initiated autoxidation of alpha-pinene. Our results show that decomposition is highly unlikely for the considered clusters, provided their bonding energy is large enough to allow formation in the atmosphere in the first place.Peer reviewe

Highly Variable Autumn Calling Rates of Northern Bobwhite Following Translocation

Fall covey counts are a popular index for monitoring population trends of northern bobwhite (Colinus virginianus; hereafter, bobwhite), but their utility is tenuous under different scenarios. Detecting an individual covey is the product of the probability that the covey’s activity center is located within the sampling frame, the probability the covey is located within the sampling frame during the sampling periods, the probability of the covey vocalizing, and the probability an observer will detect a calling covey. Researchers attempt to maximize detection or account for these potential sources of error using standardized protocol of limiting counts to certain weather conditions, replication, and distance sampling. Variation in calling rates across a range of bobwhite densities could lead to tenuous inference of population abundance from fall covey counts, particularly at low densities. Our objectives were to assess fall calling rates at 2 sites with low bobwhite density during population restoration. Our study sites were located in Erath County, Texas, USA and Leon County, Florida, USA and received translocated bobwhite during 2019 and 2020. We hypothesized calling rates would be influenced by the number of adjacent coveys that called, and thus, would be low for our sites. Although we did not estimate bobwhite density on our study sites, we surmised that their respective populations were /3 ha. Calling rate at the Erath County site was 0 in 2019 (n = 10 counts) and increased to 0.79 (standard error [SE] = 0.07, n = 34 counts) in 2020. Calling rate was assessed only in 2020 at the Leon County site and averaged 0.13 (SE = 0.07, n = 23 counts). Detection rate at count stations was 0 in 2019 and 0.78 (SE = 0.08, n = 27 calling coveys) in 2020 at the Erath County site. In 2020, detection rate at count stations was 0 (n = 3 calling coveys) at the Leon County site. We documented high annual variation in calling rates among low-abundance sites, suggesting researchers should seek to empirically estimate this parameter rather than applying arbitrary correction factors based on previous literature. Low and variable calling rates limit detection and can bias inference

Location and timing of the deposition of egg strands by perch ( Perca fluviatilis

The reproduction biology of perch Perca fluviatilis was studied in relation to lake hydrology, spawning substrate and female size using SCUBA divers during late April and mid-May 2009 in Chabařovice Lake, Czech Republic. An extreme displacement of water mass, induced by a long-lasting strong wind, caused the abundance of egg strands to differ significantly between individual parts of the lake. On average, 91% of perch spawning activity occurred at depths greater than 3 m. The mean concentration of dissolved organic carbon (DOC) indicated that the lake belongs to the category where DOC influencing the penetration of ultraviolet radiation, is not responsible for the deep deposition of egg strands by perch. Most probably, the avoidance of shallow depths (<3 m) results from strong wind/waves coming from any direction. Larger perch females started to spawn earlier than their smaller conspecifics and they used shallower depths for depositing their egg strands. As a spawning substrate, perch strongly selected dead submerged vegetation, such as common reed Phragmites communis and worm weed Artemisia sp. These substrates, however, reveal signs of progressive degradation and seem likely to disappear from the lake within several years

Improved trawling setup for sampling pelagic juvenile fish communities in small inland bodies of water

Trawling juveniles is an effective method to estimate 0+ fish assemblages in inland bodies of water. Trawlers are usually moved between bodies of water by ground transport, which restricts the size, weight and type of the equipment able to be transported, and as such do not always come equipped with machinery for trawl operation. Having to lift the trawl onto the deck of the trawler after each tow also makes small-scale juvenile trawling time-consuming and personnel intensive and deep water trawling is especially hard work. This study introduces a new two-boat setup for continuous trawling that enables faster and easier operation of the trawl, even in deep water layers, and more accurate distance and depth measurements

Extremely shallow spawning of perch ( Perca fluviatilis

The roles of wind protected bays, presence of littoral vegetation and light attenuation in the water column on spawning site selection and depth of egg strands deposition by perch Perca fluviatilis was studied in Římov Reservoir, Czech Republic, in the years 2007 and 2011 using boat observation and SCUBA divers. The data were compared with results from Chabařovice Lake, Czech Republic, where similar monitoring took place in 2007–2010 and 2012. In shallow water of Římov Reservoir, the density of egg strands was significantly higher in grass bays compared to both rocky bays and the main reservoir body. Most egg strands were deposited in water less than 0.5 m deep on reed canarygrass Phalaris arudinacea. In year when the littoral vegetation was absent perch were forced to spawn significantly deeper on various types of woody structures. In Římov Reservoir, which is less vulnerable to wind, 91.1% of egg strands were spawned in water ≤3 m deep. In contrast, in the wind exposed Chabařovice Lake, even in the presence of littoral vegetation, 90.5% of egg strands were found at depths greater than 3 m. In Chabařovice Lake, the light penetrated to three times greater depth compared to Římov Reservoir and, similarly, the depth limit to which 95% of egg strands were spawned was three times greater in this lake compared to Římov Reservoir. This study is the first contribution showing the role of water transparency in controlling the depth distribution of perch egg strands in lakes and reservoirs

Extremely shallow spawning of perch (Perca fluviatilis L.) : the roles of sheltered bays, dense semi-terrestrial vegetation and low visibility in deeper water

The roles of wind protected bays, presence of littoral vegetation and light attenuation in the water column on spawning site selection and depth of egg strands deposition by perch Perca fluviatilis was studied in Římov Reservoir, Czech Republic, in the years 2007 and 2011 using boat observation and SCUBA divers. The data were compared with results from Chabařovice Lake, Czech Republic, where similar monitoring took place in 2007–2010 and 2012. In shallow water of Římov Reservoir, the density of egg strands was significantly higher in grass bays compared to both rocky bays and the main reservoir body. Most egg strands were deposited in water less than 0.5 m deep on reed canarygrass Phalaris arudinacea. In year when the littoral vegetation was absent perch were forced to spawn significantly deeper on various types of woody structures. In Římov Reservoir, which is less vulnerable to wind, 91.1% of egg strands were spawned in water ≤3 m deep. In contrast, in the wind exposed Chabařovice Lake, even in the presence of littoral vegetation, 90.5% of egg strands were found at depths greater than 3 m. In Chabařovice Lake, the light penetrated to three times greater depth compared to Římov Reservoir and, similarly, the depth limit to which 95% of egg strands were spawned was three times greater in this lake compared to Římov Reservoir. This study is the first contribution showing the role of water transparency in controlling the depth distribution of perch egg strands in lakes and reservoirs

Changes in the fish community of Loch Leven: untangling anthropogenic pressures

Loch Leven, U.K., contains brown trout (Salmo trutta), eel (Anguilla anguilla), minnow (Phoxinus phoxinus), perch (Perca fluviatilis), pike (Esox lucius) and three-spined stickleback (Gasterosteus aculeatus), with brook lamprey (Lampetra planeri) and stone loach (Barbatula barbatula) also present in its tributaries. Arctic charr (Salvelinus alpinus), Atlantic salmon (Salmo salar) and flounder (Platichthys flesus) are now extinct. The brown trout population has supported a world-renowned recreational fishery for over a century, although a decline in fishery performance led to extensive stocking between 1983 and 2006, including with non-native rainbow trout (Oncorhynchus mykiss). This review combines historical information with contemporary gill-net and hydroacoustic surveys. In 2008, brown trout, perch and three-spined sticklebacks were abundant, but pike and stone loach were rare. The obstruction of migratory routes was probably responsible for the loss of Atlantic salmon and flounder, while a lowering of water level likely caused the extinction of Arctic charr and contributed to a reduction in pike abundance. Perch abundance has fluctuated markedly, being influenced by disease and eutrophication, although a reduction in nutrients and associated recovery of macrophytes are likely to have benefitted this species. Although the brown trout population has undoubtedly shown a long-term decline, individuals are currently in excellent condition