Tracking Tiny Turtles—Movement, Survival, and Habitat Use of Hatchling Western Saw‐Shelled Turtles (Myuchelys bellii) During Their First Two Weeks in the Wild

The article reports the results of the study on the annual dynamics of fish density, taxonomic composition of the fish population in a section of a riverbed depression in the lower reaches of the Irtysh River. A complex system of interaction between environmental factors and fish relationships in the predator-prey system in the studied section of the river under changing environmental factors is considered. The study was conducted using echometric sounding of the water column of the riverbed depression with an acoustic complex; during the open water period it was performed from a boat and during the ice cover period — from a snowmobile. The study also analysed the dynamics of environmental factors (turbidity, temperature, water level) and their effect on fish density. The maximum fish density in the riverbed depression was observed in summer, when juveniles migrate from the floodplain to the main channel. Fish density differed significantly during periods of open water and ice cover. Groups of cyprinids and percids had the largest share in the fish population. Their joint share varied from 68.53 to 87.42% of the total fish density; these values were noted in January and August, respectively. The maximum fish density was noted in June, the minimum density — in October and December: 4.49, 1.19 and 1.45 thousand ind./ha, respectively. The dynamics of the total fish density in the water area of the riverbed depression is described by a polynomial regression equation, and the only influencing factor is water temperature. The dynamics of the density of taxonomic groups in the water area of the riverbed depression demonstrated the following characteristic features: for the density of cyprinids the influencing factors were temperature and the water level; for percids, coregonids and pikes — the density of cyprinids, cyprinids and percids, respectively; for burbots and sturgeons — the water level. The study revealed that turbidity has high reliable correlation with the water level and temperature.

Well water levels can reflect the stress placed on a confined subsurface aquifer system in a similar manner to a strain meter. Based on observations of the geophysical field in Lhasa combined with digital data recorded at an underground fluid well at the Lhasa geomagnetic station in recent years, we comprehensively analyzed the characteristics of co-seismic changes caused by 14 different-magnitude M ≥ 5 earthquakes recorded in the well. The results show that (1) the co-seismic changes in water temperature and water level are different; the water level exhibits oscillation-type changes, while the water temperature variations indicate first heating and subsequent recovery. (2) The co-seismic changes are related to the epicentral distance, magnitude and focal depth of the earthquake. The closer the epicenter is to the well, the earlier the co-seismic responses occur, but the time interval between the co-seismic changes in the water level and temperature differs. (3) The co-seismic ratio of the water temperature is higher than that of the water level; this may be related to faulty water level instrumentation or segmented records.

This experiment was carried out to confirm the role of water level and water temperature in inducing the spawning of tropical walking catfish. Mature males and females reared under 23 - 25 °C, were paired and induced to spawn by controlling water level and water temperature. Decreasing water level and returning it to its original level resulted in a low spawning rate (less than 6.7 %) at 23 °C. Decreasing water level with simultaneous increase in water temperature, followed by returning the respective levels to their originals gave high spawning rates (41.7 — 50 %); whereas the same treatment but without any water temperature decreased when the water level was returned to the initial level, gave a low spawning rate (16.7 %). Increasing water level only, failed to induce spawning. A high spawning rate was obtained also when changes in water level were carried out under high temperature of 28 °C. No fish spawned in the absence of the environmental stimulation. From the results, it is confirmed that water level and temperature play important roles in inducing spawning of tropical walking catfish. Changes in water temperature probably increase the sensitivity of fish to the change in water level. Prolonged exposure to high water temperature could also improve the sensitivity of fish. Key words: Walking catfish / spawning / water level / water temperature

Perch Perca fluviatilis is a widespread predator in European reservoirs, frequent in open waters but also known to spend a lot of time in the littoral zones. To get insight into how adult perch used and selected their habitat in an environment subject to water-level (WL) fluctuations, 21 perch were continuously tracked using acoustic telemetry over 2 years in the Bariousses Reservoir (France). The different available habitats were characterized by depth classes and substrate types, presence of emerging trees and presence of tree stumps in the littoral zone. We showed that perch habitat preferences were strongly dependent on the season, except for substrate type, and in line with their habitat use. Surprisingly we did not find any influence of the WL which, however, reduced the structural complexity of the littoral zone when lowering. In spring and summer, whatever the WL, we observed a strong preference for the littoral zone and complex habitats. In autumn and winter, perch migrated into deeper waters. However, the individual variability of the habitat preferences was quite high. This type of research helps to understand the spatial ecology of fish and provides useful guidance to hydromorphological restoration for fish populations.

The potential role of visual cues for microhabitat selection during the early life phase of a coral reef fish ( Lutjanus fulviflamma)

Prediction of fish catch in the Danube River based on long-term variability in environmental parameters and catch statistics

The present paper shows analysis of water level (the distance from the land surface to the water in the well under static condition) and water temperature observed at three different levels of Chuan no. 03 well to study the changes associated with the Wenchuan earthquake of 2008 and the 2011 Tohoku-Oki earthquake. Our analysis shows co-seismic changes in water level and water temperature associated with the increase in compressive stress associated with the Wenchuan earthquake. The water level shows an increase, whereas there was drop in water temperature at the shallow depth (395 m) and enhancement of water temperature at the middle (595 m) and the bottom (765 m) layers. However, no step change in water level or temperature of Chuan no. 03 well is observed associated with the Tohoku-Oki earthquake, only seismic wave propagation-induced water level oscillation and led to co-seismic response of water temperature. The analysis of the co-seismic responses and post-earthquake adjustment processes combined with the borehole histogram and the borehole temperature gradient data clearly show co-seismic changes in water temperature that could be closely associated with the changes in the regional stress and strain state and the distribution of the aquifer and the characteristics of the aquifer. The observed temperature variation of different layers in the borehole is likely to be controlled by the flow of water in the horizontal direction.

Experimental work on the reproduction of five species of fish endemic to Australia indicates the importance of specific water temperatures and floods as triggering mechanisms for spawning and for subsequent survival of young. Evidence has been obtained which suggests that the factor which stimulates the fish to spawn is produced when water comes into contact with dry soil. The species studied were Tandanus tandanus, Plectroplites ambiguus, Maccullochella macquariensis, Bidyanus bidyanus, and Carassiops klunzingeri. The spawning of these species is compared with some observations made on the heterochthonous Perca fluviatilis. Plectroplites ambiguus and Bidyanus bidyanus spawn at water temperatures above 23°C provided there is an accompanying rise in water level; both species produce pelagic eggs. Tandanus tandanus spawns at a temperature of 24°C and demersal eggs are laid in a gravel nest; a rise in water level is not essential. Maccullochella macquariensis spawns at 20°C provided there is a slight "run off" of water into the pond; eggs are laid in hollow logs or in similar situations. Carassiops klunzingeri spawns at 22.5°C and the eggs adhere to grass and twigs at the water's edge. Perca fluviadilis spawns at 11.5°C and all fish spawn in ponds over a short period if additional water is added, this ensures a more uniform water temperature throughout the pond.

Extensive floodplains and numerous lakes in the Amazon basin are well suited to examine the role of floodable lands within the context of the sources and processing of carbon within inland waters. We measured diel, seasonal and inter-annual variations of CO2 concentrations and related environmental variables in open water and flooded vegetation and estimated their habitat area using remote sensing in a representative Amazon floodplain lake, Lake Janauacá. Variability in CO2 concentrations in open water resulted from changes in the extent of inundation and exchange with vegetated habitats. Depth-averaged values of CO2 in the open water of the lake, 157 ± 91 µM (mean ± SD), were less than those in an embayment near aquatic vegetation, 285 ± 116 µM, and were variable over 24-h periods at both sites. Within floating herbaceous plant mats, the mean concentration was 275 ± 77 µM, while in flooded forests it was 217 ± 78 µM. The best statistical model that included CO2 in aquatic plant mats, water clarity, rate of change in water level and chlorophyll-a concentrations explained around 90% of the variability in CO2 concentration. Three-dimensional hydrodynamic modeling demonstrated that diel differences in water temperature between plant mats and open water as well as basin-scale motions caused lateral exchanges of CO2 between vegetated habitats and open water. Our findings extend understanding of CO2 in tropical lakes and floodplains with measurements and models that emphasize the importance of flooded forests and aquatic herbaceous plants fringing floodplain lakes as sources of CO2 to open waters.

Eisensteinhöhle is a 2 km long crevice cave that is significantly overprinted by hydrothermal karst processes. It was opened during quarrying in the Fischauer Vorberge, at the western margin of the Vienna Basin. This pull-apart basin cuts the eastern foothills of the Alps and is formed by a major NE-SW striking, sinistral transform fault. The western margin consists of NNE-SSW striking normal faults creating paths for thermal water to rise from the central basin. The deepest part of the cave, 73 m below the entrance, hosts a pond with 14.6 ±0.2 °C warm water that occasionally acts as a spring. The water level and temperature fluctuate and at a certain level, water visibly discharges into a nearby narrow fissure. As sporadic observations of the water level since 1992 gave no obvious connection to precipitation events, the connection to an aquifer and the origin of the water remained unknown. A pumping test, conducted on 13/7/2016, yielded a volume of the spring/pool of about 2.8 m3 that is fed by a very small inlet at the sandy bottom. At the time of the pumping test, the discharge was only 4.5 l/h but during previous overflow events, discharge values of up to 289 l/h were recorded. Water temperature and hydrochemistry hint towards a mixture of an old thermal component and a young meteoric component. During continuous monitoring of water level and temperature from October 2015 until November 2018, the water level was almost stable with few periods of high level (almost at overflow) that lasted for about 3 to 4 weeks each. The water temperature increased during most high stands and is positively correlated with the water level. Correlation of the high-resolution data on water level and temperature fluctuations with precipitation measurements at the nearest meteorological stations show a relation of water level to certain rainfall events and the sporadically taken long time records show a correlation with annual precipitation sums. Long-term observations also indicate a connection to groundwater levels in the Vienna Basin with a delay of about 8 weeks in Bad Fischau. In July 2017, the water level dropped suddenly and then recovered simultaneously in the time of several weak earthquakes in the vicinity. The data suggest that the spring in Eisensteinhöhle is influenced by precipitation. For one seismic event, there is a correlation with unusual water level changes at Eisensteinhöhle, but the rareness of earthquakes demands for a longer time series to confirm this observation.

Water level and discharge dynamics in human-affected lowland rivers

Habitat selection and spatial use was studied in a population of Myotis capaccinii (Bonaparte, 1837) in the eastern Iberian Peninsula during the spring of 2004. The radio-tracked bats used only aquatic habitats as foraging sites, and most foraging activity concentrated on rivers. Rivers were positively selected and showed the highest preference rank. Pools were also positively selected but only a single pool was used through the tracking period. Foraging was not evenly distributed along rivers. The features of the water surface further determined habitat selection. Open waters with smooth surfaces were selected over cluttered surfaces or waters completely covered by vegetation. This microhabitat preference is thought to be due to a greater efficiency in prey detection and capture over open calm waters. Nonetheless, the extremely high aggregation of foraging individuals observed suggests that the distribution of prey might also affect the location of foraging sites along rivers. Thus, conservation management of M. capaccinii should ensure protection of low-flowing or stagnant waters in rivers around the bats' main caves.

For centuries the Great Lakes have been treated callously These five magnificent lakes—Superior, Michigan, Huron, Erie, and Ontario—located along the eastern half of the Canadian–U.S. border have served as a virtual sewer catching waste from industry, agriculture, commercial shipping, and households. Their natural barriers to other water systems have been breached, exposing indigenous ecosystems to aggressive invaders. They’ve been used as a highway for colossal ships that require deepened and broadened channels to crisscross the lakes, and that import exotic species along with their intended cargo. At times it could seem that this long-suffering water system will see no end of indignities. But recent renewed focus on the unique and tremendous value of this resource by governments and communities surrounding the lakes may turn the tide of neglect and abuse. According to the U.S. Environmental Protection Agency (EPA), the Great Lakes contain 21% of the Earth’s and about 84% of United States’ surface freshwater. That’s about 22,000 cubic kilometers of water spread over 94,250 square miles. Each year the lakes provide more than 6.7 million cubic meters of water to municipalities and quadruple that to industry. They support a commercial fishery worth about $13 million as of 2002, according to the U.S. Geological Survey (USGS), and a sport-fishing industry of nearly $1.3 billion as of 2001, according to the U.S. Fish and Wildlife Service. Today about 25% of Canadians and 10% of Americans—a total of more than 33 million people—live in the Great Lakes watershed. “The whole industrial expansion that took place during the ‘robber baron’ era [of the late nineteenth century] expanded along the shores of the Great Lakes,” says Deborah Swackhamer, a University of Minnesota professor of environmental chemistry. Soon ships were carrying iron ore, coal, and limestone from mines and quarries to steel mills and later steel to factories and products to markets. In addition to serving as a transportation system, the lakes provided a place to discharge manufacturing by-products. Unlike a sewer, however, whatever enters this lake system stays awhile. On average, less than 1% of the five lakes’ water turns over each year, which means that many pollutants stay in place. They settle in sediments, adhere to other surfaces, become suspended in water, and bioaccumulate in organisms. Similarly, with the exception of migratory birds, most wildlife in the basin spend their entire life cycle in or near the lakes. As a result of all these stressors, the lakes now house fish that are dangerous to eat, water that can be unsafe to drink, anoxic “dead zones”—areas in which virtually no plants or animals can survive—that appear each summer like clockwork, and an ever-growing population of unwanted species from other parts of the world.

Migratory waterbirds depend on a complex network of wetlands globally for their life cycles. However, habitat loss and degradation pose risks to these networks’ sustainability, potentially impacting wetland habitat availability. This study investigates the impact of water level changes in Beijing’s Miyun Reservoir on white-naped cranes’ (Antigone vipio) habitat use. We utilized satellite imagery from 2000–2021 and monthly data from 2018–2023 to observe changes in the reservoir’s water and land areas. Additionally, the study tracked 32 cranes using GSM-GPS loggers, yielding insights into their movement patterns and habitat preferences. Our findings emphasize the significant influence of reservoir water levels on habitat availability for these cranes. Notably, our results indicate that the decrease in suitable migratory bird habitats in the reservoir is primarily attributed to high-water level management strategies. This study highlights the necessity for balanced management of aquatic and terrestrial areas in reservoir ecosystems to preserve migratory waterbird habitats.

We caught smolts of Arctic charr, Salvelinus alpinus (L.), Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in a trap situated at the mouth of the river Halselva (70° N 23° E), northern Norway during a 5-year period. Salmon and charr were the first to leave freshwater at the end of May, while most trout left freshwater about 14 days later. Whereas the midnight sun shines continuously during the downstream migration period, the light intensity has a diel intensity pattern. The majority of the descending migrants were recorded during the night. The number of descending fish was relatively low at water temperatures below 3°C. The increase in water level was largely caused by snowmelt and thus correlated with lower water temperatures. The number of migrants of all three species increased with increasing water level and decreased with increasing water temperature, with the exception of trout, which increased with water temperature. Notably, the increase in number of migrants was also correlated with the increase in water level the following day, indicating that fish movements represent an early response to a later spate. There was no significant relationship between the number of migrants and the daily change in water level or temperature. The three species were highly synchronised in their daily number of migrants. The strongest synchronisation was found between Arctic charr and Atlantic salmon, followed by Arctic charr and brown trout.