Diurnal Migration Research Articles

ПРОСТОРОВА ДИНАМІКА ПЛАНКТОННИХ І КОНТУРНИХ АЛЬГОМЕТАУГРУПОВАНЬ ЛОТИЧНИХ І ЛЕНТИЧНИХ ЕКОСИСТЕМ

This paper examines the spatial dynamics of planktonic and contour algal metacommunities in two- and three-dimensional spaces within lotic and lentic ecosystems in Ukraine, focusing on case studies from the Kyiv and Kaniv Water Reservoirs, as well as the Ukrainian section of the Western Bug River and its tributaries. To study the spatial dynamics of algae in the horizontal plane, the well-known geographic method called Distance Decay of Similarity (DDS) was applied. It allows finding out whether there is any decrease in similarity between the local algal communities with increase in the geographic distance between the localities. Using the DDS method, we developed an integrated approach for assessing the "spatial factor," which considers both the geographic distance between localities and their degree of hydrological isolation. It has been proven that this integrated approach makes it possible to obtain more reliable data on the impact of the “spatial factor” upon the dispersal of algae. The spatial dynamics along the vertical axis includes exchange of species between the localities of the same type and between the localities of different types. Vertical dynamics in the system of localities of the same type can be illustrated by vertical diurnal migrations of planktonic Cyanobacteria, such as Microcystis aeruginosa (Kützing) Kützing. Vertical dynamics between the localities of different types includes sedimentation of some algal species from the plankton to the bottom and aquatic plants’ surface during algal blooms periods. In complex studies of algal metacommunities it is important to analyze their spatial dynamics in the three-dimensional space, which combines both the horizontal plane and vertical axis. In three localities within Kaniv Water Reservoir 72 species of algae were identified in plankton, 81 species in benthos and 80 species in epiphytic communities. There were 21 common (potentially interacting) species between phytoplankton and microphytobenthos, 18 – between phytoplankton and epiphytic algal communities, and 44 between microphytobenthos and epiphytic algal communities. As many as 14 species were common for phytoplankton, microphytobenthos and epiphytic algal communities. The algal metacommunity under study comprised a total of 164 species. The higher degree of species similarity was observed between the local communities in the horizontal plane than along the vertical axis. Applying the three-dimensional space concept enables the study of species exchange between local algal communities of different types, which form metacommunities within large lotic and lentic continental ecosystems.

Impact of heteroaggregation between microplastics and algae on particle vertical transport

Understanding the impacts of microplastics (MPs) on aqueous environments requires understanding their transport dynamics and how their presence affects other natural processes and cycles. In this context, one aspect to consider is how MPs interact with freshwater snow (FWS), a mixture of algae and natural particles. FWS is one of the primary drivers of the flux of organic matter from the water surface to the bottom sediment, where zooplankton, diurnal migration, fish faecal pellets settling and turbulent mixing can also play prominent roles. Understanding how MPs and FWS heteroaggregation affects their respective settling velocities is important to assess not only MPs fate and transport but also their ecological impacts by altering FWS deposition and thereby nutrient cycling. In this present study, we obtained a mechanistic understanding of the processes controlling MPs settling dynamics and heteroaggregation with FWS and the subsequent impacts on the settling rates of both MPs and ballasted FWS. Here we used a plexiglass column equipped with a stereoscopic camera system to track the settling velocities of (1) MPs of various compositions, densities and morphologies, (2) FWS flocs and (3) MP–FWS agglomerates. For each experimental set, thousands of particles were tracked over a series of image sequences. We found that agglomerates with high-density MPs settled at least twofold faster than FWS alone, implying a much smaller residence time in the water column, except for cases with MP fibres or low-density plastics. These findings will help to refine MP fate models and, while contingent on MPs number, may impact biogeochemical cycles by changing the flux of nutrients contained in FWS to the sediment.

High resolution depth profile scanning of plankton organisms—VERTILICE

Knowledge of the vertical migration pattern of sea lice (Lepeophtheirus salmonis) copepodites is necessary for designing efficient measures to prevent lice infestations on farmed Atlantic salmon (Salmo Salar) in sea-cages. However, data can be challenging to acquire at a large scale under realistic circumstances without interfering with the natural behavior of the specimen. A mesocosm platform was built to help acquire this data consisting of a sensor package in an underwater housing being pulled up and down along a 11-meter-long transparent tube containing planktonic organisms while collecting image-, temperature- and spectrometer data. The platform was placed at a salmon farm and the acrylic tube was filled with L. salmonis copepodites and was pre-programmed to run a profile scan twice per hour for four consecutive days. Using a fully convolutional neural network, the copepodites were automatically counted – creating a depth profile of detected lice and measured light specter. The final results showed a diurnal migration pattern throughout the test period.•Capable of acquiring vertical density profiles of any aquatic species between 0,5 – 10 mm down to 11 m below the surface.•Fully automated and can be left unintended for weeks while collecting data.

Diurnal migration of birds in the Carpathian Mountains – characteristics, barrier effect and comparison with other regions in Poland

Despite the development of technically advanced methods of studying bird migration, classical visual observations remain a source of valuable data allowing a broad analysis of the picture of diurnal migration at a given site. We employed visual observations to investigate the spatial and temporal pattern of diurnal migration of birds in the Polish part of the Carpathians. During autumns 2011-2013, 28 localities distributed over the area were surveyed by experienced observers, while 12 localities were researched in spring 2015. The data collected allowed the determination of passage intensity indices and the timing of migration for more than 100 species in autumn and about 70 species in spring. Mean passage intensity was more than 3 times higher in autumn than in spring, with the highest recorded in the first half of October and mid-March, respectively. Compared to autumn, the peak of diurnal migration was shifted to later hours in spring. The passage occurred primarily along the N-S axis, followed by the NE-SW axis. No consistent evidence of a barrier effect of the Carpathians – expressing as a reduction in passage intensity in intra-mountain locations or in higher elevated areas – has been detected in this study. The cluster analysis showed that the assemblage structure of migrants in the mountain regions located in the south of Poland (Carpathian Mts., Karkonosze Mts., Świętokrzyskie Mts.) were more similar to each other than to a region situated far to the north on the Baltic coast.

Impact of anthropogenic infrastructure on aquatic and avian predator–prey interactions in a modified lowland river

Abstract The relationship between aquatic and avian predators and prey is a fundamental process that influences the ecological dynamics of freshwater communities; a landscape of fear underpins spatial and temporal habitat use of prey, i.e., non‐consumptive predation effects. For example, complex marginal vegetation and other natural in‐river refuges are known to be important for prey to manage predation risk and predators must alter their behaviour in response to habitat patches prey occupy. However, it is unclear how prey respond to predators, and vice versa, in heavily modified degraded lowland rivers with a high degree of river maintenance measures; a component critical for flood risk management globally. Such modifications could lead to prey seeking refuge at hazardous anthropogenic infrastructure, but a robust quantification of predator–prey interactions in this context is required to develop this understanding. Using multi‐beam sonar (Dual‐Frequency Identification Sonar), we non‐invasively and simultaneously quantified the temporal rate of predator–prey interactions, the attack behaviour of predators, and the refuge seeking behaviour of prey at a pumping station intake during winter in a heavily modified lowland river. Prey fish experienced temporally dynamic, density‐dependant, and species‐specific predation risks from two dissimilar predators (i.e., aquatic vs. avian); pike (Esox lucius) and cormorant (Phalacrocorax carbo). Generalised linear modelling revealed that prey refuge use was positively associated with predator attack rate. Non‐consumptive effects were evidenced by quantified changes to shoal structure (density, area), shoaling (group aggregation), and schooling (coordinated directional movement), including diurnal migrations to and from the pumping station intake for refuge. Our results show that in the absence of natural refuge habitats the natural landscape of fear shifted and speculate that prey fish were paradoxically dependant on hazardous anthropogenic infrastructure, i.e., a pumping station intake, for refuge from predators in a degraded lowland river. These findings strongly enhance our understanding of the impact of anthropogenic infrastructure on predator–prey interactions by demonstrating how flood risk management, including river maintenance measures, and associated anthropogenic infrastructure can impact the behavioural game played between aquatic and avian predators and their prey.

Offshore Migration of Summer Monsoon Low‐Level Jet on a Diurnal Scale

AbstractThis study investigates the diurnal migration of the low‐level jet (LLJ) over the Bay of Bengal in the summer monsoon, which remains understudied despite the well‐documented diurnal offshore propagation of rainfall worldwide. The southwesterly LLJ exhibits maximum strength during the night and morning. The LLJ undergoes a substantial eastward migration of approximately 600 km from the eastern offshore of India at midnight to the center of the Bay of Bengal by afternoon. A linear land‐sea breeze model is effective in capturing the diurnal migration with similar speed and phase. Including background wind offshore extends the migration, rather than confining it to the coast. This migration is driven by inertia‐gravity waves arising from the diurnal land‐sea thermal contrast and is influenced by the westerly upstream wind from the Indian subcontinent. Our results have important implications for understanding diurnal monsoon circulations and their associated precipitation.

Diurnal migration patterns in willow warblers differ between the western and eastern flyways

It is a long-standing view that the main mechanism maintaining narrow migratory divides in passerines is the selection against intermediate and suboptimal migratory direction, but empirical proof of this is still lacking. We present novel results from a willow warbler migratory divide in central Sweden from where birds take the typical SW and SE as well as intermediate routes to winter quarters in Africa. We hypothesized that individuals that take the intermediate route are forced to migrate in daytime more often when crossing wide ecological barriers than birds that follow the typical western or eastern flyways. Analyses of geolocator tracks of willow warblers breeding across the entire Sweden, including the migratory divide, provided no support for our hypothesis. Instead, birds that migrated along the western flyway were the most likely to undertake full day flights. The probability of migrating for a full day when crossing major barriers declined linearly from west to east. We speculate that this difference is possibly caused by more challenging conditions in the western part of the Sahara Desert, such as the lack of suitable day-time roost sites. However, it may equally likely be that willow warblers benefit from migrating in daytime if favorable tailwinds offer assistance.

Migratory Daily Departure Times of Chinese Sparrowhawks (Accipiter soloensis) and Gray-Faced Buzzards (Butastur indicus) in Taiwan

ABSTRACT The strategies that migratory raptors adopt during migration reveal their long-term adaptations to different environments along their migration routes and of their stopover sites. We recorded the daily departure time of Chinese Sparrowhawks (Accipiter soloensis) and Gray-faced Buzzards (Butastur indicus) during their southward migration in autumn 2019 at Kenting National Park, southern Taiwan, and 2020 in Yushan National Park, central Taiwan. At both watchsites, Gray-faced Buzzards started their migration journey about 1 hr earlier than Chinese Sparrowhawks. After adjusting for the local sunrise time, the first daily appearance time of Gray-faced Buzzards (–2.5 ± 9.3 min) was significantly earlier than that of Chinese Sparrowhawks (47.0 ± 29.3 min) by about 50 min at Kenting National Park. Though they initiated migration later in morning at montane stopover sites in Yushan National Park, the same trend was observed and with even greater difference, about 70 min. These results indicate that these two species migrate in different daily periods and suggest that Chinese Sparrowhawks might choose to exploit stronger thermal uplifts in September before leaving the island, as they started migration later in the morning. In contrast, Gray-faced Buzzards, a species more dependent on soaring-gliding flight, set off earlier in the day, probably to take advantage of stronger northeastern tailwinds that begin in October. We conclude that the prevailing monthly wind conditions, particularly influenced by the northeast monsoons, shape the different diurnal migration times of these two raptors migrating along the East-Asian Oceanic Flyway.

Evidence of Nocturnal Migration over Sea and Sex-Specific Migration Distance of Dutch Black-Headed Gulls

Avian migration is recorded over long distances, but some species winter much closer to their breeding sites or do not migrate at all. Specifically, the family of gulls Laridae shows great within and among species variation in migration. However, the migration ecology of many gull species is still unknown, even for abundant and widespread species such as the Black-headed Gull Chroicocephalus ridibundus. Here, we aimed to map the migration of Black-headed Gulls using GPS-tracking data from eight birds from a declining colony at Griend in the Dutch Wadden Sea to study migration routes and timing as well as wintering habitat of these birds. Furthermore, we used this GPS-data and 199 colour-ring resightings of adult birds from the same colony to study their wintering locations and habitat. The GPS-tagged birds migrated away from the Dutch Wadden Sea between mid-September and late November. All migrated in western to south-western directions to wintering areas at 130 to 560 km from the breeding colony. The GPS-tagged individuals wintered in The Netherlands, France and the United Kingdom and migrated towards these wintering sites both diurnally and nocturnally. The data indicate that most movements over the North Sea were nocturnal, whereas most migratory movements over land were during the day. Colour-ring data showed that females wintered significantly further away than males. We found no indications for differences in timing of migration between males and females and also no sex-specific preference for nocturnal or diurnal migration. We argue that the hitherto undocumented prevalence of nocturnal sea crossings calls for a better assessment of the potential risks of offshore wind energy developments in the North Sea. As such, this and new GPS-tracking data of Black-headed Gulls can aid in the conservation of this common and widespread species by providing novel insights in migration behaviour and the connectivity between breeding and wintering grounds.

Многолетняя динамика фауны и населения птиц аэропорта Челябинск (Баландино)

Over 30-year study period (1990–2021), 144 bird species, including 54 nesting species, were registered on the territory of the Chelyabinsk International Airport Balandino. Total bird population density varied from 147 ind./km² in 1990 to 215 ind./km² in 2020. In different years, dominant species in this area were Alauda arvensis, Motacilla flava, Saxicola rubetra, S. torquata, and Passer montana. In the first years of research, a significant decrease in the number of the most widespread species (Corvus frugilegus, C. monedula, Columba livia, Larus barabensis, L. canus, and L. ridibundus), crossing the airfield during seasonal and diurnal (forage) migrations, was revealed. This was caused both by decrease of population of some species (C. frugilegus) in the European and Ural-Siberian parts of their range, and by the deterioration of the state of forage lands on the airport territory after the elimination of solid waste landfills and a decrease of farmland areas nearby.

The salmon louse genome: Copepod features and parasitic adaptations

Copepods encompass numerous ecological roles including parasites, detrivores and phytoplankton grazers. Nonetheless, copepod genome assemblies remain scarce. Lepeophtheirus salmonis is an economically and ecologically important ectoparasitic copepod found on salmonid fish. We present the 695.4 Mbp L. salmonis genome assembly containing ≈60% repetitive regions and 13,081 annotated protein-coding genes. The genome comprises 14 autosomes and a ZZ-ZW sex chromosome system. Assembly assessment identified 92.4% of the expected arthropod genes. Transcriptomics supported annotation and indicated a marked shift in gene expression after host attachment, including apparent downregulation of genes related to circadian rhythm coinciding with abandoning diurnal migration. The genome shows evolutionary signatures including loss of genes needed for peroxisome biogenesis, presence of numerous FNII domains, and an incomplete heme homeostasis pathway suggesting heme proteins to be obtained from the host. Despite repeated development of resistance against chemical treatments L. salmonis exhibits low numbers of many genes involved in detoxification.

Radar monitoring unveils migration dynamics of the yellow-spined bamboo locust (Orthoptera: Arcypteridae)

Accurate monitoring of locust migration is the basis for early warning and emergency control programs. This article integrates laboratory recordings with the use of Ku-band vertical insect radar to assess migration of the yellow-spined bamboo locust Ceracris kiangsu (Orthoptera: Arcypteridae) in the China-Laos border area. Under laboratory conditions, field-caught individuals engaged in flight at temperatures above 20℃ and exhibited a wingbeat frequency of 18.5–31.1 Hz. Between July 6 and August 23, 2020, a total of 39C. kiangsu migration events were recorded by radar. Locust individuals only engaged in diurnal migration, with peak activity after 15:00. Flight was recorded at an average height, flight speed and density of 410 m above ground level, 35.8 km/h, and 1305.9 individuals/km3, respectively. High-density C. kiangsu swarms exhibited high flight speeds. Departing from Laos, locusts migrated north by west 27.4–35.0° into Jiangcheng county (Yunnan, China). Migration flight was affected by ambient temperature, while its speed was determined by that of prevailing wind currents. Individual locusts autonomously adjusted their heading direction in order to unify the travel direction of the migrant swarm. Ku-band high-resolution fully polarimetric insect radar can thus accurately assess the migration patterns of C. kiangsu locusts and thereby constitutes an important forecasting tool.

Using the Stable Isotopic Composition of Heliconoides inflatus Pteropod Shells to Determine Calcification Depth in the Cariaco Basin

Pteropods have been hailed as the “canary in the coal mine” for ocean acidification, however, questions remain about their life history, habitat, and the environmental parameters that the isotopic composition of their shells reflect. In order to use pteropods as recorders of ocean chemistry, it is first necessary to understand where they calcify and how this may change through the year, whether this signal is affected by dissolution, and if shells are retained in the subfossil, and eventually fossil, record. Here we create the first annual record of the stable isotopic composition of shells of the pteropodHeliconoides inflatusin the Cariaco Basin, Venezuela utilizing samples and data from the CARIACO time series. Sixty-fourH. inflatusspecimens from 17 sediment trap samples between November 1996 and April 1998, and 22 specimens from the late Holocene-aged CAR2000-MC-2 core were analyzed for shell condition (an assessment of the amount of dissolution that a shell has experienced), size, and carbon and oxygen isotopic composition. Carbon isotopic measurements of juveniles (< 1mm) were more variable than those in adults (>1 mm), suggesting juvenile pteropods likely have a higher growth rate, and therefore different metabolic vital effects, and a more varied diet than adult pteropods.H. inflatuswas found to have an apparent calcification depth of 51.2 ± 34.0 m, suggesting they calcify at the shallowest part of their diurnal migration in the mixed layer (10–35 m in the Cariaco Basin).H. inflatusshell calcification will therefore only be impacted by changes in water chemistry at mixed layer depths. The shell condition did not impact the stable isotopic composition of the shells in either the sediment trap or core sample, suggesting the potential for using the isotopic composition of pteropod shells as oceanographic proxies when they are preserved. Comparisons between sediment trap and core sample show a 0.5°C warming that is marginally significant and a significant 0.45‰ decrease in δ13C between the late Holocene and the late 1990's. These measurements reflect changes in oceanic conditions linked to anthropogenic fossil fuel emissions known as the Suess effect, and lay the groundwork for establishing pteropods as paleoceanographic proxies in the future.

Acoustic Monitoring of Diurnally Migrating European Bee-Eaters Agrees with Data Derived from Citizen Science

The use of Autonomous Recording Units (ARUs) for wildlife monitoring has increased in recent years. Acoustic monitoring has been used for a wide range of research topics, but it has rarely been used for monitoring wildlife migrations. In this work we evaluate the use of acoustic monitoring to characterise the diurnal migration pattern of a bird species, the European Bee-eater Merops apiaster. We set up 3–4 acoustic monitoring stations daily from 11 August to 21 September 2017 in north-eastern Spain, during post-breeding migration of the species. We used the Vocal Activity Rate (VAR), defined as the number of calls per unit time, as an index of Bee-eater abundance to describe the daily and seasonal migration pattern of the species. We also assessed the relationship between daily mean VAR estimated by ARUs, with citizen science data uploaded to the platform Ornitho.cat over a large spatial scale. According to mean VAR, intensity of migration increased weekly until the last week of August when it peaked, with species abundance decreasing to the lowest values in the study area by late September. A significantly higher number of calls was detected in the first and last hours of the day. Our results agree with previously published seasonal and daily migration patterns described for the species. VAR was significantly, positively correlated with the percentage of citizen science records of Bee-eater uploaded to complete checklists, used as an independent source to compare migration timing. Overall, our results, validated through citizen science data, show that acoustic monitoring can effectively provide complementary data for monitoring the bird migration of vocally active species. The use of ARUs may help to improve our understanding of migratory behaviour and be useful for a wide range of purposes.

Effective Vertical Transport of Particulate Organic Carbon in the Western North Pacific Subarctic Region

To quantify the biological carbon pump in the western North Pacific, a comparative biogeochemistry study of subarctic-eutrophic and subtropical-oligotrophic regions, the K2S1 project, was conducted. This study used data collected during the K2S1 project to re-examine the biological carbon pump in subarctic and subtropical regions of the northwestern Pacific with a focus on the factors governing the attenuation of the downward fluxes of particulate organic carbon (POC). Seasonal and time-series observations made during the K2S1 project revealed that primary productivity and the POC flux in the upper 200 m at subtropical-oligotrophic station S1 were comparable tothose at subarctic-eutrophic station K2, but the POC flux at a depth of ~5000 m at K2 was 2–3 times that at S1. Based on these observations, the index of vertical attenuation (exponent b of the “Martin curve”) was estimated to be 0.64 at K2 and 0.90 at S1. The downward transport of POC was therefore more efficient at the subarctic station than at the subtropical station. Sinking particles were ballasted mainly by biogenic opal (Opal) at K2 and by CaCO3 at S1. The results of a multiple linear regression analysis of sediment trap data indicated that among potential ballast materials, Opal was most strongly correlated with POC at K2. Thus, Opal might contribute to the more effective vertical transport of POC in the western North Pacific Subarctic region. In addition, lower water temperatures and dissolved oxygen concentrations in the twilight zone (200–1000 m depth) at K2 likely slowed microbial decomposition of organic carbon and may also have contributed to the smaller attenuation of the downward POC flux. However, seasonal observations indicated that the carbon demand of zooplankton (prokaryotes) in the water column at K2 was ~2.5 (1.5) times that at S1. These results were inconsistent with the lower rate of attenuation of POC fluxes at K2. Moreover, the carbon demand at the two stations inferred from the POC fluxes and the carbon fluxes associated with diurnal migration by zooplankton exceeded the carbon supply, especially at K2. Other sources of carbon, such as slowly sinking and suspended POC, might account for this mismatch.

Diurnal and crepuscular activity during fall migration for four species of aerial foragers

Most migratory birds, particularly passerines or songbirds, migrate at night. However, diurnal migration has many benefits, including the ability to use a fly-and-forage migration strategy that allows an individual to refuel while migrating. Despite these benefits, very little research has been undertaken on diurnal migrants, including aerial foragers, who can refuel on the wing. In this study, we use the Motus Wildlife Tracking System to examine the timing of Bank Swallow (Riparia riparia), Barn Swallow (Hirundo rustica), Cliff Swallow (Petrochelidon pyrrhonota), and Tree Swallow (Tachycineta bicolor) movements during fall migration. Using these data, we confirm the “common knowledge” that these species of aerial foragers are diurnal migrants. During fall migration, 88.2% detections across all species were during the day, and the remaining detections were during civil twilight (range of sun elevation angles: –5.4° to 0°). Most of the detections during the day were consistent with migratory movement, and most detections during civil twilight were consistent with movements to and from communal roosts. Collectively, these results indicate that during fall migration, these 4 swallow species migrate during the day and, like other aerial foragers, may use a fly-and-forage migration strategy.

Short-term changes in the quality of suspended particulate matter in a human impacted and mangrove dominated tropical estuary (Can Gio, Vietnam)

Suspended particulate matter (SPM) is a key component of coastal food webs and a key variable of nutrient budgets. Understanding its variability across short time scales in estuaries may help ecologists understand seasonal and diurnal migration of estuarine organisms, and answer how their nutritional requirements are fulfilled. It may also inform biogeochemists regarding the factors that influence import and export of nutrients between terrestrial and coastal ecosystems. This study aimed to link the dynamics of fatty acids, stable isotopes (δ13C and δ15N) and C/N ratios of SPM, revealing organic matter quality, to rapidly varying factors (SPM concentration, salinity and presence of daylight) and comparing this variability to the seasonal variation induced by the alternation of dry and wet seasons in the studied region. Our results revealed that these rapidly varying factors had a strong influence on the bacterial and the phytoplanktonic compartments of SPM. They suggest that tidally resuspended particles are the site of intense heterotrophic activity and that estuarine phytoplankton store lipids during the daytime up to substantially modifying SPM quality. Our study also shows higher freshness of SPM during the wet season. We expect this study to raise the interest of both biologists and biogeochemists to introduce daily variability of SPM in food webs and nutrient budgets modelling.

Habitat-mediated effects of diurnal and seasonal migration strategies on juvenile salmon survival

Habitat-mediated effects of diurnal and seasonal migration strategies on juvenile salmon survival

Abiotic triggers for sea and river lamprey spawning migration and juvenile outmigration in the River Rhine, Germany

AbstractThe activity patterns of migrating lampreys (sea lamprey Petromyzon marinus and river lamprey Lampetra fluviatilis) are poorly understood. This study uses extensive screening data from the cooling water intake of a nuclear power plant on the River Rhine, Germany, gathered on 1308 days over 46 consecutive months between 2011 and 2014. More than 34,000 lampreys were retrieved, of which the great majority (99.9%) were outmigrating nonfeeding postmetamorphic individuals. The main factors controlling outmigration were season, water temperature and river discharge. The bulk of downstream migration was observed each year in spring at water temperatures between 9 and 12°C, with earlier migrations during significant discharge peaks between December and February. The migration activity of postmetamorphic individuals declined during summer and autumn, regardless of discharge. Turbidity increased the occurrence of postmetamorphic lampreys and supported diurnal migration, which accounted for nearly 20% of all lamprey records. In winter, outmigrating individuals of both species exhibited significantly longer body lengths than those detected during other seasons. Haematophagus postmetamorphic sea lampreys were also retrieved (n = 28) and represent the most upstream records of parasitically feeding sea lamprey detected thus far. Adult lampreys migrating upstream were found mainly in spring, but in very low numbers, indicating high prespawning mortalities. The study points to a challenging future for the protection of lampreys in this area: the long duration and the round‐the‐clock nature of the observed migration demand flexible solutions to realise safe operational windows for water intake stations and to minimise impacts on juvenile lampreys.

Widespread distribution of OH/H2O on the lunar surface inferred from spectral data.

Remote sensing data from lunar orbiters have revealed spectral features consistent with the presence of OH or H2O on the lunar surface. Analyses of data from the Moon Mineralogy Mapper spectrometer onboard the Chandryaan-1 spacecraft have suggested that OH/H2O is recycled on diurnal timescales and persists only at high latitudes. However, the spatial distribution and temporal variability of the OH/H2O, as well as its source, remain uncertain. Here we incorporate a physics-based thermal correction into analysis of reflectance spectra from the Moon Mineralogy Mapper and find that prominent absorption features consistent with OH/H2O can be present at all latitudes, local times, and surface types examined. This suggests the widespread presence of OH/H2O on the lunar surface without significant diurnal migration. We suggest that the spectra are consistent with the production of OH in space weathered materials by the solar wind implantation of H+ and formation of OH at crystal defect sites, as opposed to H2O sourced from the lunar interior. Regardless of the specific composition or formation mechanism, we conclude that OH/H2O can be present on the Moon under thermal conditions more wide-ranging than previously recognized.