Daily Temperature Patterns Research Articles

Analyzing daily change patterns of indoor temperature in district heating systems: A clustering and regression approach

Measuring the indoor temperature of building rooms is a valuable approach for evaluating thermal comfort and providing feedback control for heat substations in district heating systems (DHSs) in China. Previous studies on indoor temperatures have primarily focused on analyzing their overall trends and influencing factors, while research on daily change patterns is lacking. This study utilized a clustering method to analyze the indoor temperature data from an actual DHS in Northeast China. First, a 24-h observation vector was constructed using the deviation between the actual and target values to represent the daily temperature pattern. Second, the k-means method was applied to cluster the values, and the quantity distribution and typical characteristics of each cluster were analyzed. Finally, a multi-nominal logistic regression model was used to analyze the influence of different factors on each cluster. The comparison results with the four representative clustering algorithms indicated that k-means was the optimal model and the optimal number of clusters was 4. The trend of each cluster was roughly the same, with the main difference being the fluctuation amplitude and distance from the target value. The differences between the clusters were related to various influencing features, with the primary return pressure for workdays and the secondary return pressure for holidays being the most significant. This study identified the optimal daily variation patterns of indoor temperature and analyzed the important features that affect this pattern, which is beneficial for enhancing the regulatory efficiency of DHS.

Combining a daily temperature pattern analysis and a heat-pulse system to estimate sediment depths in sewer systems

Sediment depth estimations in sewer systems based on the monitoring of temperatures, thermal properties, and the analysis of heat transfer processes. Surrogate model development, laboratory validation and uncertainty analysis.

Statistical Analysis of Temporal Variations in Patterns of Rainfall and Temperature in the Klang Valley

Malaysia is in the equatorial zone and experiences hot and humid climates throughout the year. During the rainy season, floods may occur in some parts of Malaysia, including the Klang Valley. During the flood occurrences, the residents may need to leave their houses and move to relief shelters. This disaster may happen because of the continuous heavy downpour in the area. Both incidents can be connected to climate change, and one way to investigate this is to examine differences in daily rainfall and daily temperature patterns through time. Climate change is inevitable and one of the causes is known as 'anthropogenic' in which it is caused by human activities. Geological records can provide evidence of climate change. However, there has been little statistical research on climate change in the Klang Valley. Even official organisations like the Department of Irrigation and Drainage Malaysia (DID) and the National Water Research Institute of Malaysia (NAHRIM) have not conducted this area of study. The goal of this study is to evaluate climate change in the Klang Valley using statistical analysis of temporal rainfall patterns. The data collection and statistical analysis are two critical parts of this study. Rainfall and average temperature data were obtained from their respective departments and websites. These data were sorted and filtered accordingly to get a satisfactory value for the analysis. Then, the correlation test and analysis of variance were conducted to find the relation between these data points. The results of this analysis were used to determine whether the variations in rainfall patterns in the Klang Valley are caused by climate change or otherwise. In addition to this, the statistical outputs indicate that there is a statistically significant finding in both data sets in which the decreasing temperatures may result in increasing rainfall and warmer conditions may lessen the rainfall. Surprisingly, the findings contradicted the expected outcome of this study, and it is believed that external factors are the primary contributors to these findings.

Temporal Patterns of Diet and Physical Activity and of Diet Alone Have More Numerous Relationships With Health and Disease Status Indicators Compared to Temporal Patterns of Physical Activity Alone.

Daily temporal patterns of energy intake (temporal dietary patterns [TDPs]) and physical activity (temporal physical activity patterns [TPAPs]) have been independently and jointly (temporal dietary and physical activity patterns [TDPAPs]) associated with health and disease status indicators. The aim of this study was to compare the number and strength of association between clusters of daily TDPs, TPAPs, and TDPAPs and multiple health and disease status indicators. This cross-sectional study used 1 reliable weekday dietary recall and 1 random weekday of accelerometer data to partition to create clusters of participants representing the 3 temporal patterns. Four clusters were created via kernel-k means clustering algorithm of the same constrained dynamic time warping distance computed over the time series for each temporal pattern. From the National Health and Nutrition Examination Survey (2003-2006), 1,836 US adults aged 20 through 65 years who were not pregnant and had valid diet, physical activity, sociodemographic, anthropometric, questionnaire, and health and disease status indicator data were included. Health status indicators used as outcome measures were body mass index, waist circumference, fasting plasma glucose, hemoglobin A1c, triglycerides, high-density lipoprotein cholesterol, total cholesterol, and systolic and diastolic blood pressure; disease status indicators included obesity, type 2 diabetes mellitus, and metabolic syndrome. Multivariate regression models determined associations between the clusters representing each pattern and health and disease status indicators, controlling for confounders and adjusting for multiple comparisons. The number of significant differences among clusters and adjusted R2 and Akaike information criterion compared the strength of associations between clusters of patterns and continuous and categorical health and disease status indicators. TDPAPs showed 21 significant associations with health and disease status indicators, including body mass index, waist circumference, obesity, and type 2 diabetes; TDPs showed 19 significant associations; and TPAPs showed 8 significant associations. TDPAPs and TDPs had stronger and more numerous associations with health and disease status indicators compared with TPAPs. Patterns representing the integration of daily dietary habits hold promise for early detection of obesity.

Host-Parasitoid Relationship between Apis mellifera (Linnaeus, 1758) and Senotainia tricuspis (Meigen, 1838) (Diptera, Sarcophagidae): Fly Aggression Behavior and Infestation Rates of Senotainiosis.

Senotainia tricuspis (Meigen, 1838) is a Sarcophagid dipteran endoparasitoid of Apis mellifera L., and myiasis, caused by this fly, is reported in several European, North African and Middle Eastern countries. Nevertheless, very little knowledge concerning the aggression and parasitisation behavior of S. tricuspis toward A. mellifera is available in the scientific literature, and the temporal pattern of aggression remains unclear. The aim of this investigation was to describe the aggressive behavior of S. tricuspis and to provide data on pupation and adult emergence in order to identify further tools for the control of senotainiosis in beekeeping. Data were collected in an apiary in Pisa province (Tuscany, Italy), where observations of aggressive behavior were conducted indirectly by using a VHS camera and also directly by an observer. Four behavioral categories of the attack were described. A total of 55 aggressions, 21 beecatchers, 104 chases and 6 parasitization events were recorded with the camera. Slow-motion recording analyses of the parasitization episodes resulted in contact of at least 1/6 s between the parasitoid and the host. Through four days of direct observations, a total of 1633 aggression events were recorded. The daily temporal pattern of the number of aggressions showed two main peaks: one during the morning hours (i.e., from 10:00 to 11:00) and one in the afternoon (i.e., from 15:00 to 17:00). The morphometric data on the first-instars of S. tricuspis allowed us to hypothesize a penetration in the bee through its prothoracic spiracle as a modality of entrance in the host body. Third-instars successfully pupate when sinking in topsoil or clay soil, and adults emerge when left to a 4 °C overwintering period of six months. Furthermore, the high mortality rate of those larvae that did not sink and did not pupate successfully suggests that reaching a certain depth in the soil is a determining factor for larvae survival and that mulch and/or minimum soil tillage could prevent severe senotainiosis in apiaries.

A Methodology for Air Temperature Extrema Characterization Pertinent to Improving the Accuracy of Climatological Analyses

The suggested methodology for the characterization of temperature extrema presents a multistep preprocessing procedure intended to derive extrema time series of correctly identified and thermally defined daily air temperature extrema pairs. The underlying conceptual framework for this approach was developed in response to the existing gaps in the current state of daily extrema identification and the development of extrema-based synthetic air temperature time series. A code consisting of a series of algorithms was developed to establish four-parameter criteria for a more accurate representation of daily variability that allows easy replication of temperature distribution based on the correct characterization of daily temperature patterns. The first preprocessing step consists of subjecting the high-frequency temperature time series to a theoretical diurnal observing window that imposes latitudinally and seasonally crafted limits for the individual identification of daily minima and maxima. The following pre-processing step involves the supplementation of air temperature extrema with the information on the occurrence of extrema timing deemed as vital information for the reconstruction of the temperature time series. The subsequent step involves the application of an innovative temperature pattern recognition algorithm that identifies physically homogeneous air temperature populations based on the information obtained in previous steps. The last step involves the use of a metric for the assessment of extrema temperature and timing parameters’ susceptibility to climate change. The application of the presented procedure to high-frequency temperature data yields two strains of physically homogeneous extrema time series with the preserved characteristics of the overall temperature variability. In the present form, individual elements of this methodology are applicable for correcting historical sampling and air temperature averaging biases, improving the reproducibility of daily air temperature variation, and enhancing the performance of temperature index formulae based on daily temperature extrema. The objective of this analysis is the eventual implementation of the presented methodology into the practice of systematic temperature extrema identification and preprocessing of temperature time series for the configuration of physically homogeneous air temperature subpopulations.

Temporal overlap of human and apex predator activity on wildlife trails and forest roads

The daily activity patterns of animals are modulated by external factors such as habitat selection, temporal niche selection, prey availability and predation risk. Furthermore, different species show a variety of responses to human disturbance; therefore, to understand the effects of human activities on wildlife, it is crucial to consider the disturbance characteristics (e.g. type, frequency, timing and location of human activity). Our objective was to evaluate whether vehicles on forest roads altered the daily temporal activity patterns of three apex predators; Eurasian lynx (Lynx lynx), the grey wolf (Canis lupus) and brown bear (Ursus arctos), using an extensive camera trap data set collected across a gradient of forest roads and wildlife trails in the Croatian part of the Dinaric mountains. We expected a low temporal overlap between humans and apex predators but predicted this even lower at sites where vehicles are present. Consistent with our expectations, the general overlap in temporal activity of all three apex predators and humans was low, the former being primarily active at night/dawn/dusk hours and the latter during daylight hours. In contrast, our results showed similarity in the temporal activity of all three predators on wildlife trails and forest roads where human activity was more frequent and diverse.

People with Stroke Are Most Sedentary in the Afternoon and Evening

Questions: What are the daily temporal patterns of movement behaviours (sedentary time, light-intensity physical activity, and moderate-vigorous physical activity) in people with stroke? Do daily temporal patterns of sedentary time differ (a) between subgroups of people with different movement behaviour classifications and (b) over time during the first year after stroke? Design: This study represents secondary exploratory analyses from an observational, longitudinal cohort study (n = 197). Participants: This study included people with first-ever stroke recruited from 4 hospitals in the Netherlands. Outcome Measures: Movement behaviour was objectively measured using the Activ8 activity monitor within 3 weeks after hospital discharge and again at 6 and 12 months later. Results: Participants spent the least time sedentary in the morning with proportionally more sedentary time as the day progressed with maximal sedentary time seen in the evening hours. This pattern did not substantially change over time. Sedentary prolongers spent significantly more absolute time sedentary for each hour of the day, but the daily temporal pattern of sedentary time did not differ between this group and either “sedentary movers” or “sedentary exercisers.” Conclusion: People living at home after stroke are highly sedentary, particularly in the afternoons and evenings, and this pattern does not change during the first year after stroke. Clinicians should encourage people with stroke to find meaningful tasks to do during the day to reduce their sitting time. Researchers developing interventions to encourage people to sit less should include particular focus on the afternoon and evening time periods.

Seasonal Migration and Daily Movement Patterns of Sympatric Overwintering Black-Necked Cranes (Grus nigricollis) and Common Cranes (Grus grus) in Caohai, Guizhou, China

Wintering Black-necked (Grus nigricollis) and Common (G. grus) cranes occur sympatrically in Caohai Wetland, Guizhou, China. Seasonal migration dynamics, daily movement patterns, and diurnal activity budgets of the two crane species were investigated in Caohai Wetland, in order to characterize their wintering activity differences and the mechanism of interspecific coexistence, during October - April 2014 - 2017. Black-necked Cranes wintered in Caohai for 147 ± 8 days, and Common Cranes for 169 ± 8 days. Common Cranes generally arrived in Caohai 11.4 ± 3.28 days earlier and departed 11.00 ± 3.20 days later than Black-necked Cranes. During winter in Caohai Wetland, the behavioral activities of both the Black-necked and Common cranes were strongly influenced by circadian rhythms. However, there were significant differences in daily temporal patterns between them in percent time spent in specific behaviors. Common Cranes left their roosting sites 20 min. earlier than Black-necked Cranes and returned 32 min. later. Common Cranes also spent more time foraging and being vigilant than Black-necked Cranes.

The use of cork in the thermoregulation of the hive: an innovation attempt to enhance non-wood products and beekeeping in Mediterranean forests

Hive thermoregulation is fundamental for the normal development of bee colonies and, consequently, hive productivity and honey bee health. External conditions mainly affect the walls of the hive. Therefore, hive construction materials and thermal conductivity features can influence its thermoregulation efficiency. The present trial made a comparison of experimental hives (modified Dadant-Blatt of 10 frames) made with cork as thermal insulator and conventional hives made entirely with firwood to evaluate their effects on thermoregulation of Apis mellifera ligustica colonies in Northwerstern Sardinia (Italy). The cork-modified beehives consisted of common conventional beehives modified by replacing the wooden walls with cork walls (pressed cork), whereas the control beehives (wooden hives) consisted of standard Dadant Blatt beehives entirely made of firwood. Environmental (especially nest internal temperature) parameters were assessed periodically. The daily temperature pattern of cork-modified beehives was more regular than that of control beehives. In addition, bees had a more efficient winter thermoregulation in cork-modified beehives compared with control hives.

Owls and larks do not exist: COVID-19 quarantine sleep habits

BackgroundThe coronavirus pandemic presented a unique opportunity to study the daily temporal patterns and sleep habits of humans. The question to be explored was: Are there discernible differences in sleep between the normal operational environment and the stay-at-home condition? MethodsThis international prospective study analyzed results from the sleep-wake patterns questionnaire, daily logs, and interviews. Surveys were administered to the healthy volunteers (age 15–60 y) with stay-at-home for a month or more, without previous sleep disorders and mood-related complaints; volunteers were not involved in online education/work daily timetable-related activities. ResultsWe analyzed 3787 subjects with average stay-at-home of 65 ± 9 days. The most significant changes in sleep occurred during the first ten days when the difference between weekdays and weekends disappeared and changes occurred in napping habits. The majority of the participants (66.8%) shifted toward eveningness when the self-selected sleep was possible and 1869 volunteers appeared to be owls (49.4%), 823 (21.7%) exercised “typical” sleep, 478 (12.6%) were larks, and 617 (16.3%) participants were completely desynchronized to the end of stay-at-home. In addition, 497 participants (13.1%) alternated their sleep habits. The most of the desynchronized participants (n = 414) were older than 50 years (age correlation r = 0.80), and predominantly males (n = 297, r = 0.76). ConclusionIn self-selected sleep conditions, the timing of sleep and sleep habits significantly differ from those of socially and economically fixed daily routine conditions. The changes in daily temporal patterns of humans during a prolonged stay-at-home situation indicate that human sleep habits may change according to existing living conditions.

Winter-spring temperature pattern is closely related to the onset of cambial reactivation in stems of the evergreen conifer Chamaecyparis pisifera

Temperature is an important factor for the cambial growth in temperate trees. We investigated the way daily temperatures patterns (maximum, average and minimum) from late winter to early spring affected the timing of cambial reactivation and xylem differentiation in stems of the conifer Chamaecyparis pisifera. When the daily temperatures started to increase earlier from late winter to early spring, cambial reactivation occurred earlier. Cambium became active when it achieves the desired accumulated temperature above the threshold (cambial reactivation index; CRI) of 13 °C in 11 days in 2013 whereas 18 days in 2014. This difference in duration required for achieving accumulated temperature can be explained with the variations in the daily temperature patterns in 2013 and 2014. Our formula for calculation of CRI predicted the cambial reactivation in 2015. A hypothetical increase of 1–4 °C to the actual daily maximum temperatures of 2013 and 2014 shifted the timing of cambial reactivation and had different effects on cambial reactivation in the two consecutive years because of variations in the actual daily temperatures patterns. Thus, the specific annual pattern of accumulation of temperature from late winter to early spring is a critical factor in determining the timing of cambial reactivation in trees.

Vertical distribution and daily patterns of birds in the dry deciduous forests of central western Madagascar

Data on the vertical distribution and ecological requirements of forest birds in western Madagascar are poorly documented. Strata use of forest-dwelling birds associated with vegetation structure and daily temperature patterns was examined in the dry deciduous forest of Kirindy. Six line transects of 1000 m each were used to survey birds and linear sampling to quantify vegetation structure. Data loggers were employed to record differences in temperature across vertical forest strata. A total of 3468 observations of 37 bird species were recorded. In the early morning, birds called frequently and used the canopy, at mid-day, when temperature in the upper strata increased on average around 7ºC, they tended to descend along a vertical gradient to the denser vegetation of the understory, presumably to avoid heat stress. In the case of largerbodied canopy birds, they occupied the mid-story during the heat of the day. Regardless of the time of the day, the mid-story was widely used by forest birds for feeding, roosting, and preening. These results demonstrate the sensitivity and vertical movements of birds to varying environmental conditions and provide new information on the ecology of Malagasy dry forest-dwelling birds.

A global analysis of cities’ geosocial temporal signatures for points of interest hours of operation

ABSTRACTThe temporal nature of humans interaction with Points of Interest (POIs) in cities can differ depending on place type and regional location. Times when many people are likely to visit restaurants (place type) in Italy, may differ from times when many people are likely to visit restaurants in Lebanon (i.e. regional differences). Geosocial data are a powerful resource to model these temporal differences in cities, as traditional methods used to study cross-cultural differences do not scale to a global level. As cities continue to grow in population and economic development, research identifying the social and geophysical (e.g., climate) factors that influence city function remains important and incomplete. In this work, we take a quantitative approach, applying dynamic time warping and hierarchical clustering on temporal signatures to model geosocial temporal patterns for Retail and Restaurant Facebook POIs hours of operation for more than 100 cities in 90 countries around the world. Results show cities’ temporal patterns cluster to reflect the cultural region they represent. Furthermore, temporal patterns are influenced by a mix of social and geophysical factors. Trends in the data suggest social factors influence unique drops in temporal signatures, and geophysical factors influence when daily temporal patterns start and finish.

Natural exposure to ultraviolet‐B radiation in two species of chameleons from Madagascar

Many reptiles require ultraviolet-B radiation between 290 and 315 nm (UV-B) to synthesize vitamin D3 and process dietary calcium. In captivity, exposure to too little or too much UV-B can result in health problems such as metabolic bone disease. While it is recognized that UV-B is necessary to successfully maintain many reptiles in captivity, the actual levels of UV-B that species are exposed to in nature is poorly known. We measured the UV-B exposure of two species of chameleon (Calumma brevicorne and C. nasutum) in the field in Madagascar over a period of four months. We found that both species were exposed to less UV radiation than that which was available in full sun. Only on rare occasions were chameleons observed in areas with a UV Index (UVI) greater than 3.0, and the median UVI for both species was only 0.3. There was no daily temporal pattern in UV exposure for C. nasutum, but C. brevicorne was found in areas with lower UV levels in the late afternoon when compared to late morning. Additionally, C. nasutum males showed higher UV exposure than females in late morning. Our results suggest that both C. brevicorne and C. nasutum can be classified as Ferguson Zone 1 species, and should be provided with a UV-B gradient in captivity that offers access to UV-B radiation as well as adequate shaded refuge.

Revisitation analysis uncovers spatio‐temporal patterns in animal movement data

Animals regularly return to locations such as foraging patches, nests, dens, watering holes, or movement corridors, and these revisited locations are often sites of ecological significance. Analyzing the temporal and spatial pattern of revisitation can lead to important insights into the life history and ecology of populations. We introduce the R package ‘recurse’ to calculate revisitations to locations in the movement trajectory or other locations for one or multiple individuals. The package also calculates metrics such as residence time and time between visits. It can be used to quantitatively identify frequently used sites (e.g. dens, nests, foraging locations), to examine patterns of revisitation and link them with covariates such as habitat features or climatic data, and to address conservation questions of interest about specific locations. We present an example application with movement trajectory data from a turkey vulture Cathartes aura during the breeding season and demonstrate analyzing recursions, specific locations, seasonal and daily temporal patterns, and visit timing. The ‘recurse’ package should be of interest both to ecologists looking to analyze their movement data and to conservationists needing site‐specific information for management and conservation actions.

Temporal and spectral patterns of fish choruses in two protected areas in southern Atlantic

The Laje de Santos Marine State Park (LSMSP) and Xixová-Japuí State Park (XJSP) are two protected areas (PAs) located in the southern Atlantic Brazilian coast. One month of continuous underwater sound recordings allowed determining that durable fish choruses was a major contributor of LSMSP and XJSP soundscapes. The choruses showed well defined daily periodicities and exceeded background ambient noise for some hours every day, principally at dawn and dusk. This work describes the daily temporal patterns and spectral characteristics of the studied PAs choruses. Annotations of some chorus temporal descriptors (start, peak and end time instants) allow obtaining a precise statistical representation of diel chorus occurrence. Average Power Spectral Density and cepstral analysis were used to determine quantitative values for choruses spectral characterization. Results show that the passive acoustic technique could be a cost-effective method for management and fish monitoring in PAs.

The Impact of Cycling Temperature on the Transmission of West Nile Virus.

West Nile virus (WNV) is an important cause of disease in humans and animals. Risk of WNV infection varies seasonally, with the greatest risk during the warmest parts of the year due in part to the accelerated extrinsic incubation rate of the virus in mosquitoes. Rates of extrinsic incubation have been shown in constant-temperature studies to increase as an approximately linear function of temperature, but for other vector-borne pathogens, such as malaria or dengue virus, nonlinear relationships have been demonstrated under cycling temperatures near the thermal limits of pathogen replication. Using typical daily air temperature profiles from three key periods of WNV amplification in a hyperendemic area of WNV activity in California's Central Valley, as well as a fourth temperature profile based on exposures that would result from daily mosquito host-seeking and resting behavior, we explored the impacts of cycling temperatures on WNV transmission by Culex tarsalis Coquillett, one of the principal vectors in the western United States. The daily cycling temperature ranges studied were representative of those that occur across much of California, but they did not significantly alter the extrinsic incubation period of WNV compared with estimates from mean temperatures alone. This suggests that within the relatively broad range we studied, WNV incubation rates are a simple function of mean temperature. Realistic daily temperature patterns that reflected mosquitoes' avoidance of daytime high temperatures during summer reduced transmission over time compared with air temperatures, indicating that adjustment for mosquito exposure temperatures would be prudent for calculating risk.

Temporal Dietary Patterns Derived among the Adult Participants of the National Health and Nutrition Examination Survey 1999-2004 Are Associated with Diet Quality

BackgroundTemporal dietary patterns, the distribution of energy or nutrient intakes observed over a period of time, is an emerging area of dietary patterns research that incorporates time of dietary intake with frequency and amount of intake to determine population clusters that may have similar characteristics or outcomes related to diet quality. ObjectiveWe examined whether differences in diet quality were present between clusters of individuals with similar daily temporal dietary patterns. DesignThe first-day 24-hour dietary recall data from the cross-sectional National Health and Nutrition Examination Survey, 1999-2004, were used to determine proportional energy intake, time of intake, frequency of intake occasions, and mean diet quality. Participants/settingData from 9,326 US adults aged 20 to 65 years were included. Statistical analyses performedThe mean diet quality, classified by the Healthy Eating Index-2005, of participant clusters with similar temporal dietary patterns derived on the basis of individual proportional energy intake, time of intake, and frequency of intake, were inferentially compared using multiple linear regression that controlled for potential confounders and other covariates (P<0.05/6). ResultsDiet quality differences were present between US population clusters exhibiting similar daily temporal dietary patterns (P<0.001 with one exception, which was P=0.08). Participant characteristics of race/ethnicity, age, household poverty-income ratio, and body mass index were associated with the temporal dietary patterns. The cluster representing the temporal dietary pattern with proportionally equivalent energy consumed during three evenly spaced eating occasions had a significantly greater mean total Healthy Eating Index-2005 score compared with the other temporal dietary pattern clusters. ConclusionsTemporal dietary patterns are associated with differences in US adult daily diet quality, demonstrating that elements beyond food and nutrient intake, such as time, can be incorporated with dietary patterns to determine links to diet quality that enhance knowledge of the complicated interplay of time and dietary patterns.

Control of activity patterns in crowded groups of male noble crayfish Astacus astacus (Crustacea, Astacidea) by light regimes: A way to increase the efficiency of crayfish production?

Abstract Most crayfish species exhibit behavioral traits (solitary lifestyle, high aggressiveness, establishment of social hierarchies) which in intensive aquaculture systems result in low survival due to cannibalism and reduced overall growth. In addition to selective breeding programs, this situation may be improved by identifying culture conditions (e.g., light regimes) which can alleviate the negative impact of specific behavioral patterns on an effective crayfish production. The present experiments demonstrate a pronounced nocturnality of male noble crayfish Astacus astacus. The circadian system seems to be of rather little relevance to the daily pattern of the collective activity in crowded crayfish groups. Parameters of the light regime (the L/D-ratio of 24-h light–dark cycles, light intensity, background illumination during nighttime) were shown to have a crucial and immediate influence on (i) the daily temporal pattern of activity, (ii) the ‘effective density’ (density of individuals which are simultaneously active), and (iii) the overall daily amount of activity. Except for individuals at the verge of molting, activities were restricted to the scotophase, largely independent of the LD-ratio. The effective density was negatively, the overall daily amount of activity positively, correlated with the length of the scotophase. Both parameters decreased significantly under a dim nocturnal background illumination. An optimal combination of high overall daily activity and low effective density was found under a short-day photoperiod of LD 8:16. As in the long run overall daily amount of activity and effective density may be relevant to growth and survival, respectively, manipulations of the light regime are suggested to be a promising approach to improve the efficiency of a commercial crayfish production. The present results may be useful in designing appropriate long-term experiments which actually measure survival and growth. Statement of relevance Light as potential factor to improve production in RASs.