Post-spawn movements and habitat use by greater redhorse, Moxostoma valenciennesi

Abstract – A combination of radio telemetry and surface observations were used to characterize the movements and habitats of greater redhorse, Moxostoma valenciennesi , after spawning in the Grand River, Ontario, Canada. This river supports a large population of greater redhorse that migrate upstream in the spring to spawn on riffles. After spawning, greater redhorse moved as far as 15.2 km downstream of spawning areas and maintained summer home ranges in low velocity runs. Mean (±SE) water depth used by greater redhorse was 46.3±0.9 cm, and water velocities were less than 5 cm/s. Greater redhorse were usually located over cobble/gravel substrates that were covered with Cladophora. Although interspecific associations with golden redhorse, M. erythrurum, common carp, Cyprinus carpio , smallmouth bass, Micropterus dolomieu , and northern hog sucker, Hypentelium nigricans , were observed, most greater redhorse associated with conspecifics. Areas and habitat types used throughout the summer did not change, until relocation to overwintering areas occurred in early autumn.     

Characterization of the quality of the gametes and sex steroid levels during spring and summer spawning events in pejerrey Odontesthes bonariensis reared under natural conditions of temperature and photoperiod

Pejerrey Odontesthes bonariensis spawning period takes place during the end of winter and spring and, depending on temperature conditions, during late summer and autumn. Nevertheless, the occurrence and quality of the summer–autumn spawning period have not been well documented and are not considered for aquaculture production. In this context, this study aimed to characterize the reproductive activity of pejerrey reared in captivity under natural conditions of temperature and photoperiod throughout a year in order to summarize the spawning quality of the two spawning periods. The present results showed that pejerrey might spawn from late winter to the end of the spring with a peak in October (mid‐spring) and, also during summer and early autumn, interrupted by a period of 56 days without spawning activity in between. The extension of both spawning periods was almost equal (67 and 69 days). Nevertheless, higher relative fecundity and larger egg size were observed during the first spawning period, associated with higher levels of oestradiol measured in females demonstrating that it is better than the second spawning. The fertilization rate was not affected throughout the reproductive periods. These differences in the reproductive parameters are discussed in order to design specific strategies to increase seed production.     

Diverse juvenile life‐history behaviours contribute to the spawning stock of an anadromous fish population

Habitat quality often varies substantially across space and time, producing a shifting mosaic of growth and mortality trade‐offs across watersheds. Traditional studies of juvenile habitat use have emphasised the evolution of single optimal strategies that maximise recruitment to adulthood and eventual fitness. However, linking the distribution of individual behaviours that contribute to recruitment at the population level has been elusive, particularly for highly fecund aquatic organisms. We examined juvenile habitat use within a population of sockeye salmon (Oncorhynchus nerka) that spawn in a watershed consisting of two interconnected lakes and a marine lagoon. Otolith microchemical analysis revealed that the productive headwater lake accounted for about half of juvenile growth for those individuals surviving to spawn in a single river in the upper watershed. However, 47% of adults had achieved more than half of their juvenile growth in the downstream less productive lake, and 3% of individuals migrated to the estuarine environment during their first summer and returned to freshwater to overwinter before migrating back to sea. These results describe a diversity of viable habitat‐use strategies by juvenile sockeye salmon that may buffer the population against poor conditions in any single rearing environment, reduce density‐dependent mortality and have implications for the designation of critical habitat for conservation purposes. A network of accessible alternative habitats providing trade‐offs in growth and survival may be important for long‐term viability of populations.     

Resource use of crucian carp along a lake productivity gradient is related to body size,predation risk,and resource competition

Generalist fish species can feed on a wide resource spectrum and across trophic levels depending on resource availability and trophic interactions. Crucian carp (Carassius carassius) represents a good candidate species to investigate variation in the trophic ecology of generalist fish as it can be found in highly variable fish communities and its resource use is well documented. In this study, we explored the trophic ecology of crucian carp at the individual and population levels using stable isotope and gut content analysis. We tested if trophic resource use varied according to lake productivity, predation risk, intra- and interspecific competition, or individual fish size. We found that crucian carp resource preference was highly variable among and within lakes. In predator-free lakes, small crucian carp occurred in high densities, showed increased interindividual specialisation, and relied mainly on pelagic zooplankton. In presence of predators, large crucian carp occurred in low densities and included greater proportions of benthic macroinvertebrates in their diet. This shift in resource use was further favoured in productive, shallow lakes where littoral prey were probably abundant. Resource partitioning was an important factor determining crucian carp niche use, as fish had higher trophic position in absence of other cyprinids. Crucian carp showed highly dynamic resource use and food preferences in response to variable environmental conditions. Overlooking complex diet preferences of generalist fish may lead to an oversimplification of freshwater community dynamics.     

Spawning aggregation behaviour in the Creole perch,Percichthys trucha (Percichthyidae): A target species for conservation

1. Habitat fragmentation and loss threaten freshwater biodiversity worldwide. Habitats that are essential as fish spawning and nursery sites are critical, and must be identified for conservation purposes. Littoral zones within Patagonian lakes, especially shallow vegetated areas, represent important areas for the Creole perch, Percichthys trucha.
2. Spawning behaviour has been little studied, so it is not known whether these movements are performed in groups. A particular area of a deep lake in northern Patagonia was studied to identify the environmental conditions under which spawning occurs, and to analyse spawning aggregation behaviour in relation to the lunar cycle.
3. To identify spawning sites, spawning occurrence time, and the environmental parameters that determine it, fish capture data were analysed. Underwater cameras were also set up at three depth strata in the shallow zone to detect spawning aggregation behaviour. Aggregation was scored as the greatest number of individuals present in a single frame, and the number present per depth stratum. The relationship between the lunar cycle and Creole perch abundance by depth was then determined.
4. This is the first visual record of a spawning bed and the spawning aggregation behaviour of Creole perch in Patagonian lakes. The abundance of mature Creole perch in the shallow strata during the austral spring suggests that vegetated areas constitute spawning sites. Spawning aggregation takes place at a shallow depth 2 days before the full moon.
5. As the reproductive behaviours of Creole perch are important phenomena in the life history of the species, the results of this study have important implications for conservation and management.

     

Littoral spawning habitats of three southern Arctic charr (Salvelinus alpinus L.) populations

Abstract Arctic charr populations in southern latitudes are nonmigratory, with all life‐stages limited to freshwater lakes and in‐ or out‐flowing tributaries. Although many of these populations are reported to also spawn in lake littorals, little is known about the physical characteristics of putative spawning grounds. A total of 23 discrete spawning sites within three Irish lakes were located by fyke netting of spawning adults and snorkelling in littoral habitats. Spawning sites were found to be long, narrow strips running parallel to the shore at a maximum depth of 124 cm. Spawning sites were limited to areas of coarse mineral substrate with an adequate (c. 8 cm) depth of clean interstitial spaces. In individual lakes, combined areas of spawning sites made up 0.4–0.7% of available littoral. Egg densities varied considerably between sites (33–900·eggs m^?2) and were significantly correlated with gradient and width of spawning sites. No evidence of redd digging was found. The shallow, localised and restricted nature of spawning grounds makes such populations vulnerable to anthropogenically induced postoviposition changes in surface water level, eutrophication processes such as increased lake sedimentation and elevated nutrient status.     

Communal pair spawning behaviour of vendace (Coregonus albula) in the dark

Mating in nature is rarely random, and most fish species have refined mating systems. The vendace (Coregonus albula) is a short‐lived, small‐sized, cold‐water‐adapted pelagic schooling species that is known to spawn in groups, but the actual mating system of this species, like many other group‐spawning fishes, has not been described in detail. Vendace typically spawn in the littoral or sublittoral zones of lakes in late autumn, and the hatching of larvae occurs close to icebreak in the following spring. In our large study lake, vendace larvae were caught in 93% of 1,149 random sampling locations lake‐wide. We examined the courtship and mating of vendace under experimental conditions by nonintrusive observation of the natural behaviour, to clarify whether spawning activity is associated with illumination and to assess the postspawning mortality of vendace. Here, we describe and document in detail for the first time the spawning behaviour of vendace: they spawn in the dark, and females release a small portion of their eggs (on average 1% of mean total individual fecundity) when the female and male, side by side, dart from near the bottom up towards the surface, that is perform a spawning rise. Males and females had several spawning rises (on average 1,200). Our results showed high postspawning mortality (56%). The spawning stress seems to be a potential component of mortality regulating the lifespan duration of vendace.     

Patterns of movement of adult northern pike (Esox lucius L.) in a regulated river

Abstract –  We performed a tagging study on one of the spawning populations of northern pike ( Esox lucius L.) of the River Kajaaninjoki in Finland. Northern pike is the main predator in many lakes and rivers in the northern hemisphere. Previous tagging studies have shown a general tendency to sedentary behaviour by pike. Whether individuals in a fish population adapt a sedentary or moving strategy may affect population persistence. To study if the spawning population consists of sedentary or moving individuals and the pattern of movements, we tagged 40 pike with radio transmitters and followed them from May 2002 to June 2003. Pike were caught and tagged during the spawning season in the mouth of the River Kajaaninjoki which flows into one of the largest lakes in Finland, Lake Oulujärvi. Our results suggest that the pike spawning population consisted of sedentary pike ( N  = 16) dwelling the whole year in the river, and moving pike ( N  = 24) which moved to Lake Oulujärvi after the spawning period. Pike exhibited homing behaviour, as most of the migrating pike returned to the same spawning area in the following year. Large pike had a higher movement rate than small pike during the summer and seasonally the movement rate was lowest during the spring and highest during the summer.     

Differing body size between the autumn and the winter–spring cohorts of neon flying squid (Ommastrephes bartramii) related to the oceanographic regime in the North Pacific: a hypothesis

The neon flying squid (Ommastrephes bartramii), which is the target of an important North Pacific fishery, is comprised of an autumn and winter–spring cohort. During summer, there is a clear separation of mantle length (ML) between the autumn (ML range: 38–46 cm) and the winter–spring cohorts (ML range: 16–28 cm) despite their apparently contiguous hatching periods. We examined oceanic conditions associated with spawning/nursery and northward migration habitats of the two different‐sized cohorts. The seasonal meridional movement of the sea surface temperature (SST) range at which spawning is thought to occur (21–25°C) indicates that the spawning ground occurs farther north during autumn (28–34°N) than winter–spring (20–28°N). The autumn spawning ground coincides with the Subtropical Frontal Zone (STFZ), characterized by enhanced productivity in winter because of its close proximity to the Transition Zone Chlorophyll Front (TZCF), which move south to the STFZ from the Subarctic Boundary. Hence this area is thought to become a food‐rich nursery ground in winter. The winter–spring spawning ground, on the other hand, coincides with the Subtropical Domain, which is less productive throughout the year. Furthermore, as the TZCF and SST front migrate northward in spring and summer, the autumn cohort has the advantage of being in the SST front and productive area north of the chlorophyll front, whereas the winter–spring cohort remains to the south in a less productive area. Thus, the autumn cohort can utilize a food‐rich habitat from winter through summer, which, we hypothesize, causes its members to grow larger than those in the winter–spring cohort in summer.     

Reproduction and recruitment of the brown shrimp Crangon crangon in the inner German Bight (North Sea): An interannual study and critical reappraisal

The brown shrimp, Crangon crangon, is the most important target of the coastal crustacean fisheries in the German Bight. In order to evaluate the relation between the abundance of ovigerous females and larvae in spring and the recruitment success in autumn, we first analysed the seasonal appearance of ovigerous females and larvae from weekly samples throughout 2012. The spawning season in the German Bight extends over several months comprising multiple unsynchronized spawning events. The minimum shares of ovigerous females appeared in early autumn, and the highest shares in late winter bearing mostly early egg stages. We defined the putative start of the reproductive cycle for November when the frequency of ovigerous females started to increase. There was no distinct separation between winter and summer eggs, but a continuous transition between large eggs spawned in winter (the early spawning season) and batches of smaller eggs in spring and summer. Larval densities peaked in April/May. Consequently, regular annual larval surveys from 2013 to 2016 were scheduled for April/May and extended to six transects covering the inner German Bight. Ovigerous females were most abundant in shallow waters above the 20‐m isobaths, which also explained regional differences in abundance between the regions off North Frisia and East Frisia. No relation was obvious between the number of larvae in spring and recruited stock in autumn. Due to the short lifespan of C. crangon, the combination of various abiotic factors and predator presence seems to be the principal parameters controlling stock size.     

Residency of adult Atlantic cod (Gadus morhua) in the western Gulf of Maine

A mark and recapture study of cod in the western Gulf of Maine was conducted to study the seasonal movements of fish, particularly as they related to areas closed to commercial fishing. A total of 27,772 cod were tagged, and 1334 (4.8%) were recaptured with sufficiently detailed recapture location and date to be included in the study. Results indicated that the group is resident to the area and sedentary. Although there were a small percentage of fish (2.5%) that traveled long distances (>100 km), most were recaptured near their release location. There was no linear relationship between fish length and linear distances traveled, and linear distance traveled was only weakly related to days-at-large. For all groups of cod tagged and released in particular areas and months, mean distances traveled were small (<65 km), rates of travel were slow (<0.2 km/day), and rates of group dispersion were <50 km²/day. There were no recognizable spatial or temporal patterns in the mean angles of travel for groups released in various month/area combinations, and the angular deviations associated with the mean angles were quite large. Although there seems to be little pattern in the movement of cod in our study area, temporal and spatial changes in abundance indicate that movements are occurring.

The general pattern was a concentration of large cod into one small, inshore area (Area 133) in both the spring and winter, and dispersion from this area in the ensuing months. Monthly percentages of ripe cod in Area 133 provide evidence for two spawning groups; a winter group that spawns from November through January, and a spring group that spawns from April through July. Thus it is likely that the observed spring and winter concentrations of fish in Area 133 were associated with spawning. Fish in the spring group were the largest encountered in the study. The study also provided some evidence of natal homing, i.e. a return to the same spawning grounds year after year, for the spring spawning group. Although there is some exchange of fish between most of the closed areas, the timing of the closures appears to protect the largest aggregations of cod.     

Winter movements of burbot (Lota lota) during an extreme drawdown in Bull Lake, Wyoming, USA

Winter movements of burbot (Lota lota) were monitored in Bull Lake, Wyoming during a record low water storage period in the winter of 1985–1986. Burbot with surgically implanted ultrasonic transmitters were commonly sedentary during the drawdown. The fish that did move were most active during dusk and at night in winter and during the day in spring. Burbot did not appear to occupy well defined home ranges or show discernible movement patterns. Movement into shallow water during winter was attributed to colder water temperatures and the onset of the spawning season. Burbot were always found associated with silt substrates during the drawdown. Aerial photographs of the exposed bottom revealed that virtually all suitable spawning and nursery habitat for burbot was eliminated by the 13.4-m drawdown.     

Winter movement activity patterns of anadromous Arctic charr in two Labrador lakes

Anadromous Arctic charr, Salvelinus alpinus, feed in the marine environment for several months during the summer and migrate back to fresh water in late summer to spawn and/or overwinter. While overwintering, anadromous Arctic charr are generally believed to reduce or cease feeding, and they are poorly described in their winter movement activity. This study used telemetry data collected from two locations to describe overwintering movement activity, including interindividual variation. Movement activity declined markedly during the ice‐covered period, suggesting opportunistic maintenance feeding was used as an energy conservation strategy. Fall and spring movement was correlated with daylight hours, and ice break‐up had a significant effect on the timing of outmigration. Movement activity was negatively correlated with body length, with smaller individuals being more active than larger fish. Although general activity patterns were evident, there were significant differences among individuals, particularly during spring immediately prior to lake departure. Lake size and individual differences in metabolic rate may account for some of this variation.     

Detection efficiency and habitat use to inform inventory and monitoring efforts: juvenile coho salmon in the Knik River basin,Alaska

Imperfect detection associated with sampling gear presents challenges for wildlife inventory and monitoring efforts. We examined occupancy dynamics and habitat use of juvenile coho salmon, Oncorhynchus kisutch, in shallow lake environments over a summer and early fall season in the Knik River area of south central Alaska using models which control for and estimate sampling gear detection efficiency. In addition, we present statements for the probability that observed absences at a survey site or from a survey area (a collection of sites) are true absences given some amount of sampling effort and analysts' beliefs about site occupancy and sampling gear detection efficiency which can be used to guide inventory and monitoring efforts for juvenile salmon or other wildlife and plant species. Occupancy modelling results demonstrate that minnow traps were effective at sampling juvenile coho in shallow lake environments, with a mean probability of detection across the study period of 0.68 (i.e., probability of detecting the presence of juvenile coho given that they are present at a trap site; SE = 0.03). Juvenile coho salmon migrated into shallow water lakes in late summer and early fall, presumably to seek out overwinter habitat. N‐mixture modelling examination of habitat use demonstrated that once in shallow lake environments, juvenile coho were widely distributed across a range of microhabitats, with some evidence for preference for shallower depths and warmer water temperatures.     

Environmentally conditioned,year‐round volitional spawning of cobia (Rachycentron canadum) in broodstock maturation systems

Year‐round control of the spawning cycle of cobia (Rachycentron canadum) has been established by using water temperature manipulation. To compare the effectiveness of using this method to induce volitional spawning in cobia, two 80 m³ recirculating aquaculture systems (RAS) were used. Temperatures in one of the maturation tanks (‘Mat 1’) were maintained between 27 and 29°C for 12 months of the 15.5‐month study period. Temperatures in the second maturation tank (‘Mat 2’) were allowed to fluctuate naturally throughout the year and ranged from 20 to 32°C. A total of 101 spawning events occurred in the tanks between the spring of 2008 and the summer of 2009 (3 April 2008 to 17 June 2009). Of the 38 total spawning events in Mat 1, 17 of them (44.7% of all Mat 1 spawning events) occurred during the off‐season (fall and winter). The egg viability rates did not differ significantly (P > 0.05) between on‐ and off‐season spawns in Mat 1. Conversely, cobia broodstock exposed to natural water temperatures (no environmental manipulation) in Mat 2 followed the natural pattern of warm water (>26°C) dependence, limiting egg production to spring and summer seasons. This method of water temperature manipulation allows for effective control of the cobia reproductive cycle without compromising egg viability.     

Variation in spawning responses, egg and larvae productions from induced rohu (Labeo rohita) during pre-monsoon and monsoon seasons: Relationship with hormonal changes and oocyte responsiveness during final maturation

Early induced spawning in captive rohu (Labeo rohita) often encounters with reduced spawning performances and devaluation of final product. The present study attempted to gain insight into the problems associated with poor performance of rohu during pre-monsoon spawning. A combination of sGnRHa and domperidone was used to induce final oocyte maturation (FOM) and ovulation in rohu during early (pre-monsoon, PM) and normal (monsoon, MN) spawning. The spawning performance parameters such as, spawning response, production and quality of egg and larvae showed significantly lower values (p < 0.05) in PM, when compared with MN spawning. The egg and spawn productions were recorded as 2.6 ± 0.05 and 2.41 ± 0.05 during the MN season, which were reduced by almost 50% in the PM season. Moreover the quality of egg and hatchling was devaluated significantly (p < 0.05) and exhibited higher percentage of mortality and abnormality in PM than those recorded in the MN season. The plasma concentration of carp gonadotropin (cGtH), 17β-estradiol (E) and 17α20β-dihydroxy-4-pregnen-3-one (DP) in relation to progress of FOM and ovulation at different seasons exhibited marked variation in hormonal profiles particularly in E and DP of PM fish. Higher initial plasma E (3.8 ± 0.3) and a distinct E peak clearly indicated the lack of transition from vitellogenic to post-vitellogenic stages that prevailed in PM rohu. Delayed DP and cGtH surge during FOM and ovulation resulted in longer latency period in spite of higher water temperature (31.5 °C) that prevailed during the PM period. In-vitro study on oocyte maturational competence (OMC) clearly depicted the lack of maturational competence in ovarian follicles during PM than MN in rohu. However priming the fish with purified carp gonadotropin (PCG) enhanced the acquisition of OMC in PM rohu in such an extent, that no marked seasonal differences (p > 0.05) in OMC were remained further, when compared with MN follicles. The PCG mediated acquisition of maturational competence was found to be dependent fully on new mRNA and protein synthesis in PM fish. The present study clearly demonstrated that the oocytes' unresponsiveness to hormonal induction was mainly responsible for reduced spawning performance in PM rohu, which could be ameliorated through PCG priming to achieve better spawning response in rohu during the pre-monsoon period. Thereby, the rohu fry production could be initiated successfully as early as May, allowing public and private hatcheries to produce larger age-0 rohu fingerlings ensuring reliable steady source of stocking materials for grow-out system earlier in the season.     

Partial nomadism in large‐bodied bream (Abramis brama)

The recent focus on a common movement ecology paradigm has increased awareness about the importance of distinguishing different movement patterns for understanding their specific impact on animal ecology and evolution. One specific form of movement is nomadism, where animals move between habitats in an arrhythmic fashion. Although not yet described in detail for freshwater fish, nomadism between lakes within drainage systems could affect local lake food webs in an otherwise unpredictable fashion. In this study, we used passive telemetry to describe inter‐lake movements of 1,280 individually tagged adult benthivorous bream (Abramis brama) over nine contiguous years in a drainage system with two paired lakes. The movements can best be described as partial nomadism, where a part of the population is neither resident nor migratory, but instead moves between lakes in a variable, arrhythmic fashion, often with long residency in one lake before moving to the other. We found extensive between‐year variation in the proportion and direction of bream moving, with higher movement propensity being partly associated with lower somatic condition. Notably, movements out of lakes were significantly more in direction of the neighbouring lake than away from the paired lakes, suggesting that at least direction was not random. Since bream are important ecosystem engineers, fluctuating densities of adult bream could affect ecological stability in lakes. Our study suggests that fish populations in interconnected lakes within drainages should not be treated as isolated units, and we discuss this in relation to lake ecology and the importance for lake ecosystem management.     

First-year overwinter mortality in Eurasian perch (Perca fluviatilis L.) Results from a field study and a simulation experiment

Abstract– The importance of overwinter mortality of 0+ perch ( Perca fluviatilis L.) in central European lakes was estimated using a stochastic simulation model. The probability of overwinter mortality of a perch cohort was calculated by using a model developed for yellow perch ( P. flavescens Mitchill). Winter duration from a long-term data set and the length of perch at the end of the first year from five lakes were used as input data. After 1000 simulation runs, the total extinction of a cohort in the lakes studied was never predicted. Mortality rates of more than 0.5 were only predicted in two of the five lakes, and rates of more than 0.3 in these two lakes were predicted in approximately 10% of all cases. For two consecutive winters differing in duration, the length-frequency distributions of 0+ perch in the autumn and following spring were compared by a graphical method. No significant size-dependent mortality of smaller individuals could be detected in any of the populations studied. Simulated spring length-frequencies were derived from observed autumn length distributions by the same model that was used for the stochastic simulation. These simulated and the empirical spring length-frequency distributions were not identical. The differences between the two distributions were attributed to growth, which occurred between the sampling dates. The results from the simulation and the analysis of the empirical data suggest that high overwinter mortality caused by starvation is rare in central European lakes.     

Seasonal movements of non‐native lake trout in a connected lake and river system

Abstract Non‐native lake trout, Salvelinus namaycush (Walbaum), threaten native salmonid populations in the western United States. Effective management of lake trout requires understanding movements within connected lake and river systems. This study determined the seasonal movements of subadult lake trout in the Flathead River upstream of Flathead Lake, Montana, USA using radio telemetry. The spatiotemporal distribution of lake trout in the river was related to water temperature. Lake trout were detected in the river primarily during autumn, winter and spring, when water temperatures were cool. By contrast, fewer were detected when temperatures were warmest during summer and during high spring flows. Downriver movements to Flathead Lake occurred throughout autumn and winter when water temperature decreased below 5 °C, and in late spring as water temperature rose towards 15 °C and river discharge declined following spring runoff. Upriver movements occurred primarily in October, which coincided with migrations of prey fishes. These results suggest that lake trout are capable of moving throughout connected river and lake systems (up to 230 km) and that warm water temperatures function as an impediment to occupancy of the river during summer. Controlling source populations and maintaining natural water temperatures may be effective management strategies for reducing the spread of non‐native lake trout.     

Inter- and size-specific patterns of fish seasonal migration between a shallow lake and its streams

Abstract –  This study used passive telemetry (passive integrated transponders) to evaluate winter migration in three species of cyprinids (roach ( Rutilus rutilus (L.)), white bream ( Blicca bjoerkna (L.)) and rudd ( Scardinius erythrophthalmus (L.))) and their potential predators (pike ( Esox lucius (L.)) and perch ( Perca fluviatilis (L.))) between a shallow lake and its streams. Migration patterns were investigated from October to June, and a substantial part of the roach (40%) and white bream (55%) populations tagged in the lake during autumn migrated during winter into the streams, whereas only very few piscivores (<2%) migrated. In contrast to roach and white bream, only few rudd (<6%) migrated, which is likely a consequence of different overwintering strategies, e.g., rudd overwintering in shallow highly structured habitats. Small rudd migrated more than larger rudd, whereas there were no size-differentiated migration patterns for roach or white bream. Migration of the cyprinid fishes was generally initiated in late October and ended in May, and specific synchronised bursts of migration were observed in December, January and April, suggesting that migration is triggered by one or more proximate environmental cues. The cyprinid fishes generally entered the streams in late afternoon or in the morning, depending on season, but overall migration patterns varied between the three streams. We suggest and discuss that our results have great implications for lake management as well as for the interpretation of seasonal trophic dynamics in shallow lakes.