Differential Mortality Rates of Fin-Clipped and Carlin-Tagged Roach (Rutilus rutilus L.)

Roach were marked by fin-clipping (N= 15888) or tagged with Carlin-tags (N= 1476) during their spawning migration in two tributaries to Lake Årungen, Norway, in 1980. A total of 1746 of these roach were recaptured during spawning in 1981. The recapture rate of fin-clipped roach was significantly higher than the recapture rate of Carlin-tagged roach, probably due to differential mortality rates.     

Reproductive and growth strategies of the red roach, Rutilus arcasii (Steindachner, 1866), in two contrasting tributaries of the River Duero, Spain

The life-histories of red roach were assessed in the R. Moros and the R. Ucero, two contrasting tributaries of the R. Duero. Growth occurred from April to October and Ucero red roach were larger than those in the Moros from their second year onwards. Condition increased with gonad development and abruptly decreased after spawning in both populations. The condition of Ucero fish recovered during the summer, but that of the Moros fish remained low. The same year classes (1980 and 1982) dominated both populations. River Moros red roach spawned in a 4-week period between the end of April and early June, while the spawning season of Ucero red roach lasted until August. The length to fecundity relationship was similar for both populations, and fecundity and ovum size increased with fish length. The life-history traits of these red roach populations are discussed in relation to current life-history theories.     

Fish recruitment in a canal with intensive navigation: implications for ecosystem management

The young-of-the-year (YOY) fish community in Oder-Havel-Kanal, a navigable canal in the German lowlands, assessed from May to October 1999, was dominated by tolerant species especially roach Rutilus rutilus and perch Perca fluviatilis . Roach dominance was high in May and June and low during the rest of the sampling period. The dominance pattern of perch was inversely related to that of roach. Significantly higher densities of significantly smaller YOY fishes were found in bays compared with the straight reaches of the main channel which was the result of an aggregation of 0+ year roach in bays in May and June. Parallel to low structural variability (spawning and nursery habitats), the intensive ship traffic may have been a major force structuring the fish communities in the canals. Measured ship-induced flow velocity in straight reaches was about four times higher than in bays of the canal. Maximum flow velocities caused by barge tows were also four times higher than those induced by pleasure boats. The study demonstrated the relatively low fish reproductive potential of a navigable, artificially embanked lowland canal. To improve fish reproduction, modification of canal banks is highly advisable to preserve existing bays and tributaries and even to create additional ones.     

Comparative study of reproductive biology in single and multiple-spawner cyprinid fish. II. Sex steroid and plasma protein phosphorus concentrations

The dynamics and regulation of oogenesis in single and multiple-spawner cyprinid fish showing group-synchronous oocyte development, was investigated in three species from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. This paper compares the seasonal profiles of sex steroids (oestradiol-17β, testosterone and 17,20β-dihydroxy-4-pregnen-3-one) and plasma alkali-labile protein phosphorus. Different patterns of plasma oestradiol-17β (E2) and plasma protein phosphorus (PPP) have been observed not only between the single and the multiple spawner fish, but also among the two multiple spawners. In roach, two increases of E2 levels were observed. The first occurred in September after a short gonadal quiescent period, and coincided with the increase of the PPP at the onset of exogenous vitellogenesis. The second took place in spring before the spawning season. The low PPP recorded during that period probably reflected its rapid incorporation by the oocytes. In both multiple spawners, highest values of PPP were recorded just before the spawning season. In white bream, the PPP declined progressively once the differentiation of exogenous vitellogenic oocytes was completed before the onset of the spawning season. In bleak, PPP levels remained high throughout the spawning season and corresponded to a sustained oocyte recruitment during the whole of this period. Regardless of the pattern of oocyte growth recruitment, the E2 concentrations were high in both multiple spawner species during the breeding season. In the three species, testosterone levels remained low regardless of the maturation stage (ranging from 0.6 to 13.4ng ml^?1). Except for relatively high concentrations of 17,20βP in roach during final maturation and postspawning stages (20 and 28 ng ml^?1, respectively), low levels of this steroid were measured in these cyprinids, and especially in the multiple spawner fish. The role of this progestogen as the maturation inducing Steroid is discussed.     

Movement and feeding ecology of recently emerged steelhead in Lake Ontario tributaries

Steelhead (Oncorhynchus mykiss) ascend several Lake Ontario tributaries to spawn and juveniles are often the most abundant salmonid where spawning is successful. Movement and diet of recently emerged subyearling steelhead were examined in three New York tributaries of Lake Ontario. Downstream movement occurred mainly at night and consisted of significantly smaller fry that were feeding at lower levels than resident fry. Fry fed at the highest rate during the day and chironomids and baetids were the main components of their diet. The diet composition of steelhead fry was closely associated with the composition of the benthos in Trout Brook but more similar to the composition of the drift in the other streams. Daily ration was similar among streams, ranging from 10.2 to 14.3%. These findings are consistent with previous findings on the ecology of steelhead fry, as well as fry of other salmonid species.     

Spatial population structure of the Neotropical tiger catfish Pseudoplatystoma metaense: skull and otolith shape variation

Using geometric morphometrics, the skull and otolith of tiger catfish Pseudoplatystoma metaense were analysed to identify population structure in tributaries of the Apure River (i.e. the Sarare, Caparo, Guanare, Portuguesa and San Carlos Rivers) in the Orinoco basin, Venezuela. The analyses show uniformity in skull and otolith shapes of P. metaense within and among four tributaries, with only the Caparo River showing significant differences. Within the Apure basin, the stock of P. metaense was differentiated through spawning, refuge and nursery areas. This study concludes that populations of P. metaense from each major tributary in the Orinoco basin should be considered as part of a metapopulation system for management purposes. Human disturbances in the catchment have directly reduced the spawning areas available to this species, decreased the total biomass and changed the spatial distribution of spawning areas.     

The population density, growth rate and production of roach Rutilus mtilus (L.) in Tjeukemeer, The Netherlands

A method of estimating the population density of roach in Tjeukemeer (21.3 km²) using 20 529 introduced fin-clipped fish is described. Fyke nets proved to be an effective method of sampling the population for marked fish during the spawning season. A total of 20 277 roach were processed during the recapturing period. The population density of roach (⋝ 14 cm) was estimated to be 1 246 458. The growth rate of roach in the lake although relatively poor (von Bertalanffy's L ∞ for males and females, 22 and 26 cm respectively) for the species was similar to that recorded in three other Friesian lakes. The mortality rate of males was higher than that of females. Logarithmic length-weight regression analyses showed that the value of the coefficient varied both within and between the sexes, that of females being higher (range 3.03–3.375) than that of males (range 2.76–3.254). Seasonal changes in the size of the coefficient were due to a disproportionate loss of gonad weight in larger fish. The fecundity of the population was comparatively high for the species.
The total production of the population was estimated to be 95 hg ha⁻¹ of which 39 kg ha⁻¹ was contributed by fry. In older (⋝ IV) fish the production of females (12 kg ha⁻¹) exceeded that (2 kg ha⁻¹) of males, due to differences in their growth and mortality rates. The relatively poor performance of roach in Tjeukemeer, in terms of biomass and production was due to a scarcity of zoobenthos and competition from other species offish. There is no evidence either from this study or the literature that the productive potential of roach in lakes is high, even though macrophytes and detritus can be consumed in significant amounts.     

Breeding Tubercles, Papillomatosis and Dominance Behaviour of Male Roach (Rutilus rutilus) During the Spawning Period

We studied the relationship between the breeding tubercle ornamentation (i.e. skin roughness) and male pre‐spawning dominance and courtship behaviour in roach (Rutilus rutilus) within an experimental laboratory system. Sexually mature fish were caught during their migration to their spawning pond and their behaviours were studied in an artificial spawning arena. Males behaved naturally both in terms of male–male interactions and attempts to achieve spawnings. Males having many, large breeding tubercles (i.e. rough skin) were significantly more often dominant in our dyadic trials than those with smooth skin. The dominant male in the trial exhibited a more active courtship behaviour than its subordinate rival. Papilloma skin disease did not affect the dominance rank. As a result of the relationship between skin roughness and male dominance, breeding tubercles may be used by the females as a cue for choosing a high‐quality mate in a roach lek. Thus, breeding tubercles might offer a workable tool for examination of sexual selection among cyprinids.     

Can the risk of parasite infection in fish cause the ecological differentiation in the population of roach Rutilus rutilus (Cyprinidae)?

Population characteristics of macroparasite infection (prevalence and intensity) in juvenile roach Rutilus rutilus have been studied in one of the tributaries of the Rybinsk Reservoir. The level of infection and parasite diversity is higher in the mouth part than in the upper reaches of the river. Habitats in the upper reaches are characterized by a high degree of irregularity of the risk of infection. The intensity of parasitic infection varies from the absence of parasites to 100% infection. Our data confirm the hypothesis about adaptaive value of the spawning migration to habitats with lower risk for the infection of offspring with parasites. Heterogeneous conditions in the upper reaches of the river make it possible for juvenile fish from a migrating part of the population to grow in relatively safe conditions. Differences in the strategy of the spawning migration can be based on the ecological differentiation as a result of which the groups oriented either at the local adaptation or at migration to the other habitat are formed in the population.     

Using parentage analysis to estimate rates of straying and homing in Chinook salmon (Oncorhynchus tshawytscha)

We used parentage analysis based on microsatellite genotypes to measure rates of homing and straying of Chinook salmon (Oncorhynchus tshawytscha) among five major spawning tributaries within the Wenatchee River, Washington. On the basis of analysis of 2248 natural‐origin and 11594 hatchery‐origin fish, we estimated that the rate of homing to natal tributaries by natural‐origin fish ranged from 0% to 99% depending on the tributary. Hatchery‐origin fish released in one of the five tributaries homed to that tributary at a far lower rate than the natural‐origin fish (71% compared to 96%). For hatchery‐released fish, stray rates based on parentage analysis were consistent with rates estimated using physical tag recoveries. Stray rates among major spawning tributaries were generally higher than stray rates of tagged fish to areas outside of the Wenatchee River watershed. Within the Wenatchee watershed, rates of straying by natural‐origin fish were significantly affected by spawning tributary and by parental origin: progeny of naturally spawning hatchery‐produced fish strayed at significantly higher rates than progeny whose parents were themselves of natural origin. Notably, none of the 170 offspring that were products of mating by two natural‐origin fish strayed from their natal tributary. Indirect estimates of gene flow based on F_ST statistics were correlated with but higher than the estimates from the parentage data. Tributary‐specific estimates of effective population size were also correlated with the number of spawners in each tributary.     

Seasonal movements and tributary-specific fidelity of blue sucker Cycleptus elongatus in a Southern Plains riverscape

This study used acoustic telemetry and a multistate Cormack–Jolly–Seber model to determine the seasonal movement patterns of blue sucker Cycleptus elongatus from 2015 to 2017. Several hypotheses were ranked using AIC_c, and it was determined that the movement patterns of blue suckers in a mainstem reach below a hydropower dam (i.e., tailwater) differed from those of blue suckers tagged in the major tributaries (perennial with stream order >3). This study estimated a low probability (≤0.13) blue suckers would leave the tailwater reach at any time during the study. Conversely, blue suckers tagged in the major tributaries had a high probability (≥0.88) of leaving after the spawning season (February–May). Blue suckers tagged in the major tributaries displayed a high probability (0.83) of returning to the tributaries in the spawning season of 2016 when discharges were high. Blue suckers also had a higher probability of fidelity to the tributary where they were tagged (0.65) rather than straying to different tributaries (0.18). The majority of tagged blue suckers that strayed selected the only undammed tributary in the study area. In 2017, spring discharges were low, and the probability of blue suckers returning to any major tributary was low (0.19), with little difference in the probability of displaying site fidelity (0.10) vs. straying (0.09).     

Comparative study of reproductive biology in single- and multiple-spawner cyprinid fish. I. Morphological and histological features

To clarify the dynamics and regulation of oogenesis in single- and multiple-spawning cyprinid fish with group-synchronous oocyte development, a multidisciplinary approach to their reproduction was undertaken using three species from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. The gonadosomatic index (GSI) and histomorphometric changes (distribution of oocyte size, relative proportion of the various oocyte stages) in the ovary are compared. Different patterns of GSI and oocyte growth were observed both between the single- and multiple-spawner fish and between the two multiple spawners. Maximum GSIs were higher in roach (21%) than in bleak and white bream (17.7 and 14.5%, respectively), and compared to the rapid decline of GSI in the roach population, the GSI of multiple spawners decreased progressively during the spawning season. In roach, a short gonadal quiescent period and an early onset of vitellogenesis was recorded from late summer onwards whereas, in bleak and white bream, exogenous vitellogenesis was not systematically observed before winter. A protracted spawning season and/or a low water temperature in autumn are hypothesized to explain this long period of gonadal quiescence. In bleak, during the spawning season, the oocytes recruited arose from the stock of endogenous vitellogenesis and attained the final maturation stage very rapidly. This recruitment occurred during the whole spawning season. In white bream, the differentiation of vitellogenic oocytes from smaller oocytes was completed before the onset of the spawning season. During the spawning period, the proportion of vitellogenic oocytes decreased progressively whereas the percentage of oocytes in the final maturation stage remained approximately constant.     

Feeding migration of roach, Rutilus rutilus (L.), in Lake Arungen, Norway

In the period April–July 1980 we studied the feeding migration and food of roach in a small tributary of the eutrophic Lake Årungen, south-eastern Norway. Tagging experiments revealed a tendency in roach to utilize a specific tributary both for feeding and for spawning. The mean size of roach ascending the tributary in late June and July was significantly larger than the mean size of roach spawning 1–2 months earlier, probably due to higher water discharge in July than in May and June. The experiment indicates two separately motivated migrations involving homing. The roach fed more profitably in the tributary than in the lake, both in terms of food availability and predator avoidance.     

Host-constrained epidemiology of the fish tapeworm Ligula intestinalis (L.)

Investigations into the biology of the roach, Rutilus rutilus (L.), and Ligula intestinalis (L.) populations at Slapton Ley, Devon were carried out between October 1982 and December 1984, and additional data collected from the lake since 1977 have been re-analysed. The Ligula population exhibited some unusual features: a limited specificity, a persistently low abundance and a scarcity of multiple infections. The population dynamics of the roach were also unusual in that the individual growth rate was one of the fastest in Britain, the survival was very poor and the year classes tended to alternate in strength. Whether the unusual epidemiology of Ligula could be explained by the unusual population dynamics of the roach is investigated. The transmission period of Ligula to the roach was limited to their first few months of life, probably due to a limited period of feeding on copepods by the fry. This narrow transmission window was almost certainly the major factor that has prevented the abundance of Ligula plerocercoids attaining high levels in the fry or of increasing in subsequent years, and has resulted in their abundance being determined entirely by transmission events to the fry. The limited transmission period has also caused the life-cycles of the roach and Ligula populations to become synchronized. At other localities, the abundance of Ligula is typically high, and can have a significant effect on the mortality of the host population, but, with the low abundance at Slapton, Ligula-induced roach mortality was insignificant. The rapid growth of the roach fry was the most likely explanation for the limited period of feeding on copepods, and the large size, short life-span and low abundance of the roach probably also constrained the build-up of the Ligula population in the lake. The random frequency distribution and scarcity of multiple infections was not considered unusual in view of the very low plerocercoid abundance. The very low abundance of Ligula, the separation of the spawning of roach and rudd in time and space, and the scarcity of rudd may account for the absence of infection in this species. It was concluded that the Ligula population in Slapton Ley was being constrained by the atypical population dynamics of the roach, and not vice versa as theory predicts.     

Seasonal resource selection by blue suckers Cycleptus elongatus

Telemetry data were used to quantify seasonal resource selection and rank‐preferred habitat types for blue suckers Cycleptus elongatus in the middle Missouri River and its tributaries, Iowa, Nebraska, South Dakota, U.S.A. Habitat diversity required by C. elongatus to complete its annual life‐history cycle was evident by interseasonal variation in habitat selection. Tributaries and unchannelized portions of the middle Missouri River system were selected during the inferred spawning season (spring), habitats along shorelines in the channelized middle Missouri River were selected for postspawning (summer) and areas of reduced current were generally selected for the period preceding spawning (autumn). This study provides insight into mature C. elongatus behaviour throughout its annual life cycle. Furthermore, these results document the interseasonal variability in habitat selection of C. elongatus and highlight the need for development of habitat selection models for other imperilled fish species in aquatic systems affected by anthropogenic developments.     

Ranges of Regulation of Sodium, Potassium, Calcium, Magnesium Concentrations in Plasma, Erythrocytes, and Muscle Tissue of Rutilus rutilus under Natural Conditions

As a result of studies for 3 years on the roach Ratilus ratilus under natural conditions, it was shown that the Na, K, Ca, and Mg content in the blood plasma, erythrocytes, and muscle tissue as well as muscle water were maintained year after year within definite ranges characterizing normal values for these parameters. Comparison of variations in the Na, K, Ca, Mg blood plasma concentrations in different fish species revealed the presence of common limits for each of these elements. Throughout the year the most essential changes in the roach blood and tissue cation levels were found during reproduction period. During spawning the fish are characterized by the state of acute stress with parameters indicating a decrease in stability and exhaustion of adaptive possibilities in animals. Intensification of defense reactions, including those providing maintenance of the water–salt homeostasis occurs shortly before spawning for a preliminary preparation to the stress situation.     

Feeding and reproductive biology of the currito,Hoplosternum littorale,in the Venezuelan llanos with comments on the possible function of the enlarged male pectoral spines

Synopsis The reproductive biology of roach, Rutilus rutilus, was investigated during 1980–1982 in a small tributary of the eutrophic Lake rungen, southeastern Norway. The upstream migration started in early May with medium or falling water levels and water temperatures of 6–10° C, and lasted until late May or early June. Roach (both males and females) migrating early in the season were larger than roach migrating late in the season. Males matured on average one year younger than females. The first males were mature at age 2 years, the first females were mature at age 3 years. Males were smaller than females in all age groups. There was no significant year to year variation in mean length of male and female roach in the various age-groups. Mean population fecundity during 1980–1982 was estimated to be 19 × 10⁶ eggs or 63300 eggs m^–2 of spawning area. The survival rate of eggs and small roach varied considerably due to rapid and unpredictable changes in water and silt levels. Mean annual survival rates for mature male and female roach were 0.30 and 0.52, respectively. The survival rates did not vary with age.     

The distributions of larval and juvenile fishes in Amazonian rivers of different nutrient status

1. Previous work has indicated, at least in two river systems, that some Characiformes species migrate from nutrient‐poor rivers to spawn in nutrient‐rich rivers. In the present work, larval and juvenile fish were surveyed to index spawning activity in order to determine whether this spawning pattern is repeated in nine major tributaries of the Amazon basin. 2. Adult Mylossoma aureum, M. duriventre, Colossoma macropomum, Anodus elongatus, Triportheus elongatus, Brycon cephalus, Semaprochilodus insignis, S. taeniurus and Prochilodus nigricans were recorded in nutrient‐poor and nutrient‐rich rivers. However, larval and juvenile individuals of these species were found in nutrient‐rich rivers only, indicating that spawning activity was restricted to that river type. 3. Concentration of suspended solids in the river was correlated with total ichthyoplankton density and related to species composition of juvenile characiform assemblages. 4. Our findings reinforce the hypothesis that nutrient‐rich rivers and associated floodplains function as spawning and nursery grounds, and suggest that they function as source habitats for these species in the Amazon Basin.     

Validation of Alburnus timarensis from the Lake Van basin,eastern Anatolia (Teleostei: Cyprinidae)

The Lake Van basin located in eastern Anatolia is inhabited by two species of Alburnus: Alburnus tarichi is a migratory species foraging in the lake and spawning in all tributaries, while A. timarensis is resident in streams and is known only from one tributary of the lake, the Karasu. It could be shown that A. timarensis is a valid species, which is rediagnosed here. Both species are syntopic during the spawning season, but are well distinguished by size, gill raker and lateral line scale counts.     

Reproduction, Growth, and Migration of Fishes in a Regulated Lowland Tributary: Potential Recruitment to the River Meuse

Many European rivers are characterized by a canalized main channel, steep stony embankments, the absence of aquatic vegetation, regulated flow dynamics, reduced hydrological connectivity to the floodplains and a lack of spawning and nursery areas for many fish species. In such regulated rivers, tributaries may be particularly important for recruitment of fish populations in the main channel. This paper describes the reproduction, growth and migration of fishes in the Everlose Beek, a regulated lowland tributary stream of the river Meuse (The Netherlands), using bi-weekly sampling from January to December 2002. A total of 8615 fishes were caught, belonging to 13 different species. The fish species were classified into three groups, viz., residents, migrants and transients, based on the presence of various life-stages in the tributary. Size-frequency data suggest that each group uses the Everlose Beek differently: (i) Stone loach (Barbatula barbatula), Gudgeon (Gobio gobio) and Three-spined stickleback (Gasterosteus aculeatus) were resident species using the tributary as a spawning, nursery and adult habitat; (ii) Bream (Abramis brama), Roach (Rutilus rutilus), Rudd (R. erythrophthalmus), Tench (Tinca tinca), and Pike (Esox lucius) were migratory species, using the tributary as a spawning area, as well as a nursery habitat during their first year of growth, but migrating towards the river Meuse typically at a length of 5–15 cm; and (iii) Bleak (Alburnus alburnus), Sunbleak (Leucaspius delineatus), Carp (Cyprinus carpio), Crucian carp (Carassius carassius), and Perch (Perca _,fluviatilis) were transient species, characterized by an absence of reproduction, ^.and the occurrence in very low densities of >age-1 juveniles and adults only. Lowland tributaries, such as the Everlose Beek, can contribute to the recruitment of particularly migrant species, hence contributing to fish populations of the regulated river Meuse.