Interactions between the roach,Rutilus rutilus,and waterfowl populations of Lough Neagh,Northern Ireland

Synopsis Following the introduction of roach, Rutilus rutilus, to a large eutrophic lake in ca. 1973, a subsequent increase in the abundance of this cyprinid through the 1970s was accompanied by a decline in the numbers of one of the lake&s most abundant overwintering waterfowl, the tufted duck, Aythya fuligula, and an increase in overwintering piscivorous great crested grebes, Podiceps cristatus. We suggest that these contrasting trends are causally related and that competition for benthos and increased prey availability are the mechanisms responsible for the changes in the tufted duck and grebe populations respectively. In agreement with these hypotheses, a reduction in the roach population during the mid 1980s was accompanied by a recovery of tufted ducks and a decline of grebes.     

Size-dependent over-winter mortality of young-of-the-year roach, Rutilus rutilus

Over-winter survival of starved and fed young-of-the-year roach from two lakes in central Finland was examined in the laboratory between November 1992 and May 1993. The mortality rate of starving YOY roach (total length 38 ± 2 mm) from small (ca. 0.5 km²), eutrophic Lake Isojärvi was 50%, whilst roach (total length 32 ± 3 mm) from large Lake Päijänne (1106 km²) suffered 42% mortality. Mortality was size-dependent among roach from Lake Isojärvi, smaller individuals being more vulnerable. There was not strict size limit for survival as proposed previously. However, it seems that within populations approximately the same proportion of smallest roach died independent of the absolute lengths of the fish. Mortality of fed roach from both lakes was always < 5%. This good survival indicates indirectly the importance of energy reserves in wintering. Lipid and protein content of fasting roach from lake Isojärvi decreased during the winter. In the group of fasting roach from Lake Päijänne the amount of lipids stored increased between November and March and decreased thereafter. No change in protein content of fasting fish from Lake Päijänne was observed.     

The decline of a roach Rutilus rutilus (L.) population in Chew Valley Lake

A series of nettings for roach in Chew Valley Lake carried out by members of the Zoology Department, Bristol University, has revealed a marked decline in the population between 1965 and 1968. Fish from the main Lake were found to be heavily parasitized with Ligula intestinalis (L.) while those from the inflow pool (Herriott's Pool) were practically free from infection. It is considered that the decline of the roach can be linked to the incidence of Ligula , but that clean fish from the inflow pool may provide breeding stock and maintain the production of fry, which serve as food for the trout.     

Resource partitioning of roach Rutilus rutilus and bleak Alburnus alburnus in two eutrophic lakes in SE Norway

In this paper I investigate the resource partitioning of roach Rutilus rutilus and bleak Alburnus alburnus in two eutrophic lakes in SE Norway. Zooplankton was the preferred food item for both species during summer, whereas blue-green algae dominated the diet in September/October. There was no diet overlap in May, with the roach feeding mainly on detritus and the bleak feeding on surface insects. During summer the diet overlap increased, reaching high values in autumn. Habitat overlap was close to unity in spring and early summer. Coinciding with increasing diet overlap during summer and autumn the overlap in habitat decreased.     

Factors affecting prey selection by young bream Abramis brama and roach Rutilus rutilus: insights provided by parallel studies in laboratory and field

Synopsis Prey selection by underyearling bream and roach was studied in both the laboratory and field. When presented with cladoceran and a more elusive copepod prey both fish species select against copepods, regardless of the relative prey sizes. However, the field diet of bream, but not roach, consistently includes a large proportion of copepods. The explanation for this discrepancy lies in the timing and location of foraging in the field. Bream foraging, unlike that of roach, is largely restricted to the hours of darkness and to the lowest stratum of the lake. The Microcrustacea of this stratum is depleted of cladocerans at night, because of vertical migration, and is relatively rich in copepods.     

Reproductive disturbance in a roach (Rutilus rutilus) population affected by cooling water discharge

To analyse a recruitment failure in a roach ( Rutilus rutilus ) population exposed to cooling water from a Swedish nuclear power plant, histopathological examinations were made on female gonads. Several disorders were documented, corresponding to effects previously seen in Lithuanian, Moldavian and Russian heated waters, The relative gonad size (GSI) was generally lower in the exposed population. Oocyte degeneration was observed in about 50% of the females, potentially seriously reducing their reproductive capacity. The gameto- and gonadogeneses also were clearly affected and generally occurred at a faster rate. Sexual maturity was earlier and was accompanied by an increased occurrence of asynchionic gonad and oocyte growth. A normal gonad development should pass through different stages, coupled to the seasons, and the difference between individuals in a population should be small. However, in some exposed fish, the sequence of seasonal development was disturbed and a simultaneous, intensive, growth of sex cells in different stages of development could be seen. An increase of variation in gonad development both within, as well as between, fish thus was documented. Conclusively, the histopathological analysis provided evidence that the observed recruitment deficit could be related to gonad failure.     

Loss of genetic variability in reintroduced roach (Rutilus rutilus) populations

Genetic variation at five microsatellite loci and in mtDNA was surveyed in reintroduced and 'control' populations of roach ( Rutilus rutilus ) in Sweden. Microsatellite allelic richness and allele size ranges were significantly reduced in reintroduced populations, and mtDNA diversity was nearly significantly reduced in reintroduced populations. These measures of genetic variability were strongly correlated with lake characteristics that influence population size and food availability.     

Histochemical characterization of myotomal muscle in the roach, Rutilus rutilus (L.)

A histochemical study of the myotomal muscles in the roach revealed three main muscle regions: red, intermediate and white. These were distinguished on the basis of glycogen content, succinate dehydrogenase (SDH), and myofibrillar ATPase (mATPase) activity. Except for the red fibre region, none of these described regions is homogeneous. The principal new findings are the toniclike fibre, the presence of a transitional zone with two fibre types, and the mosaic organization of the white fibre region. The significance of this type of myotome architecture in relation to the locomotion of the species is discussed.     

Satiation-dependent, intra-cohort variations in prey size selection of young roach (Rutilus rutilus)

The tolerance to freezing and thawing of Leucodon sciuroides, a moss growing in mountainous areas of the Mediterranean (south-east Spain), was investigated by means of CO₂ gas exchange, modulated chlorophyll (Chl) a fluorescence and pigment analysis by high-performance liquid chromatography. Evidence is presented for freezing-induced decreases in CO₂ fixation that enhance non-radiative dissipation of absorbed light energy, a process which protects the photosynthetic apparatus. The photosynthetic apparatus of L. sciuroides remained fully recuperable after freezing, as indicated by the recovery of photosynthetic CO₂ fixation and Chl fluorescence parameters to pre-freezing values during thawing. The rapid recovery of photosynthesis activity during thawing in L. sciuroides suggests that this moss is capable of tolerating freeze-thaw cycles in a manner similar to that found at higher latitudes or in the Antarctic. The resistance of the photosynthetic apparatus of this moss to freezing might be achieved, at least partially, through the employment of dissipative pathways, such as non-radiative dissipation of absorbed light energy. Received: 4 June 1998 / Accepted: 15 February 1999     

Predator-induced respiratory responses in juveniles of vendace Coregonus albula, whitefish C. lavaretus, perch Perca fluviatilis and roach Rutilus rutilus

Predator-induced respiratory responses of juvenile vendace, whitefish, perch and roach were studied in an intermittent-flow respirometer by creating visual contact between test fishes and predators (juvenile northern pike). Vendace and whitefish always responded to the presence of pike with increased oxygen consumption. The response of perch was the opposite: oxygen consumption decreased to near the standard respiratory level. Roach responded more variably: some individuals increased their oxygen uptake while others decreased it. Changes in the rate of respiration during exposure to predation are supposed to be caused by the differences in locomotory activity due to induced antipredator behaviour. According to their responses, these species could be grouped into escapers (coregonids), hiders (perch) or indeterminates (roach). The species-specific differences in the antipredator behaviour originate in morphological and physiological characteristics which together determine the effectiveness of a particular antipredator style (i.e. either hiding or escaping).     

Effect of starvation and refeeding on digestive enzyme activities in juvenile roach, Rutilus rutilus caspicus

We evaluated the effects of starvation and refeeding on digestive enzyme activities in juvenile roach, Rutilus rutilus caspicus. Fish were divided into four feeding groups (mean mass 1.68 ± 0.12 g). The control group was fed to satiation twice a day throughout the experiment with formulated diet (SFK). The other three groups were deprived of feed for 1(S1), 2(S2), and 3(S3) weeks, respectively, and then fed to satiation during the refeeding period. The results showed that trypsin specific activity was not affected significantly either by starvation or refeeding, in all experimental groups. Chymotrypsin specific activity did not change significantly in S1 fish during the experimental period. In S2 and S3 fish no significant changes were observed during the starvation period. Upon refeeding, the activity increased in S2 fish, while it decreased in S3 fish. Amylase specific activity decreased significantly during the starvation period in all experimental groups. Upon refeeding, the activity increased. Alkaline phosphatase specific activity did not change significantly during the experiment period in S3 fish, while it showed significant changes during the starvation and refeeding period in the S1 and S2 fish. Starvation also had a significant effect on the structure of the intestine.     

The morphology and histology of the pineal organ in roach, Rutilus rutilus (L.)

The pineal organ in the roach, Rutilus rutilus (L.), is covered by a semi-transparent area, the pineal window. Beneath this the pineal is attached to a long robust stalk, lying just under the parietal bone. The pineal is attached to the brain through the dorsal sac. Three cell types have been identified histologically. These are the sensory cells, supporting cells and the ganglia cells. The inner segment of the sensory cells respond to PAS and AF staining, while the remaining cells respond to Orange G, LG, or Acid Fuchsin. The evidence suggests that the roach pineal may have a dual photosensory and glandular function.     

Consumption, growth and respiration of bleak, Alburnus alburnus (L.), and roach, Rutilus rutilus (L.), during early ontogeny

Three components of the energy budget, consumption ( C ), production ( P ) and respiration ( R ) in juvenile roach and bleak kept under controlled food ( Anemia salina , 2400 ind. l⁻¹) and temperature (20° C) conditions were measured in a study aimed at defining differences between the two species and elucidating the patterns of energy partitioning during ontogeny.
Daily food consumption rates (J day⁻¹ fish⁻¹) increased allometrically ( C =a W ^b) with body size ( W , mg dry weight) in both species. Covariance analysis indicated no differences in slope or intercept for the two regression lines ( P ≤ 0.05, n = 82). However, the two species grew at significantly different rates, roach faster than bleak.
The dependence of the respiration rate (μmol h⁻¹ fish ⁻¹) on body weight ( W ) can be described by an allometric function: R = a W ^b, where a ± 95% C.L. = 0.17 ± 0.15 for roach and 0.18 ± 0.20 for bleak. The slope for roach (b ± 95% C.L. = 0.78 ± 0.01) is slightly higher than that for bleak (0.69 ± 0.03).
Assimilation efficiency [AE = ( P + R ) C ⁻¹] was significantly higher in roach than in bleak. Different levels of AE correlated with differences in relative gut length (gut length as percentage of body length). Due to the shorter relative gut length above a weight of 5 mg, bleak has lower powers of digestion, which may explain lower production rates. These differences in energetic performance between the two species indicate mechanisms leading to niche differentiation in the early life history of the fishes.     

Myxosporea parasites in roach, Rutilus rutilus (Linnaeus), from four lakes in central Finland

Ten myxosporean species belonging to three families were found in roach, Rutilus rutilus (Linnaeus), obtained in 1985 and 1986 from four lakes in central Finland which are connected to each other, but differ in water quality. One of the lakes is polluted by paper and pulp mill effluent, two are eutrophic and one is oligotrophic and still in its natural state. Eight species were found in all the lakes. The most common species were Myxidium rhodei Léger, 1905, Myxobolus muelleri Bütschli, 1882 and Myxobolus pseudodispar Gorbunova, 1936 with prevalences varying between 66–80, 16–31 and 32–59%, respectively, in the four lakes. The largest difference in myxosporean prevalence between lakes was found in the case of M. pseudodispar infection, which was highly significantly lower in the polluted lake. The locations of the myxosporean species in the tissues of the fish were found to be species-specific. M. rhodei and M. muelleri being prevalent in the kidney and M. pseudodispar in the muscles.
No clear seasonal variation was found but a tendency for a decrease in infection with increasing age was recorded in the case of M. rhodei and M. pseudodispar .     

Biochemical changes in the lateral muscles of roach, Rutilus rutilus from two habitats following exercise

Batches of roach from two contrasting habitats were exercised in a flume at various water velocities for 1 h, and muscle metabolite levels were determined. It was found that the percentage change in lactate was greater in fish from the still water habitat than that in their running water counterparts, and it is proposed that natural conditioning of fish to water flow may be one of the main factors responsible.     

A qualitative and quantitative description of the early growth of roach,Rutilus rutilus,in the laboratory

Environmental Biology of Fishes - Eggs from a wild roach were artificially fertilized and then incubated on small pieces of nylon netting in flowing and aerated water. After hatching, the young...     

The occurrence and natural alleviation of stunting in a population of roach, Rutilus rutilus (L.)

Two sudden and pronounced changes in the growth rate of roach, Rutilus rutilus (L.), in Slapton Ley, Devon, have been observed between 1972 and 1976. At first the growth rate declined to the point at which the population became stunted, then subsequently it improved again. These changes were correlated with population density; the numbers of roach were increasing during the late 1960's/early 1970's, and this increase was substantially reinforced by very strong year classes in 1972, and, to a lesser extent, in 1973. The increase in population density resulting from the strong 1972 year class was apparently adequate to accelerate the onset of the stunting observed. The improvement in growth rate in 1976 followed immediately after extensive mortalities amongst the roach during 1975, caused by an epidemic of the parasite Ligula intestinal is (L.). Some improvement in the growth of O group roach had been evident during 1975, but this was not observed in the population. Ford-Walford plots showed a decline in the value of L after the onset of stunting in 1972.
Differences in the reproductive biology of the fish were found following the alleviation of stunting; the gonads of both sexes achieved a greater relative weight, and correspondingly the fecundity of the females was higher, although this latter effect became progressively less marked with increasing size. It was not apparent amongst the largest individuals. There was also some evidence of a decline in the proportion of fish maturing at minimum size. The changes in the reproductive biology were associated with the improvement in conditions for individual fish following the decline in population density.