A test of a model for planktivorous filter feeding by bream Abramis brama

Synopsis The planktivorous feeding of bream, Abramis brama on Daphnia hyalina and Bosmina coregoni was analyzed in a stepwise regression analysis with the average size (and standard deviation) of consumed organisms as dependent variable and the size of the fish, the average size (and standard deviation) of the organisms and their density in the environment as independent variables. Three basic predictions on filter feeding were formulated and tested. It was predicted that the (average) prey size should increase with fish size, but that the standard deviation should decline. Secondly the prey size should be strongly correlated with the prey size available and thirdly the prey density should have little effect on the size selection. These hypotheses could not be rejected for bream>10 cm feeding on B. coregoni and for bream>20 cm feeding on D. hyalina. The hypotheses were not valid for smaller bream as these acted as particulate or combined filter- and particulate feeders.     

Structure,development and function of the branchial sieve of the common bream,Abramis brama,white bream,Blicca bjoerkna and roach,Rutilus rutilus

Synopsis The filter feeding organ of cyprinid fishes is the branchial sieve, which consists of a mesh formed by gill rakers and tiny channels on the gill arches. In order to establish its possible role during growth we measured the following morphological gill raker parameters over a range of sizes in three cyprinid fishes, bream, white bream and roach: inter raker distance, bony raker length, raker width, cushion length and channel width. At any given standard length common bream has the largest inter raker distance, roach the lowest and white bream is intermediate. In the comb model of filter feeding the inter raker distance is considered to be a direct measure of the mesh size and retention ability (= minimal size of prey that can be retained) of a filter. For the three species under study there is a conflict between the comb model and experimental data on particle retention. Lammens et al. (1987) found that common bream has a large retention ability whereas roach and white bream have a much smaller one. A new model, the channel model (Hoogenboezem et al. 1991) has been developed for common bream; in this model the lateral gill rakers can regulate the mesh size of the medial channels on the other side of the gill slit. The present data indicate that this model is not appropriate for white bream and roach. At any given standard length white bream and roach only reach 70% of the raker length of common bream, which means that in this model the gill slits should to be very narrow during filter feeding. The gill rakers consist of a bony raker and a fleshy cushion. The bony rakers have a rather long needle-like part outside the cushion in bream, but not in white bream and roach which have blunt gill rakers. Blunt gill rakers are not suited to reduce the diameter of the medial channels. The comb model seems more appropriate for white bream and roach, but doubts about the validity of this simple model remain. The sum of the areas of the medial channels is an approximation of the area through which water flows in the filter. This channel area therefore gives an impression of the capacity or flow rate of the filter. With this capacity estimation and an estimation of energy consumption we calculated an energy ratio of filter feeding. The energy ratio decreases with increasing standard length with an exponent close to the expected exponent of -0.40. The energy ratio is highest in bream, intermediate in white bream and lowest in roach.     

X-ray measurements of gill-arch movements in filter-feeding bream, Abramis brama (Cyprinidae)

The technique of X-ray cinematography was used to study pharyngeal movements in Abramis brama (L.). The theoretical and practical problems in X-ray cinematography of feeding fish are discussed, as well as criteria for the selection of images suited for detailed measurements.
Respiration and filter-feeding on Daphnia pulex (length c . 1 mm) show different gill arch movement patterns in bream. Slits between gill-arches are kept smaller during filter-feeding. In addition, during filter-feeding, this inter-arch distance decreases considerably in a posterior direction. The hypothesis that particle retention occurs on the slits formed between adjacent gillarches and their gill-rakers is not supported by the present results.     

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.     

A molecular approach to detect hybridization between bream Abramis brama, roach Rutlius rutilus and rudd Scardinius erythrophthalmus

Hybridization between roach Rutilus rutilus , bream Abramis brama and rudd Scardinius erythrophthalmus was investigated using morphological and genetic analysis employing both nuclear (ITS1) and mitochondrial (cytochrome b ) markers. Allele-specific amplification (ASA) reactions for both markers were developed and ITS1 sequence data for all three species are presented. Sequencing detected two ITS1 haplotypes within both roach and bream which most likely evolved in isolation and were subsequently brought together as a result of restocking by anglers. Analysis of cloned hybrid nuclear ribosomal DNA revealed evidence of recombination between parental ITS1 sequences. ASA proved to be an effective method for identifying hybrids and detected multiple ITS1 copies in fishes identified as purebred by morphological analysis. In addition this suggests post-F1 hybridization and introgression may be occurring between roach and bream, and rudd and bream, although some barriers appear to be suppressing backcrosses within the hybrid population. Analysis of the hybrid population demonstrated that hybridization has occurred in both directions.     

Mechanism of hybridization between bream Abramis brama and roach Rutilus rutilus in their native range

Mechanisms of hybridization between bream Abramis brama and roach Rutilus rutilus were studied within the native range of the species in a lake in southern Finland. Through the genetic analysis of A. brama, R. rutilus and putative hybrids, hybridization is shown to have occurred between female A. brama and male R. rutilus. These results match with previous findings from introduced habitats, suggesting that mating between female A. brama and male R. rutilus is the predominant mechanism through which the two species hybridize.     

On the biology of bream, Abramis brama (L.) in Lake Peipsi in 1994

The population of bream in L. Peipsi was studied with respect to age, growth rate, condition factor (according to Fulton) and length-weight relationship in 1994. That autumn the bream population in L. Peipsi consisted of fishes aged from 0+ to 15+. During the first year bream reached an average body length of 7.9 cm (the commercial legal size (30 cm) was usually attained by the end of the 5th–6th year. The condition of bream in this lake was above the average of Estonian lakes. The relatively good growth rate and condition of bream in the lake indicates that the waterbody is appropriate for this fish.     

A note on the growth-rate and year-class strength of bream, Abramis brama (L.), in three eutrophic lakes, England

In this study some comparative observations on the growth-rate and year-class strength of bream, Abramis brama , in three Shropshire-Cheshire meres are given. All populations are exposed to variable recruitment. The occurrence of four strong year-classes (1959, 1966, 1969,1973) suggests that climate is an important factor influencing spawning success. Water temperatures ≥16°C in July and August may be particularly important. All other intervening year-classes are absent. The growth-rate of bream in Tatton Mere and Ellesmere Mere is good ( L ∞= 541–561 mm) but comparatively poor ( L ∞= 448 mm) in Cole Mere. The significance of population density, food supply and parasitic infestation by Ligula intestinalis is discussed.     

The combined use of acoustic tracking and echosounding to investigate the movement and distribution of common bream (Abramis brama) in the River Trent,England

Spatial behaviour and distribution of fishes along a 7.6-km lowland reach of the River Trent, England, were examined using two complementary telemetry techniques: acoustic tracking to assess the movement and activity of common bream Abramis brama (L.) and quantitative echosounding for measuring the density and distribution of fish shoals. Nine adult bream (39.3–53.2 cm) were tracked by means of intraperitoneally implanted acoustic transmitters from 19 July to 12 September 2000. Home range size varied between 0.35 and 5.40 km of river length over this period. Bream were relatively inactive during daylight hours, began moving near dusk, and tended to move throughout the night. A distinct daytime residence area was occupied by most tagged fish on most occasions, while river use at night was more variable between individuals. Mobile echosounding surveys, with the transducer beaming horizontally across the river, conducted at night between July and September 2000, showed a highly contagious fish distribution within the study reach. For 200-m sections of river, there was a negative correlation between the relative frequency of acoustic tracking fixes at night and mean fish densities, as measured by echosounding for targets larger than –50 dB (c. 5-cm long). However, there was a highly significant positive rank correlation between the relative frequency of acoustic tracking fixes and acoustic targets larger than –30 dB (c. 22-cm long), most of which in this river are bream. This suggests that telemetry and echosounding can, in this part of the River Trent, be combined to provide valuable spatial information at individual and population scales for bream.     

Influence of temperature during four following spawning seasons on the spawning effectiveness of common bream,Abramis brama (L.) under natural and controlled conditions

The common bream, Abramis brama (L.) in Kortowskie Lake (north-eastern Poland) usually spawn when the water temperature during the late spring rises to 20 °C. The optimal water temperature for embryonic development of this population is 21 °C. However, in some cases, the temperatures of the spawning grounds during bream spawning are much higher, becoming semi-lethal or even lethal for bream embryos. The aim of the study was to investigate the natural and artificial spawning effectiveness of bream during a 4-year study regarding the reproductive effectiveness of the wild bream population in relation to thermal fluctuation (optimal and semi-lethal) of their ecosystem during the natural spawning season. During four following seasons, the bream spawners, as well as the eggs, were collected from the spawning grounds and incubated at optimal (21 °C) and semi-lethal (23 °C) temperatures. The spawning of mature bream was artificially induced and the obtained eggs were also incubated at the same temperatures. The period of observed spawners on the spawning grounds was different in different years: the longest time of bream spawning was in the second year of the study and the shortest was during the third year of the study. In the last year, a decrease in water temperature caused a break in the spawning. Thermal changes in water temperature during the spawning season may have caused a high mortality level of bream embryos and decreased the recruitment of the next species generation.     

Growth,condition and gonad development of bream (Abramis brama L.) in relation to its feeding conditions in Tjeukemeer

The bream (Abramis brama L.) population of Tjeukemeer was studied for three successive years. The growth, condition, gonad development, diet and feeding conditions of the fish are described. Food competition for two years with the then abundant young planktivorous smelt (Osmerus eperlanus) and perch (Perca fluviatilis) resulted in a decreased growth rate, condition and gonad development of the larger bream. The biomass of chironomids was too small in relation to that of the zooplankton to be important for the bream population, although they were eaten more efficiently.     

Aspects of the ecology of bream, Abramis brama (L.), in a gravel pit lake and the effects of reducing the population density

The growth of bream, Abrumis brumu (L.), in a gravel pit lake was considered to be good in 1982/1983 (L_x=663cm, K=0.105). Theadult breampopulationwasdominated by the 1973and 1976 year-classes. These year classes still formed most of the spawning population in 1987, but had grown very little (<2 cm) in the previous 5 years. In November 1987, 158 kg ha⁻¹ of bream were removed from this lake and in I988 the remaining bream population showed an increase in growth (mean length by 2.7 cm and mean weight by 0.5 kg) and condition (1.87 in 1987 to 2.09 in 1988) in one growing season. This additional growth of an ageing stunted bream population is considered to be the result of an increased food supply after reducing the fish density.     

The biology of bream, Abramis brama (L), and its natural hybrid with roach, Rutilus rutilus (L), in the River Exe

Hybrids between bream, Abramis brama , and roach, Rutilus rutilus , occur in the lower reaches of the River Exe and were positively identified by their meristic features and shape of the pharyngeal bone. The growth of bream and hybrids was determined by back-calculation from scales. Annual checks were laid down in early June. The mean length for age of female bream was significantly larger than that of males for fish 6 years of age and older. This divergence in growth rate was associated with the sexual maturation of the fish. Data for the sexes were combined and compared with the growth rate of hybrids and roach from the same region. Hybrid growth was similar to that of bream for the first 6 years of life but was intermediate between that of the two parent species in the older age groups. Some hybrids with developing gonads were found. A change in the diet of bream from planktonic feeding to a benthophagic habit with age was noted. Detritus, substrate and chironomid larvae formed the bulk of the diet of hybrids.     

The spatial structure and interrelation of plerocercoids of Digramma interrupta (Cestoda, Ligulidae) and the bream (Abramis brama) in the Kuibyshev reservoir

The character of the distribution of the plerocercoid D. interrupta in the bream Abramis brama from the Kuibyshev water reservoir was studied. The spread of the parasites in A. brama population is of complex character and changes with the increase of fish body length. The factors affecting the maintenance and regulation of the relationships in the host-parasite system (size composition of fishes, peculiarities of the host's genotype, values of occurrence of different numbers of the parasites, variability of plerocercoids) are discussed.     

Migration and spawning energetics of the anadromous sea lamprey,Petromyzon marinus

Synopsis Energy expended in migration and reproduction was determined from measurements of caloric concentration and body and gonodal weight for nontrophic sea lampreys collected from different sites along the St. John River, New Brunswick. The estimated cost of locomotion in swimming the 140 km which separates the estuary from the spawning redds was 300 and 260 kcal for males and females respectively. Acutal distance which lampreys swam as well as mean swimming speed were estimated from a linear regression equation relating energy expenditure for locomotion and body weight. Energy expenditure for breeding was considerably greater than that catabolized throughout the upstream migration.     

Swimming efficiency and the influence of morphology on swimming costs in fishes

Swimming performance is considered a main character determining survival in many aquatic animals. Body morphology highly influences the energetic costs and efficiency of swimming and sets general limits on a species capacity to use habitats and foods. For two cyprinid fishes with different morphological characteristics, carp (Cyprinus carpio L.) and roach (Rutilus rutilus (L.)), optimum swimming speeds (U _mc) as well as total and net costs of transport (COT, NCOT) were determined to evaluate differences in their swimming efficiency. Costs of transport and optimum speeds proved to be allometric functions of fish mass. NCOT was higher but U _mc was lower in carp, indicating a lower swimming efficiency compared to roach. The differences in swimming costs are attributed to the different ecological demands of the species and could partly be explained by their morphological characteristics. Body fineness ratios were used to quantify the influence of body shape on activity costs. This factor proved to be significantly different between the species, indicating a better streamlining in roach with values closer to the optimum body form for efficient swimming. Net swimming costs were directly related to fish morphology.     

Derivation of dynamic reference values for the classification of contaminant concentrations in bream (Abramis brama) of German rivers and lakes using data of the Environmental Specimen Bank

A direct assessment of contaminant concentrations in biota with respect to their biological relevance or importance for the ecosystem is rarely possible. Statistically derived reference values can serve as a guide to classify measured tissue concentrations, but they do not provide any information on the biological significance of the contaminant concentrations. However, previously such reference values did not exist for environmental-biomonitoring. Based on analytical data from muscle tissue of bream (Abramis brama) of the German Environmental Specimen Bank (ESB), we present a method on how to derive dynamic reference values. These show the general state of inland surface water pollution in Germany at a certain time. The reference values allow for classification of measured contaminant concentrations in muscle tissue of bream. This classification enables a comparative assessment in means of how the actual state of pollution in a specific ecosystem is, compared to the general, macro state of pollution.     

Diet composition and prey preference of tench, Tinca tinca (L.), common bream, Abramis brama (L.), perch, Perca fluviatilis L. and roach, Rutilus rutilus (L.), in two contrasting gravel pit lakes: potential trophic overlap with wildfowl

The abundance of benthic macroinvertebrate taxa and the relative abundance of zooplankton taxa were compared with the diet of bream, tench. perch and roach from two gravel pit lakes during May-July 1986 and 1987. Significant food preferences were demonstrated between species and between lakes. Chironomid pupae dominated the macroinvertebrate diet of perch, roach, ate predominantly either Spirogyra sp. (St Peters Lake) or Daphniu hyalina (Main Lake).
The Main Lake, bream fed largely upon chironomid larvae and the bivalve Sphuerium but in St Peters Lake they positively selected a variety of less abundant benthic invertebrate taxa. Bream switched from benthos to zooplankton in the Main Lake in 1986. Tench ate large numbers of Aselhs and showed positive selection of various macroinvertebrate prey in St Peters but ate D. hjulim in Main Lake. Tropic overlap for chironomids and other macroinvertebrate prey was demonstrated between perch, bream and tench, and potentially with wildfowl which used the gravel pits for breeding and wintering.