Population responses of perch (Perca fluviatilis) and roach (Rutilus rutilus) to recovery from acidification in small Finnish lakes

Decreasing trends in atmospheric emissions and acidic deposition during the 1990s have resulted in chemical recovery from acidification in the sensitive surface water systems of southern Finland. Responses of perch and roach populations to the improved water quality were studied in 30 small lakes with the aid of water chemistry monitoring data gathered in 1987–2002 and the data collected from two consecutive periods of gillnet test fishing, 1985–1988 and 2001–2002. In the most acidified lakes, alkalinity and ANC have increased and sulphate and labile aluminium concentrations decreasæed markedly. The response of perch populations to the improved water quality is seen in improved reproduction success, indicated by a higher CPUE in numbers and a lower mean weight. The growth rate of perch has declined as the population density has increased. Roach populations have not recovered in the same way as perch, there being no major changes in NPUE or mean weight. Lower growth rates were, however, observed in the roach populations of all study lakes. The increased perch population density as an obstacle to the recovery of roach populations is discussed. Despite the chemical and biological recovery of the study lakes, the buffer capacity of many headwater lakes is low and the lakes will be sensitive to any increases in acidic deposition in the future.     

Ergasilid copepods as parasites of perch Perca fluviatilis and roach Rutilus rutilus in Central Finland: seasonality, maturity and environmental influence

A total of 1255 roach Rutilus rutilus (L.) and 866 perch Perca fluviatilis (L.) from four interconnected lakes in Central Finland differing in trophic status and pollution level were studied for parasitic ergasilid copepods between August 1985 and December 1988. In addition, 109 whitefish ( Coregonus sp.) were studied from one of the lakes.
Four ergasilid species were found: (the prevalence and intensity/fish, respectively, for the whole material are given in parentheses) Ergasilus briani (16·9%, 0·5), Neoergasilus japonicus (15·6%, 0·4) and Paraergasilus longidigitus (2·1%, 0·02) on the roach and Ergasilus sieboldi (9·9%, 0·1) and P. longidigitus (4·9%, 0·05) on the perch. Logit analysis was used to assess the significance of the year, the lake and the season for the prevalence of infection. Generally, the prevalence of E. briani on roach depended on the season only, with higher prevalences in summer. That of E. sieboldi on perch was mainly dependent on the lake, being most frequent in the oligotrophic lake. Both lake, year and season affected the prevalence of N. japonicus in roach. The more complicated system for N. japonicus was explained by the long duration of its free-living stage, its loose attachment and different location on the host, being found on the fins whereas E. briani and E. sieboldi were on the gills.
All species were found throughout the year, and age had no clear influence on infection. The occurrence of egg-sacs and length distributions of the copepods suggest that there are two generations a year, e.g. an overwintering E. briani generation which produces offspring in June to attack the fish in July, and a second generation which attacks the fish from August onwards. Whitefish were not infected by these parasites, only one fish being found which carried a single individual of E. sieboldi.     

Habitat use and growth of age-0 whitefish,Coregonus lavaretus,and cisco,C. albula

Synopsis Local American eel stocks were studied by mark-recapture methods along 600m of tidal creeks in Great Sippewisset Marsh, Falmouth, Massachusetts, during summer 1979. The estimated stock density was 350 eels, equivalent to 875 fish ha^-1, and movement of individual American eels over the five week study was usually less than 100 m. Large American eels were found to predominate in the wide marsh creeks whereas smaller American eels predominated in narrower creeks at the landward side of the marsh. Territoriality is suggested as a mechanism for maintaining differences in distribution of size classes and a limited home range.Senior author     

Acute effects on perch (Perca fluviatilis) and long-term effects on whitefish (Coregonus lavaretus pallasi) of liming of an acidified lake

The acute effects on perch and long‐term effects on whitefish were studied after liming one side of a lake [initial pH: 4.6–5.5; aluminium (Al): 29–54 μg L^?1; Ca²⁺: 0.02–0.07 mmol L^?1] that was divided into two parts with a plastic curtain. Some Al precipitation was observed on the gill surface of perch 1 day after liming; the concentration of plasma sodium of perch females in the limed side was also higher than in the acidic side. Nearly 6 months after liming, at the spawning time of whitefish, the plasma chloride concentration of whitefish in the limed side was higher and blood glucose concentration lower than in the acidic side. Four of five whitefish males from the limed side, but only one of five males and none of the five females from the acidic side, were ready to spawn. The growth of whitefish in the limed side was also more rapid. These changes illustrate that liming had no acute harmful effects on perch, and allowed whitefish to recover from acidity‐related physiological stress.     

Comparative study of bile-acid composition in the bile of the European vendace Coregonus albula L. and whitefish Coregonus lavaretus L. under conditions of technogenic water pollution

Changes of the bile acid composition were studied in bile of the vendace Coregonus albula L. and the whitefish Coregonus lavaretus L. under effect of sewers of an ore mining and processing plant, the main pollutin agents of the sewers being heavy metals. The revealed variability of the bile acid composition indicates different species-related sensitivity to the studied pollutants as well as a lower resistance of males as compared with females to this type of pollution. Mechanisms of effects of industrial sewers on the bile formation processes and a possibility of using parameters of the steroid lipid metabolism at evaluation of the state of water ecosystems are discussed.     

The influence of simulated aquatic macrophytes on the zooplankton consumption rate of juvenile roach, Rutilus rutilus, rudd, Scardinius erythrophthalmus, and perch, Perca fluviatilis

Laboratory experiments showed that, of zooplanktivorous roach, rudd and perch, in the absence of any environmental structure roach were the most efficient feeders, but high densities of simulated submerged marcrophytes elevated perch to this position; rudd matched the performances of perch and roach only at intermediate structure densities. These changes in efficiency rankings with increased structure were the result of overall decreases in the performances of roach and rudd. Simulated water lilies and emergent reeds had their own influences on consumption rate. These effects were largely mediated through relationships between structure density and swimming speed; roach and rudd, not perch, showed reduced swimming speeds in the more structured environments. Observations of the routine behaviour of the fish suggest that their assessment of predation risk may be an important factor in determining their activity level and hence foraging strategy.     

A survey of the spawning of perch (Perca fluviatilis), pike (Esox lucius), and roach (Rutilus rutilus), using artificial spawning substrates in lakes

The development of spawning in perch, pike and roach in Lake Geneva has been studied by means of artificial spawning substrates, laid at different depths, from 1984 to 1993. In Lake Geneva, perch spawned in May. A rise of surface water temperature up to 14 °C stimulated spawning activity while bad weather (surface temperature at 10 °C) induced a spread of the spawning period over more than one month. The spawning period was delayed in years when the mean width of perch egg-ribbons was the largest; this corresponded to the biggest females. At the beginning of the spawning period (early in May), perch preferentially chose a depth of 4 m to spawn. In contrast, at the end of the spawning period, maximum spawning intensity was observed at a depth of 12 m. This phenomenon was more pronounced when water temperature rose above 14 °C in the top 4 m while it remained below 12 °C at a depth of 12 m. Pike spawned at the end of April and at the beginning of May in Lake Geneva. They preferred spruce branches among the different spawning substrates that we tested in Lake Vouglans. When the water temperature increased at the surface of Lake Geneva, pike preferred to lay their eggs on substrates set at 3 m depth where the temperature was cooler than in the surface layer (10.5 °C vs 14 °C). Roach spawned during the last two weeks of May or during the first two weeks of June in Lake Geneva, depending on water temperature. Spawning had generally been spread over a week, but a sudden decrease of water temperature could slow spawning intensity. Roach were able to lay their eggs on natural or synthetic substrates, located 0.5 m below the surface near the shore as well as, at a distance of several hundred metres from the shore. The survival of eggs was always above 90% for perch and roach and generally above 70% for pike.     

Mass-marking of bone tissue of Coregonus lavaretus L. and its potential application to monitoring the spatio-temporal distribution of larvae,fry and juveniles of lacustrine fishes

Mass labelling techniques have great potential for the study of larval fish dynamics in closed habitats (lakes, ponds and flooded quarries). Different methods of mass labelling of bone tissue were tested: bathing in tetracycline solutions with or without osmotic shock, and modification of otolith microstria by temperature, photoperiod or feeding manipulations using different batches of eggs, eleuteroembryos, larvae and prefed fry of Coregonus lavaretus L. from Lake Leman. A short period of immersion with osmotic shock produced better results than longer bathing (6 to 18 h) in low concentration (400 mg 1^–1) tetracycline solutions. At the eyed stage of eggs when otoliths appear, it is possible to use the immersion technique in a hyperosmotic solution (5 to 12% sodium chloride) with 1% tetracycline (as the Hydrochloride or Oxytetracycline). Optimal immersion times (maximal labelling with minimal mortality) were determined as follows: 10 to 15 minutes for eyed eggs, 3.5 min. for eggs just before hatching and eleuteroembryos, 1.5 min. for prefed larvae and less than 1 min. for fry of more than 20 mm total length. Microscopic examination of otoliths and caudal vertebrae from coregonid larvae and juveniles reared for two years has allowed us to determine the effectiveness and persistence of fluorescent tetracycline makers.     

Downstream displacement and life-history traits of whitefish,Coregonus lavaretus,in a Norwegian river

Synopsis Each year from 1976 to 1985 a part of the freshwater resident whitefish,Coregonus lavaretus, in Liavatn, south-western Norway, was displaced downstreams into the sea. In the sea, they seemed to die within a short period of time. The fish appeared to be flushed downstream by autumn freshets. In age and size, but not sex, the descenders seem representative of the fish in the lake. Females were the predominant sex in the river, whereas the sex ratio did not differ from unity in the lake. Young fish were fast-growing, but the growth rate levelled off at an age of 2 years and an asymptotic length of ∼30 cm. Males matured mainly at age 1+ and females at age 2+. The gonadosomatic index decreased with age, whereas the amount of energy allocated to gonadal tissue relative to somatic tissue increased with age     

Survival, growth and feeding of vendace, Coregonus albula (L.), larvae in net enclosures

Vendace, Coregonus albula (L.), larvae reared in net enclosures anchored in the littoral zone of Lake Ylä-Enonvesi, eastern Finland, were observed for a period of 44 days in order to determine the effects of density on mortality, growth and feeding of the larvae. The ratio of newly-hatched fish to their food was regulated by controlling the number of fish stocked into the enclosures. Prey animals were expected to move freely in and out of the enclosures. The effect of nylon mesh (500 μm) on the penetration of zooplankters into the enclosures was negligible. The influence of possible starvation was determined by analysing the growth of the larvae, their Fulton condition factor, the instantaneous amount of food ingested, and the food composition in their guts. All these indicators were inversely correlated with larval density. Vendace larvae were found to be resistant to mortality from direct starvation. At all densities the survival rate was over 60%. At the time of complete yolk absorption, there was no increase in mortality.     

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.     

Seasonal changes in growth and standard metabolic rate of juvenile perch, Perca fluviatilis L.

The maximum growth rate of juvenile perch, PercaJuviatilis L., at different constant temperatures and in naturally changing day-lengths was studied in the laboratory. Standard metabolic rate was studied in starvation experiments at constant temperatures under short- and long-day conditions. Growth occurred in temperatures above 8 to 10°C. In winter, from mid-October until mid-April, maximal growth was considerably reduced and was relatively slow but constant. The standard metabolic rate was reduced c . 50% under short-day conditions. The seasonal change in metabolic rates, presumably controlled by an endogenous rhythm, was considered to be an adaptation to low food availability during the short winter days.     

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.     

A field experiment on the effects of interspecific competition from roach, Rutilus rutilus (L.), on age at maturity and gonad size in perch, Percafluviatilis L.

The effects of interspecific competition from roach on gonad development in O+ and 1+ perch were studied in a pond experiment by varying the roach density between treatments. The proportion of mature O+ males first increased and, thereafter, decreased with increasing roach density and increasing somatic weight. O f females were immature and all I+ males were mature. The proportion of mature 1+ females decreased with increasing roach density and decreasing somatic weight. The gonad weight of O+ and 1+ males as well as 1+ females decreased with increasing roach density and decreasing somatic weight. For 1+ males, which were individually marked, both start weight as well as somatic end weight were positively related to gonad weight. One possibleexplanation for the hump shaped relationship between the proportion of mature O+ males and somatic weight is that behavioural interactions between O+ and I+ males in the absence of roach affected maturing in O+ males. This study supports previous suggestions that annual variation in resource availability may give rise to variance in fecundity-body size relationships.     

Relationship between annual variation in reservoir conditions and year-class strength of peled (Coregonus peled) and whitefish (C. lavaretus)

We estimated year-class strength (YCS) of whitefish and peled by VPA in two boreal reservoirs Lokka and Porttipahta with mean regulation of water level amplitudes of 2.34 and 2.49 m, respectively. YCS of peled Coregonus peled(Gmelin) was related to winter drawdown most probably via egg desiccation. In the relatively shallow Lokka dissolved oxygen deficiency in late winter also had a negative impact on survival of eggs and year-class strength. In contrast to peled, whitefish Coregonus lavaretus(L.) indicated no significant relationship with winter drawdown or dissolved oxygen level. The obvious reason for the pattern is that peled spawn on the reservoir bottom, but whitefish spawn in the ascending rivers, which are mainly unaffected by reservoir regulation.     

Comparative observations on the growth rate and year class strength of roach Rutilus rutilus L. in two Cheshire lakes, England

In this study some comparative data on the growth rate and year class composition of roach in two Cheshire meres (Rostherne and Tatton) are given. The populations are characterised by year class instability and high growth rates, both of which are most extreme in Tatton Mere. The growth of roach in Tatton Mere is the highest yet recorded from Britain.
The concurrence of two (1969, 1973) strong year classes in both lakes, suggests that climate is an important factor which conditions year class strength. However, although there is some correlation between year class strength and the water temperature index (>14° C) the ultimate cause of year class variability remains obscure. There is no evidence to suggest that year class failure is due to parasitic infestation by Ligula intestinalis or to predation by perch upon roach fry. Year class failure may be due to the mortality of eggs related to the time of spawning. The observed difference in growth rate between the two populations may be attributed to a difference in density caused by the disparity of year class representation in Rostherne Mere and Tatton Mere. However, despite these differences, the net biomass achieved (36–39 kg ha⁻¹) may be similar in both lakes. Superimposed on the effects of density an influence of temperature is noted.     

The population dynamics of pike,Esox lucius,and perch,Perca fluviatilis,in a simple predator-prey system

Synopsis The population dynamics and predator-prey relationship of pike, Esox lucius, and perch, Perca fluviatilis, were examined in simple fish communities in two adjacent shallow lakes, Lochs Kinord and Davan, Deeside, Scotland. Few perch survive to age 3 but Z is low for fish > 3 years and perch live up to 17 years. Population fecundity remained relatively high and constant in perch because of the multi-age spawning stock and the presence of older more fecund perch. Growth rates of perch in both lochs are relatively high as a consequence of low stock abundance. The N, B, and P of adult perch were unusually low. The age range of pike, and N, B, P, and growth were in the range of values reported elsewhere. There was little variation in the strength of pike year classes and the importance of cannibalism and low occurrence of alternative prey in the lochs suggest that the populations were self-regulating. Cannibalism by adults was responsible for most of mortality in perch larvae, and predation by pike and adult perch was responsible for the majority of juvenile losses. This conclusion is supported by the high biomass ratios of pike:juvenile perch of 1.0–30.8. While the number of adult fish was almost equal, the biomass of adult pike was 2–3 × that of perch in Kinord and 6 × in Davan. In L. Kinord, where year class strength was stable, high predation pressure from perch and pike reduced perch abundance rather than eliminated year classes. Perch year classes fluctuated in abundance in L. Davan and were eliminated in the first summer in two sampling years. The pike, and particularly the perch populations, have features characteristic of fish communities in unperturbed ecosystems: namely, a wide range of age classes, stability in biomass with variation dampened by longevity, and low production.     

Effect of body mass and water temperature on the standard metabolic rate of juvenile yellow perch, Perca flavescens (Mitchill)

Fish respiration rates that are presumed to represent standard metabolic rates (SMR) may sometimes include an unspecified energy expenditure associated with activity and digestion. This situation may introduce a bias in bioenergetics models because standard metabolism, digestion, and activity may not be affected by the same environmental conditions. The aim of this study was to (1) develop a SMR model for juvenile yellow perch, Perca flavescens (Mitchill), that represent the minimum energy expenditure required to maintain life and (2) compare the results of this study with published perch metabolic rates and bioenergetics models. SMR was estimated for yellow perch over a range of body␣mass (4.4–24.7 g) and water temperature (12–20°C). The intercept of the relationship between fish respiration and swimming velocity obtained during forced swimming experiments was used to determine SMR. SMR estimated by the present study were comparable to values presented by two published studies on Eurasian perch, Perca fluviatilis L. However, estimated SMR were 4.1–20.9 times lower than values of a third respirometry study and predictions of bioenergetics models for perch. The present study suggests that published SMR models may sometimes include a significant fraction of energy expenditures (39.2–75.9%) associated with digestion and activity. This may complicate the implementation and the interpretation of fish bioenergetics models. The present study indicates that the intercept of respiration-velocity relationships and long-term respiration rates during starvation experiments may provide similar and reliable SMR values.     

Population structure,growth and fecundity of perch (Perca fluviatilis L.) in an acidified river system in Southern Norway

Population structure, density and reproductive potential of perch (Perca fluviatilis L.) from 4 acidified lakes in a river system in Southern Norway were investigated. The upper 3 lakes were most affected by acidification and the number of perch caught per unit effort indicate three-fold increase in density from the upper Gjerstadvann to the lower Brøbørvann. Low density of perch in the upper lakes is explained by; 1) Abnormal mortality occurring in episodes due to acidification, probably caused by aluminium toxicity at pH = 5.2–5.4. 2). Acid water (pH ≤ 5.0) during spawning and development of eggs and larvae, resulting in recruitment failure. Juvenile mortality of perch may depend on the density of the parental stock. In the 3 upper lakes, the density of adult perch probably was too low to produce significant juvenile mortality, and in these lakes the recruitment probably depended more on the May water quality. Improved water quality increases egg hatching and survival and also benefits zooplankton production, the main food for perch during the first summer. Low population density has reduced competition for food and thus improved growth of perch in the 3 upper lakes compared to the lower lake. The perch in Brøbørvann mature at higher age and have lower individual fecundity than perch in Gjerstadvann, an effect of both slower growth and lower length specific fecundity in Brøbørvann. In Gjerstadvann, the perch therefore have a higher reproductive potential relative to the stock density, and may, when the water quality is good enough, give rise to strong year-classes and more frequent year-class fluctuations than perch in the less acid Brøbørvann.     

Interactions between developmental processes,growth, and food selection in the larvae and juveniles of Rutilus rutilus (L.) (Cyprinidae)

Summary The aim of this study was to assess the effects of developmental events, occurring in fish during the first weeks after hatching, on the quantity and quality of the ingested food and on growth. The investigation was carried out with the larvae and juveniles of Rutilus rutilus, the single cyprinid species occurring in an oligotrophic subalpine lake in Tirol, Austria. Comparison between availability of prey in the water and gut contents suggests that the selection of food by the young fish is strongly influenced by developmental processes. For example, the prevalence of indigestible phytoplankton in the gut of young larvae can be taken as a sign of the not yet fully developed sensory and locomotory capacities of the young fish (El-Fiky et al. 1987). Furthermore, quantitative and qualitative changes in the gut contents correlate strongly with changes in the form and relative length of the gut, but reflect only weakly the availability of prey in the water. In the Seefelder See population of R. rutilus the switch from a phytoplankton to a cladoceran dominated diet is accompanied by an increase in relative growth rate by nearly one order of magnitude (Wieser et al. 1988).