Observations on the age, growth, reproduction and food of the roach Rutilus rutilus (L.) in two rivers in southern England

Scales and opercular bones from 632 roach from the River Stour were used for age and back-calculated growth determinations. The scales had clearer inner annuli but operculars clearer outer annuli in fish more than nine years old. The annuli were laid in late May or early June at the beginning of the growth period. Growth was minimal between November and April. Roach from both rivers grow faster than those in most other European waters. Female roach grow faster than males; River Frome roach faster than those from the Stour. Spawning occurred in May and elaboration of gonads between September and May. Immature roach have an annual cycle in condition with a maximum in June and a minimum in early Spring. The condition of mature females is affected by the gonad cycle. The fecundity of Stour roach is represented by the formula: log egg number=4.43 log length (mm)—1.69. Approximately half of the Stour males attained sexual maturity at age III and most of the rest by age IV. Half of the females were mature at age IV and the remainder by age V. Both brood success and growth rate varied from year to year but independently of one another. Most Stour roach ate aquatic insect larvae and molluscs but algae were more frequent in the diet of larger fish.     

Observations on the age, growth, reproduction and food of the dace, Leuciscus leuciscus (L.), in two rivers in southern England

Scales of 497 dace from the river Stour and 573 from the river Frome were used for age determinations. Annuli were laid down in late May to early June at the start of the growth period. Minimal growth occurred from November to April. Male dace grew minimally faster than females; Frome dace faster than those from the Stour. Growth rates in the two rivers were similar to those published for most other European waters. Variation in growth rates in different years was not great, but there were marked differences in recruitment success. Spawning occurred in the second half of March and elaboration of the gonads between September and March. Immature dace have an annual cycle in condition with a maximum in June and a minimum during the winter months. The condition of the mature females is affected by the gonad cycle. The fecundity of Stour dace is represented by the formula:

and for Frome dace by:

Most dace were mature by age IV, but there were more mature II and III group fish in the Frome population. Molluscs and Trichoptera larvae comprised the bulk of the winter diet of Stour dace, and Ephemeroptera nymphs, Simulium and chironomid larvae were the principal constituents during the summer.     

Viral infection cycles in pike (Esox lucius L.)

Pike fry weighing 0.2 g were infected with five pathogenic viruses via the water and then fed to one-year-old, 60 g pike. A transer of the viruses from the prey to the predator was demonstrated. The VHS virus produced typical hermorrhages in the muscle of the second nost. Zusammenfassung Zyklische Virusinfektion beim Hecht (Esox lucius L.) Auf dem Wasserweg mit fünf fischpathogenen Viren infizierte Hechtbrut (0,2 g) diente einjährigen Hechten (60 g) als Nahrungsquelle und gewährleistete hierdurch den Virustransfer. Das VHS-Virus induzierte im 2. Wirt typische Hämorrhagien in der Muskulatur. Résumé Cycles d'infection viraie chez le brocket (Esox lucius L.) Des embryons du brochet (0,2 g) inficés par l'eau servaient comme nourriture pour des brochets agés un an (60 g). Par cela le transfer du virus était verifié. Le virus VHS causait dans l'hôte seconde des hemorrhages typiques dans les muscles.     

The biology of pike, Esox lucius L., in a southern eutrophic lake

The biology of pike, Esox lucius L., in a southern productive lowland lake is described. Scales and opercular bones were difficult to read and interpret, and growth estimated had perforce to be based on scale readings. Growth of Slapton pike is average and intermediate between recorded extremes. Both male and female pike reached maximum condition in February, just prior to spawning. The population of pike of over 450 mm fork length in the lake was estimated at 870·6 ± 389·3 in 1975, and 950·4 ± 143.3 in 1976/77. This leads to the conclusion that the pike population has one of the highest biomasses per surface area of water ever recorded. Number of pike per unit area of surface was also high, despite the fact that a significant proportion of the population (fish under 450 mm) could not be adequately sampled. Mean instantaneous mortality rate was 0·53, and mean instantaneous survival rate was 0·59. The roach provided the main item of diet of the pike, with perch taken less readily. Immature pike ate a significant proportion of invertebrates, but roach was again a common feature of the diet of even small fish. Two spawning migrations were identified; at other times of the year, pike were non territorial. The majority of pike spawned in March. Fecundity of a sample of females was assessed. Overall sex ratio was 1:1.     

Wetlands for northern pike (Esox lucius L.) recruitment in the Baltic Sea

In recent decades, wetlands have been constructed or restored around the Baltic sea to counteract the eutrophication of its coastal waters. Some of these wetlands could also be suitable spawning and nursery areas for anadromous northern pike (Esox lucius L.). We studied juvenile pike production in three coastal wetlands along the south-eastern coast of Sweden that were restored in different ways. Where terrestrial vegetation was temporarily flooded, pike larval/juvenile emigration increased from a few thousand individuals before restoration to over a hundred thousand afterwards. We suggest that vegetation was the key to this successful reproduction, as wetlands where vegetation was removed or reduced saw no similar increase in pike production. Flooded vegetation in shallow waters offers optimal spawning conditions, increased food resources, and refuge from predation. The growth and emigration of larvae and juveniles were followed over time, revealing that 80–95% of individuals left the wetlands within 1 month (at a size <6 cm). This emigration probably represents an adaption to seasonally decreasing water levels but may also be a way to avoid cannibalism.     

Partial characterization of transferrins of catfish (Silurus glanis L.) and pike (Esox lucius L.)

Basic composition and properties of isolated transferrins of Silurus glanis and Esox lucius have been compared. In transferrin of S. glanis carbohydrate is absent, but it is present in transferrin of E. lucius (2.5%). The N-terminal amino acid is alanine in both species. Mol. wts are 68,400 (S. glanis) and 86,800 (E. lucius). Transferrins of the two species are heterogeneous, but genetic polymorphism was not observed.     

Blood values in the pike Esox lucius L.

The ranges and mean values of haematocrit, red cell, white cell and differential cell counts, red/white cell ratio, red cell fragilities, haemoglobin levels and serum protein concentrations of adult pike Esox lucius L. have been measured, and the serum electrophoretic patterns on cellulose acetate and polyacrylamide gel described and discussed. It is hoped that these blood values will provide normal standards for the pike since normal ranges are wide, and isolated measurements therefore of limited value.     

Seasonal dynamics of fatty acid composition in female northern pike (Esox lucius L.)

Seasonal changes in the fatty acid composition of neutral and polar lipids were measured in the ovary, liver, white muscle, and adipopancreatic tissue of northern pike. The role of environmental and physiological factors underlying these changes was evaluated. From late summer (August–September) to winter (January–March), the weight percentage of n-3 polyunsaturated fatty acids (especially 22:6n3) declined significantly in the neutral lipids of all somatic tissues examined. However, large quantities of n-3 polyunsaturated fatty acids accumulated in the recrude cing ovaries during fall and the weight percentage of n-3 polyunsaturated fatty acids in ovary polar lipids also increased significantly. Additionally, the n-3 polyunsaturated fatty acid content of somatic polar lipids increased significantly during fall due to increases in the total polar lipid content of the somatic tissues. This suggests that during fall n-3 polyunsaturated fatty acid are diverted away from somatic neutral lipids and thereby conserved for use in ovary construction and for incorporation into tissue polar lipids. The percentage of n-3 polyunsaturated fatty acid in ovary neutral lipids also declined during fall and early winter, perhaps as an adaptation to conserve these fatty acids for storage in oocyte polar lipids and later incorporation into cellular membranes of the developing embryo. Reductions in the n-3 polyunsaturated fatty acids content of somatic and ovarian neutral lipids during fall were compensated for specifically by increases in the percentage of monounsaturated fatty acids rather than saturated fatty acids. This suggests that the ratio of saturated to unsaturated fatty acids in pike neutral lipid, is regulated physiologically, and hence may influence the physiological functioning of these lipids. During fall and early winter the percentage of saturated fatty acids declined significantly in the polar lipids of all tissues examined. This change was consistent with the known effects of cold acclimation on the fatty acid composition of cellular membranes. As the ovaries were recrudescing from September to January, liver polar lipids exhibited significant decreases in the percentage of total polyunsaturated fatty acids and n-3 polyunsaturated fatty acids and increases in monounsaturated fatty acids, and acquired a fatty acid composition very similar to that of ovary polar lipids. Therefore, seasonal changes in the percentage of polyunsaturated and monounsaturated fatty acids in liver polar lipids probably reflect the liver's role in vitellogenesis rather than the effects of temperature on membrane fatty acid composition. At all times of year, the fatty acid compositions of white muscle and adipopancreatic tissue neutral lipids were very similar, which may indicate a close metabolic relationship between these lipid compartments.Abbreviations AP adipopancreatic - BHT butylated hydroxytoluene - CI confidence interval - EFA essential fatty acids - MUFA monounsaturated fatty acids - NL neutral lipids - PL polar lipids - PUFA polyunsaturated fatty acids - SFA saturated fatty acids     

Genetic characterization of 18 novel microsatellite loci in northern pike (Esox lucius L.)

The northern pike (Esox lucius L.), an important predatory freshwater species, is undergoing significant population decline. In this study, 18 novel polymorphic microsatellite loci were isolated and used for assessing genetic variation in the Chinese Ulungur and Hungarian Balaton populations of the species. The number of alleles ranged from 2 to 13, observed heterozygosity from 0.154 to 0.920 and expected heterozygosity from 0.145 to 0.921, thereby indicating the specific usefulness of these suites of markers for investigating genetic variability.     

Hydrocephalus and red-disease in pike fry Esox lucius L.

Two diseases of pike fry have been investigated, both causing serious losses in Dutch pike culture. In one of these diseases the lump developing on the head of the fry was associated with an internal hydrocephalus.
The other one, 'red disease' after the haemorrhagic areas in the trunk, may be identical with red-sore disease of pike.
The etiologies of both diseases are unknown.     

The influence of angling-induced exercise on the carbohydrate metabolism of northern pike (Esox lucius L.)

Summary Capture by angling was used to induce burst exercise in northern pike. By 3 h after exercise blood lactate had risen to levels of 15.2 mmol l⁻¹ (Fig. 2), which greatly exceeded the maximum post-exercise levels (4.0 mmol l⁻¹) previously reported for muskellunge, a close relative of pike. White muscle lactate level was high, 41.8 mmol kg⁻¹, immediately after capture but declined to 23.2 mmol kg⁻¹ by 6 h (Fig. 2). Blood glucose level more than doubled after exercise and remained elevated even after 96 h of recovery (Fig. 2). During the first 6 h after angling, pike disposed of 9.57 mmol (861 mg) of lactate per kg body weight. A whole body metabolic rate of 153 mg O₂ kg⁻¹ h⁻¹ is sufficient to account for this rate of lactate removal through oxidation (Table 3). However, the metabolic rate of the highly oxidative organs and tissues (red muscle, gills, liver, kidney, heart, and spleen) must be very high (>1,000 mg O₂ kg⁻¹ h⁻¹) to oxidize even 60% of the lactate that disappeared from pike after exercise (Fig. 5). Mortality of pike from angling stress was less than 3%.     

The annual reproductive cycle of pike, Esox lucius L., in two Scottish lakes

Histological changes in the ovaries of pike from two shallow, adjacent, Scottish lakes are described and related to a macroscopic scale of maturity stages and to changes in gonad weight. There was no evidence of pre-ovulatory degeneration although occasional residual oocytes were present in spent ovaries. The gonadosomatic index (GSI) was high in males from October to March, and in females it increased through the winter months to a maximum immediately prior to spawning. Maximum ovarian weight was 8.3–9.0% of total body weight compared with only 0.9–1.1% for testes. These GSIs were low compared with other reports for the British Isles, suggesting lower reproductive output. Spawning occurred in the first two weeks of April at a water temperature of 6.0–7.5° C. Fecundity was described from a regression of egg number (F) on fork length (f.l.): log₁₀F= -1.51 + 3.33 log₁₀ f.l. (cm). Mean egg diameter after preservation varied from 1.1 to 2.4 mm over the size range examined. Males were mature at age 2 at a length of ≥ 27 cm, while females first spawned at age 3 at a length of ≤ 28 cm, although a minority were mature at age 2. The sex ratio was 1.2 males: 1 female at Kinord and 1.4 : 1 at Davan. Greater egg production at Davan, 50 678 ha^?1, compared with Kinord, 33 557 ha^?1, was due to higher individual fecundity-at-age resulting from better growth. Fecundity (19.29 × 10³ calculated for a pike of 55 cm F.L.), relative fecundity of only 10–24 eggs per gram wet weight of adult, and GSI values were low compared with pike in North America and Eurasia. Food supply may restrict reproductive output of pike in Lochs Kinord and Davan. The abundance ratio of predator: prey is high with the main prey species, perch, present in low numbers, and the only alternative species is eel in these simple fish communities.     

Growth of pike Esox lucius L. in Lake Rubikiai (Lithuania)

The aim of the study was to determine the growth rate and growth parameters of pike Esox lucius L. in the mesotrophic Lake Rubikiai and to evaluate species growth in light of environmental conditions in Lithuanian lakes of different limnologic types. A total of 204 pike specimens were caught in two subsequent years, April 2005 and April 2006, in Lake Rubikiai. Six age classes (2–7 years of age) for males and 10 age classes (3–12 years of age) for females were identified by scale readings; 2‐ to 4‐year‐old males and 4‐ to 7‐year‐old females prevailed. Total length of pike ranged from 26.5 to 107 cm and weight from 106 to 7600 g. There were no statistically significant differences (Student’s t‐test, P > 0.1) between mean lengths and weights of males and females of the same age. Von Bertalanffy growth parameters for the entire population were: L_∞ = 131.7 cm, k = 0.1530 year^?1, t_o = ?0.0398 year. Calculated overall growth performance index ?′ was 3.42. The length‐weight relationship was described by the equation . The growth rate of pike in Lake Rubikiai was higher than in most other investigated Lithuanian lakes. Pike from Lake Rubikiai are characterized by average growth, compared to other populations from various geographical locations. No significant differences were established between the growth of pike in mesotrophic and eutrophic lakes. Pike growth rate did not correlate with lake surface area, maximum or mean depth, and negatively correlated with bogginess in mesotrophic lakes and limpidity and bogginess in eutrophic lakes (P < 0.05).     

The hepatic glutathione content and glutathione S-transferase activity in the pike (Esox lucius L.) and rat.

1. The content of glutathione and glutathione disulfide and the activity of the glutathione S-transferase were determined in the liver of pike and rat. 2. It was found that the liver of pike contains far less glutathione than the liver of rats, while the glutathione disulfide content was similar in both species. 3. The activity of the hepatic glutathione S-transferase was more effective in pike than in rats.     

Effects of photoperiod, feeding regime and water temperature on the formation of daily growth increments in otoliths of larval pike (Esox lucius L.)

Otolith growth increments of larval pike, Esox lucius L., were examined using known-age fish reared in the laboratory. Under different photoperiod, feeding, and temperature regimes, increments in the lapilli of all laboratory-reared fish were formed daily, starting on day 2–3 after hatching.

Zusammenfassung

Der Einfluß van Photoperiode, Futterrhythmus und Wassertemperatur auf die Anlage von Otolithen-Tagesringen bei jungen Hechten (Esox lucius L .)
Die Anlage von Tagesringen auf den Otolithen von Hechtlarven ( Esox lucius L. ) wurde unter verschie-denen Licht-, Futter- und Temperaturbedinungen im Labor untersucht. Bei allen Tieren setzte die Bildung von Tagesringen auf den Lapilli zwei lis dreiTage nach dem Schlüpfen ein.     

Experimental studies on some trophic relationships in juvenile pike, Esox lucius L.

A postprandial increase in ammonia nitrogen excretion and oxygen consumption rates was observed in juvenile pike fed a natural diet or an artificial dry diet. Specific growth rate of natural diet fed pike (2.4%) was lower than that of pike fed the artificial diet (3.1%). Fifty per cent of ingesta was evacuated within 5–6 h in pike of 25 mg body weight and 9–10 h in those weighing 150mg. Daily nitrogen excretion rates were related to body weight. Respiratory quotient and energy retention efficiency were affected by the nature of the diet ingested by pike. Parameters of the energy balance (losses, retention, increment due to feeding) were related to energy intake.     

Observations on the age, growth, reproduction and food of the chub Squalius cephalus (L.) in the River Stour, Dorset

Opercular bones from 399 chub from the River Stour, Dorset were used for age and backcalculated growth measurements. Scales were only used to aid the interpretation of difficult operculars. Annuli were laid down through the period mid-April to mid-June. Growth in length was minimal between October and March. Growth rates were similar to those published for chub in other European waters, but the Stour chub were longer-lived and attained a greater ultimate size. Female chub grew faster than the males. Spawning occurred from late May into June and elaboration of the gonads took place between September and May. Immature chub had an annual cycle of condition; the 0 group having a maximum in August and older immature fish reaching their maximum in June. Both categories had a minimum condition in early spring. The cycle of gonad development affected the condition of mature fish. The numbers of eggs in chub of lengths 359–467 mm ranged from 27 000–65 000. Some females attained sexual maturity at age V or VI, but most by age VII. The majority of males matured at age V, though some at ages III or IV. Growth rates and year-class strengths varied from year to year but independently of one another. Thirty-one per cent of chub aged II and over belonged to the 1959 year class. Young chub ate insect larvae and small crustacea, but the occurrence of fish and macrophytes was greater in the diet of older fish.