Prey capture in the pike-perch,Stizostedion lucioperca (teleostei,percidae): A structural and functional analysis

Summary The pike-perch,Stizostedion lucioperca, uses both suction and grasping during feeding. Type, size, and position of prey and predator determine the movement of catching. This is concluded from simultaneous motion analysis, electromyography, and the record of pressures inside the buccopharyngeal cavity during feeding. The EMG incorporates 24 muscles of the head, including the branchial basket and the anterior body musculature. When the pike-perch begins to feed acceleration and expansion of the head parts determine the negative buccopharyngeal pressure and therefore the suction force applied to different preys. Not the head muscles, but the epaxial and hypaxial body musculatures provide the main force for the rapid expansion of the head through movements of the neurocranium, pectoral girdle, and hyoid arch. Despite the lack of a true neck, the pike-perch is able to move its neurocranium in all directions to aim the suction force. The experiments revealed that ventral and lateral movements aid in the ingestion of a big prey after it has been grasped with the teeth. The head muscles are active as regulators of the opening movements and in the closing movements. Variable overlaps of ab- and adductor activity show that their contraction patterns are interdependent. Variations in the recorded pressures can be related largely to a series of EMGs showing different starting moments of adductor contraction. In this progressive series two patterns were distinguished, and their accompanying movements were compared and related to the type of prey. According to the feeding behavior and morphology, the pike-perch is classified as a rapacious predator. Comparison with some other voracious fishes shows that besides the total length of the lower jaw and the dentigerous area, the construction and dentition of the upper jaws and the anterior suspensorial and neurocranial parts are also important features of this ecological type. However it appears that the fishes selected for this comparison use suction rather than the teeth as the main means of catching the smaller, but commonly eaten prey. The teeth prevent escape after capture by sucking and they increase the maximum prey size that can be caught. In this group, the head ofStizostedion appears to be comparatively well adapted to sucking with grasping adaptations.     

Aquaculture of fry and fingerling of pike-perch (Stizostedion lucioperca L.) — a short review

This review presents a short survey of pertinent literature on rearing methods of pike-perch fry and fingerlings in ponds, net cages and tanks. The traditional pond culture results in variable numbers of fingerlings, which are sometimes small and are therefore of limited value for stocking. Fingerling production can be increased by manipulating the succession of zooplankton and by stocking adequate quantities of fry in the pond. Culture in illuminated net cages in lakes seems to be a possibility to produce advanced fry. The rearing of larvae in tanks following controlled propagation is initially based on feeding natural plankton. The artificial diet can only be used successfully several weeks later at fingerling size (4–5 cm). High mortality rates of fry and symptoms of food deficiency in liver cells indicate unsatisfactory quality of larval diets tested until now. Lack of an adequate artificial feed considerably hampers further development of intensive rearing of fry. Growth of fry and fingerlings is strongly temperature dependent. Growth is rather poor at 16–18°C and best between 26–30°C. Although there is a short stage of positive phototropism in fry, older pike-perch generally prefer dim light. There is no food uptake at high light intensity and mortalities will occur under such conditions. More research is needed on adequate diets which consider the ontogenetic development of the digestive organs of young fish.     

Reproduction and spawning in walleye (Stizostedion vitreum)

The walleye ( Stizostedion vitreum ) is a North American mesothermal freshwater teleost that spawns once each year in early spring. Walleye spawn randomly over suitable substrates and do not provide any parental protection for eggs or juveniles. The majority of gonadal recrudescence in adult male walleye occurs in the autumn, and walleye testes contain large numbers of viable spermatozoa from late autumn through the spawning season. Adult female walleye exhibit group synchronous ovarian development, and similar to males, the majority of gonadal development occurs in the autumn. Evidence suggests that 17α,20β-dihydroxyprogesterone is the maturational steroid in this species. Simple environmental manipulations coupled with injections of human chorionic gonadotropin can be used to advance spawning in walleye by up to 12 weeks. To spawn and propagate walleye, hatcheries in North America use a wide range of methods that have been developed to meet the needs and conditions present at specific facilities.     

Migratory behaviour of adult pikeperch (Stizostedion lucioperca) in a lowland river

The behaviour of radio-tagged adult pikeperch (Stizostedion lucioperca (L.)) from two areas in the Danish River Gudenaa were recorded prior to, and during the spawning period. Eight of 13 tagged fish in the lower reaches of the river were located throughout the whole study. Five of these fish moved upstream to various sites in the river prior to spawning, which occurred from late April to June. The three remaining fish moved to the fjord. These movements were interpreted as a spawning migration, and it is suggested that the lower reaches of the River Gudenaa constitute an over-wintering area for pikeperch, which use different spawning areas. Ten pikeperch caught just downstream of an impassable hydropower plant were radio-tagged and translocated upstream of the dam to a reservoir. Within a week, half of the fish moved to a lake situated more than 30 km upstream the reservoir. This behaviour is hypothesised to be a homing response. The study reveals that the pikeperch is a highly mobile species with a complicated migration pattern, even in relatively small river systems.     

Acute and chronic nitrite toxicity in juvenile pike-perch (Sander lucioperca) and its compensation by chloride

Pike-perch Sander lucioperca is currently considered as one of the most promising candidates for production in freshwater recirculation aquaculture systems (RAS). Here, due to the lack of studies on nitrite (NO₂^?) toxicity in pike-perch, a flow-through exposure at 0, 0.44, 0.88, 1.75, 3.5, 7, 14 and 28 mg/L NO₂^?–N was carried out to determine the acute and chronic toxicity over a period of 32 days. In juvenile pike-perch, 120 h LC₅₀ was 6.1 mg/L NO₂^?–N and at ≥ 14 mg/L NO₂^?–N all fish had died within 24 h. Chronic exposure revealed a significant build up of NO₂^? in the plasma as well as in the muscles at ≥ 0.44 mg/L NO₂^?–N peaking in fish exposed to the highest concentration of 3.5 mg/L NO₂^?–N after 32 days. Still, due to high individual variation methemoglobin (MetHb) was only significantly increased (p < 0.01) at 3.5 mg/L NO₂^?–N. No adverse effects on red blood cells (RBC) and hematocrit were observed in any of the treatments. In a second experiment, compensation of NO₂^? toxicity at increasing chloride concentrations (40 (freshwater), 65, 90, 140, 240, 440 mg/L Cl^?) was observed at a constant exposure of 10 mg/L NO₂^?–N for 42 days. At ≥ 240 mg/L Cl^?, NO₂^? build-up in blood plasma and muscle was completely inhibited. At lower Cl^? concentrations (≤ 140 mg/L), NO₂^? was significantly increased in plasma, but only insignificantly elevated in muscle due to high individual variation. MetHb was increased significantly difference only at 40 mg/L Cl^? (freshwater control) compared to the control. Again, high individual variations were observed. As a conclusion, S. lucioperca is moderately sensitive towards NO₂^? and acceptable levels in RAS should hence not exceed 1.75 mg/L NO₂^?–N to avoid MetHb formation. However, based on the 120 h LC₅₀ and a factor of 0.01 according to Sprague (1971), a NO₂^? concentration of ≤ 0.061 mg/L NO₂^?–N is considered as “safe.” Thereby, no NO₂^? should accumulate in the plasma or muscle tissue during chronic exposure. For 10 mg/L NO₂^?–N, ≥ 240 mg/L chloride compensates for NO₂^? uptake in plasma and muscle.     

Reproduction of Asian chipmunks (Tamias sibiricus) in captivity

Factors affecting reproduction in captive Asian chipmunks, Tamias sibiricus, were examined by means of a survey of chipmunk breeders in Great Britain. Sixteen breeders were asked about the conditions under which their chipmunks were kept and their success in breeding them. Results covered 205 female-years of pairing. Breeding was promoted by large cage size and early weaning of young, and inhibited by the presence of other rodent species nearby and by extended photoperiod. A diet of seeds and nuts, with some fresh fruits and vegetables, appeared to be adequate for breeding. Breeding occurred in 80–91& of female-years when neither extra lighting nor other rodents were present, irrespective of cage size. Weaning age affected the occurrence of second litters in a year. Second litters were born less often (0–13&) of breeding (female-years) if young of the first litter remained with the mother 8 weeks or longer. Second litters were more frequent (14–45& of breeding female-years) if first litters were removed by 6.5 weeks of age, and this frequency increased with cage size. Litter size also increased with cage size (means ranged from 3 to 7). Overall breeding success increased with cage size and decreased with the presence of other rodents. In most colonies without other rodents near, mean success rate ranged from 3.1 to 8.5 young/female-year. In colonies with other rodents present mean success rate varied from 0 to 3.3 young/female-year. It is suggested that the mechanisms that control population size in the wild also act to inhibit or promote breeding in captivity.     

Dynamics of the Pikeperch,Stizostedion lucioperca (L.), in Lake Balaton

The pikeperch populations inhabiting three distinct water areas of Lake Balaton differ in regard of growth. Due to stock depletion, pikeperch in the NE-basin of the lake grew considerably faster than ten years ago. The annual rate of growth in length (von Bertalanffy's K) varied between 0.09 and 0.19. The specific rate of growth in length (G_L) ranged from 0.16 to 0.23 and that of growth in weight (G_W) from 0.52 to 0.69. Length and age-structures of the stocks differed significantly between different areas and years, but the overwhelming majority of the stocks consisted of age-groups IV–V (98.2–99.3%). From NE to SW, the rates of survival were 34, 29 and 70%, respectively. These differences, and the differences in growth resulted in changes in the productive capacity of the stocks. The ratios of production and biomass were 59% (NE-basin), 63% (central basin) and 39% (SW-basin), respectively. The magnitudes of production varied inversely. The 50% retention lengths of the seine nets used in Lake Balaton were 35.0, 35.7 and 42.5 cm with weights of 572, 655 and 1019 g, respectively.     

Reproduction of the mongoose lemur (Lemur mongoz) in captivity

Responses to questionnaires sent to 20 institutions holding Lemur mongoz did not reveal which aspects of management or husbandry could account for reproductive failure in the captive population, but allowed some qualitative comparisons with data compiled for captive and wild animals. In general, reproduction has occurred initially among wild-caught specimens before tapering off, and rarely occurs in the captive F₁ generation. Data compiled by the International Species Inventory System and the International Zoo Yearbook revealed an aging captive population with no recent reproduction. No aspect of group composition, activity patterns, seasonal light regime, reproductive cycles, or diet could be linked to the lack of reproduction; and among lemurs subjected to the same conditions, some were known to reproduce while others did not. Lack of knowledge about this species and the threat of extinction for both captive and wild populations make an investigation of reproductive biology imperative. Recommendations for a research program are given.     

Characteristics of the localization of Ancyrocephalus paradoxus (Monogenea) on the pike perch Stizostedion lucioperca

In one summer old fishes of the pike perch, caught in the K urish Gulf of the Baltic Sea in August-September of 1984, at 100% infection with A. paradoxus 94% of monogeneans were localized under the lower anterior angle of the operculum on the lateral surface of the intergill space (isthmus). In fishes 1+ on the isthmus there were found 52%, in pike perches 2+ 42%, and in fishes 3+ 67% of worms. In older fishes (4-10+) the number of worms on the isthmus accounts for 5% of their total number while others are localized on gill filaments. Variability of sizes, chitinoid structures and microlocalization of worms depending on the age of fish were established.     

Reproduction in the crowned lemur (Lemur coronatus) in captivity

Four pairs of captive crowned lemurs (Lemur coronatus) were studied during their annual breeding season in order to obtain baseline data on their reproductive biology for comparison with other Lemur species and to enhance their captive breeding success. Vaginal smears, testicular measurements, and records of the Duke University Primate Center provided the presented data. During a single breeding season, females cycled an average of three times, with an average cycle length of 34 days. Cycles were detected between November and March. Vaginal estrus and copulations were limited to one day per cycle. After 125 days of gestation females gave birth to one or two young. Both sexes attained sexual maturity at an age of about 20 months. Mean male testis size peaked in late December; at the same time, three of the females experienced their first estrus. Based on all available data, there was a significant positive correlation between cycle length and gestation length in the genus Lemur.     

Isolation and characterization of nine microsatellite loci from the pike-perch, Sander lucioperca (Linnaeus, 1758)

In order to facilitate studies on the genetic structure of wild populations as well as to monitor genetic changes in cultured stocks, nine polymorphic microsatellite loci were isolated from pike-perch (Sander lucioperca). Single loci allele numbers varied between two (loci MSL-3 and MSL-7) and six (loci MSL-1 and MSL-2), and observed heterozygosities ranged from 0.36 (locus MSL-2) to 1.00 (locus MSL-9) in a test panel of 25 individuals. Only one pair of loci (MSL-5 and MSL-8) displayed significant linkage disequilibrium after sequential Bonferroni corrections. Hardy-Weinberg tests revealed significant excesses of heterozygotes at three loci (MSL-1, MSL-7, and MSL-9).     

Stress and survival of small pike-perch Sander lucioperca (L.) after trawling and chilling

The mortality and stress responses (plasma cortisol concentration) of undersized (total length, L _T, <370 mm) pike-perch Sander lucioperca caught as by-catch in a trawl fishery were assessed. The effects of three different holding methods on pike-perch caught by trawl were compared: (1) fish that were transferred to ambient-temperature water (15·0–21·4° C) immediately after capture and not exposed to chilling water, (2) fish held in chilling water for 10 min and (3) fish exposed to chilling water for 2 h. The sample fish were held and monitored in individual plastic restrainers at ambient-water temperature for 48 h after each of the handling procedures. Total mortality was similar for fish held in chilling tanks for 10 min (27·2% total mortality) compared to fish that were only held in ambient-temperature water (28·2% mortality). Total mortality reached 91·3% when fish were held in chilled water for 2 h. Mortality and plasma cortisol concentrations correlated inversely with size (96–368 mm L _T) and directly with lake-water temperature (15·0–21·4° C) after treatment. In addition, the effect of chilling was observed in elevated cortisol concentration and delayed start of recovery. The results show that quickly removing (<10 min) undersized pike-perch from chilled water could markedly improve the survival of released fish. Due to delayed recovery, however, fish should be allowed to recover (30–40 min) in a deck tank before release.     

Reproduction of the Indian wild dog (Cuon alpinus) in captivity

The reproductive behavior and development of 3 wild-caught and 2 captive-born dholes (Cuon alpinus) was observed at the Arignar Anna Zoological Park during 4 successive mating seasons. Courtship was characterized by frequent urine marking and vocalizing by both sexes, by olfactory inspection of marked spots and of partners' genitalia, and by the female's licking and mounting of the male. Dholes exhibited the copulatory tie and back-to-back copulatory posture that is typical of other canids. Estrus may be longer, and the frequency of copulation higher, than is seen in other canids, however. The 4 litters born to the wild-caught pair yielded information on growth and development. A captive-born pair first began to show signs of sexual activity at 11 months of age. © 1992 Wiley-Liss Inc.     

Habitat shift in roach (Rutilus rutilus) induced by pikeperch (Stizostedion lucioperca) introduction: predation risk versus pelagic behaviour

Changes in the fish community structure and habitat use were followed after the introduction of pikeperch (Stizostedion lucioperca) to the roach-dominated Lake Gjersjøen. Quantitative echosounding showed that the density of juvenile roach (Rutilus rutilus) was dramatically reduced in pelagic areas, from 12 000–15 000 fish/ha to 250 fish/ha, while total fish density remained unchanged in littoral areas. At the same time, the habitat segregation between different size groups of roach was altered as larger roach utilized the pelagic zone after pikeperch introduction. The loss of the pelagic refuge for juvenile roach increased the availability of juvenile roach to littoral predators, notably perch. In littoral areas, the fish community changed from one dominated by roach (> 95%) to one dominated by perch (> 50%).     

Reproduction of the owl monkey (Aotus spp.) in captivity

Abstract: The reproduction performance of captive owl monkeys, a breed used extensively in biomedical research, was observed at the Battelle Primate Facility (BPF). The colony grew through captive breeding, imports from the Peruvian Primatological Project, and others to a peak size of 730. It included seven karyotypes of Aotus sp. Results showed that owl monkeys can breed successfully in a laboratory in numbers sufficient to sustain modest research programs. Reproductive success increases when pairs are compatible, of the same karyotype, and stabilized; however, mated pairs of different karyotype are also productive. Under conditions of controlled lighting and heating, owl monkeys at BPF showed no birth peak nor birth season.     

New species of coccidia Eimeria stizostedioni sp. n. (Sporozoa: Coccidea) from the pike perch Stizostedion lucioperca (Perciformes)

A new coccidia species Eimeria stizostedioni from the pikeperch Stizostedion lucioperca (Perciformes) is described. Localities: Neva river. Prevalence: 20% (1/5). Intensity of infection weak. Oocysts 7.5-8.0 x 10.0-12.5 microns. The form varies from oval up to ovoid; a wall is sleek, colourless, single-layer two-planimetric, micropyle, the polar granules and residual body are absent. Sporocysts 3.5 x 6.5 microns, with Stieda body and residual body represented by few small granules. Sporogony is endogenous.