The effect of biomanipulation of the zooplankton on the growth, feeding and survival of pikeperch (Stizostedion lucioperca) in nursing ponds

The following treatments were evaluated for use in rearing pikeperch larvae (Stizostedion lucioperca L.) in nursing ponds: treatment with Dipterex (Bayer); concurrent stocking with common carp (Cyprinus carpio L.); short flooding periods and prefeeding fish larvae. Treatment with Dipterex (active ingredient trichloorfon, i.e. 00-dimethyl-2,2,2, trichlorohydroxyethyl phosphonate) gave zooplankton populations dominated by rotatoria and nauplii at the onset of exogenous feeding and dominated by copepods later on. Cladocerans dominated the plankton in untreated ponds but were never prominent in treated ones. Stomach analysis revealed a fast changing feeding preference in pikeperch from nauplii and copepodites towards cladocerans and chironomids. The excellent food conditions for first feeding pikeperch larvae in Dipterex treated ponds resulted in a significant higher number of harvested fingerlings. In spite of the more favourable food conditions in untreated ponds during the second half of the culture period, a significant growth difference was not found. Concurrent carp stocking did not affect significantly the survival and growth of the pikeperch, although it decreased the accessability of chironomids for pikeperch. Short flooding periods and prefeeding pikeperch larvae failed as useful management strategies for pikeperch nursing. Pikeperch fingerlings cultured in ponds are larger than those found in natural populations at the same time, giving them a high chance to become piscivorous and to increase the year class strength when stocked in natural waters.     

Characterization of the gut microbiota in early life stages of pikeperch Sander lucioperca

This study characterized the gastrointestinal microbiome of nine juvenile farmed pikeperch Sander lucioperca using a metagenomics approach based on bacterial 16S rRNA gene sequencing. Potential changes in the gut microbiota during 2 months of S. lucioperca juvenile life were investigated. Results revealed that gut microbiota was dominated by Proteobacteria (95–92%), while other phyla Firmicutes (1–1·5%) and Actinobacteria (0·9–1·5%) were less abundant. At the family level, fish‐gut microbiota were dominated by Enterobacteriaceae, which constituted c. 83% of all DNA sequence reads. Such a situation was present in all of the examined fish except one, which showed a different proportion of particular microbial taxa than the other fish. In this fish, a higher relative abundance (%) of Fusobacteria (21·0%), Bacteroidetes (9·5%) and Firmicutes (7·5%) was observed. There were no significant differences in the gut microbiome structure at different stages of development in the examined fish. This may indicate that Proteobacteria inhabiting the gut microbiota at an early stage of life are a necessary component of the pikeperch microbiome that may support proper nutrition of the fish. The information obtained on the gut microbiome could be useful in determining juvenile S. lucioperca health and improving rearing conditions by welfare monitoring in aquaculture.     

The fish community of the Loosdrecht Lakes and the perspective for biomanipulation

In a two-year-study, the fish community of the Loosdrecht Lakes area was characterized with regard to the professional fishery and the forage base. The lakes are shallow (mean depth 2 m) and eutrophic to hypertrophic. The bream,Abramis brama, dominates the fish biomass. The pikeperch,Stizostedion lucioperca, is the main predator.Bream up to 30 cm have a slow growth rate and are in a bad condition. A faster growth rate and a better condition are shown by bream of 30 cm and more. The small bream feeds on chironomid larvae, benthic cladocerans and zooplankton. The better condition of bream over 30 cm is explained by the more efficient feeding of larger bream onChironomus plumosus larvae. Pikeperch show a fast growth rate and a good condition. Recruitment is limited by the low densities of smelt,Osmerus eperlanus, leaving cannibalism as the most important way for the 0+ pikeperch to become piscivorous and to manifest a fast growth.The impact of the professional gillnet fishery on bream and pikeperch is small because the mesh sizes in use are as large as 75–100 mm bar mesh.The planktivorous 0+ pikeperch consumes mainly the carnivorous zooplanktersLeptodora kindtii and cyclopoids. The zooplankton community lacks large herbivorous species likeDaphnia hyalina, capable of consuming bluegreens. A possible experiment in biomanipulation with a view to find out whether the development ofD.hyalina is depressed by the small planktivorous cyprinids, is predator enhancement with the aid of a stocking programme for indoor-raised 0+ pikeperch in early summer.     

Early development of the postcranial skeleton of the pikeperch Sander lucioperca (Teleostei: Percidae) relating to developmental stages and growth

The early development of the postcranial skeleton (pectoral girdle, pelvic girdle, vertebral column and fins) in pikeperch (Sander lucioperca (L.)) was studied from hatching to days 47 and 43 post fertilization (dpf) at two different rearing temperatures, 15.5 and 18.0°C. Four embryonic and six larval stages were described, ranging from 3.4 ± 0.3 mm to 21.8 ± 2.1 mm in total length. The crucial point in larval development is swimbladder inflation, which enables larvae to swim energy efficiently. Until this time point, only the most essential skeletal elements to enable swimming movements have developed. As the larvae become neutrally buoyant, they grow and differentiate postcranial elements rapidly. Concurrently, swimming performance and foraging success seems to improve. A specific size is correlated with a distinct developmental stage defined by a set of traits that includes the skeletal elements. The developmental sequence of skeletal structures is temperature independent, although growth is slower and the individual developmental stages are reached later at 15.5°C than at 18.0°C. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Length rather than year‐round spawning,affects reproductive performance of RAS‐reared F‐generation pikeperch,Sander lucioperca (Linnaeus, 1758) – Insights from practice

The continuous production of large numbers of high quality gametes is essential for aquaculture, particularly in candidate species, such as pikeperch, Sander lucioperca (L.). The common practice of year‐round reproduction is under suspicion of inflicting adverse effects on the quality of the gametes through the disturbance of endogenous rhythms. We hypothesized that such perturbation does not affect RAS‐reared F‐generation broodstock. Reproductive performance (number of eggs) and gamete quality (fertilization and hatching rate) were assessed over the course of 3 years covering six independent, photothermal shifted spawning seasons in a commercial pikeperch hatchery (n = 31 egg batches of F‐generation fish in total). No substantial differences in fertilization or hatching rates could be detected between the individual spawning seasons. Fecundity varied, but there are indications for a size effect on female fecundity with intermediate sized females producing higher number of eggs (~65–70 cm). Low egg quality could be detected in batches of very large fish. In conclusion, size‐specific broodstock composition, but not year‐round reproduction of F‐generation pikeperch spawners affects the reproductive performance.     

Influence of lecithotrofic feeding on growth and development of larvae of freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

In the giant freshwater prawn Macrobrachium rosenbergii (De Man), lecithotrofic feeding was discovered at the zoea I stage, and facultative lecithotrofic feeding was found at the zoea II stage. Cases of the completion of the first two stages without feeding were detected. However, a delay in feeding at the zoea II stage caused the inhibition of the growth and development of larvae. In this connection, we recommend to introduce food to the aquaculture of the giant freshwater prawn on the end of the first day after hatching, when the first zoea II larvae emerge.     

The role of kilka (<Emphasis Type="Italic">Clupeonella cultriventris</Emphasis> (Nordmann)) in the diet of predatory fish of the Rybinsk reservoir

Data on predator fish feeding in the Rybinsk reservoir in the first years (2000–2003) of Ponto-Caspian kilka expansion are given. It is shown that the kilka’s penetration into the Rybinsk reservoir caused changes in the feeding spectra of predator fish. Kilka became one of the main objects of predator feeding throughout the whole year. In the open water period, it is consumed by pikeperch Stizostedion lucioperca (Linnaeus) and Volga pikeperch Stizostedion volgense (Gmelin) in the pelagial and by pike Esox lucius Linnaeus and perch Perca fluviatilis Linnaeus in the sublittoral and shallow bays. In winter it is mostly eaten by burbot Lota lota (Linnaeus) and pikeperch.     

Ontogeny of feeding and respiration in larval Atlantic cod Gadus morhua (Teleostei,Gadiformes): I. Morphology

Cranial development in larval Atlantic cod Gadus morhua was studied throughout ontogeny using specimens treated by staining and clearing, scanning electron microscopy and histology. Newly hatched cod larvae have closed mouths, no operculii, five well-developed branchial arches, and transversii ventralis muscles. During the endogenous feeding (yolk-sac) stage, viscerocranial structures remain simple and nonarticulated. Six days after hatching at 5°C, articulation occurs between the quadrate/Meckel's cartilage and the hyomandibula/cranium. Integration of skeletal elements results in a functional jaw that facilitates the transition from endogenous to exogenous feeding. During later ontogenetic stages, the opercular apparatus and levator-operculi coupling develops, facilitating the transition of cutaneous to branchial respiration. Overall, feeding and respiratory needs are met by changes in form (including composition) and function during larval fish growth and are correlated with demands of energy acquisition essential to survival. © 1996 Wiley-Liss, Inc.     

Early development of the skull of Sander lucioperca (L.) (Teleostei: Percidae) relating to growth and mortality

The early osteological development of the skull (chondrocranium and osteocranium) of the pikeperch Sander lucioperca was studied. Specimens were reared at two temperatures, 15·5 and 18·0° C, from hatching until 47 and 43 days after fertilization (DAF), respectively. The skeletal elements characteristic for the different developmental stages were the same at both rearing temperatures, but pikeperch reared at 15·5° C reached the developmental stages later. The formation of the functional complexes, the neurocranium, jaws and suspensorium, branchial basket and hyoid arch, was evaluated chronologically. The focus was on skull development during several functional changes: at hatching, at the shift from endogenous to mixed feeding, the shift to exclusively exogenous feeding and upon reaching the final prey-capture mechanism. Growth in total length differed between fishes reared at the two temperatures, except during a phase of very slow growth from the end of the embryonic stage until the second larval stage. The latter phase, in which most of the bony elements of the viscerocranium started to form, was marked by high mortality. When exogenous feeding began, the growth rates at both temperatures increased distinctly and the first bony elements were formed in the neurocranium. Specimens reared at 18·0° C grew continuously, but those at 15·5° C showed a second period of slow growth and high mortality. Fish reared at 18·0° C reached the successive larval stages distinctly earlier than fish reared at 15·5° C.     

The effects of diet and stocking density on the growth and behaviour of pond pre-reared pikeperch under intensive conditions

Experiments were carried out between 1999 and 2001 on pikeperch fingerlings using two feeds at four stocking densities to evaluate the success of training 35‐day‐old pond‐reared pikeperch, Stizostedion lucioperca L., to lifeless feed in intensive culture. Training periods of 28 days for each of three cohorts (1999–2001) were applied to introduce pikeperch from zooplankton to minced feed. In a preliminary study (1999), two feeds (live prey and minced fish meat) were compared at two stocking densities. Two higher densities were investigated in 2000 and 2001 and matched with the minced fish diet. Different feeds had significant effects on feed consumption and, as a consequence, on body weight gain; fish fed live prey showed highest growth rates. Unexpectedly, the stocking density had no significant effect on growth, and at the highest density there was a significantly betterfeed conversion rate. Stocking density and feed type significantly influenced the feeding behaviour. Three characteristic foraging techniques are described.     

Occurrence of age‐0 year dwarf pikeperch Sander lucioperca in late summer – an overlooked phenomenon in reservoirs

Late summer sampling of pelagic age‐0 year fish communities in five Czech reservoirs and one Dutch reservoir revealed extremely small age‐0 year pikeperch Sander lucioperca (mean 24 mm standard length, L_S, minimum 13 mm L_S) alongside more normal‐sized S. lucioperca that are found at the end of the first growing season (mean 50 mm L_S), resulting in two clearly size‐separated cohorts. Reference to such small age‐0 year S. lucioperca in lakes or reservoirs at this time of year and in such large numbers are almost absent the scientific literature, and the presence of these small S. lucioperca is contradictory to the common understanding of the reproductive biology of this species. This overlooked phenomenon may have a major effect on the population dynamics of this valuable species because of size‐dependent winter mortality.     

Effects of the timing of initial feeding on growth and survival of spotted mandarin fish Siniperca scherzeri larvae

The effects of delayed first feeding on growth and survival of spotted mandarin fish Siniperca scherzeri larvae were examined under controlled conditions. Morphometric characters [yolk‐sac volume, oil globule volume, head depth (H_D), body depth (B_D), eye diameter (E_D), musculature height (M_H), mouth diameter (M_D) and total length (L_T)], body mass (M), specific growth rate (S_GR) and survival were evaluated under different first‐feeding time (2, 3, 4 and 5 days after hatching). Larvae began to feed exogenously at 2 days after hatching (DAH) and the point of no return (P_NR) occurred between 5 and 6 DAH at 23° C, range ±1·0° C. The yolk volume of larvae first‐fed at 2 days had a significant difference compared with that of larvae first‐fed at 3, 4 and 5 days on 3 and 4 DAH. The larvae first‐fed at 2 days achieved comparatively better growth performance than that of 3, 4 and 5 days. On 5 DAH, all morphometric characters had significant differences between 2 and 5 days and 2 and 4 days initial feeding, respectively. Total mortality was recorded on 9 DAH for the larvae first‐fed at 5 days. On 12 DAH, significant differences were observed between 2 and 4 days and 3 and 4 days initial feeding for all morphometric characters. From 16 DAH to the end of experiment, all growth variables of the larvae first‐fed at 2 days were significantly higher than those in other treatments. The S_GR (2–9 DAH) first‐fed at 2 and 3 days were significantly higher than 4 and 5 day treatments, and the S_GR (9–16 DAH) first‐fed at 2 days was significantly higher than 3 and 4 day treatments. There was no significant difference, however, of S_GR (16–28 DAH) among treatments. Survival rate was significantly higher at 2 days initial feeding (27·42%) when compared with 3 (15·96%) and 4 days (7·92%) initial feeding at the end of experiment. The present study suggests that the first feeding of S. scherzeri larvae should be initiated at 2 days after hatching for achieving good growth and survival.     

Feeding habits and ontogenic changes in digestive enzyme patterns in five freshwater teleosts

Feeding habits and the activity of digestive enzymes (total alkaline proteases, α‐amylase and lipase) from dace Leuciscus leuciscus, roach Rutilus rutilus, Prussian carp Carassius auratus gibelio, perch Perca fluviatilis and pikeperch Sander lucioperca fry were studied in the Malye Chany Lake–Kargat Estuary (western Siberia, Russia). The diet of fry from all studied species was mainly composed of chironomid larvae and zooplanktonic organisms (i.e. cladocera and copepoda), whereas carnivorous species such as P. fluviatilis and S. lucioperca also preyed on fry from other fishes while detritus and microalgae were also important in the diet of ommivorous species. When comparing diet similarity (Sørensen–Dice index, Q_S) among fry at different stages of development, both omnivorous and carnivorous species showed a high level of similarity (0·67 < Q_S < 0·89 and 0·73 < Q_S < 0·89, respectively). Diet similarity values were in agreement with the overall digestive activity profile analysed by cluster analysis. Diet similarity suggested potential trophic competition when zooplanktonic and benthic prey began to decline towards autumn. The analysis of pancreatic digestive enzymes revealed a correlation among their activities and fry feeding habits with α‐amylase:total proteases (A:P) values higher than 1 in omnivorous species and lower (A:P ≤ 1) in carnivorous species.     

Allometric growth and larval development in Pacific red snapper Lutjanus peru under culture conditions

Allometric growth is a common feature during fish larval development. It has been proposed as a growth strategy to prioritize the development of body segments related to primordial functions like feeding and swimming to increase the probability of survival during this critical period. In the present study we evaluated the allometric growth patterns of body segments associated to swimming and feeding during the larval stages of Pacific red snapper Lutjanus peru. The larvae were kept under intensive culture conditions and sampled every day from hatching until day 33 after hatching. Each larva was classified according to its developmental stage into yolk-sac larva, preflexion larva, flexion larva or postflexion larva, measured and the allometric growth coefficient of different body segments was evaluated using the potential model. Based on the results we can infer the presence of different ontogenetic priorities during the first developmental stages associated with vital functions like swimming during the yolk-sac stage [total length (TL) interval = 2.27–3.005 mm] and feeding during the preflexion stage (TL interval = 3.007–5.60 mm) by promoting the accelerated growth of tail (post anal) and head, respectively. In the flexion stage (TL interval = 5.61–7.62 mm) a change in growth coefficients of most body segments compared to the previous stage was detected, suggesting a shift in growth priorities. Finally, in the postflexion stage (TL interval = 7.60–15.48 mm) a clear tendency to isometry in most body segments was observed, suggesting that growth priorities have been fulfilled and the larvae will initiate with the transformation into a juvenile. These results provide a framework of the larval growth of L. peru in culture conditions which can be useful for comparative studies with other species or in aquaculture to evaluate the changes in larval growth due to new conditions or feeding protocols.     

Growth and feeding of juvenile pike <Emphasis Type="Italic">Esox lucius</Emphasis> (Esocidae) of different hatching dates during its first months of life

Groups of fingerlings of the pike Esox lucius, that hatched from the eggs of the same female at the beginning and end of hatching are compared. It was found that larvae of pike of the beginning of hatching passed to external feeding earlier. In the period of mixed and exogenous feeding, they not only grew, but also developed more rapidly than larvae from the same brood. It was shown that pike juveniles of the end of hatching were characterized by a retarded development and growth in the first weeks of life (until reaching a length of 100 mm and a weight of 7 g). In the second month of life, specimens of this group began to feed intensively, grow, and according to body length and weight, reached pike juveniles of the beginning of hatching. Pike fingerlings of the end of hatching were characterized by compensation growth that was manifested at the excess of fish food (at cultivation in separate aquariums when the inhibitory effect of large fish on the growth of small fish was excluded) and in ponds where fish food availability was considerably lower.     

Effects of heating on growth and condition of pikeperch (Lucioperca lucioperca) in lowland ponds created by sand extraction

The growth rates of pikeperch (Lucioperca lucioperca L.) originating from two lowlands ponds in the north of Belgium, one of which is heated by the effluents of power plants, were compared by means of scalimetry and operculometry. The overall condition of the fish in both ponds was also investigated. The pikeperch grew significantly faster in heated water, although overall condition was comparable. Seasonal variations resulted in the heated pond arriving at a temperature higher than the optimum.     

Early ontogeny of the mackerel icefish, Champsocephalus gunnari, in the southern Scotia Arc

During the early ontogeny of fishes, the timing and duration of key events such as larval hatching and the switch from endogenous to exogenous feeding largely determine the offspring viability and survival. The aim of the present study was to investigate the life history traits of the early larvae of the mackerel icefish, Champsocephalus gunnari, collected in summer south of the South Shetland Islands in the Bransfield Strait and north of Elephant Island. Through the analysis of sagittal otolith microstructure, we assessed the timing and duration of egg incubation, larval hatching, first exogenous feeding, rate of yolk resorption and body growth rate. Compared to populations living further north (i.e. around South Georgia and Kerguelen Islands), mackerel icefish in the southern Scotia Arc exhibits longer egg incubation (lasting 90–120 days from winter to summer) and delayed hatching time spread over a relatively short period lasting 26 days between January and February. The first exogenous feeding takes place between 13 and 24 days after hatching still in the presence of the yolk-sac, indicating a prolonged mixed feeding afterward. The specific growth rate or daily percentage change in size (G) was 1.9 % SL day^?1, corresponding to a daily growth rate at mean size of 0.31 mm day^?1. While showing significant differences in early life history traits across their geographical distribution, C. gunnari populations share a common strategy, spawning a small number of large eggs that hatch in relatively large-sized larvae, at a time which may be independent of the timing of pack-ice retreat and onset of the production cycle.     

First feeding and subsequent growth performances in piscivorous larvae of Chinese perch Siniperca chuatsi (Perciforms: Sinipercidae)

The success of first feeding is influenced by many factors, such as prey availability, and is critical to subsequent larval growth performances. To test the advantages of prey exposure before complete yolk absorption in piscivorous larvae, feeding incidence and specific growth rate were longitudinally measured in Chinese perch Siniperca chuatsi larvae first fed at different ages. The results showed that Chinese perch larvae were able to capture live piscine prey at 4 DAH (days after hatching), 1 day before complete yolk absorption. The feeding incidence and specific growth rate were higher in larvae first fed at 4 DAH than in larvae first fed at 5 or 6 DAH. These results indicate that prey exposure experience can facilitate the onset of first feeding, and that successful exogenous feeding, even before complete yolk absorption, is important for growth performances of piscivorous fish larvae.     

Development of eggs and larvae of Stolephorus commersonnii and taxonomic key to fish eggs of the Clupeidae and Engraulidae off China

Fish eggs of successive stages of embryonic development, which were identified as belonging to specimens of Commerson's anchovy Stolephorus commersonnii through comparative molecular techniques, were collected from Leqing Bay, Zhejiang, China. Some eggs were reared artificially to obtain samples of successive developmental stages of larvae. The fertilized eggs of S. commersonnii are ellipsoidal and non-adhesive. The surface of the egg membrane is smooth and the perivitelline space is narrow. There is a single oil globule in the irregularly segmented yolk. Newly hatched larvae are transparent and devoid of pigments. Development of the larvae occurs in the following sequence: 8?h after hatching, the anus unfolds; 12?h after hatching, the pectoral fins emerge; 24?h after hatching, the liver and branchial arches emerge, and the alimentary canal differentiates into the oesophagus and intestinal canal; 30?h after hatching, the eyes become pigmented; 36?h after hatching, the upper and lower jaws become distinct; 42?h after hatching, the stellate melanophores emerge; 72?h after hatching, the postlarval developmental stage begins with the emergence of the dorsal fin. Based on the morphology of eggs and larvae of S. commersonnii, a taxonomic key to fish eggs of the Clupeidae and Engraulidae off China is established to provide an efficient and convenient way to identify the egg specimens. The fish eggs of the Clupeidae and Engraulidae off China could be identified to some extent by the buoyancy, shape and diameter of eggs, the number of layers in the egg membrane, the size of the perivitelline space, the number and diameters of oil globules, and the distribution of pigments. Meanwhile, their prelarvae could be identified by the number and diameters of oil globules, the distribution of pigments, the location of the anus and the number of myomeres.