Dariusz Kucharczyk

A model system for keeping spawners of wild and domestic fish before artificial spawning

Abstract In this paper we present a system with controlled temperature and photoperiod for keeping breeders before their artificial spawning and give a general outline of its use. The advantages of this system were: utility, small area in which it was placed, wide range of temperature and photoperiod, possibility of worked tanks together or alone and in open, closed or semi-closed systems, cheap to construct and with low running costs. Additionally, this unit was tested for artificial spawning for several wild and domestic European cyprinid and percid fish species, as well as burbot, not uncommonly in different periods than the time of their natural spawning.

Effect of temperature on embryonic and larval development of bream (Abramis brama L.)

Influence of water temperature on embryonic and larval development of bream (Abramis brama L.) was stdied. Eggs of bream were incubated at eight constant water temperatures between 13.2 and 26.8°C. The temperature of 21.1°C gave highest hatching success, with no abnormalities in the eleutheroembryos and lowest mortality observed between eyed egg stage and the time of hatching. Developmental rate increased with increasing temperature. Duration of embryonic development (y; hours) decreased with increasing incubation temperature (x; °C) according to the formula: y=910.1−65.88 x+1.318 x2. Larvae were reared at eight constant temperatures ranging from 13.5 to 34.0°C. The instantaneous growth rate in wet weight increased with increasing test temperature from 13.5 to 29.9°C, and then decreased at higher temperatures. Individual growth of fish and biomass production rate were highest at 27.9°C. This temperature is considered optimal when food availability and photoperiod are no limiting factors.

Cryopreservation of Sperm from Asp Aspius aspius

Abstract This is the first report on sperm cryopreservation for the cyprinid species asp Aspius aspius. Fish were captured from wild stock and kept under controlled conditions. Ovulation and spermiation were induced with hormonal treatment. Six simple carbohydrate-based extenders supplemented with 10% DMSO were tested for sperm cryopreservation. The most efficient extenders were 0.3 M sucrose, 0.6 M sucrose, and 0.3 M glucose. They resulted in survival to the eyed stage of 62 ± 4%, 59 ± 5%, and 49 ± 4%, respectively, expressed as a percentage of control survival, which was 58 ± 6%. The presence of chicken egg yolk in extenders significantly decreased cryopreservation success.

New Experimental Incubation Unit for Eggs of the Perch Perca fluviatilis

Abstract A simple and inexpensive incubation chamber system for eggs of Eurasian perch Perca fluviatilis is described, along with a general outline for its use. The unit was constructed from two wooden frames, and had a plastic mesh bottom. A system of glass barriers was placed in the bottom frame and formed a network of 10–18 individual chambers in two columns. The unit was placed at an angle inside a glass aquarium during egg incubation. There were no significant differences in percentage of eyed eggs incubated at different locations in the unit.

Ploidy Level Determination in Genetically Manipulated Northern Pike Based on the Number of Active Nucleoli per Cell

Abstract Silver-staining of cell preparations followed by counting of the mean number of active nucleoli per cell enabled determination of the ploidy level in genetically manipulated northern pike Esox lucius. Haploid pike resulted from activation of eggs with sperm irradiated with ultraviolet light, and triploid specimens were obtained by applying high-temperature shock. Cells of haploid individuals had one (almost 100% of cells examined) or, sporadically, two nucleoli. Depending on the specimen, mean number of nucleoli per nucleus ranged from 1.0 to 1.06. In diploid fish, the mean number of active nucleoli per cell ranged from 1.58 to 1.81. In triploids, the mean ranged from 2.08 to 2.46. Positive identification of ploidy level in northern pike required examination of up to 40 cells per individual, as determined by the regression analysis. The method required a very small amount of any kind of tissue, enabling determination of ploidy level in juvenile fish without sacrificing them.

Ontogeny of feeding habits in northern pike, Esox lucius (Esocidae), larvae reared in illuminated cages

Feeding habits of larval pike, Esox lucius L., was studied at three stocking densities in illuminated cages. Developmental patterns of larval feeding on Zooplankton were independent of larval density. During the first week of rearing, larvae fed mainly on rotifers, small cladocerans, nauplii and copepodites of Cyclopidae. After second week they selected small cladocerans (Bosmina spp.), and adult copepods (Cyclops and Mesocyclops spp.). Higher stocking densities resulted in lower survival and growth rates. This was presumably due to increased competition for food, as the composition of the diet was independent of stocking density.

Development of cannibalism in larval northern pike, Esox lucius (Esocidae)

Abstract The development of cannibalism of northern pike (Esox lucius) larvae was studied under controlled conditions. Pike larvae were reared in six glass, 50–1 aquaria at three stocking densities: 440, 2 200 and 4 400 larvae per aquarium. Fish were fed ad libitum with Artemia nauplii and sieved Zooplankton. After 4, 8 or 12 days of rearing, pike larvae were anaesthetised and measured for total length (TL) and body weight (BW). Lowest survival and fish size were noted at the highest stocking density. The frequency of all cannibalistic attacks decreased in the order: highest > middle > lowest density; the frequency of successful attacks (expressed as the number of injured sibling fish) decreased, however, in opposite order.

Use of a Floating Pump to Collect and Transfer Live Zooplankton as Food for Percid Larvae Reared in Net Cages

Abstract A system for transfering live natural zooplankton to net cages containing percid larvae is described. The construction of this system is based on a net cage system routinely used for coregonid larvae. The pump transferred zooplankton in proportion to zooplankton density in a lake and can be adjusted depending on fish size and stocking density. A floating pump transferred up to 55% of available zooplankton to a rearing cage. The percentage of zooplankton groups in the control cage and in the pumping water was similar. Zooplanktonic organisms were not damaged by the pump.

Feeding habits of larval Eurasian perch, Perca fluviatilis (Percidae)

Abstract Feeding during the development of Eurasian perch (Perca fluviatilis) larvae was studied in situ in cylindrical cages. Initially perch larvae were maintained in cages, 0.2 mm of mesh size. The initial stocking density was 7 000 larvae per cage. Fish were fed with Zooplankton and after 17 days were transplanted to cages with a larger mesh size (1.2 mm). Development was observed for additional 17 days. Larval survival was about 25% and 65% for the initial and secondary rearing, respectively. Perch larvae ate initially rotifers and later ate nauplii and copepodites. Cladocera was the dominant food item in the diet of perch at the conclusion of our observations.

FEEDING HABITS OF ASP ASPIUS ASPIUS LARVAE (CYPRINIDAE) IN LAKE MAROZ, POLAND

Abstract Feeding development of asp Aspius aspius larvae was studied during rearing in Lake Maroz (north Poland) illuminated cages. The initial rearing occurred under controlled conditions in a hatchery. After four and half weeks, reared fish (total length 14.8 mm) were transported to cages maintained in a lake. The initial stocking density was about 8 830 fish per cage. All experiments were replicated three times. Fish were fed Zooplankton collected during night with a light placed over the cages. During the seven weeks rearing period in lake cages survival was relatively high (over 72%). The observed feeding development pattern was as follow: rotifers, nauplii, copepodites, adult Copepoda, then adult Cladocera. The largest asp larvae also ate imago forms of insects.