This study demonstrated that individual fecundity of 34 migrating European female eels Anguilla anguilla increases linearly with body weight (BW) and total length (TL). The total individual fecundity of fish from 560 to 1960 g BW was between 981 x 10 3 and 6320 x 10 3 eggs, respectively. The mean relative individual fecundity equalled 2415 x 10 3 (± 524 x 10 3 ) per kg BW. The values of this parameter ranged from 1753 x 10 3 to 3224.5 x 10 3 kg -1 . Based on the results, it might be suggested that A. anguilla has lower total individual fecundity than New Zealand longfin eel (Anguilla dieffenbachii), American eel (Anguilla rostrata) and Japanese eel (Anguilla japonica) although it has one of the highest fecundity values per kg BW. Total fecundity was strongly depended from fat level in muscle (R 2 = 0.9523) and ovary (R 2 = 0.9531) as well as level of DHA content in ovary (R 2 = 0.8967) and muscle (R 2 = 0.6274) (N=10). There were no important relationship between total fecundity and protein level as well as in muscle and ovary.

A method for the mass marking of ide Leuciscus idus larvae by feeding them Artemia salina nauplii that were immersed in different solutions of alizarin red S, tetracycline hydrochloride and calcein was tested. The best quality marks were obtained after feeding fish for 4 days with nauplii that had been immersed in 200 mg l(-1) alizarin red S.

meiotic gynogenetic development of the rainbow trout (Oncorhynchus mykiss, walbaum 1792) was induced in the course of egg activation performed by the UV-irradiated homologous and heterologous (european grayling Thymallus thymallus linnaeus, 1758) spermatozoa. to recover diploidy in the gynogenetic zygotes, activated eggs were subjected to the high pressure shock in order to inhibit extrusion of the second polar body. gynogenetic rainbow trout progeny hatched from the eggs activated by the irradiated rainbow trout and grayling milt with similar hatching rates of 28.19% and 29.22%, respectively. however, gynogenetic rainbow trout produced with grayling semen had shown lower survival than gynogenotes provided with the homologous spermatozoa during two years of rearing. Viable hybrids are not produced between rainbow trout and grayling which ensured that fish obtained in this experiment were true gynogenetic progenies. A Robertsonian polymorphism characteristic for the rainbow trout from the studied strain was also observed among the gynogenetic specimens that exhibited diploid chromosome number ranging from 58 to 62 and stable chromosome arm number (fn= 104). no radiation-induced fragments of the paternal chromosomes were observed in the gynogenetic individuals. fish produced in both experimental variants were genotypic (XX) and phenotypic (gonads) females. The results confirmed that the gynogenetic protocol used in the present research is an efficient means of producing all-female gynogenetic rainbow trout stocks.

Despite large karyotype differences between parental species, the hybrid progeny of the sea trout (