Artificially fertilized eggs and yolk‐sac larvae of a freshwater tropical/subtropical fish Clarias gariepinus receiving no external food were incubated at 22, 25 and 28° C until full yolk resorption. Developmental time, size and matter composition (CHNS‐O Analyzer and ashing) were assessed at egg fertilization, hatching and yolk resorption; respiration was measured every 4–5 h. The course of acceleration of C. gariepinus embryonic developmental rate with temperature (Q10dev) was compared over the temperature range to those of Cyprinus carpio and Oncorhynchus mykiss; they differed greatly, but were similar when compared on the basis of effective temperatures specific to each fish. Specific growth rates for energy (88, 150 and 183% per day at 22,25 and 28° C, respectively) as well as the conversion efficiencies of egg energy (64, 71 and 68%, respectively) and protein (71, 78 and 76%, respectively) in C. gariepinus larval tissues were higher than those known for the endogenous feeding period of coldwater and temperate fish species. In C. gariepinus at the end of yolk resorption, the carbon percentage and caloric values of dry weight, size (in terms of dry matter, minerals, protein and energy per larva) and transformation efficiencies were lowest at 22° C, highest at 25° C and had slightly decreased at 28° C. A tentative mechanism which leads to the positive or negative response of body size to temperature over the viable temperature range is defined.

The aim of this study was to assess the biochemical profile of tench blood plasma during preand postspawning period under the conditions of hormonally-induced artificial reproduction. A total of 59 females and 27 males were examined during the postspawning period of 1999 and 52 females and 25 males were examined during the prespawning period of 2000, as well as 48 females after reproduction. Biochemical indices determined in blood plasma were as follows: cortisol, glucose, total protein (TP), triacylglycerols (Tcg), cholesterol (Chol), transaminases (ALT and AST), creatine kinase (CK), alkaline phosphatase (ALP) and electrolytes (Na). In females in the pre-spawning period, higher values of TP (P < 0.05) and Tcg (P < 0.01) were found compared to males. Immediately after reproduction, males had higher TP (P < 0.01) and Chol (P < 0.01) than females. No significant sex-related differences were found in other indices under study. Higher values of glucose (P < 0.01), Tcg (P < 0.01), Chol (P < 0.05), AST (P < 0.01) and ALP (P < 0.01) were found for females after reproduction in June compared to values found in April, i.e. two months prior to reproduction. Differing water temperature (10.3 °C in April; 22 °C in June) associated with metabolic rate also played an important role. Induction of ovulation by GnRH synthetic analogue and carp pituitary was not successful in all females. However, between the spawned and unspawned female fish, differences were found in glucose concentration (P < 0.01) but non-significant differences were recorded for other biochemical indices. The blood plasma biochemical profile enabled to assess the state of internal milieu of broodstock during the reproduction period.

This study investigated the feasibility of using clove oil, 2-phenoxyethanol, or Propiscin as an alternative to tricaine methane sulphonate (MS 222) as a ¢sh anaesthetic, particularly in regard to reducing ¢sh stress. The biochemical blood pro¢les of perch Perca £uviatilis L. anaesthetized with either MS 222 (100 mg L À 1 ), clove oil (33 mg L À 1 ), 2-phenoxyethanol (0.40 mL L À 1 ) or Propiscin (1.0 mL L À 1 ), and a non-anaesthetized control group were compared. Biochemical pro¢les were determined from blood samples collected before treatment in controls. For each anaesthetic tested, ¢sh were divided into two groups, one sampled immediately after 10-min anaesthesia and a second, sampled 24 h after 10-min anaesthesia. The values determined in the present study suggested that internal organs and tissues of perch were slightly altered by MS 222, clove oil and 2-phenoxyethanol anaesthesia, but not by Propiscin anaesthesia.

Summary Natural diets of tench (Tinca tinca L.), carp (Cyprinus carpio L.) and bigmouth buffalo (Ictiobus cyprinellus Val.) were studied to determine food competition among them in polyculture stocks of two different densities. Tench diet consisted mainly of zooplankton (43.8%) and bottom sediments (21.2%). In contrast, carp diet consisted mainly of bottom items including plant debris and detritus (68.8%), which dominated over zooplankton (19.1%). In bigmouth buffalo, most food bulk comprised zooplankton (80.7%). Thus, the resulting food competition (i.e. similarity) was most pronounced between tench and carp (60.8%) and between tench and bigmouth buffalo (47.4%). When comparing growth performance of the three cultured species, the ratios between stocking and harvesting size were: in normal stocking density (392 kg ha−1) 1.72, 3.67 and 2.13, and in doubled stocking density (777 kg ha−1) 1.07, 2.33 and 2.16 in tench, carp and bigmouth buffalo, respectively.

Gonadotropin-releasing hormone in Cyprinidae as in other Vertebrates functions as a brain signal which stimulates the secretion of luteinizing hormone from the pituitary gland. Two forms of gonadotropin-releasing hormone have been identified in cyprinids, chicken gonadotropin-releasing hormone II and salmon gonadotropinreleasing hormone. Hypohysiotropic functions are fulfilled mainly by salmon gonadotropin-releasing hormone. The only known factor having an inhibitory effect on LH secretion in the family Cyprinidae is dopamine. Most cyprinids reared under controlled conditions exhibit signs of reproductive dysfunction, which is manifested in the failure to undergo final oocyte maturation and ovulation. In captivity a disruption of endogenous gonadotropinreleasing hormone stimulation occurs and sequentially that of luteinizing hormone, which is indispensible for the final phases of gametogenesis. In addition to methods based on the application of exogenous gonadotropins, the usage of a method functioning on the basis of hypothalamic control of final oocyte maturation and ovulation has become popular recently. The replacement of natural gonadotropin-releasing hormones with chemically synthesized gonadotropin-releasing hormone analogues characterized by amino acid substitutions at positions sensitive to enzymatic degradation has resulted in a centuple increase in the effectiveness of luteinizing hormone secretion induction. Combining gonadotropin-releasing hormone analogues with Dopamine inhibitory factors have made it possible to develop an extremely effective agent, which is necessary for the successful artificial reproduction of cyprinids.Keywords: reproductive dysfunction; ovulation; luteinizing hormone; gonadotropin-releasing hormone; gonadotropin; dopamine; dopamine antagonist; cyprinids List of abbreviations DA = dopamine; DI = dopamine antagonist; EU = European Union; GnRH = gonadotropin-releasing hormone; GnRHa = gonadotropin-releasing hormone analogue; cGnRH-II = chicken gonadotropin-releasing hormone II; mGnRH = mammalian gonadotropin-releasing hormone; sGnRH = salmon gonadotropin-releasing hormone; GPCR = G-protein coupled receptor; LH = luteinizing hormone; MRL = minimum residual limit; IM = intramuscular injection; IP = intraperitoneal injection; PCC = pericardial cavity injection; IV = intravenous injection

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Effect of incubation temperature (range: 9-36 °C; interval: 3 °C) on artificially propagated weatherfish (Misgurnus fossilis) early ontogeny (during interval from egg fertilization to the finish of hatching) was investigated. Both, the amplitude of the incubation period (evaluated in four crucial moments), the total hatching period duration was inversely proportional to the incubation temperature and ranged from 17.5 days at 9 °C to 1.8 days at 24 °C (expressed at H 50 ) or from 137 hours at 9 °C to 9 hours at 24 °C, respectively. There were no influence of rising temperature on the total length of newly hatched larvae (T L = 4.23-4.67 mm), in contrast to negative correlation with developmental stage (9-18 °C: stage 37; 21-24 °C: stage 36), i.e. the length might determine the age at hatching, rather than the age at hatching determines the hatching length. The thermal tolerance range in term of survival lies between 9 and 24 °C (the thermal optimum 15-24 °C, i.e. weatherfish is a warm-mesothermic species). Temperatures above 24 °C (in our study 27-36 °C) are considered the lethal temperatures already during embryonic period. It is highly recommended to distinguish an impact of suboptimal temperatures 9-12 °C on development during explored interval only, in contrast to possible other effect of these lower temperatures in context of the whole early ontogeny. RÉSUMÉEffets de la température sur les premiers stades de vie de la loche d'étang, Misgurnus fossilis (L. 1758) L'effet de la température d'incubation (gamme : 9-36 °C, intervalles : 3 °C) sur les premiers stades ontogéniques de loches d'étang (Misgurnus fossilis) (de la fécon-dation à la fin de l'éclosion) a été étudié. La durée de la période d'incubation (évaluée à quatre moments clés) et la durée de la période d'éclosion des oeufs d'un lot sont inversement proportionnelles à la température d'incubation et s'étalent de 17,5 jours à 9 °C à 1,8 jour à 24 °C (pour l'indice H 50 ) et de 137 heures à 9 °C à 9 heures à 24 °C, respectivement. Il n'y a pas d'influence d'une élévation de température sur la longueur totale des larves à l'éclosion (T L = 4,23-4,67 mm), alors qu'il y a une corrélation négative avec le stade de développement (9-18 °C : stade 37 ; 21-24 °C : stade 36), i.e. la longueur semble déterminer l'âge à l'éclo-sion, plutôt que l'âge à l'éclosion déterminerait la longueur à l'éclosion. La gamme

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