Effect of live and dry food on rearing of tench (Tinca tinca L.) larvae under controlled conditions

In the current paper we present a method of rearing tench (<em>Tinca tinca</em> L.) larvae under controlled conditions, fed on dry food (Gemma and Perla) and Artemia nauplii or decapsulated cysts of Artemia. Tench larvae were obtained after artificial spawning by aid of Ovopel stimulation. Two experiments were conducted during which fish were divided into 4 groups (in duplicate) and placed in 30 dm3 glass fish tanks set up in a recirculating system. The fish were fed <em>ad libitum</em> and reared for 25 days. Larvae were fed exclusively (experiment 1) or after 10 days (experiment 2) of receiving <em>Artemia</em> nauplii with two types of compound feeds and decapsulated cysts of Artemia. The best growth rate was observed in the control group fed on Artemia nauplii and in the group offered decapsulated cysts in both experiments. The highest survival rate, over 96%, occurred in the control group. A twofold worse survival rate was obtained in the group fed exclusively on dry food. Applied transition schedule had significant effect on survival rate among treatments, however it did not influence the percentage of body deformations occurring in groups receiving compound feed only. The results obtained indicate the necessity of applying gradual transition from live food to compound feed and the improvement of feeding schedules in common tench culture

Optimal Monetary Strategies for Central and East European EU Candidates

The author argues that the high real interest rate policy persued in the Central and Eastern European Countries (CEEC) carries a risk of currency devaluation and recession when they join the European Monetary Union. Fear of demand-pull inflation has led the monetary authorities in the fast-growing CEEC to reduce the demand for credit by raising real interest rates, exceeding the interest parity relation with major EU markets. This policy has caused speculative capital inflows, distortion of capital allocation, real currency appreciation and trade deficits. Currency overvaluation will require a corrective devaluation via-a-vis the Euro during the final stages of accession to the EMU. Such a "last minute" correction is likely to destabilize CEEC banks and businesses by upsetting the balance between short-term foreign currency liabilities and long-term domestic assets. The author proposes that the CEEC EMU candidates adopt flexible inflation targeting instead of focusing on interest rates as a main disinflationary tool. This would assure accumulation of the proper amount of foreign currency reserves, reduce the current account deficit and ensure a smooth transition to the EMU. The new policy should be focused on defining and adopting a band of acceptable inflation rate targets and a "step down" path to alignment with the Euro.

Effects of photothermal manipulations on the artificial reproduction of barbel, Barbus barbus (Actinopterygii: Cypriniformes: Cyprinidae): a pilot study

The effects of photothermal manipulations on the artificial reproduction of female Barbus barbus (L.) (age 6+, 0.3–0.8 kg body weight) were studied under controlled conditions. The experiment was preceded by a 3-month period of wintering (Light/Dark hourly regime 9L : 15D–13L : 11D; temperature 8–12°C). The experiment commenced when the photoperiod was changed promptly from 11L : 13D to 14L : 10D. As the experiment progressed, the photoperiod gradually changed to 16L : 8D. After 50 days of photostimulation, water temperature was increased from 12 to 17°C within 24 h, and stabilized for the next 14 or 22 days. When photothermal stimulation was completed (65 or 73 days, respectively), fish were treated with mGnRH-based ovulating agent Ovopel. The ovulation rate amounted to 33% and 22%, respectively for the shorter and longer stimulation time (difference insignificant at P ≤ 0.05). Longer photothermal stimulation resulted in lower variability of latency time, higher relative weight of stripped eggs, and higher relative working fecundity. The undesirable effect was the triggering of oocyte resorption in 11% of females

Effects of temperature on body chemical composition and incidence of deformities in juvenile tench, Tinca tinca (Actinopterygii: Cypriniformes: Cyprinidae), fed a commercial dry diet and/or natural food

Background. Water temperature is a major factor regulating fish metabolism. It can influence body chemical composition and the incidence of body deformities. The latter often develop in farmed fish and this issue is currently emerging as a serious problem for aquaculture. Determining the effects of water temperature on body chemical composition and fish body deformities is an important subject for research in fish biology and nutrition, and aquaculture. The presently reported study was conducted using juvenile tench, Tinca tinca (Linnaeus, 1758), an important aquaculture species in Europe. Two hypotheses were tested: 1) temperature can significantly influence body chemical composition and the incidence of body deformities in fish; 2) the effects of temperature on fish depend on their diet. Materials and methods. Fish, with an initial total length of 28.4 ± 2.7 mm and body weight of 0.24 ± 0.07 g, were reared at 20, 23, and 26°C and fed dry feed Aller Futura (Aller Aqua, Denmark) only, or a combination of this feed and natural food (frozen larvae of Chironomidae) in a 3 ÷ 2 ratio of dry matter, or the natural food alone. The duration of the experiment and the daily food rations were adjusted to the experimental temperatures based on a correction factor, q, of 1.000, 0.779, or 0.609, respectively. The experiment duration was 92, 72, or 56 days for the respective temperatures. Results. Body deformities occurred in all groups of fish fed solely or partially with the dry diet (21.5%–89.5%). The incidence of deformities was directly proportional to the temperature and the content of dry feed in the diet reaching the maximum in fish fed exclusively the dry diet at 26°C. Water temperature and fish diet influenced body chemical parameters (moisture, protein, lipid, ash, Ca, P, Mg, Ca ÷ P, Mg ÷ P), but water temperature did not have a significant effect on whole-body P content. Conclusion. Water temperature proved to significantly influence fish chemical body composition and the incidence of body deformities in fish fed dry diet. The major factor that caused fish P deficiency, and resulted in low body ash content and body deformities, was insufficient bioavailability of P in the dry diet. Water temperature appeared to only modify P deficiency symptoms in fish