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With the aim of preserving and increasing endangered stocks of white-clawed crayfish, research on juvenile production has been carried out. Advantages in application of newly developed techniques of egg storage, transport and artificial incubation techniques are discussed. Eggs can be removed from maternal pleopods during the early stages of embryonic development and placed in artificial incubation devices. This practice avoids egg losses caused by aggressive contacts, female disease or death and the production of stage-2 juveniles in different batches by means of temperature manipulation. Furthermore transmission of pathogens from broodstocks to offspring can be minimised. Egg storage and transport have some advantages in the artificial reproduction of crayfish. Firstly, embryonic development continues under storage conditions and thus water and human effort can be saved during this period. Temperature plays an important role on both efficiency rates and duration of embryogenesis. Secondly, egg transport could facilitate restocking programs, as there is no need to move berried females to other habitats. To sum up, the combined use of artificial incubation and storage/transport techniques could have important applications to the development of astacid crayfish culture.

The effects of osmolality and accidental urine contamination on spermatozoa velocity and motility were studied, combined with an examination of the biological characteristics of stripped and testicular sperm. Analysis of Northern pike sperm showed higher ionic concentrations of Na+ (123±9 mM), Cl- (127±7 mM), and K+ (35±5 mM) in the seminal fluid of testicular sperm (TS), than in that of stripped sperm (SS): Na+ (116 ±9 mM), Cl- (116 ± 7 mM) and K+ (25 ± 4 mM). Highest osmolality of seminal fluid was observed in TS with a value of 358 ± 77 mOsmol kg-1 compared with 273 ± 21 mOsmol kg-1 for SS and 68 ± 36 mOsmol kg-1 for urine. A significantly higher spermatozoa concentration was observed in TS (34 ± 5 x 109 ml-1) than in SS (23 ± 4 x 109 ml-1). Spermatozoa concentration per male and per kg body weight was 22 ± 17 x 109 for TS and 18 ± 2 x 109 for SS, respectively. Both TS and SS showed significantly higher spermatozoa velocities and motilities after dilution in urine than after dillusion in distilled water during the activity period. In conclusion, the results obtained from the present study provide information on northern pike sperm physiology that be used to improve sperm management efficiency for this species. [ABSTRACT FROM AUTHOR]

The effects of osmolality and accidental urine contamination on spermatozoa velocity and motility were studied, combined with an examination of the biological characteristics of stripped and testicular sperm. Analysis of Northern pike sperm showed higher ionic concentrations of Na+ (123±9 mM), Cl- (127±7 mM), andK+ (35±5 mM) in the seminal fluid of testicular sperm (TS), than in that of stripped sperm (SS): Na+ (116 ±9 mM), Cl- (116 ± 7 mM) and K+ (25 ± 4 mM). Highest osmolality of seminal fluid was observed in TS with a value of 358 ± 77 mOsmol kg-1 compared with 273 ± 21 mOsmol kg-1 for SS and 68 ± 36 mOsmol kg-1 for urine. A significantly higher spermatozoa concentration was observed in TS (34 ± 5 × 109 ml-1) than in SS (23 ± 4 × 109 ml-1). Spermatozoa concentration per male and per kg body weight was 22 ± 17 × 109 for TS and 18 ± 2 × 109 for SS, respectively. Both TS and SS showed significantly higher spermatozoa velocities and motilities after dilution in urine than after dillusion in distilled water during the activity period. In conclusion, the results obtained from the present study provide information on northern pike sperm physiology that be used to improve sperm management efficiency for this species. [ABSTRACT FROM AUTHOR]

With the aim to evaluate the effect of different intervals of degrees-days on egg production of tench (Tinca tinca L.), 480 breeders were kept in 15 x 10 x 1 m bare concrete tanks from February until July and fed on commercial feed. Males and females were held together under natural photoperiod and temperature conditions. Ovulation was hormonally inducted (LH-RHa) in three groups at different degrees-days (group I: 1090, group II: 1175 and group III: 1536). In the groups I and II, a mean of 88% of females was injected, obtaining a 98% of positive response, without significant differences in the egg production between both groups (10.7% body weight, b.w.). With 1536 degrees-days, percentages of injected and stripped females were significantly lower. First stripping yielded a total of 9332 g of eggs (8.3% b.w.). A second hormonal induction was evaluated in each group at 1900, 2047 and 2111 degrees-days respectively. A mean of 85% of the initial females of the three groups received a second hormonal treatment, obtaining a 92% of positive response, without significant differences in egg production among the groups. The second stripping yielded an egg production (598 g, 5.9% b.w.) significantly lower than the first one. Relating to males, semen was obtained without hormonal induction throughout 50 days and the positive response was around 90%. With the exception of eggs obtained in the first induction of group III (1536 degrees-days), where overripening process was detected, further mean fertilization (over 80%) and hatching rates (around 35%) support the good quality of eggs and sperm. This study showed that the advantages of the broodstock’s maintenance in small concrete tanks are not only easiness of handling and possibilities of yield prediction, but also a good egg production at higher densities than in big earthen ponds.

With the aim to evaluate the effect of different intervals of degrees-days on egg production of tench (Tinca tinca L.), 480 breeders were kept in 15 x 10 x 1 m bare concrete tanks from February until July and fed on commercial feed. Males and females were held together under natural photoperiod and temperature conditions. Ovulation was hormonally inducted (LH-RHa) in three groups at different degrees-days (group I: 1090, group II: 1175 and group III: 1536). In the groups I and II, a mean of 88% of females was injected, obtaining a 98% of positive response, without significant differences in the egg production between both groups (10.7% body weight, b.w.). With 1536 degrees-days, percentages of injected and stripped females were significantly lower. First stripping yielded a total of 9332 g of eggs (8.3% b.w.). A second hormonal induction was evaluated in each group at 1900, 2047 and 2111 degrees-days respectively. A mean of 85% of the initial females of the three groups received a second hormonal treatment, obtaining a 92% of positive response, without significant differences in egg production among the groups. The second stripping yielded an egg production (598 g, 5.9% b.w.) significantly lower than the first one. Relating to males, semen was obtained without hormonal induction throughout 50 days and the positive response was around 90%. With the exception of eggs obtained in the first induction of group III (1536 degrees-days), where overripening process was detected, further mean fertilization (over 80%) and hatching rates (around 35%) support the good quality of eggs and sperm. This study showed that the advantages of the broodstock’s maintenance in small concrete tanks are not only easiness of handling and possibilities of yield prediction, but also a good egg production at higher densities than in big earthen ponds.