J.D. Celada

Reproduction of astacid crayfish in captivity—current developments and implications for culture, with special reference to Ireland and Spain

Summary Astacid crayfishes, native to western Eurasia and western North America, are iteroparous and long-lived (6–12 years), reaching final sizes of about 30–500 g and 90–200 mm total length, depending on species. While economically valuable, their low fecundity and slow growth makes economic aquaculture difficult. In Spain and Ireland the relatively small native white-clawed crayfish Austropotamobius pallipes (Lereboullet) carries around 70 eggs for 8–9 months and reaches first maturity at 3–4 years and 50 mm total length. The larger signal crayfish Pacifastacus leniusculus Dana, introduced to Europe from California, matures at about 70 mm and 2 years and carries some 200 eggs for 8 months. A. pallipes alone occurs in Ireland; both species in Spain. We have investigated fecundity, oviposition and subsequent egg development of diese species in field and laboratory and developed strategies to maximize egg survival in artificial incubators. Temperature manipulations may be used to maximize juvenile surviva...

Response of juvenile freshwater crayfish (Pacifastacus leniusculus Dana) to several fresh and artificially compounded diets

Abstract Three artificially compounded diets (purified diet, compound feed, and crab protein crustacean reference diet) and several fresh diets were tested under laboratory conditions in an attempt to improve survival and growth rates of juvenile freshwater crayfish ( Pacifastacus leniusculus ). The highest survival obtained was 44.44% after 80 days of test. Fresh aquatic plant material, when added to artificially compouned diets, improved growth and slightly increased survival, and the animals became more pigmented. Juveniles held singly, rather than in groups, achieved higher survival rates. The results with juvenile P. leniusculus have been related to those obtained in research with other crustaceans.

The possibilities for artificial incubation of white-clawed crayfish (Austropotamobius pallipes Lereboullet) eggs: comparison between maternal and artificial incubation

Abstract The development of artificial incubation techniques for freshwater crayfish eggs and the incorporation of these practices to the working scheme in production centres would have numerous advantages. This study evaluates the efficacy of one particular device, designed by this research group, for the artificial incubation of white-clawed crayfish ( Austropotamobius pallipes ) eggs. Comparisons between maternal and artificial incubation demonstrated the suitability of the tested system for artificial incubation for eggs of this species, during a period of 42% of the total duration of the embryonic development. Overall survival rate to juvenile stage 2 was significantly higher ( P

Artificial incubation of crayfish eggs ( Pacifastacus leniusculus Dana) from early stages of embryonic development

Abstract Three experiments on artificial incubation of crayfish eggs ( Pacifastacus leniusculus Dana) were carried out under different thermal regimes using a specially designed incubator tested in previous trials. Each treatment included a period of low temperature of different duration. Three flow rates were used in each experiment: 3.0, 1.5 and 0.5 l/min. In all cases the eggs were detached from females at three phases of embryonic development: beginning of gastrulation (mean degree days 230, 18 days after spawning); embryo between closing of the blastopore and appearance of mandibular rudiments (mean degree days 365); and embryo with naupliar appendages (mean degree days 480). The results showed that it is possible to auain acceptable juvenile stage 2 survival rates (58.9%) even though eggs were detached at the earliest embryonic phase (beginning of gastrulation). In the experimental incubator, flow rates could be reduced to 0.5 l/min without decreasing survival. The highest survival to juvenile stage 2 (72.1%) was obtained by delaying egg removal until the appearance of naupliar appendages, and using a thermal treatment of 15.5 ° ± 1 °C preceded by a 3-week period of low temperature (5 ° ± 1 °C) commencing at stripping time.

Effects of management on survival and growth of Stage 2 juvenile freshwater signal crayfish (Pacifastacus leniusculus Dana) under laboratory conditions

Abstract Four experiments were carried out in order to evaluate survival and growth rates of Stage 2 juvenile Pacifastacus leniusculus under different management conditions: effects of offspring origin (artificial incubation, maternal incubation under laboratory conditions and maternal incubation under natural conditions), of different shelter availability, of water circulation systems (partially re-circulated and full flow-through), and effects of certain flow rates. Juveniles kept singly, rather than in groups, had higher survival rates. However, when juveniles were in groups, they showed faster growth. Offspring from artificial incubation did not show significant differences in survival and growth rates from those from maternal incubation. The addition of pebbles as shelter did not improve survival rates. The use of a full flow-through system allowed significantly higher survival and growth rates. A flow rate of 1 l/min improved the survival rate in comparison with 6 l/min, but not growth. In general, the highest mortality occurred during the first 40–60 days of the experiments, although a great variation in the final results was observed.

Effects of thermic manipulation throughout egg development on the reproductive efficiency of the freshwater crayfish (Pacifastacus leniusculus Dana)

Abstract The improvement of reproductive efficiency of freshwater crayfish, Pacifastacus leniusculus Dana by means of periods of low temperature treatment of different duration was studied. The best rate of production of stage 2 juveniles in relation to the initial number of eggs (82.18%) corresponded to 4 weeks of low temperature starting at phase IX (embryo with naupliar appendages). The period between the appearance of eye pigments and the first post-embryonic molt is the most critical for reproductive efficiency.

Effects of shelter type and food supply frequency on survival and growth of stage-2 juvenile white-clawed crayfish (Austropotamobius pallipes Lereboullet) under laboratory conditions

Two shelter substrates (fibre-cement sheets and PVC pipes) and two foodsupply frequencies (once and twice daily) were tested on white-clawed juvenilecrayfish in two separate experiments performed under laboratory conditions.Juvenile crayfish were maintained at an initial density of 50 animals persquaremetre in a flow-through system and fed on fresh Daphniapulex and a feed formulated for rainbow trout. After 120 days,highersurvival (50.5%), but lower growth, was obtained when fibre-cement sheets wereprovided as shelter. A comparison between food supply frequencies showed abetter survival rate (60.5%) when food was provided twice per day althoughtherewere no differences in growth after 80 days of trial. The number of animalswith chela autotomy is positively correlated (r between 0.33 and 0.48 depending ontreatments) with decreases in survival rate. The combination of adequate shelterand frequency of food supply could reduce the agonistic behaviour of juvenilecrayfish.

Effects of different thermal treatments during embryonic development on the artificial incubation efficiency of crayfish (Austropotamobius pallipes Lereboullet) eggs. Control of the embryogenetic duration and implications for commercial production

Summary The development and improvement of artificial incubation techniques for freshwater crayfish eggs and their incorporation into the working schedule of breeding centres is of great interest for commercial production. Factors such as the water circulation system, flow rate, thermal treatment, etc., could strongly influence the success of the process. The present study attempts to test the possible influence of one of these variables, the thermal regime, on both the duration of embryonic development and the efficiency rates obtained in the artificial incubation of white-clawed crayfish (Austropotamobius pallipes) eggs. Four different thermal treatments were tested (three of them included a period at low temperature: 4°-5°C). Survival rates to juvenile stage 2 were similar in the four cases, ranging between 66.7 and 72.7%. We conclude that water cooling (an expensive management procedure) is not necessary in astacid breeding centres provided that egg development takes place at moderately low temperatur...

EFFECTS OF DIFFERENT THERMAL TREATMENTS ON THE MATERNAL INCUBATION EFFICIENCY OF THE ASTACID CRAYFISH AUSTROPOTAMOBIUS PALLIPES (LEREBOULLET,1858) UNDER CONTROLLED CONDITIONS

[Adult freshwater crayfish, Austropotamobius pallipes, were maintained in the laboratory in such a way that mating, spawning, and maternal egg incubation took place under controlled conditions. This allowed to obtain data on reproductive biology from spawning to stage 2 juveniles. Three different thermal treatments were tested during embryonic development: a constant temperature of 11°C, ambient room temperature, and the incorporation of a cold period (3 weeks at 4°C). Females used in the three treatments tested were of a similar size (Mean Carapace Length ± Mean Standard Error = 34.06 ± 0.11 mm). Stage 2 juvenile production was not significantly different among the three regimes applied. The highest mean number of stage 2 juveniles per female (23) was obtained in animals maintained at constant temperature. Statistical differences were not detected, neither with regard to reproductive efficiency, in which the best value (33%) again was obtained at constant temperature. Although thermic manipulation thus did not provide better results as regards efficiency, this practice allowed to obtain stage 2 juveniles in different batches, spaced in time. Cangrejos de rio de la especie Austropotamobius pallipes se mantuvieron en laboratorio durante la fase reproductiva. De esta forma, apareamiento, puesta y todo el proceso de incubacion maternal de los huevos tuvieron lugar bajo condiciones controladas. Esto permitio la obtencion de datos biologicos reproductivos desde la puesta hasta el segundo estado juvenil. Durante el desarrollo embrionario, se ensayaron tres tratamientos termicos: temperatura constante de 11°C, temperatura ambiente y la inclusion de un periodo frio (3 semanas a 4°C). Las hembras presentaron una talla similar en los tres tratamientos (Longitud Media de Cefalotorax ± E.S.M. = 34,06 ± 0,11 mm). La produccion de juveniles estado 2 no mostro diferencias significativas entre regimenes termicos, aunque el numero medio mas alto obtenido por hembra (23) correspondio a animales mantenidos a temperatura constante. Igualmente, tampoco fueron detectadas diferencias significativas en los resultados de eficiencia reproductiva. El valor mas elevado (33%) fue obtenido con temperatura constante. Aunque la manipulacion termica no mejoro significativamente los resultados de eficiencia, esta practica permite la obtencion de juveniles estado 2 en diferentes lotes dentro de amplios margenes de tiempo., Adult freshwater crayfish, Austropotamobius pallipes, were maintained in the laboratory in such a way that mating, spawning, and maternal egg incubation took place under controlled conditions. This allowed to obtain data on reproductive biology from spawning to stage 2 juveniles. Three different thermal treatments were tested during embryonic development: a constant temperature of 11°C, ambient room temperature, and the incorporation of a cold period (3 weeks at 4°C). Females used in the three treatments tested were of a similar size (Mean Carapace Length ± Mean Standard Error = 34.06 ± 0.11 mm). Stage 2 juvenile production was not significantly different among the three regimes applied. The highest mean number of stage 2 juveniles per female (23) was obtained in animals maintained at constant temperature. Statistical differences were not detected, neither with regard to reproductive efficiency, in which the best value (33%) again was obtained at constant temperature. Although thermic manipulation thus did not provide better results as regards efficiency, this practice allowed to obtain stage 2 juveniles in different batches, spaced in time. Cangrejos de rio de la especie Austropotamobius pallipes se mantuvieron en laboratorio durante la fase reproductiva. De esta forma, apareamiento, puesta y todo el proceso de incubacion maternal de los huevos tuvieron lugar bajo condiciones controladas. Esto permitio la obtencion de datos biologicos reproductivos desde la puesta hasta el segundo estado juvenil. Durante el desarrollo embrionario, se ensayaron tres tratamientos termicos: temperatura constante de 11°C, temperatura ambiente y la inclusion de un periodo frio (3 semanas a 4°C). Las hembras presentaron una talla similar en los tres tratamientos (Longitud Media de Cefalotorax ± E.S.M. = 34,06 ± 0,11 mm). La produccion de juveniles estado 2 no mostro diferencias significativas entre regimenes termicos, aunque el numero medio mas alto obtenido por hembra (23) correspondio a animales mantenidos a temperatura constante. Igualmente, tampoco fueron detectadas diferencias significativas en los resultados de eficiencia reproductiva. El valor mas elevado (33%) fue obtenido con temperatura constante. Aunque la manipulacion termica no mejoro significativamente los resultados de eficiencia, esta practica permite la obtencion de juveniles estado 2 en diferentes lotes dentro de amplios margenes de tiempo.]

Duration of egg storage at different temperatures in the astacid crayfish Pacifastacus leniusculus: critical embryonic phase

Abstract The critical phase that would limit duration of egg storage in the astacid crayfish Pacifastacus leniusculus was investigated. Weekly monitoring was conducted during an 84-day period of storage at three different constant temperatures (15.5±1, 10.5±1.5 and 4±0.5 °C). After artificial incubation, stage 2 juveniles were only obtained from the lowest storage temperature, the sole treatment in which eggs did not reach the critical embryonic stage by the end of the storage. This limiting stage occurs at phase XII (embryo with pulsating heart) when embryogenesis of stored eggs ceased and phase XIII (eyed stage) was not reached. Eggs were also stored at a constant refrigeration temperature (4±0.5 °C) for periods ranging from 84 to 126 days. Mean survival rates to juvenile stage 2 were acceptable (approximately 50%) and different batches of juveniles were obtained over a 3-month period, depending on the duration of storage. The combined use of storage and artificial incubation techniques could have important applications to the development of astacid crayfish culture.