Indoor Hatchery Research Articles

Selection among critically endangered landlocked salmon (Salmo salar m. sebago) families in survival and growth traits across early life stages and in different environments.

Endangered wild fish populations are commonly supported by hatchery propagation. However, hatchery-reared fish experience very different selective pressures compared to their wild counterparts, potentially causing genotype-by-environment interactions (G × E) in essential fitness traits. We experimentally studied early selection in a critically endangered landlocked Atlantic salmon population, first from fertilization to the swim-up stage in a common hatchery setting, and thereafter until the age of 5 months in two contrasting rearing environments. Swim-up progeny were moved either to standard indoor hatchery tanks involving conventional husbandry or to seminatural outdoor channels providing only natural food. After the first summer, sampled survivors were assigned to their families by genotyping. Early survival until the swim-up stage was mostly determined by maternal effects, but also involved significant variation due to sires and full-sib families (potential genetic effects). High on-growing survival in hatchery tanks (88.7%) maintained a more even distribution among families (relative share 1.5%-4.2%) than the seminatural environment (0.0%-5.4%). This heterogeneity was mostly maternal, whereas no independent paternal effect occurred. Heritability estimates were high for body size traits in both environments (0.62-0.69). Genetic correlations between the environments were significantly positive for body size traits (0.67-0.69), and high body condition in hatchery was also genetically linked to rapid growth in the seminatural environment (0.54). Additive and phenotypic growth variation increased in the seminatural environment, but scaling effects probably played a less significant role for G × E, compared to re-ranking of genotypes. Our results suggest that not only maternal effects, but also genetic effects, direct selection according to the environmental conditions experienced. Consistently high genetic variation in growth implies that, despite its low overall genetic diversity and long history in captive rearing (>50 years), this landlocked Atlantic salmon population still possesses adaptive potential for response to change from hatchery rearing back to more natural conditions.

Use of ovaprim and Chorulon hormones for spawning induction of G4 transgenic Mutiara catfish Brood stock in rearing indoor Hatchery

Use of ovaprim and Chorulon hormones for spawning induction of G4 transgenic Mutiara catfish Brood stock in rearing indoor Hatchery

The Effect of Different Time on Temperature, pH, and Disolved Oxygen in Indoor Hatchery

The hatchery is a biosecurity system in the form of a water quality control system and aquatic environmental health. Hatchery determines the success or failure of spawning. Temperature, pH and dissolved oxygen are key water quality parameters that control the distribution and distribution of organisms in the waters. Temperature, pH and dissolved oxygen in waters are key water quality parameters that control the distribution and distribution of organisms in the waters. This study aims to describe fluctuations in water quality, namely temperature, pH, and DO in the indoor hatchery based on different times. The design used was a RAL with 3 treatments and 4 repetitions, namely P1: observing water parameters every 1 hour (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 WIT); P2: observation of water parameters every 2 hours (6, 8, 10, 12, 14, 16, 18, 20, 22, 24 WIT); and P3: observation of water parameters every 4 hours (6, 10, 14.18, 22 WIB). The results showed that in general the temperature, DO and pH values ​​in the indoor hatchery did not fluctuate significantly. However, during the observation at 14 to 16 WIB at P1 there was an increase in temperature and DO, on the contrary there was a decrease in the pH value. When DO increases, the pH appears to decrease. At P2 there was a decrease in temperature values ​​at 6 to 8 WIB, while the DO and pH values ​​were stable. Furthermore, at P3, it can be seen that the temperature, DO and pH values ​​are more stable.

Adherence of kelp (Saccharina latissima) gametophytes on ropes with different binder treatments and flow regimes

The cultivation of kelp typically involves two stages, where an indoor hatchery phase preceedes the grow-out phase at-sea. The in situ adhesion of microscopic propagules onto specifically designed substrates using binders has been proposed as an alternative to conventional hatchery methods where juvenile seaweeds are cultured on seeded twine, aimed at saving resources while increasing productivity as it obviates the hatchery phase. Here we tested how well kelp (Saccharina latissima) gametophytes adhere to cultivation ropes using two binder types (agar and κ-carrageenan) and application treatment (separate or mixed application) under two ecologically relevant flow regimes (5 and 15 cm s−1), and a control condition (0 cm s−1) in a laboratory flume. Our findings indicate that the effectiveness of a binder to retain S. latissima gametophytes onto cultivation rope, measured by the sporophyte density, was comparable for all binder types in the high flow velocity (15 cm s−1) treatments, including the non-binder control treatment. Sporophyte densities were highest in the low flow velocities (0 and 5 cm s−1) in the absence of a binder compared to all other treatment combinations. In conclusion, our results highlight that the effectiveness of binder assisted seeding of kelp propagules did not differ between the binder and non-binder treatments and was unaffected by flow velocities for the binder treatments. These findings are important in the development of novel methods and further optimisation of existing binder-based methods aimed at retaining seaweed propagules onto cultivation rope.

VARIATION OF TEMPERATURE AND ZEOLITE APPLICATION ON SIMULATED TRANSPORT OF CULTURED JUVENILE SEA CUCUMBER (Holothuria scabra)

Sea cucumber (Holothuria scabra) aquaculture practice required different sites for the juvenile and grow-out phase. While broodstock conditioning, spawning, and nursery phase were mostly conducted in an indoor hatchery, the juvenile needs to be reared outdoor in saltwater pond, sea pens, or ex-situ grow-out sites. However, information on optimal transport condition with regards to post-transport survival from the hatchery to the grow-out sites is limited. These gaps of knowledge required immediate research since the demand for sustainable sea cucumber culture is constantly increasing, whether for commercial or conservation (restocking) purposes. Therefore, the aim of this study is to investigate the effectiveness of transportation methods of juvenile sandfish by combining temperature and zeolite treatment. The variation of temperature (low and ambient) combined with the use of zeolite treatment on simulated transport condition of sea cucumber juvenile were evaluated in this study. This experiment used 3 (three) replicate groups consisting of 10 (ten) individual hatchery-produced sea cucumber juvenile (less than 0.1 g weight) held in 4 (four) different treatments of temperature and zeolite addition to medium water for 12 hours duration of simulated transport. The monitoring result of water quality (pH and ammonia) and the survival rate of sea cucumber juvenile observed within 7 (seven) days post-transport suggests that pH and survival rate were affected by the temperature regime and zeolite addition. The addition of zeolite and the increase of temperature tend to decrease pH values. However, the excessive decrease of temperature should be avoided during the transportation process as it tends to reduce the survival rate of sea cucumber juvenile.

Studies on the Growth Responses of Common Carp (Cyprinus carpio) Progenies Raised Using Different Starter Diets

200 fry of carp obtained from induced breeding by stripping were fed three times daily ad libitum with Artemia (DT1), commercial starter diet (DT2), and dried egg yolk (DT3)for 8 weeks. Each treatments were in triplicates in indoor hatchery. At the end of the experiment, the progenies mean weight gained (MWG) was highest in the treatments fed Artemia (3.490±0.015a) as compared to others with significant difference (P<0.05).Mean weight gained (MWG) was highest in the treatments fed Artemia. Percentage weight gain (%WG) and specific growth rate (SGR) had no significant differences (P<0.05). Feed conversion ratio (FCR) was highest (P<0.05) in treatment fed with smashed egg yolk. Feed conversion efficiency (FCE) was highest (P<0.05) in the treatment fed with composed feed. Mortality rate was highest in treatment fed with Artemia, and percentage survival was highest (P<0.05) in treatment fed with composed feed. Percentage jumpers per treatment were highest in Artemia diet. In conclusion, it is imperative that Artemia feed (amidst other starter diets researched on) is most preferable for the optimum growth and development of common carp fry.

Effects of handling stress and moulting cycle on reproductive performance and digestive capacity of female giant freshwater prawn, Macrobrachium rosenbergii

Energy metabolism is a critical component in assessing the fundamental aspect of organism fitness in prawn aquaculture farming. This is particularly important to maintain sustainable energy use to cope with stress and tolerance without affecting growth and reproduction functions. This study aims to determine and compare energy utilisation with a special focus on reproductive performance and digestive capacity concerning the handling-stress and moulting cycle of female Giant Freshwater Prawn, Macrobrachium rosenbergii. There were two experimental groups, which are (i) grow-out pond-reared (G1): prawns were sampled randomly and concurrently for one day at an outdoor condition, and (ii) short-term maintenance (G2): prawns were transported to an indoor hatchery, acclimated for two weeks, and sampled by staggered-method for two consecutive months. For the respective experimental conditions, haemolymph from five females was sampled at eight different moulting stages, whereby each stage was classified as reproductive and non-reproductive moulting cycles. Cultivated females at the grow-out pond had higher levels of haemolymph glucose (p < 0.05) at Sub-stages D1 (0.51 ± 0.12 mg/mL), D3 (0.50 ± 0.05 mg/mL), and A (0.71 ± 0.09 mg/mL) during the reproductive moulting cycle compared to the short-term maintenance at similar moulting stages. Other findings showed that cultivated prawns at the grow-out pond had significantly (p < 0.05) higher glucose levels at Sub-stages D3 (0.57 ± 0.09 mg/mL) and B (0.37 ± 0.03 mg/mL) during the non-reproductive moulting cycle compared to the short-term maintenance indicating that energy was utilised to cope with the handling stress. We suggest that short-term maintenance may reduce the stressors factor and is applicable for hatchery operations to maintain the health of the prawn.

Comparative study on African catfish (Burchell, 1822) hypophysation using ovaprim and chicken pituitary gland extract

Comparative study on African catfish hypophysation indices using ovaprim and chicken pituitary gland extract (CPGE) was carried out. Sixteen (16) African catfish brood stocks between 1100 and 2300 g in ratio 2:1 and four (4) numbers of layer birds (Gallus gallus domesticus) between 1200 and 2200 g in ratio 1:3 were used respectively. The experiment was batched into “A” and “B”. Batch ‘A’ was placed on ovaprim while batch ‘B’ was placed on CPGE. An indoor hatchery vat, measuring 0.6096 m x 1.8288 m x 0.3048 m each was used for the incubation. Digital measuring kits were used to monitor water quality parameters and measurement of the brood stocks weights independently. Brood stocks on ovaprim and CPGE treatments had the following mean hypophysation indices in these order: fecundity (11100±7690 and 17760±13863), latency period (9.53±0.54 and 9.77±0.49), fertilization percentage (94.03±5.90% and 90.6±10.11%), hatchability percentage (75.6±0.81% and79.35±10.27%), number of eggs produced (5889±657.37 and 9403.33±589.80), total number of larvae hatched (4717.33±1111.0 and 7111.33±506.64), SGR (0.67±0.31 and 1.1±0.31), and survival rate (64.81±0.71 and66.24±2.19) respectively. There was no significant difference (p = 0.05) in the mean values of fecundity, latency period, fertilization and hatchability percentages in both treatments but there was significant difference (p ≤ 0.05) in number of eggs produced and total number of larvae hatched in both treatments. The water quality parameters were within the range for induced breeding techniques and there was no significant difference (p= 0.05) in both experiments. Both ovaprim and CPGE had excellent results from the induced breeding of Clarias gariepinus and yielded good results. Therefore, CPGE could be recommended from the view point of excellent results and its availability from chicken slaughter houses as against ovaprim which are imported.

Standardization of oocyte size during artificial fertilization and optimization of stocking density during indoor larval and outdoor nursery rearing of captive spotted scat (Scatophagus argus) for a viable juvenile production system

The present study describes the viable and efficient hatchery seed production technique to maximize spotted scat (Scatophagus argus) juvenile production in captivity during the breeding season. Broodstock fish maintained in the earthen pond of hatchery were selected according to varying mean oocyte diameter (MOD) ranging from 351 to 400 (T1), 401–450 (T2), 451–500 (T3), and > 500 μm (T4) according to natural vitellogenesis progression. Breeding pairs were formed as two males: one female. Females (n = 24) were induced with a double dose of hCG (2000 IU kg−1 body weight day−1) and a single dose of LHRHa (400 μg kg−1 body weight) each at 24 h interval, whereas males (n = 48) received a single dose of LHRHa (200 μg kg−1 body weight). Females in T4 were spawned through dry stripping earliest at 30 h post hormone induction, whereas females of the T1 group spawned last at 33 h. The largest (P < 0.005) diameter (718.33 ± 3.28 μm) of fertilized eggs was observed in T4, whereas the smallest (652.33 ± 18.68 μm) fertilized eggs were observed in T1 post-fertilization. Significantly highest absolute and relative fecundity was found in T5 (1060.67 ± 45.36 and 213,239.7 ± 17,324.9, respectively), whereas T1 and T2 exhibited no significant difference. The dry stripped eggs were fertilized with milt and incubated for 22 h for hatching. Females in T4 achieved the greatest fertilization (98.67 ± 0.88) and hatching (97 ± 2.08) percentages significantly. The initial oocyte size range of 351–400 μm in T1 led to the lowest fertilization (17 ± 3.46) and hatching (10.67 ± 3.92) percentage. Subsequently, scat juvenile production techniques were standardized by conducting two experiments on stocking densities of larvae and fry. Hatchlings were first reared in the mesocosm larval rearing system in an indoor hatchery with four different stocking density of 2 (SD2), 4 (SD4), 6 (SD6), 8 (SD8) larvae L−1 for 30 days. Stocking density of 4 and 6 larvae L−1 achieved the highest survival of 53.05 ± 1.01% and 51.03 ± 1.23%, respectively. On completion of metamorphosis (30 dph), fry were shifted to hapa based rearing in a pond with three different stocking density of 2000 (SD2000), 3000 (SD3000), 5000 (SD5000) fry m−3 for 30 days. Highest survival percentage of 78.94 ± 2.78 found in SD3000. Present study standardized the operation protocol for a commercial hatchery aiming for juvenile scat production by selecting females with initial oocyte size >500 μm diameter for artificial fertilization. Seed production can be optimized by adopting a stocking density of 4–6 larvae L−1 in the indoor larval rearing and 3000 fry m−3 in outdoor hapa based nursery systems.

Optimisation of nursery rearing for megalopa of giant mud crab Scylla serrata (Forskal, 1775)

Three nursery rearing trials were conducted to overcome the inconsistent survival of megalopa of the giant mud crab Scylla serrata (Forskal, 1775) during metamorphosis to crab instar. In the first trial, 3-4 days old megalopa (4.73 mg mean body weight) were stocked in hapas erected in outdoor brackishwater ponds and indoor fiberglass (FRP) tanks at densities of 500 nos. m-2 and 1 no. l-1 respectively and reared for 15 days using minced clam meat (Meretrix casta) as feed. Outdoor hapas were provided with seaweed, Gracilaria tenuistipitata as shelter. Mean survival rate of crab instar following three consecutive runs were significantly higher (p&lt;0.05) for megalopa reared in outdoor hapas (57.7±2.7%) over indoor FRP tanks (24.1±2.2%). To ascertain the life stage that yields optimal survival on weaning from indoor hatchery to ponds, zoea 5 (Z5) and megalopa 1-day old (M1), 2-day old (M2), 3-day old (M3) and 4-day old (M4) were reared in hapas for15 days and fed on minced clam meat. Three day and 4-day old megalopa demonstrated significantly higher survival rates (p&lt;0.05) of 62.3±3.08% and 69.6±2.35% respectively to crab instar stage at conclusion of the trial. Megalopa (3-4 days old, 5.05 mg mean body weight) were stocked to 100 l tanks (stocking density - 1 no. 4 l-1) and reared for a period of 8 days using different feeds viz., artemia biomass (T1), minced clam meat (T2), crab larvae (T3) and artemia nauplii (T4) in the third trial to evaluate various production parameters. Crab instar conversion rate (number of crab instars/number of megalopa stocked × 100) was significantly higher (p&lt;0.0001) for megalopa fed using artemia biomass (T1) and minced clam meat (T2) at 74.66±5.81% and 72.00±2.30% respectively. Results of the present study indicate that, high density rearing (500 no. m-2) of megalopa (3-4 days old) in outdoor hapas provided with seaweed refuge for short periods (15 days) would yield higher survival rate to crab stage. Nursery rearing of megalopa in ponds reduces the hatchery phase in mud crab larval rearing and maximise production of crab instars.

HEREDITY OF BAND PATTERN IN CLOWN FISH, Amphiprion percula

&lt;p&gt;One of marine ornamental fishes which was succeeded on its breeding, from eggs production to larval and juvenile rearing at Institute for Mariculture Research and Development, Gondol was Clown fish, &lt;span style="text-decoration: underline;"&gt;Amphiprion&lt;/span&gt; &lt;span style="text-decoration: underline;"&gt;percula&lt;/span&gt;. In local name, the fish also known as Biak Clown fish. In culture development, the fish frequently faced the problem on color pattern which was not meet with export demand. The fish should be bright orange and thin black stripe pattern. In this experiment, analysis was conducted to understand the juvenile color variation produced from 3 pairs broodstock. Larvae and juvenile were reared in the indoor hatchery for 2-3 months,then reared at outdoor tanks for other 3-4 months. Amplification of broodstock and juvenile genoms using specific primer for pigment sequens. Parameters observed on juvenile were classified into three color pattern classes i.e., class I (thick black stripe and disperse), class II(thick black stripe), and class III (thin black stripe). Numbers of juvenile analyzed from its pair broodstock and each class were 2-3 fishes. Color perform similarity coefficient was analyzed molecularly using sequencing. Sequencing process followed: DNA isolation, amplification using gen Tyr primer, purification PCR product and finally DNA sequencing. Sequencing analyses of PCR product, after alignment showed that similarity coefficient of color pattern of class I, II, and III between broodstock and juvenile was only 50 %, and phenotipically, color pattern appeared on juvenile were different than its broodstock. The changes of color perform on Clown fish also affected by interaction between genotype and environment and feed pigment concentration.&lt;/p&gt;&lt;p&gt;Keywords: heredity, color pattern, Tyr gene, clown fish, A. percula&lt;/p&gt;

HEREDITY OF BAND PATTERN IN CLOWN FISH, Amphiprion percula

One of marine ornamental fishes which was succeeded on its breeding, from eggs production to larval and juvenile rearing at Institute for Mariculture Research and Development, Gondol was Clown fish, Amphiprion percula. In local name, the fish also known as Biak Clown fish. In culture development, the fish frequently faced the problem on color pattern which was not meet with export demand. The fish should be bright orange and thin black stripe pattern. In this experiment, analysis was conducted to understand the juvenile color variation produced from 3 pairs broodstock. Larvae and juvenile were reared in the indoor hatchery for 2-3 months,then reared at outdoor tanks for other 3-4 months. Amplification of broodstock and juvenile genoms using specific primer for pigment sequens. Parameters observed on juvenile were classified into three color pattern classes i.e., class I (thick black stripe and disperse), class II(thick black stripe), and class III (thin black stripe). Numbers of juvenile analyzed from its pair broodstock and each class were 2-3 fishes. Color perform similarity coefficient was analyzed molecularly using sequencing. Sequencing process followed: DNA isolation, amplification using gen Tyr primer, purification PCR product and finally DNA sequencing. Sequencing analyses of PCR product, after alignment showed that similarity coefficient of color pattern of class I, II, and III between broodstock and juvenile was only 50 %, and phenotipically, color pattern appeared on juvenile were different than its broodstock. The changes of color perform on Clown fish also affected by interaction between genotype and environment and feed pigment concentration.Keywords: heredity, color pattern, Tyr gene, clown fish, A. percula

Differential expression profiling of orange‐spotted grouper larvae, Epinephelus coioides (Hamilton), that survived a betanodavirus outbreak

Nervous necrosis virus (NNV), a piscine nodavirus, has caused serious viral nervous necrosis and viral encephalopathy and retinopathy in hatchery-reared larvae and juveniles of a wide range of marine teleost species worldwide in the last two decades. Although the mortality of NNV-infected larvae is nearly 100%, there are still some larvae that survive this catastrophe. To comprehensively understand the variations of these survivors at the molecular level, we collected orange-spotted grouper larvae that survived an NNV outbreak in an indoor hatchery in southern Taiwan to study differential gene expression. Healthy larvae with high, medium and low levels of detected NNV were compared with morbid larvae using a 9600-clone-containing grouper larva cDNA microarray, and differential gene expression was further confirmed by a quantitative real-time polymerase chain reaction. Significant variation exists in healthy larvae. The following genes were upregulated: adenylate kinase 1-2, myosin binding protein H-like, myosin light chain 2, myosin light chain 3, tropomyosin, fast/white muscle troponin T embryonic isoform, and parvalbumin 1 and 2 genes. The following genes were downregulated: apolipoprotein A-I, trypsinogen, pyruvate kinase and astacin-like metalloprotease. Moreover, immunoglobulin M heavy chain gene transcription was significantly higher in healthy larvae that had high virus levels, indicating that humoral immunity might protect organisms from viral infection. These results suggest that some non-immune-related genes may have played important roles in survival during the larval metamorphosis stage, after betanodavirus infection.

Breeding and Larval Rearing of Asian Catfish, Clarias batrachus (Linnaeus, 1758) on Live and Artificial Feed

A study was conducted to observe the breeding and larval rearing of Asian Catfish, Clarias batrachus fed with live and/or artificial feed for 21 days in an indoor hatchery. The brooders of C. batrachus (Av. wt of female 160 ± 10.5 g; Av. wt of male 120 ± 6.75 g) were procured from outside ponds and stocked in a pond near the experiment site 2-months prior to spawning. The fishes were successfully induced bred using ovaprim @ 1.0–2.0 ml/kg body weight (bw) to females and 0.5–1.0 ml/kg bw to males. Fertilization, hatching and survival percentages at spawn stage were respectively recorded 70.6 - 72.8, 60.7 - 55.3 and 54.3 - 56.2. After yolk-sac absorption, fry of three age groups 7, 14 and 21 days were subjected to feed trial using Artemia nauplii followed by laboratory made feed for 21 days. Weekly sampling indicated that higher age groups constantly maintained higher lengths and weights with highest survival in the age group of 14-days old fry and SGR in 7-days old. The quality of hatchery water was recorded for temperature 29 ± 1°C, pH 7.2 ± 0.2, DO 7.1 ± 0.3 mgL-1 and total alkalinity 132 ± 4.0 mgL-1 respectively.

PERFORMANCE AND HETEROTIC ESTIMATION OF GROWTH IN INTRASPECIFIC CROSSING OF GIANT GOURAMY

Intraspecific crossing of giant gouramy was done to get better hybrid population. This study was conducted to evaluate the hybrid vigour or heterotic value of the hybrids line, especially for growth rate character. Besides that, we want to know the effect of hybridization on performance of phenotypic variability. Two days post hatching age larvae of four populations i.e. Bastar and Blue-saphire strain, F-1 hybrid and F-1 hybrid reciprocal, were used in this experiment. All fish were reared in aquaria for 30 days period in indoor hatchery. The fish were fed with live food such as Moina and Daphnia for the first ten days, followed by Tubifex for the second ten days and finally, commercial feed were given until the end of the study. The collected data were total length, standard length, and body weight of each population. The results showed that the phenotypic variability of the hybrid population was higher than that of inbred population. Hybrid population from female of Bastar and male of Blue-saphire has better growth than both of its parents. Heterotic values of total length, standard length, and body weight of the hybrid population was 9.5%, 2.9%, and 15.6% respectively. Maternal effect was detected in hybrid population.

Effect Of Grow-Apart Syndrome On The Head Diameter, Body Length And Cannibalism In Clarias Gariepinus (Burchell, 1822) Hatchlings

Nine indoor rectangular (0.53 m3) concrete tanks were each stocked with induced-bred Clarias gariepinus fry (mean ± standard error of mean (s.e.m.) =1.63±0.61g) at 500 fry per tank. Ad libitum feeding, restricted feeding and no-feeding treatments each of mixed zooplankton and hatched brine shrimp (Artemia salina) replicated three times was used. One hundred and fifty fry each weighing 2.22 ± 1.22 g (mean ± s.e.m) from the indoor rearing exercise were stocked in each of nine 150 m3-capacity outdoor earthen ponds. These were similarly replicated and treated as in the indoor tanks but 40% crude protein crumbled artificial feed was used. The increase in body length, head diameter and the frequency of cannibalism in the fry were monitored indoor and outdoor for 14 days. The results showed that fish reared in the outdoor earthen ponds had better increases in standard lengths (SL) and total lengths (TL) than those reared in indoor tanks. There were significant differences (P < 0.05) in mean increases in the TL and SL per day for the jumpers (JP) whether reared indoor or outdoor. On the contrary, no significant differences (P > 0.05) in increases in SL and TL per day were recorded for the non-jumpers (NJP) whether reared indoor or outdoor. Fish fed ad libitum showed better increases in length and head diameter for both the jumpers and the non-jumpers than those on other feeding regimes. Unlike in outdoor rearing, increase in the head diameter of the JP and the NJP raised on different feed regimes was significantly different (P < 0.05) for indoor hatchery. The 36.75% mortality obtained in indoor hatchery was due mainly to cannibalism. Little or no feeding of C. gariepinus fry therefore enhanced grow-apart syndrome which encouraged cannibalism, differences in body length and head diameter. Keywords: jumpers, non-jumpers, restricted feeding, ad libitum, mortality, cannibalism. IFE Journal of Science Vol. 9 (1) 2007 pp. 33-44

Intensification of redclaw crayfish Cherax quadricarinatus culture : I. Hatchery and nursery system

Intensification of an indoor hatchery and nursery system for the Australian redclaw crayfish Cherax quadricarinatus (von Martens) (Decapoda: Parastacidae) was obtained by increasing the surface area available for the crayfish juveniles and by synchronizing the age of the hatchlings held in each tank. The former improvement was facilitated by distributing an artificial seaweed-like material throughout almost the entire volume of small (275 l) hatching tanks. As the number of egg-bearing females was increased from 3 to 8 per hatching tank, the number of juveniles per liter also increased to as many as 6.5 juveniles/l, without reaching an apparent upper limit. The hatchlings were kept in the tanks for 75 days from the day females were found to be gravid and then harvested and graded according to size. The average juvenile weight at harvest was 0.34±0.04 g. The weight distribution of the juvenile males was not significantly different from that of the juvenile females on the day of harvest, and in both the distribution was positively skewed.

Crowding female red claw crayfish, Cherax quadricarinatus, under small-tanks hatchery conditions: what is the limit?

Previous studies on reproduction in the red claw crayfish, Cherax quadricarinatus, have successfully employed broodstock densities of up to 20 crayfish m −2. This study attempted to increase the density of broodstock in order to intensify production of young in indoor hatcheries. Adult crayfish were stocked in 0.3 m 2 tanks at a 1:5 M:F sex ratio at three densities: 6, 12 and 18 crayfish per tank (corresponding to 20, 40 and 60 m −2). The number of berried females was noted at weekly intervals during 14 weeks. There was no difference among densities in survival rate and percentage of spawning and molting, nor in clutch size (pleopodal egg counts) of females. The results indicated that breeding red claw females are insensitive to crowding over a wide range of densities. They suggest that a broodstock density higher than 60 crayfish m −2 is feasible under indoor hatchery conditions.

A comparison of clutch and brood size in the Red Claw, Cherax quadricarinatus (von Martens) and the Yabby, C. destructor Clark (Decapoda: Parastacidae)

Data are presented on clutch and brood size in the freshwater crayfishes, Cherax quadricarinatus (red claw) and C. destructor (yabby) obtained under indoor hatchery conditions. Clutch size, measured as pleopodally attached eggs, and brood size, measured as newly independent juveniles, were positively related to crayfish weight. Regression coefficients were not significantly different from 1.0, consistent with theoretical expectations for clutch/brood size–weight relationships. ANCOVA indicated significance differences between species and between clutch and brood sizes. Based on size adjusted means, C. destructor was found to produce 1.5 times more offspring than C. quadricarinatus and average brood size was found to be 40.0% lower than average clutch size. Causes of egg and larvae loss, and reasons for the high degree of variability in clutch/brood size estimates amongst studies of these crayfish are discussed.

Intraspecific variation in clutch and brood size and rate of development in the yabby, Cheraxdestructor (Decapoda: Parastacidae)

The cultured freshwater crayfish Cherax destructor Clark has the largest distribution of any freshwater crayfish species in Australia. This study presents preliminary data on intraspecific variation in reproductive traits of C. destructor obtained from three populations under indoor hatchery conditions. Clutch size, measured as pleopodally attached eggs, and brood size, measured as newly independent juveniles, were positively correlated with crayfish weight. ANCOVA indicated significant differences between populations and between clutch and brood size. Based on size adjusted means, clutch size ranged from 360.6 to 593.4 and brood size from 311.4 to 384.5. Average brood size was 22.6% lower than average clutch size. Development time also differed amongst populations and was negatively correlated with temperature. Temperature adjusted mean development time ranged from an a minimum of 33.4 days to a maximum of 42.2 days. A strong inverse relationship between clutch/brood size and development time further highlighted the extent of life history differences amongst the crayfish populations. The implications of the increasing evidence for significant intraspecific variability within commercial species of Cherax in relation to aquaculture research and sustainable aquaculture are discussed.