Spermatophore cryopreservation and artificial insemination of black tiger shrimp, Penaeus monodon (Fabricius)

To develop an appropriate cryopreservation protocol for spermatophores of black tiger shrimp, Penaeus monodon, three cryoprotectants (dimethyl sulphoxide (DMSO), methanol (MeOH) and ethylene glycol (EG)) at two concentrations (5% and 10%) were examined. Artificial implantation of spermatophores was also carried out to assess the fertilizing ability of fresh and post‐thaw spermatophores. Spermatophores were collected during consecutive regenerations (15‐day intervals) and assessed for qualitative and quantitative changes and also for fertilizing ability by implantation. The mean fertilization rate for artificial insemination using post‐thaw spermatophore was 79.9±3.7%, lower than the fertilization rates observed for artificial implantation using fresh spermatophore and natural mating. Mean hatch rates for fresh spermatophore, frozen‐thawed spermatophore and natural mating were 88.8±0.6%, 87.8±0.4% and 88.3±0.5%, respectively; and there was no difference among the three groups. The mean fertilization rate of spermatophores collected during the first stripping was higher (90.6±0.6) than during the second stripping (85.7±2.6), but the mean hatch rate was not different between the two strippings. The highest mean sperm viability (79.7±0.4%) was obtained from DMSO (5%), with no survival observed in the 10% MeOH treatment. Spermatophore weight, total sperm count and percentage of abnormal sperm were not different between spermatophores collected at the first and second stripping. This is the first study to report high fertilization and hatch rates from cryopreserved spermatophore using artificial implantation of spermatophore before spawning.     

Comparison of larval performance between Thai and Vietnamese freshwater giant prawn, Macrobrachium rosenbergii (de Man): a preliminary study

This study compared the performance of larvae of giant freshwater prawn (Macrobrachium rosenbergii) from Thailand and Vietnam. Thai broods were collected from a farm and Vietnamese broods were collected from a river. Larvae from these two sources were raised in identical environments, and their rates of development and survival as well as their ability to withstand environmental stresses were assessed. The first postlarval stage was observed in both strains on day 22. All larvae (100%) from Thai broods completed metamorphosis by day 36, but only 89% of the Vietnam strain completed metamorphosis by day 45. The stages of development were more uniform in larvae from the Thai stock than the Vietnamese stock. Survival differences were observed within the first week (92% in the Thai group vs. 55% in the Vietnamese group). These differences were most pronounced beginning in week 5 (52% and 16% respectively) and week 7 (33% and 2% respectively). No clear difference was found in brood size and fecundity between the two groups. No difference in survival was observed between the two groups of larvae challenged with salinity, oxygen or formalin. Differential development rates of larvae in the same batch would naturally create conditions favourable for cannibalism and impaired ability to capture food. The earlier and more uniform rate of development, and subsequent higher rate of survival of Thai stock compared with the Vietnamese wild stock is suggested to be due to inadvertent selection in the domesticated stock.     

Effect of cryoprotectants, extenders and freezing rates on the fertilization rate of frozen striped catfish, Pangasius hypophthalmus (Sauvage), sperm

The effects of four cryoprotectants (methanol, MeOH; dimethyl sulphoxide, DMSO; dimethyl acetamide, DMA; and ethylene glycol, EG), three extenders (calcium‐free Hanks' balanced salt solution, C‐F HBSS, Hanks' balanced salt solution, HBSS and sodium chloride, NaCl) and two different freezing procedures (one‐ and two‐step) on the cryopreservation of striped catfish (Pangasius hypophthalmus (Sauvage)) sperm were investigated. Sperm were frozen using a controlled‐rate freezer in 250 μL straws and stored for 2 weeks in a liquid nitrogen (LN₂) container. They were then airthawed at room temperature, and fertilization, motility and viability were assessed. The highest fertilization rate of 41% (81% of control) was achieved with the combination of 12% DMSO and 0.9% NaCl using a one‐step freezing procedure (10°C min^?1). Also, DMA resulted in a higher fertilization rate (30% or 51% of the control) than MeOH (18% or 38% of the control) or EG (8% or 12% of the control). In addition, the three extenders used did not affect fertilization rates after cryopreservation with each cryoprotectant. There were no significant differences among the three cryoprotectant concentrations and between the one‐ and two‐step freezing procedures. However, fertilization rates of cryopreserved sperm were significantly lower than the controls (P<0.05). The results of this study indicate that high fertilization rates of striped catfish eggs can be achieved using cryopreserved sperm when frozen at 10°C min^?1 in DMSO or DMA with either 0.9% NaCl or C‐F HBSS.     

Improved survival of rohu, Labeo rohita (Hamilton-Buchanan) and silver carp, Hypophthalmichthys molitrix (Valenciennes) fingerlings using low-dose quinaldine and benzocaine during transport

The effects of fingerlings immersion in low‐dose benzocaine (15 and 30 mg L⁻¹, silver carp and rohu) and quinaldine (100 μL L⁻¹ silver crap and 250 μL L⁻¹ rohu) for 1, 3 and 6 h on stress responses and survival of rohu, Labeo rohita and silver carp, Hypophthalmichthys molitrix fingerlings were evaluated in a transport simulation experiment. Both quinaldine and benzocaine showed low mortalities (0–2%). The total mortality in control (with no anaesthesia) was 30% for rohu and 14% for silver carp. Quinaldine and benzocaine‐treated fingerlings had significantly higher plasma chloride levels than the control in both species. Benzocaine, quinaldine, as well as the control, had an initial elevation of plasma cortisol levels. Benzocaine lost its effectiveness after 3 h exposure while quinaldine persisted throughout the 6 h experimental period. Both sedatives reduced bacterial build‐up compared with the control. No post‐exposure mortality was observed for any of the transport methods assessed 48 h after the treatment. This study suggests that the use of low‐dose benzocaine or quinaldine during transport has positive effect on the survival and health of rohu and silver carp fingerlings.     

Ultrasound Enhanced Immersion Protocols for Masculinization of Nile Tilapia, Oreochromis niloticus

Androgen immersion protocols have been unsuccessful in consistently producing all-male tilapia at a high enough ratio for them to be commercially viable. This study explored the use of ultrasound to improve on the results of previous immersion studies. Variables tested include two hormones (trenbolone acetate-TBA and 17α-methyldihydrotestoterone-MDHT) at two concentrations (100 and 250 μg/L) and with or without ultrasound (cavitation level). All hormone treatments with ultrasound and non-ultrasound resulted in significantly higher masculinization than the appropriate controls ( P < 0.05). Among pairs of treatments of the same hormone at the same dose, all ultrasound treatments resulted in significantly higher number of males compared with non-ultrasound treatments with the exception of MDHT 250 μg/L ( P 0.05). Comparing across all ultrasound treatments, TBA 250 μg/L with ultrasound had higher masculinization than all the other ultrasound treatments ( P 0.05). Comparing across all non-ultrasound treatments, TBA 250 μg/L had higher ( P 0.05) masculinization than MDHT 100 μg/L and TBA 100 μg/L with non-ultrasound. Two of the three replicates of TBA 250 μg/L ultrasound treatment resulted in 100% males and the highest mean percentage (98%) of males. This study thus demonstrated the potential of a short-term immersion protocol using ultrasound to more predictably produce all-male, commercially viable tilapia seed.     

Correlation between Tennant method and Standardized Precipitation Index for predicting environmental flow condition using rainfall in Godavari Basin

Paddy and Water Environment - Environmental flow is necessary to maintain a healthy ecosystem and sustain aquatic lives. Its assessment is thus aimed at analysing the minimum flow of water required...     

Characterization of Small-size Egg-bearing Thai ss-strain Rotifers Brachionus rotundiformis and Their First Offspring

This study selected small (100–120 μm) egg-bearing females from a local Thai ss population and characterized their first offspring's life history in an attempt to produce small-size rotifers. Mean lorica length of selected small adult females was 120 ± 6 μm at the time of collection, and this mean length did not increase over their lifetime. While their first offspring life span was only 5.11 ± 0.35 d, the reference population longevity was higher, 9.65 ± 0.4 d. The length of reproductive period of offspring from the small-size egg-bearing female was 2.58 ± 0.38 d, shorter than that of reference population 6.83 ± 0.58 d. Although the rate of egg production was not different between small egg-bearing female and reference population, the total number of eggs produced by the small egg-bearing female's first offspring was lower (4.78 ± 0.60) compared to the reference population (11.83 ± 1.26). The small egg-bearing female's first offspring had a higher egg to lorica length ratio (76.1 ± 1.64%) than the reference population (56.6 ± 1.3%), indicating a relatively high investment in reproduction. The small egg-bearing female's first offspring reached only 125 ± 6 μm in 36 h, and further culture of their offspring over 35 d resulted in a mean offspring size, 163 ± 11 μm, similar to the reference population (159 ± 16 μm). This shows that population mean size reduction is not likely to result from selecting small egg-bearing females within a single generation. The unique reproductive characteristics of small egg-bearing female place it in its own category.     

Characterization and comparison of variations in reproductive performance of Chitralada strain Nile tilapia, Oreochromis niloticus (L.)

In an attempt to better understand and characterize the variability in the female reproduction of individual Thai‐Chitralada strains of Nile tilapia, Oreochromis niloticus (L.), tagged mature females (n=68) from a single population were monitored in a hapa‐in‐pond system over a 12‐month experimental period. Spawn female⁻¹, eggs female⁻¹ day⁻¹, eggs kg female⁻¹ day⁻¹, day spawn⁻¹ and weight (g) at first spawning of individual females were determined from the regular weekly sampling of weight (g) and eggs per spawn. For analysis, the females were grouped into two, high spawning (HSF) and low spawning frequency (LSF) classes based on their spawning frequency (SF) record. Moreover, nested under these two classes were two groups each based on growth rate, i.e., high frequency – large size (HL), high frequency – small size (HS), low frequency – large size (LL) and low frequency – small size (LS). There was no difference in eggs spawn⁻¹ among all females. The HSF group produced 68% and 361% more eggs female⁻¹ day⁻¹ than the population mean and LSF group respectively. Eggs female⁻¹ day⁻¹ and spawn female⁻¹ remained high in the HSF group and low in the LSF group throughout the 12‐month experimental period. This suggests that individual female spawning activity is consistent within a population in a common environment. The inter‐spawn interval increased with age in all four groups, and day spawn⁻¹ was shorter by 130% in HSF females compared with day spawn⁻¹ in LSF. The HSF group also spawned more successively (≥3), while the LSF group of females had fewer successive spawns (≤2). Body weight (g) had no influence on the number of eggs produced. The study indicates that separating frequently spawning females could be used as an important strategy to improve commercial seed production of Nile tilapia.     

Controlled reproduction of an important indigenous fish species, Spinibarbus denticulatus (Oshima, 1926), in Southeast Asia

Aquaculture of Spinibarbus denticulatus (Oshima, 1926), a fish species indigenous to North Vietnam and Eastern China, is constrained by lack of fingerlings for stocking ponds and cages. As these fish do not naturally breed in captivity, carp pituitary extract (CPE), luteinizing hormone-releasing hormone analogue (LHRHa) with domperidone (DOM) and human chorionic gonadotropin (HCG) were administered at various doses to induce ovulation. A first set of experiments evaluated the response to LHRHa (30, 40 and 50 μg kg⁻¹) with or without DOM (10 mg kg⁻¹), CPE (20, 30 and 40 mg kg⁻¹) and HCG (3000, 4000 and 5000 IU kg⁻¹). A second set of experiments evaluated the dose response to LHRHa (30, 35, 40 and 50 μg kg⁻¹) primed with 6 mg kg⁻¹ of CPE, and HCG (3000, 3500, 4000, 5000 IU kg⁻¹) primed with 6 mg kg⁻¹ of CPE. The treatment groups were compared with each other and the control (injected with 0.9% saline solution). Only 25% and 50% ovulation resulted when treated with LHRHa at 40 and 50 μg kg⁻¹, whereas 100% ovulation was achieved with an addition of DOM to LHRHa. Both 30 and 40 mg kg⁻¹ CPE induced 100% ovulation. However, HCG (4000 and 5000 IU kg⁻¹) induced ovulation in only 33% of females. When primed with CPE, the minimum dose of LHRHa required was 35 μg kg⁻¹ to achieve 70% ovulation. Priming HCG with CPE also resulted in 100% ovulation, and the minimum effective dose of HCG to induce ovulation was 3500 IU kg⁻¹ with 60% ovulation. Fertilization and hatch rates observed in this study with different hormonal stimulation were high (80–93%). The results indicate that while the use of combined hormone strategy has no apparent advantage over a single hormone strategy, LHRHa+DOM (40 μg kg⁻¹+10.0 mg kg⁻¹) and CPE (30 mg kg⁻¹) are most effective in consistently inducing ovulation and thus can be used for commercial hatchery production of S. denticulatus larvae.