Efficacy of exogenous hormone (GnRHa) for induced breeding of climbing perch Anabas testudineus (Bloch, 1792) and influence of operational sex ratio on spawning success

Can sympathetic induction be a convenient technique for breeding Amblypharyngodon mola (Hamilton, 1822)?

Mola carplet (Amblypharyngodon mola) is one of the most popular small fish species of the Indian subcontinent. There are limited studies on captive breeding of this species, which is important for aquaculture and the conservation prospects of this species. The conventional induced breeding method using an inducing agent (GnRHa and dopamine antagonist) is one of the most effective and prevalent methods of breeding fish. It is a laborious and time-consuming process, particularly in mass fish breeding and in lieu of that, a less time-consuming method - sympathetic induction of the broodstock, is used in some regions of India, particularly in big carp fish. However, this method has not been reported in commercial-scale breeding of small indigenous fish species. Therefore, an experiment was conducted to compare the spawning efficiency of Amblypharyngodon mola bred by sympathetic induction with the conventional complete induced breeding method. The spawning performance in terms of latency period, relative fecundity, fertilization rate, incubation period, and hatching rates of sympathetically induced Amblypharyngodon mola were compared to completely induced Amblypharyngodon mola brooders. Although the latency period (7.8 hrs), relative fecundity (39 nos./g), fertilization rates (81.61%) and spawning efficiency coefficient (0.681) were better in conventionally induced fish, but lower post-spawning mortality (1.29%) and better hatching rates (86.21%) were observed in sympathetically induced fish. The results indicate that quality offspring of Amblypharyngodon mola could be obtained in terms of survivability through sympathetic breeding. Sympathetic induction breeding could be a cost-effective, convenient, time-saving method of mass-scale breeding and aquaculture of Amblypharyngodon mola.

Intraspecific phenotypic differences in climbing perch Anabas testudineus (Bloch, 1792) populations may be linked to habitat adaptations

The climbing perch, Anabas testudineus, is a nutritionally and economically significant food fish. The present study reveals the first comprehensive description of the life-history traits of A. testudineus scooped up through different traditional fishing gears from July 2020 to December 2020. Among the 120 collected specimens, the smallest and largest specimens were 8.5 cm-14.6 cm TL in Nilphamari and Patuakhali, respectively. The estimated b values for LLRs indicated positive allometric growth in all sampling points (b > 1.0). The LWRs of A. testudineus indicated positive allometric growth in the Gazipur and Nilphamari districts (b > 3.00) and negative allometric growth in the Patuakhali and Khulna districts (b < 3.00). A Wilcoxon sign-ranked test for WR showed no significant dissimilarity from 100, signifying the balanced habitat for A. testudineus. The estimated a3.0 was minimum in Khulna (0.0110) and maximum in Nilphamari (0.0825). "The Lm was estimated at 7.4032 (7.4) cm TL in Nilphamari and 8.86 (8.9) cm TL in Patuakhali". Nineteen of twenty morphometric measurements and ten of twelve meristic characters showed substantial variations (p < 0.0001). The principal component analysis indicated shape variation and explained 85.361% of the total variance and showed differences in TL, SL, HL, LBD, LE1, D1D2, A1A2, and VV2. The cluster heatmap demonstrates that the other stocks segregated Gazipur stock. Our findings reveal a significant dataset about intraspecific phenotypic differentiation, which will aid the long-term exploration and management of A. testudineus species in Bangladesh and its neighboring countries.

Dietary brewer’s spent yeast enhances growth, hematological parameters, and innate immune responses at reducing fishmeal concentration in the diet of climbing perch, Anabas testudineus fingerlings

A 60-day feeding trial was conducted to optimally reduce the fishmeal level in climbing perch (Anabas testudineus) fingerling diet using a dietary brewer’s spent yeast biomass (BSY) based diet. In this study, five isonitrogenous (35% CP) and isocaloric (19.15 MJ/Kg) feeds were prepared by replacing 0 (BSY0), 25% (BSY25), 50% (BSY50), 75% (BSY75) and 100% (BSY100) of fishmeal protein using BSY protein. A total of 225 numbers of uniform-sized climbing perch fingerlings (3.29 ± 0.09 g) were randomly stocked in the 15 rectangular FRP (Fiber-reinforced plastic) tanks (150 L capacity). The experimental fish were fed twice daily at 4% BW for the first fortnight and later reduced to 3% BW based on satiation. At the end of the feeding trial, the weight gain (WG) of fish increased with the increasing BSY incorporation rates corresponding to fishmeal content and peaked at 77.88%, and beyond that, WG decreased. Food conversion ratios decreased as dietary BSY levels increased and peaked at 76.28%. All other growth and feed utilization parameters followed a similar trend of weight gain. Hepatosomatic index (HSI) and viscerosomatic index (VSI), A:G ratio, serum catalase activity, and monocytes were unaffected and the total serum protein, albumin, globulin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), respiratory burst activity, lysozyme levels, myeloperoxidase activity, hemoglobulin, red blood cells, white blood cells, neutrophils, eosinophils, lymphocytes, and gut protease activities were increased significantly (P < 0.05) with the increasing replacement levels and peaked between 25 and 75%. The serum SOD activity and total platelets were decreased, whereas the serum uric acid and gut amylase activities were increased significantly to the increasing levels of FM replacement in the diets (P < 0.05). Among treatments, the BSY100 resulted in an overall poor growth response combined with relatively reduced values in nearly all biochemical parameters. The whole-body composition was nearly unaffected. The integrated biomarker response of various biochemical indicators from the different treatments has shown that the 50% fishmeal protein can be optimally replaced by BSY, which would cause an 18% reduction in the Economic conversion ratio (ECR) and −270.28 gCO₂e^– reduction in carbon footprint value per kg of climbing perch fingerlings production.

Reproductive aspects of Anabas testudineus collected from the Gajner Beel wetland in Bangladesh: implications for its conservation under changing eco-climatic conditions and suggestions for best aquaculture practice

The freshwater climbing perch, Anabas testudineus, is an economically and nutritionally valuable food fish. This study explores the various reproductive contents (size at sexual maturity, reproductive period and fecundity) of A. testudineus in the Gajner Beel concerning the eco-climatic variabilities and suggests sustainable management policies. A total of 709 individuals were randomly collected from January to December 2019 among 371 females that were sorted out for this study. Total length (TL) ranged from 7.50 to 16.40 cm. Based on the maximum length (L_max), TL vs. gonadosomatic index (GSI), TL-standard length (SL) regression and logistic model, the size at sexual maturity (L_m) was 10.00 cm, 10.40 cm, 11.00 cm and 11.50 cm, respectively. The spawning season was May to August and peaked in June-July. The Fulton's condition (K_F) was suggested as the best condition factor (p < 0.0001), and relative weight (W_R) showed no significant difference from 100 for females (p = 0.143). Fecundity was ranged from 9459 to 35,915. A significant relationship was observed between GSI and temperature (p = 0.0016), dissolved oxygen (DO) (p < 0.0001), pH (p < 0.0001), alkalinity (p < 0.001) and climatic parameters (air temperature, p < 0.001 and rainfall, p < 0.001). The data series of 48 years (1971-2019) revealed that the rise of average air temperature by 0.029 °C and the reduction of rainfall by 2.96 mm per year might shift the spawning season of A. testudineus 15-20 later. Therefore, this study will be helpful for the sustainable management and conservation of the wild stocks of A. testudineus in the Gajner Beel and adjoining ecosystems.

Hormonal induction of ovulation using Ovaprim™ [(D-Arg6, Pro9NEt)-sGnRH+domperidone] and its impact on embryonic development of wild-caught Longspine scraper, Capoeta trutta (Heckel, 1843)

Knowledge of gamete quality is a prerequisite for developing techniques to fertilize eggs and rear offspring for hatchery production. Our objective was to develop assisted reproductive techniques, via hormonal induction of final oocyte maturation (FOM), for Longspine scraper, Capoeta trutta. Fish were administered injections of salmon gonadotropin-releasing hormone analogue containing anti-dopaminergic drug (Ovaprim™) or saline (control). Effects of Ovaprim on induction of ovulation, gamete quality, embryonic development, and larval survival were later examined with serum steroid hormone levels and ovarian histology. The saline group failed to spawn, whereas Ovaprim accelerated FOM and induced spawning. Fish treated with Ovaprim showed an increase in gonadosomatic index, egg diameter, and wet weight relative to controls. Average absolute fecundity, relative fecundity, fertilization, and hatching rates were 8823 eggs/spawn, 53 eggs/g body weight, 95%, and 91%, respectively. Serum 17α,20β-dihydroxy-4-pregnen-3-one (DHP) levels were significantly enhanced by ∼4-fold in Ovaprim-treated fish compared to the saline-injected fish, while 17β-estradiol levels declined upon FOM in hormone treated fish. Embryonic development closely resembled the teleost scheme, despite variations in timing. Larval survival at 6 and 12days post-hatch were 98% and 95%, respectively. Results suggest that Ovaprim is efficient for inducing spawning in C. trutta for stock enhancement or hatchery purposes.