In most livebearing fish, the gravid spot is an excellent marker to identify brooding females, however its use to predict progress of embryonic development, brood size, timing of parturition and overall reproductive potential of populations remain unexplored. Therefore, to understand these relationships, this study quantified visual attributes (intensity and size) of the gravid spot in relation to key internal development in Gambusia holbrooki. Observations show that the colour of the gravid spot arises from progressive melanisation on the surface of the ovarian sac at its hind margin, rather than melanisation of the developing embryos or the skin of the brooding mother. More importantly, the gravid spot intensity and size were closely linked with both developmental stages and clutch size, suggesting their reliable use as external surrogates of key internal developmental in the species. Using predictive consistency of the gravid spot, we also determined the effect of rearing temperature (23 °C and 25 °C) on gestation period and parturition behaviour. The results show that gestation period was significantly reduced (F = 364.58; df = 1,48; P ˃ 0.05) at 25 °C. However there was no significant difference in average number of fry parturated in the two temperature groups (P<0.05), reaffirming that gravid spot intensity is a reliable predictor of reproductive output. The parturition in the species occurred predominantly in the morning and in contrast to earlier reports, tails of the fry emerged first with a few exceptions of head-first, twin and premature births. This study demonstrates utility of the gravid spot for downstream reproductive investigations in a live-bearing fish both in the field and laboratory. The reproducibility of the relationships (intensity with both developmental stage and clutch size), imply that they are also relevant to wild populations that experience varying temperature climes and stressors, significant deviations of which may serve as indicators of environmental health and climate variability.
Hormonal sex reversal can produce monosex fish stocks and provide insights into their gamity and reproductive physiology. However, paradoxical effects have been reported in several fish species that remain largely ignored as anomalies, particularly those of masculinisation. As a first step, this study examined reproductive viability of paradoxically masculinised Gambusia holbrooki produced following oral administration (20-100 mg/kg feed) of a feminizing hormone diethylstilbestrol (DES). Contrary to expectation, all treatment groups produced 100% male populations. Survival, mating behaviour, gamete production, breeding output as well as expression of anti-Mullerian hormone (amh), ovarian (cyp19a1a) and brain (cyp19a1b) aromatase of masculinised fish were also examined. Survival (≤ 54.1 ± 7.3%) at termination of DES treatment was significantly lower compared with controls (88.6 ± 4.3%) but remained unaffected post treatment. Gonopodium thrusting frequency (33 ± 9.8 per 10 min) was not significantly different to untreated males just as sperm abundance (3.9 ± 1.5 × 108/male) and their motility (88.6 ± 29.1%). Importantly, paradoxically masculinised fish mated with virgin females and produced clutch sizes (22 ± 4) and progeny survival (87.0 ± %) that were comparable to that of untreated males. Masculinised testes showed high amh and low cyp19a1a expression, a pattern resembling those of untreated males. Production of paradoxically sex-reversed males with a capability to produce viable offspring has not been reported previously in this or other fish species. The outcomes support a feed-back regulation of oestrogenic pathways in this viviparous fish and could be useful for ecological applications such as controlling invasive fish populations.
Optimal feeding frequency in aquaculture is vital for the sustainable and economical production of healthy, high-quality fish. This article described the growth performance and survival rate data in the juvenile phase of two commercially important ornamental fish species; Betta splendens (Siamese fighting fish) and Poecilia reticulata (Guppy) reared at different feeding frequency. Thirty days old juveniles of both species were randomly distributed into 12 3 L rectangular plastic tank (n = 10 fish/tank; three replicates per feeding frequency) where they were subjected to four different feeding frequency treatments (1 meal/day (T1), 2 meal/day (Control), 3 meal/day (T2) and four meal/day (T3)) using commercial ornamental fish micropellets for 60 days. The juvenile's weight and length were measured once a week while the number of live fish were recorded daily. The amount of feed intake was also recorded by weighing in the weight of micropellet left after feeding. At the end of the experimental period, the specific growth rate (SGR), food conversion ratio (FCR) and condition factor (K) were calculated for growth performance using the weight, length and feed intake data while the survival rate was calculated using the number of live fish data. Normality test, One-way ANOVA analysis followed by Tukey pos-hoc test were then performed on the data obtained from the calculation of SGR, FCR, K an survival rate. The data presented in this article will aid the rearing process of both species' juveniles for commercial, experimental and personal usage purpose.
This data article describes the growth performance, glucose concentration in blood and testosterone level in plasma of juvenile Asian seabass (Lates calcarifer) after being fed with exogenous melatonin at different concentrations (0, 50 and 100 mg kg-1). To collect the data, 160 juveniles (60 days old) with an initial mean weight of 20.54 ± 7.16 g and mean length 11.14 ± 0.05 cm were reared in 1800 L rectangular fibreglass aerated tanks of a recirculating aquaculture system (n = 40 fish/ tank/ treatment) for 90 days. Four different treatments were tested: basal diet without any hormone (Control), basal diet with ethanol solution (Control + Ethanol; vehicle control), basal diet sprayed with 50 mg/kg feed of melatonin (Melatonin (50 mg/kg of diets)) and basal diet sprayed with 100 mg/kg feed of melatonin (Melatonin 100 mg/kg of diets). Initial and final body weight and body length of fish was measured and recorded to calculate the data of weight gain (WG). At the end of the feeding trial, the juveniles blood glucose and testosterone level were analyzed. Normality test, One-way ANOVA analysis followed by Tukey post-hoc test were then performed on the data obtained from the calculation of WG, survival rate, blood glucose and testosterone level. The data presented in this article will helps farmers and scientist to optimize the usage of melatonin administration in Asian seabass juveniles.
Despite having high economical value and declining wild population, the aquaculture of the Malaysian mahseer (Tor tambroides) is still way behind. Crucial information such as on its sexual dimorphism is scarce thus making its broodstock management in captivity challenging. The first step in studying fish sexual dimorphism is by observing and identifying the morphological differences between each sex. Thus, this article collected and described morphometric measurements data of broodstock reared in captive conditions. The broodstock were reared and raised in captivity for five years since they were bought from a local commercial supplier while they were five-inch fingerlings. Seven conventional and 21 Truss network morphometric measurements were taken from 27 male (TL: 53.88 ± 2.86 cm; W: 1.82 ± 0.23 kg) and 27 female (TL: 53.97 ± 3.62 cm; W: 1.86 ± 0.35 kg) T. tambroides broodstocks using digital image analysis. Photograph of the fish broodstocks were captured and the morphometric measurements were conducted using imageJ freeware. Statistical analysis was later conducted on the morphometric data to identify the morphological differences between the broodstocks. This dataset will not only aid the sex identification of this species but also in stock population studies thus accelerating the development of T. tambroides aquaculture while improving its conservation efforts.
The growth performance and survival rates of juvenile striped catfish, Pangasianodon hypophthalmus, reared at various levels of pH and temperature were described in this article. Two rearing trials were conducted separately for pH and temperature where both trials lasted for 35 days. One hundred and twenty juveniles (1.5 ± 0.23 g) were randomly stocked into 12 rectangle glass aquariums (n = 10 fish/tank; three replicates per treatment) with 100 L of water for each trial. The treatment consisted of four different pH level (7.5, 8.0, 8.5 and 9.0) and four different temperature level (26 °C, 28 °C, 30 °C and 32 °C). The survival of fish was counted at the end of experiments, and the weight of the juvenile was measured once a week. The quantification of feed intake was determined through the measurement of the residual weight of the feeds after the feeding process. Upon the conclusion of the experiment, the data pertaining to weight and feed intake were utilized to calculate the specific growth rate (SGR) and food conversion ratio (FCR) as indicators of growth performance. Additionally, the number of live fish was employed to ascertain the survival rate. The data obtained from the calculation of SGR, FCR and survival rate were next subjected to a normality test, one-way analysis of variance (ANOVA), and a Tukey post-hoc test. The information in this article will help in the business, experimental, and personal usage for P. hypophthalmus juveniles rearing process.