Growth, sex reversal pattern, and reproductive characteristics of Barramundi (Lates calcarifer) broodstock candidates reared in floating cages

Sex reversal of male to female is a characteristic of barramundi (Lates calcarifer), which is affected by several factors, thereby changing the broodstock population. A study was conducted in floating cages in Langkawi, Malaysia, to determine the weight point at the onset of the sex reversal phenomena. A total of 75 female and 55 male adult individuals (3-4 weeks of age) were sampled from the fish cultured in cages to ascertain their sex at different weights. The water temperature and salinity values were 29.82 °C and 33.12 ppt, respectively. The specimens were classified into twelve bodyweight classes (2.00-8.00 ± 0.5 kg intervals). Female specimen body weight distribution was highest in the 6.01-6.50 kg class (22.6%), followed by the 5.51-6.00 kg and 4.51-5.00 class (13.3%), while male specimen body weight distribution was highest in the 4.51-5.00 kg class (32.1%), followed by the 4.01-4.50 kg class (30.3%). Length-to-weight relationships for females and males of Asian Seabass indicated positive allometric growth. The correlation between body weight and GSI, using Pearson's correlation, for both sexes, for the male and female barramundi, there was a weak correlation between body weight and GSI, which was 37 and 30%, respectively. Based on the present study's findings, it can be concluded that sex reversal from male to female in Barramundi largely occurred at 4.57 kg body weight and 66.8 cm total length.

Gonad Quality of Banana Shrimp Male Broodstock Penaeus merguiensis (DeMan, 1888) Fed Different Natural Diets

A study was carried out to determine the maturation period, quality and quantity of sperms production in Banana shrimp male broodstock, Penaeus merguiensis fed different natural diets. The three different natural diets namely; squid, fish and shrimp flesh used in this study were obtained from known sources and fed to the tested shrimp in triplicate groups. Based on the results obtained, squid seem to be the most effective natural diet as it enhances the sperms maturation within 20 days. Feeding fish and shrimp flesh as diets for the Banana shrimp broodstock resulted in the observation of maturation in 22 and 24 days, respectively. Similarly, squid diet also recorded the highest (p = 0.002; p < 0.05) sperms count (58.6 to 74.5) as compared to fish diet (44.0 to 61.3) or shrimp diet (28.0 to 42.8). Also, feeding squid diet resulted in a higher percentage of live sperms with ranged between 97.75% to 98.80%. On the other hand, broodstocks fed fish and squid flesh was observed with ranges of between 96% to 97.86% and 92.54% to 96.06%, respectively. It was therefore concluded that squid diet was most effective to improve sperm quality, quantity and maturation period in male broodstock of P. merguiensis. Further study should be carried on the reproductive performance of broodstock fed with squid as diets and it effect on the performances of post larvae obtained.

Histology and External Morphological Assessment on Ovarian Maturation Stages of Wild Female Banana Shrimp, Penaeus merguiensis (de Man, 1888) for Broodstock Selection Purpose

Study on ovarian maturation stages were carried out using external morphological assessment of ovarian colourations and histological assessment of Oocyte structure for broodstock selection purpose. Stage 1 to Stage 4 of female shrimps broodstock were sampled from Kuala Muda, Kedah, Malaysia. Four obvious colourations of ovary stages were identified which are: yellow (Stage 1), green yellowish (Stage 2), light greenish (Stage 3) and dark green (Stage 4) through the morphological assessment. The Gonadosomatic Index (GSI) showed significant increment as the gonad reach advance stages. Histological assessment of Stage 1 ovary identified Perinucleolar Oocyte (PO) with small size oocytes. Stage 2 ovary was identified with Yolkless Oocyte (YO), Stage 3 ovary was identified with late stage of yolky globules and Stage 4 ovary was identified with fully yolky globules. From the results achieved, it can be concluded that the ovarian colourations and GSI can be applied to identify the ovarian maturation stages, meanwhile, the histology assessment is the most precise method to determine the ovarian maturation stages in more details and accurate for each of the ovarian maturation stages.

Thermal Tolerance and Physiological Changes in Mud Crab, Scylla paramamosain Crablet at Different Water Temperatures

Simple Summary

The nursery phase of mud crab (Scylla spp.)—from megalopa to several, further crablet stagesneeds to be carried out in optimal environmental conditions, until they reach a larger size suitable to being stocked to a pond. This study observed the behavioral thermoregulation of crablet instar phases, and determined the effects of several levels of water temperature on growth, survival, molting cycle, gill condition, and sex ratio in the nursery phase of S. paramamosain. In this study, optimal temperature for the long-term nursery phase of S. paramamosain, beginning with megalopa stage, was found to be 28 to 30 °C, with the possibility that water temperature could affect the sex ratio of mud crabs. Findings of this study could result in increased crablet production from hatcheries, and assist in realizing potential of monosex seed production of S. paramamosain, through temperature treatment.

Abstract

This study was carried out to determine the physiological changes (survival, growth, molting cycle, sex differentiation, and gill condition) of mud crab, Scylla paramamosain crablet at different water temperatures of 24, 28 and 32 °C, and ambient temperature of 27 to 30 °C. Thermoregulatory behavior, represented by preferred temperature (29.83 ± SD 2.47 °C), critical thermal minimum (17.33 ± SD 0.58 °C), critical thermal maximum (40 ± SD 0.00 °C), and thermal tolerance interval (22.67 ± SD 0.58 °C), were checked for Crablet 1 stage only (with ambient temperature as acclimation temperature).Both low (24 °C) and high (32 °C) temperatures were associated with lower growth performance, and survival rate (p < 0.05), in comparison with both 28 °C and ambient temperature treatments.Male ratio at low temperaturetreatment (24 °C) was higher (80.09 ± SD 18.86%) than for other treatments (p < 0.05), observed as 44.81 ± D 10.50%, 41.94 ± SD 19.44%, and 76.30 ± SD 5.13% for 28 °C, 32 °C and ambient temperature treatments, respectively. However, there was no significant difference observed between 24 °C, 28 °C, and ambient temperature treatments. Anatomical alterations of gill lamellae of S. paramamosain crablet for both 32 °C, and 24 °C treatments, appeared thinner and paler than at both 28 °C, and ambient temperature treatments. Based on this study, temperature of 28 to 30 °C was recommended as the optimal temperature for the long-term nursery phase of S. paramamosain.

Effects of Biofloc Application on Survival Rate, Growth Performance and Specific Growth Rate of Pacific Whiteleg Shrimp, <i>Penaeus vannamei </i>Culture in Closed Hatchery System

BACKGROUND AND OBJECTIVE

Biofloc application has been introduced in aquaculture in order to reduce the nutrients level and sustain good water quality. Due to its importance, a study was conducted to identify the effect of biofloc application on shrimp growth performance, specific growth rate and survival rate in a closed hatchery system.

MATERIALS AND METHODS

Molasses as carbon sources were applied in ratio 10:1 for biofloc formulation and no addition of molasses in non-biofloc (clear water) treatment. One way ANOVA was applied to analyze the differences between biofloc treatments and clear water.

RESULTS

The survival rate of the shrimp was ranged between 23.69 and 98.77% for biofloc treatment, whereas 98.15-99.23% for non-biofloc treatment. The lowest survival rate (23.69%) was due to vibriosis infection in one of the biofloc treatment tanks. Growth performance was identified expedite in biofloc especially in (dark green) colour biofloc as compared to non-biofloc. The Specific Growth Rate (SGR) for Body Weight (BW) was identified expedite around (3.25-4.06) g day-1 for biofloc treatment compared to non-biofloc around (2.74-3.93) g day-1. The SGR for (TL) also identified expedite around (2.12-2.45) cm day-1 for biofloc, compared to non-biofloc (clear water) around (1.71-2.13) cm day-1.

CONCLUSION

It can be concluded that the biofloc application successfully improved the shrimp performance and at the same time become the additional natural diet to the shrimp respectively. However, further study needs to be conducted to improve the survival rate and prevent vibriosis infection by using the biofloc system in the future.

Dataset on reproductive status of ovary mud crab at different salinity levels

This article investigated how crabs responded to different culture salinities through ovarian maturation stages using combination of external morphology (ovarian coloration and gonadosomatic index), and histological assessment (oocyte structures and diameter sizes). A total of sixty immature crabs were sampled from coastal water of Setiu Wetlands, Kuala Nerus, Terengganu, Peninsular Malaysia, and were introduced to limb autotomy technique in order to induce molt. Crabs were reared until successfully molted, and leaves prior to hardened shell, before proceed with salinities acclimatization prior to salinity treatments (10, 20 and 30 ppt). Five crabs were randomly selected every 15 days throughout 60-day of culture (Day 15, 30, 45 and 60) for the assessment. The different between each ovarian maturation stages was recorded based on the color appearances, and Kruskal-Wallis analysis were done between gonadosomatic index and oocyte diameter sizes with different salinity treatments. Part of the data is associated with the recent articles [1], [2] and provided here as raw data of Supplementary materials.

Histological Characteristics on the Testes of Mud Spiny Lobster, Panulirus polyphagus (Herbst, 1793)

BACKGROUND AND OBJECTIVE

Mud spiny lobsters, Panulirus polyphagus (P. polyphagus) are one of the most important fisheries resources now-a-days due to quality that it's possessed. However, there is still lack of in-depth study about this species mainly on males testicular characteristics and sexual maturity size. Therefore, the present study was carried out to investigate the histological characteristics on the testes and sexual maturity sizes of mud spiny lobster, Panulirus polyphagus.

MATERIALS AND METHODS

The testes were dissected out and fixed in 10% buffered formalin solution for 11 h, dehydrated in 70% alcohol and lastly placed in tissue processor for 18±1 h at 60°C. The tissues blocks were cut at the thickness of 4 μm on a rotary microtome. Stained tissues were taken under Advance Microscope (Nikon Eclipse 80i Nomarski DIC). Collected data were analyzed using Microsoft Excel 2013. Data were presented as mean±standard deviation. Statistical analyses were done using one-way ANOVA using SPSS (Version 22).

RESULTS

These lobules of mature P. polyphagus were formed via different germinative lineage cells such as spermatogonia, spermatocytes, spermatids and spermatozoa. The histological characteristics of testes showed that the process of spermatogenesis went through the stages of four testes maturation which were spermatogonia I and II, spermatocytes I and II, spermatids and spermatozoa stages within different body weight of P. polyphagus. It was found that there were significant difference between body weight and carapace length to the testicular maturation stages (one-way ANOVA and p = 0.000).

CONCLUSION

The results of this experiment indicated that males P. polyphagus have four stages of testes maturation and can be considered to have fully mature testes that ready for fertilization at 452 g body weight (BW) and 107 mm carapace length (CL) or more.

Effect of Water Salinity on the External Morphology of Ovarian Maturation Stages of Orange Mud Crab, Scylla olivacea (Herbst, 1796) in Captivity

BACKGROUND AND OBJECTIVE

Mud crab from the genus Scylla are considered as one of the most demanded seafood items nowadays as their flesh has high quality, tasty and higher growth rate thus support and boosted expansion in aquaculture sector especially in Malaysia. Present study was designed to focus on the effect of water salinity on the ovarian maturation of orange mud crab, Scylla olivacea based on morphological characteristics.

METHODOLOGY

Samples were collected from Setiu wetlands, Terengganu, Malaysia from July-September, 2015. Ovarian maturation of S. olivacea was classified into four stages based on previous study which were: Immature (Stage 1), early mature (Stage 2), late mature (Stage 3) and fully mature (Stage 4).

RESULTS

Morphologically as the ovary develop the colouration start to change from translucent or whitish in colour and sometimes creamy to pale yellow, follow by light orange and lastly reddish orange. Stage 1 ovary was translucent and whitish in colour, stage 2 ovary was pale yellow in colour, stage 3 was light orange and stage 4 ovary was reddish orange in colour. Gonad Somatic Index (GSI) of S. olivacea remained low at stage 1 and 2 and began to increase started at stage 3. This present study involved three different salinities treatments, which treatment 1 (10 ppt), treatment 2 (20 ppt) and treatment 3 (30 ppt). Treatment 2 produce the highest number of stage 4 ovarian maturation based on colouration and the highest GSI recorded, follow by treatment 1 and lastly treatment 3.

CONCLUSION

This present study proved that salinity does affected the ovarian maturation of S. olivacea in captivity and provides important information regarding the effect of water salinity on ovarian maturation for further studies on reproductive biology of this species.