Effect of different maturation diets on reproductive performance of the broodstock of purple mangrove crab, Scylla tranquebarica

The present study was aimed at evaluating the reproductive performance of the broodstock of purple mangrove crab (Scylla tranquebarica) fed natural food and formulated diets supplemented with astaxanthin and/or DHA. Formulated diets were supplemented with 500 mg kg-1 of astaxanthin (FA), 10 g kg-1 of DHA (FD) and both astaxanthin and DHA (FA+D). Diet without astaxanthin and DHA (FCon) and natural food (NF) consisted of forage fish (Valamugil sp.), shrimp (Penaeid sp.) and mangrove clam (Polymesoda sp.) to serve as control. Female broodstock of initial body weight 129.07±17.03 g were stocked in HDPE tank and cultured under recirculating water system. Broodstock maturation was monitored until spawning. Reproductive performance of female and condition of the larvae were also evaluated. After 50 weeks, broodstock fed FA+D diet showed better maturation percentage, spawning rate, gonadosomatic index, oocytes diameter, molting, molt death syndrome and survival rate than FCon group (P0.05) to the FA+D group but diet FD resulted in better performance than FA. Broodstock fed FA+D diet had the highest hatching rate, number of larvae produced and significantly higher zoea II survival compared to FCon and NF groups (P<0.05). No significant difference was observed in hatching rate and zoea II survival rate when broodstock were fed FA+D, FA and FD diets. This study indicated that DHA as well as astaxanthin improved the reproductive performance of the mangrove crab, and the use of both DHA and astaxanthin further enhanced the maturation performance

Sensory systems and feeding behaviour of the giant freshwater prawn, Macrobrachium rosenbergii, and the marine whiteleg shrimp, Litopenaeus vannamei

Information on the sensory basis of shrimp feeding provides the means for assessment of the effectiveness of food items in terms of smell, taste, size, and colour. This chapter summarizes information about the sensory basis of the feeding behaviour of the giant freshwater prawn (Macrobrachium rosenbergii) and the marine whiteleg shrimp (Litopenaeus vannamei). Existing literature on these shrimp species and other decapod crustaceans is reviewed, and unpublished experiments using the selective sensory ablation technique to determine the involvement of vision, chemoreception, and touch sense in the feeding behavior of the juveniles of M. rosenbergii and L. vannamei are also described. To determine the role of vision in feeding, the eyes of the juveniles were painted over (deprived of vision) with white manicure and their feeding response to commercial pellets was compared with those with untreated eyes. The untreated eyed juveniles detected and approached a feed pellet right away, but the specimens blinded by the coating detected a pellet only after random accidental touch with the walking legs while roaming on the aquarium bottom. Juveniles that had learned to feed on pellets showed food search and manipulation responses to a pellet-like pebble without smell and taste. The early larvae (zoeae) of M. rosenbergii already have colour vision (that likely persists through life) and colour preference for blue and white. The adults of L. vannamei discriminated a blue-colored well among seven grey wells in a palette, also showing colour vision in this shrimp. A behavioural experiment with dyed prawn flesh showed that L. vannamei has innate color preference for yellow food over black, red, green, and blue food regardless of the background colours of the aquarium bottom. To disrupt chemoreception, the juveniles of both the species were abruptly transferred to water of drastically different salinity and the osmotic ablation destroyed the chemosensitive sensilla. The osmotically ablated juveniles approached a pellet right away but failed to ingest it; they had learned the visual cue and texture of the pellets and recognized them by vision and tactile sense. To determine the role of sensory appendages in feeding of L. vannamei juveniles, the antennal flagella, antennular flagella, and the pincers of the pereiopods were ablated. The ablated juveniles roamed the bottom, touched a pellet at random, grabbed it with the maxillipeds, and ingested it. Subsequently they learned to lower the head, actively swim forward, sweep the bottom with the maxillipeds, detect a pellet, and ingest it—thus indicating a plasticity in feeding behaviour in L. vannamei

Terrestrial animal- and plant-based ingredients as alternative protein and lipid sources in the diets for juvenile groupers: Current status and future perspectives

The Epinephelinae groupers are strict carnivorous species. They are widely cultured in the Asia Pacific region as a result of high demand and market price especially in the live reed food fish trade. Groupers are commonly raised in net cages and fed with the unsustainable low value fish. Although this feeding practice has been gradually improved by using formulated diets, the production cost of these diets is high due to the increasing prices of fish meal and fish oil. In order to find sustainable replacements for these expensive commodities, research has been conducted to evaluate alternative ingredients effects on fish growth performances and immune function. This review covers different types of alternative ingredients tested on several species of juvenile grouper. In general, animal protein sources were able to replace fish meal at higher inclusion levels than plant protein sources. Lowered digestibility, deficiency in essential nutrients, and reduced palatability are major challenges in using alternative ingredients in grouper feeds

Dietary ascorbic acid requirement for the optimum growth performances and normal skeletal development in juvenile hybrid grouper, Epinephelus fuscoguttatus × Epinephelus lanceolatus

A 10-week feeding trial was conducted to determine the dietary ascorbic acid required by the juvenile hybrid grouper, Epinephelus fuscoguttatus × Epinephelus lanceolatus for its optimum growth, survival, and normal skeletal development. Eight experimental diets containing graded levels of ascorbic acid (4.8, 11.2, 24.1, 47.2, 75.6, 95.4, 156.2, and 303.0 mg/kg) were prepared and labeled as C5, C11, C24, C47, C76, C95, C156 and C303, respectively. Each diet was fed to triplicate groups of fish [initial weight 7.71 ± 0.06 g (mean ± SD)]. The fish were cultured in 150 L of fiber glass tank supplied with aeration and flow-through seawater system (3 L min−1) with the stocking density of 15 individual per tank. During the feeding trial, fish were hand-fed with the experimental diets to apparent satiation twice a day (8:00 and 15:00). Bulk weight of each fish group was measured at 2 weeks interval. At the end of the experiment, fish were sacrificed and subjected to radiographic imaging to detect the presence of skeletal deformities. The body weight gain (BWG) of fish was in the range from 628.51 ± 39.61 to 880.18 ± 113.30%. Fish fed with the C156 diet gained the highest BWG and specific growth rate (SGR). In the present study, ascorbic acid level did not affect the survival of the hybrid grouper. The feed conversion ratio (FCR) value in all dietary treatments appeared to be less than 1, indicating hybrid grouper have high efficiency of converting feed into body mass. Multiple types of skeletal deformities (fusion, kyphosis, lordosis, and scoliosis) were observed in the fish fed with the diets containing less than 95 mg/kg of ascorbic acid. In conclusion, dietary ascorbic acid levels can affect the growth performance and normal skeletal development in the hybrid grouper. Although 95 mg/kg was sufficient for normal skeletal development, 156 mg/kg of dietary ascorbic acid is recommended for feed development to maintain the optimum growth and normal skeletal development in the fish

Supplementation of duckweed diet and citric acid on growth performance, feed utilization, digestibility and phosphorus utilization of TGGG hybrid grouper (Epinephelus fuscoguttatus x Epinephelus lanceolatus) juvenile

A feeding trial was conducted in juvenile TGGG hybrid grouper to investigate the growth performance, feed utilization, and digestibility after citric acid supplementation in a diet that was partially composed of duckweed. Five isoproteic and isolipidic diets (50% protein, 16% lipid levels) were formulated using Lemna minor and Spirodela polyrrhiza at 5% of fishmeal protein replacement level with or without 3% of citric acid supplementation. A diet without duckweed and citric acid was used as the control diet. Triplicate groups of fish (10.30±0.05 g) were randomly distributed in tanks with a flow through system at a stocking density of 20 fish per tank. The fish were fed twice daily with each experimental diet until apparent satiation for 10 weeks. As a result, the fish fed a diet with duckweed S. polyrrhiza and citric acid (DSC) achieved significantly higher growth, body weight gain (BWG) and specific growth rate (SGR) compared to the control group (P<0.05); however, it was not significantly different with other treatments (P>0.05). The growth, BWG and SGR in fish fed duckweed diets only (L. minor and S. polyrrhiza) were almost similar with the control without significant differences (P>0.05). Similarly in feed utilization, fish fed the DSC diet had a better feed conversion ratio, protein efficiency ratio, and net protein utilization without significant differences (P>0.05) compared to the control. The apparent digestibility coefficient for crude protein and crude lipid, and phosphorus absorption of DSC and the diet with duckweed L. minor and citric acid were comparable to the control without any significant differences (P>0.05). Survival was not affected by the experimental diets. This study showed that TGGG can utilize a diet partially composed of duckweed and better performance was observed with the aid of citric acid

Shelter colour preference in the purple mud crab Scylla tranquebarica (Fabricius)

Cannibalism a serious problem in the grow-out of mud crabs in ponds. Studies have proven that presence of shelters decreases aggressive behaviour of Scylla spp. in ponds and tanks. In this study, the shelter colour preference was determined in the wild captured purple mud crab Scylla tranquebarica (Fabricius) in an outdoor round black tank. Eight out of 48 PVC pipes were painted either blue, green, red, black or white. Other eight were not painted and were provided as grey shelters. The shelters were presented in different two-colour pairs to a group of 35 crabs; eight shelters of one colour and eight of other colour were arranged alternately on the tank bottom, and the number of occupants was recorded. After emptying the shelters, the shelters rearranged for the next observation. Each colour combination was repeated five times, and total of 15 combinations were tested. The number of occupants against each colour of the different pairs were analyzed by the χ2-test and Thurstone’s law of comparative judgment. The data were converted into mean z-scores and significant biases from zero were noted. Underwater visibility of each colour shelter was visually measured through a waterproof digital CCD camera. The crabs showed a strong bias for blue shelter and white shelter chosen the least under the holding condition. The underwater visibility was highest in blue and white colour shelters among the six colour shelters. The observed colour preference was probably due to colour per se and may be an innate ability, rather than due to relative underwater visibility. During the observations, the shelter occupants were tolerant of intruders; there was no aggressive competition for shelter and two to four crabs shared one shelter. It was hypothesized that the touch stimulus of shelter suppresses the aggressiveness and results in low cannibalism of S. tranquebarica

Broodstock condition and egg quality in tiger prawn, Penaeus monodon, resulting from feeding bioencapsulated live prey

This study was motivated by the need to find a solution to poor egg quality and the resulting mass mortality of hatchery-produced larvae of the tiger prawn, Penaeus monodon. The approach adopted sought to improve the broodstock condition and determine its effect on egg quality using rates of fertilization, hatching and metamorphosis. Broodstock specimens were given four separate dietary treatments (D1–D4), all of which comprised squid and trash fish plus supplements. D2, D3 and D4 were supplemented with bloodworm, bioencapsulated bloodworm and a commercial broodstock diet, respectively. Tricalcic phosphate (Ca3(PO4)2) was used to enrich the live bloodworm. The bioencapsulated ration performed better than regular bloodworm and other diets. This was evident from the bioencapsulation results which showed the highest rate of hatching, survival of nauplii and larvae metamorphosing into zoea stage