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The effect of stunting by feed and space deprivation on compensatory growth (CG) in Silver pompano, Trachinotus blochii, was investigated. A commercial pellet feed (45% protein and 10% fat) was fed two times a day, throughout the entire experiment. The 270-day experiment consisted of an initial 60-day stunting phase and a 60-day post-stunting phase carried out in 4 × 2 × 2 m3 galvanized iron (GI) rectangular cages, and a 150-day grow-out phase carried out in 3-m diameter circular GI cages. During the stunting phase, the normal fish (in triplicates) were stocked at lower stocking density (17 fish/m3) and fed at 10% of body weight (BW), while stunted fish (one replication) were stocked at about three times higher stocking density (56 fish/m3) and fed at a three times lower feeding rate (3% of BW). The stunted and normal fish were reared in triplicates during the post-stunting phase, at uniform stocking density (15 fish/m3) with feeding at a higher rate (10% of BW) for stunted fish and normal feeding rate (8% of BW) was adopted for normal fish. During the grow-out stage, each replication from the post-stunting phase was shifted to 3-m circular cages with the same feeding rates. The lag in growth in stunted fish (5.56 g against 9.43 ± 0.13 g of normal) during the stunting phase was compensated during the post-stunting phase (36.88 ± 2.23 g against 38.13 ± 1.48 g of normal) by higher feeding rate. There were no significant (p > 0.05) differences in final harvest, biometry, morphometry, dressing yield, carcass nutritional composition, and serum biochemical markers at the end of grow-out stage. Because of the significant difference (p < 0.05) in the total feed provided (5.2 kg for stunted fish against 22.8 kg for normal fish) and the lesser unit cost for the production of stunted fingerling (USD 0.087 for stunted fish against USD 0.106 for normal), the farming of stunted fish brought about a higher net operational revenue and benefit:cost ratio.

Orange chromide, Pseudetroplus maculatus is a euryhaline species with both ornamental and food value. The species has several attributes similar to other fish model organisms such as smaller size, repeated breeding, ease of maintenance, and higher fecundity. A salinity tolerance study was performed in different salinities (0, 15, and 35 ppt) in triplicate introducing 10 fishes each (5.4 ± 0.08 g) in 12 plastic tanks of 60 L water-holding capacity. Fish were fed with commercial feed (1.2 mm and 40% protein) at 5% of body weight twice daily for 45 days. No significant variation (p< 0.05) in growth and survival was observed during the study indicating the wide salinity tolerance for the species. Experimental breeding of the species in freshwater and seawater (35 ppt) revealed the ability of the species to breed in varying salinities. Lenience in captive broodstock development, pair formation, and year-round natural breeding makes the seed production of the species easier. Characteristics such as multiple spawnings, a prolonged incubation period (48 to 72 hours) useful for elaborative embryonic studies, shorter larval development cycle (25 to 30 days), and better acceptance of live feed (Artemia nauplii and flakes) and commercial feed by the larvae make the species a potential euryhaline ornamental fish model to assess the physiological changes at different salinities. Minimal input requirements and lower capital and operational investments for the seed production of the species make it an ideal model organism for studying the impact of climatic and environmental changes on fish farming in different habitats.

Histological analysis was carried out on ovarian development in the picnic seabream, Acanthopagrus berda (Forsskål 1775) caught in the estuarine waters of Calicut, Kerala, India from January to December 2016. Four developmental phases of oocyte development were identified viz., oogonia proliferation and transformation into the primary oocyte, primary growth phase, secondary growth phase and maturation phase and these are similar to those described for other species. The reproductive development process begins in a very young ovary with the formation of oogonia, the cells originally derived from special primordial germ cells formed early in the embryonic development; their multiplication and differentiation are followed by the release of mature oocytes. Oocyte development stages observed in A. berda were chromatin nucleolus, early perinucleolar, late perinucleolar, lipid vesicle stage I oocyte, lipid vesicle stage II oocyte, primary yolk granule stage, secondary yolk granule stage, tertiary yolk granule stage, hydrated oocyte and atretic oocyte. The oocytes entered the maturation phase when they attained the maximum size of 459.6±71.83 µm. Histological examination of the mature ovaries showed the presence of all the different oocyte stages in the ovary of A. berda with an asynchronous mode of ovarian development shortly before spawning, indicating that the species is a multiple spawner. [ABSTRACT FROM AUTHOR]

Gonadal assessment of Acanthopagrus berda (Forsskål 1775), a commercially and recreationally important fish from Indian waters, was studied by collecting 250 fishes from the Korapuzha estuary, Calicut, Kerala using cast net during December 2015 to January 2016. External morphology of the gonads reveals that A. berda is bisexual (with ovo-testis) in nature with the ovarian lobe in the mid-dorsal region of the abdominal cavity and the testicular lobe as a band along the ventro-lateral wall with a major portion running along the extreme posterior region of the gonad. Males were dominant in lower length classes (17-23 cm) while females dominated in upper length classes (24-43 cm), confirming protandrous hermaphroditism in the species. Gonado-somatic index (GSI) was significantly higher (P<0.05) for the females. Males and transitional groups were showing almost similar GSI. External morphological and histological evaluation of the gonads of A. berda during the 2-month study revealed the presence of different developmental stages such as matured testis with oozing milt, an intermediate gonad structure with an anterior thin ovary-like structure and a posterior thick testis-like morphology indicating a transitional ovo-testis, maturing ovary and matured ovary. The simultaneous availability of milt oozing males and matured females from the wild indicates the opportunity for development of captive breeding, seed production and hatchery technology for this important commercial food fish. [ABSTRACT FROM AUTHOR]