Diet composition, feed preferences and mouth morphology of early stage silver therapon (Leiopotherapon plumbeus, Kner 1864) larvae reared in outdoor tanks
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This study examined the diet composition, feeding preferences, and mouth morphology of the silver therapon (Leiopotherapon plumbeus, Kner 1864) larvae under captive conditions. Larvae were reared in outdoor tanks (4 m3) with natural food grown 2 weeks prior to start of larval rearing. Food preference was measured by the Chesson's electivity index (αi). Gut content analysis of larvae sampled between 5 and 25 days after hatching (DAH) showed the dominance in the diet by zooplankton, mainly copepod nauplii, cladocerans and insect larvae. Small fish larvae (5–9 DAH; 3.32–6.29 mm standard length) preferred cladocerans, ciliates and copepod nauplii; whereas older larvae (12–25 DAH; 5.45–19.26 mm standard length) preferred insect larvae over cladocerans and adult insects. The mouth gape size at 5 DAH was 359 μm and increased to 3.75 mm at 40 DAH when body size grew at an average rate of 0.59 mm d−1. The standard length (SL) of L. plumbeus larvae was strongly associated with mouth size (r2 = 0.98, P < 0.05), indicating a progressive increase of ingested prey size of the fish larvae. These results clarified the early life feeding ecology of this species, which is essential in developing effective hatchery techniques.
CitationAya, F. A., Corpuz, M. N. C., & Garcia, L. M. B. (2015). Diet composition, feed preferences and mouth morphology of early stage silver therapon (Leiopotherapon plumbeus, Kner 1864) larvae reared in outdoor tanks.
Plankton surveys; Animal morphology; Insect larvae; Length; Food preferences; Biometrics; Nutrition; Fish larvae; Protists; Diets; Feeding; Zooplankton; Ciliates; Dominance; Hatcheries; Digestive system; Body size; Mouth; Hatching; Predation; Leiopotherapon plumbeus; Copepoda; Leiopotherapon; Therapon; Cladocera
The study was funded by the SEAFDEC Aquaculture Department (Study Codes Nr-04-F2010B and Nr-01-F2013B) and UP Natural Sciences Research Institute (Project Codes BIO-09-2-06 and BIO-13-2-04).
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Growth response of cultured larvae of silver therapon Leiopotherapon plumbeus (Kner, 1864) in outdoor tanks in relation to fertilizer type and fish density This study evaluated the effects of fertilizer type and fish density on early growth and survival of silver therapon Leiopotherapon plumbeus (Kner, 1864) larvae reared in outdoor tanks. In the first experiment, larvae (1.92 ± 0.09 mm total length) were stocked into nine, 4 m3 tanks at an initial density of 0.5 larvae L-1 and reared for 42 days at an ambient temperature of 28.8–30.7°C. Three treatments with three replicates each were compared: organic (chicken manure, OF) or inorganic fertilizers (ammonium phosphate, IF) applied once every 2 weeks, and the unfertilized (NF) tanks serving as the control group. Water quality, zooplankton densities, survival or growth of L. plumbeus larvae did not vary significantly in either fertilized or unfertilized tanks. Fertilization resulted in elevated nutrient concentrations, which did affect survival (2.10%–6.07%) of the fish larvae. In the second experiment, larvae were stocked at densities of 0.4 or 0.6 larvae L-1 in tanks fertilized at 4–5 days interval with OF and IF for 30 days. Growth performance of L. plumbeus larvae was affected by fish density, with significantly larger (20.04 ± 2.65 mm in total length) and higher specific growth rate (SGR; 6.97 ± 0.48% day-1) at 0.4 larvae L-1 than at 0.6 L-1. Fry production did not vary significantly between fish density treatment groups given the same fertilizer types, but survival rates were improved at 0.4 L-1. Together, production of L. plumbeus larvae in outdoor tanks can be optimized at a lower stocking density, regardless of the type of fertilizer used.
Morphological development and survival of Philippine silver therapon larvae, Leiopotherapon plumbeus (Kner, 1864) reared under different feeding schemes JAP Añano & MRR Eguia - In Proceedings of the DLSU Research Congress 2016, De La Salle University, Manila, Philippines, March 7-9, 2016, 2016 - De La Salle UniversityPhilippine silver therapon, Leiopotherapon plumbeus, locally known as ayungin, is an endemic fish species in the country. The demand for silver therapon remained high despite the decline of its population and commercial catches. Taking into account the potential of this species for stock enhancement, this study focused on developing an initial feeding strategy necessary to provide potential L. plumbeus juveniles for aquaculture. The experiment conducted was a short duration 10-day feeding experiment which used different feeding schemes utilizing live food organisms [Brachionus (B), Moina (M), co-fed with BM, Chlorella (C) and filtered lake water (L)]. Morphometric measurements were evaluated to assess growth performance of larvae among different feeding schemes. Survival rate was determined at the end of feeding experiment at 9 DAH (days after hatching). Growth parameters of L. plumbeus larvae reared under different feeding schemes showed significant differences starting at 5 DAH (P < 0.05) onward. After a total of 10 days, a significant decline in fish larval samples was observed under two feeding schemes (C and L). BM has a significant higher rate of survival (18.07 ± 7.09%) compared to other treatments. B. rotundiformis (15-20 mL-1) can be considered as a starter food for silver therapon larviculture and M. micrura (5-10 mL-1) can be utilized during an assumed co-feeding phase at 6 DAH.
Embryonic and larval development of hatchery-reared silver therapon Leiopotherapon plumbeus (Perciformes: Terapontidae) The embryonic and larval development of hatchery-reared silver therapon Leiopotherapon plumbeus are described to provide essential information on the early life history of this species. Egg size, larval size at hatching, yolk resorption rate, onset of feeding and development of some morphological characters were examined. Fertilized eggs (430–610 µm in diameter) were spherical, yellowish, demersal and slightly adhesive. First cleavage occurred 6 min post-fertilization and embryos hatched 21–24 h post-fertilization under ambient temperature of 27.5 ± 0.1 °C. Newly hatched larvae [1.79 ± 0.04 mm in total length (TL)] with yolk volume of 0.579 ± 0.126 mm3 had no functional or pigmented eyes, mouth or digestive tract. The eyes became fully pigmented and mouth opened [31 and 36.5 hours post-hatching (hph)] shortly before yolk resorption at 39 hph and when larvae had grown to 2.65 ± 0.14 mm in TL. Some morphological characters such as total length, pre-anal length and eye diameter decreased following yolk resorption, which also coincided with the development of foraging capacities shortly before exogenous feeding was initiated. L. plumbeus larvae initiated exogenous feeding at 54 hph, indicating a short (15 h after yolk resorption) transitional feeding period. Larval growth at the early stages of development (54–72 hph) was rapid and steadily increased from 288 to 720 hph, when larvae, 12.05 ± 4.02 mm in TL, closely resembled the external characteristics of their adult conspecifics.