ONTOGENY OF THE BALASHARK Balantiocheilos melanopterus BLEEKER, 1851 (CYPRINIDAE)
Abstract: The Balashark is a
highly praised ornamental species that has been overfished to the point that it
has become endangered in most of its distribution area, especially in
Indonesian waters. Captive propagation has reduced the threats upon wild
populations of balashark. Nevertheless, knowledge on the biology of this
species is still scarce, in particular as regards to its ontogeny. This
information is crucial for the identification of larvae and small juveniles in
the wild, as well as for improving its culture. Balashark eggs average 1.2-1.3
mm in diameter and hatch after 13 hours (26-28°C), giving birth to 4.5-mm
embryos, with a yolk sac of circa 1.1 mm3. At the end of the endogenous feeding
period (day 4 after hatching [AH]), larvae attain 6.3 mm TL. The mouth opens on
day 2 AH (5.8 mm total length, TL). At the time of first feeding (day 4 or 5
AH, 6.3 mm TL), their mouth and gape already average 0.5 mm and 0.27 mm,
respectively, and they grow up to 10.2 and 6.3% TL, respectively, on day 8 AH.
The swim bladder starts forming as early as day 2 AH and is filled by day 3 AH
(5.9 mm TL), but the separation between the anterior and posterior chambers
does not take place before 9.5 mm TL (day 9 or 10 AH). The fin development
sequence is typical of cyprinids, and follows a caudal-to-cranial pattern
(i.e.; caudal, dorsal and anal, pelvic then pectorals), except for the anlagen
of pectoral fins, which are present in 1-day old fish (5.3 mm TL). Based on the
vanishing of the abdominal and caudal fin fold, and on the lengths of the fins
relative to fish size, the transition between the larval and juvenile stage
occurs at circa 17 mm TL (corresponding standard length: 13.7 mm). At this
stage, the scale cover is not developed yet, but juveniles already exhibit the
typical pigmentation pattern of adults on their dorsal, anal, pelvic and caudal
fins, while pigmentation on the pelvic fins is still in its very early stages.
Keywords: Balantiocheilos
melanopterus; cyprinid; ontogeny; morphology; larva
Author: Etienne Baras, Agus
Priyadi, Marc Legendre
Journal Code: jpperikanangg070013
