Borneo river shark

📖 Overview

The biology of this species is essentially unknown; development presumably by placental viviparity as suggested by the newborn young and by reference to other, related carcharhinids (adults of either sex including pregnant females were not available for examination). The type locality was described to have very low banks that slope gradually down to a flat and muddy bottom. Little information available on the hydrology of the area, however, the Lower Kinabatangan Segama Wetlands RAMSAR site (available at http://www.sabah.gov.my/sabc/downloads/RIS_LKSW_2008.pdf) provides the following hydrological characteristics for the streams of the Kulamba Wildlife Reserve where Kampung Abai is located: salinity 1.7-1.9, pH 6.4-7.5, temperature 25.5-29.9°C, conductivity 27.6-31.2 μS/cm, total suspended solids 126.8-214.5 mg/L, dissolved oxygen 4.6-5.9 mg/L and the most important features to take note of are the very low salinity (practically freshwater) and high suspended solids .

🔬 Taxonomy

🐟 Physical Description

This species is distinguished by the following combination of characters: snout short, broadly rounded in dorsoventral view; minimum distance from mouth to nostril 1.1-1.6 times nostril width; lips usually concealing teeth when closed mouth; lower teeth with erect, narrow, moderately hooked to straight cusps, with notched mesial and distal edges, and low mesial and distal shoulders or blades (except in posterior teeth); anteroposterior tooth row counts 13-15/13-15; total tooth row counts 28-31/29-32 or 60-63; interdorsal space 17.0-19.5% TL; anterior margin of pectoral fin slightly convex, pectoral length 11.6-13.4% TL; length of pelvic-fin anterior margin 6.3-7.7% TL, 36-40% of length of pectoral-fin anterior margin; pelvic-fin height 4.6-6.3% TL; first dorsal fin not falcate, with concave posterior margin, free rear tip just anterior to pelvic-fin origins, its length 16.9-19.1% TL; second dorsal-fin length 10.5-12.3% TL, anterior margin length 7.5-9.7% TL, its base length 7.4-9.3% TL and 1.4-1.9 times second dorsal-fin height, its height 4.7-6.0% TL and 58-68% of first dorsal height; anal-fin height 4.1-5.0% TL and 74-102% of second dorsal-fin height, its base 65-94% of second dorsal-fin base; caudal-fin subterminal margin weakly concave; total vertebral count 196-209; monospondylous precaudal count 60-67, 30-33% of total count; diplospondylous precaudal count 43-52, 22-26% of total count; diplospondylous caudal count 82-96, 42-46% of total count; precaudal count 108-114, 54-58% of total count; boundary coloration (watermark) on head diffuse, extending through lower level of eye; in young, watermark well defined, diffuse along trunk, situated near lateral midline; dorsal, pectoral, pelvic and anal fins plain; ventral caudal-fin lobe, and postventral and dorsal margins, dusky to blackish .: fusiform / normal.

🌀 Behaviour

Behavioural data for Borneo river shark is currently being reviewed.

🦐 Diet

🥚 Reproduction

🌍 Habitat & Distribution

Freshwater; pelagic. Tropical

🌿 Ecology

📐 Morphometrics

🌡️ Water Parameters & Tolerance

📊 Population Risk & Fisheries

🐠 Related Species

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