Why in News?
Shellear fish (Parakneria thysi) recently gained attention for their remarkable ability to climb 15-meter (50-foot) vertical waterfalls in Congo (Luvilombo Falls) using specialized fins, a behaviour filmed for the first time after 50 years of local legends.
Anatomy & "Climbing Gear"
- Microscopic Hooks: Their pectoral and pelvic fins are covered in tiny, unicellular hook-like projections called unculi that act like "velcro" to grip wet, slippery rock.
- Muscle Power: They possess hypertrophied muscles and a specialized skeletal structure (pectoral/pelvic girdles) that allow them to support their weight against gravity.
- Locomotion: They don't jump; they use a "swimming-like" lateral wiggle of their rear bodies to push themselves vertically up the rock face.
The Arduous Journey
- Duration: The climb takes approximately 10 hours for a 15-meter ascent.
- Rest Periods: The fish are "sprinters," not marathoners. They move for only about 15 minutes total, spending the rest of the time resting on horizontal ledges to recover energy.
- Size Constraint: Only small individuals (37–48 mm) can make the climb. Once they grow larger (up to 96 mm), they become too heavy for their fins to support their weight.
Purpose of the Migration
- Escaping Predators: Moving upstream allows them to avoid downstream predators like the silver butter catfish.
- Food & Habitat: The climb helps them reach areas with less competition for food and reoccupy habitats after being washed downstream by seasonal floods.
- Seasonal Timing: The migration typically occurs during the major floods at the end of the rainy season in April and May.
Conservation Threats
- Illegal Fishing: Fish are highly vulnerable to being caught with fine-mesh mosquito nets while they wait at the base or during their slow climb.
- Water Diversion: Irrigation projects and dams that divert river water could dry up the waterfalls, essentially "closing the road" for this migratory species.
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