Practical Skills and Field / Project Work
Practical Skills and Field / Project Work
This domain tests laboratory and field competence: identification, measurement, water testing, gear repair, and project reporting. Marks depend on correct technique and clear records.
Core rules
- Total length (TL) = snout to tip of caudal fin. Standard length (SL) = snout to base of caudal fin (hypural plate). Fork length = snout to caudal fork. State the unit.
- Weigh fish after blotting; zero the balance; record weight to the nearest gram.
- Condition factor K = 100 W / L³, with W in grams and L in centimetres. It indicates plumpness.
- Water testing: collect below the surface, avoid air bubbles, fix samples for dissolved oxygen by the Winkler method, and record time.
- Gear repair: use a netting needle and mesh gauge; keep knots tight and mesh size uniform.
- Project report: title, objectives, methodology, observations, results, discussion, conclusion, references.
Worked example
A fish weighs 250 g and has SL 25 cm. K = 100 × 250 ÷ 25³ = 25,000 ÷ 15,625 = 1.6. A K near 1.0–1.5 is common for many species; 1.6 suggests good condition, but compare with the same species and season. If you mistakenly used TL instead of SL, K would be lower and the comparison invalid.
Traps
Do not measure TL and label it SL; do not record a reading without units; do not leave DO samples exposed to air; and do not present a project without a control or repeat measurement.