Practical Work and Field Exposure
What the exam tests
Practical work tests hands-on skills and accurate recording. Expect questions on water sampling, dissolved oxygen, pH, plankton, fish dissection, feed formulation, pond preparation, netting and hatchery observation.
Core rules
- Collect water samples below the surface, avoid air bubbles, label bottles and test promptly.
- The Winkler method measures dissolved oxygen by fixation and titration; starch is the indicator.
- Use a Secchi disc for transparency and a plankton net for qualitative samples.
- Dissection should reveal gills, heart, liver, intestine, swim bladder and kidney; identify organs without damaging them.
- Pearson square formulates feeds from two ingredients to a target protein level.
- Pond preparation includes drying, liming, manuring and screening inlet water.
- Record dates, measurements, units and observations; poor records lose marks.
Worked example
Make a 30 percent protein feed from ingredient A at 40 percent protein and ingredient B at 20 percent protein. Pearson square: parts of A = 30 - 20 = 10; parts of B = 40 - 30 = 10. Ratio A:B = 10:10 or 1:1. Reasoning: the target lies midway, so equal parts are needed. For 100 kg feed, use 50 kg of each.
Traps
Do not trap air in DO bottles. Do not read the meniscus incorrectly. Do not use wet and dry weights interchangeably. Do not leave samples unlabelled. Do not dissect without a labelled diagram.
Key facts
Use calibrated pH meters. Rinse electrodes with distilled water. Preserve plankton samples with formalin if needed. Keep a field notebook.