Fish Harvesting, Post-Harvest Technology and Value Addition
Harvesting
Pond harvest is done by seining with a drag net followed by draining, or by repeated partial harvesting to match market demand. Carps are harvested at about 800 g to 1.5 kg after 8-12 months. Stop feeding 24 hours before harvest, lower the water level, and harvest in the cool hours to reduce stress and injury. Handle fish with wet hands and keep them out of the sun.
Why fish spoil quickly
After death, autolysis and bacterial action follow rigor mortis. Spoilage bacteria and enzymes act fastest at warm temperature, so chilling to near 0 degrees C is the single most effective step. Fish should be washed in clean water, gutted where required, graded, and iced immediately at a fish to ice ratio of about 1:1 by weight, with ice above the fish and drainage holes so melt water runs off.
Quality indices and preservation
- TVB-N should stay below about 30 mg per 100 g; higher values indicate spoilage.
- Fresh fish: firm flesh, bright red gills, clear eyes, no off-odour.
- Methods: icing, freezing at -18 degrees C, salting, drying to low moisture, smoking, canning and retort pouches.
- Value addition: fish pickle, fish curry in retort pouches, fish balls, surimi, fish protein concentrate, fish oil rich in omega-3, and silage or manure from waste.
- Compliance: FSSAI standards and HACCP-based hygiene in processing units.
Worked example
500 kg of carp is harvested for an 8-hour journey. Ice at 1:1 gives 500 kg, but allow about 25% melt loss over the trip, so arrange 500 x 1.25 = 625 kg of ice. Ice must be crushed and layered so it contacts every fish; a solid block with fish stacked at the bottom gives no chilling at all.
Traps that cost marks
- Reversing the ice ratio, so that 2 parts fish to 1 part ice is quoted.
- Drying fish on the ground or on dirty nets, which causes contamination and fly blow.
- Judging freshness only by appearance without citing TVB-N or gill colour.