Theory question 105
Fisheries and Aquaculture(a) Give two reasons each for carrying out the following management practices in fish ponds. (i) removal of excessive vegetation. (ii) removal of silt. (iii) supplementary feeding. (iv) fertilizer application.
(b) Mention five conditions that could necessitate culling of farm animals.
(c) State five effects of excess nitrogen in the soil on crops.
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(a)(i) Excess vegetation: prevents oxygen shortage at night; allows light into the water; removes hiding places for predators; makes harvesting easy.
(ii) Silt: keeps the pond deep enough; prevents muddy water; removes toxic gases/organic matter at the bottom; maintains water volume.
(iii) Supplementary feeding: gives fish enough food for fast growth; makes up for scarce natural food; allows higher stocking density; earlier harvest.
(iv) Fertilizer: increases plankton (natural food); increases fish yield; raises productivity of the water.
(b) Any five: old age; low productivity (poor laying, low milk); chronic disease; infertility/sterility; physical deformity or injury; bad temperament; poor growth rate; undesirable traits.
(c) Any five: excessive leafy (vegetative) growth; delayed maturity, flowering and fruiting; weak, soft stems that lodge; greater attack by pests and diseases; poor fruit and seed quality; low yield of tubers/grain; lower keeping quality.
Two reasons for each pond practice.