Observation

This question was attempted by many candidates and their performance was generally poor. In Questions 4(b) many candidates confused inbreeding with induced breeding. In Question 4(c) very few students answered this question and many could not draw a proper cross-section of a fish pond. In Question 4(d), most candidates did not scorethe full mark because they only wrote one point instead of two.

The expected answer is as follows:

(a)        Effect of high turbidity in fish ponds
                       
-           Reduced light penetration leading to reduced photosynthesis
-           Clogging of fish gills thereby reducing respiration and uptake of oxygen
-           Low dissolved oxygen
-           It affects fish growth
-           It reduces natural fish food
-           It causes eventual death of fish


(b)        (i)         Definition of inbreeding of fish

It is the mating of close relatives in fish./
It is the crossing/ mating of fish offspring of the  same parents or with the same genetic make up

(ii)        Quality of a good broodstock

                        -           Ability to be induced/ reproduce in captivity
-           Ability to produce numerous and hardy eggs and larvae
-           Should be hardy/ active/ adaptable to different culture systems
-           Have good feed utilization ability
-           Should be easy to handle
-           Should be without defect
-           Should be resistant to disease
-           Should have fast growth rate
-           Ability to accept both natural and artificial feed
                                                                                                           
(c)        Cross section of a fish pond

                                                                                    
d)         Explanation of terms in aquaculture

(i)         Partial Harvesting

                        -           It is the type of harvesting where bigger fish are removed to allow
smaller ones space to grow
-           Usually the pond water is not drained/ partially drained
                                                                                                                  
(ii)        Total Harvesting

-           This is the method of harvesting where the pond water is drained and the fish collected either with hand, net or bowl.
-           All the fish are usually collected/ removed