STUDIES ON THE PREDATORY POTENTIAL OF SOME FISH SPECIES ON MOSQUITO LARVAE IN SOME PARTS OF NORTHERN NIGERIA
STUDIES ON THE PREDATORY POTENTIAL OF SOME FISH SPECIES ON MOSQUITO LARVAE IN SOME PARTS OF NORTHERN NIGERIA
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Date
2014-06
Authors
AUTA, Bitrus
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Abstract
This study was designed to evaluate the larvivorous potential of some indigenous fishes for the control of mosquito larvae and by extension, the adult mosquitoes. Twelve (12) fish species were collected from streams, rivers, ponds, swamps, ditches, reservoirs, lakes and dams in parts of northern Nigeria using hand nets, cast nets, drag nets and malian traps. These fishes were evaluated in the laboratory against the number of Culex quinquefasciatus larvae that each can consume in 24 hours, from which their predatory indices (PI) were computed. Similarly, the ability of nine of the fish species to prey on mosquito larvae in outdoor concrete ponds was evaluated for 12 months. Fish hardiness was measured by the ability to survive without being fed for five months (20 weeks), ability to survive under extreme pH, and ability to survive in different water volumes for 13 weeks. The fish species were bred under static and flow-through systems. Furthermore, Clarias galmaensis hatched in the laboratory using ovaprim hormone was tested for larvivorous efficacy at 5, 7 and 9 months. All the fish species evaluated preyed on mosquito larvae, but the consumption rate varied with species, the differences in the consumption rates among the 12 fish species were significant at P<0.05. The PI/ the mean number of mosquito larvae consumed per day by each of the fish species were as follows: Poecilia reticulata 265.00/53; Clarias gariepinus 101.36/223; Clarias galmaensis 49.40/988; Epiplatys spilargyreius 45.00/18; Hemichromis bimaculatus 35.96/187; Oreochromis niloticus 35.12/144; Leptocypris niloticus 29.33/88; Schilbe mystus 26.60/125; Synodontis ouemeensis 24.67/74; Brienomyrus niger 17.00/51; Astatotilapia burtoni 7.80/39 and Brycinus nurse 3.29/28. The number of larvae consumed by each of these fish species was lower when commercial feed was added but t-test showed that the differences were not significant (P>0.05). Except for ponds that contained Brienomyrus niger, Brycinus nurse
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and Synodontis ouemeensis, all other ponds were devoid of larvae throughout the test period of 12 months. The lowest pH tolerated by the fish was 3.16, by Astatotilapia burtoni and the highest was 11.85, by Brycinus nurse. No fish species had mortality of more than 50 percent when starved in the laboratory for five months. Mortalities recorded among the different fish species kept in 10, 20 and 30 litres of water for 13 weeks were generally low; in six of the 12 fish species no mortality was recorded; in all, only 15 (5.21%) out of 288 fish died. Poecilia reticulata bred in the static and flow-through system and Epiplatys spilargyreius in the laboratory all year round. Poecilia reticulata, Clarias gariepinus, Clarias galmaensis, Epiplatys spilargyreius, Hemichromis bimaculatus, Leptocypris niloticus, Oreochromis niloticus and Schilbe mystus showed promise as good predatory agents for mosquito larvae with the potential that could be harnessed for the control of mosquitoes and consequently the diseases they transmit.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF
DOCTOR OF PHILOSOPHY DEGREE IN ZOOLOGY
DEPARTMENT OF BIOLOGICAL SCIENCES,
FACULTY OF SCIENCE,
AHMADU BELLO UNIVERSITY,
ZARIA NIGERIA
JUNE, 2014
Keywords
PREDATORY,, POTENTIAL,, FISH,, SPECIES,, MOSQUITO,, LARVAE,, NORTHERN NIGERIA