Alemayehu, Esayas (2009) Some Aspects of the Biology of Garra dembecha [Pisces: Cyprinidae] and Clarias gariepinus [Pisces: Clariidae] in Lake Hayq, Ethiopia. Masters thesis, Addis Ababa University.
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Abstract
Sex-ratio, length-weight relationship, condition factor, food and feeding habits of Garra dembecha (n=580) and Clarias gariepinus (n=121) in Lake Hayq were studied from monthly samples collected by gillnets of various stretched mesh sizes (3, 5, 8, 10 and 12 cm) and long lines between January 2009 and June 2009. Length of G. dembecha ranged form 8 to 13.3 cm for females and from 8 to 14 cm for males. Length of C. gariepinus ranged from 25 to 77 cm for females and from 20.5 to 50 cm for males. Male to female ratio was in favor of males in the total sample of G. dembecha (1.33:1). Sex-ratio was significantly different from 1:1 in three of the six sampling months and also in the total sample. Female preponderance over males in the total sample of C. gariepinus (1.02:1) was observed. Sex-ratio was not significantly different from 1:1 in the total sample of C. gariepinus. The relationship between total length (range: 8-14 cm) and total weight (range: 6-45 gm) of G. dembecha was found to be curvilinear and statistically significant (p<0.05). The slope b was 3.14 for males and 3.11 for females, which was in both cases not significantly different from the expected value of 3 (t-test, p>0.05).Thus, growth of the fish was isometric. The corresponding equations were represented by: Males: TW = 0.0038x TL 3.144 and Females: TW =0.012x TL 3.109 . The relationship between total length (range: 20.5-77 cm) and total weight (range: 75-3500 gm) of C. gariepinus was found to be curvilinear and statistically significant (p<0.05) and suggesting isometric growth. The slope b was 3.04 for males and 3.27 for females, which was not significantly different from the expected value of 3 (t-test, p>0.05). The corresponding equations were represented by: Males: TW= 0.005x TL3.038 and Females: TW=0.002x TL3.274 . Monthly FCF of G. dembecha in this study ranged from 0.8 to 1.73 for females, and from 0.82 to 1.84 for males. Mean FCF+ SE was found to be 1.25+ 0.02 and 1.33 + 0.01 for females and males, respectively, with an overall value of 1.30 + 0.01. Generally, males had larger FCF values than females. Monthly FCF of C. gariepinus in this study ranged from 0.50 to 1.15 for females, and from 0.48 to 1.10 for males. Mean FCF+ SE was 0.69 + 0.02 and 0.67+ 0.02 for females and males, respectively. The overall Mean + SE FCF was 0.68+ 0.02. Generally females had larger FCF than males. Based on a total of 476 gut samples of G. dembecha, the fish was found to ingest a wide spectrum of food items, ranging from various types of phytoplankton to zooplankton, and to sand particles and detritus. The predominant food items, in terms of frequency of occurrence, were Melosira, Tetraedron, Amphora, Nitzchia, Cymbella, Microcystis, Fragillaria, Cosmarium, Suririella, Navicula and Daphnia. Numerically, Nitzchia, Tetraedron, Cosmarium and Melosira dominated the food of G. dembecha. The contribution of Daphnia was low. Moreover, the fish had ingested detritus, and sand grains. Stomach content samples (n= 121) of C. gariepinus showed that C. gariepinus feeds on a variety of items of both plant and animal origin ranging from phytoplankton to zooplankton, to insects and fish. Macrophyte shoots and detritus were also among the most frequently found items. The predominant food items in terms of frequency of occurrence were crustaceans, followed by insects and fish. Numerically as well, crustaceans (98%) were the most important items followed by insects (0.028%) and fish (0.0045%). Mesocyclops were the most numerous genera in the diet of C. gariepinus (37%) followed by Thermocyclops (31%), Daphnia (14%) and Cerodaphnia (14%). Monthly variation, both in frequency of occurrence and numerical abundance, was also noted in the gut contents of G. dembecha over the period of investigation. Diatoms contributed the highest number in 4 of the 6 sampling months (January to April); while Cyanophyta (40%) in May and Chlorophyta (60%) in June contributed the highest number. Monthly variation among the major food groups was observed in C. gariepinus in the present study. Insects were encountered in greater number of stomachs in the months of January (57%), March (55.56%), April (75) and May (83.33) while Crustacea appeared more frequently in February (77.78%), March (55.56%) and June (77.78%). Fishes were absent entirely in April and June. All the size groups of C. gariepinus ingested all the major food items. This suggests that C. gariepinus, at all sizes, is an indiscriminate feeder in Lake Hayq. However, the relative contribution of items of C. gariepinus varied with fish size. The contribution of insects decreased with increasing fish size, whereas the contribution of zooplankton increased with increasing size.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Condition factor, food and feeding habits, Lake Hayq, length-weight relationship, G. dembecha, C. gariepinus |
| Subjects: | Q Science > QH Natural history > QH301 Biology Q Science > QL Zoology S Agriculture > SH Aquaculture. Fisheries. Angling |
| Divisions: | Africana |
| Depositing User: | Selom Ghislain |
| Date Deposited: | 03 Jul 2018 09:38 |
| Last Modified: | 03 Jul 2018 09:38 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/6241 |
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