Growth parameters and total mortality in Oreochromis niloticus (Linnaeus) from Nyanza Gulf, Lake Victoria

Getabu, Albert

doi:10.1007/bf00014617

Cited by 34 publications

(26 citation statements)

References 6 publications

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“…(2007) made similar observations, wherein Nile tilapia <30 cm TL dominated the fish catches (68%). The presence of mature individuals, even under heavy exploitation, probably indicates a high resilience of the species and could be one reason that Nile tilapia continued to be dominant in the lake (Getabu 1992; Dache 1994; Njiru et al . 2007).…”

Section: Discussionmentioning

confidence: 99%

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Management of the Nile tilapia (Oreochromis niloticus (L.)) fishery in the Kenyan portion of Lake Victoria, in light of changes in its life history and ecology

et al. 2008

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This study reports on the population parameters, catch distribution and feeding ecology of Nile tilapia (Oreochromis niloticus) from bottom trawls and commercial catches obtained in the Kenyan portion of Lake Victoria during 1997-2006. The population parameters were analysed using the FAO-ICLARM stock assessment tool (FISAT). The fish biomass and the food ingested by the fish were estimated using the swept area and point methods, respectively. Immature fish comprised ഠ70% of the total fish population. The asymptotic length, maximum weight, maximum age, exploitation rate (E) and length at 50% maturity of Nile tilapia have decreased, whereas the growth curvature and fishing mortality have increased. The commercial catches increased from 13.93 t in 1997, to 23.70 t in 1999, decreasing thereafter to 18.73 t in 2005. The bottom trawl catches increased from 46.90 kg ha -1 in 1997, to 401.48 kg ha -1 in 2000, decreasing thereafter to 15.57 kg ha -1 in 2006. The major food items ingested by the fish were algae, insects and other fish. Population parameters, and the catch and diet of O. niloticus, have changed over the years in Lake Victoria. The population characteristics suggest a population under stress, attributable to intense catch exploitation. Even under intense exploitation (E = 0.68), however, the mature fish constituted ഠ30% of the population. The commercial catches are still high, indicating a very resilient fishery. Nevertheless, despite this resilience, the future of Oreochromis fishery is threatened by increased fishing capacity in the lake, and there is need to re-evaluate the effectiveness of current fishery management measures, with the goal of possibly adopting new measures. Enactment of new fishery policies also should provide for co-management to enhance the management process. Furthermore, there is a need to reduce fishing capacity and illegal fishing methods, and to seek alternative livelihoods for lake fishers and other stakeholders.

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Section: Discussionmentioning

confidence: 99%

“…2004). Previous studies of O. niloticus population parameters in Lake Victoria indicated a fishery under intense exploitation (Getabu 1992; Dache 1994; Njiru et al . 2005, 2007).…”

Section: Introductionmentioning

confidence: 99%

Management of the Nile tilapia (Oreochromis niloticus (L.)) fishery in the Kenyan portion of Lake Victoria, in light of changes in its life history and ecology

et al. 2008

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“…With an annual population growth rate of about 3%, high unemployment rate, erratic rains, poor soils, tsetse fly infestation around the lake, which makes farming and keeping of livestock unprofitable, the lake resource remains the main source of livelihood (Yongo et al, 2005). The situation has led to an upward trend in the number of boats, gears and increased 1985-1986(Getabu, 1992 to 0.50 year )1 in 2004-2005. There has also been a reduction in size at first maturity (Lm 50 ) of L. niloticus from 74 cm TL for males and 102 cm TL for females in 1978-1984(Asila & Ogari, 1988, to 54 cm TL for males and 50 cm TL for females in 2004 was reported at an average length of 35 cm TL in the Lake Victoria, Kenya (Getabu, 1992) Continued reduction in sizes of Nile perch could also be attributed to high demand by the processing factories which have a capacity to process Nile perch which outstrips the available fish (Abila, 2000). Due to increased competition for fish, the plants which previously processed fish of 2-3 kg now accepts up to 1 kg.…”

Section: Discussionmentioning

confidence: 99%

Are fisheries management, measures in Lake Victoria successful? The case of Nile perch and Nile tilapia fishery

Njiru¹,

Nzungi²,

Getabu³

et al. 2006

African J Ecol

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“…For different species of the family Cichlidae, there have been studies of reproductive traits (Duponchelle et al, 1999;Gomez-Marquez et al, 2003;Komolafe & Arawomo, 2007), growth (Getabu, 1992;Booth & Merron, 1996;Admassu & Casselman, 2000;Caskey et al, 2007;Bwanika et al, 2007;Gomez-Marquez et al, 2008), and aspects of the fishery (Balirwa, 1992;Jiménez-Badillo, 2004). There is no study of population structure and reproductive maturity by C. beani.…”

Section: Introductionmentioning

confidence: 99%

Population structure and reproductive behavior of Sinaloa cichlid Cichlasoma beani (Jordan, 1889) in a tropical reservoir

et al. 2011

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The population structure and reproductive condition of the Sinaloa cichlid Cichlasoma beani from samples obtained from June 2000 to July 2001 were determined. Samples in the first week each month from the largest trader of tilapia in the Aguamilpa Reservoir in Mexico and were caught in gillnets (9.6 and 11.4 cm stretch-mesh size). Of 596 specimens, there were 427 males and 169 females; monthly sex ratio, frequency of lengths by the multinomial distribution, timing of reproduction, condition index, and size at first maturity was determined. Differences in the sex ratio and monthly totals were significant, favoring males, except for September 2000 and March 2001. From one (August 2000) to three modal groups (July 2000 and June 2001) were identified by size. There were no significant differences in standard length weight relationships by sex, which indicated that a shared model for both genders is appropriate, and isometric growth was detected. Based on the proportion of mature and partially matures fish, the main reproductive period was April through June; size at first maturity was 18.9 cm. Water temperature was not significantly related to the percentage of mature and partially matures Sinaloa cichlids or spawning. These findings provide information for regulating the Cichlasoma beani fishery in this region such minimum legal size and non-fishing period.

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Growth parameters and total mortality in Oreochromis niloticus (Linnaeus) from Nyanza Gulf, Lake Victoria

Cited by 34 publications

References 6 publications

Management of the Nile tilapia (Oreochromis niloticus (L.)) fishery in the Kenyan portion of Lake Victoria, in light of changes in its life history and ecology

Management of the Nile tilapia (Oreochromis niloticus (L.)) fishery in the Kenyan portion of Lake Victoria, in light of changes in its life history and ecology

Are fisheries management, measures in Lake Victoria successful? The case of Nile perch and Nile tilapia fishery

Population structure and reproductive behavior of Sinaloa cichlid Cichlasoma beani (Jordan, 1889) in a tropical reservoir

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