Changes in some biological parameters of the silver cyprinid, <i>Rastrineobola argentea</i> (Pellegrin, 1904) in the Nyanza Gulf of Lake Victoria, Kenya

Yongo, Edwine; Olukoye, Joshua; Makame, Ali; Chebon, Brian

doi:10.1111/lre.12281

Cited by 5 publications

(5 citation statements)

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“…However, in Lake Naivasha, Outa et al 2014 ( Outa et al 2014 andKeyombe et al 2017 (Table 2). Condition of fish is affected by changes in food availability, environmental quality, seasonality and reproductive status (Yongo et al 2019). The O. niloticus had high condition values during the months of September and October (Fig.…”

Section: Resultsmentioning

confidence: 99%

Population Biology of Nile tilapia (Oreochromis niloticus) in Lake Naivasha, Kenya

et al. 2020

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The Nile tilapia, Oreochromis niloticus was introduced in Lake Naivasha to provide exploitable fisheries. It is one of the commercially important fish providing livelihoods to communities around the lake. However, its stocks in the lake have been declining due to intense fishing, ecological changes and effects of other exotic species. This study investigated on its population and biological parameters. Fish samples (1021) were caught monthly from January to December 2017 using gillnets of mesh-sizes 2-5 inches. A total of 1021 O. niloticus caught had overall sex ratio of 2.21:1.0 (male: female). Length of fish ranged from 9.0 to 40.0 cm TL and weighed between 20 and 1220 g. Length at first maturity (Lm 50 ) was estimated at 28.0 cm TL for all sexes. The mean length and weight for all fish was 22.6 cm and 272.6 g. The slope b of lengthweight relationship was 2.86 for all fish. The mean condition factor was 0.99, 1.04 and 1.01 for male, female and all fish, respectively. The asymptotic length (L∞) was 42 cm, growth coefficient (K) 0.21 year −1 and growth performance index (Ф) 2.57. The natural (M), fishing (F) and total mortality (Z) coefficients were estimated at 0.55, 0.26 and 0.80 year −1 , respectively. Length at first capture (Lc 50 ) was calculated at 19.38 cm. The optimum sustainable yield (E 0.5 ), maximum sustainable yield (E max ) and maximum economic yield (E 0.1 ) indices were 0.23, 0.35 and 0.26, respectively. This study has provided some insights into biology of O. niloticus and stock assessment relevant information to the fishery management.

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Section: Resultsmentioning

confidence: 99%

Population Biology of Nile tilapia (Oreochromis niloticus) in Lake Naivasha, Kenya

et al. 2020

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“…The length–weight relationship and condition factor are also important parameters for assessing the health condition of fish (Mortuza & Al‐Misned, 2013; Nehemia et al, 2012). Accordingly, many studies have emphasized length–weight relationships since they provide information about fish growth patterns, general health, habitat conditions, life history and morphological characteristics (Froese, 2006; Yongo et al, 2019). Fish can attain either isometric, negative allometric or positive allometric growth patterns.…”

Section: Discussionmentioning

confidence: 99%

Length–weight relationship, condition factor, sex ratio and size at first maturity of the blue‐spotted tilapia (Oreochromis leucostictus) in Lake Naivasha, Kenya

et al. 2022

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Oreochromis leucostictus is a commercially important tilapiine in Lake Naivasha, with its stocks having declined because of the effects of fishing, habitat degradation and pollution. The present study investigated its length-weight relationship, condition factor, sex ratio and maturity. Fish samples (233) were collected during 2017, with each fish measured (cm), weighed (g) and analysed for maturity in the laboratory. The mean (±SD) total length and weight were 21.3 ± 0.3 cm TL and 187.4 ± 8.3 g, respectively. The fish exhibited a negative allometric growth pattern (b = 2.33). The mean condition factor was 1.06, 0.99 and 1.04 for male, female and combined sexes, respectively. The condition factor was significantly higher in September (1.70 ± 0.15) and October (1.63 ± 0.15) than in other months. Males were significantly more dominant than females (male:female sex ratio = 2.19:1.0). Females (21.0 cm TL) matured at smaller lengths, compared to males (26.0 cm TL). Comparisons with earlier studies suggested the length-weight relationship, condition factor, sex ratio and size at first maturity of O. leucostictus in Lake Naivasha varied significantly from other tilapiines in various water bodies. The results of the present study provide insights into the biological attributes of O. leucostictus useful for its sustainable management.

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“…All the eggs were weighed (0.001 g), and random samples were weighed and counted. The absolute fecundity (AF) was calculated using the formula described by Yongo, Olukoye, Makame, & Chebon, ():

A F = \frac{italicnG}{g}

where AF = absolute fecundity; n = number of eggs in sub‐sample; G = total weight of the ovaries; and g = weight of sub‐sample.…”

Section: Methodsmentioning

confidence: 99%

“…All the eggs were weighed (0.001 g), and random samples were weighed and counted. The absolute fecundity (AF) was calculated using the formula described by Yongo, Olukoye, Makame, & Chebon, (2019):…”

Section: Materials S and Me Thodsmentioning

confidence: 99%

Biological aspects of Schilbe intermedius (Ruppell, 1832) in the Nyanza Gulf of Lake Victoria, Kenya

2020

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Silver butter catfish (Schilbe intermedius) is an indigenous fish species in Lake Victoria. It has a good economic value because of the quality and freshness of its flesh, increasing its demand for consumption. It is potamodromous, with its stock in the lake declining because of overexploitation by the use of illegal fishing gears at the river mouths on their way to spawning areas. Fish samples (321) were obtained from commercial gill net (1.5–3 in.) fishers within Nyanza gulf. The fish samples were weighed (g) and measured (cm), dissected and sex determined by visual inspection of the gonads. Ovaries for mature female fish specimens were preserved for analysis of fecundity. Fecundity was determined by the gravimetric technique. The mean (±SE) length and weight for all fish were 18.2 ± 0.2 cm TL and 51.9 ± 1.9 g, respectively. The female fish (20.0 ± 0.2 cm) were significantly (F = 199.80, p < .05) larger than the males (15.9 ± 0.1 cm). Similarly, the females (68.8 ± 2.6 g) were significantly (F = 152.61, p < .05) heavier than the males (30.93 ± 1.02 g). The overall sex ratio was 1.23:1.0 (female:male). The length frequency exhibited a unimodal distribution, with the modal class between 16 and 18 cm for either sex. The regression slope (b) of the length–weight relationship was 3.2, 3.1 and 3.0 for all fish, females and males. The absolute fecundity ranged from 6,510 to 59,818 eggs, with a mean of 34,473 eggs. The length at 50% maturity was estimated to be 16.0 cm (female) and 18.0 cm (male) fish. The mean length and size at maturity of S. intermedius have declined, likely attributable to fishing effects, changes in food resources, competition and predation. Thus, the present study provided relevant biological data of S. intermedius, which is currently limited for this region.

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Changes in some biological parameters of the silver cyprinid, Rastrineobola argentea (Pellegrin, 1904) in the Nyanza Gulf of Lake Victoria, Kenya

Cited by 5 publications

References 9 publications

Population Biology of Nile tilapia (Oreochromis niloticus) in Lake Naivasha, Kenya

Population Biology of Nile tilapia (Oreochromis niloticus) in Lake Naivasha, Kenya

Length–weight relationship, condition factor, sex ratio and size at first maturity of the blue‐spotted tilapia (Oreochromis leucostictus) in Lake Naivasha, Kenya

Biological aspects of Schilbe intermedius (Ruppell, 1832) in the Nyanza Gulf of Lake Victoria, Kenya

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