Population parameters and exploitation rate ofSarotherodon galilaeus galilaeus(Cichlidae) in Lakes Doukon and Togbadji, Benin

Abstract

Growth, mortality, recruitment and relative yield per recruit of Sarotherodon galilaeus galilaeus from Lakes Doukon and Togbadji were studied. Data on total length, total weight and sex were recorded on a monthly basis between January and December 2013 for S. g. galilaeus captured by local fishers. The estimated asymptotic lengths L" were 26.2 and 23.6 cm for Lakes Doukon and Togbadji, respectively, while the growth rate K was 0.73 in Lake Doukon and 0.87 in Lake Togbadji. Estimates of fishing mortality, 0.27 and 0.47 y -1 for Doukon and Togbadji, respectively, were low relative to natural mortality, 1.51 and 1.74 y -1 , respectively. Sizes at first sexual maturity were 12.8 and 13.2 cm for females and males, respectively, in Lake Doukon, and 11.5 and 12.4 cm for females and males, respectively, in Lake Togbadji. The size at first capture was estimated at 13.3 and 12.7 cm for Lakes Doukon and Togbadji, respectively, which, in the light of the size at maturity estimates, indicates that fish spawn at least once before capture. The current exploitation rates of 0.15 for Lake Doukon and 0.21 for Lake Togbadji suggest that their stocks of S. g. galilaeus are not overexploited in either lake.

Assessing the exploitation status of main fisheries resources in Ghana’s reservoirs based on reconstructed catches and a length-based bootstrapping stock assessment method

“…sector of Ghana. However, studies on the same species in Doukon and Togbadji reservoirs in Benin by Lederoun et al (2016) depict a larger asymptotic length, while the K estimates are comparable to those reported in this study (Table 8). The growth parameters of the target species estimated in our study are also similar and comparable to those reported for C. zillii and O. niloticus in a previous study of the Bontanga Reservoir by Ofori-Danson et al (2008) but differ for S. galilaeus.…”

“…The desirable target would be to let as many fish as possible spawn at least once before they are caught, to rebuild and maintain healthy spawning stocks (Froese 2004). The total length at first sexual maturity was based on published research on the species (Adite and Van Thielen 1995, Akongyuure et al 2017b, Duponchelle and Panfili 1998, Kwarfo-Apegyah and Ofori-Danson 2010, Lederoun et al 2016, Ofori-Danson et al 2008.…”

Gillnet selectivity estimates for five commercially important fish species in Tono Reservoir, Northern Ghana

“…The results of the current study do not differ greatly from those of Lederoun et al . (), who reported the sizes at first sexual maturity of female S. galilaeus were 12.8 cm in Lake Doukon and 11.5 cm in Lake Togbadji in Benni. In contrast, the results of the present study disagreed with those of Adams et al .…”

Biodiversity and Fish Reproductive Aspects of the Sô River in Southern Benin.

“…Benin is a coastal country with a river-rich watershed, especially in its southern part. The SÔ River, located northwest of Nokoué Lake in the municipality of Sô-ava, like the other rivers of the country, is subject to the action of local populations whose main activity is fishing (Lederoun et al, 2016).…”

“…However, the widespread use of non-regulatory fishing gear, techniques and fishing methods is leading to the degradation of aquatic ecosystems. Fishing is one of the causes of the degradation of river biodiversity (Lederoun et al, 2016. The intensification of the exploitation of freshwater and brackish water populations by permanently growing local populations constitutes a major risk of regression and disappearance of species (Kouakou et al, 2016, Aholoukpe, 2017.…”