Growth, mortality and yield of Sarotherodon melanotheron melanotheron (Rüppell, 1852) in the Lake Nokoué and Porto-Novo Lagoon complex Benin, West Africa

Abstract

The study evaluated some population parameters of Sarotherodon melanotheron melanotheron within a lagoon complex in southern Benin: Lake Nokoué and Porto-Novo Lagoon. Data on the total length, total weight, and sex were recorded monthly between January and December 2015 for 1,745 specimens captured by local fishermen. The asymptotic length L∞ was estimated at 24.68 cm. The growth rate K was 0.86. The total, natural, and fishing mortalities were estimated at 2.46, 1.71, and 0.75 y−1, respectively. The size at first sexual maturity was 8.9 and 9.2 cm, respectively, for males andfemales. The size at first capture was estimated at 9.2 cm, which indicates that fish spawn at least once before capture. The current exploitation rate of 0.31 remains below the maximum exploitation rate Emax which was 0.604 but was equal to the exploitation rate retaining 50% of the biomass of the stock (E0.5 = 0.324). This suggests that the stock of S. m. melanotheron is not overexploited in the complex. However, it is recommended that the actual rate of exploitation be kept as it is to ensure a sustainable management of these fish populations.

Evaluation of length-weight and length-length relationships of some of the most abundant commercial fishes from the Couffo River basin (Benin, West Africa)

“…Differences in growth patterns have been reported previously for the same species in the same environment and in different ecosystems. These differences could be related to sample size, season, fishing habitat, sex, maturity stage, diet and stomach fullness, health status, trophic level, and food availability (Bagenal and Tesch 1978, Lowe-McConnell 1987, Oribhabor et al 2009, Koffi et al 2014. None of these parameters were considered in this study like the one that was conducted in the Mono basin (Lederoun et al 2016b).…”

“…Beninese continental waters abound with diverse aquatic fauna (LalPyP et al 2003, 2004, Moritz et al 2006, Montchowui et al 2007, Moritz 2010, Ahouansou Montcho 2011, Lederoun 2015, Lederoun et al 2018a, 2018b, Moritz and LalPyP 2019 and free access year round (Lederoun et al 2016a(Lederoun et al , 2020. This explains the overexploitation of the resources (Niyonkuru 2007, 2016a and the need to identify sustainable management measures to avoid the depletion of stocks that are still available.…”

Spatial and temporal patterns of fish assemblages in Lake Nokoué and the Porto-Novo Lagoon (Benin, West Africa)

“…This system alone contributes between 65 and 70% to the country's continental water fisheries production. However, the increase in commercial fishing since the 1990s has led to a gradual decline in fish populations from overfishing (Lederoun et al 2020). While studies focusing on population dynamics and sustainable management practices have been conducted for certain target species (Coptodon guineensis (Günther), Hemichromis fasciatus Peters, Sarotherodon melanotheron (Rüppell) (Niyonkuru 2007, Lederoun et al 2020, comprehensive research on the fish ecology within this complex remains scarce.…”

“…However, the increase in commercial fishing since the 1990s has led to a gradual decline in fish populations from overfishing (Lederoun et al 2020). While studies focusing on population dynamics and sustainable management practices have been conducted for certain target species (Coptodon guineensis (Günther), Hemichromis fasciatus Peters, Sarotherodon melanotheron (Rüppell) (Niyonkuru 2007, Lederoun et al 2020, comprehensive research on the fish ecology within this complex remains scarce. Previous studies on the spatio-temporal variations of the ichthyofauna are outdated, with the most recent data dating back over two decades (Adité and Thielen 1995, LalPyP et al 2003, 2004, Villanueva 2004.…”

Untitled

“…Trewavas [4] had subdivided S. melanotheron into five subspecies. Currently, three subspecies of this fish are clearly distinguished as separate taxa through morphometric and molecular data [5] among which, we can cite S. m. melanotheron known from Côte d'Ivoire to Cameroon [6] . This fish is found in estuaries and brackish waters in Côte d'Ivoire from the Cavally River in the West to Aby lagoon in the East and also in various ecosystems of the Bia basin [7].…”