Anthropogenic Impacts on Fish Populations in Lake Cayo (Republic of Congo, Central Africa)

Abstract

Ichthyofaunal diversity and the impact of anthropogenic activities on fish population assemblages were studied in Lake Cayo, a small lake located in the coastal region of the Republic of Congo. Twelve stations were sampled twice over a two-year period. Fishing techniques following standardized methods utilizing monofilament gill nets, and nine environment variables were measured at each station. A total of 11,361 specimens comprising 30 species in 28 genera and 18 families were collected with the Cichlidae being the most diversified. Redundancy Analysis with forward selection coupled with Monte Carlo permutation tests identified depth, pH and substrate as accounting for 57.7% of the total variance among the nine variables sampled (p < 0.05). The low Shannon's diversity (1.16 ± 0.33) and Equitability (0.43 ± 0.12) indices at all sites, suggest that the Lake Cayo system is in poor ecological health.

Diversity and Influence of Environmental Factors on the Spatio-Temporal Distribution of the Ichthyofauna of Malonda Lagoon (Congo Brazzaville)

“…Malonda lagoon is located in an oil zone. Oil exploitation is one of the main activities identified as polluting the aquatic systems of the southwest coast of the equatorial ecoregion [12].…”

“…The high values of the indices (H' and R) would show an even distribution and a good diversification of species within a station [17]. When the calculated H' and R indices approach their maximum values, this proves that all species in the community constitute an excellent distribution of abundance and that the environment is in good ecological health [12] [24]. In our case for most stations, the values show a poor distribution of fish abundance, consequently a poor ecological state of the lagoon.…”

“…The composition of settlements is also modified, sometimes considerably, by human interventions, such as the construction of works (port facilities, dykes, dams), the development of communications with the ocean, fishing and aquaculture activities, pollution linked to urbanization and industrialization and agricultural activities [11] [12]. These activities can have significant and uncontrolled consequences on the entire lagoon hydrosystem from the catchment area to the sea [13].…”

Length-Weight Relationships and Condition Factors of 15 Fish Species from the Lo&#233;m&#233; River Basin (Mayombe, Republic of Congo)

“…Work carried out in the Loémé basin [4] [14] only reports a systematic assessment of its ichthyofauna, as is the case for the majority of the fresh and brackish waters of the Republic of Congo. The other aspects such as biology and ecology are not or only very slightly addressed in this basin [15] [16].…”