Influence of precipitation and water-level on the reproduction of Ctenopoma petherici Günther, 1861

Abstract

The present study aims to understand the importance of rainfall and water level in the reproduction of Ctenopoma petherici in tropical environments. The experiment consisted of following females for 12 months in two different ecosystems: Lake Ayame 2 and the Agneby river. In Lake Ayame 2, the water is permanent, while in the Agneby river, the water level varies considerably from the dry season to the rainy season. Fish were collected monthly from September 2015 to August 2016. Gonado-somatic index, percentage of mature females and percentage of sexual stage of gonad maturation were calculated m onthly. Stages of sexual maturity were determined. The effect of rainfall and high water levels on maturity was highlighted by considering the period from March to April and the long dry season. To determine the reproductive strategy of C. petherici, the distribution of oocytes at different developmental stages was examined at different times of the ovarian cycle. Two variants of the Chi-square test and the Mann-Whitney test were used. The results indicate that rainfall and water level influence the maturity status. Each of them stimulates and promotes the maturation of the gonads and their combination leads to the intensification of sexual activity. As a result, C. petherici breeds all year round in Lake Ayame 2. In the Agneby river, breeding begins at the end of the long dry season and intensifies with rains and floods. The breeding period coincides well with the long rainy season on the Agneby river. At the end of this work, it appears that rainfall and high water levels in the environment have the same effect on the reproduction of C. petherici. The distribution of oocytes at different stages of maturity indicates a unique egg-laying pattern for this species.