Polyculture potential of endemic Benni (Mesopotamichthys sharpeyi) with three species of non-endemic tilapia, Zilli (Captodon zilli), Blue (Oreochromis aureus), and Nile (Oreochromis niloticus) based on various weight ratios and stocking densities

Abstract

This study aimed to investigate Benni's weight ratios or stocking densities in two distinct experiments in the presence of three species of tilapia: Zilli, Blue, and Nile in 60 days. The fish were divided into four experimental groups with 22 treatments in triplicate. The groups were based on different weight ratios (10% or 30% difference) and stocking densities (2:1, 1:2, and 1:5). This included four control treatments, six Benni-Zilli treatments, six Benni-Blue treatments, and six Benni-Nile treatments. Benni, Zili, Blue, and Nile had initial weight ranges of 5.1–9.3, 4.0–7.2, 5.1–9.2, and 5.1–7.7 g, respectively. Benni's growth performance compared to Zilli had a direct relationship with Benni's weight gain. A reverse correlation was revealed with Benni's weight gain in the analysis of Zilli's growth performances. Benni and Zilli showed similar growth performances during the stocking density experiment. Treatments with higher weight and stocking density ratios of Benni showed an improved survival rate. The highest survival rate for Zilli was observed in Benni's lower weight and stocking density ratios. Various weight ratios and stocking density had no significant effect on Benni's growth compared to Blue. The growth performance of Blue in Beni-Blue experimental treatments was better than that of Benni. In all six Benni-Blue treatments, the average survival rate of Benni was 97.76%, while Blue was 94.41%. The experimental treatments with Benni-Nile showed no adverse effect of increasing the stocking density ratio of Benni on Nile growth performance. The Benni population increased, and Nile growth indicators improved. These results suggest that the Nile exhibits high competition ability against Benni. It is noticeable that the Benni did not achieve a 100% survival rate in any Benni-Nile treatment, while the Nile had a 100% survival rate in the four experimental treatments. According to the results, the presence of Nile, Zilli, and Blue had the most negative impacts on the growth indices of Benni, respectively. Moreover, Benni showed the highest average survival rate in polyculture with Blue, Zilli, and Nile, respectively. Benni cannot compete interspecies with tilapia by species-based mechanisms. Benni in polyculture with Nile tilapia is not advised under the experimental conditions. The negative impacts of Zilli's presence next to Benni may be reduced by increasing the weight ratio or stocking density. Blue demonstrated the least negative impact on the examined Benni performances compared to the other two experimental tilapia. It is recommended that every effort be made to prevent the introduction of any tilapia species into Benni's ecosystem.