Impact of Diverse Fertilization Practices and Supplementary Feeding Regimes on Water Quality, Plankton Abundance, Growth, Survival, Blood Parameters, and Economic Returns of Grey Mullet (Mugil cephalus) in Nursery Ponds

Abstract

The grey mullet (Mugil cephalus) is a significant aquaculture species known for its rapid growth, versatility, and high market demand. However, nursery-stage mortality, slow development, and high production costs continue to limit its profitability, particularly in earthen pond systems. One of the most significant issues is a lack of standardized and cost-effective feeding and fertilization systems that may optimize natural food production, maintain appropriate water quality, and improve fry survival and growth. The current study examines how various fertilizers and feeding techniques affect the water quality, plankton quantity, growth performance, survival rate, certain blood parameters, and economic assessment of raising grey mullet (Mugil cephalus) fries in eastern ponds. For seven months, grey mullet fries weighing 0.35±0.02 g were planted in nine earthen ponds (1000 m2 each) at a pace of 50,000 seeds. Three treatments were studied in triplicate: organic fertilizer with aquafood (T1), inorganic fertilizer with aquafood (T2), and aquafood only (T3). The measured water parameters were determined to be within an optimal range during the study period, with significant (P<0.05) changes in pH and ammonia concentrations across treatments. When comparing T1 to the other treatments, phytoplankton and zooplankton numbers showed considerably (P<0.05) higher values. The findings also show that compared to other groups, T1 showed a highly significant (P<0.05) increase in final body weight, weight gain, daily gain weight rate, and specific growth rate. T1 had the highest survival rate (60%), followed by T2 (57%) and T3 (55%). Basic hematological measures such as hemoglobin concentration (Hb), red blood cell count (RBCs), and hematocrit (Ht) showed substantial (P<0.05) changes. Furthermore, T1 achieved the highest benefit-cost ratio of 1.42, while T2 and T3 achieved 1.32 and 1.26, respectively. This approach came to the conclusion that the optimal nursery pond management for improving grey mullet survival and growth as well as raising the financial returns was to use organic fertilizers with aquafeed as a feeding strategy.