Evaluation of the Cyclopoid Copepod Apocyclops royi as Live Feed for Larval Rearing of Pearlspot (Etroplus suratensis)

Abstract

Aim: To evaluate the efficacy of the cyclopoid copepod Apocyclops royi as a live feed for larval rearing of pearlspot (Etroplus suratensis) and to assess its suitability for hatchery-scale seed production by comparing its performance with that of Artemia franciscana nauplii and a combined feeding strategy. Study Design: A 21-day experiment was conducted using 3-day-post-hatch (DPH) Etroplus suratensis larvae under three dietary treatments, each with three replicates. Larvae were reared in 100-L cylindrical polyester fibreglass tanks to evaluate survival, growth performance, and morphometric development. Methodology: Pearlspot larvae were randomly assigned to three dietary treatments: (i) Apocyclops royi,    (ii) Artemia franciscana nauplii, and (iii) a combination of A. royi and A. franciscana nauplii (1:1). Each treatment consisted of three replicate tanks stocked with 250 larvae per tank. Survival, body weight, total length, specific growth rate (SGR), and morphometric development were evaluated. Data were analysed using one-way analysis of variance (ANOVA), followed by Tukey's HSD post hoc test, and significant differences among treatments were determined at p < 0.05. Results: Significant dietary effects on larval performance were observed from 9 DPH onwards (p < 0.05). Larvae fed the combined diet exhibited the highest final weight (30.53 ± 0.64 mg), final length (12.51 ± 0.18 mm), specific growth rate (10.30 ± 0.14% day⁻¹), and survival (90.26 ± 1.67%), which were significantly greater than those of larvae fed A. royi alone (25.52 ± 0.58 mg; 11.53 ± 0.19 mm; 9.45 ± 0.11% day⁻¹; 80.66 ± 2.12%) or A. franciscana nauplii alone (23.03 ± 0.62 mg; 10.82 ± 0.22 mm; 8.96 ± 0.10% day⁻¹; 71.00 ± 2.61%) (one-way ANOVA, Tukey's HSD, p < 0.05). The combined diet also promoted greater body elongation, pigmentation, fin development, and overall morphometric differentiation. Conclusion: Under the tested conditions, the combined diet of A. royi and A. franciscana nauplii was associated with improved survival, growth performance, and morphological development of E. suratensis larvae compared with either live feed provided individually. The findings indicate that including A. royi in larval feeding regimes may support pearlspot seed production and warrants further evaluation under hatchery conditions.