Optimal dietary ration for juvenile pigfish, Orthopristis chrysoptera, grow-out

• Marine baitfish aquaculture increases availability of live bait.
• Marine baitfish aquaculture protects natural population of baitfish species.
• An optimal ration model minimizes waste while maximizing growth rate.
• At optimal ration, pigfish could be grown from hatching to market size in 2–3 months.

Pigfish (Orthopristis chrysoptera) have been identified as a good candidate for marine baitfish aquaculture. Initial research on the species has focused on captive spawning and larval rearing, but optimizing juvenile grow-out is also essential for economical production. We conducted an experiment to determine the optimal ration (Ropt) for maximizing growth rate while minimizing size variability and overfeeding. We measured total length (TL), wet weight (WW), specific growth rate (SGR), gross feed conversion efficiency (GFCE), and survival of juvenile pigfish (initial size: 2.6 ± 0.4 cm TL) using six ration levels (4, 8, 12, 16, 20, or 24% WW d− 1) for four weeks at 24.7 ± 0.2 °C. Final size (TL and WW) increased with increasing ration at lower rations, reaching a plateau at intermediate levels (8–16% WW d− 1). Survival increased with ration from 74% at the lowest ration to a plateau of 96.0% at rations > 10.7% WW d− 1. GFCE decreased with increasing ration from 149% to 47%. To identify Ropt and its change with fish size, we modeled SGR as a function of WW, ration, and their interaction and found that Ropt = 11.19 · WW− 0.26 (R2 = 0.70, P < 0.05). This equation provides a guide for producing pigfish quickly and efficiently and, with further research on culture requirements, can be used to establish an efficient pigfish grow-out protocol.