Yellow perch (Perca flavescens) larval production is often hindered due to slow growth, low survival rate, and non-inflation of the swim bladder. Traditional recirculating aquaculture systems are often costly and technically demanding, which discourages adoption by small- and medium-scale producers. To address this, a novel, low-cost (<$100) filter and sprayer recirculation system (FSRS) was developed that can be added to existing tanks. The FSRS recirculates water through a filter with a surface sprayer within the tank to improve the rearing environment. This study evaluated the FSRS on larval growth, survival, and swim bladder inflation (SBI) with two feeding regimes (rotifer, artemia) and stocking densities. Salinity effects on rotifers growth were also measured in this study.
Rotifers were grown at a salinity of 10 and 20 ppt to optimize their production. Yellow perch larvae were reared in the lab and on two farms using the FSRS, under two feeding regimes (rotifers only vs. rotifers followed by artemia) and two stocking densities (~21 vs. ~44 larvae/L) for 38 days. The larvae were fed only rotifers for 17 days, or rotifers for 10 days followed by artemia for 7 days, then both live feed and dry feed (Otohime B1) for 14 days, and then only dry feed for 7 days. At the farms, larvae were reared on a single feeding regime (rotifer followed by artemia). The SBI rate was measured after 31 days of feeding (dof). Growth and survival rate were measured at multiple points (10, 17, 31, and 38 dof).
Growth in 20 ppt salinity yielded significantly more rotifers than 10 ppt (p < 0.0022). Larvae fed rotifers followed by artemia exhibited significantly greater growth than those fed only rotifers (p < 0.001). In the lab, larvae reared at lower densities achieved greater growth than at higher densities, regardless of the feeding regime, confirming that reduced density supported faster growth. However, as farms did not include directly comparable densities, farms were compared in terms of feeding (rotifers followed by artemia) and found that growth was even better than in the lab. Rotifers found to be more effective in survival compared to rotifer followed by artemia feeding. In the lab, the survival rate was ~65% under low-density conditions compared with ~46% at high density. For Farm A and Farm B, the survival rate was ~ 4% and ~ 30%, respectively. SBI rate in all experimental sites were not diet and density (p > 0.05). In the lab, the SBI rate was ~ 55% and ~46% for high and low densities, respectively, and ~50% at Farm A and ~6% at Farm B. Farm B faced higher algal turbidity issues, which may have hindered the SBI.
This study demonstrates that the FSRS technology could enhance larval yellow perch rearing by supporting high growth, SBI, and survival rate. Feeding rotifers followed by artemia significantly enhanced growth. The reduced density also enhanced growth. Farms achieved equal or greater growth than the lab, but with lower survival rates, underscoring the operational challenges associated with large-scale production. Overall, this low-cost FSRS and combined feeding regime of live feeds can markedly improve yellow perch larval production.
Keywords: yellow perch, recirculation system, rotifers, artemia, swim bladder inflation, survival.