Olivia I. Markham

Marine copepods are an essential live feed for the culture of many marine ornamental fish and other finfish species, yet their production is frequently constrained by contamination from free-living ciliates. To address this challenge, the efficacy of three disinfectants (sodium hypochlorite, iodine, and hydrogen peroxide) was evaluated for ciliate removal in cultures of two copepod species, Parvocalanus crassirostris and Oithona colcarva. Appropriate ranges of disinfectant concentrations and exposure durations were identified through a preliminary trial assessing the toxicity to Euplotes spp. over a 5-min period. Subsequent experiments tested three doses of each disinfectant to quantify ciliate removal success and egg hatch rates for each copepod species. Ciliate presence/absence showed no variation (100% in controls, 0% after disinfection), precluding statistical analysis except for one variable iodine trial, which was analyzed using Fisher’s Exact Test. Hatch and recovery rates were analyzed using binomial GLMMs with treatment as a fixed effect and replicate as a random effect, with Tukey-adjusted pairwise comparisons and α = 0.05. Sodium hypochlorite and hydrogen peroxide consistently removed all ciliates across tested concentrations, whereas iodine only achieved complete removal at the highest dose. The effects on hatch rate differed between species, with hydrogen peroxide producing the highest hatch rates in P. crassirostris (approximately 44 to 46% at 50–100 g/L for one minute) and sodium hypochlorite supporting the highest hatch in O. colcarva (up to 92% at 250 mg/L for one minute). These findings demonstrate that disinfectant performance is species-specific and that species-specific disinfection protocols are warranted to improve the reliability of copepod production in marine aquaculture.

The cherry barb (Puntius titteya) is a staple of the ornamental aquaculture industry, with an estimated 60,000 individuals produced monthly in Florida, USA. On a commercial scale, small improvements in efficiency may yield considerable economic and operational benefits. This study investigated first-feeding protocols aimed at reducing the use of live Artemia spp. nauplii by evaluating microdiets (MDs) top-dressed with feed attractants and commercial liquid Artemia replacements (LAs). Larvae were fed MDs top-dressed with 0.25%, 0.50%, or 1.0% of L-alanine, betaine, or L-tryptophan for seven days. Diets with L-alanine and L-tryptophan significantly increased survival compared to the reference diet. A 21-day trial that tested three feed attractants combined into a single diet at previously determined inclusion levels (L-alanine, 0.5%; betaine, 0.25%; and L-tryptophan, 0.25%) showed no additive or synergistic survival benefits. No differences were observed for RNA/DNA ratios at 15 days post-hatch, suggesting no effect on larval quality. Additional experiments were conducted comparing the performance of two commercial LA diets (EZ Artemia Ultra [Zeigler Bros., Inc., Gardners, PA, USA] and LiquaLife^® [Cargill Inc., Minneapolis, MN, USA]) against live Artemia. Partial Artemia replacement with EZ Artemia Ultra maintained comparable survival to larvae fed only Artemia. Larval growth was significantly reduced in 100% LA groups, suggesting limitations in nutrition or digestibility. These findings demonstrate that targeted use of feed attractants can enhance early rearing outcomes in P. titteya aquaculture, facilitating the goal of reducing Artemia use and increasing production efficiency and hatchery output.

Clownfish (Amphiprion ocellaris) are a staple commodity in the marine aquarium trade and an emerging model organism for research. Bottlenecks during larviculture affect the survival of juvenile fish and continued reliance on live feeds, such as rotifers (Brachionus spp.) and Artemia spp. nauplii, increasing the complexity and cost of raising this species. This study utilized known digestive physiology of clownfish larvae to experimentally reduce the use of live feeds. First, larvae were weaned from rotifers to Artemia at three time points (3, 5, and 7 days post-hatch [DPH]), demonstrating that larvae can be transitioned to Artemia as early as 5 DPH without negative impacts on survival, total length (TL), or whole-body cortisol. A second weaning trial tested the introduction of a commercial microdiet (MD) at 5, 8, and 11 DPH. Survival was greatest when the MD was introduced at 5 DPH (mean ± SD; 64.47 ± 0.10%), and no differences in TL nor whole-body cortisol were detected, suggesting that Artemia may not be required prior to MD weaning. Next, three commercially available MDs were tested for their effects on survival, growth, and coloration of clownfish larvae. Survival and growth did not differ among diets, but fish fed TDO Chroma Boost™ exhibited significantly red-shifted hues, higher saturation, and greater brightness scores in some body regions compared to fish fed Golden Pearl or GEMMA Micro 300. A partial budget analysis indicated a net profit increase of ~$1.60 per fish, highlighting the potential for cost savings and streamlined clownfish production.