Ingestion rate, survival and growth of newly released seahorse Hippocampus reidi fed exclusively on cultured live food items

Abstract

The main bottleneck for seahorse aquaculture is the low survival of newly released juveniles. Although the reasons for low survival are poorly understood, proper nutrition is considered crucial. This study therefore evaluated the ingestion rate (IR), survival and growth of newly released Hippocampus reidi reared under different management protocols. The indirect method was used to estimate the IR of different live food items (newly hatched Artemia nauplii, rotifers Brachionus plicatilis and the offspring of the copepod Tisbe biminiensis). A 14day-long rearing trial was conducted on 38L aquaria connected to a seawater recirculation system. Six treatments were tested: Art00h — newly hatched Artemia nauplii (5ind.mL−1); Art24h — 24-h enriched Artemia (5ind.mL−1); Rot+Art24h — rotifers (B. plicatilis; 10ind.mL−1) from day 1 until day 7 followed by enriched Artemia metanauplii (5ind.mL−1); Cop — Copepods (T. biminiensis; 2ind.mL−1); and Art24h+Cop — T. biminiensis (2ind.mL−1) and 24-h enriched Artemia (5ind.mL−1). In the treatment Starvation, no feed was provided. All treatments, except Starvation, received the microalgae Nannochloropsis oculata every other day. The IR trials indicated that the offspring of the copepod was the main live food ingested by the seahorses. Treatment Art24h+Cop resulted in a significantly higher survival (33.5±5.4%), followed by Cop (6.6±4.8%) and Art00h (6.0±8.3%) which were not significantly different from each other, but significantly higher than juveniles fed rotifers and Artemia (Rot+Art24h) with a survival of only 0.3% (±0.5). No survivors were observed in the remaining treatments. Growth parameters were significantly higher in Art24h+Cop and Art00h. Results showed that the feeding of copepods T. biminiensis combined with enriched Artemia increases growth and survival of H. reidi during the first two weeks of life.