Effects of UV-treated sea water, chlorinated sea water, and formalin-treated copepods on survival and growth of newborn seahorses, Hippocampus comes

Abstract

Seed production of the seahorse Hippocampus comes was examined using different types of sea water (UV-treated, chlorinated, sand-filtered), and formalin-treated copepod Pseudodiaptomous sp. as a food organism. Growth and survival of newborn seahorses (8.9±0.0 mm stretched height, 0.004 g) were monitored until day 30 after birth. Growth (stretched height and weight) was significantly higher (p<0.05) in UV-treated sea water (41.4±0.5 mm, 0.23±0.00 g) than in chlorinated (33.8±1.4 mm, 0.16±0.00 g) or sand-filtered (32.8±0.1 mm, 0.16±0.00 g) sea water. Survival was significantly higher in UV-treated (65.6±1.1%) and chlorinated (62.2±4.0%) sea water than in sand-filtered sea water (41.1±1.1%). Survival of seahorses fed 30 ppm formalin-treated copepods (95.3±1.8%) was significantly higher (p<0.05) than of seahorses fed untreated copepods (78.7±5.5%) on day 8. On day 15 survival was 78.7±9.68% in seahorses fed formalin-treated copepods and 0% in those fed untreated copepods. By day 30, survival of seahorses fed formalin-treated copepods was 64.7±9.82%. On the day of the final comparison (day 10), there was no difference in size between groups. Thus, the present study demonstrates that survival and growth of newborn seahorses is significantly improved in UV-treated water, and survival is markedly maintained by treating food organisms in formalin.