The effects of temperature, Artemia enrichment, stocking density and light on the growth of juvenile seahorses, Hippocampus whitei (Bleeker, 1855), from Australia

The effects of environmental parameters (temperature, feed, stocking density and light levels) on juvenile growth of White's seahorse, Hippocampus whitei, were examined over 107 days. Growth rates in animals stocked at about 3 months old increased with increasing temperature from 0.14 mm day(-1) at 17 degreesC to 0.26 mm day(-1) at 26 degreesC. Several body condition indices fell with increasing temperature, possibly as a result of increased metabolic rates at higher temperatures. The hepatosomatic index (HSI) fell from 4.44 at 17 degreesC to 2.67 at 26 degreesC. The gonadosomatic index (GSI) peaked at 20 degreesC, indicating that the optimal temperature for reproduction was 20 degreesC. The seahorses became mature at 6-7 months old. The use of Artemia enriched with DC Selco(R) improved growth rates over non-enriched Artemia, but did not affect the condition indices. There were no major effects of stocking densities (range 0.5-1 seahorse l(-1)) and light levels (range 24-136 muE m(-2) s(-1)) on growth over the limited range tested, but there was an indication that reproduction might be inhibited at stocking densities greater than 1 seahorse l(-1). (C) 2003 Elsevier Science B.V. All rights reserved.