Abstract
Knowledge of the biology and ecology of seahorses ( Hippocampus spp.) is scarce, but has been increasing in recent years due to their conservation status. Captivity breeding programmes can be a valuable source of information on the reproductive biology of seahorses. A captive broodstock of Hippocampus guttulatus Cuvier 1829 was established in 2006 and kept under natural-like photoperiod and temperature. Female maturation was studied during the whole reproductive season in 2007. Most egg clutches were released from May (17 °C; 15L:9D) to October (18 °C; 13L:11D), with peak releases occurring in June–August (20 °C; 16L:8D–14L:10D). Throughout the study, four egg morphotypes were found; two regression equations were proposed for estimating egg/yolk volume based on measurements of egg and yolk biometrics. Female weight was positively correlated with yolk volume/egg volume ratio ( Y v/ E v) ( r s = 0.523, n = 21, P < 0.05) but not with E v or Y v. Egg dry weight (567 ± 141 μg) was correlated with Y v ( r s = 0.384, n = 31, P < 0.05). Mean clutch size and clutch biomass were 242 ± 142 eggs and 137 ± 87 mg dry weight, respectively. Clutch size was positively correlated to female weight ( r s = 0.479, n = 25, P < 0.05). Inter-clutch intervals (days) were affected by temperature (°C) as described by the following equation: Interval = 357.55e −0.1283 Temp. Estimated inter-clutch intervals at 16, 18 and 20 °C were 45.9, 35.5 and 27.5 days, respectively. Egg total lipids accounted for 31.9 ± 3.1% dry weight. Absolute lipid content in eggs was correlated with egg dry weight ( r s = 0.907, n = 41, P < 0.001) and Y v ( r s = 0.384, n = 41, P < 0.5). In decreasing order of relative percentage, the most important fatty acids, were 18:1 n9, 16:0, 18:2 n6, 20:5 n3, 18:0 and 22:6 n-3. The level of n-3 HUFA was 18.5 ± 0.7% (38.4 ± 3.3 mg/g dry weight). The profile of fatty acids in eggs resembled that displayed by the broodstock diet (enriched adult Artemia).
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