A study on the feeding of the pot-bellied seahorse (Hippocampus abdominalis : reducing the reliance on brine shrimp (Artemia)
Creators: name: Wardley, TR
Publisher: name: University Of Tasmania
Year: 2023

description: The primary aim of this study is to reduce the reliance on Artemia during the culture of pot-bellied seahorses. The results demonstrate that reliance can be reduced significantly if not totally replaced. Early juvenile seahorses can be fed on alternative live diets such as copepods as the growth (F = 0.054, df 1, p &gt; 0.05) and condition (F = 0.416, df 1, p &gt; 0.05) of 3-week old seahorses fed copepods was similar to those fed enriched Artemia. It was also found that seahorses as young as newborns readily consumed copepods and gammarid amphipods (Hippomedon sp and Biribus sp) from the biofouling panels. Later juveniles can continue to be fed on biofouling crustaceans as the growth (F = 0.982, df 1, p &gt; 0.05) and condition (F = 7.401, df 1, p &lt; 0.05) of 17-week old seahorses fed biofouling was similar to those fed Artemia or weaned onto frozen diets. The best predictor for determining prey size was the total length of the seahorse. Based on Cheeson's standardised forage ratio the preferred prey type of 5, 21 and 49 day old seahorses showed a particular preference for copepods with 21 and 49 day old seahorses also positively selecting both amphipod species (Hippomedon sp and Biribus sp). Larger 147 and 175-day old seahorses positively selected both amphipod species and 203-day old seahorses' positively selected Biribus sp and caprellids (Caprella sp). Thirteen week old seahorses were weaned onto either a frozen mysid or amphipod diet with a nil, 10 day and 16 day weaning period and it was found that the growth of seahorses weaned onto frozen diets over a 16 day period had similar growth (F = 83.922, df 7, p &lt; 0.05) to those seahorses fed enriched Artemia. It is possible that younger seahorses could be weaned onto frozen diets if appropriate sized feeds can be attained. It was also found that although a range of commercial enrichment diets had no affect on the growth (F = 0.671, df 5, p &gt; 0.05) and condition (F = 1.637, df 5, p &gt; 0.05) of seahorses, Artemia should be enriched as the liver condition in seahorses fed unenriched Artemia was poor and the optimal feed rate for seahorses was between 5 and 7 % body weight daf1 (F = 0.47, df 5, p &lt; 0.05). This study also examined the anatomy of the digestive system and ontogenetic development of digestive enzymes to provide a better understanding of the potbellied seahorses' nutritional requirements and digestive capacity. Seahorses are released with a near fully developed digestive tract and could be said to be fully developed between day 21 and 35 after the intestinal valve develops on day 7 and the intestine starts to loop around itself on day 21. Trypsin, lipase and amylase were present at every stage studied. The presence of enzymes in unfed newborn seahorses indicates that they are capable of digesting protein, lipid and carbohydrates prior to the onset of feeding, however the digestive system may not be fully functional until around day 28 to 35 when enzyme activities appeared to plateau. It was also found that trypsin and lipase activities were greater than amylase activities indicating that seahorses rely more heavily on protein and lipid than carbohydrate for their early nutrition. Lastly a cost benefit analysis of alternative feed sources was prepared which demonstrated that significant savings in costs can be achieved.