Asian-Pacific Aquaculture 2024

July 2 - 5, 2024

Surabaya, Indonesia

UTILIZATION OF MACROALGAL JUICE AS AN ALTERNATIVE SETTLEMENT CUE AND POST-SETTLED JUVENILE FEED FOR Stichopus cf. horrens

Glaiza Ibañez1*, Rona Soy1, Marie Antonnette Juinio-Meñez1

1Marine Science Institute, University of the Philippines Diliman, Quezon City, Philippines 1101

*gsibanez@up.edu.ph

 



 The aquaculture of economically important sea cucumber species  is one way of mitigating overexploitation by  decreasing dependence on wild catch.  For Stichopus cf. horrens , an emergent aquaculture species harvested for consumption and as source of raw materials in the nutraceutical and pharmaceutical industries, production bottlenecks exist in the hatchery culture phase during settlement and metamorphosis to early juveniles.  Primarily,  cultured  live microalgae (i.e., Chaetoceros muelleri / calcitrans and Navicula ramosissima ) are used as settlement cue and early juvenile feed post-settlement. However, these are costly in terms of maintenance. Preliminary trials have shown the potential of using macroalgal juice as  a cheaper and more sustainable  alternative to live microalgae. In this study, the effectiveness of three macroalgal juices ,  Sargassum  sp. (SRJ), Gracilaria  sp. (GRJ), and  Ulva sp. (ULJ), to induce settlement and increase the size of post-settled  S.  cf. horrens juveniles were tested against  N. ramosissima  (NR) as positive control.  In the settlement experiment,  concentrated macroalgal juices were painted on  corrugated plastic sheets which served as settlement plates. These were placed in  70-L  bins stocked with late auricularia larvae at a density of 0.3 larvae ml-1 .  In the feeding experiment, post-settled juveniles (~4-10 mm) were fed with  SRJ, GRJ, ULJ, and NR. After 30 days of rearing, highest settlement success was recorded in the ULJ (1.58 ± 2.89 %) treatment but was not significantly different than the other treatments. Moreover, sizes of post-settled juveniles were highest in the NR (7.3 ± 3.8 mm) treatment followed by ULJ (7.1 ± 2.7 mm) and these are significantly higher than the GRJ (6.1 ± 2.3 mm) treatment. In the feeding experiment, no significant differences were noted among treatments however, the highest average length was recorded in the ULJ (11.4 ± 2.0 mm) treatment on Day 15. Interestingly, a slight increase in the juvenile length was noted on Day 15 but all lengths decreased on Day 30. Furthermore, survival was significantly lower in the SRJ (46.7 ± 26.9 %) treatment.  The comparable settlement success, average lengths, and survival among the four treatments suggest the potential of using macroalgal juice as an alternative to the conventional live microalgae as settlement cue and post-settled juvenile feed prior to release in the ocean nursery .  Optimizing the use of juice in terms of feeding concentration/ amount and understanding  the nutritional requirements of metamorphosing larvae and post-settled juveniles are pivotal considerations in the development of cost-effective and sustainable macroalgal feeds.