Growth, Survival, and Behavior of Early Juvenile Sandfish Holothuria scabra (Jaeger, 1883) in Response to Feed Types and Salinity Levels under Laboratory Conditions

Abstract

Aquaculture of the tropical sea cucumber Holothuria scabra or sandfish is still at a developing stage, especially in the Philippines. In Mindanao, early juveniles of sandfish were successfully produced at the Mindanao State University at Naawan (MSUN) sandfish hatchery for 5 yr now. However, on-site growing of these early juveniles in ocean nurseries often suffered very low survival rates. Two separate laboratory experiments were conducted for 60 d to test for the effects of feed types (Navicula sp., powdered Sargassum, and Sargassum extract) and salinity levels [ambient seawater at 32–35 (as control), 20, 25, and 40 ppt] on the growth, survival, and behavior of 7-wk-old early juvenile sandfish (2–15 mm in length). Juveniles fed with Sargassum extract significantly produced the highest increase in width and length, followed by powdered Sargassum and Navicula sp. with a survival rate of at least 71%. The highest growth rate (GR) and survival were observed with ambient salinity, followed by 40, 25, and 20 ppt. Unusual pale coloration, sluggish movement, and destroyed integument in some parts of the body were observed in some juveniles exposed to lower salinity indication of an unhealthy individual. Overall, Sargassum extract is an ideal feed for sea cucumber juveniles. Low salinity is stressful to early juvenile sandfish and that growth and behavior were adversely affected.

Application of Sargassum sp extract on juvenile sandfish nursery

“…Absolute growth in body length of juveniles reared in a controlled tank for 30 days of 20.1 mm [3]. Referring to the results shown [3,5], the absolute growth of the body length of the three treatments (8.76 -14.59 mm) was still quite good. Good growth because of the available food and stocking density which was still in the optimal range (400 individuals/m 2 ).…”

“…A report mentioned that the body length of juvenile sandfish measuring 2-15 mm that were fed Sargassum sp extract and reared for 60 days was 20-34 mm [5]. Absolute growth in body length of juveniles reared in a controlled tank for 30 days of 20.1 mm [3].…”

“…In the Philippines, the development of sandfish seeds production techniques, especially the maintenance of juvenile sandfish H. scabra was carried out using Sargassum sp seaweed as juveniles feed IOP Publishing doi:10.1088/1755-1315/1207/1/012007 2 [4,5]. Sargassum sp is available and grows in the coastal of the Kei Islands.…”

Can commercially available mosquito nets be used for rearing sandfish (Holothuria scabra) juveniles in floating ocean nursery?

“…Factors that may have affected the growth performance of juveniles might be related to environmental parameters in each site. According to Magcanta et al (2021), water salinity affects the growth of sandfish juvenile. High precipitation brought by heavy rains and typhoon Surigae during the first 30 d of rearing could have lowered the water salinity at Site 2 which has restricted water movement.…”

“…Such condition allows faster biofilm accumulation and subsequent fouling particularly as CH has very fine mesh. Other factors such as handling, predation (Cabacaba and Campo 2019; Altamirano and Noran-Baylon 2020), and salinity fluctuations (Magcanta et al 2021) during heavy rains also affect growth and survival of sandfish juveniles.…”