MARINE AND FISHERY SCIENCES 36 (2): 209-217 (2023)
ABSTRACT. This study investigates the potential of locally available mosquito nets as an alter-
native material for sandfish ocean nurseries. Mosquito nets (~2 mm mesh) were designed into sin-
gle (SL), double (DL), and triple-layered (TL) to approximate the conventional hapa (CH) with ~1
mm mesh normally used in sandfish ocean nurseries. The study was conducted in Maliwaliw island
and in a cove in Buyayawon both located in Eastern Samar, Philippines. Results showed that TL had
the highest juvenile survival (35.93 ±10.56%) in Maliwaliw, which was significantly different (p<
0.05) from SL and DL. The DL design showed the highest survival (25.23 ±17.15%) in Buyayawon
by day 60, followed by TL (21.37 ±3.11%), although not statistically significant. On the other hand,
average growth rate was highest in SL in both sites where survival was also the lowest. Biomass,
however, was the highest in DL in Buyayawon (1,014 ±266 g m-2) followed by TL in Maliwaliw
(925 ±107 g m-2). Sandfish juvenile survival in DL and TL were higher than those in the CH in both
sites suggesting that mosquito nets can indeed be used as an alternative material for rearing early-
stage sandfish juveniles in floating ocean nurseries.
Key words: Ocean nursery, post-settled sandfish, growth, survival, Philippines.
¿Se pueden utilizar redes mosquiteras disponibles en el mercado para criar juveniles del
pepino de mar (Holothuria scabra) en jaulas oceánicas flotantes?
RESUMEN. Este estudio investiga el potencial de los mosquiteros disponibles localmente como
un material alternativo para los criaderos de pepinos de mar en el océano. Los mosquiteros (malla
de ~2 mm) se diseñaron en una sola (SL), doble (DL) y triple capa (TL), para aproximarse al hapa
convencional (CH) con malla de ~1 mm que normalmente se usa en los criaderos de pepinos de
mar en el océano. El estudio se realizó en la Isla de Maliwaliw y en una cala en Buyayawon, ambas
ubicadas al Este de Samar, Filipinas. Los resultados mostraron que el TL tuvo la supervivencia de
juveniles más alta (35,93 ±10,56%) en Maliwaliw, significativamente diferente (p<0,05) de los
diseños SL y DL. La DL obtuvo la mayor supervivencia (25,23 ±17,15%) en Buyayawon al día 60,
seguido de TL (21,37 ±3,11%), aunque no fue estadísticamente significativa. Por otro lado, la tasa
de crecimiento promedio fue más alta en SL en ambos sitios, en donde la supervivencia también fue
la más baja. La biomasa, sin embargo, fue más alta en DL en Buyayawon (1.014 ±266 g m-2) segui-
da de TL en Maliwaliw (925 ±107 g m-2). La supervivencia de juveniles de pepinos de mar en DL
y TL fue mayor que la de CH en ambos sitios, lo que sugiere que las redes mosquiteras pueden usar-
se como un material alternativo para criar juveniles de pepinos de mar en etapa temprana en jaulas
oceánicas flotantes.
Palabras clave: Criadero oceánico, pepino de mar bentónico, crecimiento, supervivencia, Filipinas.
Received: 16 January 2023
Accepted: 2 March 2023
ISSN 2683-7595 (print)
ISSN 2683-7951 (online)
Journal of the Instituto Nacional de
Investigación y Desarrollo Pesquero
This work is licensed under a Creative
Commons Attribution-
NonCommercial-ShareAlike 4.0
International License
Marine and
Fishery Sciences
Can commercially available mosquito nets be used for rearing sandfish
(Holothuria scabra) juveniles in floating ocean nursery?
Guiuan Development Foundation, Inc., Guimbaolibot Avenue, Poblacion Brgy. 10, Guiuan, Eastern Samar, 6809, Philippines. ORCID
Margarita de la Torre-de la Cruz, Jonh Rey L. Gacura,
Racelle R. Rescordado, Janine L. Villamor
Holothuria scabra, commonly known as sand-
fish, are high-value sea cucumber species cul-
tured in the Philippines and other countries. The
success of sandfish grow-out culture largely
depends on the supply of sandfish juveniles. For-
tunately, the technology for juvenile sandfish pro-
duction in land-based hatcheries are well estab-
lished (Agudo 2006; Gamboa et al. 2012; Juinio-
Meñez et al. 2012). Post-settled hatchery-pro-
duced sandfish juveniles (<5 mm in length) are
transferred to ocean nursery systems (Agudo
2006; Gamboa et al. 2012; Juinio-Meñez et al.
2012; Mills et al. 2012) for further rearing. Sand-
fish culture techniques in nursery systems vary in
different countries. In Vietnam, and northern Aus-
tralia, pond nursery systems employ hapa nets
stocked with sandfish juveniles measuring 1-2
mm (Pitt and Duy 2004; Bowman 2012). In New
Caledonia, nursery systems follow two phases
(Agudo 2006). Early-stage juveniles (<5 mm) are
maintained in bare (without sand) tanks until they
reach a size of about 10-20 mm (1 g). Then, they
are transferred to tanks lined with a thin layer of
sand enriched with mud or food supplement.
While this hatchery-based nursery system has
shown good results, this is not practical in the
Philippines because of the high operating cost
and space limitations (Juinio-Meñez et al. 2012).
Marine ponds with sandy substrate are also not
common in the country. To address these bottle-
necks in sandfish juvenile production, the float-
ing ocean nursery system was developed (Juinio-
Meñez et al. 2012).
Ocean nursery rearing of early-stage sandfish
juveniles (~3 mm) uses a conventional hapa
made from fine nylon net with ~1 mm mesh size
(Gamboa et al. 2012; Sinsona and Juinio-Meñez
2019; Altamirano and Noran-Baylon 2020). Juve-
niles are reared for 30-60 d before released to sea
ranch or enhancement sites.
A study conducted in Bolinao (Pangasinan
province) comparing the growth and survival of
sandfish in ocean floating hapas and hapas in
ponds found that survival rates of juveniles in
both hapa systems were similar albeit with lower
average growth rates in ocean nursery (Juinio-
Meñez et al. 2012). Likewise, a study by Cabaca-
ba and Campo (2019) in Guiuan, Eastern Samar,
comparing the growth and survival of sandfish
juveniles in floating hapas and those in rearing
tanks, showed better growth of juveniles in the
floating hapas but lower survival rate. However,
the difference in the survival rate was not signifi-
cant. Same authors recorded 64.88% survival of
1,000 early sandfish juveniles stocked per hapa in
floating ocean nursery after 45 d of rearing, while
Altamirano and Noran-Baylon (2020) recorded
70.5% survival after 60 d. According to Juinio-
Meñez et al. (2012), ocean nurseries using float-
ing hapas are cost-effective and strategic for com-
munity-based grow-out and sea ranching. How-
ever, the fine nylon mesh net (~1 mm) used in
ocean nursery systems is not readily available in
local stores in Eastern Samar nor in Eastern
Visayas. They came from Western Visayas and
are rather expensive for small-scale fishers who
want to go into sandfish rearing. One piece of
locally available mosquito net costs only about
USD 3.00, whereas fine mesh nets cost USD
30.00 a piece, including handling and delivery
costs. Hence, this study was conducted to investi-
gate the potential of using locally available mos-
quito nets as an alternative material for rearing
early-stage sandfish juveniles in floating ocean
Field experiments were conducted from March
to May 2021 in the nearshore waters of Barangay
(smallest political unit in the Philippines) Mali-
waliw, Salcedo (Site 1), and in Barangay Buyaya-
210 MARINE AND FISHERY SCIENCES 36 (2): 209-217 (2023)
won, Mercedes (Site 2) in Eastern Samar, Philip-
pines (Figure 1). Site 1 (11.10513° N-125.58088°
E) is adjacent to a mangrove and seagrass bed and
exposed to moderate to strong wave action. Site 2
(11.10886° N-125.69852° E) is a cove with min-
imal wave exposure, and water flow/circulation is
constrained by a provincial road cutting through
and made possible only through a short bridge.
Some houses are situated along the coastline of
the cove which could be a potential source of
nutrient inputs into the water.
Mosquito nets used has a dimension of 1.7 m ´
0.9 m ´1.2 m (length ´width ´height) and do not
have uniform mesh size. Because of the mesh size,
three designs were tried: single-layer (SL), dou-
ble-layer (DL), and triple-layer (TL) alternating
bigger and smaller mesh sizes. The DL and TL
were made by overlaying 2 and 3 mosquito nets,
respectively. To prevent flapping of the overlayed
nets while at sea, the bottom and sides of nets
were sewed horizontally and vertically (Figure 2).
For each site, 12 hapas were installed consisting
of triplicate of each mosquito hapa net design, and
the conventional hapa. Each hapa net is attached
to a rectangular frame (2 m ´1 m) made from
PVC pipe (4" diameter). To maintain the rectangu-
lar shape of the bottom, a rectangular perforated
(2 m ´1 m) frame made from 3/4" blue PVC pipe
were also attached to each hapa net. Improvised
sinkers made from re-used plastic bottles (~1 l)
filled with sand were also attached to the four cor-
ners of the hapa net.
Prior to stocking juveniles, nets were pre-con-
ditioned for three days, following nursery culture
Figure 1. Location of experimental sites in Eastern Samar, Philippines. Data Source: NAMRIA Administrative Map, GDFI
2022.WGS84. QGIS 3.16.