MARINE AND FISHERY SCIENCES 36 (2): 209-217 (2023)

https://doi.org/10.47193/mafis.3622023010504

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.

209

*Correspondence:

mtdelacruz1909@gmail.com

Received: 16 January 2023

Accepted: 2 March 2023

ISSN 2683-7595 (print)

ISSN 2683-7951 (online)

https://ojs.inidep.edu.ar

Journal of the Instituto Nacional de

Investigación y Desarrollo Pesquero

(INIDEP)

This work is licensed under a Creative

Commons Attribution-

NonCommercial-ShareAlike 4.0

International License

Marine and

Fishery Sciences

MAFIS

TECHNICAL PAPER

Can commercially available mosquito nets be used for rearing sandfish

(Holothuria scabra) juveniles in floating ocean nursery?

MARGARITA DE LA TORRE-DE LA CRUZ*, JONH REY L. GACURA, RACELLE R. RESCORDADO and JANINE L. VILLAMOR

Guiuan Development Foundation, Inc., Guimbaolibot Avenue, Poblacion Brgy. 10, Guiuan, Eastern Samar, 6809, Philippines. ORCID

Margarita de la Torre-de la Cruz https://orcid.org/0000-0002-6947-5632, Jonh Rey L. Gacura https://orcid.org/0000-0002-3265-0150,

Racelle R. Rescordado https://orcid.org/0000-0002-8290-7268, Janine L. Villamor https://orcid.org/0000-0003-3821-4488

INTRODUCTION

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

nurseries.

MATERIALS AND METHODS

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

211

DELATORRE-DE LA CRUZ ET AL.: SANDFISH OCEAN NURSERY CULTURE USING MOSQUITO NETS

Figure 1. Location of experimental sites in Eastern Samar, Philippines. Data Source: NAMRIA Administrative Map, GDFI

2022.WGS84. QGIS 3.16.