Aquaculture Management of Blue Swimming Crab (Portunus pelagicus) in Boncong Bancar Marine Farming Facility, Tuban Regency, East Java Province, Indonesia
Aquaculture Management of Blue Swimming Crab (Portunus pelagicus) in Boncong Bancar Marine Farming Facility, Tuban Regency, East Java Province, Indonesia
Blue Swimming Crab (Portunus pelagicus) is Indonesia's
highly economically valuable fishery commodity. It ranks third among export
commodities in volume, following shrimp and fish. In 2011, Blue Swimming Crab
exports reached 42,410 tons with a value of approximately IDR 978 billion (1). The high demand for Blue Swimming Crab has led to intensive
exploitation of this resource, affecting both stock availability and a decline
in productivity and recruitment capacity within the exploited populations (2). With high-intensity exploitation occurring in all its distribution
areas, from shallow coastal waters to offshore regions, the availability of
Blue Swimming Crab is progressively decreasing (3).
Direct harvesting of Blue Swimming Crabs
from natural habitats appears insufficient to meet export demand. In countries
such as the United States, Japan, Taiwan, and Australia, Blue Swimming Crab
remains a significant dietary item, constituting a strategic export market (4). While aquaculture presents a potential solution to meet market
demands, the scarcity of skilled human resources remains a primary constraint.
Therefore, promoting Blue Swimming Crab aquaculture and providing training
opportunities in suitable regions are essential (1). Given these challenges, this study was undertaken to
gain firsthand experience and skills in Blue Swimming Crab aquaculture
techniques at the Boncong Bancar Marine Farming Facility in Tuban Regency, East
Java Province.
Experimental
Section
Data
Collection
The
methodology employed in this study used a descriptive approach. Descriptive
methodology involves gathering data directly from experts and relevant
literature related to the case under investigation (5). It extends beyond data collection
to encompass analysis and discussions regarding the collected data.
Data
Collection Techniques
Data collection in this Internship Program
incorporated two methods: primary data and secondary data. Primary data was
obtained through observation, interviews, and active participation, while
secondary data comprised information collected and reported by individuals for
specific purposes or scientific knowledge.
Declarations
Conflict of Interest
The author declares no conflicting interest.
Data Availability
The unpublished data is available upon request to the corresponding author.
Ethics Statement
Not applicable.
Funding Information
Not applicable.
References
Primary
Data
Observation
Observation involved systematic data
collection through observation and recording of activities related to Blue
Swimming Crab aquaculture techniques at the Boncong Bancar Marine Farming
Facility in Tuban, East Java.
Interviews
Interviews were conducted to gain in-depth
knowledge about the subject matter, conduct preliminary studies, and identify
research areas that require investigation. This technique relied on
self-reports or personal knowledge and beliefs (6).
Active Participation
Active participation required the
researcher to engage directly in activities related to Blue Swimming Crab
aquaculture. This encompassed seed selection, water quality measurement,
feeding, pest and disease management, harvesting, and packaging. tics
Secondary
Data
Secondary
data consisted of information collected from documents, journals, magazines,
and articles. These data sources did not directly provide information to the
data collector but served as valuable references for the research, aligning
with the research topic and objectives (6). Combining
primary and secondary data collection methods enabled a comprehensive
exploration of Blue Swimming Crab aquaculture practices, making this research
valuable for the aquaculture industry and fisheries experts.
Result
and Discussion
General Condition of MFF Boncong
MFF Boncong,
established in 1981, underwent several name changes, initially PRUG (Pembenihan
Rakyat Udang Galah) and later UPPB (Unit Pengelolaan Perikanan Budidaya) before
adopting its current name, MFF, in 2015. The choice of cultivation commodities
also evolved to meet market demand. Initially, it focused on freshwater prawns
(Macrobrachium rosenbergii), shifting to tiger prawns (Panaeus
monodon) in 2004 due to increased demand. Over the years, it diversified
into vannamei shrimp, eel, tiger groupers, coral groupers, seahorses,
mangrove crabs, blue swimmer crabs, and lobsters. These changes reflect MFF
Boncong's adaptability in responding to market dynamics.
MFF Boncong Tuban, East Java, is at 111°44'39.33'' E longitude and
6°46'18.43'' S latitude. It is located along Jalan Raya Semarang Km 41, in
Boncong Village, Bancar Subdistrict, Tuban Regency, East Java. The installation
is on the northern coast of Java, characterized by relatively calm sea
conditions and sheltered from the open sea. The surrounding environment
includes a river to the west, aquaculture areas to the east, and a sandy
northern shoreline. The facility's temperature averages around 30°C, and
freshwater is sourced externally due to saltwater intrusion, with the location
depicted in Figure 1.
Rearing
Facility
Water
Supply System
The water supply for aquaculture at MFF,
sourced from the sea, utilizes innovative methods for seawater management.
Seawater is conveyed through 20 cm diameter PVC pipes, harnessing the pressure
of ocean waves and gravity. This sustainable water transport approach aligns
with recent research findings promoting environmentally friendly aquaculture
practices (7). The flowing water is collected in
underground seawater reservoirs, where it undergoes treatment and
sedimentation, following established water treatment principles in aquaculture (8). A dose of 10 ppm of calcium
chloride and 5 ppm of thiosulfate is added to neutralize the water. After
treatment, the water is pumped to a storage tank, ensuring the culture medium
is optimized for crab rearing (9).
Figure 1. Location of MFF Boncong in Tuban Regency (A) and MFF Boncong by Google map (B).
Fresh seawater for crab cultivation is
typically prepared at night to replace the morning water. This rotation helps
maintain a cleaner and healthier environment for the crabs as the pond becomes
soiled from residual feed and molting. The weekly requirement of approximately
3600 liters per pond.
In contrast, freshwater for other activities
within MFF, including employee hygiene and reducing parasitic risks in grouper
fingerlings, faces a unique challenge due to seawater intrusion. As described
by (10), seawater intrusion into freshwater
sources is a growing concern in coastal areas. The previous year, freshwater
was sourced from a 5-meter deep artesian well. However, this source has been
rendered unusable due to seawater intrusion, with the salinity reaching 26 ppt,
underscoring the pressing need for alternative freshwater sourcing and
management strategies in the region.
Aeration
System
The supply of dissolved oxygen in the
crab-rearing environment is crucial for various activities and the breakdown of
organic matter within the ponds. Oxygen is primarily obtained through natural
air diffusion and aeration hoses installed in each pond. Research by
(11), highlights the critical role of
dissolved oxygen in aquaculture, emphasizing its direct impact on the growth
and health of aquatic organisms. Each crab-rearing pond is equipped with six
aeration hoses. These hoses are installed in series within one pond and parallel
across different ponds, facilitating control during feeding without disrupting
aeration in other ponds.
Pond
Construction
The construction of crab-rearing ponds at MFF
Boncong entails rectangular ponds with a depth of 100 cm, a length of 2.5 m,
and a width of 1.2 m. These concrete ponds are equipped with 3 cm inlet and 8
cm outlet PVC pipes. Additionally, a string is affixed at the top of each pond to
suspend the aeration hoses.
The construction of the ponds necessitates
consideration of water retention. A well-constructed pond retains water volume
unless water loss is due to evaporation caused by elevated temperatures.
Normally, increased temperatures have minimal impact on cultivated biota, as
the evaporation rate typically results in only a 1 cm reduction in water level,
prompting periodic water replacement.
Rearing
Activities
Water
Quality Management
The rearing of mud crabs places significant
emphasis on water quality management. Dissolved oxygen levels, pH, salinity,
and water temperature are meticulously controlled to ensure the well-being of
the crabs. Water quality measurements are taken three times a day, specifically
at 7 AM, 12 PM, and 5 PM, as these intervals coincide with expected changes in
water quality. Although MFF typically conducts measurements twice daily, the
additional measurement aims to capture fluctuations during these key timeframes.
During observations, pH levels range from 6 to
8, and salinity falls between 30 and 35 ppt. According to Juwana and
Romimohtarto (2000), salinities between 25 and 35 ppt are suitable for crab
survival. A temperature of 32°C aligns with recommended crab farming
conditions, as Juwana and Romimohtarto (2000) suggested. Likewise, during this
study, water temperatures ranged between 29°C and 33°C, in line with
literature. Dissolved oxygen levels averaged between 5.0 ppm and 8.4 ppm over one
month, which is considered favorable, as Suharyanto (2012) indicated that
dissolved oxygen levels of 6 to 8 ppm are ideal for crab cultivation.
Feeding
Management
At MFF Boncong, crab feeding is
conducted three times daily, scheduled for 7 AM, 3 PM, and 9 PM. Feed is
administered at a rate of 3-5% of the crab's body weight. Upon the arrival of live
fish feed, it is immediately prepared, frozen, and provided during designated
feeding hours. Any residual feed is siphoned to prevent contamination of the
pond. Feeding is typically done by scattering feed near the crabs' shelters. It
is imperative that feeding does not extend beyond the allocated time to prevent
cannibalism and protect smaller or molting crabs.
Facilities
Maintenance
Efficient rearing activities are contingent
upon proper infrastructure maintenance. Routine maintenance of facilities and
equipment is conducted at MFF. Pond cleaning is executed using high-pressure
water spray whenever the pond appears dirty. Algal growth is the primary
concern on shelter walls and pond surfaces. Tanks and equipment are thoroughly
cleaned and dried. Aeration equipment is checked every morning, and any clogged
aeration stones are replaced with clean ones while the soiled stones are
cleaned and dried. This maintenance is essential to preserve the equipment's
functionality and ensure it does not disrupt the growth of the cultivated
crabs.
Disease
Control
To date, there have been no serious
diseases affecting mud crab rearing. Effective water quality management
contributes to the crabs' health and growth. However, the mud and sedimentation
culture of the crabs may result in sediment adhering to the crabs' backs,
making them appear dirty and unattractive. This condition can attract other
organisms if left unaddressed, especially when coupled with the inactivity of
the crabs.
The
primary method of control involves brushing the crabs' backs with a toothbrush
when they become visibly dirty, as indicated by a dark, soiled appearance.
Crabs that are uncomfortable with the accumulation of dirt exhibit behaviors
such as scratching their bodies with their claws and pincers or rubbing their
bodies against the shelters.
Harvesting
Mud crab harvesting is typically carried out
when the crabs reach an age of 4 to 5 months, with a size of 1 kg, containing 3
to 4 crabs per kilogram. This corresponds to individual crab weights ranging
from 250 to 330 grams. The harvesting process is straightforward and involves a
one-day fasting period to empty the crabs' digestive tracts. Subsequently, the
water level in the pond is reduced to 25%. The crabs are then caught in nets
and placed in refrigerators or freezers at a temperature of 20°C. Once the
crabs become semi-immobile or deceased, they are ready for sale.
Marketing
The matured
crabs are marketed to various consumers, including restaurants in Tuban and
middlemen. In restaurant-scale sales, prices can reach Rp. 150,000 per
kilogram, while middlemen typically purchase at rates around Rp. 95,000 per
kilogram. Crab farming appears to have favorable marketing prospects, with
demand increasing in Tuban. However, natural production levels have not yet met
this growing demand. In conclusion, the future of mud crab aquaculture seems
promising, with effective demand creation indicating continuous growth in
marketing.
Production
and Business Analysis
Production
In the context of mud crab
aquaculture, the measure of success lies in the production volume over a given
timeframe, coupled with market pricing. Survival Rate (SR) for Mud crab is
typically around 95%, indicating a harvest of 608 crabs. Given that the size of
a Mud crab after 5 months is approximately 1 kg with 3 crabs per kilogram, each
harvest generates 155 kg or 15.5 quintals for 16 ponds.
Business Analysis
After harvesting the swimming crab, the
business and determination of the Break Even Point (BEP) is analysed. There are
16 pools for the swimming crab business, with each pool measuring 1.2 x 2.5
meters. This setup yields a production of 15.5 quintals or 155 kilograms per
cycle. Selling this at a rate of Rp.95,000 per kilogram to middlemen results in
a total revenue of Rp.465,719,000 per cycle.
BEP represents the minimal time
required to recoup the initial investment in a business venture. The BEP
equation can be derived as follows:
Upon totaling the expenditure
requirements and the initial capital needed over a period of 5 months, which
amount to Rp. 298,290,917, the break-even point is reached within a single
production cycle. Moreover, a profit of Rp167,428,728 is achievable.
Business
Development in Mud Crab Cultivation
Challenges
One of the challenges encountered in
Mud crab cultivation is the cannibalistic nature of these crabs. This behavior
can reduce the Survival Rate (SR) when ponds lack sufficient shelters and
inadequate feed supply. Maintaining water quality to ensure crab health and
sustained growth is also a significant concern. Another challenge lies in
controlling the electricity supply to run aerators, a crucial factor in
ensuring adequate oxygen levels through aeration.
Future Business Prospects
Considering the Break-Even Point
(BEP) and the monthly profit, Mud crab aquaculture holds significant potential
for the future. This potential is substantiated by the unmet demand for Mud
crab in Tuban, which remains unsaturated. Advancements in technology and
research can potentially mitigate challenges such as cannibalism, offering
solutions to enhance productivity. As such, local, national, and international
demands for Mud crab can be satisfied over time.
The increasing demand for this crab
delicacy and technological advancements position mud crab aquaculture as a
promising venture with significant growth potential. This supports the local
market and creates potential for expansion into regional and international
markets.
Conclusion
In summary, mud crab cultivation is a relatively
straightforward and disease-resistant marine aquaculture. Routine water quality
management enhances growth with minimal disease risks. Challenges include
cannibalistic behaviors, particularly during low feed availability and molting,
but these can be mitigated by providing adequate shelter for the crabs in the
ponds. The ease of mud crab farming and the unmet demand to date make it a
promising business venture, especially in Tuban, where demand remains
unfulfilled due to the seasonal dependence on wild catches.
This study was conducted at the Boncong Bancar Marine Farming Facility in Tuban, East Java, focusing on Blue Swimming Crab (Portunus pelagicus) aquaculture. As a high-value seafood commodity with crucial export markets, the study aimed to enhance knowledge and skills, providing valuable insights for students and stakeholders. It emphasized the need for sustainable aquaculture to reduce reliance on wild harvesting, as Blue Swimming Crab demand exceeds natural supply. The research adopted a descriptive approach, including biological characteristics, survival rates, behavior, water quality, and feeding techniques according to MFF Boncong standards. Water quality measurements resulted in an average pH of 6 to 8, temperatures not exceeding 33°C, dissolved oxygen levels between 5.0 ppm and 8.4 ppm, and salinity between 30–35 ppt. In summary, Blue Swimming Crab aquaculture offers a profitable business opportunity, contributing to the country’s foreign exchange reserves, and warrants close attention from fisheries experts.
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