Marine Fish Culture, Development, and
Status in Indonesia
Muhammad
Murdjani[1]
Abstract
Indonesia has began the development of marine fish culture to avert the
over-exploitation of wild populations, to protect endangered species, and to
increase export earnings. Groupers,
wrasses, and seabasss are the species cultured. Some success was achieved in the production of eggs and larvae
from broodstock in the laboratory. The
hatching rates for Cromileptes altivelis, Epinephelus guttatus,
and Plectropomus leopardus were consistently high during the trial
runs. The grouper, C. altivelis,
produced eggs that survived to Day 60 while C. undulatus produced eggs
that were reared to Day 15. However,
there are still constraints in the mass-culture of these species.
The Indonesian archipelago has a shoreline extending
to 81,000 km long. The marine
ecosystems along this shoreline is characterised by high diversity (Soekarno,
1996). The marine resources are
exploited and are threatened by overexploitation, habitat destruction, and
pollution.
Indonesia has a strong commitment to sustainable
utilisation of marine resources.
As such, aquaculture is one of the long-term strategies to achieve this. The long coastline and diversity of marine fauna provide a great opportunity for mariculture to be developed in the country. In addition, the government of Indonesia is supportive of the development of aquaculture to increase export earnings, sustainable use of marine resources from the wild, and to protect endangered species from extinction.
To date, Indonesia has made inroads in mariculture of
groupers and wrasses, which are economically important. This paper reviews various aspects of this
development and highlights significant results in producing eggs and larvae
from broodstock.
The
species that are potentially suitable for culture in floating net-cages and pen
systems belong to the Serranidae, Labridae, Lutjanidae, Siganidae, and
Latidae (Table 1). All except the Latidae are found in coral
reefs.
The coastal ecosystem of Indonesia includes mangrove forests, seagrass beds, and coral reefs. There are five structural types of coral reefs, namely, fringing reefs, barrier reefs, atolls, apron reefs, and patch reefs (Suharsono, 1994). These reefs have highly diverse assemblages of reef fauna, including approximately 350 species, belonging to 75 genera. Based on surveys using the line transect method, the condition of 6% of the reef areas are excellent, 24.5% good, 29.2% fair, and 41.2% poor (Soekarno, 1994 and Suharsono, 1994).
Table 1.
Species of fishes that are potentially suitable of culture
|
family |
scientific name |
common name/s |
|
|
Cromileptes altivelis |
humpback grouper |
|
|
Epinephelus tauvina |
estuarine grouper |
|
|
E. malabaricus |
Malabar grouper |
|
Serranidae (groupers) |
E. fuscoguttatus |
mottlet grouper |
|
|
Plectropomus leopardus |
leopard coral trout |
|
|
P. maculatus |
spotted coral trout |
|
Labridae (wrasses) |
Cheilinus undulatus |
humbhead wrasse |
|
|
Lutjanus johni |
gold snapper |
|
Lutjanidae (snappers) |
L. argentimaculatus |
mangrove snapper |
|
|
L. sanguineus |
red snapper |
|
|
Siganus javus |
streaked spinefoot |
|
Siganidae (rabbitfishes) |
S. canaliculatus |
white-spotted spinefoot |
|
|
S. guttatus |
yellow-blotch spinefoot |
Grouper and some species of coral fishes are selected
species that are suitable to rear in floating net-cages and pen systems. Seed or fingerlings are available either
from the wild stock or finfish hatcheries.
Culture Systems
The
culture system can be divided into two phases, nursery and grow-out
phases. There are two types of nursing
phase: the nursing from fingerling to juvenile for 3 - 4 months, and the other
one is nursing juvenile prior to releasing into grow-out for 1 - 4 weeks. The grow-out phase is to grow the fish from
juvenile to marketable size for 6 to 12 months, depending on the optimal value
for the specific market.
Broodstock
development
Collection and domestication of spawners are the first
priorities in seed-production. This
step has been difficult because the collection of male from the wild is quite
difficult and sex-reversal may occur.
Being protogynous hermaphrodites, males appear to be fewer in the wild
possibly due to overexploitation of larger individuals in a population. In the laboratory, sex-reversal may occur as
a result of density-dependent factors such as stocking density, sex ratio, and
capacity of enclosure.
After establishing the broodstock, a special diet for
the spawners was developed as nutritional components of the diet affect egg
quality. Likewise, fertilisation rate,
hatching rate, larval strength and feeding success are all related to the
quality of eggs produced by the broodstock.
It was found out that the success of grouper hatchery depends mostly on
getting good quality eggs. With low
quality eggs, the mortality during first week of larval rearing was disastrous.
Spawning in captivity
Before the induction of spawning, maturity of fish is determined from either the morphological appearance or gonadal condition. All the fish selected for spawning are healthy and free from injury and parasites. Fish were induced to spawn either by hormonal treatment (LHRH-@, HCG and Puberogen with dosage used based on the weight of the spawner and varies widely according to maturation condition of the spawner) or by environmental manipulation (of water temperature in combination with circulating water level).
The Regional Brackishwater Aquaculture Development
Centre (RBAC) has conducted induction of spawning for 5 species of groupers and
1 species of wrasse (Cromileptes altivelis, Epinephelus fuscoguttatus, E.
malabaricus, E. tauvina, Plectropomus leopardus, and Cheilinus
undulatus). These laboratory
inductions were done during 1995-1996 (Table 2). These inductions were successful in producing eggs. The hatching rates have a wide range that
can be attributed to the size of the fish that was induced to spawn. The mean hatching rates are high for C.
altivelis, E. guttatus, and P. leopardus and fairly
consistent throughout the trial runs.
The grouper, C. altivelis, produced eggs that survived to Day 60
in September and October 1996 while C. undulatus produced eggs that were
reared to Day 15 (Table 2). This result
for C. altivelis and C. undulatus indicates the feasibility of
producing fry for cage culture from broodstock.
Egg collection
Eggs are collected from the spawning tanks using a
fine mesh (200 mm) seine net in the morning after spawning. The collected eggs are washed repeatedly through a series of
filter screens to remove debris that have adhered to the eggs. The eggs are then placed in graduated
cylinders or aquarium for density estimation.
Normally, fertilised eggs float while the unfertilised eggs settle to
the bottom of the container.
Unfertilised eggs are later removed by siphoning.
Fertilized eggs are then transferred to the incubation
tank at a density of 100-150 eggs/litre.
The eggs will hatch about 15-18 hours at 26-28oC after
spawning. Dead eggs that settled at the
bottom are removed by siphoning. The
newly hatched larvae are carefully collected the following morning by scooping
them with a beaker and are immediately transferred to larval rearing tanks.
Larval rearing
The rearing tanks are commonly fabricated from
plastic, fibreglass, or concrete. A
typical larval rearing tank is rectangular in shape, ranging from 8-10 tons in
volume, and is located outdoors. The
initial stocking density for newly-hatched larvae in rearing tank is between
50-100 larvae/litre. The salinity for
larval rearing is at 30-31 ppt while the water temperature is at 26 - 28oC
to promote fast growth of larvae.
Grading
Heavy mortalities occur in the tanks due to
cannibalism and stress so proper grading was done to reduce or avert
cannibalism Grading is usually done a week after the larvae started feeding on Artemia
(i.e. Day 17-30) and every week thereafter.
Table 2. Range
of egg production, hatching rates (HR), and survival rates (SR) of groupers and
wrasse in controlled laboratory conditions (D-day; figures rounded up to the
nearest 1,000)
Species
|
Period of spawning |
No. of trials |
No. of eggs
|
HR range |
HR mean (s. d.) |
SR range |
|
Cromileptes
altivelis |
11/95-11/96 |
12 |
450-10,600 |
60-90% |
79.17% (8.12) |
0.01% D-5 to 5.0% D-30 |
|
Epinephelus
fuscoguttatus |
04/95-11/96 |
18 |
3,750-60,700 |
60-90% |
76.11% (8.75) |
|
|
E.
malabaricus |
03/96-11/96 |
9 |
1,000,000-5,000,00 |
25-80% |
60.55%
(19.92) |
|
|
E.
tauvina |
04/96-11/96 |
8 |
690,000-2,600,000 |
30-80% |
60.62%
(17.75) |
|
|
Plectropomus
leopardus |
11/95-05/96 |
7 |
450,000-2,109,000 |
60-80% |
75.71% (7.76) |
|
|
Cheilinus
undulatus |
09/95-11/96 |
13 |
700-10,600,000 |
30-80% |
66.15%
(16.07) |
0.01% D-5 to 0.01% D-15 |
|
Feed |
Size
|
Time of feeding |
Feeding frequency |
Density/amount
|
|
algae (Chlorella sp.) |
5-20 u |
Day 1-5 |
1/day |
4-5 x 10,000/ml |
|
rotifera (Brachionus
spp.) |
50-175 u |
Day 3-12 |
4-5 times/day |
3-5/ml |
|
brine shrimp nauplii
(Artemia spp.) |
250 u |
Day 10-23 |
2-3 times/day |
2-3/ml |
|
Subadult and adult brine
shrimp |
1 mm |
Day 20-60 |
2-3 times/day |
on demand |
|
minced fresh marine fish
(sardines) |
2-5 mm |
Day 30 - harvest |
2-3 times/day |
on demand |
Food preparation
The most popular initial food for early life of larvae
among finfish hatchery operators is the rotifer, Brachionus plicatilis. It is also suggested that the use of
nauplius of copepods, Acartia spp. improves larval survival of
grouper. These zooplankton are cultured
in a large-scale and fed with phytoplankton one of which is Nannochloropsis.
The other factor that causes high
mortality in the culture system is disease.
The most common symptoms of diseases of larval rearing are loss of
appetite, loss of scales, change of body colour, and occurrence of white spots
on the body.
Treatment was done immediately as these symptoms
occur. The treatments include for white
spot; immersion of fry in water at reduced salinity of 15-20 ppt with the
addition of 20 ppm formalin for 1-2 hours and for bacterial infection,
immersion in 3 ppm oxytetracycline for 10 hours.
Fishermen in Indonesia use cyanide in collecting
seedlings for culture. This destructive
fishing practice, in addition to the high harvesting effort on adults, is
considered detrimental to the ecology coral reef ecosystem and the sustainable
use of marine resources. Thus, efforts have been conducted Indonesia to address
this. For example, in order to prevent
fishermen from using destructive fishing methods such as cyanide, an economic
and pragmatic approach is required.
Education and information is not enough to solve the problem; the
employment of fishermen that gives them a regular income and allows a better
standard of living is likewise very important in terminating destructive
fishing activities. In the long run, these solutions will result in the rehabilitation
and recovery of damaged coral reefs and its fish populations. Another solution is through research and
development of marine finfish culture, in particular of coral reef fishes and
sea bass. The Central Research
Institute for Fisheries (CRIFI), National Seafarming Development Centre (NSDC),
National Brackishwater Aquaculture Development Centre (NBADC), and Regional Aquaculture Development Centre (RBADC) have
achieved impressive results in propagating, in captivity, different grouper
species (Epinephelus spp., Cromileptes altivelis), snappers (Lutjanus
spp.), wrasse (Cheilinus undulatus), and sea bass (Lates calcarifer). In addition, regulations are in place for
catching and export of threatened species like the Napoleon wrasse in order to
protect this endangered species and its natural habitats.
The tropical reef fishes especially groupers and
wrasses, are in high demand in Asia, especially in Hong Kong and China. The demand for groupers is not limited to
Hong Kong and Singapore but extends to the big cities in other Southeast Asian
countries. Thus, groupers and wrasses
fetch good prices in the market (Table 4).
Table 4. Price
list of live groupers in Bali (prices
as of September, 1995 from Kumagai, 1996)
|
Indonesian
name |
Scientific
name |
Size
|
Price
|
|
Kerapu
tikus Kerapu
lumpur Kerapu
malabar Kerapu
macan Kerapu
sunu Ikan
napoleon |
Cromileptes
altivelis Epinephelus
suellus Epinephelus
malabaricus Epinephelus
fuscogutattus Plectropomus
leopardus Cheilinus
undulatus |
=>1.5 kg =>5.0 kg =>5.0 kg =>5.0 kg =>2.0 kg =>10 kg |
Rp. 120.000/kg Rp. 18.000/kg Rp. 18.000/kg Rp. 18.000/kg Rp. 32.500/kg Rp. 45.000/kg |
Another species in high demand and with the highest
commercial value is the Napoleon (humphead) wrasse (Cheilinus undulatus). Despite the ban, the harvest and export of
this species still continues because local laws are very difficult to
enforce. The price depends on the
season (before Chinese New Year and other festivities the prices are reaching
top level). The retail price in Hong
Kong is approximately higher than in Indonesia. Thus, there is a great temptation for local fishermen to catch
Napoleon wrasse with cyanide. Other
coral reefs species which are in high demand and have high commercial value are
the humpback grouper, Cromileptes altivelis, and the Malabar grouper, Epinephelus
malabaricus.
The development of aquaculture in Indonesia
particularly marine finfish culture has improved significantly. Opportunities of marine finfish culture
development still abound although there are constraints, namely;
·
lack of hatchery
technology for snapper, and wrasses;
·
standardisation of
hatchery technology for grouper; and
· difficulty in the recognition, identification, segregation and catching of fry of cultivable species
·
difficulty in the
recognition, identification, segregation and catching of fry of cultivable
species;
·
rapid destruction of the
natural environment of different cultivable species;
·
limited knowledge on the
biology of the different marine cultivable species, except for milkfish,
seabass, rabbitfish, mullet and grouper;
·
lack of knowledge of
basic data on nutrition, feeds and feeding habits of various species needed for the formulation of test diets.
To address these constraints, the following recommendations are identified:
·
intensify studies in the
hatchery technology for cultivable species of groupers;
·
expand studies on the
identification and availability of larval finfish with potential for
aquaculture;
·
conduct studies to
develop culture technology appropriate for various cultivable species;
·
pursue nutrition studies
and preparation of test diets for cultivable species; and
·
promote and maintain
international collaboration among institutions engaged in mariculture and
solicit support from developed countries.
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[1] Regional Brackishwater Aquaculture Development Centre, Situbondo, East Java, P.O. Box 5 Panarukan, Situbondo 68351, Indonesia