An Introduction of Light Traps for Sampling Freshwater Shrimp and Fish in the Barito River, South Kalimantan
A set of light traps were used to sample freshwater shrimp and fish from Barito River in Banjarmasin, South Kalimantan. Each of five collapsible traps (same size and shape) and of four different traps (box-shape, wire-stage, bamboo-stage and minnow nets) was assigned with one of LED lamps or incandescent lamps. A total of 231 shrimps and 34 fishes were collected during the 6-night sampling periods of March 2009. The shrimp catch was dominated by the Macrobrachium sp. (99.6%) with size ranges varied from 24-85 mm total length. The fish catch composed of Oxyeoleotris urophthalmus (38.2%), Glossogobius giuris (20.6%), Oxyeoleotris marmorata (17.6%), Flounder pleuronectes (8.8%), Puntioplites bulu (5.9%), Mastacembelus erythrotaenia (5.9%) and Osteochilus melanopleura (2.9%) with size ranges varied from 60-310 mm total length. It can be concluded that color or relative intensity of light had strong effects on number of catch collected, where LED traps appear to be more effective than incandescent ones. The Minnow nets collected significantly number of catch compared to other three traps regardless white LED lamps and ordinary incandescent ones. The effect of size and shape of the traps that influenced number of catches was further discussed in this study.
In Indonesia, traditional fisherman using Prayang trap equipped with a kerosene
lamp or the fixed Bagan trap with petromaks lamp to lures Black tiger shrimp
Penaeus monodon into the traps from the shrimp ponds (Kawamura
et al., 1983). In general, the light traps have become increasingly
popular for sampling fish and squid (Thorrold, 1992),
larval and juvenile fishes (Hernandez and Shaw, 2003;
Lindquist and Shaw, 2005; Marchetti
et al., 2004), marine crustacean (Holmes and
OConnor, 1988; Meekan et al., 2001)
or freshwater shrimp and fish (Collier et al., 1997;
Aswadirani, 2003; Mukhlasin, 2004;
Ahmadi et al., 2008). The light traps are also
very useful when towed nets are ineffective or prohibited (Brogan,
1994; Hernandez and Shaw, 2003). Light traps used
here, typically using battery-powered incandescent bulbs, chemical light stick,
blacklight fluorescent (UV) or electrical lamps, while the use of LED lamps
has not much been performed under field condition. As for the difference in
light sources, each lamp has its unique optics and intensity output even same
electrical power use.
At present, many types of traditional fishing gears are operated in the Barito
River, including the use of harmful fishing methods (e.g., poisoning, electrofishing)
that threaten the useful aquatic animals life in the river. In the past,
about 350 species was found in Barito River but now it possibly exist only about
150 species. This is mainly attributable to the destructive fishing and water
pollution, among others. Several types of local fish are considered currently
extinct and endangered fish such as the Arowana, jelawat, kalui, kelabau, belidah,
baung and sanggam. Therefore, fishing technology development that environmentally
friendly and efficient, should be promoted. The use of light would be a potential
fishing method for harvesting freshwater shrimp and fish from the Barito River.
In line with this, from time to time the automated light traps were developed
from the conventional devices.
There was no scientifically published information on the use of light traps in Barito River, so far. It is claimed to be the first sampling method used for collecting shrimp and fish in this river. However, before light traps can be used quantitatively, several potential biases have to be considered. What species will be sampled by the light traps? How effective light traps used in high turbidity of the river? Are individual species collected in different numbers using specific colors/relative intensities of light? Do size and shape of the light trap affect number of catch? We performed this study to address these questions by extracting the sampling data collected from the Barito River.
MATERIALS AND METHODS
Study area: South Kalimantan is one of the 4 provinces in Kalimantan (formerly called Borneo) with capital city of Banjarmasin. It lies between W114°19'13" and E11°33'30" and between N1°21'49" and S44°10'14". It is bordered with East Kalimantan at the north, with Makassar Strait at the east, with Java Sea at the south and with West Kalimantan and Central Kalimantan at the west. Total area is 37.000 km2, 57% or about 21.000 km2 is forest and mountains range with altitude of 1.000 to 1.500 m above sea level. It closes to the equator line with the temperature ranged from 17-36.2°C, humidity rate of 81-90%, sunshine of 40-90%, with the average rainfall of 236 mm and rain days about 157 days/year. South Kalimantan is also often called Province of a thousand-river where the Barito River is the largest and the longest river in Indonesia with more than 6.000 km long. One of its tributary rivers is the Martapura River which in turn has two tributary rivers of its own, namely Riam Kanan and Riam Kiwa where the dams were constructed permanently. Barito River also connects with the Negara River which branches out into lesser rivers. It carries high sediment contains causing the water to be turbid and brownish in appearance (rather bluish at the area close to the ocean) but slightly better compare to Mahakam River in East Kalimantan. The river allows for transportation, drinking water sources, recreational activity and fisheries.
Shrimp and fish were sampled with light traps from the Barito Riverbank during 6-night periods of March 2009. The sampling area was located at Basirih Village about 10 km from Banjarmasin City (Fig. 1), ranged from S03° 19.012' to S03° 20.665' and from E114° 34.098' to E114° 36.296' determined by the GPS 60 (Garmin Co. Ltd., Taiwan). The experimental environments consisted of highly turbid, slow flowing and rarely vegetated habitat with water depths varied from 2-4 m. Visibility of the water was only about 50 cm from surface measured with the Secchidisk with total suspended solid (TTS) reaching 182-567 mg L-1. The surface water temperature was recorded daily and ranged from 28.5 to 29°C throughout the trials. The trapping experiments were set up as follows:
Experiment 1: Five modified collapsible traps were constructed with
the same dimensions and materials (iron rod frame 800x600x280 mm, covered with
poly-ethylene netting and with two open slackness nylon monofilaments 23 mm
mesh size at each end).
|| The sampling area of Barito river in Banjarmasin, south Kalimantan
Each of the five traps was assigned with one color of LED lamps (Torpedo flasher,
Yuli Co.Ltd. China) or with incandescent lamps (YL/YS-1, Yuli Co.Ltd. China).
Each color (blue, green, yellow, red and extra white) was tested and repeated
three times with the same treatments. The objective of this experiment was to
evaluate the effect of different color/intensity of lamps on number of catches.
Experiment 2: Four traps of different sizes and shapes were comprising: (1) box-shape trap: PVC rod frame 890x670x220 mm with black 150 mm hexagonal mesh wire (16 gauge PVC-coated wires). Ten entry funnels located on each side of the trap with a 500 mm inside ring entrance; (2) bamboo-stage trap: 420 mm high by 300 mm wide with an aperture of 15 mm apart and 25 mm wide opening; (3) wire-stage traps: 450 mm high by 400 mm wide, with 12 mm square mesh wire and 30 mm wide opening and (4) minnow nets: 600 mm long by 300 mm wide, covered with 12 mm polyethylene netting and 70 mm inside ring entrance. Each of the four traps was associated with single white LEDs or ordinary incandescent of squid fishing lamps (Yo-zuri Co.Ltd. Japan) following the same procedure. The objective of this experiment was to examine whether size and construction of the light traps affect number of catches.
The light traps were randomly laid on the bottom of the river and illumination began 1 h before sunset and picked up the next morning. On each sampling date, each trap was separated from the other traps approximately 5 m to minimize any significant light contamination between traps. Each trap of the groups was repeatedly used for three night operations (a total of 54 trials). The soaking-time for the traps varied from 14-16 h. After collection, the catches were identified for species and sex and measured for carapace length, total length and weight.
For the statistical analysis, the Mann-Whitney test was used to see which catch
differed between two lamps or between individual sexes of the same species.
The Kruskal-Wallis test was applied to see if there were significant differences
in the total catch between the five traps in the Experiment 1 or between the
four traps in the Experiment 2. The Multiple Comparison test was performed to
see which catch differed significantly among the traps (Conover,
A total of 231 shrimps and 34 fish were caught across all treatments during the 6-night sampling periods (Table 1). There was a large variability in numbers between shrimp and fish collected. The shrimp catch was dominated by the longarms shrimp Macrobrachium sp. (99.6%) with size ranges of 24-85 mm total length (Fig. 2) and the lowest number was the giant freshwater shrimp M. rossenbergii (0.4%). Size-frequencies of the Macrobrachium sp. collected indicating that the light traps sampled juveniles and adults exclusively. A total of 85 males and 145 females including 55 egg-bearing females (38-74 mm TL) were collected in this study. The fish catch composed of Oxyeoleotris urophthalmus (38.2%), Glossogobius giuris (20.6%), Oxyeoleotris marmorata (17.6%), Flounder pleuronectes (8.8%), Puntioplites bulu (5.9%), Mastacembelus erythrotaenia (5.9%) and Osteochilus melanopleura (2.9%) with size ranges varied from 60-310 mm total length.
In the experiment 1, the LED lamps or colored incandescent lamps were associated
with the same collapsible traps. Color or relative intensity of light had strong
effects on numbers of shrimp and fish collected. The LED traps collected Macrobrachium
sp. were significantly higher than that of colored incandescent ones (Mann-Whitney
test, p<0.05) (Table 2). There was no difference in the
total number of Macrobrachium sp. among LED traps used (Kruskal-Wallis
test, p>0.05). It was identified that male has chelae 1.5 times longer than
its total length and 1.3 times longer than female of the same size. The males
chelae collected in the light traps varied from 17-129 mm long. However, no
significant different in the sizes between males and females collected (Mann-Whitney
test, p>0.05) (Table 3). For colored incandescent lamps,
yellow appeared to be the strongest attractor for Macrobrachium sp. among
the colors (Multiple Comparison test, p<0.05). Then green was significantly
different from blue, red and white (Multiple Comparison test, p<0.05). It
was found that the number of female was significantly higher than that of male
(Mann-Whitney test, p<0.05) regardless typical lamps used (Table
||Pictures of Macrobrachium sp. collected from Barito
||Total number, size range of Carapace Length (CL), Total Length
(TL) and weight of shrimp and fish captured from the Barito River using
various light traps over 6-night sampling periods
||Total numbers of catch collected in the collapsible traps
using LEDs and incandescent lamps in the experiment 1
|B: Blue, G: Green, Y: Yellow, R: Red, W: White
||Size ranges and numbers of individual sexes of Macrobrachium
sp. caught by the collapsible traps with different colors of lamps
in the experiment 1
|The bracketed numbers indicate the egg-bearing females
||Total numbers of catch collected in the box-shape, wire-stage,
bamboo-stage and minnow net traps by mean of white LED and ordinary incandescent
lamps in the experiment 2
|A: Box-shape trap, B: Wire-stage trap, C: Bamboo-stage trap,
D: Minnow nets
||Size ranges and numbers of individual sexes of Macrobrachium
sp. that collected in four different traps using white LED and ordinary
incandescent lamps in the experiment 2
|The bracketed numbers indicate the egg-bearing females
Male to female sex ratio of Macrobrachium sp. was 1.0:2.6 for LED lamps
and 1.0:1.6 for colored incandescent lamps. Both types of lamps were generally
attractive enough to allure shrimp and fish into the traps in the river.
In the Experiment 2, performance of box-shape trap, wire-stage trap, bamboo-stage
trap and minnow nets were investigated by mean of white LED and ordinary incandescent
lamps. There were significant differences in the total catch between the four
traps (Kruskal-Wallis test, p<0.05) and the Minnow nets collected significantly
number of catch compared to other three traps (Multiple Comparison test, p<0.05)
(Table 4). There was no significant difference between the
collecting rates of the box-shape and wire-stage traps (Mann-Whitney test, p>0.05)
but both traps caught more catch than bamboo-stage trap). More males than females
were found in ordinary incandescent traps (Mann-Whitney test, p<0.05) (Table
5). The size and design of the light traps that affected number of catch
were also evaluated in this study.
The present study clearly demonstrates that light traps can be used for harvesting
shrimp and fish from the Barito Rivers without any bait. Data on phototactic
response revealed that all colors or relative intensity of lights utilized in
this study had strong effects on number of catches collected where LED traps
appear to be more effective than incandescent ones. Although individual species
collected in different numbers using specific colors or intensities of light,
but insufficient support for a taxonomic color bias in the LED traps (Table
2). Most species seemed to respond similarly to the LED traps, except Macrobrachium
sp. which to be found more attractive to the yellow incandescent trap. The
efficacy of yellow light may be due to its wavebands not being attenuated under
water as rapidly as blue or red wavebands (Wetzel, 2001).
Yellow light also emits a greater intensity of light over a longer time than
other colors tested which may have increased the effectiveness of yellow trap.
Macrobrachium sp. displayed stronger phototactic behaviour than M.
rosenbergii (de Man, 1879) of the same genus in the river. From the results
of phototactic data analysis, Macrobrachium sp. could be determined as
a multichromatic species because it shows photopositive for all colors. Female
dominated in catch during the whole sampling period (total sex ratio of male
to female was 1.0:1.7). About 40% of total female collected in the light traps
was egg-bearing females ranged from 38-71 mm total length (Table
3). Females are usually inactive during the breeding season, while females
carrying the eggs still reacted positively to the light traps. It was also clear
from our work with the American crayfish Procambarus clarkii (Ahmadi
et al., 2008). However, this result contrary to the observations
of many studies (Richards et al., 1996; Holdich,
2002; Faller et al., 2006) which reported
that egg-bearing females are less active than males. They become more active
after releasing the young and preparing for mating.
Macrobrachium sp. in this river does not seem to have been scientifically
described yet (proposed name Macrobrachium baritoense). It morphologically
resembles with M. australiense (Holthuis, 1950) from Australia River
(Dimmock et al., 2004). To differentiate between
two species, cheliped traits were considered as they show a high level of developmental
variation (Short, 2000). It was clear from our findings
that the males chelae of Macrobrachium sp. (112 mm) has twice longer
than that of M. australiense (51 mm) of the same size (72 mm) reported
by Short (2000). The size range of Macrobrachium sp.
(28-83 mm) collected from this study was also similar to M. hainanense
(Parisi, 1919) in Chinase streams (Mantel and Dudgeon, 2004),
M. nippponense (de Haan, 1849) in Japanese aquacultures (New,
2005) and M. lamarrei (H. Milne-Edward, 1937) in Nepal freshwater
ponds and rivers (Sharma and Subba, 2005). However,
it was considerably smaller than others Macrobrachium species in the
same genus such as M. ohione (Smith, 1874) in the Upper Mississippi
River (Conaway and Hrabik, 1997), M. amazonicum
(Heller, 1862) in Amazon River (Bialetzki et al.,
1997), M. rosenbergii (de Man, 1879) in Thailand River (Sripatrprasite
and Lin, 2003), M. heterochirus (Wiegmann, 1836) and M. carcinus
(Linnaeus, 1758) in Mexico River (Mejia-Ortizi et al.,
2004). This study also suggests investigating the spawning season, distribution,
growth and production of Macrobrachium sp. in the Barito River.
The results also showed that traps of different sizes and shapes but containing
the same amount of attractant had effect on the numbers caught. The minnow nets
collected almost 50% of total catch compared to other three traps regardless
LED lamps and incandescent ones (Table 4). The least effective
was a traditional bamboo-stage trap where shrimp/fish that went inside can easily
find its way out again through bamboo-aperture itself (approx. 15 mm wide apart).
This implies that to expect more catch by light traps, the trap designs should
be modified. Sheaves (1995) asserted that the trap size
can affect catch rates by influencing the density of animals in the trap. Beside
the above problem, we found another reason why much less catches were sampled
from Experiment 2, this because of the optical characteristic of squid fishing
lamp that might be more suitably used in clear water (e.g., sea, coastal) rather
than in turbid water.
Another criticism is clear from this study that the catch is not always found
to be negatively correlated with turbidity which results may differ from other
works (Meekan et al., 2000; Lindquist
and Shaw, 2005) in term of species target, size and design of traps, light
sources and environmental condition. It is commonly understood that efficiency
of light traps in clear water was greater than that of turbid water. The light
attenuation is gradually declining with increasing of turbidity that would reduce
the effective sampling radius of the traps (Lindquist and
Shaw, 2005). It is interesting to conduct trapping experiments under highly
turbid environment, since visibility of the water was only about 50 cm observed
from surface with the help of the Secchidisk. Such condition may cause short
sighting distance for the animals to access the light during nighttime. However,
we have proved scientifically that light traps used in this study were able
to entice shrimp and fish entered the traps even using 0.06 W LED with 3-volt
From this finding, we intend to enlarge our future phototactic study in Barito River to examine the light traps with specific designs associated with various colors or light intensities at different turbidity levels or under richly vegetated habitat. This indicating more detailed data will be needed to analyze the factors leading to this variation. Installation of underwater instruments (e.g., video-camera and digital light-meter) would also be helpful to investigate interaction between the animals and light traps as well as security risk.
We could not standardize catches to the Catch Per Unit of Effort (CPUE) for all treatments because the length of time that the lights were operational was variable and dependent on the type of light devices and variance in battery life. For future applications, the use of LEDs is considered more advantage than incandescent bulbs, because they are more energy efficient, more colors available and more durable. Creating a waterproof electrical light source at reasonable cost is the main challenge for designing light traps.
The author is grateful to Mr. Ahmad Rizani and Mrs. Tien Zubaidah for their
help during the trapping experiments and measurement work as well as students
of Faculty of Fisheries, Lambung Mangkurat, Banjarbaru, South Kalimantan for
their assistance with the laboratory work. We would also like to thank Prof.
Dr. Gunzo Kawamura my former Supervisor from ex-Kagoshima University for his
inspiration in my phototactic study.
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