Fish colonization of the artificial reef at Gusung Batu Lampe Muara Badak, Kutai Kartanegara, East Kalimantan, Indonesia: a preliminary study

Study parameters and location

An underwater line transect and fish visual census (FVC) were applied in this survey. FVC method is commonly used at site (Lim, 2017) and line transect limits the observation area to only 200 m² (20 m long and 10 m wide, 5 m to the right and 5 m to the left), measured using a 50 m roll meter. The distance of the observation area was around 5 km from the coast at the coordinate of 0° 13’02.1” S 117° 29’35.1” E and a 40 HP speed boat was used to transport divers to the site. The artificial reef structure comprised 34 units of tetrahedral concrete block, sizing 60 cm x 60 cm at base, 60 cm high and 35 cm x 35 cm wide on top, with four holes in each block, were placed in a row. Two SCUBA divers descended to the bottom; one ensured the safety of the divers and the other one took photographs while counting the number of fish. Fish photographs were realized with Action Kogan 4K and Nikon AW 130 underwater cameras. These cameras were also used to record the vicinity condition such as a unit of reef, and a GPS device (Garmin) was used to determine the observation site. All observational data were recorded using underwater diving slates. Observation took place for only 30 to 45 minutes in the morning at 09:00, in the early afternoon at 13:00 and at the late afternoon at 17:00, with the total duration of 90 to 135 minutes for one survey. Surveys were performed four times: in November and December 2016, and in January and July 2017.

Data capture

Recording and taking photographs of fish started about 20 minutes after transect was laid to provide time for fish to react to the natural habitat. Fish species identification was conducted with reference to Allen (2000); Anam & Mostarda (2012); Masuda et al. (1975); Peristiwadi (2006).

Water physical parameters such as transparency, salinity and temperature were measured with water quality meter AZ 8603 (Shenzhen Hengkaituo Sci-Tech Co., Ltd, Guandong, China). Water velocity was assessed by drifting on the surface a small buoy for 10 m distance and noting the time to pass was using a stopwatch. Water depth was measured with a measuring rope.

Data analysis

Palaeontological Statistics version 3.20 (Hammer et al., 2001) was used to analyze the diversity indices, namely dominance, Shannon’s H, evenness, and Margalef species richness index. Bray–Curtis multivariate statistics, which is known to be more effective than other analytical tools (Kurt & Merlyn, 1998) such as Euclidean, Morisita, Mahalanobis, and Jaccard statistics, was applied to analyze the similarity of fish size colonization among observation times. Fish density (individual/m²) was calculated manually.

Fish community

Taxonomically, 38 species belonging to 26 genera and 16 families were observed during surveys. A total of 25 species and 12 families were observed in the first survey; 22 species and 9 families in the second survey; 26 species and 11 families in the third survey; and 23 species and 13 families in the last survey (Table 1 and Table 2). All of the fish were small-bodied. In each survey, the two families Pomacentridae and Labridae were families with the most common and adaptable species as well as the most abundant in individual number, followed by the Chaetodontidae and Acanthuridae families. The remaining 12 families were only represented by one or two species. However, the four families Chaetodontidae, Siganidae, Caesionidae and Nemipteridae were present in every survey. Some families were only present in single surveys. The fish species observed at the fourth survey to represent the fish colonization of the artificial reef at Gosong Batu Lampe are shown in Figure 2.

Figure 1. Map showing the study location of Gusung Batu Lampe in Pangempang water, Muara Badak.

Figure 2. Fish species associated with the artificial reef at Gusung Batu Lampe taken from the fourth survey.

Mallet et al. (2016) examined reef fish assemblages during daylight hours, 10 times a day for 34 consecutive days in a branching coral and they discovered fish abundance and taxa richness were greater in the early morning, in which the most frequent observed families was Pomacentridae and Labridae (in 100% and 99.6% of cases, respectively). In our study these two families were also encountered in every survey, and were the most specious and populous families, followed by Acanthuridae and Chaetodontidae families. Honda et al. (2013) reported that the most dominant families on the basis of species number in coral reefs were Labridae, Pomacentridae and Chaetodontidae. There were nine families identified in all surveys, but with only one species in each family, and according to Hernández-Velasco et al. (2016) the families distributed in tropical regions inhabit shallow coral reefs. Chaetodon kleinii and two other species of Chaetodontidae identified in our study indicated that Gusung Batu Lampe has potentiality to attract more coral reef fish. Chaetodon sp. are known to be obligate corallivores, which feed entirely on coral polyps (Kulbicki et al., 2011; Yusuf & Ali, 2004), and rely on reefs for breeding, nursing and shelter (Muhammad et al., 2017). In term of single species, Caesio teres, of the family Caesionidae (Fusilier), was the most abundant species and fed primarily on plankton; this species is included commercially as an important food fish. Some species of this family are distributed widely in mid-water over reefs (Bawole et al., 2014) and are utilized as bait fish to catch Tuna (Rajasuriya, 2014). Acanthurus, of the family Acanthuridae, commonly known as surgeonfish, was encountered in this study as the third major group. This group feeds upon algae.

Fish colonization size

Based on the Bray–Curtis index, the number of fish at 09:00 in the morning and at 13:00 in the early afternoon was 95.0% similar, but declining less to 80.0% at 17:00 in the late afternoon (Table 3). This phenomenon of retreat of coral fish in the late afternoon could be an effect of light intensity (Rickel & Genin, 2005). Light may influence and increase water temperature (Mcleod et al., 2013), and such condition could affect the performance of coral reef fish, said otherwise they which tend to harbor or hide in reef holes and unseen (Suyatna et al., 2016). Likewise, the number of taxa between two observation times was 99.0% similar, but the similarity in the late afternoon was only 91.0%.

Fish density in a unit area (individual/m²) increased from the first to the last survey, from 1/4.444 m² to 1/1.481 m² (Table 4). This indicates that the reef at Gusung Batu Lampe potentially provide a valuable area forcoral reef fish population since the availability of refuge sites of reefs may increase fish number (Grossman et al., 1997), and reef size did not significantly affect the density of colonists (Borntrager & Farrell, 1992).

Fish group structure

The diversity index was applied to describe regarding of how many different species are present over the surveys among the observation times. This study revealed that the number of colonists, species richness and species diversity was highest in at 09:00 in the morning and at 13:00 in the afternoon, and the highest species richness arose in the 3rd survey, particularly at 13:00 (Table 5). The other diversity indices showed a different population sizes of the colonists during this study.

Some relevant water quality parameters measured at the location showed favorable water conditions for fish to live (Table 6). This is notable, since water quality factors such as current velocity may affect food intake (Belal, 2015), water transparency determines underwater visibility and fish assemblage (Enrique de Melo et al., 2009), and temperature and salinity may decrease species richness and fish abundance (Brucet et al., 2012). Fish can live in various places, but they often occupy a particular place and certain depth (Costa et al., 2013).