Abundance and Distribution of Freshwater Eels in Pangi River, Maitum, Sarangani Province

The fishing for freshwater eels, along with environmental pollution and other human impacts, have all contributed to a significant decline in eel numbers over the last 25-30 years. Total volume of glass eels collected on an annual basis is around 150 tonnes which satisfies the current aquaculture needs of approximately 100 tonnes/year with the excess going to human consumption in Spain [1]. Many people are involved in the eel collection, transportation and distribution, from glass eel fishers to the eel farmer and processor [1].


Introduction
Eel is the common name for any fish of the 10 families constituting the Order Anguilliformes, it is characterized by a long snakelike body covered with minute scales embedded in the skin. Eels lack the hind parts of fins, adapting them for wriggling in the mud and through the crevices of reefs and rocky stones.
According to Schrank in year 1798, freshwater eels are catadromous, that spawns in tropical ocean waters, and has a peculiar leptocephalus larval stage that is unique to elopomorph fish. They constitute a single Genus, Anguilla.
The fishing for freshwater eels, along with environmental pollution and other human impacts, have all contributed to a significant decline in eel numbers over the last 25-30 years. Total volume of glass eels collected on an annual basis is around 150 tonnes which satisfies the current aquaculture needs of approximately 100 tonnes/year with the excess going to human consumption in Spain [1]. Many people are involved in the eel collection, transportation and distribution, from glass eel fishers to the eel farmer and processor [1].
In the Philippines, freshwater eels have different populations scattered in various regions in country in which they are considered important food fish especially to the indigenous people [2]. There has been documented on the evolutionary history and phylogenetic studies of the eels in the country and by traditional molecular methods, where this fishes are quite abundant and geographically near to their spawning ground [2]. Knowledge and background of the natural life history and specification are the basis for sound fishery management or aquaculture industry development of eels.
The study provides baseline information on the abundance and distribution of the freshwater eels that present in Pangi River Maitum, Sarangani Province. This serves as basis for action plan of the Local and National Government Unit for protection and conservation of Freshwater Eels in the area [3][4][5][6][7][8][9][10].

Sampling area and sampling stations
Pangi River can be found at Brgy. Pangi, Maitum, Sarangani Province ( Figure 1). The sampling stations stretch from 50 to 100 meters which is further subdivided into tree substations, where two (2) is designated at both sides and 1 substation at the center.
There are two (2) types of substrates observed in the area: sandy and rocky. The mouth of the river or the station 1 had its sandy bottom while the station 2 and 3 had its rocky bottom.
The Sampling Stations will be as follows: The first substation is placed on the mouth of the river which expands from 31 meters at low tide to 100 meters up at high tide. The second station will be 50 meters away from the mouth of the river, the third station is 50 meters away from the second station.

Sampling methods and sampling frequency
Sampling is done by collecting the anguillid eels that is trapped using net traps as collecting gear on the 1 st , 2 nd station and 3 rd station. This is made of 8 meters mosquito net, rope and bamboo sticks. A set of three net traps are set together in three stations to intercept as many as possible eels over a wide area. The net traps are set in the afternoon and timed by the incoming high tide and get the trapped glass eels using the (sigpaw) Scoop net.
Sampling is done every full moon and new moon of the month to observe the tidal fluctuation in collecting freshwater eels.

Data collection
The information that are noted and gathered during sampling is the following: The eels that will be collected will be identified through its morphological characteristics.
Determining the species using morphological characteristics ( Figure 2).
The following data are computed using the information gathered during sampling: Catch per unit effort The information on biomass of animals caught and length of fishing are used to compute for the Catch per unit effort using the formula:

Total weight of catch CPUE g hour
No of hour in catching = .

Total no of particular species Abundance Index
Total no of all species = × .

No of sampling the particular species found Frequency Index
Total no of sampling = × Dominance Index = Abundance Index + Frequency Index The Collected anguillid eels were fixed in 95% ethanol alcohol just after weighing and the specimens were counted.

Results and Discussion
Results showed that there are two types of Freshwater eels which can be found on Pangi River, Maitum Sarangani Province those are the Anguilla marmorata species and the Anguilla bicolor pacifica. A total of 4,262 individuals were collected and a total Catch per unit effort of 65.98 g/hr for the duration of five (5)  The largest catches of the freshwater eels were in the month of November during the New Moon phase and with the zero catches during the month of December and January Full moon. It is also showed that on the station 2, substation 1 right side near the bank is more applicable area on setting the trap than station 1 and station 3, since the water depth and current is more severe on the area of Station In terms of abundance A. marmorata has an average of 96.62%, while the A. bicolor pacifica has an average of 3.26%. This could be attributed to their habitat and migration pathways as mentioned earlier.
In terms of frequency, A. marmorata has an average of 100%, while A. bicolor pacifica has an average of 42.86%.
In terms of Dominance, A. marmorata has an average of 196.62, while A. bicolor pacifica has an average of 46.12. Table 1 represents the abundance, frequency and dominance of the two species that has been collected on the study as general. 1 and Station 3. As well as visual observation indicated that glass eels were most abundant on the side of the river bank. The trap which is placed in station 1 which is found on the mouth of the river had been destroyed by the waves due to the strong winds and drifted trees during sampling, and for the trap which is set on the center of the station 1 is not comfortable for the collector and trap due to the high level of the water that occur on the center of the river during high tide it reaches 10 to 20 feet depth at the center of the river. While on station 3 it is hard to set the trap since station 3 possesses larger rocks and also not suitable for the traps due to the strong current coming from the upstream of the river, it gives damage to the net trap. Data also shows that freshwater eels is more abundant during the new moon phase than the full moon phase, due to the moon light which is present every full moon, freshwater eels is more seen during dark hours such as new moon, glass eels prefer to migrate during those times, suggesting that the lunar phase has a strong effect on inshore migration mechanism of glass eel at the mouth of the Pangi River, there were 4,249 individuals collected caught during the new moon samples obtained in five (5) months (from 2014-2015) used for comparison during the full moon phase which are 13 individuals collected during those times. Weather condition also had been noted and observed during the sampling period (Figures 4 and 5).
Temperature is also a factor that affects the migration of Freshwater Eels they are more likely to stay on colder part of the river which is more observed on the study, they prefer to migrate upstream. Other study also who has been conducted on other countries said that temperature affects the survival of the Freshwater eels ( Figure 6).

Abundance, frequency, and dominance of freshwater eels in Pangi river
The following Figures 7-9 showed that Anguilla marmorata is the

Conclusion and Recommendation
The Abundance and Distribution of Freshwater Eels in the area of Pangi River, Maitum Sarangani Province revealed that the river had its source for wild eels especially the Anguilla marmorata species that suits for culturing process in the near future, since the river possesses a rocky substrate which is good for the habitat of the said species. In conclusion the findings of this study confirm that there are two species which are present on the Pangi River which is the Anguilla marmorata and Anguilla bicolor pacifica, the good quality of the water and maintaining its cleanliness is another key factor why those wild eels keep on migrating on the area, due also to the abundance of other food that can be found on the area. Studies in the laboratory or with different types of sampling gear fished in the Pangi River itself will be helpful to further examine the abundance and distribution of freshwater eels in Pangi River, Maitum Sarangani Province.