The authors have declared that no competing interests exist.
The samples of flatfishes were collected along the Mon State from July to December 2017 including Mawlamyine, Kyaikkhami, Setse, Zee-Phyu-Thaung Belugyun island, Paung and Thaton. The total 21 species of flatfishes were recorded in Mon State. Moreover, the relative abundance, diversity and similarity were conducted using Simpson Index, Shannon index and Jacquard’s index etc. According to the present study, the Cynoglossidae was the most dominant family and the most dominant species was
Pleuronectiformes were first named in 1758 by Linnaeus;
Flatfishes are one of the important components in several demersal communities around the world. Flatfishes are also important predators in many demersal communities. They may serve as an important link between demersal production and human consumption
The flatfishes are one of the most important economic groups of marine fishes in Myanmar. From the commercial point of view, all species are locally known as “Khway-Shar”. It yields 2277.35 tones and by percentage, it had 4.41 % of the Myanmar marine fish landings in Yangon, the business city of Myanmar for 2005
The present study area, called Mon state is an administrative division of Myanmar. It is sandwiched between Kayin State in the east, the Andaman Sea in the west, Bago Region in the north and Tanintharyi Region in the south. The land area is 12, 155 km2. The state of capital is Mawlamyine. Bordering Bago Division in the south of Sittaung river mouth, Kayin state in the east, Thailand and Taninthayi division in the south and Andaman Sea and Gulf of Mottama in the west, Mon state is situated between Latitudes 14° 52′ and 17° 32′ N and Longitudes 96° 51′ and 98° 13′ E.
Numerous studies have been done on the distribution, abundance and fisheries biology of flatfish in many different places around the world
1. Mawlamyine (Lat. 16° 29′ N, Long. 97° 37′ E),
2. Kyaikkhami (Lat. 16° 03′ N, Long. 97° 33′ E),
3. Setse (Lat. 15° 56′ N, Long. 97° 37′ E),
4. Zee-Phyu-Thaung (Lat. 15° 15′ N, Long. 98° o′ E),
5. Belugyun island (Lat. 16° 12' N and 16° 32' N and Long. 79° 52' and 79° 35' E),
6. Paung (Lat. 16° 37' N and 97° 34'E) and
7. Thaton (Lat. 17° 00' N and 97° 22'E) (
From July to December 2017, the samples of flatfish species were randomly collected on monthly basis, at seven stations along the Mon State, not only from fishing boats but also from the fishery markets. The fresh samples were put in the bags and containers. For environmental parameters, the water samples in each station were measured their temperature (
Study areas | Parameters | July | August | September | October | November | December | |
1 | Mawlamyine | TemperatureᵒC | 30.0 | 29.5 | 29.0 | 28.0 | 27.0 | 26.5 |
Salinity ‰ | 25.5 | 25.0 | 23.5 | 26.5 | 23.5 | 25.5 | ||
pH | 7.2 | 7.2 | 7.4 | 7.4 | 7.4 | 7.6 | ||
2 | Kyaikkhami | TemperatureᵒC | 29.5 | 27.5 | 28.5 | 28.0 | 27.0 | 26.5 |
Salinity ‰ | 28.0 | 24.5 | 28.0 | 26.5 | 27.0 | 25.5 | ||
pH | 7.4 | 7.2 | 7.4 | 7.6 | 7.6 | 7.8 | ||
3 | Setse | TemperatureᵒC | 29.5 | 28.0 | 28.0 | 27.5 | 27.0 | 26.5 |
Salinity ‰ | 30.5 | 26.0 | 26.5 | 27.0 | 27.5 | 27.0 | ||
pH | 7.6 | 7.2 | 7.4 | 7.6 | 7.8 | 7.6 | ||
4 | Zee-Phyu-Thaung | TemperatureᵒC | 30.0 | 28.5 | 28.0 | 27.5 | 27.5 | 26.0 |
Salinity ‰ | 30.5 | 27.5 | 29.5 | 30.0 | 30.5 | 29.5 | ||
pH | 7.8 | 7.6 | 7.8 | 7.8 | 8.0 | 7.8 | ||
5 | Belugyun island | TemperatureᵒC | 29.0 | 27.5 | 28.0 | 28.5 | 27.5 | 26.0 |
Salinity ‰ | 26.5 | 25.0 | 28.0 | 27.0 | 28.0 | 25.0 | ||
pH | 7.4 | 7.4 | 7.6 | 7.8 | 7.8 | 8.0 | ||
6 | Paung | TemperatureᵒC | 30.0 | 27.5 | 28.5 | 27.5 | 26.5 | 26.0 |
Salinity ‰ | 26.0 | 25.0 | 26.0 | 27.0 | 27.5 | 26.0 | ||
pH | 7.4 | 7.4 | 7.4 | 7.6 | 7.8 | 7.8 | ||
7 | Thaton | TemperatureᵒC | 30.0 | 28.5 | 28.0 | 28.0 | 27.5 | 26.5 |
Salinity ‰ | 25.5 | 25.0 | 25.5 | 25.0 | 26.5 | 25.5 | ||
pH | 7.4 | 7.2 | 7.2 | 7.4 | 7.2 | 7.6 |
The relative abundance (percentage of catch) of fish across different sites was calculated. RA of individual species was calculated by the following formula.
Number of samples of particular species x 100 Total number of sample
The species richness indices were calculated using Simpson Index (D).
Simpson Index (D) =
In the Simpson index, D is richness, p is the proportion (n/N) of individuals of one particular species found (n) divided by the total number of individuals found (N), Σ is still the sum of the calculations, and s is the number of species.
Evenness was calculated by the following formula.
J′ = H/lnS
In the formula, J′ is evenness, S= the number of species, H is richness.
The species diversity indices were calculated using Shannon index.
Shannon index (H) =
In the Shannon index, H is diversity, p is the proportion (n/N) of individuals of one particular species found (n) divided by the total number of individuals found (N), ln is the natural log, Σ is the sum of the calculations, and s is the number of species.
Similarity of the species in all sampling station was calculated using Jacquard’s index:
Where
A total of 5 families, including 21 species of flatfishes were recorded in Mon State. The Psettodidae which included 1 genus and 1 species, the Paralichthyidae, which included 1 genus and 2 species, the Bothidae which included 1 genus and 1 species, the Soleidae which included 4 genera and 7 species, the Cynoglossidae which included 2 genera and 10 species were found along the Mon state in this study.
In
Sr. No | Scientific Name | Sampling areas | Type of gear | ||||||||||
Mawlamyine | Kyaikkhami | Setse | Zee-Phyu-Thaung | Belugyun island | Paung | Thaton | Bag net | Gill net | Cast net | Trawl net | Drift net | ||
1. | Psettodes erumei | - | - | - | + | - | - | - | - | - | - | + | + |
2. | Pseudorhombus arsius | - | + | - | + | - | - | - | - | - | + | + | |
3. | P. dupliciocellatus | - | - | - | + | - | - | - | - | - | - | + | + |
4. | Engyprosopongrandisquama | - | - | + | - | - | - | - | - | - | - | + | + |
5. | Heteromycteris oculus | - | + | - | - | - | - | - | - | - | - | + | + |
6. | Synapture albomaculata | + | - | - | - | - | - | - | - | - | - | + | - |
7. | Zebraiszebra | - | - | + | - | - | - | - | + | + | + | + | + |
8. | Z.synapturoides | - | - | + | - | - | - | - | + | + | + | + | + |
9. | Euryglossa harmandi | + | - | - | - | - | + | - | + | - | + | - | - |
10. | E. orientalis | + | - | - | - | + | + | + | + | - | + | - | - |
11. | E. panoides | + | - | - | - | + | + | - | + | - | - | ||
12 | Paraplagusi bilineata | + | + | + | _ | + | _ | _ | + | + | + | + | + |
13. | P. ablochii | - | - | + | - | - | - | - | + | + | + | + | + |
14. | Cynoglossus lida | + | - | - | - | - | + | - | + | + | + | - | - |
15. | C. Bengalensis | + | - | - | - | - | + | + | + | + | + | - | - |
16. | C. semifasciatus | + | - | - | - | - | + | + | + | + | + | - | - |
17. | C.cynoglossus | + | - | - | - | + | + | - | + | + | + | - | - |
18. | C. carpenteri | - | + | + | + | - | - | - | - | - | - | + | + |
19. | C. lingua | + | + | + | + | - | + | - | - | - | - | + | + |
20 | C.macrolepidotus | + | + | + | + | - | - | - | - | - | - | + | + |
21. | C.arel | + | + | + | + | + | + | + | - | - | - | + | + |
Total | 12 | 7 | 9 | 7 | 4 | 9 | 4 |
In addition, flatfishes are caught mostly using bottom trawl nets by fishermen in all stations as the flatfishes are close to the bottom and swim by undulation of the body. Besides bag nets, gill nets, cast nets and drift nets are used for catching flatfishes in some stations. Soleidae appears to be caught mostly by bag nets and cast nets and Psettodidae, Paralichthyidae and Bothidae appear to be caught mostly by bottom trawl nets in Mon State.
Due to sampling limits in this study, potential bias may be an issue, especially as large variations in catch were observed among vessels. However, since our samples were taken randomly from different catches deposited in the market, it was believed such bias was minimized. it cannot be excluded that the possibility that rare flatfish species were under-represented in the study (in terms of their number and abundance) because many of these species are small in size and deposited as trash fish and so could not be examined completely.
Of the total sample number 378 of 21 species in seven stations, samples were obtained the total number of 128 in Mawlamyine, 79 in Kyaikkhami, 29 in Setse, 53 in Zee-Phyu-Thaung, 19 in Belugyun, 48 in Paung and 19 in Thaton (
Family | Scientific name | No. of specimens | ||||||||
Sampling areas | Mawlamyine | Kyaikkhami | Setse | Zee-Phyu-Thaung | Belugyun island | Paung | Thaton | Total | ||
Psettodidae |
|
0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | |
Paralichthyidae |
|
0 | 1 | 0 | 1 | 0 | 0 | 0 | 2 | |
|
0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | ||
Bothidae |
|
0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | |
Soleidae |
|
2 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | |
|
0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | ||
|
0 | 0 | 2 | 0 | 0 | 0 | 0 | 2 | ||
|
0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | ||
|
7 | 0 | 0 | 0 | 0 | 3 | 0 | 10 | ||
|
6 | 0 | 0 | 0 | 2 | 5 | 2 | 15 | ||
|
1 | 0 | 0 | 0 | 1 | 0 | 1 | 3 | ||
|
1 | 1 | 3 | 0 | 1 | 0 | 0 | 6 | ||
0 | 0 | 4 | 0 | 0 | 0 | 0 | 4 | |||
|
3 | 0 | 0 | 0 | 0 | 2 | 0 | 5 | ||
|
37 | 0 | 0 | 0 | 0 | 18 | 15 | 75 | ||
Cynoglossidae |
|
20 | 0 | 0 | 0 | 0 | 10 | 0 | 31 | |
|
32 | 0 | 0 | 0 | 6 | 10 | 0 | 48 | ||
|
0 | 2 | 1 | 1 | 0 | 0 | 0 | 4 | ||
|
1 | 1 | 1 | 4 | 0 | 0 | 1 | 8 | ||
|
1 | 1 | 1 | 1 | 0 | 0 | 0 | 4 | ||
|
17 | 71 | 15 | 45 | 9 | 0 | 0 | 154 | ||
Total | 128 | 79 | 29 | 53 | 19 | 48 | 19 | 378 |
The relative abundance of number of species of Mawlamyine is relatively the highest (34%) of all stations. The relative abundance of number of species of Kyaikkhami (21%) is the higher as compared to Zee-Phyu-Thaung. In the same way, the relative abundance of number of species of Paung (12%) is higher than Setse (7%) and the relative abundance of number of species of Belugyun and Thaton are the same with 5% respectively (
Of the total sample number 378 of 21 species, samples were obtained the total number of 36 in July, 41 in August, 75 in September, 86 in October, 88 in November and 52 in December (
In the
Family | Scientific name | No. of specimens | Total | ||||||
Month | July | August | September | October | November | December | |||
Psettodidae |
|
0 | 1 | 0 | 0 | 0 | 0 | 1 | |
Paralichthyidae |
|
0 | 0 | 0 | 1 | 0 | 1 | 2 | |
|
0 | 0 | 0 | 0 | 0 | 1 | 1 | ||
Bothidae |
|
1 | 0 | 0 | 0 | 0 | 0 | 1 | |
Soleidae |
|
0 | 0 | 1 | 0 | 1 | 0 | 2 | |
|
0 | 0 | 0 | 0 | 0 | 1 | 1 | ||
|
2 | 0 | 0 | 0 | 0 | 0 | 2 | ||
|
0 | 0 | 1 | 0 | 0 | 0 | 1 | ||
|
0 | 1 | 0 | 3 | 4 | 2 | 10 | ||
|
0 | 6 | 4 | 0 | 4 | 1 | 15 | ||
|
0 | 0 | 1 | 0 | 2 | 0 | 3 | ||
|
0 | 3 | 2 | 0 | 1 | 0 | 6 | ||
2 | 0 | 0 | 2 | 0 | 0 | 4 | |||
|
0 | 4 | 0 | 1 | 0 | 0 | 5 | ||
|
2 | 5 | 18 | 10 | 28 | 12 | 75 | ||
Cynoglossidae |
|
4 | 1 | 5 | 10 | 5 | 6 | 31 | |
|
12 | 8 | 0 | 6 | 17 | 5 | 48 | ||
|
0 | 0 | 2 | 0 | 2 | 0 | 4 | ||
|
0 | 2 | 1 | 3 | 0 | 2 | 8 | ||
|
1 | 0 | 2 | 0 | 0 | 1 | 4 | ||
|
12 | 10 | 38 | 50 | 24 | 20 | 154 | ||
Total | 36 | 41 | 75 | 86 | 88 | 52 | 378 |
In
The similarity in species composition among the stations was analyzed using the Jaccard index for calculating the extent of similarity between pairs of data sets. Cluster analyses identified two assemblages (with a similarity of 14%), which corresponded to the group of Mawlamyine, Paung and the group of Kyaikkhami, Setse, Zee-Phyu-Thaung, Belugyun and Thaton (
In
The similarity in species composition among the months was analyzed using the Jaccard index for calculating the extent of similarity between pairs of data sets. The JI value between August and September and the value between September and November are the same as well as the highest while it is the lowest for the comparison between July and August. Cluster analyses identified two assemblages (with a similarity of 53%), which corresponded to the group of September, November, August and the group of July, December, October (
Wang
Station No | Station name | Duration | Total Sampled Fish | ||
July- Aug | Sep- Oct | Nov- Dec | |||
1. | Mawlamyine | 28 | 52 | 48 | 128 |
2. | Kyaikkhami | 18 | 38 | 23 | 79 |
3. | Setse | 5 | 11 | 13 | 29 |
4. | Zee-Phyu-Thaung | 17 | 29 | 7 | 53 |
5. | Belugyun island | 2 | 5 | 12 | 19 |
6. | Paung | 4 | 20 | 24 | 48 |
7. | Thaton | 1 | 5 | 13 | 19 |
Mon State is more adjacent to the brackish water rather than the marine areas. Therefore, it can be concluded that flatfishes are brackish water or marine species. In the present study, Cynoglossidae was the most abundant among order- Pleuronectiformes. As a result, Cynoglossidae was also one of the important exported fishes in Mon State. Moreover, Mawlamyine was the highest diversity and the most abundant as it is one major city of Myanmar and most of the fishes all around the Mon State are exported to there.
I’m deeply grateful to my dearest parents, U Kyin Aung and Daw Myint Myint San for their kind moral and financial support to reach the goal of this work.