Geoje Island
- thanks to Mr. Byun, Young-Ho.
Dae-Min Kim
I am a core participant of a Korean fish amateur group, named "Asari (어살이)" which stands for "life in harmony with fish". The group was created by Jeon, Hyung-Bae, a present president and one of my best friends, a little more than a year ago. The group does not yet have an official web site. But it is mainly based on an internet cafe (I think this type of web site can be called "online community" in English spoken in the U.S) belonging to the Daum, one of the most popular internet search-base in South Korea. Several months ago, a man whose name is Byun, Young-Ho (변영호) applied for a membership to our community. He introduced himself as a teacher in Geoje Island and a leader for an elementary school student's amateur naturalist group, Haneulgang (하늘강), that stands for "sky and river" in Korean.
The name reminds me of my old memory. One day I was a high school student, my mother introduced to me an article about a elementary school's amateur naturalist group in Geoje Island that found several natural habitats of Triops longicaudatus (긴꼬리투구새우). The group's name shown in the article was Haneulgang. Before the group, there was a little information about the Triops in South Korea. It was known as a group of extremely rare animals in wild with extremely limited distribution range only in the southeast. However, as the Haneulgang, with a young teacher and his students, tries to search every single rice-paddies of the Geoje Island for the Triops, the other naturalist groups in many different areas also began to search the local rice-paddies. As a result of this series of activity, hundreds of Triops' natural habitats have been recorded nationwidely and their ecology and reproduction have recently been well studied.
A couple of years ago, Byun Young-Ho also found an undescribed species of the Odonata in South Korea. One day when he was on his way back home from the school, he found a dragonfly he has never seen in books and took a picture of it. He asked Gwang-Soo Jeong, president of the Odonata Society of Korea, for an identification of the species. Mr. Jeong answered the species was an undescribed species in South Korea, Sympetrum fonscolombei (두점배좀잠자리). S. fonscolombei was widely distributed in the Southeast Asia and Japan but the species had not been found in the Korean Peninsula until Mr. Byun.
I will introduce Mr. Byun more in detail later on in a seperated section, probably in the "Who Have Donated to Me?". So, no more description here!
As a member of our group, Mr. Byun has asked us (me and Jeon, Hyung-Bae) many questions regarding to fish identification. One of his goals(= Haneulgang's goals) of this year is to do monitoring the freshwater-fish fauna of the Geoje Island. Thus, he has a collecting trip almost every weekend and gathers specimens that he is unable to identify. Throughout our online community, there is not anyone who is strongly responsible for doing something. However, as time goes by, I and the president Hyung-Bae became responsible for fish i.d. and Mr. Byun became responsible for question.
Mr. Byun seems to like "invitation". When he invited us (me and Jeon, Hyung-Bae), he said, "locals have to have plenty of knowledge about their areas' bio-fauna and they are responsible for inviting experts to their areas." I wondered if he really thought we are experts but I was truly appreciated. Although I am just an undergraduate student of a collge, I am always ready for giving help in case my knowledge is needed by the others. He had a plan to invite us to Sanyang River, Yeoncho River and Oepo Creek. All these streams, for sure, are filled with nice collecting spots, beautiful scenaries and fishes.
Day 1. (May 30, 2009)
It took only 4.5 hours to reach the Geoje Island from Bundang where I am living. When I was a little boy, my family had a summer vacation to the Geoje Island. At that time, we left Seoul (which is only 30 minutes away from Bundang) and it took more than 10 hours to the Geoje Island! A nice expressway, built a couple of years ago, makes such a huge difference!!
I expected temperature of the Geoje Island is much higher than that of the Bundang, but it was actually a little cooler due to the ocean. Mr. Byun said the wind from the ocean is so strong that wind-chill in winter is much more severe than visitors expected. The annual precipitation of the Geoje Island is higher than most of the inland region, with the exception of mountainous regions in Kangwon Province, Jiri mountains and Jeju Islands (Jeju Islands can not be included in the inland region though). Thus, there are many deeply developed stream systems in the island. Also, the Geoje Island is the second largest island in South Korea. Usually freshwater fish diversity of an island increases when size of the island increases and distance between the island and the nearest inland region decreases. The number of freshwater fish species occurred in the Geoje Island is actually higher than any other islands in South Korea. Dr. Ki-Chul Choi, a father of South Korea's Biology, recorded 32 species and Mr. Byun has recently recorded 39 species. Mr. Byun has not found 10 species recorded by Dr. Choi and has newly found about 10 species that were not recorded from the island. When adding some more species recorded by the other researchers, there are totally 49 species occurred in the Geoje Island.
Why does Coreoleuciscus splendidus leave this nice riffle?
There are only two islands on the South Sea of South Korea where a Korean endemic cyprinid species, Coreoleuciscus splendidus, is occurred. The Geoje Island is one of them. Through the island, C. splendidus has been found only from the upper Sanyang River. In mountainous regions in the Korean Peninsula where C. splendidus is relatively common, the species is found over gravel bottom with fast to torrential current. The species loves clear, cool water and beautiful large riffles. All islands in South Korea are small for size so they tend to be unable to support such riffles. According to Mr. Byun, the upper Sanyang River was once called "Kangwon in the Geoje Island", which means there were tough mountains with deep valleys and torrential headwaters, like Kangwon Province. In past, the riffles like those of Kangwon Province, developed in the upper Sanyang River, might support small populations of C. splendidus. Unfortunately, there have been no one who found the species in the Geoje Island, since early in 1990s. For a recent decade, more researchers have visited the upper Sanyang River to find the species even than the last couple of decades. The river is still clear and supporting riffles. And there are still many species that was recorded at the same time as C. splendidus. Nobody knows the reason why C. splendidus has been disappeared.
Mr. Byun also is an enthusiast who is eager to know why there is no more C. splendidus and whether there is still a few populations. He planned to have a trip so called "finding C. splendidus" to the upper Sanyang River with me, Hyung-Bae and several other teachers who also are belonging to the Haneulgang.
The spot Mr. Byun introduced was greatly beautiful. There is no artificial structures on banks and waterbody. Richly developed vegetation along the river reminds me of somewhere in tropical rain forest. A section of riffle that harbor the shore with nice looking pine groves was like an ancient river in mountainous regions of the South Korea.
* me at our secret spot!
Water was chest-deep in another spot so my shirt was wet.
* me in the Sanyang River forest
* Upper Sanyang River in the Geoje Island
I found no one swimming or hanging out there in such a gorgeous river. This is because this section of the upper river which is about 3.5 km-long has been protected as a drinking water supply. There is Gucheon Dam built about twenty years ago at lower area for a purpose of drinking water supply. The dam probably destroyed a certain portion of the habitat of C. splendidus. However, especially nowadays, the dam provides a nice long habitat for animals living around the river. The upper river would be bothered by human unless there has been such a protection.
Mr. Byun said this upper Sanyang River is his favorite river. If there was a beautiful river like the upper Sanyang River in my neighbor, it would be my favorite. Mr. Byun has had collecting trips to here for several years. At the same time he has collected almost all species recorded from this area with the exception of C. splendidus and Anguila marmorata, he also has found several species historically unrecorded from this section of the river. We collected many species Mr. Byun has collected, but no C. splendidus was found.
A South Korean endemic torrent catfish (Amblycipitidae) species, Liobagrus mediadiposalis, has been recorded from this river. Dr. Young-Mok Son, a previous professor of the Seowon University, studied a biogeographic characteristic of the Geoje Island based on its freshwater fish fauna. He named a mountain chain running through the Geoje Island from the northwest to the southeast "Son's Line". The major freshwater fish species used in Dr. Son's study was L. mediadiposalis. According to him, there are 3 morphologically different types of L. mediadiposalis found in South Korea and the only one type, called "Seomjin River type" is found from the Sanyang River. (The detail will be discussed in the Geoje Island section of the Major South Korean Drainage Divisions.) All three (or potentially more) species of the genus Liobagrus of South Korea love riffle with clear, cool water, like does C. splendidus.
Hyung-Bae found a bunch of L. mediadiposalis's egg. This may mean there are natural reproductions of L. mediadiposalis and the river's environmental condition supports them.
Is there any factor that is not very harmful to L. mediadiposalis but led extirpation of C. splendidus? Or was the extirpation caused by a sort of competition with the other species?
I and Hyung-Bae was thinking about the same questions during our 3 hour-long collecting.
* Liobagrus mediadiposalis's egg.
Where the water gets calm down, Zacco temmincki gets busy with preparing for breeding.
* Why does Coreoleuciscus splendidus leave this nice riffle? There have been no one who answered.
Is Coreoperca kawamebari still there?
Nobody knows how many freshwater fish species has left (been extirpated from) the Sanyang River. We can expect but cannot believe two individuals of the A species, one from the Sanyang River and another one from somewhere far from the Sanyang River are the same species. Also, we cannot deny probability that there were some endemic species to the Sanyang River and they were all extirpated, while there have been a few studies on the freshwater fish fauna of the Sanyang River. However, I can tell a species that was identified as Coreoperca kawamebari has left the Sanyang River. So, according to what we know, there are 2 species that have LIKELY been extirpated from the Sanyang River and Geoje Island (because in Geoje Island they were found only from the Sanyang River): Coreoleuciscus splendidus and Coreoperca kawamebari.
Unlike C. splendidus, C. kawamebari is found over coarse sand and silt bottom with low to moderate current. The shore of habitats are typically richly vegetated, but sometimes not (i.e. Tamjin Dam Lake). According to Dr. Choi's records, the lower Sanyang River (nearby the estuary) was the only habitat of C. kawamebari in the Geoje Island. I think biogeography of the C. kawamebari is more interesting than that of the C. splendidus. C. kawamebari has been collected from Samsan River, Tamjin River, Sanyang River of the South Korea and rivers in the western Japan. In South Korea, the rivers, except Sanyang River, are geographically close to each other, so it is easy to expect that those rivers were connected long time ago. However, although there are many rivers including Seomjin River geographically between Tamjin River and Sanyang River, C. kawamebari has not been found from those rivers. This interesting distribution may easily make sense when taking a closer look at the distribution map.
About 10 years ago, I was travelling here in the Sanyang River estuary with my parents to feagure out what freshwater fish are living here. I already knew C. kawamebari was collected from some spots near here, but I did not know where they exactly are. More than 30 meters from here to the upper area, there is still a small impoundment.
At that time, like nowadays, sea water rise up to right below the impoundment. As we can see from the picture, there is poorly developed intertidal zone along the waterbody. Therefore, this section may be a good habitat for some Gobiidae species and Plecoglossus altivelis, but not for C. kawamebari. I collected several Gobiidae species, Carassius auratus, Pungtungia herzi, Zacco temmincki, Iksookimia longicorpus, Odontobutis obscura, many individuals of Plecoglossus altivelis and so on from upper areas of the impoundment.
* Sanyang River estuary
* Lower Sanyang River
Mr. Byun introduced a well-known spot to us. It was the lower Sanyang River under a small bridge named "Omangcheon-Gyo", where the last population of C. kawamebari was collected by Dr. Son in early 1990s. Mr. Byun also has searched for the species for several years but no specimen has been found. After a half hour long collecting, he asked me and Hyung-Bae if environmental condition of the spot is different from that of the rivers that still support large number of C. kawamebari as we see. Literaly "as we see", water is a little more clear than Samsan River and some important features, such as substrates, vegetation development, water depth and current also did not look bad. C. kawamebari is not a species that is strongly effected by water clarity. In Tamjin River drainage where harbors the largest population of the species, C. kawamebari is sometimes found in a small drain from rice-paddies, reservoir, large gravel riffle and even in a large dam lake, Tamjin Dam.
There is a relatively large reservoir in the middle Sanyang River, called Yeondam Lake and built before the last specimen of C. kawamebari. I and Hyung-Bae thought if C. kawamebari is still here in the Sanyang River, the last population may live in the Yeondam Lake. Before the Tamjin Dam was built in the middle Tamjin River, it was said "C. kawamebari will be extirpated from the upper reaches due to environmental changes" by people who heard the news about the dam. However, it has been three years since the first discharge of the dam and there are still a large number of C. kawamebari in the dam lake. Therefore, Mr. Byun may need to contact fishermen in the Yeondam Lake.
What is the biggest difference between Tamjin River and Sanyang River? Historically, less than 5 individuals of C. kawamebari were collected from the Sanyang River in every single collecting. So, size of historic population would be a difference? If it is, probably there was a series of heavy environmental alterations occurred extensively in the lower Sanyang River during the 1990s. Thus, the alterations wiped C. kawamebari out. In this case, it makes sense that there is no more C. kawamebari, although today's environmental condition of the lower Sanyang River looks fairly okay (because it has been recovered at least for ten years), compared to Samsan River and Tamjin River.
I do not think saying "a certain species has been extinct" is a very good language. There is a much better way to express the same meaning : "a certain species has not been found for -- years" or "the last specimen was collected -- years ago. " I would like to say "Coreoleuciscus splendidus has not been found in the Sanyang River for 20 years and the last specimen of Coreoperca kawamebari was collected from the lower Sanyang River 15 years ago." In the world, there are many species, that are recently found again in wild, whose last specimens were collected over 50 years ago. So, I hope anyone find C. splendidus and C. kawamebari again in the Sanyang River soon.
Day 2. (May 31, 2009)
Oepo Creek estuary
The first site for the second day was Oepo Creek. The Oepo Creek is a small, less than 6km, and independent creek that flows into the South Sea. Mr. Byun supposes that estuary fish fauna of the Oepo Creek may be different from that of Sanyang and Yeoncho River. He thinks a major reason is that the sea to which the Oepo Creek flows is opened to outer ocean, whereas the sea to which Sanyang and Yeoncho River flow is surrounded by many smaller islands so it seems like a bay. According to his idea, direction and origin of the oceanic currents that flow through the estuaries of the rivers(and creeks) probably are all different, because morphologies of the inner sea nearby the estuaries are very different each other. Many of estuary fish species may "take" oceanic currents to move.
* Oepo Creek estuary
Of course, I would like to support Mr. Byun's idea about the estuary fish fauna of the Geoje Island. However, I would focus more on habitat structure, such as substrate, size of the stream and seaweed fauna, since I think the Geoje Island is too small to be heavily effected by the oceanic currents distribution. The Sanyang River estuary consists of tidal mud flat with poor vegetation. The Oepo Creek estuary supports rocky shore with large sized seaweed species. Thus, probably there are more Anguila japonica, Acanthogobius sp. and Mugilogobius abei in the Sanyang River and more Favonigobius gymnauchen, Luciogobius guttatus and Takifugu niphobles in the Oepo Creek.
I went with Hyung-Bae to the lower area(estuary) than the bridge(shown in the picture above) and the teachers led by Mr. Byun went to the upper area which is closer to actual freshwater. The estuary was approximately chest-deep and harbors various habitats including rocky shore, seaweed bed over gravel bottom and pelagic water over sand bottom.
From the bridge, we could see hundreds of Takifugu niphobles. Some of them looks ready for spawning. We also saw large schools of striped mullet (Mugil cephalus) and a few flathead (Platycephalus indicus)
in the pelagic area, but it was impossible to catch those with my kicknet. My kicknet used in this trip is the largest one I have at home in South Korea. Last year, I bought this net from a tiny, shabby fishing shop managed by a local couple near the Jeongra Harbor in the Samcheok county. As always, like any other locals there, the couple was so drunken and called for 2,0000 won(about $20) for a net. At that time, I doubted the price and just did not want to speak more with them. But the price made a lot of sense to me, when I first used the net to collect Iksookimia koreensis for my project. In this trip, Hyung-Bae also was amazed how well the net works. It worked as not only a kicknet but also a seine. When we used the net as like a seine, I and Hyung-Bae hold the pole and do houling up to the shore. "Some" of the fishes we collected are shown as followings:
* Chaenogobius mororanus (Gobiidae)
* 얼룩망둑 (망둑어과), Identified by Jeon, Hyung-Bae
The specimen was collected from sandy shore with richly developed seaweed bed. The species has been found in the Russian Far East, East Sea coast of North Korea and South Korea, South Sea of South Korea, Japan and the southeastern China.
* Pseudoblennius percoides (Cottidae)
* 돌팍망둑 (둑중개과), Identified by Jeon, Hyung-Bae
The specimen was collected from rocky shore with seaweed bed. The species has been found in coast and estuary in South Korea and Japan.
* Pholis fangi (Pholidae)
* 흰베도라치 (베도라치과), Identified by Jeon, Hyung-Bae
The specimen was collected from rocky shore. The species has been found in coast and estuary of the Yellow Sea Region(North Korea, South Korea, the eastern China) and Japan.
* Thryssa chefuensis (Engraulidae)
* 청멸 (멸치과), Identified by Jeon, Hyung-Bae
The specimen was collected from sandy shore. The species has been found in shallow ocean and estuary of the southern South Korea, Japan, the southeastern China, Taiwan and the Southeast Asia.
* Neoditrema ransonneti (Embiotocidae)
* 인상어 (망상어과), Identified by Jeon, Hyung-Bae
The specimen was collected from rocky shore with seaweed bed. This matrotrophic viviparous species has been found in shallow ocean and estuary of the South Korea and Japan.
* Mugil cephalus (Mugilidae)
* 숭어 (숭어과)
The specimen was collected from sandy shore. The species is common worldwidely in temperate ocean, estuary and lower river.
While I and Hyung-Bae was working in the estuary, Mr. Byun and his fellows were in the lower creek. The Oepo Creek, as mentioned earlier, tends to lack water flow due to its short length and small size of the catchment. It seems that the creek may be often dried up in late spring and early fall (usual dry seasons in the South Korea).
* Lower Oepo Creek
They collected several Gobiidae species, including Chasmichthys gulosus, Chaenogobius urotaenia, Acanthogobius flavimanus, A. lactipes and Favonigobius gymnauchen, Anguila japonica and Rhynchocypris oxycephalus. R. oxycephalus tends to be the most dominant freshwater fish species in headwater of hills and relatively lower mountainous areas. The species are, sometimes, occurred in lower river when there are spring runs directly flowing into the lower river or the river itself keeps its headwater-like habitat from the upper to the lower reach. Probably the latter case fits the Oepo Creek.
I do not know why Chasmichthys gulosus (see the picture on the left) has not been introduced in books written on freshwater fish. This owner of extremely large mouth is commonly found in tidal pool, tidal creek, inner bay and warm estuary. I have seen this species in wild only in the South Sea coast of South Korea.
The species on the left is Favonigobius gymnauchen. It is found all around the coastal areas of South Korea and especially common in the South Sea. I have never tried to raise this fish in a home aquarium. I hope to get a chance in the future. This fish will be cool over dark coloured, monotonous substrate.
Another nice looking goby, Acanthogobius lactipes. We are looking at a male fish in the picture on the left. It is hard for me and Hyung-Bae to sort young and female fish of this species, when A. lactipes is mixed with F. gymnauchen in a jar. I have used a morphometric characteristic that can be summarized like A. lactipes has at least two more fin rays on the first dorsal fin. Hyung-Bae said the lower jaw is shorter than the upper jaw in A. lactipes and the lower jaw is longer in F. gymnauchen. Yes, I like Hyung-Bae's method.
Yeoncho River estuary
The next spot was the Yeoncho River estuary. The Yeoncho River is the second longest stream following the Sanyang River in the Geoje Island. According to Mr. Byun, the Yeoncho River boasts the highest freshwater fish diversity in the Geoje Island. He wonders why, because the Yeoncho River is located around the place where the human population density is the highest in the Geoje Island and the river has been suffered from human settlement. I would focus on habitat diversity of the river to answer Mr. Byun's question. The Yeoncho River supports larger macrophytes-dominated littoral zone than the Sanyang River. Although the Sanyang River has more gravel riffle-like area than the Yeoncho River, there are historically not many fish species that occure in riffle in the Geoje Island.
The water clarity there was one of the lowest among relatively bigger streams in the Geoje Island. It may be due to human population density in the area. However, the habitat looks fine, since there were large gravel bottomed pool and riffle, small mud flat and shore vegetation. This spring, Mr. Byun collected several individuals of Gasterosteus aculeatus. It was the first record of the species from the Geoje Island. This fish shows worldwide(cold and temperate zones) distribution and common in the East Sea coast of the South Korea. Also, there are many streams where the species has been found in the South Sea and there are several records of the species from the southern Yellow Sea coast.
* Yeoncho River estuary
There are 2 species that Dr. Choi collected in the 1970s from the Yeoncho and Sanyang River and have not been found by the other researchers: Tribolodon hakonensis and Anguila marmorata. Both species are amphidromous fish and T. hakonensis is a anadromous and A. marmorata is an catadromous fish. T. hakonensis is relatively common along the East Sea and South Sea coast. According to my experience, T. hakonensis prefers larger river or coastal freshwater lagoon. This is probably one of the reason why this species is so uncommon in the Geoje Island that there have been no one who collect since the 1970s. However, the lower Yeoncho and Sanyang River look like fairly good habitats for the species and I think the species may be collected if try more in early spring.
I collected several young individuals of Chaenogobius castaneus and Mr. Byun collected an adult male one. This species has already been recorded only in the Yeoncho River, but was not by Mr. Byun. Mr. Byun looked happy, saying "ah, found one more!". We got several other species including Tridentiger obscurus, Chaenogobius urotaenia, Favonigobius gymnauchen, Mugilogobius abei and many young of the years of Lateolabrax japonicus.
Hyung-Bae especially was impressed by the beauty of Mugilogobius abei. This species is a tiny (less than 5cm) Gobiidae fish that lives in shallow tidal pool or creek with coarse sand bottom. The species was once known as a "rare species", but actually is common in the Yellow Sea coast. Mr. Byun firstly collected this species in the Geoje Island.
The species in the picture on the left is Chaenogobius castaneus that Mr. Byun collected. In fishtank, this species does not spend most of time on substrate, unlike the other Gobiidae fish. The movement shown in a fishtank reminds of "flying". This species is called "Nal-Mangduk (날망둑)" in the Korean common name. In the Korean language, "Nalda" means "flying". I wonder the Korean common name of this species, "Nal-Mangduk", is named after its movement which is like "Nalda".
An unwelcomed guest in macrophytes zone
When we were done in the Yeoncho River estuary, it was 1:30 pm. Hyung-Bae had to arrive in Seoul to see his friends, so we needed to consider the time. Mr. Byun asked me how about 3:30 pm is for departure. It was on Sunday, so the traffic northward to Seoul should be bad. We had only about 30 minutes for the middle Yeoncho River, where harbors nice looking macrophytes zones.
Mr. Byun was looking for a tiny Cyprinid fish, Aphyocypris chinensis, in the middle Yeoncho River. In South Korea, this species is common along the Yellow Sea coast in rice-paddy, drain, reservoir, pond and marsh. There was a record of this species from the Geoje Island, according to Dr. Choi's studies published in the 1980s. However, nobody has found this species in the Geoje Island since then. A. chinensis is usually collected in flock with ricefishes such as Oryzias sinensis or O. latipes. These fishes all prefer macrophytes dominated littoral zone with still water to low current. Since Mr. Byun has many experiences of collecting A. chinensis out of the Geoje Island and knows what its habitat looks like, he has tried in the middle Yeoncho River.
* middle Yeoncho River
We collected more than two hundreds individuals of Oryzias latipes and many Carassius auratus and Misgurnus anguillicaudatus. Although these species are usually collected with A. chinensis out of the Geoje Island, there was no A. chinensis in our collecting jars.
While we were wondering, Hyung-Bae picked up a small fish from a bunch of fish on the net. It was an unwelcomed guest, nile tilapia, Oreochromis niloticus! This species originally came from the Nile River in the northern Africa. Since this species was well known its great taste, it has worldwidely became a trend to do fish farming with this species. South Korea is not an exception. Although the water temperature in South Korea is much lower than that in the northern Africa, there are natural reproductions in a few tributaries of Imjin River(in Gyeonggi Province), Jinwi River(in Gyeonggi Province) and Seomjin River(in Jeollanam Province). The individual we collected is a young fish. I do not hope it means there is natural reproduction of this species in the Yeoncho River.
<additional pictures>
*(above) Hyung-Bae said shape of the rock surface seems to be dinosaurs' footprints.
I am pointing a finger at one of them.
*(above) After collecting in the Yeoncho River estuary.
from the left to the right: me, Mr. Byun, and Mr. Jeong.
* while collecting in the Yeoncho River estuary.
from the left to the right: a fellow of Mr. Byun's, Mr. Byun, Hyung-Bae Jeon, and me.
2009-06-12, Dae-Min Kim