Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Akihiko Koyama Last modified date:2022.07.25

Assistant Professor / Department of Bioresource Sciences / Faculty of Agriculture

1. Spawning habitat of the Chinese false gudgeon, Abbottina rivularis, in an irrigation channel near the Ushizu River, northern Kyushu Island, Japan.
2. Ryutei Inui, Shion Takemura, Akihiko Koyama, Norio Onikura, Mahito Kamada, Potential distribution of Tridentiger barbatus (Gunther 1861) and Tridentiger nudicervicus (Tomiyama 1934) in the Seto Inland Sea, western Japan, ICHTHYOLOGICAL RESEARCH, 10.1007/s10228-013-0370-y, 61, 1, 83-89, 2014.01, We developed distribution models for two near-threatened gobiid fishes, Tridentiger barbatus and Tridentiger nudicervicus, based on distribution data and geographic variables in the Ariake Sea, the Yatsushiro Sea, and Suonada Bay. Subsequently, we estimated the potential distribution of both species across all areas of the Seto Inland Sea based on the model predictions. The models indicated high accuracy and demonstrated that both species inhabit shoal and relatively enclosed waters. Predicted potential distribution areas of the two species included all sites with previous records and a few new sites without existing records..
4. Takuya Okawa, Yoshihisa Kurita, Kazuki Kanno, Akihiko Koyama, Norio Onikura, Molecular analysis of the distributions of the invasive Asian clam, Corbicula fluminea (O.F. Müller, 1774), and threatened native clam, C. leana Prime, 1867, on Kyushu Island, Japan, BioInvasions Records, 10.3391/bir.2016.5.1.05, 5, 1, 25-29, 2016.03, The invasion of the Asian clam, Corbicula fluminea (O.F. Müller, 1774), has caused serious ecological and economic problems worldwide. In the Japanese archipelago, C. fluminea has been identified using morphological characteristics in most distribution surveys. However, a recent study has shown that morphology alone cannot be used to identify C. fluminea due to its superficial similarity to the related native species C. leana Prime, 1867. Consequently, the present distribution of C. fluminea is still poorly understood. We surveyed the distribution of C. fluminea on Kyushu Island, Japan, by sequencing the cytochrome b region of the mitochondrial DNA, a region that can be used to distinguish the two clam species, and found that C. fluminea was already established throughout the entire island, except at a single site where Corbicula clams comprised solely of C. leana. In response to this serious situation, we suggest using PCR-RFLP method, which was employed here, to distinguish the two clam species for more effective and rapid surveys..
5. Akihiko Koyama, Ryutei Inui, Hiroki Iyooka, Yoshihisa Akamatsu, Norio Onikura, Habitat suitability of eight threatened gobies inhabiting tidal flats in temperate estuaries: model developments in the estuary of the Kuma River in Kyushu Island, Japan, ICHTHYOLOGICAL RESEARCH, 10.1007/s10228-015-0490-7, 63, 2, 307-314, 2016.04, We developed habitat suitability models for eight threatened goby species inhabiting tidal flats in the estuary of Kuma River in Kyushu Island, Japan. The best models selected several environmental factors, which were supported by area under the curve (AUC) values ranging from 0.793 to 0.976. The habitat suitability curves for each variable demonstrated various slopes, suggesting interspecific differences in habitat suitability for each environmental factor. The results suggested that the range of environmental gradients in tidal flats influences the richness of the threatened goby species..
6. Prioritization procedure for protecting native bitterling species with consideration for invasions by several alien species: A case study around the Kikuchi river basin, Kyushu Island, Japan.
7. Akihiko Koyama, Ryutei Inui, Kaito Sawa, Norio Onikura, Symbiotic partner specificity and dependency of two gobies (Apocryptodon punctatus and Acentrogobius sp A) and four alpheid shrimps inhabiting the temperate estuary of southern Japan, ICHTHYOLOGICAL RESEARCH, 10.1007/s10228-016-0535-6, 64, 1, 131-138, 2017.01, We collected two gobies, Apocryptodon punctatus and Acentrogobius sp. A, and four alpheid shrimps from an estuary in southern Japan, to identify the symbiotic shrimps with gobies and to understand their partner specificity and dependency. Analysis based on generalized linear models identified two specific partners for each goby. A. punctatus frequently coexisted with partners and showed similar habitats, suggesting that this goby might be an obligate mutualist. Acentrogobius sp. A had lower rates of coexistence and appeared in habitats different from one of its partners, suggesting that this goby might be a facultative mutualist..
8. Akihiko Koyama, Ryutei Inui, Keitaro Umemura, Mizuki Wakabayashi, Kazuki Kanno, Norio Onikura, The first record of the spawning nest of Gymnogobius cylindricus and Gymnogobius macrognathos, ICHTHYOLOGICAL RESEARCH, 10.1007/s10228-016-0548-1, 64, 2, 261-263, 2017.04.
9. Distribution of Anguilla japonica and A. marmorata in the Nansei Islands, Japan, and their habitat segregation based on local names.
10. Distribution and color variations of Carassius auratus in the Amami-Ryukyu Islands, Japan.
11. Ryutei Inui, Akihiko Koyama, Yoshihisa Akamatsu, Abiotic and biotic factors influence the habitat use of four species of Gymnogobius (Gobiidae) in riverine estuaries in the Seto Inland Sea, Ichthyological Research, 10.1007/s10228-017-0584-5, 65, 1, 1-11, 2018.01, Gobies that are phylogenetically related or coexist in the same marine and estuarine systems often exhibit abiotic and/or biotic habitat segregation. Thus, it is possible that species of Gymnogobius inhabiting the same riverine estuaries also exhibit abiotic and/or biotic habitat segregation. The goal of this study was to determine the differences in abiotic and biotic habitat use between these species by sampling goby and host shrimps, and by examining the physical environments of the rivers where these species are found. The surveys of goby and host shrimps were conducted in the estuaries of the Saba and Ibo rivers, which drain into the Seto Inland Sea, a body of water that separates three of the four main islands of Japan. We used hand nets and shovels to collect goby and host shrimps, and measured median sediment particle size, elevation, and salinity at each site. Generalized linear models (GLMs) were used to assess the preferences in abiotic and biotic habitat use by the goby species. Median particle size, salinity, and elevation were used as the abiotic environmental predictors, whereas the presence/absence of host shrimps were re-organized into four categories consisting of “Upogebia major” only, “Nihonotrypaea japonica” only, “Upogebia major &
Nihonotrypaea japonica,” and “Upogebia yokoyai,” which were used as the biotic environmental predictors. The GLMs demonstrated that median particle size had the largest influence of the abiotic variables, with goby species segregating according to differences in sediments
moreover, there was some evidence suggesting that the host and symbiont do not always correlate at the species level. Our results indicated that although there is some overlap in abiotic and biotic habitat use among the four species of Gymnogobius, the differences were broad enough to provide an explanatory mechanism as to how these species can coexist in the same river systems..
12. Record of a rare pebble-shore crab Cyclograpsus pumilio from Yamaguchi Prefecture to northern coast of Kyushu, Japan, with some notes on their habitat conditions.
13. Distributional records of a rare snapping shrimp Alpheus dolichodactylus in Kyushu, Japan.
14. The northernmost record of a tidal flat crab, Macrophthalmus convexus (Crustacea: Decapoda), based on a specimen from an estuary of Tanega-shima island, southern Japan.
15. Kazuki Kanno, Norio Onikura, Yoshihisa Kurita, Akihiko Koyama, Jun Nakajima, Morphological, distributional, and genetic characteristics of Cottus pollux in the Kyushu Island, Japan: indication of fluvial and amphidromous life histories within a single lineage, Ichthyological Research, 10.1007/s10228-018-0637-4, 65, 4, 1-9, 2018.06, We evaluated the morphological, distributional, and genetic characteristics of the freshwater sculpin, Cottus pollux, in Kyushu Island, Japan. Based on pectoral fin ray number, the sculpins inhabiting 30 rivers were divided into two types [modes 13 (M13) and 15 (M15)]. We evaluated four environmental parameters: length of main river (L-MR), average gradient of main river (G-MR), distance from sampling site to river mouth (D-SM), and gradient around sampling site (G-S), and compared the two types. L-MR, D-SM, and G-S were significantly larger for the rivers that contained M13 fish than for those containing M15 fish. M13 individuals were distributed in the upstream areas of large river systems, suggesting a fluvial life history, whereas M15 individuals were distributed in the downstream areas of small river systems, indicating an amphidromous life history. We conducted phylogenetic analysis based on mitochondrial 12S rRNA [788 base pair (bp)] and control regions (386 bp). Mitochondrial DNA analysis showed that both M13 and M15 groups were genetically of C. pollux middle-egg type (ME). Our findings proposed the hypothesis that C. pollux ME in Kyushu Island exhibits dimorphism in both morphological and distributional traits. Additionally, haplotype distribution indicated that the fluvial M13 populations had higher genetic specificity in each river in contrast to the existence of one genetic group of amphidromous M15 individuals in Kyushu Island..
16. First record of the brachiopod Lingula reevii (Brachiopoda, Lingulidae) from the Sea of Japan.
17. First record of the varunid crab Parapyxidognathus deianira from the coast of the Sea of Japan.
20. Spawning nests of six goby species in a newly-established fish-way on the Onga River estuary barrage.
21. Change of crab and goby fauna in the mitigation tidal flats in the Naka River estuary..
22. Differences in conservation candidate tidal rivers by cross‐taxon analysis in the Japanese temperate zone.
23. Habitat suitability maps for juvenile tri-spine horseshoe crabs in Japanese intertidal zones: A model approach using unmanned aerial vehicles and the Structure from Motion technique
The tri-spine horseshoe crab, Tachypleus tridentatus, is a threatened species that inhabits coastal areas from South to East Asia. A Conservation management system is urgently required for managing its nursery habitats, i.e., intertidal flats, especially in Japan. Habitat suitability maps are useful in drafting conservation plans; however, they have rarely been prepared for juvenile T. tridentatus. In this study, we examined the possibility of constructing robust habitat suitability models (HSMs) for juveniles based on topographical data acquired using unmanned aerial vehicles and the Structure from Motion (UAV-SfM) technique. The distribution data of the juveniles in the Tsuyazaki and Imazu intertidal flats from 2017 to 2019 were determined. The data were divided into a training dataset for HSM construction and three test datasets for model evaluation. High accuracy digital surface models were built for each region using the UAV-SfM technique. Normalized elevation was assessed by converting the topographical models that consider the tidal range in each region, and the slope was calculated based on these models. Using the training data, HSMs of the juveniles were constructed with normalized elevation and slope as the predictor variables. The HSMs were evaluated using the test data. The results showed that HSMs exhibited acceptable discrimination performance for each region. Habitat suitability maps were built for the juveniles in each region, and the suitable areas were estimated to be approximately 6.1 ha of the total 19.5 ha in Tuyazaki, and 3.7 ha of the total 7.9 ha area in Imazu. In conclusion, our findings support the usefulness of the UAV-SfM technique in constructing HSMs for juvenile T. tridentatus. The monitoring of suitable habitat areas for the juveniles using the UAV-SfM technique is expected to reduce survey costs, as it can be conducted with fewer investigators over vast intertidal zones within a short period of time..
24. Temporal changes in benthos at intertidal zones' communities in the Kuma River system: ecological monitoring before, during, and after the Arase dam removal.