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Science Journal of Kanagawa University 31 : 89-92 (2020)
Abstract: Molluscs and bottom sediments were collected by dredging in Sagami Bay off Hi-ratsuka in September 2018 and 2019. A total of 350 live specimens were collected, belonging to 24 species: 11 gastropods, 1 scaphopod, 11 bivalves, and 1 cephalopod. Three species (Thais clavigera, Glycymeris vestita, and Paphia amabilis ) were the first record since the dredging investigation started in 2006. All the collected species were warm-water species. The bottom sediment at depths above 5 m was composed of fine to medium sand containing 2.4-3.1% mud, and that about 10 m deep was composed of the same sand with 3.0-4.6% mud. At depths of 20, 30 and 40 m, the bottom sediments were composed of very fine to fine sand containing 4.4-6.4, 9.9-16.4 and 15.3-24.4% mud, respectively. In comparison with the investigation results of 2018, the bottom sediments of 2019 contained more plant fragments and mud.Keywords: molluscan fauna, bottom sediment, dredge, Hiratsuka, Sagami Bay
相模湾平塚沖の貝類相:2018 年と 2019 年の調査結果
大和田正人 1, 3 齋藤礼弥 1, 2 加瀬友喜 1, 2 金沢謙一 1, 2
Molluscan Fauna in Sagami Bay off Hiratsuka:Results of the Investigation by Dredging in 2018 and 2019
Fig. 1.Sampling localities. Arrows show the positions and directions of dredging. The black arrows indicate the investigation in September 2018, and the white arrows indicate that in September 2019.
300m Sagami Bay
Hiratsuka City
Sagami River
St.1
St.3St.4St.5
St.6
St.7St.8
St.10St.11
St.1St.2
St.3
St.4
St.5
St.6
sampling date station position depth (m)September, 2018 St. 1 35°18'09.9"N, 139°22'26.7"E–35°18'00.8"N, 139°21'51.2"E 42.5–44.5
totalSeptember, 2019class scientific name Japanese name September, 2018
distribution areas number ofspecies
Hokkaido to Kyushu 1southern Hokkaido and southward 3
southern Hokkaido to Kyushu 5Tohoku and southward 2
Tohoku to Shikoku 1Kashima sea to Okinawa 1Kashima sea to Kyushu 1
Boso Peninsula and southward 5Boso Peninsula to Kyushu 4Sagami Bay and southward 1
Table 3.Distributions of the species collected in the investigation
Table 2.List of the species collected in the investigations in September 2018 and 2019
92 Science Journal of Kanagawa University Vol. 31, 2020
Fig. 2.Grain size distribution and depth on each locality. Grain size was shown in phi scale.
25
50
%
0
25
50
%
0
φ-3-2-101 φ-4 -3-2-101 -4 -3-2-101 φ-4
25
50
%
0 -3-2-101 φ-4 -3-2-101 φ-4
St.6, 20195.5―5.2 m
St.5, 201910.8―9.4 m
St.4, 201912.6―13.7 m
St.3, 201920.8―22.8 m
St.2, 201930.6―31.6 m
St.1, 201947.3―44.6 m
St.11, 3.7―3.2 m
St.10, 20185.2―4.7 m
St.8, 20189.9―13.3 m
St.7, 201810.5―14.7 m
St.6, 201819.4―21.9 m
St.5, 201819.7―28.0 m
St.4, 201829.9―29.8 m
St.3, 201830.9―31.3 m
St.1, 201842.5―44.5 m
文献 1) Horikoshi M (1957) Note on the molluscan fauna of
Sagami Bay and its adjacent waters. Sci. Rep. Yoko-hama National Univ., Section II. 6: 37-64.
2) 黒田德米,波部忠重,大山 桂 (1971) 相模湾産貝類 . 生物学御研究所編,丸善,東京.
3) Okutani T and Matsukuma A (1982) Some interesting mollusks dredged from the shelf around the southern coast of the Izu Peninsula, Honshu, with description of two new species. Mem. Natn. Sci. Mus., Tokyo 15: 163-183.
4) Okutani T (2006) Protobranchia and Anomalodesmata (Mollusca: Bivalvia) collected in shelf, slope and bathyal zones in Sagami Bay, 2002-2004. Mem. Natn. Sci. Mus., Tokyo 40: 295-306.