Academic Research

The Survey of the State of the Ocean Surrounding Ishigaki City

Purpose of the survey

In view of the fact that Ishigaki City is surrounded by a vast ocean, the natural environment of which is a valuable asset for the city, the maintenance, conservation, and utilization of the surrounding maritime area are important issues, and the Basic Plan on Ocean Policy of Ishigaki City (formulated in 2013) also mentions such efforts.

In addition, Ishigaki City has been selected as an “SDGs Future City” and is engaged in initiatives to promote sustainable community development.

This project was formulated as part of efforts to contribute to the achievement of SDGs Goal 14 on “Life Below Water,” and also as part of the implementation of the Basic Plan on Ocean Policy of Ishigaki City , which outlines basic policies for the comprehensive and systematic promotion of the city’s ocean-related policies. As such, in order to maintain, conserve, and utilize the maritime area surrounding Ishigaki City, the project conducts oceanic surveys of water quality and ocean currents, etc., with the aim of better understanding the actual state of drifting marine debris in surrounding waters and marine debris that washes ashore, and also understanding the state of the natural environment of Uotsuri Island, etc.

Overview of survey

Dates	(Sun) January 29, 2023, departure at 17:00 At sea, implementing survey (Mon) January 30, 2023, arrival at 20:00
Survey details	・Survey of fish shoals ・Oceanic survey ・Landscape survey
Maritime areas surveyed	(1) Maritime area around Senkaku Islands (2) Maritime area northwest of Ishigaki Island
Vessel used	Privately owned multi-purpose vessel (Gross tonnage: 697t)

Maritime areas surveyed

Survey time schedule

Date	Time	Movements	Operations
(Sun) Jan 29	16:00		Board
	17:00	Depart Ishigaki port
	19:00	Arrival at survey area (2) Start oceanic and fish shoal surveys	・Implement St.X-CTD-04 ・Implement St.X-CTD-03 ・Monitoring using fish finder device
(Mon) Jan 30	06:00	Arrival at survey area (1)
	07:30	Start oceanic, landscape, and fish shoal surveys	・Implement St.X-CTD-02 ・Implement St.X-CTD-01 ・Observation of the sea and Uotsuri Island from the ship ・Aerial drone surveys and photography and video recording from the ship ・Monitoring using fish finder device
	12:00	Monitoring concluded Return to port
	20:00	Arrival at port	Disembark

Maritime route

Survey details

Fish shoal surveys

In order to better understand marine life in the maritime area around Ishigaki City, a biomass survey of fish shoals was implemented.

Observation of fish shoal

《Survey method》

Observation and recording of fish shoal, using a fish finder device installed on the vessel.

Oceanic survey

In order to understand the status of oceanic pollution, observations were conducted of drifting and adrift marine debris.
The underwater environment was also observed, including the water temperature and salinity in the survey area.

XCTD deployed in the ocean

Maritime observation from the ship

《Survey method》

An X-CTD（eXpendable Conductivity Temperature Depth Profiler: a measuring device to survey ocean temperature and electrical conductivity [salinity] while a vessel is in motion）was deployed into the ocean to observe the vertical profile of water temperature and salinity.

Visual survey

A visual survey of the sea and Uotsuri and other islands using a drone and other equipment was implemented in order to understand and analyze the current state of the maritime area and the Senkaku Islands.

Aerial drone observation

《Survey method》

In addition to visual observations from the ship, cameras and drones were used to record images and video, both from the ship and from the sky.

Scenes from the survey

Survey dates: January 29 and 30, 2023
Survey area: Maritime area around Uotsuri Island

Observation of Uotsuri Island

Patrol by Japan Coast Guard

Drifting marine debris

Marine debris washed ashore

X-CTD

Scenes from a memorial service at sea

Offering of flowers to commemorate those who perished in the wartime incident in which evacuees washed ashore on the Senkaku Islands
Date; January 30, 2023, around 10:00
Location: Waters off Uotsuri Island

Supplementary materials (PDF)