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Fisheries catch assessment using GPS trackers and effort mapping of small-scale fishers in Davao Gulf
Fisheries catch assessment using GPS trackers and effort mapping of small-scale fishers in Davao Gulf
Andre C. da Costa Neves a, Edison Roi D. Macusi b
São Sebastião, São Paulo Brazil
São Sebastião, São Paulo Brazil
This professional practice was delivered in a remote way due to covid-19 outbreak.
Home office during professional practice in São Sebastião, city of São Paulo, Brazil.
Study Area
Study Area
The Davao Gulf is located in South Philippines on the island of Mindanao.
The fishermen that voluntarily participated in the study leave from ports in the eastern part of the Davao Gulf.
Ecological Questions?
Ecological Questions?
- Where are the main fishing grounds? How is it the fishing effort allocation on them?
- How long do they stay to fish in their fishing ground?
- How far do they fish from their home port?
- Is the distance that they go from their home port a regular occurrence or is it random?
- Do they fish randomly, go in all directions, or is there a regular pattern that they are all fishing and going to this basic fishing ground?
Phase 1: Processing the data
Phase 1: Processing the data
Sampling
Sampling
GPS devices were distributed to artisanal fishermen in Davao Gulf.
The sampling was done before and during the professional practice.
Raw data
Raw data
Raw data consisted in Excel spreadsheets with position (latitude and longitude), speed, direction, date and time.
Positions of 16 fishing boats.
Georeference
Georeference
Georeference all the GPS readings in QGIS.
Imported the data including the attribute table.
Phase 2: Filtering
Phase 2: Filtering
Distinguish the fishing trips
Distinguish the fishing trips
Tracks of all fishing trips.
Tracks of all fishing trips.
Two main ports identified:
Two main ports identified:
- Lupon
- Governor Generoso
Phase 3: Analyzing
Phase 3: Analyzing
Fishing gear dependent speed
Fishing gear dependent speed
Where are the main fishing grounds?
Where are the main fishing grounds?
Lupon
Lupon
Identifying the fishing grounds and the fishing effort allocated in each of them.
Governor Generoso
Governor Generoso
Used the coordinates with speed equal to zero to represent the fishing activity.
How deep do they fish?
How deep do they fish?
Raster layer bathymetry
Raster layer bathymetry
Analyzing the depths where the boats fish.
Extracted the raster value from the bathymetry raster layer for each GPS position with speed equal to zero.
Results:
Not all the boats fish on the same depth (p<0.05).
How far do they fish from their home port?
How far do they fish from their home port?
Is this distance a regular occurrence?
Is this distance a regular occurrence?
Analyzing the distance from the homeport
Analyzing the distance from the homeport
Results:
The null hypothesis was rejected. Meaning that the mean distance traveled from the home port is not the same between all the boats (p<0.05).
Discussing the Ecological Questions
Discussing the Ecological Questions
Some fishing grounds have been identified, usually there is an area close to the shore intensively fished, while other fishing grounds remain further offshore with different levels of effort.
The analysis regarding the time was compromised due to a lack of periodicity in the GPS readings.
The spatial behavior of the artisanal fishermen in eastern Davao Gulf is significantly different between them, in terms of depth they fish and distance traveled from the home port.
Video_georeferecing.movVideo showing the process of georeferencing the fishing trips using QGIS.
Homogeneous Subsets
4. Even though the variation in depth between all fishermen is significantly high, we could still observe significant similarities in the depth between small groups of fishermen (p>0.05). It might be related to the size of the boat, engine, fishing gear and target species.
5. Through the observation of the fishing routes, we could identify that the fishermen usually go to the same fishing grounds. They tend to go to the fishing ground that they went on the previous day. Some big changes on the fishing route are observed, but they are less frequent.
Conclusion
Conclusion
This professional practice was an unique experience in terms of adaptation to new scenarios, self-learning and international network. I had the opportunity to develop my skills on GIS analysis and gain knowledge on fisheries. It will definitely has a good impact on my professional career.
Bibliography
Bibliography
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