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Dr. Pascal Thoya
Macquarie Univerisity, Sydney, Australia

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Research Keywords & Expertise

0 Fisheries Management
0 Fisheries Science
0 blue economy
0 GIS & Environmental Modelling
0 Marine Spatial Planning (MSP)

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Journal article
Published: 29 March 2021 in Sustainability
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Spatially explicit records of fishing activities’ distribution are fundamental for effective marine spatial planning (MSP) because they can help to identify principal fishing areas. However, in numerous case studies, MSP has ignored fishing activities due to data scarcity. The vessel monitoring system (VMS) and the automatic identification system (AIS) are two commonly known technologies used to observe fishing activities. However, both technologies generate data that have several limitations, making them ineffective when used in isolation. Here, we evaluate both datasets’ limitations and strengths, measure the drawbacks of using any single dataset and propose a method for combining both technologies for a more precise estimation of the distribution of fishing activities. Using the Baltic Sea and the North Sea–Celtic Sea regions as case studies, we compare the spatial distribution of fishing effort from International Council for the Exploration of the Seas (ICES) VMS data and global fishing watch AIS data. We show that using either dataset in isolation can lead to a significant underestimation of fishing effort. We also demonstrate that integrating both datasets in an ensemble approach can provide more accurate fisheries information for MSP. Given the rapid expansion of MSP activities globally, our approach can be utilised in data-limited regions to improve cross border spatial planning.

ACS Style

Pascal Thoya; Joseph Maina; Christian Möllmann; Kerstin Schiele. AIS and VMS Ensemble Can Address Data Gaps on Fisheries for Marine Spatial Planning. Sustainability 2021, 13, 3769 .

AMA Style

Pascal Thoya, Joseph Maina, Christian Möllmann, Kerstin Schiele. AIS and VMS Ensemble Can Address Data Gaps on Fisheries for Marine Spatial Planning. Sustainability. 2021; 13 (7):3769.

Chicago/Turabian Style

Pascal Thoya; Joseph Maina; Christian Möllmann; Kerstin Schiele. 2021. "AIS and VMS Ensemble Can Address Data Gaps on Fisheries for Marine Spatial Planning." Sustainability 13, no. 7: 3769.

Journal article
Published: 02 January 2020 in African Journal of Marine Science
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Ringnet fishing began in the early 20th century and is practised worldwide, mainly to target nearshore pelagic species. The method was introduced to Kenya’s coastal waters by migrant fishers from Tanzania. However, the impacts of this fishing gear remain poorly assessed. We assessed the spatial distribution of ringnet fishing effort and its possible effects on ecosystem components, such as coral reefs, marine megafauna and marine protected areas, on the south coast of Kenya. We tracked 89 ringnet fishing trips made from December 2015 to January 2016 and used spatial multicriteria analysis to determine hotspots of possible environmental risks. The results showed that habitat type and bathymetric profile influenced the spatial distribution of ringnet fishing effort. Mixed seagrass and coral habitats had the highest concentration of the effort. Most of the habitats in the study area were moderately exposed to the impacts of the ringnet fishery. The study identifies high-risk areas that require spatial measures to minimise possible environmental risks of the gear both to habitats and to endangered sea turtles.

ACS Style

P Thoya; S Pérez-Jorge; Gladys M. Okemwa; H Mwamlavya; A Tuda; N Wambiji; Joseph Maina. Spatial patterns and environmental risks of ringnet fishing along the Kenyan coast. African Journal of Marine Science 2020, 42, 23 -33.

AMA Style

P Thoya, S Pérez-Jorge, Gladys M. Okemwa, H Mwamlavya, A Tuda, N Wambiji, Joseph Maina. Spatial patterns and environmental risks of ringnet fishing along the Kenyan coast. African Journal of Marine Science. 2020; 42 (1):23-33.

Chicago/Turabian Style

P Thoya; S Pérez-Jorge; Gladys M. Okemwa; H Mwamlavya; A Tuda; N Wambiji; Joseph Maina. 2020. "Spatial patterns and environmental risks of ringnet fishing along the Kenyan coast." African Journal of Marine Science 42, no. 1: 23-33.

Journal article
Published: 07 September 2019 in Marine Policy
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Bottom trawling is a common fishing method for harvesting demersal marine resources such as prawns and ground fish species. However, bottom trawling is known to have negative impacts on marine ecosystems and several measures have been suggested to sustainably manage the fishing method including, mapping trawling pressure and restricting its use away from fragile marine ecosystems. In this study, we map spatio-temporal distribution of trawling effort using 8900 trawls obtained from logbook statistical data and consequently evaluate the effectiveness of a Vessel Monitoring System (VMS) and a Prawn Fisheries Management Plan (PFMP) in the Malindi-Ungwana Bay, Kenya. The PFMP and VMS aimed at restricting prawn trawling to areas beyond 3 nm from shoreline since 2010 in order to reduce conflict with artisanal fishers. Results show spatio-temporal adjustments in the distribution of fishing effort and catch rates of prawns following regulatory changes in the bay. Encroachment in no-trawl areas occurred gradually between 2011 and 2017 with some years (2013, 2016) depicting over 50% of fishing effort in the no-trawl areas. Trawling within the restricted zone produced higher catch per unit effort (CPUE) of prawns compared to fishing outside the zone. Introduction of VMS in 2017 led to a significant reduction of fishing effort in no-trawl area of about 80% by 2018. The change in fleet behaviour in the bay after introduction of the VMS, provides important insights on how marine spatial planning and technology could be applied to enhance compliance with fishing area regulations, reduce resource use conflicts and promote sustainable fisheries.

ACS Style

Pascal Thoya; Boaz Kaunda-Arara; Johnstone Omukoto; Cosmas Munga; Edward Kimani; Arthur Omondi Tuda. Trawling effort distribution and influence of vessel monitoring system (VMS) in Malindi-Ungwana Bay: Implications for resource management and marine spatial planning in Kenya. Marine Policy 2019, 109, 103677 .

AMA Style

Pascal Thoya, Boaz Kaunda-Arara, Johnstone Omukoto, Cosmas Munga, Edward Kimani, Arthur Omondi Tuda. Trawling effort distribution and influence of vessel monitoring system (VMS) in Malindi-Ungwana Bay: Implications for resource management and marine spatial planning in Kenya. Marine Policy. 2019; 109 ():103677.

Chicago/Turabian Style

Pascal Thoya; Boaz Kaunda-Arara; Johnstone Omukoto; Cosmas Munga; Edward Kimani; Arthur Omondi Tuda. 2019. "Trawling effort distribution and influence of vessel monitoring system (VMS) in Malindi-Ungwana Bay: Implications for resource management and marine spatial planning in Kenya." Marine Policy 109, no. : 103677.

Journal article
Published: 27 December 2018 in Fisheries Research
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Fishers’ spatial behavior affects their incomes, livelihoods and ecological sustainability and is affected by establishment of protected areas, and the impacts of changing climate and weather patterns. An understanding of fishers’ spatial behavior is essential for evaluating catch trends or estimating per-area yeilds. Location choice by fishers has largely been understood through foraging models and empirical studies in large scale, developed country fisheries. This paper uses participatory mapping, logbooks and remotely sensed weather (wind speed) data to explore the influence of weather and capital on the spatial behavior and success of coastal Kenyan small-scale fishers. We test generalized foraging models of fisher behavior. A reef crest separates available fishing grounds in the study area between two distinct areas of dissimilar fish catches. Over half of the fishing trips accessed grounds outside the reef, particularly in the calmer northeast monsoon season. Trips across the reef were more successful both in terms of catch and value per fisher and price per kg. Access across the reef was determined primarily by season but was also affected by métier and daily wind speeds. Amongst a sample of non-motorised trips, crossing the reef was the most important variable for predicting Value Per Unit Effort (VPUE). Other things equal, more productive grounds ought to attract more effort, but access to the fishing grounds beyond the reef is constrained by fishers’ access to capital, fluctuations in weather and the interaction between these variables. Fishers with low levels of capital are more affected by daily weather that limits access to the more profitable fishing grounds. Fishers with more capital are able to access more productive grounds more freely, but at the expense of extra compensation for the capital needed. Thus while gross returns to offshore trips exceed similar returns for nearshore trips, net returns are likely to be more equal. In our study a stark exception to the pattern of higher returns from more capitalised gear is the relatively high VPUE achieved by spear fishers, making the assumption of free movement of labour between gears not valid. The study also adds a temporal complexity to this picture by showing the likelihood of accessing grounds beyond the reef crest varies temporally by season.

ACS Style

Pascal Thoya; Tim M. Daw. Effects of assets and weather on small-scale coastal fishers’ access to space, catches and profits. Fisheries Research 2018, 212, 146 -153.

AMA Style

Pascal Thoya, Tim M. Daw. Effects of assets and weather on small-scale coastal fishers’ access to space, catches and profits. Fisheries Research. 2018; 212 ():146-153.

Chicago/Turabian Style

Pascal Thoya; Tim M. Daw. 2018. "Effects of assets and weather on small-scale coastal fishers’ access to space, catches and profits." Fisheries Research 212, no. : 146-153.

Journal article
Published: 11 December 2018 in Western Indian Ocean Journal of Marine Science
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Bathymetry refers to the depth of the water column in relation to sea level. It is fundamental in marine spatial plan- ning, resource exploration and sustainable management of marine resources. It is also vital for safety of navigation, and planning of coast-based infrastructural developments. However, acquisition of bathymetry data is very expen- sive due to the cost of equipment, expertise and technology needed to collect data and produce maps. Satellite-de- rived bathymetry (SDB) therefore offers an opportunity to generate shallow water bathymetry at extremely reduced costs, mainly due to freely-available multispectral satellite imagery and open-source processing software. This paper presents the application of an already developed and published shallow-water bathymetry derivation model and protocols. The results indicate that the technique could be effective for mapping shallow water bathymetry, with higher accuracy in low to non-turbid waters. The SDB of Mombasa Port was identical to the official charted depths upon comparison, with a R2 value of ~90% and a RMSE of 1.61 m. SDB maps can be categorized as medium resolu- tion due to their relatively low spatial resolution. SDB cannot be used as a stand-alone hydrographic tool but it rather offers a viable reconnaissance solution for mapping shallow coastal waters where hydrographic data gaps exist.

ACS Style

Amon Kimeli; Pascal Thoya; Noah Ngisiang’E; Harrison Ong’Anda; Charles Magori. Satellite-derived bathymetry: A case study of Mombasa Port Channel and its approaches, Kenya. Western Indian Ocean Journal of Marine Science 2018, 17, 93 .

AMA Style

Amon Kimeli, Pascal Thoya, Noah Ngisiang’E, Harrison Ong’Anda, Charles Magori. Satellite-derived bathymetry: A case study of Mombasa Port Channel and its approaches, Kenya. Western Indian Ocean Journal of Marine Science. 2018; 17 (2):93.

Chicago/Turabian Style

Amon Kimeli; Pascal Thoya; Noah Ngisiang’E; Harrison Ong’Anda; Charles Magori. 2018. "Satellite-derived bathymetry: A case study of Mombasa Port Channel and its approaches, Kenya." Western Indian Ocean Journal of Marine Science 17, no. 2: 93.

Journal article
Published: 01 July 2017 in Ocean & Coastal Management
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ACS Style

Gladys M. Okemwa; George W. Maina; Cosmas N. Munga; Elizabeth Mueni; Mwaka S. Barabara; Stephen Ndegwa; Pascal Thoya; Nicholas Ntheketha. Managing coastal pelagic fisheries: A case study of the small-scale purse seine fishery in Kenya. Ocean & Coastal Management 2017, 144, 31 -39.

AMA Style

Gladys M. Okemwa, George W. Maina, Cosmas N. Munga, Elizabeth Mueni, Mwaka S. Barabara, Stephen Ndegwa, Pascal Thoya, Nicholas Ntheketha. Managing coastal pelagic fisheries: A case study of the small-scale purse seine fishery in Kenya. Ocean & Coastal Management. 2017; 144 ():31-39.

Chicago/Turabian Style

Gladys M. Okemwa; George W. Maina; Cosmas N. Munga; Elizabeth Mueni; Mwaka S. Barabara; Stephen Ndegwa; Pascal Thoya; Nicholas Ntheketha. 2017. "Managing coastal pelagic fisheries: A case study of the small-scale purse seine fishery in Kenya." Ocean & Coastal Management 144, no. : 31-39.

Journal article
Published: 01 November 2016 in Regional Studies in Marine Science
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The structure of benthopelagic fish assemblages of the continental shelves and upper slopes along coastal East Africa (Kenya and Tanzania) was studied based on data from bottom trawls during 2012. These surveys are the most recent since the historical bottom trawls conducted in the 70s and 80s along costal East Africa. The bottom trawls sampled fishes in 27 stations along the Kenyan coast using FV Vega, while in Tanzania 24 stations were sampled by MV Mafunzo. A total of 66 fish species in 43 families were trawled in Kenya, while 40 species belonging to 22 families were sampled in Tanzania in depth ranges of 10 m to 230 m. The highest fish biomass was in shallow (50>50 m) of the south coast and shallow and mid-depths (50–150 m) of north coast. The lowest species diversity was associated with Kenyan samples of north coast in the mid-depth (50–150 m) and deep (>> 150 m) waters. The dominant species in the trawls differed with those documented in the historical trawls of the 1970–1980s. The results provide a taxonomic database on the fish species off coastal East Africa useful for monitoring spatio-temporal changes in fish assemblages in the face of climate change effects and increasing exploitation levels.

ACS Style

Boaz Kaunda-Arara; Cosmas Munga; Julius Manyala; Baraka Kuguru; Mathias Igulu; Muhaji Chande; Simon Kangwe; Stephen Mwakiti; Pascal Thoya; Emmanuel Mbaru; Renison Ruwa. Spatial variation in benthopelagic fish assemblage structure along coastal East Africa from recent bottom trawl surveys. Regional Studies in Marine Science 2016, 8, 201 -209.

AMA Style

Boaz Kaunda-Arara, Cosmas Munga, Julius Manyala, Baraka Kuguru, Mathias Igulu, Muhaji Chande, Simon Kangwe, Stephen Mwakiti, Pascal Thoya, Emmanuel Mbaru, Renison Ruwa. Spatial variation in benthopelagic fish assemblage structure along coastal East Africa from recent bottom trawl surveys. Regional Studies in Marine Science. 2016; 8 ():201-209.

Chicago/Turabian Style

Boaz Kaunda-Arara; Cosmas Munga; Julius Manyala; Baraka Kuguru; Mathias Igulu; Muhaji Chande; Simon Kangwe; Stephen Mwakiti; Pascal Thoya; Emmanuel Mbaru; Renison Ruwa. 2016. "Spatial variation in benthopelagic fish assemblage structure along coastal East Africa from recent bottom trawl surveys." Regional Studies in Marine Science 8, no. : 201-209.