Relationship Between the Spatial and Temporal Distribution of Fishing Vessels and the Marine Environment in Namibia’s Exclusive Economic Zone (EEZ)
摘要
Effective fisheries management in Namibia’s EEZ requires a clear understanding of how environmental conditions impact fishing activities and production levels. Although vessel tracking technologies, such as the Automatic Identification System (AIS), have enhanced monitoring efforts, limited research has connected fishing activities to oceanographic variables and actual production outputs. This study examines the spatial and temporal patterns of fishing effort in Namibia’s EEZ. It evaluates the relationship between effort and environmental variables (sea surface temperature and chlorophyll-a) and determines how these factors impact production levels across gear types and vessel flags. The study utilised AIS data from the Global Fishing Watch platform alongside MODIS-Aqua satellite data and production data from 2018 to 2022. Fishing effort was quantified using average fishing hours per square kilometre (hr. km2), mapped onto 0.1° × 0.1° grid cells. Environmental variables were extracted and overlaid with fishing effort maps. Effort was analysed by gear type (trawlers, longliners and others) and vessel flag, incorporating production data to assess fishing efficiency. Production data were analysed with fishing effort and environmental conditions to assess the correlation. Results indicate that Namibian vessels accounted for the highest fishing effort, exceeding 96,000 h over the study period. Fishing activity peaked in 2021 and was most intense at depths of 300–400 m, with SSTs (15–19 °C) and Chl-a concentrations (1–4 mg/m3). Trawlers and longliners showed the highest activity, with trawlers dominating. Environmental factors played a significant role in shaping fishing effort distribution. Chlorophyll-a concentrations showed a general increase, while SST exhibited a downward trend during the study period. This apparent contradiction in environmental trends, with rising Chl-a and decreasing SST, may reflect complex local marine dynamics influenced by the Benguela upwelling system. Production data analysis revealed that areas with higher fishing effort generally aligned with zones of moderate Chl-a and favourable SST, suggesting environmental factors moderately influence catch success. A weak negative correlation was observed between SST and fishing effort, while Chl-a showed a moderate positive correlation. However, efficiency varied by gear type and vessel flag. This study confirms that fishing effort and production in Namibia’s EEZ are seasonally and spatially linked to environmental variables. The integration of AIS data, satellite-derived oceanographic variables, and production statistics offers a more holistic understanding of fishing behaviour. These insights are vital for implementing adaptive, ecosystem-based fisheries management and highlight the need to complement AIS data with catch documentation for more accurate monitoring and policy development.