# Geostatistical Analysis of the Variability in Sthenoteuthis oualaniensis Fishing Grounds in the Northwestern Indian Ocean High Seas

## TL;DR

This study analyzes how the fishing grounds of Sthenoteuthis oualaniensis in the northwestern Indian Ocean have shifted over time due to environmental and climate changes.

## Contribution

The study introduces an integrative approach combining geostatistical and GAM models to quantify the spatiotemporal dynamics of a key squid species under environmental variability.

## Key findings

- The fishing ground centroid of S. oualaniensis shifted eastward and northward from 2016 to 2024.
- Hotspot areas expanded northeastward but sharply contracted in 2024.
- Environmental factors and spatiotemporal drivers jointly influence the species' abundance.

## Abstract

Sthenoteuthis oualaniensis is a key commercial species in the high-seas fisheries of the northwestern Indian Ocean. Its spatiotemporal distribution is highly uncertain due to the combined influence of climate variability and environmental changes, making fishing ground prediction challenging. In this study, spatial autocorrelation analysis and the standard deviation ellipse model were employed to elucidate the spatiotemporal dynamics of S. oualaniensis fishing grounds, and a GAM model was used to quantify the relationships between its abundance and environmental factors. The results show that the fishing ground centroid has shifted progressively eastward and northward, the resource distribution exhibits clear spatial clustering, and the hotspot areas have expanded toward the northeast. Spatiotemporal factors exert significant impacts on the distribution of S. oualaniensis. Overall, this study highlights the integrative regulatory effects of multi-scale oceanographic variability on the species’ spatial distribution and provides scientific support for dynamic management and sustainable utilization of high-seas fishing grounds in the northwestern Indian Ocean.

Sthenoteuthis oualaniensis is a major commercial species in the high-seas fisheries of the northwestern Indian Ocean. However, its spatiotemporal distribution exhibits strong uncertainty under climate and environmental variability, complicating the understanding of fishing ground dynamics. To investigate the spatiotemporal distribution of S. oualaniensis under climate change, this study analyzed commercial fishing data from 2016 to 2024. The results indicate that the core distribution area of the species is consistently concentrated within 14–19° N and 61–65° E. From 2016 to 2024, the fishing ground expanded annually and shifted overall toward the east and north, with its centroid showing a persistent northeastward trajectory. Global spatial autocorrelation analysis revealed positive and significant Moran’s I values for all years, demonstrating a strong spatial clustering pattern. Hotspot analysis shows that high-abundance areas were primarily located north of 14° N, with an overall northeastward migration trend. Hotspots expanded continuously from 2016 to 2023, but sharply contracted in 2024, shifting further northeast and becoming restricted to 63–68° E and 19–21° N. The GAM results indicate that CPUE in the region is jointly influenced by spatiotemporal drivers and multiple environmental factors. These findings confirm that the spatiotemporal distribution and population dynamics of S. oualaniensis are shaped by the combined effects of environmental variability and temporal–spatial factors, with environmental influences playing a particularly crucial role.