Impact of sea surface temperature fronts on the spatial distribution of jellyfish in the northern Arabian sea

Abstract

Identifying the spatial distribution of species and their relationship with environmental factors is crucial for conservation and management efforts. In Pakistan, jellyfish are economically significant and serves as an important fishery resource. This study utilized both in-situ and satellite data to investigate the relationship between fish catch and sea surface temperature (SST) gradient magnitude (GM). Notably, an unusually high subsurface Chlorophyll a (Chl-a) level (∼1.5 mg/m³) was observed, significantly higher than surrounding waters (∼0.5 mgm⁻³). Additionally, on October 27 at station 6, a high SST GM of 0.097 °C km⁻¹ was recorded alongside an elevated subsurface Chl-a of 1.24 mg/m³. Low salinity levels (<36.2 psμ) were detected in areas with strong frontal activity, while higher levels (>36.7 psμ) were observed in the surrounding regions. Moreover, a high wind stress curl (>0.4 N/m³) was noted in regions with strong SST fronts along coastal and offshore areas of Balochistan and Sindh. A strong correlation (R² = 0.987) was identified between annual fish catch and catch per unit effort (CPUE). The study revealed a significant fish catch (>200 kg) along the Balochistan coast and the Indus River estuary, with the exception of one offshore catch station. Results also indicated a strong correlated (R² = 0.73, p < 0.001) between SST GM and fish catch in the upper layer (<50 m depth). By establishing a GM threshold at 0.06 °C km⁻¹, there was an 80% likelihood of achieving a high catch within the upper 50 m layer. These findings enhance our understanding of how SST fronts influence the spatial distribution of jellyfish and improve our ability to forecast jellyfish fishing grounds in the northern Arabian Sea.