海洋環境因子影響鮪釣船捕撈時數 : 印度洋大尺度空間分析

Abstract

鮪漁業為全球最重要的漁業之一，由於氣候變遷可能導致鮪魚的分布、資源量改變，其漁業資源的管理必須考慮氣候變遷的影響機制。然而，過往研究偏向於環境變化對資源量與生物特性的影響，針對漁船作業時空分布與環境因子互動的研究較為缺乏。本研究針對印度洋熱帶鮪類的重要漁場進行大尺度分析，使用 2016至2019年間漁船船舶自動識別系統（Automatic Identification System）數據，探討台灣籍延繩釣漁船時空分布與表水溫、葉綠素a（chlorophyll-a）、印度洋偶極指數（Dipole Model Index）的相關性。

研究發現，延繩釣漁船作業集中在印度洋西北及西南海域，並具有明顯季節性趨勢。本研究依據漁船目標魚種偏好棲息的區域，以南緯15°為界，分南北兩區討論。結果顯示影響捕撈時數的環境因子中，以表水溫的關聯性最高，在南緯15°以北的海域，表水溫與捕撈時數呈線性相關，作業時數在表水溫大於28.8°C的海域增加。南區捕撈時數與表水溫呈非線性相關，表水溫在12.2°C至20.7°C間的海域對捕撈時數有正向影響。在氣候變遷，海洋暖化的情境下，表水溫可以做為評估未來漁撈動態變化的參考。

Tunas sustain some of the world's most commercially valuable fisheries. Since climate change may largely affect the distribution and abundance of tuna species, management of fishery resources must take these mechanisms into account. However, previous studies have focused on the effects of environmental changes on resource abundance and biological characteristics; studies on the interactions between vessel activities and environmental factors are limited. In this study, we investigated Taiwanese longline fishing vessels' spatial-temporal distribution and the relationship between sea surface temperature, chlorophyll-a, and Dipole Model Index.

We found that vessel operations were concentrated in the northwestern and southwestern of the Indian Ocean, with clear seasonal patterns. The study area was divided into north and south regions based on the boundary of 15°S latitude by the temperature preference of the target species. The results showed that sea surface temperature had the highest correlation among the environmental factors. In the northern region, sea surface temperature was linearly correlated with fishing hours, and the hours increased when the temperature was more significant than 28.8°C. In the southern region, fishing hours were non-linearly correlated with sea surface temperature; a positive effect on fishing hours occurred between 12.2°C and 20.7°C. The findings suggest that sea surface temperature can be used as a reference to assess future fishing dynamics.