Tuna behaviour at anchored FADs inferred from Local Ecological Knowledge (LEK) of pole-and-line tuna fishers in the Maldives

Abstract

The Maldives tuna fishery landings in 2018 were 148, 000 t and accounted for nearly a quarter of the global pole-and-line tuna catch. This fishery partially relies on a network of 55 anchored fish aggregating devices (AFADs) deployed around the archipelago. About one-third of the total pole-and-line tuna catch is harvested at AFADs. Although the AFAD fishery has existed for 35 years, knowledge on the behaviour of tuna in the AFAD array is still limited, precluding the development of science-based fishery management. In this study, local ecological knowledge (LEK) of fishers was used to improve our understanding of tuna behaviour, through personal interviews of 54 pole-and-line fishers from different parts of the archipelago. Interview results suggest that during the northeast monsoon tuna are more abundant on the eastern side of the Maldives, while during the southwest monsoon they are more abundant on the western side of the Maldives. Most fishers believed that tuna tend to stay at the AFADs for 3 to 6 days and remain within 2 miles from the AFADs when they are associated. Fishers believe that strong currents is the main factor for tuna departure from AFADs, though high sea surface temperatures and stormy conditions were also thought to contribute to departures. Moderate currents are believed to be a favourable condition to form aggregations at the AFADs while other factors such as suitable temperature, prey and attractants enhance this aggregation. Fishers also believe that there are multiple schools segregated according to size and species at AFADs and that catchability is higher at dawn and in the late afternoon when the tuna occur shallower in the water column. This study is an important step towards engaging the Maldivian tuna fishers into a science-based fishery management.

Artisanal fishers in small island developing states and their perception of environmental change: the case study of Mauritius

“…Anchored FADs are widely used in the Philippines and Indonesia (Macusi et al 2015 ; Khan et al 2020 ). Other countries in the Indian Ocean using FADs extensively include the Maldives, where a FAD array is used on a semi-industrial scale by the tuna pole and line fishery and is managed by the government (Jauharee et al 2021 ). The use of FADs may be an adaptation method to diversify fishing methods in the wake of climate change as highlighted by Bell et al ( 2018b ) in the Pacific Islands.…”

“…In the context of fisheries, LEK relies on the practical knowledge of fishers on exploited marine ecosystems, based on their site-specific observations and experience. LEK from fishers has been used to infer on fish behaviour (Moreno et al 2007 ; Macusi et al 2017 ; Jauharee et al 2021 ), biology (Silva et al 2020 ) and habitat use (Silvano and Begossi 2012 ). LEK has also been used to identify fishing areas (Schafer and Reis 2008 ) and gather useful information for the management of marine protected areas (Gerhardinger et al 2009 ).…”

“…The use of anchored FADs (Fish Aggregating Devices) is widespread in artisanal and semi-industrial coastal fisheries (Chooramun and Senedhun 2013 ; Karama and Matsushita 2019 ; Khan et al 2020 ; Jauharee et al 2021 ; Tilley et al 2019 ). FADs are floating objects that are used to attract fish and facilitate their capture (Sadusky et al 2018 ).…”

Fish aggregating devices could enhance the effectiveness of blue water marine protected areas

“…Fish aggregating devices have proven uses in marine conservation. For more than 20 years, anchored FADs have been deployed offshore of fishing communities by development and fisheries organizations, to redistribute fishing pressure from coastal ecosystems to pelagic resources (Campbell et al., 2016; Jauharee et al., 2021). Here, we propose deploying FADs that remain inside blue water MPAs could directly and positively enhance their benefits.…”

Fish Aggregating Devices could enhance the effectiveness of blue water MPAs

“…Fish aggregating devices have proven uses in marine conservation. For more than 20 years, anchored FADs have been deployed offshore of fishing communities by development and fisheries organizations, to redistribute fishing pressure from coastal ecosystems to pelagic resources (Campbell et al 2016; Jauharee et al 2021). Here, we propose deploying FADs that remain inside blue water MPAs could directly and positively enhance their benefits.…”