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Estimating fishing effort and spatio-temporal distribution of longline vessels in the Indian Ocean


Utama, FW and Hoenner, X and Hardesty, BD and Peel, D and Ford, JH and Adams, V and Wilcox, C, Estimating fishing effort and spatio-temporal distribution of longline vessels in the Indian Ocean, Frontiers in Marine Science, 8 Article 671036. ISSN 2296-7745 (2021) [Refereed Article]

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Copyright Statement

Copyright © 2021 Utama, Hoenner, Hardesty, Peel, Ford, Adams and Wilcox. This article is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) License, (, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

DOI: doi:10.3389/fmars.2021.671036


Protein from fish is essential for feeding the world’s population and is increasingly recognized as critical for food security. To ensure that fisheries resources can be sustainably maintained, fisheries management must be appropriately implemented. When logbook and landing records data are not complete or are incorrect, it is challenging to have an accurate understanding of catch volume. Focusing on Indonesian longline vessels operating in the Indian Ocean from 2012–2019 (n = 1124 vessels), our aims were to (1) assess compliance through identification of landing sites and potentially illicit behavior inferred by interruptions in VMS transmission, and (2) understand how the fishery operates along with quantifying the spatio-temporal distribution of fishing intensity by applying a Hidden Markov Model, which automatically classified each VMS position as fishing, steaming and anchoring. We found vessel compliance gaps in 90% of vessels in the dataset. Compliance was questionable due both to the widespread occurrence of long intermissions in relaying VMS positions (mean = 17.8 h, n = 973 vessels) and the use of unauthorized landing sites. We also observed substantial changes in fishing effort locations among years. The introduction of regulatory measures during the study period banning transshipment and foreign vessels may be responsible for the spatial shift in fishing activity we observed, from encompassing nearly the whole Indian Ocean to more recent intense efforts off western Sumatra and northern Australia.

Item Details

Item Type:Refereed Article
Keywords:fishing effort, hidden Markov model, longline, vessel monitoring system, vessel compliance, VMS, IUU, spatial management
Research Division:Environmental Sciences
Research Group:Environmental management
Research Field:Conservation and biodiversity
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Marine biodiversity
UTAS Author:Hardesty, BD (Dr Britta Hardesty)
UTAS Author:Adams, V (Associate Professor Vanessa Adams)
UTAS Author:Wilcox, C (Dr Chris Wilcox)
ID Code:146270
Year Published:2021
Deposited By:Geography and Spatial Science
Deposited On:2021-08-26
Last Modified:2021-10-14
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