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Project O.2.c - Temporal network analysis of bycatch communities caught in purse-seine fisheries

01 May 2021 - 31 May 2023

Program(s) in charge: Ecosystem & Bycatch Program
Funded
Objectives
  • Investigate the connectivity among bycatch species caught in the purse-seine fishery and how the structure of these community relationships changes over time and space (if feasible) in the eastern Pacific Ocean (EPO).
  • Investigate the vulnerability of those connections and the role of key bycatch species for the community/network
Background
  • Ecological risk assessment (ERA) is an approach currently used by IATTC staff to evaluate the ecological impact of tuna fisheries in the EPO
  • ERA can also help ensure the long-term sustainability of ‘associated’ and ‘dependent’ species that share the same ecosystem as principal tuna species
  • Scientists and managers require novel quantitative methods to reliably identify communities that may include vulnerable species
  • Temporal network analysis (TNA) may help identify the communities with vulnerable species and their evolution, and, where appropriate, help prioritize the call for mitigation measures, further detailed analysis, or the prioritization of data collection on potentially vulnerable species
Relevance for management
The proposed TNA can support ERA by identifying distinct ecological assemblages within the purse-seine bycatch
Duration
12 months, extended to 24 months due to COVID-19 pandemic
Workplan and status
  • Understand the network structures that emerge from the recurrences of the relationships among bycatch species and how these networks change through time.
  • Detect bycatch communities within networks and key bycatch species as centralized actors of these communities.
  • Explore impacts of key bycatch species on their communities through control theory analysis (node removal simulation).
External collaborators
Scripps Institution of Oceanography
Deliverables
A series of dissemination material: documents and presentations for the IATTC Bycatch Working Group, as well as a peer-reviewed scientific publication
Updated date: 01 May 2023
Progress summary for the reporting period
  • A number of meetings were organized with Scripps Institution of Oceanography during 2021-2023.
  • Exploratory analyses of different bycatch metrics by set type were conducted for 2006–2021 data.
  • Preliminary connectivity, network and temporal-network analyses were conducted for the most common bycatch species for each set type.
  • New state-of-the art algorithms and methods are currently being explored by the main researcher to better infer potential relationships between species and communities.
Challenges and key lessons learnt
  • Preliminary results suggest differences in the inshore vs offshore bycatch communities and their structures and between different set types.
Comments
Results of the project are expected to be presented at the EBWG-02 in 2024.