Aggregation processes of Tuna under Drifting Fish Aggregating Devices (DFADS) assessed through fisher's echosounder buoy in the Indian Ocean

The aggregative behavior of tuna around floating object is widely exploited by the industrial purse-seine fishery, which deploy thousands of floating objects each year in all oceans in order to improve their catches. These fish aggregating devices (FADs) are generally equipped with echosounder buoys that can collect acoustic data, conferring to these devices the status of privileged observation platforms for the fish communities that aggregate. Using a classification model based on supervised learning algorithms trained on M3I buoy data, we were able to translate the acoustic data collected along the trajectories of 5748 drifting FADs newly deployed between 2016 and 2018 in the Indian Ocean into presence or absence of tuna aggregation. Analysis of the resulting time series indicated that drifting FADs are colonized by tuna aggregation over an average of 39 days. The results also revealed, for the first time, that the residence time of a tuna aggregation around a single DFAD is about 6 days and that DFADs spend on average 9 days without tuna. After colonization, DFADs appear to be occupied by tuna aggregation about 43 % of their soaking time. Finally, we showed that these metrics can manifest spatial and temporal variations

Machine learning for characterizing tropical tuna aggregations under Drifting Fish Aggregating Devices (DFADs) from commercial echosounder buoys data

The use of echosounder buoys deployed in conjunction with Drifting Fish Aggregating Devices (DFADs) has progressively increased in the tropical tuna purse seine fishery since 2010 as a means of improving fishing efficiency. Given the broad distribution of DFADs, the acoustic data provided by echosounder buoys can provide an alternative to the conventional CPUE index for deriving trends on tropical tuna stocks. This study aims to derive reliable indices of presence of tunas (and abundance) using echosounder buoy data. A novel methodology is presented which utilizes random forest classification to translate the acoustic backscatter from the buoys into metrics of tuna presence and abundance. Training datasets were constructed by cross-referencing acoustic data with logbook and observer data which reported activities on DFADs (tuna catches, new deployments and visits of DFADs) in the Atlantic and Indian Oceans from 2013 to 2018. The analysis showed accuracies of 75 and 85 % for the recognition of the presence/absence of tuna aggregations under DFADs in the Atlantic and Indian Oceans, respectively. The acoustic data recorded at ocean-specific depths (6-45m in the Atlantic and 30-150m in the Indian Ocean) and periods (4 a.m.-4 p.m.) were identified by the algorithm as the most important explanatory variables for detecting the presence of tuna. The classification of size categories of tuna aggregations showed a global accuracy of nearly 50 % for both oceans. This study constitutes a milestone towards the use of echosounder buoys data for scientific purposes, including the development of promising fisheries-independent indices of abundance for tropical tunas

Preliminary results of BIOFAD project: testing designs and identifying options to mitigate impacts of drifting Fish Aggregating Devices on the ecosystem

The EU project BIOFAD was launched in August 2017. This 28-months EU project is coordinated by a Consortium comprising three European research centers: AZTI, IRD (Institut de recherche pour le développement) and IEO (Instituto Español de Oceanografía). The International Seafood Sustainability Foundation (ISSF) is also actively collaborating by providing the biodegradable materials needed to test biodegradable dFADs (drifting FADs). Following IOTC, along with other tuna RFMOs, recommendations and resolutions to promote the use of natural or biodegradable materials for dFADs, this project is seeking to develop and implement the use of dFADs with both characteristics, non-entangling and biodegradable, in the IOTC Convention Area. However, there are no technical guidelines on the type of materials and FAD designs to be used. The main objectives of the project are: (1) to test the use of specific biodegradable materials and designs for the construction of dFADs in real fishing conditions; (2) to identify options to mitigate dFADs impacts on the ecosystem; and (3) to assess the socio-economic viability of the use of biodegradable dFADs in the purse seine tropical tuna fishery. This document shows the preliminary results regarding the effectiveness of around 716 BIOFADs deployed, in terms of tuna aggregation, drift, materials’ durability, etc. in comparison to currently deployed NEFADs (non-entangling dFADs). The project BIOFAD has counted since its inception with the support of the whole EU purse seine tuna fishery and, more recently, with the collaboration of the Korean purse seine fleet

Results of the BIOFAD Project: Testing Designs and Identify Options to Mitigate Impacts of Drifting Fish Aggregating Devices on the Ecosystem

The EU project BIOFAD was launched in August 2017. This 28-months EU project is coordinated by a Consortium comprising three European research centers: AZTI, IRD (Institut de recherche pour le développement) and IEO (Instituto Español de Oceanografía). The International Seafood Sustainability Foundation (ISSF) is also actively collaborating by providing the biodegradable materials needed to test biodegradable dFADs (drifting FADs). Following IOTC, along with other tuna RFMOs, recommendations and resolutions to promote the use of natural or biodegradable materials for dFADs, this project is seeking to develop and implement the use of dFADs with both characteristics, non-entangling and biodegradable, in the IOTC Convention Area. However, there are no technical guidelines on the type of materials and FAD designs to be used. The main objectives of the project are: (1) to test the use of specific biodegradable materials and designs for the construction of dFADs in real fishing conditions; (2) to identify options to mitigate dFADs impacts on the ecosystem; and (3) to assess the socioeconomic viability of the use of biodegradable dFADs in the purse seine tropical tuna fishery. This document shows the results regarding the effectiveness of 771 BIOFADs deployed within the project, in terms of FAD lifespan, drift, materials’ durability, catch and tuna aggregation in comparison to currently deployed NEFADs (non-entangling dFADs). The project BIOFAD has been supported since its inception by the whole EU purse seine tuna fishery and, more recently, with the collaboration of the Korean purse seine fleet