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An evaluation of observer monitoring program designs for Chinese tuna longline fisheries in the Pacific Ocean using computer simulations


This paper evaluates the performance of different observer coverage rates and 9 possible sampling designs to estimate via computer simulation the total catch of target and non-target species for Chinese tuna longline fisheries in the Pacific Ocean. The stratified random samplings include different stratification schemes (based on target species or fishing areas) with different strategies for allocating observers. The observer data from 103 vessels between 2010 and 2019 were assumed to be the “true” sampling population. We concluded that the accuracy of catch estimates had a significant positive relationship with species detectability and observer coverage rate. On average, the accuracy improved by 50% when the coverage rate increases from 5 to 20%. Current simple random sampling in Chinese tuna longline fisheries is less efficient for monitoring many species. Stratified sampling designs based on the target species tended to yield the most accurate estimates of the total catch. Allocating the observers based on the scale of the fleets in different stratum seemed to be less efficient. The proportion of observers between different fleets should be adjusted according to different monitoring objectives. In general, a large proportion of observers are recommended to be allocated onboard vessels targeting bigeye tuna (Thunnus obesus). This study has the potential to have a significant contribution to future designs of the observer monitoring programs in Chinese tuna longline fishery and many other fisheries.

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Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.


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The work was supported by National Key R&D Programs of China (2019YFD0901404) and the scientific observer program of the Distant-Water Fishery of the Ministry of Agriculture and Rural Affairs of the People’s Republic of China (08-25). We would like to thank the National Data Centre for Distant-Water Fisheries of China for providing the observer data (2010–2019). We would also like to thank the observers, the captains of Lianfeng Du and other vessels, and the crew who helped contribute to the collection of data. We are grateful for Shandong Lidao Oceanic Technology Company Limited et al. for their cooperation, and we would like to thank Bai Li and other colleagues in the International Learning Network supported by the Paradise Foundation, Shanghai Ocean University, and the University of Maine for the discussion and revision of this paper.


This work was funded by National Key R&D Programs of China (2019YFD0901404) and the scientific observer program of the Distant-Water Fishery of the Ministry of Agriculture and Rural Affairs of the People’s Republic of China (08-25).

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JW contributed to the conception of the study, performed the data analyses, and wrote the manuscript; XG contributed to the conception of the study and wrote the original draft; JC contributed significantly to analysis and manuscript preparation; XD helped perform the analysis with constructive discussions; ST helped perform the analysis with constructive discussions and financially supported this work; YC analyzed existing literatures and provided a lot of work for the revision of the paper; all authors read and approved the final manuscript.

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Correspondence to Siquan Tian.

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Wang, J., Gao, X., Chen, J. et al. An evaluation of observer monitoring program designs for Chinese tuna longline fisheries in the Pacific Ocean using computer simulations. Environ Sci Pollut Res 28, 12628–12639 (2021).

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  • Observer programs
  • Coverage rate
  • Stratified samplings
  • Tuna longline
  • Pacific Ocean
  • Computer simulation