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To explore the effect of the shape and size of the stow net cod-end mesh on the selectivity of Larimichthys polyactis, three different mesh openings were adopted as 30 mm, 40 mm, 50 mm for diamond-mesh cod-end, and 20 mm, 30 mm, 40 mm for square-mesh cod-end in this study, respectively. 12 at-sea trials were carried out in the Haizhou Bay of the Yellow Sea in autumn 2020, using the covered cod-end method. The Logistic selectivity model was applied in the study, based on the analysis of the composition of the catch and the escape rate of juveniles. The effects of mesh shape and mesh size on the selectivity of Larimichthys polyactis were analyzed. The results showed that:63 kinds of fish were caught in the experiment, the body length of Larimichthys polyactis ranged from 80 mm to 134 mm, and the average body length was 106 mm. The proportion of the catch in the diamond mesh and square mesh to the total catch was 41. 45% and 36. 83%, respectively. Under the same mesh size, the release effect of juvenile Larimichthys polyactis with square mesh is better than that of diamond mesh. When the mesh size is 40 mm, the number and mass escape rate of square mesh is 34. 53% and 34. 39 higher than those of diamond mesh, respectively. The 50% selection body length (L50) of the 30 mm and 40 mm square mesh was 5. 93% and 18. 84% higher than the corresponding diamond meshes. The juvenile proportion of Larimichthys polyactis is very high, more than 90%, and almost all of them are juvenile fish. Based on the above test results, considering the resource status and production efficiency of Larimichthys polyactis in Haizhou Bay, it is recommended to expand the mesh size of the cod-end net for fishing Larimichthys polyactis from the currently specified diamond mesh of 35 mm to 50 mm of diamond mesh, or square mesh with 40 mm, to achieve the purpose of effectively protecting the juvenile resources of Larimichthys polyactis. [ABSTRACT FROM AUTHOR]