Study on the influence degree of marine ranching on the high-quality development of coastal cities

As an innovative approach to fisheries, marine ranching is subtly transforming the development patterns of coastal cities through the enhancement of fisheries, the professional transition of fishermen, and the restoration of the marine environment. Utilizing the entropy method and the staggered difference-in-differences (DID) method, this paper calculated the high-quality development index (HQDI) of 53 coastal cities from 2010 to 2021 and assessed the influence degree of marine ranching on coastal cities' HQDI. The key findings were as follows. Firstly, marine ranching generally improved the HQDI of coastal cities. Coastal cities with national marine ranching demonstration zones achieved an average increase of approximately 0.83 % in their HQDI compared to those without. Secondly, through the effect of carbon emission reduction, marine ranching contributed to an average increase of approximately 0.84 % in the HQDI. However, the green technology innovation and industrial structure upgrading effects have yet to materialize. Thirdly, this impact varied among coastal cities. When the number of marine ranching exceeded three, the average increase of HQDI was approximately 1.82 %. This effect was pronounced in higher-tier cities, with first-tier cities experiencing an average increase of 1.26 %, second-tier cities an average increase of 1.19 %, and third-tier cities an average increase of 2.18 %. Furthermore, this effect was significant in northern coastal cities, where the average increase was approximately 0.98 %. In coastal cities with low levels of manpower and material resources, this effect was also pronounced, with the HQDI increasing by an average of about 1.01 % and 0.98 %, respectively. Lastly, the spatial econometric analysis revealed a positive spatial spillover effect. This paper evaluated the effectiveness of China's recent marine ranching construction, providing a theoretical and empirical foundation for authorities to formulate targeted policies and measures.