Mantis shrimp (Oratosquilla oratoria), the main catches of stow net fishing vessel in Zhangpu, Fujian Province, were followed and sampled monthly from August 2022 to April 2023. A total of 368 samples were used to determine the body length and body mass, to characterize the feeding intensity and female ovarian development, and to calculate the ratio of males to females in the catch, in order to analyze the fishery biology of O.oratoria. The results showed that the ratio of female to male was 1∶1.115 in the catch of O.oratoria, the dominant body length group was 110-130 mm, the dominant body mass advantage group was 15.0-25.0 g,and there was no significant difference in average body length and average body mass between male and female samples. The relationship between body length and body mass was W = 2.140×10^-5L^2.882 (R² =0.946, n=368). The gonadal maturity of female O.oratoria was between stage Ⅰ-Ⅲ, and stage III individuals mainly appeared from February to April. The average feeding grade of O.oratoria was 1.44, of which grade 1 was the most. The average annual condition factor index of O.oratoria was 1.226, and the male was slightly larger than the female.

Based on the data of fisheries resource survey by trawling from Minjiang Estuary and adjacent waters in Fujian in March,May,July,August in 2021,species composition,quantitative distribution,dominant species and community biodiversity characteristic of the fish were analyzed.Results showed that there were 104 kinds of fish in the investigated sea area,belonging 13 orders,46 families and 71 genera;among which the most species were Perciformes(50 kinds),followed by Clupeiformes(16 kinds).The temperature adaptability of fish was mainly warm water species,accounting for 70.19%,and the distributed water layer was mainly at the bottom species and the near-bottom species,accounting for 69.23% in total.There were 14 kinds of dominant species such as Coilia mystus,Parargyrops edita,Konosirus punctatus,and so on,most of them only occurring in 1 or 2 surveys,with significant seasonal differences.The fish stock density in weight and quantity were 667.10 kg·km^-2 and 71.91×10³ ind·km^-2,respectively,which were higher in summer than spring.The Shannon-Wiener biodiversity index of fish in Minjiang Estuary was at a good level(2.622).

In order to explore the selectivity of different mesh size codends of two-stick swingnet for Trichiurus lepturus in Eastern Fujian sea waters,4 mesh sizes(25,35,45 and 55 mm) codends were compared using covered net method in the autumn of 2019.The Logistic model was used to fit the selectivity curve of T.lepturus and the model parameters were estimated by maximum likelihood method.The results showed that:The L_0.5 of T.lepturus increased with the increase of mesh size,indicating that the increase of mesh size can effectively release T.lepturus.The relationship between the L_0.5 of T.lepturus and mesh size(m) was L_0.5=1.877m+45.323(R²=0.712).With the increase of mesh size,the weight escape rate and number escape rate of T.lepturus also increased,both of which were above 60%.

Based on the investigation of Branchiostoma balcheri resources in Xiamen Amphioxus Natural Reserve in August 2019(summer),November 2019(autumn),January 2020(winter) and April 2021(spring),this paper studied the resource status and the reasons for resource changes of B.balcheri,combined with historical survey data.The results showed that the average body length and weight of B.balcheri were 29.71 mm and 68.0 mg,respectively.The population was mainly composed of two years classes and three years classes,accounting for 76.2%.There were significant differences in the average body length and weight in the four quarters.The average density of B.balcheri in Eyu Island sea area was 50.0 ind/m²,which was the highest of the four sea areas in the reserve,but the range was very small.The average density of Huangcuo,Nanxian-shibaxian and Xiaodeng Island-Jiaoyu Island sea area were 4.1,1.5 and 0.4 ind/m²,respectively,which decreased significantly compared with the historical survey,especially Xiaodeng Island-Jiaoyu Island sea area did not appear basically.The change of habitat environment was the main reason for the decrease of B.balcheri resources in Xiamen sea area.