Improving the accordion-shaped trap selectivity for black rockfish by mounting escape vents: A case study from the small-scale fishery in Shandong, China

摘要

Sustainable development of small-scale black rockfish (Sebastes schlegelii) resource has received little attention in Shandong, China, although this species is an important source of income for local fishermen. Accordion-shaped traps with a mesh size of 2 cm are currently used; however, they present poor size selection and effect fishermen's ability to effectively utilize the black rockfish resource. In this study, we explored a method to improve the size selectivity of traps by mounting escape vents at the ends of each trap. The selectivity of accordion-shaped traps with escape vents of size 6, 7, and 8 cm was tested using a catch comparison method. A theoretical Mature Body Length (MBL) of 15 cm was defined as the reference point to support the interpretation of results. The results demonstrated a decrease in the retention of immature fish with the enlargement of escape vent size. Based on the retention rate and estimated percentage of individuals below and above the MBL, the 6 and 8 cm escape vent sizes were not considered appropriate for sustainable fishery. However, the 7 cm escape vent size was found to retain most of the mature black rockfish, while releasing the majority of immature black rockfish; hence, it can be considered a gear option for sustainable resource utilization. The results of this study can be used to formulate management regulations for small-scale fisheries in China.