Squid jig types, composition and CPUEs, utilized in diamondback squid (Thysanoteuthis rhombus) fishing along southern Tañon Strait, Philippines

The study examined the fishing practices and efficiency in catching Thysanoteuthis rhombus, or diamondback squid (DBS), in the southern Tañon Strait region of southwestern Cebu through a survey conducted in DBS fishing communities across seven municipalities. In the study’s locality, DBS presence has been noted without comprehensive understanding of its fishery and technology. From responses of 105 DBS fishermen, the study found two primary gear types used: “single jig in a line” (SJL) and “multiple jig in a line” (MJL), both featuring manually crafted squid jigs with integrated sinkers, 151-200m monofilament nylon mainlines connected to buoyant polystyrene spools and brightly-colored flag markers, and attachments affixed to the mainlines such as blinkers and bait; with MJL being distinctly equipped with five jigs spaced every 1-10m. Among the two, SJL is predominantly used by respondents. CPUE analysis indicates SJL’s overall higher efficiency, with CPUEs of 0.49 kg/jig/hr, 0.63 kg/jig/hr, 1.07 kg/jig/hr, and 0.67 kg/jig/hr during 1991-2000, 2001-2010, 2011-2020, and 2021-2022, respectively. MJL type showed CPUEs of 0.81 kg/jig/hr, 0.62 kg/jig/hr, 0.63 kg/jig/hr, and 0.75 kg/jig/hr during the same periods. Despite varying CPUEs, both gear types showed higher CPUEs in DBS fishing compared to previous DBS exploratory studies in the country. However, there’s a notable decline in the average weight per caught individual over the decades, prompting respondents to increase fishing efforts since 2011. The study suggests that assessing the population dynamics of DBS along the Tañon Strait is crucial for ensuring the sustainability of this resource. published by the Journal of Biodiversity and Environmental Sciences | JBES