This study documented the fishing grounds and seasonal availability of the diamondback squid (DBS) (Thysanoteuthis rhombus) along the southern Tañon Strait region of southwestern Cebu, Philippines, using purposive sampling of 105 fishermen across seven municipalities. All respondents had prior experience in capturing T. rhombus using a gear specifically designed for the species. Findings revealed that DBS fishing grounds spanned from the Municipality of Barili to Santander, with Barili emerging as the most prominent site. DBS fishing was also noted in Carcar, marking the first fisher-reported records of DBS in Cebu Strait. Respondents commonly used motorized boats (0.3–0.39 GT) with 6–10 HP gasoline engines, consuming 1–2L of fuel per trip. Fishing lasted 7–11 hours, typically conducted solo during daylight hours. The peak DBS season was observed from March to early August, with May yielding the highest catches—typically 1–10 pieces per trip, each weighing 1–10 kg. A lean season occurred from late August to February, with October having the lowest catch rates and most operations reporting no catch. Respondents noted a general decline in DBS catches from 2021 to 2022, coinciding with the COVID-19 pandemic. However, some fishermen linked the decline from 2011 to 2020 to excessive fishing effort and the use of the “multiple jigs in a line” method. While various causes were proposed, most attributed the decline to the species’ natural seasonal behavior. The findings offer baseline data for resource assessment and highlight the need for adaptive, season-based management to ensure sustainable catches.
