Capture fishery profile of Diamondback squid Thysanoteuthis rhombus (Troschel, 1857) in Rizal, Palawan, Philippines

Abstract

The diamondback squid, locally known as “dalupapa,” is a high-value marine species commonly landed in Rizal, Palawan, Philippines. However, essential fishing information remains limited. Hence, this study provides the first documentation of the Thysanoteuthis rhombus (Troschel, 1857) fishery, specifically its focused were on fishing operation, seasonality, bait types, monthly catch per unit effort, gear characteristics, and fishing grounds. Data were collected through face-to-face interviews using printed questionnaires from 16 respondents with more than five-year experiences for diamondback squid fishing. All data were processed and analyzed using MS Excel, while fishing grounds were mapped with QGIS software. Fishing operations typically begin between 0300H and 0500H and end between 1300H and 2300H, resulting in a total fishing duration of nine to 18 hours per day. These operations occur five to 10 days per month, totaling 54 to 126 hours of fishing time monthly. Commercial fishing vessels with 3.02 to 9.03 gross tonnage are equipped with 52-160 jig sets, capable of catching 35-400 individual squid. The fishing season spans from February to November, with peak activity occurring between May and September. Commonly used baits include Rastrelliger kanagurta, Exocoetus sp., and T. rhombus fins. Monthly CPUE ranges from 0.03 to 0.08 kg/js/hr. Fishing gear typically consists of two jiggers attached to a hanger, with a 545 m long mainline connected to three Styrofoam buoys. Most fishing grounds are located in the southern part of West Philippine Sea waters. Further research is recommended to deepen understanding of the diamondback squid fishery in Rizal, Palawan.