01Bigfin reef squid season concept and regional differences

Bigfin reef squid, commonly called spear squid, are cephalopods that are active at water temperatures 18–24 °C and reach their peak in June–September. In the South Sea region and Jeju region, the opening timing differs slightly due to temperature changes and current variations, which directly affect the choice of fishing trip timing.

In the South Sea, activity begins in early June once water temperature reaches 18 °C, while in Jeju the main harvest starts from late June to early July, coinciding with the northward flow of the current. This difference stems from regional currents (East Sea, South Sea, Jeju current) and depth variations (60–120 m).

Therefore, instead of a fixed ‘season start’ date, monitor local temperature and currents in real time and consider the period from mid‑June to the end of September as an ‘evergreen’ window where trips can be launched at any time.

South Sea region
Coasts of Jeollanam‑do and Gyeongsangnam‑do
60–110m
Water temperature 18–22 °C
Jeju region
Surrounding waters of Jeju Island
80–120m
Water temperature 20–24 °C
East Sea region
Coasts of Gangwon‑do and Gyeongsangbuk‑do
50–100m
Water temperature 19–23 °C

02Principles and key components of the Omorig rig

The Omorig separates the ‘Omori (sinker)’ from the ‘rig’, allowing the heavy sinker to descend first and quickly settle at the target depth. A 1–1.5 m leader is attached to the hook, letting it drift with the current and freely swim, naturally attracting spear squid.

Sinkers of sizes 15·20·25·30 are mainly used, with weights around size 20 (≈75 g), size 25 (≈90 g), and size 30 (≈110 g). In deeper water with strong currents, choose heavier sinkers; in shallow water with weak currents, select lighter sinkers for stable bottom placement.

Hook sizes are generally 2.5–4.0 in the South Sea region and 3.0–4.5 in the Jeju region. The main line is PE 0.6–1.2 with a fluorocarbon 12–20 lb leader attached for 1–1.5 m.

At night, use glow (luminescent) hooks to increase visibility, and in shallow water use natural‑color hooks to reduce wariness.

Sinker sizes
15·20·25·30
Sinker weight
75~110 g
Hook sizes
2.5–4.5
Main line material
PE 0.6–1.2
Leader material
Fluorocarbon 12–20 lb

03Practical application: depth, current, and time‑of‑day strategies

In deep water (80–120 m) with strong currents, combine a size 30 sinker with a 4.5 hook to achieve rapid descent and a wide search area. Conversely, in shallow water (60–80 m) with weak currents, use a size 20 sinker and a 2.5 hook for smooth movement.

When the current is strong, extend the hook leader up to 1.5 m to let the current carry it, allowing the spear squid to naturally pass over the leader. In weak or stagnant sections, keep the leader under 1 m to minimize hook mobility.

Set the time window to sunset ± 2 h as the ‘golden time’. During this period, diminishing light triggers active feeding behavior in spear squid, and glow hooks become highly effective.

⏱ Golden time
Sunset − 2 h
Quiet surface, start observing hook movement
Sunset ± 0 h
Light diminishes, spear squid become highly active, bites increase
Sunset + 2 h
Current weakens, capture the final bite before retrieving the hook

04Cautions and common oversights

The Omorig excels at detecting ‘pull‑type’ bites. Slightly trembling bites or upward‑bursting bites are not sensed, so minimize hook movement and focus on underwater sound.

If the sinker catches on the bottom or creates a vortex, the entire rig twists and fails to reach the target depth. Choose a slim long‑type sinker and adjust sinker weight according to bottom slope.

⚠ Common Mistakes
  1. Excessively lengthening the hook leader– Gets caught in the current, reducing bite sensitivity.
  2. Under‑selecting sinker weight – rig does not stay on the bottom in deep water.
  3. Using natural‑color hook at night – low visibility makes bites easy to miss.