01Cold‑Water Olive Flounder Ecology and West Sea Spawning Characteristics

Olive flounder (Paralichthys olivaceus) is a left‑eyed flatfish with both eyes on the left side of the body, inhabiting coastal sand and pebble bottoms at depths of 10–200 m. In the West Sea coast it spawns from February to June when water temperatures are 11–17 °C. Females finish spawning in April–June, males in March–June, and when the temperature exceeds 15 °C (usually mid‑May) they move to shallow coastal waters to begin feeding. Therefore, in June the water is still cool, and olive flounder are actively moving in relatively shallow depths (above 20–40 cm), making a downshot rig most effective.

Sinker
25–40 go (112–150 g)
Hook
3/0–4/0 straight hook
Soft bait
4‑inch minnow/shad tail (white, red, chartreuse)
Leader
Carbon 8–12 go (30–50 cm)

02Downshot Rig Principle and Precise Setup

Downshot rigs fix the sinker on the bottom and attach a leader above it, suspending the soft bait 20–40 cm off the substrate. Olive flounder prey on prey passing 20–40 cm above the bottom, so the bait must pass through this layer for a high bite rate. Adjust sinker weight according to current strength: for currents of 0.5–1.0 m/s use 30–35 go, and for 1.0–1.5 m/s use 35–40 go. Leader length is set between 30–50 cm depending on tide and depth. When activity is high and the bait moves quickly, set the leader to 30 cm for rapid response; when activity is low, extend it to 45–50 cm so the bait stays longer in the bottom layer.

West Sea coast
Olive flounder habitat
20–80m
May–October
North‑western South Sea
Shallow‑depth coast
30–100m
June–September
Offshore breakwater
Deep water
80–150m
July–October
⏱ Golden Time
Dawn 04:00–06:00
Below 15 °C, cold‑water olive flounder move to shallow depths and bite actively
Morning 09:00–11:00
Weak current makes sinker placement easy, focusing early bites
Evening 18:00–20:00
Around sunset ±2 h, olive flounder actively search for food, peak bite frequency
⚠ Common Mistakes
  1. Underestimating sinker weight causes the rig to lift with the current, leaving the target depth and reducing bites.
  2. Setting the leader too long allows the bait to touch the bottom and disappear, lowering bite rates.
  3. Water temperature above 22 °C maintaining the same rig causes olive flounder to move to deeper water, making them harder to catch.

03 Practical Application and Safety Tips

In June cold‑water conditions on the West Sea coast, first check the Korea Meteorological Administration marine weather forecast. Days with wind speeds of 5–10 knots (2.5–5 m/s) and wave heights of 1–1.5 m are optimal, and select a current forecast of 0.5–1.0 m/s. For safety, stay hydrated to prevent seasickness, and wear anti‑slip shoes near rocky shores to avoid slipping on breakwaters. After setting the rig, verify that the sinker is firmly anchored and that the bait is floating precisely 20–40 cm above the bottom. When bites begin, reel in smoothly to keep the bait moving; if the bite intensifies, pull the line sharply to lift the hook. Finally, store the caught olive flounder immediately to avoid rapid temperature changes, and after the trip release it back to the sea or handle it appropriately.