01Impact of Heatwave on White Croaker Behavior

In July, the West Sea’s daily high temperature approaches 33 °C, and surface water often exceeds 24 °C.

According to data from the National Institute of Fisheries Science (NIFS), white croaker’s active period is optimal between 18–24 °C, and activity sharply declines and feeding diminishes when water temperature exceeds 25 °C.

Therefore, during heatwaves the fish’s habitat layer tends to shift from shallow depths to the deeper 60–120 m zone.

This temperature rise raises the white croaker’s metabolic rate and oxygen demand, but as water warms, dissolved oxygen drops, increasing stress.

In midsummer heat, perceived temperatures rise sharply, so adequate hydration before and after the trip plus shade and cooling gear are essential.

Target temperature
18–24℃
Optimal Depth
60–120m
Recommended line sizes
PE 4~6 go
Leader Material
Carbon 8~12 go

02Heatwave Basic Equipment Checklist

⚠ Common Mistakes
  1. Ignore water temperature and stay in shallow water: white croaker moves to deeper depths
  2. Neglecting water intake leads to rapid dehydration and fatigue
Southern West Sea
Jeollanam-do·Busan
60–120m
July–September
Central West Sea
Chungcheongnam-do·Incheon
70–130m
July–October
Northern West Sea
Gyeonggi-do·Gangwon-do
80–140m
July–October

03Tide and Optimal Spot by Time of Day

According to the Korea Meteorological Administration’s marine weather information, in July the West Sea experiences its strongest tides about two hours before and after sunrise and sunset, creating strong water flow. Particularly, the ±2‑hour window around sunset is a ‘golden time’ when white croaker’s feeding activity surges, and the fish rapidly ascend to shallower depths.

At this time, using surfcasting or boat‑mounted down‑shot rigs can effectively target the fish’s vertical movement.

⏱ Golden time
Sunset − 2 h
Surface flow weakens·white croaker ascent begins
Sunset ± 0 h
Rapid ascent at 60–80 m depth·maximum catch potential
Sunset + 2 h
Surface flow recovers·white croaker descends again

04Heatwave Response Practical Tips

First, measure the on‑site water temperature for 30 minutes before departure and set a small line 10 m deeper than the target depth to monitor temperature changes in real time.

Second, when the fish ascends, avoid sharply increasing line tension; instead follow the fish with a smooth retrieve, minimizing dehydration risk while maintaining catch rates.

Third, within 15 minutes after the trip, replenish water and electrolytes and perform cooling stretches to greatly help prevent dehydration and heatstroke.

‘On extremely hot days, fish move to deeper waters. Matching depth is the key to success.’ – NIFS research team