Tidal Range

Most coastal regions experience a semidiurnal tide, with two high tides and two low tides each day. However, the amplitude of each rising and falling phase may vary. We typically refer to larger tidal amplitude phases as the Major Tide, and smaller amplitude phases as the Minor Tide.

In addition, the tidal range of each segment refers to the water level difference between a consecutive high tide and low tide, which plays an important role in fishing and intertidal activities.

1. Major Tide vs Minor Tide

• Major Tide: Large tidal range, stronger water movement
• Minor Tide: Small tidal range, weaker water movement

Type	Tidal Range	Current Strength	Impact on Fish & Intertidal Activities
Major Tide	Large	Fast	Fish are more active; suitable for long casts; larger exposed intertidal area
Minor Tide	Small	Slow	Lower fish activity; suitable for bottom fishing or slow presentations; limited intertidal exposure

The tidal range of each segment directly influences current strength and exposed shoreline area, making it a key factor for predicting fish activity and intertidal opportunities.

2. Tidal Range of Each Segment

• Definition: Segment tidal range = height of a high tide − the adjacent low tide

• Characteristics:

  • Each tidal segment may have a different range
  • It is not equal to the difference between the highest and lowest tide of the day
  • Major tide segments usually have a larger range than minor ones

Example:

First high tide 3.5m → low tide 0.8m → range 2.7m (Major Tide) Second high tide 3.2m → low tide 1.0m → range 2.2m (Minor Tide)

3. Impact of Tidal Range on Fishing

• Large range (Major Tide):

  • Stronger currents, higher fish activity
  • Suitable for long-distance casting and fast-moving lures

• Small range (Minor Tide):

  • Calm water conditions, lower fish activity
  • Suitable for bottom fishing or slow presentations

Fishing tip: The period between high and low tide during a major tide is often the best fishing window. Minor tides are more suitable as supplementary fishing periods.

4. Impact on Intertidal Activities

• Large range (Major Tide):

  • Greater tidal retreat exposes more shoreline
  • Higher efficiency for collecting shellfish, crabs, and seaweed

• Small range (Minor Tide):

  • Limited tidal retreat
  • Smaller exposed area and shorter exploration window

Intertidal tip: Focus on major tidal ranges and retreat distances to maximize efficiency and safety.

5. Summary

• Large tidal range → stronger currents → more active fish → wider fishing/intertidal area
• Small tidal range → calmer water → lower fish activity → smaller usable area
• Understanding segment-based tidal range (rather than daily extremes) enables more precise planning for fishing and intertidal activities, improving both efficiency and safety.