The correct answer is option 2: warm and cold currents meet. Fishing grounds are areas where fish and other marine species are abundant. These areas are usually found where warm and cold ocean currents converge. When warm and cold currents meet, they create a mix of nutrient-rich waters, which attracts plankton and other smaller organisms. This, in turn, provides a food source for larger fish and marine animals, making it an ideal location for fishing.

Option 1, high tides, is not directly related to the abundance of fish in fishing grounds. High tides occur due to the gravitational pull of the Moon and the Sun.

Option 3, low tides, also do not have a direct correlation with the presence of fishing grounds. Low tides occur when the ocean waters recede away from the shore.

Option 4, high stormy waves, are not necessarily indicative of the presence of fishing grounds. Stormy waves are caused by severe weather conditions and do not directly influence fish populations.

Therefore, the correct answer is option 2: warm and cold currents meet.