Algal Blooms and Their Effect on Fish

From time to time the water off our coast turns cloudy green or brick red, and the first question every angler asks is: is the fish safe? This is an algal bloom, often called red tide. It is a natural phenomenon that peaks in warm-water seasons, but it is worth understanding properly before you launch or eat your catch.

Why blooms happen and how to spot them

• Warm water and high surface temperatures through the summer months.
• Nutrient loading (nitrogen and phosphorus) from discharges and land-based sources.
• Currents and stagnant water that prevent flushing and trap the bloom mass in place.
• Calm winds and clear skies, ideal conditions for rapid growth.

The visible signs start with colour: thick green, muddy brown, or brick red, and the denser the colour the more suspect the water. It is often accompanied by surface foam, a strong smell resembling rotting fish or sulphur, and murky water with suspended particles that foul your bait. In severe cases dead fish float up or behave oddly near the surface, because oxygen drops and some species release toxins that damage the gills.

Effects on fish and fishing

As a bloom develops, fish behaviour changes: they move deeper seeking oxygen, vanish from shallow edges, and feed less aggressively, so bait response drops and fishing slows. In advanced stages, mass mortality occurs in enclosed basins, creeks and poorly flushed areas. On eating your catch, any fish taken from affected water deserves caution: some species accumulate toxins in their tissue, and shellfish are the highest risk category because they filter water continuously. That said, there is no need to panic: blooms are seasonal and usually break up once weather changes and water renews.

What to do

• Avoid known bloom areas and do not fish inside foam or discoloured water.
• Wash your catch in clean water and gut it immediately rather than later.
• Buy from trusted, traceable sources, not unknown sellers inside an affected zone.
• Report fish kills and unusual colour changes to the authorities.
• Follow official bulletins rather than rumours in group chats.

To be clear: final health recommendations, and clearance to fish or eat from a specific area, rest with the relevant official authorities. This article is guidance for anglers only.

Plan your trip smartly

Before starting the engine, check sea state and wind, because long calm spells combined with warm water are the bloom's breeding ground. B7R gives you tide tables for Shuwaikh and Shuaiba ports, sea state, a fish guide, a catch log, seasons, navigation tools and an SOS emergency button — free on Google Play, and it helps you track changing conditions and decide whether to go or wait.

The bottom line: read the water before you run, log your observations in your catch log, and report anything unusual. Download B7R and keep it updated: B7R on Google Play.