Toxic 'Red Tide' kills 4.2 million fish

84531dc6-7943-4c08-b602-20d45d6ed301

Editor's Picks
Features Post
What caused this snail die-off?
04 January 2022
Fishkeeping News Post
Nanochromis transvestitus
04 January 2022
Features Post
How do I feed these tricky gobies?
04 January 2022
Features Post
Should I add sand for my Rams?
04 January 2022
Features Post
How to set up your Christmas tank
20 December 2021


A vast tide of microscopic red algae off the coast of Texas is thought to have been responsible for the deaths of 4.2 million fish since September.

The 'Red Tide' is a regular occurrence in the Gulf of Mexico during the autumn, but this year's deadly bloom is one of the largest seen and especially destructive to the Gulf's wildlife.

It's thought that algal levels have reached such deadly proportions due to the record breaking drought that Texas has suffered recently, with the combination of temperature, rising salinity and nutrient levels associated with the arid conditions all thought to be contributing factors.

The algae responsible, Karenia brevis is not only potentially deadly to fish, but the toxins it contains can become concentrated within the tissues of shellfish such as oysters, mussels, scallops and whelks and if these are eaten by humans can cause neurotoxic shellfish poisoning (NSP).

While there have been no reported fatalities from NSP, victims have been frequently hospitalised with symptoms including nausea, vomiting and slurred speech.

With these facts in mind the Texas Department of State Health Services has banned both the commercial and recreational harvesting of shellfish in the area.

Officials have also reminded the public that the toxin can become airborne close to the sea in rough conditions and while most people would only suffer 'nuisance' symptoms such as coughing and sneezing, people with asthma or other lung conditions may be more severely affected so should bear this in mind before visiting the coast.

The deadly blooms are usually broken up, dispersed and destroyed by a combination of rain and cold temperatures but with no end in sight for the drought it's not known when these conditions will occur to end the problem, and how many more fish will die in the meantime.

Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.