The Goliath Grouper big fish in trouble

The Goliath Grouper, Epinephelus itajara, is the largest grouper found in the North Atlantic. The goliath grouper lives in the tropical and subtropical waters from the coastal waters of Brazil up through the Caribbean into the Gulf of Mexico and the waters surrounding the Florida coast. Adult goliath groupers are at least one meter in length and can reach two meters long weighing in excess of 800 lbs (455 kg).

These huge fish take five to six years to mature. When they are sexually mature adult goliath grouper mate and spawn at known spawning grounds. The aggregation of large numbers of the fish in a small area during the spawning season attracted commercial and sports fishermen to the species.

By the 1990s, the fish numbers had dropped to such low levels that fishing for the goliath grouper was no longer economical. In 1991, the goliath grouper was placed on the IUCN Red List for endangered species as critically endangered.  United States banned the fishing for goliath groupers in its waters in 1990. The Caribbean banned goliath grouper fishing in 1993.

With fishing no longer affecting its numbers, scientists searched for other potential threats to the goliath grouper.

The immature fish do not live out in the ocean with the adults. During the first five to six years of its life, the young grouper lives in the waters of the mangrove swamps Mangrove swamps are changing owing to human interference. Some swamps are being destroyed to make way for agricultural and housing developments. Mosquito control measures and water drainage projects from the Everglades have both impacted heavily on the Florida mangrove swamps. The loss of the waterways making up part of its nursery will not aid in the recovery of goliath grouper numbers.

The waters around Florida are subject to red tides. Algal blooms cause these tides. A rapid increase in dynoflagellates of the species Karenia brevis is responsible for the marked color change of the sea. As well as changing the color of seawater, Karenia brevis produces a neurotoxin, called brevetoxin, which is deadly to many fish. After a red tide, dead fish are washed up on to the beaches. Scientists from National Oceanic and Atmosphere Administration (NOAA) examine these fish to ascertain which species are threatened by red tide events. Unfortunately, one of the species found washed up on the beaches is the goliath grouper.

Reference sources:

Florida State University Koenig and Coleman Laboratory

The Marine Genomics Project

NOAA South East Fisheries Research Center