Nassau Grouper (Ephinephelus striatus)

The Nassau Grouper is commercially extinct throughout much of its range. It has been red listed as an endangered species by the World Conservation Union, and is a protected species in US federal waters. In the Virgin Islands, Nassau grouper were reported in 1900 to be “..a common and very important food-fish, reaching a weight of 50 pounds or more.”  The fish is now commercially extinct in those same areas. The Bahamas and Belize have the last significant stocks of Nassau grouper in the world; it is up to us to ensure that we continue to have these fish for our future.

Groupers are very slow growing fish, and some species of grouper live to be over 120 years old. They are an important component of healthy marine ecosystems. Groupers have the unfortunate habit of ‘grouping’ together in the thousands to reproduce. These groups are called spawning aggregations. Nassau groupers form “spawning aggregations” at predictable places during the full moons in the winter months. 

Fishermen have long known about these aggregations and have targeted them- in the past with sailboats and hand lines, but now with traps, spears, big nets and satellite navigation equipment, many more fish can be caught. Many of the fish caught at aggregations have not yet had the chance to release their eggs. Some Bahamian aggregations that once had tens of thousands of fish now only have a few hundred, or have disappeared completely. The primary factor responsible for this drastic decline has been uncontrolled fishing when the fish are spawning. Failure to protect Nassau grouper spawning aggregations in Bermuda resulted in a 95% decline in the population, and commercial extinction of local stocks.  Many aggregations have been lost entirely, and there is strong evidence that once an aggregation has been fished out, it will not return.

Spawning Aggregations (SPAGs) are vulnerable to overfishing because

•          SPAGs are predictable in time and place

•          New fishing technology enables us to find and fish in more areas of the sea

•          Aggregation fishing targets large reproductively-active fish limiting their ability to reproduce successfully

•          Fish are often caught before they have had a chance to release eggs and sperm

•          Fishing at a SPAG can reduce the abundance of fish hundreds of miles away because the fish in aggregations swim hundreds of miles from the habitats in which they are found for the rest of the year to spawning site and then return to their territory. Grouper tagging studies indicated that Nassau grouper in the Exuma Sound aggregate hundreds of miles away in Long Island.

•          Adult fish cannot return home.

•          There will be less fertilized eggs to mature and replenish fish stocks

The Nassau grouper is the most valuable of our finfish species, with commercial landings valued at over $1.8 million in 2001. Bahamian grouper catches are showing marked signs of decline, and it is in our interest to protect this fish now.  We should have the foresight to learn from the mistakes of other countries; to do what needs to be done to protect the fish in our oceans and the people who depend on them. The Bahamian government put in place no-fishing zones around some of the grouper spawning sites during the winters of 1998-2000. This protection was discontinued in 2000 then restablished in 2004.

•          Closures during spawning season began in 1999/2000

•          Country-wide closed seasons:

–         January 1st-31st 2004

–         December 16th 2004-February 16th 2005

–         December 13th 2005-February 14th 2006

–         (High Cay Andros site closed 1st November-31st March from 2003 to 2006)

-       December  1st 2006 to February 28th 2007. The High Cay Andros site will be closed from November 1st 2006 to February 28th 2007. Read the Press Release from the Minister of Agriculture and Marine Resources, Hon. Leslie Miller MP.

- December 15th 2007-February 28th 2007. Read the Press Release from the Minister of Agriculture and Marine Resources, Hon. Lawrence Cartwright.

Any grouper species harvested during this period must be landed with the head, skin and tail intact.

What should we do? The Nassau Grouper is one of our most important food fish.  BREEF is following the recommendations of respected fisheries scientists from The Bahamas and abroad, and is calling for a closed season for Nassau grouper between 1st November and 31st January. A closed season will protect our fish while they are breeding. This is similar to the closed season that we have for crawfish in the summer.

• We need a closed season for Nassau grouper (like we have for crawfish in the summer) between    1^st November and 1^st March.
• We should support the implementation of a network of No-Take Marine Reserves and National Marine Parks. These will protect reproductive stocks of Nassau grouper and other marine life.
• We should include spawning aggregation sites within the boundaries of our marine reserves.

Nassau Grouper Links:

Studying Nassau Grouper Spawning Aggregations

NOAA Nassau Grouper Research

Green Reef Nassau Grouper Information

 Adult Grouper

Mature at 4-5 yrs, can live 20+ years and reach lengths of 48+inches. They feed on shrimp, amphipods, crustaceans, spiny lobster, spider crab, octopus and reef fish. Solitary—live in crevices in deeper  reefs.

Adult Grouper Spawning Aggregations

Form spawning schools during full moons from Nov-Feb when water temperatures fall below 26^oC (79^oF).May travel hundreds of miles to spawn releasing eggs and sperm into the water around dusk.

Larvae

Eggs (1mm) hatch about 23-40 hours after fertilization. Juveniles are pelagic: floating on currents, developing to a size of 1-1.25 inches over 35-50 days during which they are carried by flood tides to nursery habitats.

Settled larva

Early juveniles up to 10 months old settle to the bottom living in nursery areas such as creeks and  inshore algal beds up to a length of 2 inches

Juveniles

At about 2” they move to shallow patch reefs until adulthood when they move to deeper reefs.

Spawning aggregations  form during the winter months. Nassau grouper gather in large numbers to reproduce (spawn) at predictable locations and times making them vulnerable to overfishing.

Nassau grouper show four distinct color patterns in a spawning aggregations: the normal coloration, bicolor, white belly and dark phase. The normal or barred coloration is found in the morning, the bicolor phase occurs in both males and females in the early afternoon. The white belly phase occurs in females with swollen abdomens. The dark phase occurs in courting fish. Late in the afternoon, spawning occurs in groups of 3-25 fish, as bicolor fish follow a dark phase fish  releasing sperm and eggs into the water.

Dahlgren C. Nassau grouper: Life History, Biology & Ecology. Caribbean Marine Research Center.

Sadovy Y. Eklund A. 1999 Synopsis of Biological Data on the Nassau Grouper, Epinephelus straitus, and the Jewfish, E. itajara.