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Grouper fish: Diet, Habitat and Reproduction of Atlantic Goliath Grouper

Grouper fish is one among the many species from the Serranidae family; heavy bodied and large mouthed saltwater fishes.  Grouper species are largely found in warmer seas.

Grouper fish

The common grouper types include but not limited to, Atlantic Goliath grouper (also known as Jewish grouper), the Giant grouper, Nassau grouper, the Red Grouper and finally the Dusky grouper.

Where do grouper fish come from?

You’ll find groupers between coral and artificial rocks in shallow tropical waters. They make their “homes” in those rocky bottoms where there are caves and holes.

Largely, it’s found in the Brazilian coast and most of the Caribbean as well as the Mexican Gulf and the Florida Keys of the U.S.A.

In the eastern Pacific Ocean, from the Californian Gulf to Peru, it can also be sighted.

Moreover, the eastern Atlantic Ocean from Senegal to Congo is another of places where it can be found. Additionally, it still can be found in Canary Islands though very rarely.

Its ideal habitat is inshore shallow waters upto about 150” (46m) depths.

What does grouper fish look like?

Well, they have dull colors mostly greenish and brownish. However, some are somewhat brighter with others having bold patterns.

Amazingly, Nassau Grouper (Epinephelus striatus) is infamous for its ability to change to several color patterns.

However, there are grouper fish that inhabit deeper waters, for example the black and yellowfin groupers. These have more of red coloration in comparison to those whose habitat is near the shore.

It is broad headed with small eyes on an elongated and broad body, with its widest part measuring over a half of all of its body length.

Its large mouth has jawbones that extend past its small eyes. Its body has 5 dark bands/stripes which are mostly noticeable on baby groupers.

It has continuous dorsal fins. In addition, the first dorsal fin spines are shorter than the rays of the soft dorsal.

Pelvic fins appear smaller than the rounded pectoral fins. The caudal fin is similarly rounded.

Also, scales and thick skin cover soft dorsal and anal fins bases. There are notches on the membranes of the dorsal fin elements.

Of the Atlantic groupers, Goliath grouper (Epinephelus itajara) is the largest measuring about 8.2” (2.5m) and tipping the scale at about 800 pounds (363 Kgs).

How do grouper fish reproduce?

They have relatively slow growth rate. As a result, only after about 5 or 6 years and about 36” in length is when they reach reproductive maturity age.

While full maturity size for females is at about 48” – 53”, males are however at a smaller size of about 42” – 45”. Besides, their maturity age is also slightly younger than that of females for whose it’s about 6 – 7 years.

The table shows how its slow growth is phased:

Growth phases0 – 6 Years7 – 15 YearsFrom 25th Year
Appx’ Annual Growth (inches)4 inches1.2 Inches0.4 Inches

Mostly, grouper species are psychotic protogynous hermaphrodites; meaning, they firstly mature as females but after sexual maturity, they are able to transform their sex into males. 

Harems of about 3 – 15 females are usually under the control of the largest males.

Competitive exclusion of large males from reproducing smaller males is enabled by spawn addition.

Following that, the decline of fitness of a small female grapper happens. This is only if it begins to change sex prior to controlling harem like a male first would.

In short, the biggest female will change its sex besides increasing its fitness where there is no fit male available.

Goliath grouper form spawning groups known as spawning aggregations of about 100 or more individuals.

Reproduction is always soon after full moons; July – December. From inshore reefs, they’ll even move upto 100Kms (62 miles) to the spawning sites.

The perfect and preferred spawning sites are ship wrecks, isolated patch reefs as well as rock ledges.

Because they are dispersal spawners, reproduction while in these sites is through broadcast spawning method. This is essentially females releasing eggs and males all in one go releasing sperms into the water column.

This method enhances the chances of successful eggs fertilization. In addition, it also reduces chances of eggs predation.

Water currents disperse the pelagic eggs after fertilization. On hatching, the 2nd dorsal and pelvic fin spines are well elongated on the kite-shaped larvae.

In about 25 – 26 days post hatching, the now 1” (2.5 cm) pelagic larvae transforms into benthic juveniles.

How long do goliath groupers live?

On record, the oldest known and verified Goliath grouper lifespan is 37 years. Only 6 years shy of the oldest know goldfish record 43 years held by Tish. However, it’s estimated that grouper fish can even hit 50 year mark.

Just like counting rings on a tree trunk for age estimation, the age of grouper fish can likewise be estimated by annual growth rings count on its dorsal fin rays.

They were however nearly decimated by the overfishing using spear and line till they were classified as legally protected species.

Well, it’s been adjudged by some as its “own enemy” with regards to its population decline. Below are its possible contributions towards that; 

  • Firstly, during preparation for spawning, they gather in their hundreds in wrecks and reefs. It is in this environment that food and shelter is in abundance. This however avails a good opportunity for their catching because they won’t budge. In any case, they are slow swimmers.
  • Secondly, besides taking long to mature and reproduce, pollution and coastal developmental activities by humans affect the mangrove forests, critical for their survival. It’s in these forests where juveniles hide from predators prior to moving to the reefs.  
  • Further, besides being a victim of trophy hunting that thrilled many a sportsmen to overpower the giant grouper fish recreationally, it also was a common and popular delicacy. These 2 factors almost made it extinct in the “80s.
  • High build-up of mercury in their system, liver in particular has also contributed in the plummeting of their numbers. The bigger it gets, the high the toxic levels.
  • Additionally, some female goliath groupers, Baitfish cloak for instance will feast on as many eggs as possible after the male releases sperms on the laid eggs. This subsequently reduces the eggs that would eventually hatch.

This though contributes in a small way to their slow population growth.

What do goliath groupers eat?

Naturally, they never actively hunt down a fast swimming prey because they are opportunistic predators.

It feeds on crustaceans; for instance calico crabs, sea turtles and even barracudas. These, almost exclusively make up goliath grouper diet at about 80%.

Additionally, small and slow fish targets like catfish, toadfish and burrfish make about 20%.

That said however, it will not pass on a fish caught on a fishing line and any other struggling fish.

Its rapid expansion of the mouth aids in sucking in ambushed prey and subsequently swallowing it whole.

Do goliath grouper have teeth?

Well, their dentation is such that they have just but a few teeth (3 – 5 rows of teeth) on the lower jaw edges.

These teeth are tiny and re-curved; just enough for holding the food/prey within the mouth cavity but not to bite.  However, their pharynx has heavy crushing tooth plates for crushing before swallowing. As a result, they don’t bite. 

Do goliath groupers bite?

The answer is NO! They don’t.

In-fact, out of their opportunistic nature and ambitiousness, they sometime may mis-judge the size of a prey. Subsequently, they will not fully swallow it in one go. As a result, the part of prey left dangling out will only be fully gulped when the swallowed bit is digested. 

How much does a grouper weigh?

Before answering that, it’s best to start by knowing, how many types of grouper fish are there? (Some of the types have been enumerated here above on this article).

Well, it’s worth noting is that this grouper species has in excess of 100 varieties. Subsequently, while they are all heavy bodied, their weights vary from one grouper fish to another.

However, the Goliath grouper for instance can weigh upto 800pounds.

Are goliath groupers good to eat?

Well, this is another concern with most. However, some smaller types of groupers are. In-fact, their being a delicacy back in the days contributed to their near extinction.

So, yes, there are some good and safe choices; for instance, halibut, snapper, yellowfish tuna, mahi mahi as well as bluefish grouper are safe choices.

Again however, as sited above as one of the reason for their numbers decline is the toxic mercury build-up in them as they grow. As a result therefore, you’d want to be safe to avoid them. Swordfish, King mackerel and marlin are particularly to be completely avoided because of insidious toxic mercury.

What must be remembered however is, just like with any fish meal, ensure it is properly prepared and well cooked.

How big do goliath grouper get?

Grouper fish can grow to 8” or there about.

However, another of goliath grouper fish (E. lanceolatus) relation, the giant grouper fish which is a native of Pacific and Indian Ocean measures about 8.8” (2.7m) in size.  It probably is the biggest grouper ever caught.

Are groupers dangerous?

While they have been known to stalk divers, they are however not known to attack. Yes, they are immense sized but in the meantime, they are also nonthreatening. Scuba divas will attest to this. That is however not to say they shouldn’t be treated with caution.

You may also be asking, are Goliath groupers aggressive? Well, it depends on prevailing circumstances. That is a good answer to that.

Adults are territorial (especially when in its refuge areas; the ledges, wrecks and caves), solitary and overly inactive when not feeding or spawning.

However, when it feels threatened, it will make rumbling sounds from its swim bladder (caused by muscular contractions) as well as assume an aggressive body language.

Amongst its few known predators are barracuda, moray eels and king mackerel. They however only prey on the grouper fish before they are fully matured.

When fully matured, their only predators are large sharks and obviously but sadly, humans.

Grouper fish facts summarized:

  1. As they age, Groupers undergo sex reversal. They are all born females later transforming to males. However, most remain females because few live long enough to transform to males.
  2. Just because of their sheer big size, they’ll suction in small prey when they open their mouths.
  3. They swallow their prey whole, however big. They’ll crush it with the heavy tooth plate in their pharynx. Their tiny teeth are not to bite.
  4. Atlantic Goliath Grouper can and does grow so big that some believe it’s the same one that swallowed Jonah the Jew of the bible. Infact, some believe that was the source of its former name, the Jewish grouper.
  5. United States Navy ones named one its submarines after it. From its launch on the 27th Oct 1941, it served till it was decommissioned on 11th Aug 1970.
  6. They have a massive and powerful dive pull although they are slow swimmers. Besides, they are incapable of doing long swims.
  7. Some Groupers are able to change their colors for camouflage and blending with their environment.
  8. They can well tolerate low oxygen levels to live in brackish waters.
  9. They are a “No take” Species. This is because they are legally protected. In-fact, you’d better be caught with marijuana than with a grouper fish.
  10.  When it’s spawning time, they’ll move upto 100 miles.
  11.  The mercury levels in their system, especially as they grow big make them unsafe for human consumption.

Conclusion:

Thanks to protection, Grouper fish population is steadily growing and easily traceable. As a result, this is making it endearing to many scuba divers seeking the thrill that come with being amidst the robust yet nonthreatening fish.

The feeling is magical to anyone who dares.

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