The Goliath groupers are on their honeymoon. As a diver, you can use your dive time to do science and actively contribute to the conservation of these gentle giants. All you need to do is count fish. Here’s how.


Goliath groupers are critically endangered throughout their tropical and subtropical Atlantic ocean distribution. In the United States, a federal and state moratorium on harvest implemented in 1990 has allowed a slow path towards recovery from near extinction. Diving in Florida will allow you to see Goliath groupers during the most spectacular time of the year: spawning season.

Every year, from mid August to early October, Goliath groupers travel from around the state of Florida to congregate at a few sites along the Florida coastline (from north of Miami to the Jupiter area) for the purpose of breeding. These congregations are spawning aggregations. The peak spawning season is September. Goliaths remain for several weeks at the spawning aggregation sites checking each other out, and seeking potential mates with an elaborate courtship. Spawning occurs either at the full moon or the new moon (scientist are still looking into this).


You can dive for science if you know how to count fish and you can tell apart a light color fish from a dark color fish.

How to count fish like a scientist.

As you start your dive, count Goliath groupers every 10 minutes. You will count all the Goliaths around you, in a 360 degree field of view. To do so, you turn slowly around on yourself, like a little planet Earth rotating on its axis, counting as you turn, until you reach your starting point. You already learned to count numbers in kindergarden, so I will not elaborate any further. Why is this important? Because knowing how many fish you see at each dive site helps scientists like me to evaluate the health of the population

How to count colorful fish like a scientist.

As males and females seek each other out and engage in courtship they change their “color”, or in this species, their color “tone” from light to dark. There are 4 color phases (check out the photo below)

Normal (N) – typical brown blotches you see year round

Light (L) – The fish body is all white or very light

Dark (D) – the fish body is all black or very dark

Bicolor (B) – The fish has a white head and a dark body

Goliath groupers and their color phases. Photo Credit: Mike Phelan, Alang Chung

Goliath groupers and their color phases. Photo Credit: Mike Phelan, Alang Chung

Each color phase has an “assigned sex”, this means, scientists suspect what sex belongs to each color phase, but the groupers are not willing to provide a sample of their eggs or sperm as they pass by the unsuspecting scientific diver. For now, we think the Normals are males or females not engaged in courtship. Once the Goliaths engage in courtship, the Lights are females, the Darks are males, and the Bicolors are dominant males.

To count the number of Goliath grouper in each color phase, after your first count, you will do another 360 rotation around yourself, this time you are counting how many groupers in each color phase you see. It’s easier to look for the Lights, Darks and Bicolors as they stand out. Everything else will be Normals.  Why is this important? Because knowing how many Goliath groupers are in each color phase helps scientists like me to quantify how active is the spawning aggregation.

How to enter data like a scientist

1 – Bring a dive slate with you, with a pencil. The slate can be any size comfortable to you

2- On the top of the dive slate write DATE, TIME IN , DIVE SITE. You fill in that information after you complete the dive

3- As a reminder to yourself, under the date, time in and dive site lines, write down the color phases and their abbreviations,

N = Normal, L = Light, D = Dark, B = Bicolor

4 – Dive, dive, dive. Every 10 minutes count the number of Goliaths (your first 360 rotation) then count the number in each color phase (your second 360 rotation). Depending on whether you are diving air or nitrox, you will do 2 counts or 3 counts per dive.


Let’s say in your first rotation you count 10 Goliath groupers. You write down the number 10. On your second rotation you count 2 Lights, and 2 Darks (easier to see among the Normals). So right next to the 10 (your first count) you write 2 L, 2D, 6N.


Please email me the data

If you have photos or video of Goliath groupers, and you know WHEN and WHERE you took them consider sharing them with me for the purpose of science.

You are welcome to post comments here or email me your questions/comments

Safe diving ! Please, read the diving etiquette below.

Goliath grouper etiquette.003.003