Grand Cayman Island: Sergeant major nest at Devil’s Grotto July 21 2022

Towards the end of the dive I was hanging out under the boat and started watching a Sergent major fish. They are common throughout the Caribbean and I have seen hundreds (maybe thousands) of them over the years. But it’s still interesting to observe their behavior, especially when it comes to their nesting.

Wikipedia says, “The sergeant majors is an oviparous species in which the males create nests where the females to lay their egg masses on rocks, reef outcrops, shipwrecks, and pilings.^[5] The males actively chase the females in courtship before the female releases approximately 200,000 ref, ovoid eggs which are attached to the substrate by a filament”

Reefnews.com does a good job explaining what happens next,

After building this nest, the male Sergeant Major will stay near the nest for several days to guard the eggs until they hatch. The female will leave during this time. The male will chase away all other fishes to keep the eggs from being eaten. The male Sergeant Major can be very aggressive during this time, and will even attack people in the water if they accidentally get too close to the nest. Although the Sergeant Major probably couldn’t hurt anyone, it will fearlessly try to drive away anybody that it thinks is too close to its nest.

http://www.reefnews.com/reefnews/photos/sgtmjr02.html

Whitespotted Filefish in Cozumel on July 19 2021

During one of the dives on July 19th I encountered a pair of Whitespotted Filefish.

A page from the Dive Paradise website tells us, “They have scales, although very small, and feel like sandpaper – not dissimilar to a shark’s skin. This roughness is how the Filefish got its name. Reportedly their dried skin was once used to finish wooden boats.”

They go on to say,

Every Filefish has a sharp spine on its head just above its eyes. It erects the spine when threatened as a defensive move. Its primary defense is to erect its dorsal and pectoral fins plus the spine to make it difficult for a predator to eat or to extract from its hiding place if back in a little cave.

https://diveparadise.com/2017/11/05/american-whitespotted-filefish-cozumel-reefs/

It looks like I made the darker filefish nervous since it’s spine was up as it approached me, and what I assume is it’s mate. Since both sexes can change color, that’s not a good way to tell which is the male and which is the female. The website says, “It is difficult to differentiate between males and females. The male fish are said to have slightly larger appendages extending from their bodies at the base of their tails.”

When the orange colored filefish turned it’s tale towards me I can see what I think are the “appendages extending from their bodies at the base of their tails.” Although it’s still difficult to tell for sure, this would make the orange colored filefish the male.

Queen Triggerfish in Cozumel, Mexico on July 21, 2021

It took me most of the week to get a good video of a Queen Triggerfish. Notice how it changes color as it swims by. Since many of my favorite fish can change color, I became interested in learning how it happens.

The New World Encyclopedia tells us,

Chromatophore is a pigment-containing and light-reflecting cell, found in various invertebrate and cold-blooded vertebrate animals, that can help bring about changes in color or brightness in the organism. Among animals with such cells are various crustaceans, cephalopods, amphibians, fish, and reptiles. Through aggregation or dispersion of the pigment and reorientation of reflective plates in single cells (in most animals) or through the muscular movement of complex chromatophore organs (in cephalopods), the color or brightness of the entire organism or part of the organism can change, which is useful for camouflage, signaling, temperature regulation, and protection from radiation.

https://www.newworldencyclopedia.org/entry/Chromatophore

It looks like this Queen Triggerfish was changing color to blend with the surroundings for camouflage.