[About the Sea 15] Diving on a day that felt like early summer both on land and underwater, I was able to observe plenty of biological reproduction

Hello.
My name is Fumiya, a company employee and diving instructor living in Fukuoka.
I mainly dive in the Genkai Sea, such as Shikanoshima and Karatsu, and occasionally in northern Kyushu areas like Nagasaki.
The shop I usually go to is called Dive Shop Sunrise.
For anything related to the seas of northern Kyushu, head to Dive Shop Sunrise.

This was on May 14th.
(I'm writing this in a hurry, surprised that over a week has already passed)

The weather was nice that day, with temperatures over 25°C, making it a day that felt like summer had arrived early before the rainy season.

Underwater, the shallow areas looked like this.
The water gets murkier as you go a bit further in; that's typical for Shirase at this time of year.

The water temperature reached 19°C, and as it rose, the wakame seaweed fronds began to melt or get munched on by sea hares, leaving many with only their stems remaining.

The peak season for the fronds has come to an end, and now it is the breeding season.
The mekabu, which are the reproductive organs, are growing vigorously.

The folds of the mekabu, the reproductive organs of the wakame, are the perfect hiding place for small creatures.
When you peel them back a little, you can see small fish, shellfish, and crustaceans scurrying away in a panic, like children whose secret base has been discovered.

You can also see the breeding process of Sargassum horneri, which showed us a magical scene last time.

Sargassum horneri plants are either male or female, and the eggs attach to the female reproductive receptacles (the parts that look like fruit).
I intended for this to be my best shot, but setting aside my frustration at being unable to focus properly underwater due to my worsening presbyopia, I am impressed by how each type of seaweed has its own way of reproducing.

It's not just seaweed that is breeding; fish are too.

As I wrote in "The story about how seahorses are cute,"seahorses are basically monogamous.
The one with the swollen lower belly is the male.
He is raising the eggs in his brood pouch.

And what I saw for the first time that day was a Japanese pygmy filefish protecting its eggs.

Just like with the seahorse's brood pouch, it is often the male who is responsible for protecting fish eggs.
This is a survival strategy where the female conserves the energy she spent producing the eggs, while the male ensures the next generation survives by keeping them in a safer place and using safer methods.

However, it seems that for the Japanese thread-sail filefish, the female protects the eggs.
Moreover, since these eggs hatch in just about three days, it means I was able to witness a quite rare scene.
It was my first time seeing it, and I was moved.

I often observe Japanese thread-sail filefish because it's cute to see the little ones schooling, and once they become adults, they tend to drop in priority as subjects of observation, but when I see scenes like this, it makes me realize I need to observe them more carefully.

And speaking of Shirase, there are sea slugs.
The aeolid nudibranchs that had been bustling since winter have disappeared all at once, making me feel the change of seasons.

From now until summer, the underwater world will surely change its appearance even more.

Recently, I've been so busy with work I don't even want to do that my opportunities to go to the sea have drastically decreased, so while it's necessary to cherish every single dive, it was a day that made me think I want to keep my work in moderation and go diving so that I can properly feel the changing seasons in the sea.

The end.

My note is themed around "Things about the sea, things about travel, and random thoughts."
Please read my other posts if you'd like.