Giant behaviors from giant fish

Lab Note #4
Apr 13, 2015

Hey guys!

Sorry it's been so long since my last post but I figured today would be a great day to start spamming you with updates again as I am preparing for my second field season out in Catalina!

Last summer I found at that giant sea bass are really awesome fish that do some really cool things:

Giant sea bass change color! Just before courting I began to notice this sort of sexual dimorphism (changing color before sex). Females that are carrying eggs tend to be very rotund would become much darker in color and the males would become much lighter in color. It's believed that this is a sign that they are ready to reproduce and courting can begin.


I was able to observe some courting! Giant sea bass courting is very similar to courting in other fishes. The two most common things I saw were circling and nudging:

This is circling. It's very simple but its really awesome to see.

The female leads in a circular pattern and the male follows. As they continue on the circling becomes fast and faster which may lead to a spawning rush (I think). What is cool about circling in GSB is that they seem to prefer to do this in pairs. When a second male tries to come in and join in this behavior the males start to display aggressively toward each other. On a few occasions the male that was circling initially, would charge at intruders getting them to back off and even charged at my dive buddy and me!

The second behavior that was very common was nudging.


Nudging would only occur during circling and it is when the male would nudge at the anal fin of the female, essentially lifting the female into the water column. This is thought to be a their way of saying "hey lets do this, I'm ready to spawn."

Unfortunately I was unable to see any sort of spawning last season, but I do know what "should" happen. In other fish species that do similar behaviors, they start with circling and as it becomes faster the males begin to nudge more and more, eventually getting the female to rush toward the surface to release her eggs and the males follow releasing their sperm at essentially the same time.

With the knowledge I have gained I think this summer will be a different story and spawning will be seen and you guys will get to see it as well.

Another note is going up as well talking about sound stuff so check that out!

Let me know if you have questions! I would love to answer them.

Check out my blog (I update it a bit more frequently than I do here) thatfishkid.tumblr.com and get ready for more updates as I get closer to giant sea bass summer round 2!

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