Bullseye jawfish are brooding their eggs in the "Baja California" tank. Notice the jawfish's mouth as it peeks out from its burrow at the bottom of the tank! It's holding an egg in its mouth. This brooding behavior is the male's responsibility. The eggs, protected and nurtured in the mouth, will hatch in about eight days.

The tank displays two males and two females, but interestingly, it's always the same male that practices mouthbrooding.

The first observation of mouthbrooding was in September of last year. Over the next nine months, there have been approximately 25 egg-laying events, and without exception, the same male has guarded the eggs. Initially, the "unpopular males" who didn't pick up any eggs garnered sympathy. However, gradually, sympathy began to be expressed for the "popular males," with people saying, "They seem to be having a tough time."

However, for them, it's not a matter of "being popular or not." Both males and females engage in various strategies to leave behind as many offspring as possible.

Females likely choose males based on various characteristics to find a suitable mate for producing offspring. Conversely, males also want to choose females; a larger female who will lay many eggs would be preferable. This might lead to fights between males.

[Tokyo Sea Life Park Research Staff, Michi Amano]

(For more details, please see ZooExpress email newsletter No. 62.)