Does Size Matter? Female Mate Choice in Freshwater Goby

Choosing a mate can be a complicated matter to humans. Many factors such as looks, personality, or status always come into play. For the freshwater goby however, finding a mate seems quite simple for it seems to come down to a matter of size.

In Rhinogobius sp., more commonly known as freshwater goby, male size is a significant factor for the female’s choice of a mate. This is thought to be so because male gobies eventually take on the role of protecting their nest and larger males tend to have greater capabilities for paternal care.

Furthermore, during mate selection, males compete for reproductive resources like a nesting place, and of course – a female goby. As one might expect, the larger males are usually more dominant.

Additionally, male gobies, when they don’t have access to nearby food, tend to eat the female’s eggs instead and based on previous studies, the larger males are less likely to do this than smaller males.

However, a question remains: Do female gobies actually prefer for larger males, or do they merely choose the larger males because the larger males outcompete the smaller males?

SEAFDEC/AQD Deputy Chief Dr. Ito Sayaka partnered with Dr. Iguchi Kei’ichiro from Japan’s National Research Institute of Fisheries Science and Nagasaki University to gain insights on this.

Dr. Ito said it was difficult to clearly separate the contribution of male-male competition and female mate choice as they both contribute to the outcome of reproductive behavior.

“So, we created an environment in the aquarium where intermale interference was not possible and tested female mate choice with respect to male body size,” he said.

The results showed that females preferred relatively larger males as mating partners.

“It was thought that this was due to the greater ability of larger males to guard eggs, according to further experiments. For example, nests guarded by small males are easily taken over by other individuals and all the eggs there are eaten by them,” explained Dr. Ito.

Additionally, he said that when small males spawned with larger females, their males are more likely to cannibalize the eggs.

“These results indicate that it is important for us to consider the size composition of the breeders in the tank based on preference of female to partners, when culturing gobies, in order to improve the survival of the eggs,” Dr. Ito concluded.

To learn more about this study and its implications in detail, you can read the article entitled “Female mate choice for male size in a freshwater goby under experimental conditions eliminating inter-male interference.” You may request for a copy of the article here: https://repository.seafdec.org.ph/handle/10862/6514