Rock Lobster Reproductive Cycle: What are Tar Spots?

The reproductive cycle of Western Rock Lobsters is a fascinating process, and one particularly interesting aspect is the appearance of tar spots. These spots serve as important markers in a female lobster’s life, indicating her readiness to spawn and playing a crucial role in the species’ sustainability.

What is a Tar Spot?

When Western Rock Lobsters mate during late winter and early spring, males attach a packet of sperm to the underside of the female. This sperm packet, known scientifically as a “spermatophoric mass,” is dark and tar-like in appearance—hence the nickname “tar spot.” However, what you may not know is that when the packet is first deposited, it’s actually white and sticky, similar to chewing gum! Over the next few hours, it hardens and darkens into the familiar black spot.

The Mating Process

Mating typically begins in the cooler months of June and July, peaking as females prepare to carry their fertilised eggs. During this time, females develop fine hairs, known as setae, on their endopods (the inner segments of their swimming legs (pleopods) located on the abdomen), which help them carry their eggs until they hatch. The eggs remain under the female’s tail until they are fully developed.

Why is This Important?

The presence of a tar spot indicates that a female lobster is in the middle of her reproductive journey. During this time, she’s protected from fishing to ensure she can successfully carry and hatch her eggs, contributing to the sustainability of the species.

Sustainability Measures: Protecting the Future

One of the many sustainability measures in place is ensuring that tar-spotted females are returned to the water immediately. This simple but important practice helps protect the population, ensuring that future generations of lobsters thrive in Western Australia’s waters for years to come.

For more information about the reproductive cycle of Western Rock Lobsters, visit the Western Rock Lobster research page here.