Schooling Munida gregaria

 Two species of lobster krill can be found in the waters around the Falkland Islands. Both Munida gregaria and M. subrugosa  are anomuran decapod crustaceans of the family Galatheidae. They are not true lobsters but are in fact more closely related to the porcelain crabs and hermit crabs.

Munida gregaria and M. subrugosa attracted attention many years ago. Records of these dense concentrations of crustacea causing surface waters to turn red date as far back as 1594. Subsequently many famous travellers rounding Cape Horn and passing through the Straits of Magellan or sailing close to the Falkland Islands have described this spectacle (see Matthews (1932) Lobster-krill anomuran Crustacea that are the food of whales. Discovery Reports. Vol V., p. 469 – 484 for more detail).

Munida gregaria was described at the end of the 18th century (Fabricius, 1793) while M. subrugosa was described later on in the middle of the 19th century (White, 1847). Up until the 1930s the data available was limited to morphological, taxonomic and the odd faunistic note.

 



Inside a school of adult (approx. 10cm) Munida gregaria

Lobster krill and squat lobster (Munida gregaria and M. subrugosa) occur in huge abundance especially in the shallow waters of southern South America and the Falkland Islands. In southern South America Munida spp. can represent up to 50% of the macrofaunal benthos. Benthic samples from the Beagle Channel show Munida spp. to represent 90% of the decapod biomass. Munida subrugosa is more common in the Beagle Channel but this situation is reversed in the Falkland Islands.

A late January swarm of very small (1cm) lobster krill.For the most common species in the Falkland Island, M. gregaria, the reproductive period starts in June with the size of female clutches increasing until many of the larvae hatch from November to mid December. After metamorphosis the post larvae shoal throughout the summer until settlement. They can be seen in huge number all around inshore Falklands during January and February.

Due to their huge abundances around the Falkland Islands lobster-krill are extremely important to our ecosystem. Larvae and post larvae are reported to feed on diatoms and calanid copepods. Adult diets consist to a large degree of sediment and particulate organic matter (POM). They are also reported to feed on diatoms, foraminiferans, nematodes, oligochaet worms, polychaets, crustaceans and macroalgae. Because of the large amount of POM in their diets they are considered to be important in nutrient cycling. The list of lobster-krill predators is high with a number of large whale species visiting the Falklands in February and March each year to take advantage their enormous shoals of post larvae that occur close to shore. Just about every medium to large sized predator around the Falkland Islands from molluscs, fish to seabirds including albatross, petrels and penguins feed on these bountiful crustaceans.

The unusual spectacle of adult lobster krill on the seafloor.