How a project counting thumbnail-sized baby lobsters since 1968 reliably predicts a $240m industry’s future

Fishing is a game of risk and reward the world over, but off the Western Australian coast the odds of a good catch are stacked in crayfishers’ favour.

The $240 million per year western rock lobster industry — WA’s most valuable fishery, which was worth as much as $400m pre-COVID — has the unique ability to predict its catch four years into the future, all thanks to the work of a curious scientist more than 55 years ago.

In the 1960s, CSIRO scientist Bruce Phillips determined that the amount of baby lobsters, or puerulus, found hiding in seagrass on the coast directly correlated to the health of the fishery in four years time. 

Lobsters hatch from eggs as larvae, and spend almost a year drifting and growing in the Indian Ocean’s deep water before transforming into puerulus. 

“This little baby lobster’s job is to swim from the open ocean off the continental shelf, all the way to the coast, and find a habitat to live in where it won’t get eaten,” said Department of Primary Industries and Regional Development scientist Simon de Lestang. 

“They swim in mainly at night on a dark moon … and do not eat the whole way because they want to stay perfectly clear so any fish swimming past don’t see it.” 

Many puerulus do not make it, but those that do will grow into the famous red WA crayfish, members of Australia’s most lucrative wild species fishery.

Dr Phillips discovered he could trick the puerulus to sit for about a month in artificial seagrass beds, which he floated in shallow water.

When he began counting and recording the number of puerulus he found in the ocean each month in 1968, little did Dr Phillips know he was beginning a data set which is now the envy of fisheries around the world.

“He started with six collectors at Seven Mile Beach, just north of Dongara. He set up a protocol of how to sample them, shake them, clean them, process them every month, and that has been going since 1968,” Dr de Lestang said. 

“I’ve spoken to Bruce about it and they had no idea how valuable and how good the data would be.”

The data is invaluable because the amount of puerulus which make it to the coast indicates how many legal-size rock lobsters will be available to the commercial and recreational lobster industries in four years’ time. 

“It gives us really good information on how many lobsters they’ll be able to catch, and how the environment and the changes we are seeing in water temperatures and currents and storm patterns is effecting recruitment to the lobster fishery,” Dr de Lestang said. 

“It allows us to look into the future and know what we are expecting this fishery to look like in 10, 20, 30 years time as climate change continues to modify the ocean.” 

Every month Fisheries researchers continue to measure and record puerulus settlement data at nine sites along the WA coast. 

The puerulus collectors are designed to mimic floating seaweed. They are hauled to the surface, shaken thirty times, and the amount of baby lobsters that fall out is counted.

Sheets are then shaken another 10 times until no more puerulus fall out. 

In 2008, alarm bells sounded for the lobster industry when very few puerulus were recorded along the coast. 

“We knew in four years time that there would be very few new lobsters coming into the fishery, so that gave us a four-year lead time to work with the industry and say ‘what should we do, how should we change what we are doing’,” Dr de Lestang said.

“It allowed us to completely change the management of the fishery.

“We moved to a quota, and we were able to sail through 2012–2014 when a normal fishery would have collapsed.

“We were strong through that period, and that’s purely down to what Bruce Phillips started at Seven Mile Beach in 1968.”