Tracking of Spiny Lobsters Yields Surprising Results

March 21, 2007

Contact: Christina S. Johnson, csjohnson@ucsd.edu, 858-822-5334

California spiny lobsters in the Point Loma kelp bed in San Diego move anywhere from 50 meters to 1 kilometer every night scavenging for food. By morning, many return to a home area, which on average is about 100 square meters.

California spiny lobsters find shelter among rocks.
Credit: Thien Mai.

These are two main findings of a California Sea Grant/California Department of Fish & Game tagging study led by San Diego State University biology professor Kevin Hovel and Cal State Long Beach biology professor Chris Lowe.

“What the study says to me is ‘wow,’ lobsters move around a lot more at night than I thought,” said Charlie Graham, a commercial fisherman in Santa Barbara who is familiar with Hovel’s results.

“The art of lobster fishing is deciding where and when to set traps,” Graham said. “The research tells me I can be happy setting my traps a little farther from the beach and letting them (the lobsters) come to me. I don’t have to risk losing a trap by putting it near the surf grass.”

Hovel’s findings are based on two seasons of tagging and tracking data and on a series of dive surveys that let the scientists correlate lobster movement patterns with specific environmental features.

“The take-home message is that lobsters move a lot.” Hovel said. The average lobster moved about 400 meters a night, though there was a range of 50 meters to 1 kilometer.

“We also showed lobsters move among habitats more than expected,” Hovel said. Lobsters’ journeys from kelp forest to surf grass or vice versa are very often beneath understory algae.

Another discovery has been that spiny lobsters do not “home” to specific shelters – a special rock crevice, ledge or rock pile, for example. Instead they seem to have fidelity to a particular area, usually about 100 square meters with many sheltering areas in it.

The results of the study can help in stock assessment and in identifying habitat areas that are critical for sustaining a lobster fishery, he said.

Steven Berkeley of the Long Marine Laboratory at UC Santa Cruz bases this conclusion on an analysis he has led on the timing of rockfish spawning, as a function of female rockfish age, and of larval quality, as measured by oil globule size.

A California spiny lobster hides under a rock ledge.
Credit: Thien Mai.

This analysis has shown that for Pacific ocean perch, widow and yellowtail rockfishes, the oldest females spawn earliest in the season. They also produce larvae with the largest oil globules (the source of nutrition for the developing embryo). Larger oil globules are associated with higher rates of larval survivorship, and good recruitment is usually correlated with high survivorship in larvae produced during the earliest part of the spawning season.

Translation: “Older female rockfish just get better with age,” said Berkeley, whose research on rockfish reproduction has led to what is colloquially known as the “big-fat-mamma” hypothesis. He calls it more delicately “the maternal effect,” but the idea is the same: For many species of rockfish, the oldest, biggest females are the best reproducers.

For the chilipepper rockfish, a different pattern was observed. There was no appreciable difference in the size of oil globules or in the timing of spawning for older vs. younger females.

The importance of this research is that “it tells us we need to protect the large adults of these three rockfishes,” Berkeley said, since they are the ones most likely to be contributing to the next generation.

Enter marine reserves.

With traditional fishery management tools, it is almost impossible to selectively protect older females, he said. “One of the real advantages of marine reserves is that they can protect older fishes. This is important because fishing, even at sustainable levels, removes the oldest fish from the population, and it does it very quickly.”