A Study of the Connectivity of Grunion Populations Is Underway
A spawning female grunion digs tail first into the sand to deposit her eggs, while a male wraps himself around her, depositing milt. Photo: Alan Pitcairn
Related Information
Research Contacts:
Danielle Zacherl
Biology Department
CSU Fullerton
T; 714-278-7510
E: dzacherl @exchange.fullerton.edu
Karen Martin
Biology Department
Pepperdine University
310-506-4808
E: karen.martin @pepperdine.edu
Relevant Links:
Does Beach Grooming Harm Grunion Eggs?
Fox News Video of Grunion Run from April, 2008
Revised:
May 7, 2008
May 6, 2008
Contact: Christina S. Johnson, California Sea Grant, 858-822-5334, csjohnson@ucsd.edu
A Cal State Fullerton biologist has been awarded a $30,000 grant from California Sea Grant to study the amazing California grunion, one of only two marine fish species that leaves its watery world to spawn, bravely, on land.
The grant’s recipient, Danielle Zacherl, a professor in the Biological Sciences Department at CSU Fullerton, will be looking at the fidelity of grunion to their birthing beaches, in particular, whether adult grunion return to where they were born to spawn, as do salmon.
As a first step in answering this, Zacherl and her co-investigator on the project, biology professor Karen Martin of Pepperdine University, will examine the chemical signals imprinted on calcified ear structures in developing grunion embryos. These tiny pebble-like structures are called otoliths and grow in daily layers.
The scientists’ theory is that the sand and seawater that bathe the grunion embryos leave a chemical mark on the otoliths, creating a natural tag of where the fish were (or would have been) born. It is hoped that this tag can be extracted from adult fish to determine the reproductive connectivity of grunion populations in California.
CSU Fullerton biology professor Danielle Zacherl. Credit: CSU Fullerton
Beginning this month, Zacherl and CSU Fullerton graduate student Andy Fredell will collect grunion eggs from 15 beaches between Monterey and San Diego, isolate the tiny otoliths and use laser ablation to pulverize the otolith into an ionized gas cloud. Mass spectrometry will then be used to determine the cloud’s chemical composition.
Next summer, the scientists plan to return to a subset of the same 15 beaches (it takes about a year for the fish to reach reproductive maturity), collect adult grunion, remove their otoliths and then use a laser to expose the inner part of the otolith (the part calcified while the fish was an embryo). This layer will then be ablated, analyzed for its chemical composition and compared to the chemical signatures of grunion eggs from the same beach.
“If the chemical signals of the adults from a particular beach match those of the embryos collected at that beach, it will tell scientists that the grunion do indeed return to their natal grounds,” Zacherl said. “Alternatively, if all the grunion are coming from only a few beaches, it tells us you want to protect those beaches.”
Grunion are silver, sardine-like fish whose odd mating behaviors are eerily tied to the lunar and hence tidal cycles. When the tide is right, grunion “body surf” onto sandy beaches. The females then frantically bury their tails in the wet sand, releasing eggs, while the males curl themselves around the upright females and deposit milt.
The clutches of the tiny tangerine grunion eggs incubate in the sand until the progression of the tidal cycle scours away the sand. The eggs hatch when exposed to the turbulence of incoming waves. Newly hatched grunion (larvae) then ride the swash out to sea. The fish reach reproductive maturity in about a year.
“It is really exciting to be working on such a charismatic species, and frankly the field work is really fun,” Zacherl said. “A grunion run is a classic Southern California experience.”
NOAA’s California Sea Grant College Program is a statewide, multi-university program of marine research, extension services, and education activities administered by the University of California. It is the largest of 31 Sea Grant programs and is headquartered at Scripps Institution of Oceanography at the University of California, San Diego. The National Sea Grant College Program is part of the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce
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