Written by Sean Beckwith, PhD student
ST. PETERSBURG, FL – Towing a plankton net to scoop up fish eggs may be routine, but determining the species is a different matter altogether. A collaboration of two labs at the College of Marine Science uses a new method to discover fish spawning grounds through analysis of the DNA in fish eggs.
The vast majority of fish in the ocean are broadcast spawners –the female releases eggs in large quantities to float around until the larvae hatch and swim away on their own. A problem facing many fisheries managers is the time it takes to estimate fish populations. A new method utilizing DNA will likely reduce that time from years to months.
Dr. Ernst Peebles realized that existing fish population methods could be extended to a much larger number of species through new technologies and new databases like FISH-BOL (fish barcode of life). With the development of the Marine Resource Assessment program in 2010 here at the college, Dr. Mya Breitbart was eager to collaborate with fisheries ecologists on gaps in the body of research that molecular biology methods might fill.
A process called DNA barcoding focuses on a segment of DNA that is short enough to be efficiently sequenced but long enough to allow for identification of species. While most fish eggs look alike, their DNA does not.
Working in one of Dr. Breitbart’s microbiology labs, USFSP senior Makenzie Burrows performs much of the hands-on DNA work related to this project. Dr. Breitbart explains the process further, “When we sequence this gene, we can then compare it against the database and that tells us what species each fish egg belongs to.”
From the original proof-of-concept study done in small Terra Ceia Bay (near the mouth of Tampa Bay), the DNA barcoding of fish eggs has expanded to cover the entire Gulf of Mexico.
With the identification data from Dr. Breitbart’s lab, fish population researchers can use the number of floating eggs, compare that with the rate of egg production and calculate the number of females releasing eggs for each species.
Dr. Peebles points out that this method is not only rapid, but could be very cost effective in comparison to conventional methods.
The most exciting aspect of this project for fisheries scientists is the discoveries that await them. Dr. Peebles notes, “This method is one of the best, if not the best, methods of detecting spawning in marine fish.”
And by identifying new spawning grounds, resource managers have the ability to increase protection of spawning habitats to ensure the longevity of ecologically and economically important species.