by Julia Renner, Environmental Science, 2017
Jon Puritz, postdoctoral research associate in Dr. Katie Lotterhos’ lab at Northeastern’s Marine Science Center, had a paper published October 26 in Scientific Reports. The report, “Fine-scale partitioning of genomic variation among recruits in an exploited fishery: causes and consequences,” pointed to the need to monitor and protect reproducing groups of red snapper fish over a wide geographic range.
Red snapper is one of the most heavily exploited fish species in the United States and has been overfished for three decades, with its population declining 90 percent during the second half of the 20th century. Puritz investigated the causes behind the fact that genetic diversity among young—otherwise known as genetic patchiness—in red snapper is observed even on very small spatial scales. The amount and type of genetic variation within a population can indicate where and how reproduction is taking place, and can point to the best methods for preserving and protecting exploited species. Using a type of genetic sequencing called double-digest restriction-site associated DNA sequencing, Puritz investigated genetic variation in samples of juvenile red snappers and adults that could potentially be parents. What he found contradicted a previously held theory of “sweepstakes recruitment,” which posits that large groups of young produced during each breeding cycle come from only a few breeding individuals, and those individuals win the genetic sweepstakes, with a large number of offspring in each area therefore being genetically similar. Puritz’s discovery of genetic diversity among offspring at very small spatial scales indicates that rather than a few breeders contributing disproportionately to the next generation, “large and independent groups of breeders are contributing to recruits, likely across a wide geographic area,” said Purtiz.
The most significant implication of these findings, Puritz says, is that “monitoring for this and many other fishery species needs to take place on a yearly basis, across multiple spatial scales. We still have a lot to learn about recruitment in broadcast spawning species,” he says, pointing to the need for additional monitoring and research. “For those that are heavily fished, it’s even more critical that we take the time and spend the money necessary to truly understand what is affecting recruitment.”
The techniques used in his research on red snapper can also be applied to projects examining populations of other heavily exploited species.