Environmental Monitor

From February 2015 to November 2015 I was a freelance science writing intern for Fondriest Environmental's magazine Environmental Monitor, which covers technological advancements in monitoring systems for air and water quality in oceans, lakes, rivers and streams. Here you will find my entire collection of short briefs and longer form features written for the magazine. 

Snapper Spawning Schools Have Complex Histories, Rely On Timing Over Location

By Cassie Kelly, July 23, 2015

A new study from the Hawaii Institute of Marine Biology has found that timing is much more important to the survival of snappers on the reef outside of Punta Hicacos, Cuba, who are coming together to spawn, than the location of their spawning aggregations.

Megan Donahue, an assistant researcher at the institute and co-author of the study published in the journal PLOS ONE, said there are two benefits for snappers, which are solitary creatures, to come together. The first is that they get to choose their mate, which may be difficult to do otherwise. The second is for the benefit of their offspring. When the fish lay together at high densities, and there are thousands of eggs, it is much more challenging for predators to get to all of them.

Donahue and her team were curious about how the snappers choose when and where to aggregate for spawning, so they partnered with the National Institute for Mathematical and Biological Synthesis to look at the frameworks through which the fish decide.

After studying 10 different locations in Punta Hicacos, they concluded that the mean survival of the snappers was higher during specific periods of the lunar cycle, whereas survival rates between spawning areas were similar regardless of location.

Scientists also state in the study that the pattern was even more striking for minimum larval survival. They write that “the minimum percent larval survival over the ten simulated spawning periods was twice as high inside the observed spawning period compared to outside the observed spawning period. Similarly, average distance traveled by settling larvae and larval age at settlement have stronger patterns along the temporal axis than the spatial axis, indicating greater sensitivity to timing than location.”

“It’s similar to deciding if it is better to go to Joe’s Dive Bar on Monday night, or to the Downtown Tavern on Thursday night,” said Donahue. “Is one of those better for your reproductive success in the long run? So, that’s what the study was about.”

From a conservation perspective, Donahue says knowing how snapper aggregations decide when and where to spawn is absolutely crucial to their survival, because when overfished, there can be detrimental consequences.

“There are situations where spawning aggregations have been fished so hard that they are actually eliminated,” said Donahue. “So when that happens, there have been examples of where new spawning aggregations have come up in other new locations. And one of the things that our study suggests is that the timing and location of those aggregations is quite important and it’s not clear that a new one that arises will have, at least initially, the same advantages for larval success that the well-established ones have.”

Donahue said this finding suggests that the aggregations evolve over time and develop a complex history of how to reproduce with as little failure as possible.

“So, let’s say you can spawn over three days and that third day has been consistently better,” said Donahue. “So the organisms that are spawning on that third day are the ones that are doing a bit better so the whole aggregation shifts a little bit later.”

Donahue said that they believe the snapper aggregations lose all of that history and must start over again when they are fished out. Though she suggests fishermen stop fishing during spawning altogether, she does understand the convenience.

“It’s so easy to overfish because of their (snappers) biology,” said Donahue. “Once a year they have a big party, and it’s so easy to go and crash the party.”

To expand on the research, Donahue and her team are planning to follow up on the idea of a spawning window and study other fish species to see how important timing is for their mating success.

This article appeared in Fishsens Magazine, an partner magazine to Environmental Monitor. Read the orginal post here