A team of researchers has found that at least some fish larvae, such as splitnose rockfish, stick with relatives for longer than expected. Rather than simply dispersing at random, siblings were more likely to be found in the same group a year later. The details are in a paper that was just published in the journal Proceedings of the National Academy of Sciences.
Many marine fish and invertebrates release their tiny larval offspring into the open water during spawning events, leading to a process called pelagic dispersal. The splitnose rockfish (Sebastes diploproa) is one such species. Splitnose rockfish are livebearers that give birth to thousands of larvae, which float around in the ocean before settling somewhere safe. Only a handful of these larvae will actually make it to adulthood; the majority are preyed on by larger organisms. Previously, scientists believed that these larvae dispersed at random after mass spawns.
Researchers from Oregon State University, funded by an award from the Hatfield Marine Science Center, collected rockfish larvae that had recently settled off the Oregon coast. These larvae had traveled up to a few hundred meters to get to shallow waters over a period of about a year. The larvae were then genetically analyzed in the team’s laboratory.
The research team found that the groupings of larvae were not totally random. Even after a year, 11.6% of larvae found in an individual group were siblings. This shows that sibling fish larvae are more likely to stick together, even after a year in the open ocean. This is the first time this behavior has been recorded, partially because it’s difficult to study the mechanics of pelagic dispersal. Tracking minuscule larvae is nearly impossible and scientists have struggled to streamline the process. The new findings could improve current mathematical models used by marine scientists to predict larval aggregation.
The team’s findings show that larval dispersal is not completely random and related larvae tend to group together. The study provides new insights into dispersal behaviors and may also help scientists improve computer models.
Ottmann et al. Long-term aggregation of larval fish siblings during dispersal along an open coast. Proceedings of the National Academy of Sciences (2016).