Researchers at the Leon Charney School of Marine Sciences at the University of Haifa discovered that the jellyfish swarms swim collectively towards the west, which may contribute to their survival
The swarms of the common jellyfish in Israel, the wandering string jellyfish, direct their swimming towards the west in a way that affects the direction of their progress, according to a new study conducted at the Charney School of Marine Sciences and published in the journal Current Biology. "Until now, it was common to think that swarms of jellyfish swim randomly and that their movement in space is dictated solely by the currents of the sea, but thanks to innovative research methods, we found that along the coasts of the country, the jellyfish swim towards the west, that is, against the direction of the waves," said Dr. Yoav Lehn from the Department of Marine Sciences at the University of Haifa is the editor of the research.
Jellyfish belong to the stingray system and have been around for about 500 million years with almost no morphological changes - and yet, in many ways, much is hidden over the obvious regarding what researchers know about it. One of the most intriguing issues related to jellyfish swarms is related to the ability to try and understand the migration patterns of the swarms and their movement routes along the coasts of the country. This lack of ability makes it difficult to prepare for the arrival of various entities such as power plants and desalination plants. "If the jellyfish were passive, i.e. without the ability to move on their own and actually drifted with the help of the currents alone, we would be able to predict the movement of the swarms. The fact that we are not successful is evidence that jellyfish have swimming abilities, which we are still unable to understand," said the researchers.
In the current study, Dr. Lehan and a team of researchers from the Leon Charney School of Marine Sciences, together with researchers from the Technion, the Hebrew University, and Tel Aviv University, sought to examine and understand the migration patterns of the schools of the migrating whiting on the shores of the country - and thus to try and understand the The swimming abilities of the jellyfish.
The data collection phase of the study was very complex and the researchers used innovative methods for this purpose. In the first phase, a light aircraft flew along the coastline from the shores of Ashkelon in the south to the shores of Nahariya in the north in order to map the distribution of the swarms, and locate the large swarms. In the second stage, the researchers followed and photographed the direction of progress of the swarms using drones operated from a research ship sailing near the swarms. In the last step, the researchers examined the swimming direction of the swarms in relation to the sea currents and the direction of the sea waves. "The use of a unique research method based on data collection from light aircraft, drones and research ships allowed us to characterize the swimming and movement patterns of thousands of jellyfish and analyze them with the help of mathematical models," said Dr. Lehan.
As mentioned, the researchers discovered that the swarms of jellyfish from a wandering filamentous species show navigational abilities. They swim together continuously and non-stop at a speed of about 10 cm per second towards the west, against the direction of the waves, distancing themselves from the shore and thus increasing their ability to survive. They also added that the swimming patterns may vary between different species of jellyfish and different marine environments "When the strong tidal currents are dominant, the jellyfish may direct their swimming against the current and not necessarily against the waves, to reduce the risk of being washed ashore. In other cases, jellyfish may actually prefer to stay close to shore in bays or estuaries, so swimming towards the open sea is not always the preferred choice. The goal in the end is to get to the place where the chance of their survival is the highest."
So why do the jellyfish still come near the shore, and in many cases even wash ashore and die? According to the researchers, the final direction and speed of movement of the jellyfish result from a combination of swimming and drifting by the currents and waves. When there are no waves and the current is weak - the movement will be determined by swimming alone. On the other hand, when the drift is strong, it will have a significant effect on traffic. "For example, after storms, many jellyfish reach the beach, because swimming cannot overcome the drift created by the waves. What is clear is that the jellyfish swarms do not drift passively in different directions. The research advances us in the ability to understand the movement of the jellyfish and perhaps even predict in the future when the swarms will reach the coastal strips and when they will leave," the researchers concluded.
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