As part of the study, which has been underway in Israel since 2016, the researchers performed the test on earthworms, but never on finfish. The first earthworm tested was found to be in advanced pregnancy. Shortly before, the researchers treated an earthworm that had been injured by fishing gear – and it turned out that it was also pregnant.
For the first time in Israel, an ultrasound examination was performed on a whitetip shark (Carcharhinus plumbeus), as part of a long-term study of local shark populations. The examination, conducted this week on the whitetip shark Romi by a team of researchers from the Super Predator Laboratory at the Maurice Kahn Marine Research Station of the University of Haifa off the coast of Hadera, revealed that she was in the advanced stages of pregnancy. At the same time, another whitetip shark, Emily, found with a fishing hook stuck near her gill openings, was successfully treated – and during the tests it turned out that she was also pregnant.
The study, which is now in its tenth year off the coast of Hadera, focuses on diagnosing reproductive indices among local shark populations. This area is a seasonal aggregation site, but the reasons for this are still being studied. "The study allows us to gain important insights into the reproductive behavior of the sharks in our area. We are trying to understand whether this is a permanent spawning site, or just a transit station for the sharks. The data collected through tagging, hormonal tests and ultrasound scans help us put together a more comprehensive picture of the sharks' reproductive processes in the Mediterranean," said Dr. Aviad Sheinin, head of the superpredators department at the Maurice Kahn Marine Research Station of the Czerny School of Marine Sciences at the University of Haifa.
During the tagging and routine examinations, the researchers discovered that Emily had suffered a fishing hook injury. The hook was successfully removed, and she was also found to be in early pregnancy. “This is another case that illustrates the connection between fishing activity and shark population conservation,” notes Dr. Sheinin. “The better we understand their movements and breeding periods, the better we can promote protection measures for these species. Our access to sharks as part of the study also allows us to provide them with immediate treatment if necessary, as was the case with Emily.” He says, “In general, sharks have a good ability to recover from injuries, but it is important to continue monitoring them to understand the long-term effects of encounters with fishing gear.”
In the case of Romy, the finned shark, the ultrasound examination provided new data on the species' reproductive cycle in the Mediterranean region. "The size of the embryos observed in the examination – between 50 and 77 centimeters – is consistent with the known gestation cycle of finned sharks, which lasts about 12 months," explained Dr. Lee Livne, a postdoctoral fellow in the Super Predators Lab who studies shark reproduction. "The encounter with Romy was particularly significant because to date, only five finned sharks have been documented in our area, and this is the first time we have been able to conduct an in-depth reproductive examination."
Romy and Emily, named in honor of the late Romy Gonen and Emily Damari, are the seventh and eighth sharks to be tagged this season, and as part of the ongoing research since 2016, 123 sharks from the region have been tagged so far. The researchers hope that continued monitoring of the tagged sharks will allow for a better understanding of their migration and breeding patterns, and thus contribute to their conservation in the Mediterranean Sea.
More of the topic in Hayadan:
