A world record was just set in near complete darkness, more than 9,800 feet below the surface of the Pacific Ocean. It took a little coaxing, but with some mackerel and a strategically placed floodlight, scientists were able to capture video of the most fish ever recorded in one shot.
In this case, it was a writing mass of 115 Ilyophis arx, cutthroat eels.
“Our observations truly surprised us,” said Astrid Leitner, a biological oceanographer and lead author on the study, who conducted this work as graduate researcher in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). “We had never seen reports of such high numbers of fishes in the sparsely-populated, food-limited deep-sea.”
The researchers captured the footage on a seamount in the Clarion-Clipperton Zone (CCZ) a region of seafloor that extends from Hawaii almost to Mexico, known for being rich with rare metals, including copper, cobalt, zinc and manganese. The eels were found near a region known for international mining operations.
“Over the years, it’s drawn increasing interest from the mining industry, which sees this new region as a way to cut down on human labour and the destruction of precious land,” Science Alert reports. “Sixteen contracts have already been issued for deep sea mining in more than 1 million square kilometres of this zone, and yet only a tiny portion of deep abyssal habitats have been sampled, explored, or even mapped by scientists.”
The team studied just a few seamounts in the CCZ. The peaks of these underwater mountains are about 9,800 feet below the surface, and judging from this dive, can support more life than the surrounding plains.
“The number of eels observed in this study at abyssal depths is truly unprecedented for both abyssal and bathyal depths,” the researchers wrote in the study, published in the journal Deep-Sea Research.
Abyssal plains and seamounts make up 70% of the ocean floor. This encounter highlights the importance of protecting ocean habitats.
“If this phenomenon is not just isolated to these two seamounts in the CCZ, the implications on deep sea ecology could be widespread,” Leitner said. “Our findings highlight how much there is still left to discover in the deep sea, and how much we all might lose if we do not manage mining appropriately.”
Watch the eels gather in the video below.