Nurseries in the deep sea( gust 2000. While performing geological ...)

gust 2000. While performing geological surveys with ROV Tiburon, they noticed that octopus and blob sculpin were common near certain cold seeps, where hydrocarbon-rich fluids seep out of the seafloor. When they returned to the region in 2001, they brought along biologists, who realized that the octopus were present in unusually large numbers. On one dive, the ROV also brought up a rock sample which was covered with eggs. It wasn't until later, when Drazen watched videotapes of these dives, that he realized both the fish and the octopus might be brooding eggs. Intrigued, Drazen organized a third dive in July 2002, to count the animals and their eggs and to make more observations. The high densities of animals measured in certain areas convinced Drazen that these nurseries might qualify as biological hot spots.

Previously discovered biological hot spots in the deep sea, such as hydrothermal vents and the tops of seamounts, have been related to geological or topographic features that cause an increase the availability of food. The nurseries on the Gorda Escarpment may represent a totally different type of hot spot, where physical conditions particularly favor the development of eggs. Drazen is still not sure what aspect of the physical environment makes this spot so popular for brooding animals.

Whatever the key conditions may be, Drazen points out that such areas are critical habitat for the species involved. He and his co-authors are concerned that these undersea nurseries could be endangered by commercial trawling or long-line fishing. Such fishing has expanded into the deep sea as near-shore fish stocks have declined. For this reason, Drazen suggests that reproductive hot spots such as this might qualify as areas to be protected from fishing.

Finding one reproductive hot spot may also help scientists discover other such areas. But as Drazen points out, "Unlike hydrothermal vent and seamount communities, which persist for generations, repr
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Contact: Debbie Meyer
debbie@mbari.org
831-775-1807
Monterey Bay Aquarium Research Institute
3-Sep-2003

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