Last Friday, a second oarfish washed up on Southern California’s shore within a week. The 14 foot fish was spotted on a public beach near the Oceanside harbor, a likely once in a lifetime experience for all present. Lifeguards contacted Kerri Danil, a Research Fisheries Biologist at the Southwest Fisheries Science Center (SWFSC), who coordinates the National Marine Fisheries Service retrieval of stranded cetaceans along the California coast. Suzy Kohin, supervisor of the Highly Migratory Species program, transported the fish back to SWFSC that evening. On Monday morning, a specialized team of research scientists dissected the oarfish to discover as much information as possible. In addition to looking for a cause of death, the dissection also proved a means to answer many questions about a creature rarely seen outside the depths of the ocean.
Three of the most common aspects of fish dissection focus on deducing the age, stomach contents and reproductive condition. In order to determine the age of the female oarfish, the team looked for otoliths, tiny ear-bone structures. Unfortunately, due to their incredibly small nature and that the head was mangled from unknown causes, the otoliths could not be retrieved. However, the age may still be found through its fin spines or vertebrae. The stomach contents were examined and contained little besides a small amount of krill. This common procedure helps identify the fish’s diet and might provide an indication as to the amount of food in the creature’s habitat. The ovaries, measuring 4 feet long and containing millions of eggs, were inspected to determine the oarfish’s reproductive condition. Preliminary evidence suggests that the oarfish is capable of multiple spawning events due to the presence of eggs at different levels of development. Microscopic analysis of the eggs will verify the species’ reproductive strategy.
Several tissue samples were taken to test a variety of environmental and genetic indicators. Tissue samples will provide information on any bioaccumulation of biochemicals or pesticides present in its habitat. Muscle tissues will also be examined for possible Fukushima radiation; which would indicate the fish might have migrated from the western Pacific. However, such evidence of radiation is improbable due to what is known about the structure and movement of the fish so far. DNA samples were also collected to determine population structure and compare genetic relatedness to the initial stranded oarfish from last week.
Scientists also hope to analyze the structure of the body. A researcher from California State University Fullerton has asked to view the vertebrae to help determine the biomechanics of oarfish movement. Nick Wegner, Fisheries Resources Division biologist, collected the gills to study the morphology and specialization of the gills. The liver, heart and eyes will be compared anatomically to those of other bony fishes. It also appears as though the skull is made of cartilage instead of bone, a rare occurrence, and the fish was x-rayed to provide further analysis of its bone structure.
Finally, the team will also look at the various signs of trauma and parasites. Phil Hastings of the Scripps Institution of Oceanography UC San Diego hopes to study the cookie cutter shark bites located along the body; while parasites, such as nematodes and tapeworms, were taken from the body cavity.
Overall, the discovery of this oarfish provides a rare opportunity for scientists to examine an otherwise highly elusive creature. By studying the various clues provided, we might come to know more about the life and structure of the oarfish.
NOAA Fisheries "On the Line" podcast: The Giant Oarfish
Antonella Preti measuring head of oarfish
Photo Credit Phil Hastings, Scripps Institution of Oceanography, UC San Diego