The 2017 wolf eel wrangle is underway! Seattle Aquarium staff members are systematically performing annual check-ups on the Aquarium’s wolf eel population, looking at the condition of wolf eels’ teeth and gums and measuring their lengths, weights and girths.
In addition, aquarists are updating the wolf eels’ database identification photos, looking for spot patterns and unusual blemishes or scars—and this year, they are passive integrated transponder-tagging (or PIT-tagging) each individual fish. This process involves inserting a tiny chip, which can easily be scanned and read digitally, under the skin of each wolf eel. This will aid in tracking the animals as they progress through different exhibits at the Aquarium. Aquarist Angie Deccio says this reminds us that “our wolf eels are considered non-releasable by Fish & Wildlife because most of the younger ones are captive-reared.”
Although their maximum lifespan is not known, wolf eels are estimated to live at least 20 years. According to Angie, “Some of the recent animals we have lost had their otoliths counted and were estimated to be about 19 years old!” (Otoliths, also called “ear stones,” are hard structures made of calcium carbonate, located just behind the brains of bony fishes. Otoliths have rings that can be used to estimate fish age—similar to rings on a tree.)
With the new PIT tag system, tracking the youngest wolf eels with hatch dates will aid in documenting more exact captive age ranges.
A few fun facts from the first week of wolf eel check-ups:
- Average length: 5 feet
- Average weight: Approximately 20 pounds
- Total number of wolf eels currently at the Aquarium: 14
- Age of oldest known wolf eels in the Underwater Dome exhibit: Approximately 15 years old
Want to learn more about wolf eels? Check out our animal fact sheet, then plan a visit to the Seattle Aquarium!