Evidence of marine predation on silver New Zealand longfin eels, Anguilla dieffenbachii

Abstract

AbstractThe use of Pop‐up Satellite Archival Tags (PSATs) has provided considerable new information about the behaviour of migrating (silver) eels (Anguilla spp.) at sea, with 9 of 19 recognised species or subspecies tagged to date. However, such studies often reported premature tag detachment and relatively high rates of predation. Since 2000, several PSAT‐tagged New Zealand longfin eels, Anguilla dieffenbachii, were released to understand migratory behaviour and location of potential spawning grounds. Of 20 PSAT‐tagged eels released in 2019, all tags detached prematurely, but 7 (58%) were likely eaten or injured by predators 1–81 days after release. Two eels were probably eaten by sperm whales, whereas other tagged eels were likely eaten by lamniform and non‐lamniform sharks, and southern bluefin tuna. Because of the high rate of predation, we recommend that future releases should be from smaller catchments or offshore.