Evaluations of Tag Retention and a Device for Releasing Discarded Hawaiian Spiny Lobsters Panulirus marginatus

Abstract

Tag loss and mortality that results directly from the tagging process are a concern to all tagging programs because they reduce sample sizes and can bias population and survival estimates. The purposes of this study were to estimate streamer tag loss in Hawaiian spiny lobsters Panulirus marginatus, evaluate the use of passive integrated transponder (PIT) tags in these lobsters, and determine the effectiveness of a cage specially designed to release tagged lobsters safely on the seafloor rather than on the surface where potential predators are present. To estimate tag loss, lobsters were double-tagged (polyethylene streamer and PIT tags) during research cruises in 2003 and 2004. Among the lobsters recaptured in 2004–2006, PIT tag recapture rates were approximately twice those for streamer tags after 1 year at liberty and approximately 4 times those for streamer tags after 2 and 3 years at liberty. Only two lobsters were recaptured that had a streamer tag but no PIT tag. A video system recorded Hawaiian spiny lobsters released from a specially designed release cage. The video observations indicated that the cage is an effective, simple, and inexpensive means for releasing lobsters safely on the seafloor. This cage could be utilized by commercial fishers to safely release sublegal and female lobsters. An additional benefit of the cage is that it insures an accurate release position, which is crucial for movement estimates, because it releases tagged lobsters directly under the vessel.