Townsend Cromwell
TC-99-04 Lobster Tagging
TC-99-04 Lobster TaggingMarch 24-April 21, 1999
March 29, 1999 We arrived in Honolulu on the Thursday (March 18th) at 9:00 pm. The next 6 days consisted of resupplying the ship with fuel, food, and repairs to equipment that couldn't be accomplished at sea. By Wednesday the 24th, the ship was fully serviced and restocked. All the materials from the Marine Mammal Research Program Field camp cruise (TC-99-03) had been removed, 240 lobster traps and their associated lines and buoys had been loaded, and at 6:00 pm, the ship's lines were thrown off and we backed away from our pier. We are now enroute to Necker Island (right), 378 nm NW of Honolulu where we will set lobster traps in the afternoon and retrieve them the following morning. The intent of the cruise is to capture lobsters (spiny and slipper) which will be
tagged with special tags, and released. From the tags returned to the NOAA Fisheries scientists (by fisherman or this ship when we perform our June Lobster Assessment Cruise), the distance the lobsters traveled can be determined by
comparing release location against the capture location. Its hoped that the data from this study can be used to gain a better understanding of the movement of adult lobsters.
When a lobster grows, it is unlike animals such as cats and dogs, which grow slowly until adulthood. Lobsters have a hard external shell that must be shed in order for the lobster to grow. So when a lobster is ready to grow (ie.
molt), it retreats to a dark cave where its exoskeleton (the shell) splits open and the lobster crawls out. The newly molted lobster is soft and an easy meal for other animals which is why it goes into hiding. Over the next hour or so,
the lobster's body absorbs sea water which causes its body to swell. The new exoskelton then hardens and the process is complete until the next molt. You can imagine how hard it is to tag an animal that regularly sheds its outer shell. However, the tags used for this study are retained by the lobster even through their molts. As a result, these tagged lobsters will also be
assessed for growth, survivability and population estimates. Previously, for population estimates, we would capture lobsters and determine only the sex, species and size of the lobsters. However, with these tags, we can now identify
individual lobsters which enables the fishery scientists to look up the tag and see where we caught this actual lobster, when, and what size it was at the time. This information gives clearer insight as to how individual lobsters move around and grow within their population. This provides a cleared understanding of the population as a whole.
- For related information about lobster research, visit the Honolulu Laboratory's Kewalo Research Facility Lobster Research web pages.