Another intriguing piece of marine debris identified (at least we think!) by Chelsea Thomas, IS489 (University of Hawaii) intern with the NOAA Marine Debris Program. Information was compiled and reviewed by NOAA MDP staff with assistance from Seba Sheavly, Sheavly Consultants.
Location where debris was collected: Midway Atoll, Northwestern Hawaiian Islands, HI, USA
Many of these small “cap-like” pieces of marine debris were found on the shores of Midway Atoll. You may be wondering “What on Earth” are these? Reliable sources believe the item is the “head” of a particular type of eel trap used by some fisheries; however, we are not 100% positive on the identification.
The photos below show two different variations of the head piece intact on the eel traps. The photo above shows the broken items with these different variations as well.
Eel traps. www.eeltrap.com
The NOAA Marine Debris Program found this eel trap (photo below) on Kahuku Beach, Island of O‘ahu with the head piece missing.
The eel trap “heads” found on Midway measured approximately 4cm in diameter. An eel trap manufacturer provided an illustration (below) that includes a measurement for the trap head at 4cm.
This raises the question as to why many of these pieces end up in the marine environment. One answer may be due to the manner in which these eel traps are handled when harvesting the catch.
The trap is baited and then hooked at the head to a line and sunk to the ocean floor. Sometimes traps are weighted to assure contact with the bottom. Later, fishermen retrieve the trap by pulling up the line, thus lifting the traps. Captured eels are released into a holding tank on deck. The action of submerging and retrieving the traps may put pressure on the head piece. This stress is possibly what causes the head to separate from the trap. It may be for this reason that the newest version of the trap has an improved head that easily hooks on and releases off the line (see photo below).
Eel trap heads. www.tradekorea.com
A special machine is needed on deck to hook and unhook traps with this new type of head, which requires less fishermen, resulting in a higher efficiency and lower labor costs. This updated trap head design may be one possible solution to prevent them from ending up as marine debris in the environment.
FUN FACT: In Korea, the government has an incentive program to address marine debris. Money is given to fishermen who collect fishing gear and other debris while out fishing. An eel trap is worth $0.15 if collected.
Cho, D.O., 2009. The incentive program for fishermen to collect marine debris in Korea. Marine Pollution Bulletin 58, 415-416.
Gorban, A., Kobayashi, H., Honma, Y., Matsuyama, M., 1964. The Hagfishery of Japan. 2, 5.