NOAA's Marine Debris Blog

Keepin' the Sea Free of Debris!

“What on Earth?” ENTRY #005: Lobster/shellfish trap door hook (by Chelsea Thomas, guest blogger)

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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. This is Chelsea’s final blog and we are sad to see her go–she’s done such an awesome job! Thanks so much Chelsea!

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

Several plastic hooks have been found on Midway Atoll. You may be wondering “What on Earth” is this type of hook and what is it used for? Following some key sleuthing via the Internet, we think the hooks are used on lobster traps and other shellfish traps to latch and unlatch the door of the trap; however, we are not 100% certain.

A bungee cord is attached to the frame of the trap at one end and the hook at the other end (see photo below). This gives the hook tension to hold the door shut but also allows the fisherman to easily unlatch it.

 

Source: www.guangjingroup.com

Once the traps are baited, the door is latched shut, a machine is used to haul them off the side of the boat, and they sink to the sea floor. They are connected to a line and marker buoys (see photo below) that float at each end.

Source: www.seafish.org

These hooks are typically used on a range of traps called creels (traps similar to net cages).  They are used for catching lobster, crab, shrimp, cuttlefish, and crayfish. Because these traps are used to catch a wide range of species, they are sometimes also referred to as polypots. Overall, traps come in a wide variety of makes, models, and materials. For example, crab pots are often made of wire mesh, whereas lobster traps today are typically a combination of wood and metal.

There are various hooks that serve similar functions. The photo below on the left shows large grip hooks, medium hooks, shrimp pot hooks, and spinners, respectively. The large hooks are used to fasten the door on larger traps (e.g., for lobster) and the medium to small hooks are for smaller traps typically used for catching shrimp or crab. The hooks in the middle photo are typically used on crab traps.

  

Source: www.polypotcreels.co.uk, www.memphisnet.net, www.seattlemarine.net

Most of the hooks are made of heavy-duty nylon or polypropylene, though heavy-duty crab pot door hooks made of stainless steel are available as well (see far right photo above). One lobster creel manufacturer describes its hooks as follows: “Our new molded plastic hook is based on our heavier steel version but with refined release features, it is lighter, and corrosion proof. It is easier to handle in cold, wet conditions!”

A possible explanation of how the hooks may end up in the marine environment is due to natural wear and tear. It is suspected that with time, sea water may eventually corrode or degrade the bungee cord holding the hook, leading to the hook’s release.

A fishing gear website sells a kit to repair worn door latches on any crab or shrimp trap (see photo below). The kit includes two replacement hooks, a heavy-duty bungee cord, and stainless steel hog rings (the metal piece that secures the bungee cord to a hook). This may indicate that it is not uncommon for hooks or bungee cords to fall off or come apart from the trap.

Source: www.boatersworld.com

While we think this is a pot/trap door hook, we are not 100% sure. If you have any information about this marine debris item’s identity, please contact us at marinedebris.web@noaa.gov.

Author: NOAA Marine Debris Program

The NOAA Marine Debris Program envisions the global ocean and its coasts, users, and inhabitants free from the impacts of marine debris. Our mission is to investigate and solve the problems that stem from marine debris, in order to protect and conserve our nation's marine environment, natural resources, industries, economy, and people.

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