MIT Sea Grant College Program

 
     
 

The Whale-free Buoy

Description: The Whale-free Buoy reduces the risk to marine mammals from passive fishing gear by eliminating the normal mechanism for entanglement in buoy lines - the abrupt intersection between the line and the buoy. Through a combination of taper and flexibility, the Whale-free Buoy resists being caught by the fluke, fin, or baleen.

How the Whale-free Buoy design works: The Whale-free Buoy is an innovative concept aimed at reducing the risk of whale entanglement in passive fishing gear. The device is a replacement for the conventional buoy used to mark and to facilitate the retrieval of the gear. The novel features of the Whale-free Buoy are its shape and flexibility.

A prototype of the Whale-free Buoy is pictured in Figure 1. It is fabricated from an industry-standard 5" x 11" Spongex buoy to which a polyurethane rubber stem has been added. This stem is flexible and hollow and eliminates the abrupt transition between rope and buoy that is associated with a conventional buoy. It is this abrupt transition between rope and buoy, often exaggerated by a knot, eye, or swivel, that often initiates an entanglement.


Figure 1. A prototype 5" Whale-free Buoy during commercial evaluation.

The whale or other marine mammal typically encounters the buoy line at some distance below the surface. As the rope slides past the fin, fluke, or mouth, the buoy comes in contact with the animal. The sliding past the gear stops. Due to buoyancy and hydrodynamic drag, the conventional buoy resists being pulled past the obstruction. As the animal strains under the pull of the gear, further entanglement occurs until no amount of maneuvering of force can free the animal.

The taper and flexibility of the Whale-free Buoy prevents this scenario. The gentle transition from the line to the buoy allows an unimpeded sliding of the buoy's stem around the obstruction. As the new buoy continues to slide over the fin or fluke, the increasing stiffness of the stem eventually provides the leverage to flip the buoy around and free. In the case of a buoy line caught in baleen, the gradual taper of the buoy allows it to be pulled free.

How the Whale-free Buoy will help fisherman?
The Whale-free Buoy is compatible with most forms of passive fishing and can be used with no other changes in the gear or its method of use. It can also be used in combination with other whale-safe methods.

By reducing the risks posed by buoy lines, the Whale-free Buoy addresses the most significant risk posed by passive fishing gear. The most important feature of the buoy is that it doesn't compromise the integrity of the gear as do weal links or other techniques where the gear must fail in order to be effective.

In addition to reducing the risk of entanglement, the Whale-free Buoy offers other advantages by being less likely to catch on vessel keels and rudders as well as tug towlines, trawl warps, or paravane cables. These are common causes of gear loss and presents a measurable advantage to fishermen in addition to knowing that his gear is whale safe. The buoy also tends to stand vertically, even in a current, greatly increasing the visibility of the buoy and facilitating its easy retrieval.

The Whale-free Buoy will be an inexpensive product that can be integrated into the fisherman's gear through attrition. In addition, the tapered flexible stem can be provided as an attachment to standard buoys.

Whale-safe gear is becoming a requirement in many fisheries and without practical solutions to entanglement risks fishermen will lose their traditional fishing areas and seasons.

The early solutions to the problem are proving inadequate. Breakaway links in the buoy line are not preventing entanglements since to be of practical use, their load limits are probably too high. For example, along the U.S. east coast, the ALWTRT plan requires buoy line weak links of 600 pounds inshore and 1,500 pounds offshore in the fixed gear fisheries. Unfortunately, those loads are well in excess of what is likely to cause a marine mammal to sense an obstruction and begin to thrash to break free.

Based on the tests described in the included PowerPoint presentation, the Whale-free buoy, consistently released at loads less than 40 pounds for smaller buoys suitable for inshore fishing and less than 80 pounds for larger buoys more suitable for offshore locations. This dramatic reduction in the load required to free the whale will make the difference between an uneventful encounter and a life-threatening entanglement. An added advantage to the Whale-free Buoy is that the fishing gear remains intact after the encounter.

The loss of gear is costly to the fishermen but there are further problems in that if the fisherman in unable to retrieve it, it becomes ghost gear and can continue to cause mortality to the target species and other marine life. Though most fishermen believe whale encounters are rare, loss of marker buoys due to other marine traffic is not. The Whale-free Buoy's performance is equally useful against these more frequent hazards.

The gear loss that can be prevented by the adoption of the Whale-free Buoy is significant and through its use, fishermen can increase their profitability.

Tests to date: The Whale-free Buoy has been tested in several ways. Initially, several prototypes were provided to lobstermen to evaluate the compatibility of the device with current commercial methods. No problems were found and the comments of Capt. Mathew Thomson of Monhegan Island are included in the PowerPoint slide show that accompanies this submission.

Next were efficacy tests. A commercial fishing vessel was fitted with an apparatus to simulate an encounter of a whale fin or fluke with a buoy line. The apparatus presented an engaging crook at a depth of 5 feet (1.5 m) below the surface. A variety of conventional and Whale-free buoys of different sizes were attached to weights of different sizes and placed outside Gloucester Harbor. Various combinations of vessel speed and fair tide and foul tide encounters were used to understand the dynamics of such events and when and under what loads the buoys released. The test procedure and the results are portrayed in the slide show, including underwater video clips.

Finally, the matter of entanglement in baleen was addressed by comparing the pull required to free several different buoy shapes through an underwater specimen of baleen. Again, the favorable test results are reported in the slide show. Even the very slender "pipe buoys" proved less effective when compared on a diameter or cross-sectional area basis.

An interesting benefit of the efficacy tests described above has been the development of a practical apparatus for testing buoy innovations. Short of enlisting the services of a whale, it is the best tool available for simulating an encounter. The simple crook arm used in these initial tests could be replaced with a more representative geometry of entangling areas on specific marine mammals.

Contact
Cliff Goudey, Director
Center for Fisheries Engineering Research
Massachusetts Institute of Technology
Sea Grant College Program
MIT Bldg. NE20-376, 3 Cambridge Center
Cambridge, MA 02139 USA
Phone: 617-253-7079
Fax: 617-252-1615
Email: cgoudey@mit.edu
URL: http://seagrant.mit.edu/cfer/

 

Related
"Efficacy Tests of the Whale-free Buoy"

 

U.S. Patent for Whale-free Buoy
(Full Text)