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The Geometry of a Cast Net | |
By Jorge Laguna, What is a cast net?... a question being asked by many to the MFC..., all the way from some commercial fishers in Northwest to others in Southeast Florida. In question is the definition of the term cast net. Current rules define it as having a radius of 12'7". A radius, as anyone with some basic geometry background knows, refers to a measurement from the center of a circle to its perimeter (outside). Some groups are intending to confuse the issue by claiming that a cast net is a "gravity operated vertical trawl" (whatever that may mean).  Let us assume for a minute that a cast net is like a shrimp trawl. If that is the case, the Commission could require the heavy TED's (Turtle Excluder Devices), as well as BRD's (Bycatch - finfish - Reduction Devices) to be placed on them. Further, the targeting of finfish with trawls is already prohibited in state waters. If you stretch your imagination a bit, a cast net could look like this trawl.
Back to basic geometry... So how do we measure the area a circle... there is a formula that has been around before I was born; in fact for thousands of years. A formula used by ancient Egyptians, the ancient Roman and Greek civilizations. A formula that defines the area of a circle: Area = "Where R is the radius as measured from the center of the circle and, where The Constitutional Amendment prohibiting gill and entangling nets, and limiting other nets to an area of 500 ft2 or less, was overwhelmingly approved (72%) by voters in 1994 and implemented in 1995. Article X, Section 16, of the Constitution clearly grouped nets into four categories: gill or entangling nets, seines, trawls, and cast nets. Hand thrown cast nets are in fact given an exemption from being considered entangling nets, but are still limited to an area not to exceed 500 ft2. How do we determine the radius of such a cast net with an Area = 500 ft2 ? By using the following formula: R = Square-root (A/ where the Radius is equal to the square root of the Area divided by Current Rule establishes a 12'7" radius for cast nets (to precisely have a 500 ft2 cast net the radius would need to be 12' 7.39") Perhaps the following illustration drawn to scale will further clarify the issue.
In addition to claiming that cast nets are vertically operated trawls, some fishers believe that the radius of such should be 18' 4" (why call it a radius if it ain't a circle?) instead of 12' 7". The only thing I can say is that such a radius would double the area allowed by the Constitution.
  Reference Spiegel M.A., Ph.D. 1968. Mathematical Handbook of Formulas and Tables. McGraw Hill Inc.  Geometry Says cast nets are Circular If you would like further information call the Fish and Wildlife Conservation Commission at 850-487-0554or e-Mail us at: Marine Fisheries | |
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Finally, when a person throws a cast net, his or her objective is to open it into an area that will maximize the surface area it fishes. What is that area, one may ask? - A circle (not a cone, a cylinder, a sphere, or any other shape). Grant it that many of us can only dream of throwing a cast net into a perfect circle, but most commercial cast netters would tell you that this is their main objective.Our mission: Managing fish and wildlife resources for their long-term well-being and the benefit of people.
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