The Physics of Catching the Fish

Home the rod, the reel, the line.



The halibut itself can exert multiple forces on the line including tension and shear. The force of tension that is put on the line by the fish is felt through the torque on the rod and partly absorbed by the frictional force in the reel. The fish also experiences the force due to the changes in pressure from being brought up from the bottom at a depth of up to 100 meters. For every 10 meters the fish is brought up from the bottom the fish experiences a change in pressure of 1 atmosphere. Fish that live at extreme depths have ways to deal with the problem of intense pressure but are not usually able to deal with extreme changes in pressure that occurs when they are brought up quickly. This is especially true of fish that use a swim bladder to deal with the problem of buoyancy. The problem of buoyancy is explained by Archimedes principle F_B=W_fluid. The buoyant force is the upward force that a fluid applies on an object that is partially or completely immersed in it. Since the halibut is completely immersed in seawater the buoyant force acting on the halibut is equal to the magnitude of the weight of the seawater that the halibut displaces. An average size halibut can weigh about 75 kilograms and be over a meter long. To see a chart on how to estimate the weight of a halibut of a known length click on the halibut below.
Halibut may use other methods of achieving neutral buoyancy at extreme pressures such as reduced bone weight. I truthfully don't know how halibut have overcome this problem but I do know they migrate long distances and usually live at extreme depths but migrate to as shallow as 20 meters during the summer.