Advantages and Disadvantages

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Advantages      One clear advantage of having a swimbladder is that little to no extra energy is necessary in order to remain stationary at a constant level of water.  Only a slight control by use of the pectoral fins is required to balance out the propulsive force of water exiting the gills.  Fish with no swimbladder on the other hand, such as mackerels, sharks, and rays must expend energy by constantly swimming in order to keep from sinking.

Another advantage of swimbladders is oxygen storage.  Physoclists and physostomes alike may occasionally use the oxygen present within their bladder as an emergency backup in times of urgent need, although, this emergency store can only be of aid for a few minutes (Jones 1957).      Finally, swimbladders in some fish are known to increase hearing abilities.  With the presence of inner ear- swimbladder connections, these fish have exhibited greater sensitivity to sound, however it is not yet clear whether there is also an increase in frequency selectivity (Coombs & Popper 1982a) Disadvantages      One disadvantage of having a swimbladder is that neutral buoyancy can only be achieved at a small range of depths specific to certain fishes.  If a fish swims below its buoyancy range, it will have to expend greater energy in the exercise of swimming in order to keep from sinking.  On the other hand, if a fish swims above its upper buoyancy level, it becomes overly buoyant.  Its swimbladder would expand to such a great capacity that the fish might be thrown out of control if it does not compensate for this increased buoyancy by vigorously swimming downward.  The fuller the swimbladder gets, the more tipsy the fish is-- much like a large helium balloon.  Therefore, many fish that do not have a swimbladder, such as the Atlantic mackerel, have greater depth flexibility and speed in moving through columns of water.  A swimbladder would only serve as a constraint for these fish which are continuously active predators (Schmidt-Nielson 1997).      One other disadvantage of having a swimbladder is that oftentimes the bladder serves as an acoustical target which sounds can be bounced off of.  This might enable predators to more easily locate the fish (Schaefer & Oliver 1998).

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