Other Game Fish 205 



obtained, mostly well up rivers or from landlocked waters 

 formerly connected with the sea. These specimens, and others 

 of larger size, have been studied, and good evidence obtained 

 that their age can be assessed from the annuli which appear 

 on their scales. When it is realized that the water tempera- 

 ture at Boca Grande, Florida, ranges from a high of 93 de- 

 grees in summer to a low of 59 degrees in winter, and that 

 there is a seasonal change in the availability of the various 

 food forms, it is not surprising that there is a change in the 

 growth rate which would show on the scales. 



According to scale readings, tarpon reach a length of ten 

 inches at the end of the first year, twenty inches at the end 

 of the second, thirty inches at the end of the third. They 

 probably start spawning in their sixth or seventh year, when 

 they are about four feet long, and it is at this time that they 

 play the largest part in the catch. However, there is evi- 

 dence that angling is not heavy enough to deplete their num- 

 bers to a dangerous extent. Ten-year-old fish are not un- 

 common, and average five feet in length. The oldest fish 

 found in the course of scale examination had reached its 

 fifteenth year. 



One of the most startling facts recently discovered about 

 the tarpon has to do with its air-bladder. As we have seen 

 in Chapter VI, this is well supplied with blood vessels and 

 has an open connection with the gullet which enables little 

 tarpon trapped in landlocked lagoons where the water is 

 almost devoid of oxygen to survive by coming to the surface 

 for air. Experiments have now shown that even in well- 

 oxygenated sea water these fish rise periodically for air — 

 adults on the average of five times per hour, younger fish 

 more frequently. If prevented from coming to the surface, 

 they perish — in the experiments, within from seven to 128 

 hours. Like human beings, they must have airj if held under 

 water too long, they drown. 



