REPORT OF DIRECTOR AND STATE GEOLOGIST 1900 r223 



RATE OF GROWTH OF FISHES 



The rate of growth of fishes is by no means satisfactorily 



determined. It is generally computed by measuring at intervals 



^a few kept in captivity. But this is measuring the rate of 



growth of fishes in abnormal conditions. Knowledge of the 



natural rate of growth is alone of value. 



Masterman and Mcintosh claim that the rate can be obtained 

 more accurately by comparing the average lengths of large 

 numbers taken at different times ; but this average length is an 

 artificial standard. It would be more correct to compare the 

 lengths of the greatest number measured at different times. 

 Thus out of 500 Fundulus examined about July 15 more meas- 

 ured 2.1 centimeters than any other length. This was the 

 modal length then for Fundulus at that time. Six weeks later 

 out of an equal number taken more measured 3.2 centimeters; 

 the growth during the six weeks being the difference between 

 3.2 centimeters and 2.1 centimeters, or 1.1 centimeter. 



Of 200 menhaden taken on July 31 the modal length was 6 

 centimeters. On August 28, the modal length was 7.8 centi- 

 meters. This species is thus shown to have a growth of 2 centi- 

 meters during that month. 



It was found impossible to get other species in sufficient 

 numbers to use this method but that is no objection to . the 

 method for it is necessary to obtain large numbers in ascertain- 

 ing the average length. The objection to the average length is 

 that it does not exist in nature whereas the model length is that 

 length most specimens of a certain catch have reached at the 

 time they are taken. 



PARASITISM 



A number of fishes were examined at the Fulton market for 

 parasites. By far the greater number of the parasites were 

 Ascarids but the number of the species of this form is so great 

 that it has not been possible to ascertain the species. The 

 Ascarids were found on the gills, cavity of the stomach, lumen 

 of the intestine, in the body cavity and even between the muscle 

 fibers and beneath the epidermis. Some occurred encysted on 



