96 RATE OF GROWTH OP SOME SEA FISHES 



depths with the shrimp-trawl and a small-meshed otter-trawl, and 

 have also worked a large tow-net, 8 feet by 6 feet in area at 

 the mouth, at various distances from the coast. Knowing the 

 spawning time of each species I have been able to determine the 

 age of the young specimens collected in a number of cases with 

 more or less certainty. Often there is no doubt as to the age 

 within a month or so of young- specimens of the same year's brood, 

 and it is often possible to say that small fish which are too large to 

 be derived from the last spawning period, for instance those col- 

 lected at the spawning period itself or a little later, must be a year 

 old or a little over. But it is difficult in this way to ascertain the 

 maximum growth for one year, since a number of specimens of one 

 species often form a continuous series in size, and it becomes diffi- 

 cult or impossible to say where those of one year old end and those 

 of two years begin. 



In order to get more certainty on the question, I have been rear- 

 ing specimens of known age of as many species as possible in the 

 tanks of the aquarium. The first results of these experiments were 

 published in this Journal, vol. i, p. 370. Many of the flounders and 

 other fish mentioned there are still alive. It is, of course, a ques- 

 tion in the case of each species how far the growth of specimens in 

 captivity is normal, whether it exceeds or falls short of the growth 

 of those living in the free state. This question can only be 

 answered by comparing the size of captive specimens with that of 

 young specimens collected from the sea at various times of the year. 



I have recorded the place of capture as well as the size of the 

 specimens collected, and am able therefore in some cases to confirm 

 and in others to add to the results obtained by Dr. Fulton. In a 

 few cases I have had opportunities of determining the minimum size 

 of ripe specimens with results which sometimes differ from Dr. 

 Fulton's, a difference doubtless due in part to the difference of the 

 districts in which our observations have been made. 



Another subject I have discussed is the relation between age and 

 sexual maturity. It is not at present known whether flat fishes for 

 instance begin to breed at one year of age or at two, or whether 

 some breed at one year and others at two according to the size they 

 reach in the time. Some species again may have a more uniform 

 growth than others, and all breed at the end of their first year, 

 while other species do not breed till a later age. 



I have given below, in tabular form, the details I have collected 

 up to the present time concerning the several species. The majority 

 of the species considered, belong to the families Pleuronectidae and 

 Gadidge, and I have more data referring to the flat fishes than to any 

 other species. With the exception of Caranx trachurus all the 



