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Part III. — Fifteenth Annual Report 



the benefit that may be derived from such operations. In Norway, the 

 1 latching work was originally started quite experimentally, and on a 

 small scale ; it was necessary tirst to find out what difficulties there 

 would be to overcome ; the station was subsequently very much ex- 

 tended (in 1890) in order to show what practical results could be pro- 

 duced. Operations have now gone on for some years, and considerable 

 numbers of fry of the cod have been distributed in the inshore waters 

 along the south-east coast. The largest production in a season has been 

 320,000,000 fry, which were sent out from the hatchery last year ; and 

 a marked increase in the abundance of young cod has been observed 

 where fry has been distributed in great numbers. But it would he of the 

 greatest interest to have such experiments done that would more definitely 

 show the effect on the abundance of fish when fry were distributed 

 in a certain area. This would be a statistical test of the economy of sea- 

 Hsh hatching. When carried out on a large scale, as it ought to be when 

 practical results are looked for in the way of an increased fish supply, 

 the fry can be produced at a very moderate cost ; as an illustration it may 

 be mentioned, that at the Flodevig hatchery during 1896, 320,000,000 

 cod fry were produced at the rate of more than 2,500 for a penny. But 

 in order to work so cheaply it is necessary to have the station furnished 

 with sufficient tanks and reservoirs, where the parent fishes may be 

 retained safely from one year to another. And I must also mention, 

 as easily may be seen, that once the capital expenditure is made, it will 

 not cost much more to hatch 300,000,000 of fry than it will cost to pro- 

 duce say 60,000,000 a year. 



From statements sometimes made it seems that some misapprehen- 

 sion exists as to the principles of fish culture, It has been said that 

 the fishes produce such large numbers of eggs that the quantity of 

 fry that may be developed artificially will have very little effect upon the 

 abundance of fish in a certain area. Practical experiments have shown 

 differently in such places where hatching work has been carried out on a 

 large scale, and this experience may easily be accounted for. In order to 

 maintain the equilibrium or balance within a species, it is necessary that 

 on the average two adult individuals remain as the offspring from one male 

 and one female fish ; and this will apply to any species. We find that a 

 cod will produce more than one hundred times as many eggs in a season as 

 a herring, and the destruction of cod eggs or larvae must therefore be about 

 one hundred times as great as the destruction of herring eggs or larvae. 

 Many similar instances could be mentioned, which all would tend to show 

 that the destruction of pelagic fish eggs and their larvae must be enor- 

 mous. As clearly shown by Dr Fulton in a papeff on the principles of 

 fish culture, the number of eggs produced by any fish is the best measure 

 of the destruction that must take place. And that this destruction takes 

 place at an early period is most probable. The newly born viviparous 

 blenny (Zoarces) measures about 2 inches, and when only 100, or at the most, 

 120 embryos of this size, which are found in a female fish, are sufficient to 

 maintain the species, it is clear that these 120 young blennies must have 

 the same chance of reaching maturity as 6,000,000 of eggs produced by a 

 turbot or any other fish in a season ; in other words, one newly bom 

 blenny, about 2 inches long, is equal to 50,000 of such fish eggs ; or, 

 that out of 50,000 such eggs the 49,999 are destroyed before they reach a 

 stage similar to that of a new-born blenny. 



If we take the case of the flat-fishes, which are of most interest to this 

 country, we will find that the young fish is very hardy, and has got good 

 means of protection. From the moment it has passed the transformation 

 stage it lives regularly on the bottom. The pigmentation on the upper 



