42 MARKETABLE BRITISH MARINE FISHES 



disprove. The capture at marketable size of one in a thousand 

 of the fry liberated, means 200 from each spawner in the hatchery 

 every year. It may well be doubted that so high a proportion 

 is possible. If there were no fishery by man the species would 

 soon reach its limit of increase, and then on the average each 

 pair of mature plaice would produce only two mature offspring 

 to succeed them. This would mean a survival of two out of 

 200,000 eggs supposing each female spawned only once. But in 

 the first place fish are marketable before they are mature, and 

 therefore more than two marketable fish would survive, and in 

 the second place the species being below its possible abundance 

 excess of food is available, so that probably a greater proportion 

 survive to marketable size. Then again, the eggs and fry are 

 protected in the hatchery. But taking all these facts into con- 

 sideration we may well doubt w^iether more than fifty out of the 

 fry derived from each spawner in one season reach marketable 

 size, and then we have to consider what proportion of these 

 would be caught. 



At present then it must be held that artificial propagation is 

 in its experimental stage. There is good evidence that it pro- 

 duces local increase in the fish supply, the fish hatched in a 

 particular place being carried or migrating to other definite 

 areas in particular directions in consequence of currents, the 

 habits of the fish, &c. It is possible therefore, if proper in- 

 vestigation be made, to trace out the history of the fry liberated 

 from a hatchery, and to prove definitely what proportion of 

 increase in the abundance of fish is produced by its means in 

 particular localities. In future inquiries two points ought to 

 receive attention with regard to the question whether the mere 

 hatching of the eggs and protecting the fry for the few days 

 before the absorption of the yolk is of very great benefit. The 

 first point is the possibility of feeding and rearing the larvje 

 until they have gone through their transformation, and even 

 until they are marketable. In this way a smaller percentage of 

 loss in the larval and young stages than occurs in the natural 

 conditions might be obtained, in other words longer and greater 

 protection afforded. The second point is whether cheaper and 

 larger results might not be produced by taking a very much 

 greater number of spawners, and merely putting the fertilised 

 eggs into the sea in vast quantities. Hitherto, notwithstanding 



