ECONOMICS OF THE FISHERIES 317 



important, but the lack of concentration, and often the seasonal nature of 

 supply, present many of the most serious hindrances to development of the 

 fisheries. These conditions prevail along much of the shore line of the 

 North American continent. 



Selectivity of Methods of Capture. To exploit the complicated source of 

 wealth in the sea, the fishermen use gear which has varying degrees of 

 selectivity. A purse seine is quite specific for schools of fish at the surface. 

 The haul seine catches whatever is larger than the meshes of the net that en- 

 counters it; a pond net, weir or trap catches some part of anything that hap- 

 pens to be moving in a way to be intercepted by the leader ; a trawl catches 

 all the bottom fish which do not escape, in a narrow strip of bottom up to a 

 height of six to eight feet; hooks catch whatever fish are attracted by the bait 

 and with mouth big enough to take it; crab trot lines catch only crabs; "pots" 

 or small cages catch lobsters, crabs, eels, sea bass, etc., depending on where 

 they are set. 



The fisherman is therefore not altogether free to produce and sell what 

 the market seems to want, especially of finfish. With the catch-all types of 

 gear he catches whatever happens to be present at the time and place, and 

 wherever he uses his gear he produces in most cases several or many kinds 

 of fish, which may not be the most desirable assortment, but which never- 

 theless he must sell, if he can. "Trash" fish, for which there is no market 

 or which are not economically worth while, are discarded at sea. If they are, 

 they may be food for other fishes as truly as they would be if consumed 

 alive by enemies. For these reasons, among many reasons, the forces of 

 supply and demand are only weakly operative for particular kinds of fish. 

 Economically as well as biologically the totality of useful fish of a region 

 tend to behave collectively. 



Versatility of Methods and of Opportunities of Capture. Fishermen, how- 

 ever, do have some choice of what they catch. In the case of gill nets they 

 can make the size of the meshes to catch a predetermined size of fish. They 

 can drift them at the surface or sink them to the bottom. Variation of the 

 mesh of trawls, seines, pounds, nets, etc., also may allow small fish to escape 

 dead or alive. Minimum sizes of mesh are in many cases fixed by law. 



Perhaps the most important controllable variable is the choice of time 

 and place of fishing and, of course, appropriate gear and methods. By 

 experience, fishermen learn that certain kinds of fish are more likely to be 

 found at certain times and places, and to that extent can increase the produc- 

 tion of them at will, but selectivity is never complete — "odd varieties" of 

 fish other than those mainly sought are taken and must be disposed of. We 

 shall see in the Section on Marketing that many kinds of finfish enter the 

 same competitive markets, and are substituents one for another; that few 

 fishes possess peculiar consumer appeal that cannot be substituted by other 



