enhancement programs dealing with one species must be aware and account for 

 the possible effect of dealing with a complex of stocks and that a single stock 

 may not be representative of a species. 



Within a population (stock) of a given species, the size of the population 

 is determined by a number of factors, especially natural mortality, recruitment, 

 and growth. In the case of a commercially important species, man's fishing 

 activities represent mortality to the population. Basically, stock enhancement 

 involves procedures whereby the total amount of edible product (bioraass) is 

 increased by increasing the number of animals and/or the size of the animals 

 in the population. , A number of general techniques for stock enhancement have 

 been proposed. These will be introduced now because of their general application, 

 but specific suggestions will be made later when each species is discussed. 



1) Control of harvest. If the amount of biomass removed from the stock 



is properly regulated, then the maximum sustainable yield (MSY) can be achieved. 

 However, a depleted stock, such as haddock, might increase in biomass by natural 

 processes if the amount of fishing is decreased. The levels of harvest are not 

 always easily determined and must be evaluated constantly. 



2) Recruitment. To assist a natural population in attaining a maximal 

 size consistent with the marine ecosystem, additional individuals can be added 

 to the population (stock) . In hatcheries, many individuals can be reared under 

 man-controlled conditions and released into the natural environment. One early 

 attempt at stock enhancement was to culture fertilized eggs and young stages 

 and to release them into the waters. This approach, however, does not insure 

 adequate recruitment in all species because of high predation and environmental 

 hazards encountered by very young stages. The release of individuals in more 

 advanced stages of development normally increases their chances of reaching 

 marketable size. Excellent examples of successful hatchery programs are those 



