Stock Enhancement 



The Fishery Conservation and Management 

 Act of 1976 could be a stimulus for com- 

 prehensive stock enhancement programs 

 which would improve many of the U.S. fish- 

 eries. For example, the National Marine Fish- 

 eries Service (NMFS) has projected that en- 

 hancement could result in the ultimate 

 restoration and a 100 percent increase in the 

 catch of U.S. groundfish.86 



Basically stock enhancement is the use of 

 procedures which will increase the total 

 amount of edible biomass by increasing the 

 number of fish and/or the size of fish in the 

 population. 



Stock enhancement is a complex subject, 

 and in spite of erratic periods of intense in- 

 terest by various private and governmental 

 groups, detailed studies are not numerous. In 

 general, certain fisheries, such as salmon, are 

 better understood in terms of stock enhance- 

 ment than others. Various reasons can be 

 given for this lack of data, but one major fac- 

 tor is the problem of control and recovery of 

 stock by the government responsible for the 

 enhancement activities. By extending fishery 

 jurisdiction to 200 miles, the United States has 

 taken control over the fisheries which would 

 benefit from enhancement and has assured 

 that U.S. citizens or permit holders could reap 

 the harvest of stocking programs. 



There are a number of commercially impor- 

 tant species which could benefit from en- 

 hancement programs. Some of these are cod, 

 haddock, yellowtail and blackback flounder, 

 ocean perch, pollock. Gulf shrimp. Pacific 

 salmon, Alaska crab, Atlantic herring, and 

 Pacific pollock. 87 Enhancement possibilities 

 and the benefits to be gained are different for 

 each. These species were selected somewhat 

 arbitrarily in order to study enhancement 

 possibilities as described in OTA Working 



Paper No. 4. The heavy fishing of these species 

 in the past, with the depletion of stocks of 

 some, and the existing well-developed 

 markets for products of these species make 

 them likely targets for enhancement. 

 However, if a comprehensive program were 

 to be undertaken in reality, careful analysis 

 should go into the selection of the species for 

 enhancement and the specific enhancement 

 methods to be used with each species. 



The most commonly used methods of en- 

 hancement are control of the harvest, recruit- 

 ment, development of new stocks, habitat 

 management, and aquaculture. The following 

 is a brief description of how each of these 

 methods is used: 



1) Control of harvest: If the amount of 

 biomass removed from the stock is prop- 

 erly regulated, then the maximum sus- 

 tainable yield 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 which allow this natural 

 recovery are not always easily deter- 

 mined and must be evaluated constantly. 



2) Recruitmmt: to Assist a natural popula- 

 tion in attaining a maximal size consist- 

 ent with the marine ecosystem, addi- 

 tional fish can be added to the stock. 

 Many fish can be reared in hatcheries 

 under man-controlled conditions and 

 then released into the natural environ- 

 ment when they are large enough to sur- 

 vive the predation and environmental 

 hazards encountered by very young fish. 

 Hatchery programs related to Pacific 

 Coast salmon and many freshwater 

 species, such as trout and bass, provide 

 excellent examples of successful recruit- 

 ment. Unfortunately, many marine 

 species have not yet been reared under 

 hatchery conditions although some at- 

 tempts have been made. 



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