BIOLOGY AND NATURAL HISTORY 135 



ocean. Where do they spend the winter? What do they feed on? How fast do 

 they grow? And what is the natural mortality? 



In the sounds, more observations have been made, and knowledge of the 

 life histories in these waters is further advanced, although still inadequate. 

 Interspecies food relationships — a most important factor in fisheries man- 

 agement- — are known on the basis of examination of stomach contents of 

 very few fish, and these mostly adult. 



Magnitudes of population and fishing mortality cannot be determined on 

 the basis of the present inadequate records of catch and effort, and no data 

 are available for estimating trends in average size or age composition of the 

 commercial catch. ^ We do not have the information on which to determine 

 whether or not the present fishing intensity and commercial catch represent 

 a wise utilization of the finfish resources. 



The following recommendations are made for future study of the finfish 

 in North Carolina waters: 



MIGRATIONS. More observations should be made of the movements of 

 fish after they leave the inside waters in the fall. Do they move south or do 

 they spend the winter off the North Carolina coast, and if so, where? Knowl- 

 edge of location of the winter grounds may open up new possibilities for 

 the industry. Limited trawling operations in the Cape Lookout area during 

 early 1949 produced some fair catches of croakers, spot, flounder, trout, 

 and sea mullet. We must know more about the extent of the winter popula- 

 tion. Are more fish to be found in deeper waters? Present trawling is com- 

 monly limited to about 20 fathoms. Are the fish located in other areas of 

 trawlable bottoms? Answers to these questions should be sought. 



FOOD OF FISHES. Studies should be made of the food and feeding habits of 

 the commercially important species at various stages of growth. To what 

 extent is each utilized as food by other fishes? How many young shad and 

 alewives are eaten by striped bass, and how many shrimp by gray trout? 

 Is it wise economy, on any reasonable assumption as to what the food con- 

 version factor is,^ to protect the predatory species; or would it be advan- 

 tageous to promote the exploitation of them as indirect protection of those 

 species in the food chain which are closer to the basic production? Detailed 

 food and growth studies should clarify these interspecies relationships. 



ABUNDANCE. It is desirable to know more about the quantity of fish avail- 

 able to the industry and what fluctuations in abundance occur. We have for 

 certain years records of the catch, but as indication of the effort used in 



2. The best indication of an over-fished population is a decrease in catch per unit effort. 

 Lacking catch per unit effort data, the size and age composition of the catch may be used as 

 criteria. A population which is being over-fished will yield smaller and younger fish. 



3. The usual assumption is that it takes 10 pounds of food to produce a pound of fish — 

 although this figure is only an estimate and undoubtedly varies considerably according to species 

 and individuals. 



