The Fishery for Blue Crabs in the St. Johns River, Florida, 



With Special Reference to Fluctuation 



in Yield Between 1961 and 1962 



By 

 MARLIN E. TAGATZ 



ABSTRACT 



The Bureau of Commercial Fisheries began studying the blue crab in 1957 to 

 determine factors affecting the abundance of marketable -size crabs. In 1 96 1 a field 

 station for studying the blue crab and its fishery in the St. Johns River was estab- 

 lished at Green Cove Springs, Fla. 



A description of the commercial fishery for blue crabs in the St. Johns River 

 is presented together with the statistics of the fishery for 1961 and 1962. The catch 

 was 1,384,579 pounds in 1961 and 3,231,569 pounds in 1962 (an increase of 133 per- 

 cent). The effort of fishermen fishing pots in 1962 was 68 percent greater than in 

 1961 and the effort of trawlers was 109 percent higher. 



The factors primarily responsible for determining the size of the 1961 and 1962 

 catches were market conditions, migrations, and population size. Market conditions 

 included changes in demand, the availability of outlets, and price. Movements of 

 immature and mature crabs into fishing areas, and the length of stay, affected 

 utilization by the fishery. Data oncatchper standard unit of effort indicated fluctua- 

 tions in population size between years. 



Commercial catches were sampled during 1961 and 1962 to determine the sex 

 ratio, width, and weight of blue crabs. Comparisons were made between unculled 

 catches of crabs and those sold to dealers to define better the difference between 

 the commercial marketable-size and the size of crabs actually caught. 



INTRODUCTION 



The blue crab, Callinectes sapidus , supports 

 one of the most important fisheries of the 

 United States. In 1961, 10,000 fishermen caught 

 153 million pounds of blue crabs valued at over 

 $8 million to the fishermen. The blue crab 

 ranges as far north as Nova Scotia but is found 

 in greatest abundance from Delaware Bay to 

 Texas. In Delaware and Chesapeake Bays, 

 where year-round crab fisheries have long been 

 established, more pounds of blue crabs are 

 landed than of any other species of fish or 

 shellfish except menhaden. More recently, a 

 major fishery for blue crabs has developed in 

 the South Atlantic States, where- it is also 

 second in poundage only to menhaden, and its 

 dollar value, as a food species, is exceeded 

 only by shrimp. The blue crab supports the 

 most rapidly expanding fishery in Florida. A 

 production of 25.6 million pounds in I960 was 

 four times that of 10 years ago and more than 

 double that of 1957 (Rosen and Robinson, 1961). 



Records of annual landings of blue crabs 

 have been maintained since before 1900. Large 



Note. — Marlin E. Tagatz, Fishery Biologist (Research), 

 Bureau of Commercial Fisheries Biological Laboratory, 

 Beaufort, N.C. 



and sudden fluctuations in supply have raised 

 serious economic problems for the industry. 

 Efforts to predict these fluctuations, or to con- 

 trol them by restrictive regulations, have been 

 largely unsuccessful. Concerned over the in- 

 stability of the crab supply, the Atlantic States 

 Marine Fisheries Commission initiated action 

 that resulted in a study of blue crabs in the 

 South Atlantic States. The Bureau of Commer- 

 cial Fisheries, as the primary research agency 

 of the Commission, began this study in 1957 at 

 its biological laboratory in Beaufort, N.C. To 

 investigate the St. Johns River blue crab, a 

 field station was established at Green Cove 

 Springs, Fla., in 1961. 



Studies were begun on the blue crab in the 

 St. Johns River to determine the life history, 

 the nature of the fishery, and natural factors 

 that affect the size of the fishable population. 

 This report is concerned primarily with the 

 study of the fishery. The management of the 

 fishery and the development of methods to 

 predict yield require detailed statistics of 

 fishing operations. Reliable catch and effort 

 data are necessary in any attempt to determine 

 year-to-year fluctuations in abundance when 

 actual population size is not known. The con- 

 tribution of factors that affect abundance can 

 then be judged. Data on sex and size composition 



