ESTIMATES OF ABUNDANCE 



The most recent strong year class of At- 

 lantic menhaden was that of 1958. In the ab- 

 sence of a strong year class, the catch will 

 consist mainly of menhaden less than 3 years 

 old. Even with the appearance of a strong 

 year class, the catch would consist mainly of 

 menhaden less than 3 years old for at least 

 2 additional years. Since age-0 menhaden 

 have always been relatively unimportant in 

 the catch, it will be the age- 1 and -2 fish, 

 or the 1963 and 1964 year classes, which 

 will make up the bulk of the catch in 1965. 

 The 1963 year class of menhaden, caught as 

 age- 1 fish in 1964, was not particularly 

 strong. The catch of age- 1 fish was less 

 than in 1964 in only 2 years since 1955 in the 

 South Atlantic Area and in only 1 year since 

 1955 in the Chesapeake Bay Area (even though 

 fishing intensity was the highest on record in 

 the Chesapeake Bay Area in 1964). 



A project has been started to estimate the 

 relative abundance of 0-group, or juvenile 

 menhaden, in various Atlantic coast estuaries 

 1 year before they enter the fishery. Several 

 estimates are made each year based on 

 (1) trawling, (2) haul seining, (3) marking and 

 recovery of juveniles, and (4) counting schools 

 of juveniles from an airplane. Estimates were 

 made by haul seining and marking for the 1961 

 year class and by allmethods for the 1962, 1963, 

 and 1964 year classes. Because the data have 

 been compiled for only a few years, wehave not 

 been able to assess fully the reliability of the 

 estimates for predicting the contribution of 

 each year class to the fishery. 



Trawling, the first method used each year, 

 usually is begun in June and repeated in some 

 estuaries in July and August. 3 The trawl, sim- 

 ilar to one described by Massmann, Ladd, and 

 McCutcheon (1952), has anopening about 24 feet 

 wide by 3j feet high. The net is towed between 

 two outboard motor boats; three to six tows of 

 5 minutes each are made in an estuary during 

 each survey. For most estuaries, the mean 

 number of juvenile menhaden caught per tow 

 was lower in 1964 than in 1963 (table 2). 



Estimates by haul seining, and by marking 

 and recovery are made during July and August. 

 About 30 to 40 hauls are made in each loca- 

 tion, over a 4-day period. The mean catch 

 per seine haul and the population estimate 

 based on marking and recovery of juveniles 

 appear to vary in a similar manner; therefore, 

 the estimates based on marking are not pre- 

 sented here. The reduction in the catch in 

 1964 was more pronounced in haul seines 

 (table 3) than it was in trawls (table 2). 



30bservations of juvenile Atlantic menhaden based on 

 surface trawl catches in Bath Creek, N.C, by A. L. 

 Pacheco. Unpublished manuscript, U.S. Fish and Wildlife 

 Service, Bureau of Commercial Fisheries Biological 

 Laboratory, Beaufort, N.C. 



Table 2. --Average number of juvenile menhaden 

 caught per 5 -minute trawl tow in selected 

 Atlantic coast estuaries in June, 1963 and 

 1964 



Estuary 



Sawmill, S.C. 

 Meggetts, S.C. 

 Calabash, N.C. 

 Broad, N.C. .. 

 Bath, N.C. ... 

 Felgate, Va. . 



Ball, Va 



Colbourn, Md. 

 White, Del. .. 



1963 



Number 



1964 



Number 



Table 3. — Average number of juvenile menhaden 

 caught per seine haul in selected Atlantic 

 coast estuaries, July and August, 1963 and 

 1964 



Estimates of abundance also are made 

 each fall by counting schools of juvenile men- 

 haden from an airplane. Briefly, the observer 

 estimates the area, in square feet, of each 

 menhaden school sighted along a prescribed 

 flight path. The total square feet divided by 

 the miles of flight gives an estimated number 

 of square feet of juvenile menhaden per mile. 

 Data for 1963 and 1964 are shown in table 4. 

 Some areas have more than one estimate 

 shown each year, for observations made on 

 different dates. A decrease in the area of 

 manhaden schools in 1964 is apparent. 



In the 10 years since the start of the Atlan- 

 tic menhaden investigations, significant con- 

 tributions have been made to the biological 

 knowledge of this species and to an under- 

 standing of the relations between the fishery 

 and the stocks. However, the current increased 

 fishing intensity on young fish, decreased 

 catches, and shift in the area of greatest 

 catch have raised certain important ques- 

 tions, such as: (1) Is there overfishing, (2) 

 what are the interrelations of the stocks in 

 the different areas, and (3) what are the ef- 

 fects of water temperature, salinity, and water 

 currents during spawning on survival of a 

 year class? These questions cannot be an- 

 swered completely without increased research. 



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