JUNE; ATLANTIC MENHADEN GROUPINGS 



October (Roithmayr, 1963; June and Nichol- 

 son, 1964; Nicholson, 1971a). 



Single-set catches from fall school-aggrega- 

 tions, on the average, were larger than single- 

 school summer catches. A plot, by 3-ton size 

 classes, of 138 single-set catches made from large 

 fall school-aggregations that appeared off Long 

 Island shows a marked difference in the shape 

 of the frequency polygon when compared with 

 that of single-school summer catches in the 

 North Atlantic Area (lower and middle panels, 

 Figure 3). The ranges of the two distributions 

 are nearly identical (3 to 102 metric tons for 

 the fall school-aggregations) , but the curve rep- 

 resenting fall school-aggregations is more sym- 

 metrical and its mode considerably higher (40- 

 to 42-ton size class) and in much closer agree- 

 ment with the mean of the distribution (44.4 

 metric tons) . Moreover, single-set catches from 

 fall school-aggregations, on the average, were 

 over twice as large, and the standard deviation 

 of their frequency distribution was V/o times 

 greater than that of single-school summer catch- 

 es in the North Atlantic Area (Table 2). Com- 

 parisons within years show the mean catch from 

 fall school-aggregations to be from II/2 to 31/0 

 times larger than the mean single-school sum- 

 mer catch in the North Atlantic Area. 



Differentiation of summer schools and fall 

 school-aggregations was also indicated by the 

 fact that the mean single-school summer catch 

 in the North Atlantic Area decreased over the 

 8-year period, whereas the mean single-set catch 

 from the fall school-aggregations off Long Island 

 generally increased (cf. Tables 1 and 2). Al- 

 though the two seasonal catches were negatively 

 correlated (r = — 0.228), the coefficient has no 

 statistical significance. 



Following the disappearance of the fish from 

 coastal waters of southern Long Island and else- 



10 



5 - 



>. 



North Carolina (fall) 

 n = 248 



North Atlantic Areo (summer) 

 n = 605 



Long Island (fall) 

 = 138 



I I I I I I I I I I 



I I 



38 50 62 74 86 98 IK) 122 134 146 158 170 



Catch per Single-School Set (MT) 



162 



Figure 3. — Percentage size-frequency distributions of 

 138 single-set purse-seine catches of Atlantic menhaden 

 from fall school-aggregations off Long Island (lower 

 panel), 605 single-school summer catches in the North 

 Atlantic Area (middle panel), and 248 single-set catches 

 from fall school-aggregations off North Carolina (upper 

 panel), 1955-62. 



where in October, large school-aggregations re- 

 appeared off the coast of North Carolina in No- 

 vember of every year. These aggregations were 

 usually first intercepted by the fishing fleet in 

 the vicinity of Cape Hatteras, N.C., and fished 

 as they moved southwestward along the coast 

 until they disappeared oflf Cape Fear, N.C., in 

 December or early January (Roithmayr, 1963; 

 Nicholson, 1971b). 



Single-set catches from fall school-aggrega- 

 tions off North Carolina, on the average, were 

 the largest recorded along the Atlantic coast. 

 A plot of 248 catches (upper panel, Figure 3) 

 shows a range of 1.5 to 180 tons. The grand 

 mean for the 8-year period was 54.2 tons, with 

 a standard deviation of 37.63 tons. Thus, these 

 catches, on the average, were from three to near- 

 ly five times heavier than single-school summer 



Table 2. — Mean size of catches of Atlantic menhaden from 138 purse-seine sets on fall school-aggregations off Long 

 Island and 248 sets on fall school-aggregations off North Carolina, 1955-62. The number of sets used in calculating 

 the means are given in parentheses. 



703 



