BERRIEN; EGGS AND LARVAE OF SCOMBER 



ATLANTIC MACKEREL 

 EGGS/STATION 



time sequence of sampling. We sampled transect E 

 as much as 4 days after transects G, H, and K, and 

 8 or 9 days after transect D. If we had progressed 

 southward over the whole cruise, the young taken 

 on transect E probably would have been smaller 

 by 8 or 9 mm and intermediate between the 

 lengths of those found on transects D and G, as- 

 suming Sette's (1943) calculated growth rate of 

 about 1.0 mm/day in 20- to 30-mm S. scombrus is 

 correct. 



During August we took S. scombrus larvae only 

 on the two northernmost transects, off Martha's 

 Vineyard and Montauk Point between about 10 

 and 90 km offshore. Relatively few larvae were 

 caught, 76 in all. They were small, ranging from 

 2.6 to 7.7 mm with a mode of 3.0 to 3.9 mm long. 



Because 1) no S. scombrus eggs were taken on 

 the August cruise and 2) larvae occurred only near 

 the northeastern extreme of sampling at a time 

 when the adults are knowm to be migrating toward 

 the north and east, it follows that these larvae may 

 have resulted from the last spawning within our 

 survey area for 1966. In fact, they may have been 

 spawned northeast of the survey area, for Bumpus 

 and Lauzier (1965) report a southwesterly drift in 

 continental shelf waters off Rhode Island and 

 Long Island, N.Y., in August. 



Scomber scombrus. Catch Characteristics 



Statistical tests were run on catch characteris- 

 tics, in order to summarize the data. These tests 

 included: 1 ) comparison of catch sizes by net 1 (0 to 

 15 m) versus those by net 2 ( 18 to 33 m) for eggs; 2) 

 the same comparison for larvae; 3) comparison of 

 larva lengths taken by net 1 versus net 2 during 

 day; 4) the same comparison during night; and 5) 

 comparison of larva lengths taken during day ver- 

 sus those taken during night. Because the samples 

 were collected by open nets, net 2 catches were 

 corrected for contamination. 



Results of tests 1 and 2 showed significant dif- 

 ferences in the catch between nets 1 and 2. Net 1 

 caught 2.3 times as many eggs (chi- 

 square = 1,533.956, P<0.005, with 19 df) and 6.1 

 times as many larvae (chi-square = 1,360.618, 

 P<0.005, with 26 df) as net 2. The larger catch in 

 the 0- to 15-m (net 1) tow is probably related to the 

 occurrence of most eggs and larvae of iS. scombrus 



Figure 5. — Distribution of Scomber scombms eggs and selected 

 surface isotherms (°C) during May 1966. 



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