10 



80 



ABUNDANT 



COMMON _ 



SCARCE 



ABUNDANT - 



COMMON 



SCARCE 



- 10.0 



8.0 



6.0 



4.0 



- 2.0 



- 00 



- - 2.0 



- ABUNDANT 



— COMMON 



_ SCARCE 



- ABUNDANT 



_ COMMON 



- SCARCE 



Figure 2. — Comparison of annual mean temperatures and lowest monthly mean temperature for each of the j'ears 

 1905-67, with the abundances of green crabs and soft-shell clams. Equal levels of abundance occurring at the same 

 time and place are shown as slightly displaced lines. 



Estimates of the abundance of clams from 1949 

 through 1967 were ftirnished by biologists of the 

 Maine Department of Sea and Shore Fisheries. 



QUANTITATIVE SAMPLING 



BCT biologists used standardized methods to 

 trap crabs in various locations from 1953 through 

 1960 and 1965 through 1967. The specially de- 

 signed traps (fig. 3) were built to the same dimen- 



sions, were baited with 4.5 kg. of fresh or frozen 

 herring each day, and were fished at the same 

 locations in the same depth of water each time. 

 The traps were fished for 24 hours on 2 consecu- 

 tive days diu-ing the first week of each month from 

 late spring to late fall, when the crabs were most 

 active. The catch and old bait were removed each 

 day. The crabs were sexed, counted, measured, 

 and destroyed. The catch per trap per day, used 



CHANGES IX GREEX CRAB ABUNDANCE IN RELATION TO RECENT TE.Ml'ERATl'RE CHANGES 



339 



