500 

 400 

 300 

 200 

 100 



Jonesport, Maine 



J I I I — ' 



Trenton, Maine 



800 

 700 

 600 

 500 

 400 

 300 

 200 

 100- 

 



Plum Island Sound, Massachusetts 



_1 1 I I L_ 



1954 1956 1958 I960 1962 1964 1966 



Figure 4. — Greatest monthly mean catch of green crabs 

 per trap per day in each year, 1953-67. Locations are 

 arranged from northeast (top) to southwest (bottom). 

 Broken hnes indicate periods when no trapping was done. 



end of the period. In Canada, MacPhail et al. 

 (1955) fished two traps daily for 24 days and re- 

 moved 14,915 crabs without a drop in catch. It 

 ajjpears that, in areas where crabs are generally 

 abundant, they move about sufficiently to fill any 

 gap temporarily caused by trapping. 



The most radical changes in abundance have 

 been in Canada and northeastern Maine. During 

 the summer of 1954, MacPhail et al. (1955) trapped 

 an average of 343 crabs per trap per day for 24 

 days in a rocky area of the Bocabec River in 

 New Brunswick, Canada. Soon after 1954 the 

 green crab population started a continuous 

 decline; the catch ])er traj) dropped to 53 in 1958, 

 41 in 1959, and 7% in 1960 (Fisheries Research 

 Board of Canada, 1961). 



In Perry, Maine, on Passamaquoddy Bay, shore 

 surveys yielded 552 crabs per man-hour in August 

 1956 but only 7 per man-hour in September 1965. 

 At nearby Ltibec, where trapping was not started 

 until 1957, maximum monthly catches were 13 

 and 16 crabs per trap per day in 1957 and 1958, 

 but dropped to zero by 1960 and were still zero in 

 1965. 



Trap catches at Cummins Beach, Jonesport, 

 Maine, ranged between 235 and 500 crabs per 

 trap per day in 1953-58, dropped to 50 in both 

 1959 and 1960, and to 6 in 1965. Shore surveys 

 made in vSeptember 1965 at two locations near 

 Jonesport yielded 3 and 1 1 crabs per man-hour. 



In Trenton, Maine, at the Mount Desert Island 

 bridge, where trapping began in 1953, catches 

 dropped abruptly from a maximum of 271 crabs 

 per trap per day in 1955 to 5 and 8 in 1956 and 

 1957. Catches then dropped to zero in 1958 and 

 were still zero in 1965. A shore survey in nearby 

 Sorrento yielded 14 crabs per man-hour in 

 September 1965. 



Trap catches have fluctuated in 1953-67 at 

 Southport in central Maine and Plima Island 

 Sound in northern Massachusetts; and over shorter 

 periods in Boothbay Harbor and Kennebunkport, 

 Maine, and in Scituate and Eastham, Mass. 

 None of these fluctuations have reached points as 

 low as those given above for northeastern Maine 

 and Canada. 



Two locations in Rhode Island showed a more 

 gradual but consistent decline of crabs over 

 several years. At Narrow River in Narragansett 

 Pier maximum monthly means dropped steadily 

 from 127 crabs per traj) per day in 1956 to 51 in 

 1959. At Potter Pond Outlet in Jerusalem the 

 means dropped from 334 in 1955 to 88 in 1959. 

 The abundance in later years was not determined. 



CHANGES IN WATER TEMPERATURE 



The trend in coastal sea-water temperature 

 has changed markedly since the early 1950's 

 when tlie importance of the green crab was first 

 being realized in northern New England. I have 

 shown (Welch, 1967) that the peak of warming 

 of sm-face sea water at Boothbay Harbor, Maine, 

 since 1905 was in 1953 (annual mean, 11.1° C); 

 that the subsequent trend has been toward lower 

 temperature (1967 anniutl mean, 7.3° C.) ; and 

 that, although both summer and winter tempera- 



CHAXGES IN GREEX CRAB ABUNDANCE IN RELATION TO RECENT TEMPERATURE CHANGES 



341 



