collections were made during the ebb tide just be- 

 fore low water. Observations with a face jDlate in- 

 dicated that during the ebb tide green crabs were 

 actively moving from the intertidal zone into the 

 channels. The crabs taken at nearly low tide had 

 had an opportunity to feed in the intertidal zone 

 during a complete tide before capture. The sam- 

 ple size was arbitrarily limited to about 50 crabs 

 or eight drags. Occasionally more than .50 crabs 

 were caught; all were retained for stomach 

 analj'sis. 



Tables of data on the stomach contents of the 

 green crabs caught during this study are available 

 in the U.S. Fish and Wildlife Service Data Report 

 29, which can be obtained from the Branch of Re- 

 ports, Bureau of Commercial Fisheries, U.S. De- 

 partment of the Interior, Washington, D.C. 202'±0. 

 The tables and figures in the text are derived 

 from these data. 



Each crab stomach was removed at the labora- 

 t-ory and placed in a vial containing Formalin. = A 

 record of the sex, molting stage, and carapace 

 width, as well as the presence of eggs on female 

 crabs, was included in each vial. Later each stom- 

 ach was opened, the contents were flushed with 

 water into a dish, and the food items were sepa- 



- Trade names referred to in this publication do not imply 

 endorsement of commercial products. 



rated and identified under a dissecting microscope. 

 The occuiTence and, whenever possible, a count of 

 each food item were recorded. For each collection 

 of crabs, the total of these data and the number of 

 stomachs containing food were used to obtain the 

 jjercentage frequency of occurrence and average 

 number of each food item per crab. 



Estimates of the amount of food in the stomachs 

 were separated into three categories : ( 1) stomachs 

 containing tissues and hard jjarts of foods, (2) 

 stomachs nearly empty, containing only hard parts 

 of foods, and (3) stomachs with no food. The stom- 

 achs in the first category are tabulated here as a 

 percentage of all crabs caught jjer collection, and 

 those in the second category as a percentage of tJie 

 stomachs containing food. Empty stomachs are 

 omitted from all calculations. 



Most food consisted of crushed or fragmented 

 remains; so, I used various hard structures to 

 identify the food organisms. Assigning a food to 

 a definite species category was not always possible, 

 but often enough of the food remained so that I 

 could assign it to a general taxonomic group. As 

 a consequence, not all major taxonomic groups are 

 the sum of the specific items. Mollusk shells were 

 the most readily identified food items (fig. 2). In 

 particular, species of pelecypods could be recog- 

 nized because their hinge structures usually were 







Figure 2. — Mollusk foods from the stomachs of green crabs: a. Mytilux cdiilis, and b. Gemma i/cdidui and Hydrohia 



tniniita (1-mm. scale near lower edge of figure). 



186 



U.S. FISH AND WILDLIFE SERVICE 



