Results from the clam ecology study at Cranberry Cove, town of Beals were as follows:
High Tide (No Netting): Survival = 22.2% Growth = 8.5 millimeters, which is about 3/10ths of an inch
High Tide (With Netting): Survival = 83.3% Growth = 11.4 millimeters, which is about 4/10ths of an inch
Mid Tide (No Netting): Survival = 18.1% Growth = 7.9 millimeters, which is about 3/10ths of an inch
Mid Tide (With Netting): Survival = 83.3% Growth = 10.7 millimeters, which is about 4/10ths of an inch
Low Tide (No Netting): Survival = 19.4 % Growth = 12.8 millimeters, which is about 1/2 of an inch
Low Tide (With Netting): Survival = 80.6% Growth = 16.5 millimeters, which is about 6/10ths of an inch.
No surprise in these results! As expected, clam survival was very low (less than 25%) in all of the unprotected pots. The netted plots, however, averaged 82.4%. Predation by green crabs was the primary source of clam mortality at Cranberry Cove. These results show how important it is to use protective netting to help clams survive.
The growth results also were not surprising. Growth rate at the mid and upper tide levels was very similar, averaging about 9.6 mm of new growth between May and September. Growth was significantly faster for clams planted at the lowest tidal level in this study. While growth was slightly faster in protected pots, clams averaged over a half-inch in new growth (14.7 mm) during the experiment. This is an excellent example of how clam growth is related to tidal position. Clams grow faster at the extreme low tide mark because they are able to feed longer each tidal cycle as that is the area where water covers the flats longer each day. Clams only feed when the tide covers them, so animals living near the high water mark are stunted and sometimes may never reach 2-inches (legal size).