Table 1.

Proxy measures of clam growth: Expectations relative to poor^* (11.5- to 11-ka) conditions and summary of results by time period

Response variable	Expectations	How evaluated	Summary of results	Expectations met?/comments
Age at death	Improved growing conditions for clams will allow clams to live longer unless harvested	Count maximum number of annuli	Age at death increases through time up until harvested midden samples; age at death of all nonharvested samples are older than specimens from 11.5 to 11 ka	Yes. Clam dies youngest in Early Holocene and in Early Historic times when envirocultural conditions are poorest
Size at death	Improved growing conditions for clams will allow clams to grow larger unless harvested	Measure maximum growth-axis length	Size at death from all nonharvested samples larger than specimens from 11.5 to 11 ka	Yes. Clams are smallest in the Early Holocene and in Early Historic times, paralleling trends in age at death
Modeled maximum size	Healthier clams will be larger	Estimate Linf	Linf indicates increase in size from the Early Holocene to before Early Historic times. Most clams from middens and clam gardens are on average the same size as clams from unwalled beaches 4.2 to 2.9 ka; however, the largest clams in the Holocene are from the midden contexts. By the Early Historic, clams have a smaller maximum size. Linf of 11.5- to 11-ka specimens is smaller than all time periods, except 10 to 9.5 ka and living	Yes. Clams are smallest in the Early Holocene and in Early Historic and modern times. Linf indicates that midden samples from clam gardens are the same size or larger than nonmidden 4.2- to 2.9-ka clams, suggesting that the theoretical maximum size of clams in clam gardens is the same or larger than the “naturally” biggest clams in the Holocene; this, in turn, demonstrates the benefits of traditional clam management
Size at young age	Clams will be bigger in better growing conditions	Measure sizes (growth-axis length) at ages 1–5	At ages 1 and 2, Early Historic clams are bigger than all others, but this evens out by age 3. By age 3, clams from all time periods, except living, are larger than those from 11.5 to 11 ka; by ages 4 and 5, clams from all time periods are larger than those 11.5 to 11 ka	Somewhat. While 11.5- to 11-ka clams are smaller than all other time periods, reflecting that period’s relatively poorer growing conditions, the Early Historic and modern clams are not distinguishable from this early period

^*Poor conditions are those where abiotic factors (grain size, water temperature, slope) are outside the preferred range for butter clams and where there has been no human management. These conditions characterize the temporal category from 11.5 to 11 ka.