Temperature, maximum size, and the Atlantic surfclam Spisula solidissima : the sensitivity of demographics to climate warming, the perfidy of food, and a vignette on size-limited management in bivalve fisheries

A dominant theme explaining intraspecific latitudinal size gradients is the temperature–size rule which states that growth rates decline but maximum sizes increase with declining temperatures over a species’ range. Herein, the demographics of the Atlantic surfclam Spisula solidissima are evaluated relative to the temperature–size rule, followed by contemplations on the impact of climate change on its management. Analysis of latitudinal trends in size–frequency identifies the anticipated trend of increasing maximum size with decreasing temperature. A metabolic energetics model shows that variations in size accrue from the physiological impact of geographic variations in temperature modulated by variations in food supply. Lifetime fecundity declines with increasing temperature. Implications include the decline in maximum size towards the south limiting the southern stock as a larval source. As temperature increases, the more rapid early growth rate does not counterweigh the cap on size imposed by temperature. Thus, higher temperatures rob the species of reproductive potential. Management measures based on the size frequency are discussed, and specifically regulatory size limits on landings are identified as incompatible with the temperature–size rule. The contribution directly addresses the influence of climate change on the fisheries management of the Atlantic surfclam, with specific reference to size-limit regulations. This paper, more broadly, examines the influence of rising temperatures on the growth of Atlantic surfclams and, by extension, most of the Bivalvia.