There are two Atlantic surfclam subspecies. The northern subspecies (Spisula solidissima solidissima) supports the federal fishery and is abundant on the continental shelf north of Cape Hatteras. The southern subspecies (S. s. similis) is predominantly found south of Cape Hatteras, but is also found in shallow, patchy, northern areas, such as coastal Virginia, Long Island Sound, and southern Massachusetts. However, the taxonomic rankings of these clams remain controversial. Recent genetic evidence suggests they could be distinct, but closely related species. Given the surfclam’s vulnerability to climate change and its economic importance to commercial fishing and aquaculture industries, the uncertainty around its taxonomic classification must be resolved. The goal of this project was to determine whether the surfclam subspecies have the ability to hybridize. Surfclams were collected from commercial fishing grounds off New Jersey (S. s. solidissima) and from a known S. s. similis bed in Massachusetts. Breeding occurred in October 2023 and May/June 2024 and resulted in several cohorts of purebred and hybrid progeny. Genetic samples were collected from each of the parental and offspring groups to confirm genetic lineage. Fertilization rate across groups ranged from 95-100%. Larvae were reared in 60 L static cultures maintained at 17-22˚C and a salinity of 29-32. Shell length, shell height, and survival were assessed two to three times weekly during water changes. Growth of the hybrid larvae appeared most similar to the purebred larvae with which they shared maternal parentage. Larvae from all four groups metamorphosed, with most reaching competency at approximately 21±5 days post fertilization. A controlled study of juvenile growth in a flow-through seawater system (18-24˚C, salinity 27-31) showed that hybrid surfclams (S. s. similis female x. S. s. solidissima male) exhibited significantly greater growth rates than either purebred group. This work demonstrates that S. s. solidissima and S. s. similis are indeed capable of hybridizing. Future work will include evaluating whether any physiological and thermal tolerance differences exist among the groups and determining whether hybrid clams can generate gametes, backcross with purebreds, and produce F2 hybrids.