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The Florida bay scallop (Argopeclen irradiuns concentricus Say, 1822) is a relatively short-lived species that resides in dynamic marine systems and is subject to multiple stressors, although the environmental drivers of bay scallop abundance along the Florida Gulf Coast are not well understood. The use of an ecosystem approach to fisheries management may be particularly relevant for short-lived species that are highly susceptible to environmental changes, but this approach requires an understanding of how environmental variables, such as salinity and temperature, may influence bay scallops throughout their range. This study was designed to identify the relationships between environmental variables and bay scallop abundance and to evaluate the relative effect of these relationships. Scallop surveys conducted in the spring and fall along the Florida Gulf Coast from 1992 to 2019 were compared with seasonal water quality parameters, streamfiow discharge, precipitation, wind speed, and climate indices. The size and spawning success of the fall scallop population were negatively affected by relatively high Karenia brevis counts, low dissolved oxygen, and low phosphorus availability. During the period of early postsettlement growth in the winter, scallops were negatively impacted by salinities outside the range of 22-27 due to increased rainfall and low nitrogen availability. Finally, the factors that negatively affected juvenile scallop growth and survival in the spring included increased rainfall and wind speed resulting in relatively high turbidity and comparatively low chlorophyll a. KEY WORDS: Argopecten irradians, abundance, Florida, Karenia brevis, salinity, GAMLSS, INTRODUCTION The Florida bay scallop (Argopecten irradians concentricus Say, 1822) is a relatively short-lived species with a lifespan of approximately 12-18 mo (Barber & Blake 1981). Bay scallop spawning typically [...]

Bay scallops (Argopecten irradiuns conemtricus Say. 1822) exhibit a strong association with seagrass habitat from the time of larval settlement, but alternative habitats, such as macroalgae species, may also serve as important habitats for this species. The association of Florida bay scallops with the percent cover of observed seagrass, macroalgal species, and several substrate types (e.g., mud, shell, and rocks) was examined to determine whether a variety of seagrass and macroalgal species significantly influences the abundance of bay scallops in Florida. Sampling occurred at eight study sites along the Gulf coast of Florida, from Tampa Bay in the south to St. Andrew Bay in the north. SCUBA divers used a point-intercept approach along a transect to assess habitat type and percent cover, in addition to recording bay scallop abundance. Generalized additive models for location, scale, and shape were used to model bay scallop abundance as a function of habitat type. Across all sites, bay scallop abundance was positively correlated with percent cover of seagrass and negatively correlated with bare substrate, such as mud and sand. Five out of the 13 habitat types observed in association with bay scallops in this study were significant factors in models of bay scallop abundance including Acetabularia spp. (J.V. Lamouroux. 1812), Cmderpa spp. (J.V. Lamouroux, 1809), Gracilaria spp. (Greville, 1830), Syringadium filiforme (Kiitz, 1860), and Thalassia testudinum (Koenig. 1805). The two most important habitat variables were T. testudinum and Gracilaria spp., and there was an observed threshold response of bay scallop abundance to these habitat variables at low to medium percent cover. This is the first study to identify the importance of both seagrass and several macroalgal species for Florida bay scallops and suggests that bay scallop restoration efforts may benefit from restoring seagrass and macroalgae. KEY WORDS: Argopecten irradians concentricus, bay scallop, Florida, habitat, macroalgae, Thalassia. seagrass, GAMLSS, INTRODUCTION Bay scallops (Argopecten irradians Say. 1822) are found in coastal, benthic habitats ranging from Cape Cod, Massachusetts to Laguna Madre, Texas (Fay et al. 1983). Commercial bay scallop fisheries [...]