Date of Award
© 2021 Daniel F. Delago
Professional Science Master's (PSM) In Ocean Food Systems
Adam St. Gelais
The eastern oyster (Crassostrea virginica) supports the ecological function of estuarine ecosystems by creating biogenic reef habitat (Purchon, 2013), and positively influencing coastal biogeochemistry in intertidal, and subtidal environments (Humphries et al., 2016; Ray and Fulweiler, 2020). As anthropogenic impacts continue to influence the health of marine environments globally (Halpern et al., 2008), oyster reef restoration is gaining increased attention as a means of maintaining the function of estuarine systems (Beck et al, 2011). Shellfish aquaculture has gained increased attention, contributing 21% of all aquaculture production globally (FAO 2020). Shellfish aquaculture provides a suite of social-ecological benefits while contributing to provisioning and supporting ecosystem services including nutrient removal, water clarification, coastal protection, and habitat creation (Gentry et al. 2020; Grizzle et al. 2008; Dame and Kenneth, 2011; Kellogg et al. 2014). In this way, shellfish aquaculture can exist in synergy with ecosystem processes, resulting in positive environmental outcomes while creating livelihoods through supply of seafood and commercial products (referred to as restorative aquaculture) (Blanchard et al., 2017). Despite the range of ecosystem services provided from bivalve aquaculture, the role of larval subsidy in population restoration has yet to be recognized (van der Schatte Olivier et al., 2020). However, evidence of green lipped mussel (P. canaliculus) restoration via larval subsidy has been documented (Norrie et al., 2020). Habitat suitability index (HSI) models have proven effective in facilitating population restoration of the American oyster in estuaries of the eastern United States by providing spatially explicit information regarding the quality of habitat over broad areas of interest (Soniat and Brody, 1988; Barnes et al., 2007; Starke et al., 2011; Pollack et al., 2012; Linhoss et al., 2016; Theuerkauf and Lipcius, 2016; Puckett et al., 2018). This study employs a geospatial HSI model for the eastern oyster to investigate a recent population resurgence in an estuary where oysters were once extirpated, the Damariscotta River estuary (DRE), Maine, USA. As a means of internal validation, we combine HSI model predictions with local ecological knowledge gained through participatory interviews and surveys of local shellfish harvesters targeting eastern oysters, oyster aquaculture producers operating within the estuary, and researchers familiar with the system. By assessing the viability of incidental restoration resulting from larval subsidy from oyster aquaculture, this study explores the implications of low-cost restoration strategies which integrate fisheries, aquaculture, and conservation interests within a reciprocal conservation paradigm.
Delago, Daniel F. 2021. Investigating larval spillover from oyster aquaculture through geospatial Habitat Suitability Index modeling: A Damariscotta River estuary case study. Graduate Program in Ocean Foods Systems, University of New England, Maine, USA.