Using reproductive potential to assess oyster population sustainability

Abstract

Ensuring that oysters remain sustainable in the face of significant coastal restoration activities, high local subsidence rates, and predicted sea-level rise requires a deeper understanding of basic population demographics, including reproductive potential. We quantified fecundity (eggs ind −1) of oysters at high-and low-salinity sites during a fall and spring spawn season. We assessed the relationships between oyster size, the relative proportion of females across size classes, and fecundity. Finally, we quantified reproductive potential (eggs m −2) of an engineered reef by connecting fecundity with annual oyster population demographic data as a means to assess population sustainability. The proportion of females generally increased with shell height, achieving a population with >50% females in Biloxi oysters >75 mm, and Grand Isle oysters >100 mm. Fecundity across both sites and seasons ranged from approximately 2,000 to >55 million eggs oyster −1. Mean fecundity generally increased with shell height, varying significantly by site, with Grand Isle (high salinity) oysters having greater fecundity than Biloxi (low salinity) oysters. Fecundity did not differ by season. Mean reproductive potential (eggs m −2) was driven by density and size distribution. Reefs with high densities and higher counts of market-sized oysters had reproductive potentials 5× greater than those with low densities and low counts of juvenile oysters. With increasing changes in water quality from coastal management and climate, impacts on oyster reproduction may critically impact population sustainability. Reproductive potential provides critical data to assess individual reef ecosystem services, and to assess the potential for maintenance of local metapopulations.

Context‐dependent carryover effects of hypoxia and warming in a coastal ecosystem engineer

“…If carryover effects are operating in these field-raised populations, growth deficits associated with early life exposure and re-exposure to multiple stressors may ultimately reduce oyster size and limit their economic value since oysters with similar shell sizes would contain less meat (tissue). Moreover, because oyster fecundity is correlated with size (Marshall et al 2020), carryover effects of stress may affect wild oyster population size or hatchery production, while also affecting oysters' ability to provide key ecosystem services such as denitrification (Kellogg et al 2014). Finally, oysters are protandrous hermaphrodites (larger individuals are female Thompson et al 1996), so these size effects may impact oyster sex ratios in the field, further influencing population dynamics.…”

Oyster reefs' control of carbonate chemistry—Implications for oyster reef restoration in estuaries subject to coastal ocean acidification

“…Given that the reefs we monitored are young subtidal constructed reefs, their rapid growth was not constrained by sea level, contrasting with mature, natural/restored reefs that are typically limited in vertical growth (Waldbusser et al, 2013). In this regard, this study reflected impacts of young reefs; oysters grow according to a von Bertalanffy growth function in which growth declines with age (Rothschild et al, 1994; von Bertalanffy, 1938), thus older reefs that contain larger, slower growing oysters and/or have reached their vertical growth maxima may exert less biogeochemical influence on the water column as energy is increasingly allocated for reproduction (Marshall et al, 2020) and calcification rates decline. Moreover, all environmental observations occurred over summer months when the rates of community calcification and respiration would be the largest, and the reefs were located in a shallow region (2 m) with a small tidal range (1 m), collectively maximizing the reefs' potential impacts on the carbonate chemistry that were captured in our study.…”

Oyster model inventory: Identifying critical data and modeling approaches to support restoration of oyster reefs in coastal U.S. Gulf of Mexico waters

“…Similarly, predation is another cause of mortality at higher salinities as oyster predators generally increase in abundance and biomass with salinity, and lower salinities limit their distribution (Wells, 1961). For example, the oyster drill (Stramonita haemastoma) and the stone crab (Menippe mercenaria) are restricted to salinities above 12-15 (Menzel and others, 1958;Garton and Stickle, 1980;MacKenzie, 1981) where they are capable of decimating local oyster populations, particularly the smaller size classes (that is, shell height < 50 millimeters).…”