We describe a model designed to simulate the shell carbonate budget of an oyster reef. We identify five parameters descriptive of basic characteristics of the shell carbonate budget of a reef that limit simulation accuracy. Two describe the TAZ (taphonomically-active zone) and the distribution of shell carbonate within it. One is the taphonomic rate in the TAZ. Two determine the volume contribution of shell carbonate and the taphonomic loss rate within the reef framework. For Mid-Atlantic estuaries, model simulations suggest that reef accretion only occurs if oyster abundance is near carrying capacity. Simulations further suggest that reef accretion is infeasible for any estuarine reach where dermo is a controlling influence on population dynamics. We forecast that the oyster disease dermo is a principal antagonist of reef persistence through its ability to limit shell addition. Model simulations suggest that reefs with inadequate shell addition 'protect themselves' by limiting the volumetric content of shell carbonate in the TAZ. Thus, a dominant process is the transient expansion and contraction of the shell resource, otherwise termed cultch, within the TAZ, rarely expanding enough to generate reef accretion, yet rarely contracting enough to foster erosion of the reef framework. The loss of framework carbonate thusly is curtailed during periods when the surficial shell layer deteriorates. Stasis, a reef neither accreting nor eroding, is a preferred state. Reef recession requires an inordinately unbalanced shell carbonate budget. Results strongly argue for expanded focus on the dynamics of the shell resource within the TAZ, as this likely fosters a feedback loop with abundance through recruitment, serves as the protective layer for the reef during periods of reef stasis, and establishes the threshold conditions for reef accretion and recession. Model simulations suggest that attaining maximum sustainable yield and maintaining a biomass capable of supporting sufficient shell production for reef accretion are irreconcilable goals over a large component of the oyster's range. Reef stasis would appear to be the only achievable restoration goal in Mid-Atlantic estuarine reaches where dermo holds sway. Exploitation rates much above 5% of the fishable stock per year restrict availability of surficial shell and foster reef erosion. In contrast, in the Gulf of Mexico at the high-productivity end of the oyster's range, an enhanced fishery and reef accretion may be compatible goals.

Protandric oysters generate a relatively uniform reproductive potential over a wide range of environmental conditions that impose variations in growth rate and life span. Sex-at-length keys applied to survey data show that the female fraction routinely fell between 0.4 and 0.5, regardless of location in the salinity gradient. About 70% of population biomass is female over the same salinity range. Due to the necessary local modulation of the rate of male-to-female conversion to limit the influence of varying growth and life span over the salinity gradient, the number of males always exceeds by a small amount the number of females; thus improving the likelihood of a female having neighbouring males, a necessity for an immobile broadcast spawner. However, oysters at the extremes of the estuarine gradient all yielded populations with divergent sex-ratios. One consequence of reduced generation time brought about by increased mortality from disease should be selection favouring the switch from male to female at smaller size, if disease mortality is strongly female-biased. The site with the longest record of high mortality manifests such an increase. Sites up coastal rivers, putative refuges from disease, harbour animals with the slowest male-to-female conversion rates. Arguably these animals are most similar to the ancestral oyster pre-disease. Marketed animals range from 62% to 69% female. The principal influence of the fishery, and of oyster disease, would seem to be a reduction in lifetime egg production. Dermo disease may have reduced lifetime fecundity of females by nearly a factor of four.

Female summer flounder Paralichthys dentatus grow faster than males and experience a lower natural mortality rate. Sex‐structured assessment models have been developed for other fishes with sexually dimorphic characteristics to better account for population dynamics. Although a desire exists to develop similar assessment techniques for summer flounder, some prerequisite data are not available, including the sex of fish that are landed in the recreational fishery. Furthermore, summer flounder recreational landings are constrained within harvest limits almost entirely by minimum size restrictions—a management approach that could place much of the recreational fishing mortality on females. To fill a basic but important data requirement to improve the stock assessment of this species while also providing some insight on how current management strategies might impact the sex structure of the population, we collected data on sex and length of summer flounder (n = 4,437) that were landed in the New Jersey recreational fishery in 2009 and 2010. Females dominated the recreational catch in both years (95% female overall). The proportion of landed fish at a given length that were females was greater at lower latitudes and earlier in the summer; the proportion female at length was greater in 2010 than in 2009. Extensive seasonal, annual, and spatial variability evident over such a local scale suggests a highly dynamic sex dependency in the population dynamics of summer flounder and indicates that a more robust data set covering wider geographic and temporal scales will be necessary before sex‐specific landings data can be confidently incorporated into an assessment. Received February 20, 2012; accepted August 17, 2012

Models that account for sex‐specific behavior and population dynamics are becoming more common in the stock assessment of sexually dimorphic fishes. However, such models can be data intensive and require some knowledge or assumptions about the sex ratio of fishery landings. A recent stock assessment review of Summer Flounder Paralichthys dentatus identified the need to account for sex‐specific fishing mortality in the assessment model; however, no data on the sex composition of the catch were available. Fishery‐independent, sex‐specific information for this species is collected annually by the National Marine Fisheries Service's Northeast Fisheries Science Center during their bottom trawl survey. Sex at age from the survey could be applied to the fishery landings if the probability of landing a given sex at a given age is equivalent for fish collected by the survey and those in the landings. To generate the first regionally comprehensive database on the sex ratio of Summer Flounder landings and to determine the efficacy of using survey sex‐at‐age keys to estimate the sex of landed fish, we recorded the sex composition of the commercial and recreational catches of Summer Flounder (n = 31,912) in 2010 and 2011. When (1) trawl survey length data were left‐truncated to simulate the minimum retention sizes in the fisheries and (2) age–length keys generated from fishery‐dependent data were applied to length frequency distributions from the survey to simulate the growth rates of landed fish, the sex‐at‐age pattern in the survey‐derived data closely resembled the patterns in the catch. However, statistically significant differences in sex at age remained between the catch and the survey‐derived data. We hypothesize that these differences are attributable to differences in the spatiotemporal distributions of the sexes and of the survey and fishing effort. Received March 9, 2015; accepted June 23, 2015

The presumption is that egg quality influences larval survival and that egg size influences egg quality. Thus, larger eggs should be favored by selection. Counterweighing the tendency for egg size to increase is the number of eggs that can be produced if egg size remains small. We examine how egg size and egg number counterbalance in Crassostrea oysters, resulting in an average egg size near 50 mm. Simulations imposing a diversity of ranges in larval survivorship-from little advantage for large eggs relative to small eggs to a great advantage-yield some anticipated outcomes in which genotypes generating larger eggs are favored. In other simulations, however, genotypes generating smaller eggs became increasingly common. In these cases, egg size declines, as does the likelihood of survival of individual larvae: the antithesis of expectation. Few simulations identify preferred egg sizes near the size typically observed, suggesting that, under most field conditions, a selective advantage exists for smaller or larger eggs than those typically spawned. However, the extremes in egg size are rarely advantageous. Most simulations resolve an optimal intermediate egg size. Thus, observed egg size is a balance between the chanciness of larval survival enhanced by the production of a larger number of eggs and the genetically predisposed, but environmentally modulated, individual probability of larval survival that is a function of egg size, with environment determining the optimal size. The 50-mm size observed likely represents the median outcome of a range of larval survivorship probabilities, each selecting for relatively larger or smaller eggs, imposed stochastically over multiple generations. In this scenario, each year the population is pulled toward smaller or larger egg sizes, but in the next year the impetus is independent of the previous year. Reduced generation time, by disease or fishing, modifies the extent, but not the direction of trend. Thus, environmental stochasticity retains preeminence in stabilizing a balance between the probabilities of survival modulated by egg number and by egg size. The influence of shortened generation time-by disease, for example-is unlikely to be manifest in a modification in egg size and hence egg number.