Oyster reefs are a primary source of calcium carbonate in most estuaries and the habitat complexity provided by these reefs supports a diversity of estuarine life. The available surface area of hard substrate on an oyster reef is critical for population maintenance, as this substrate provides habitat for the settlement of new oyster recruits. On natural reefs, the primary substrates available for settlement by spat include live oysters, boxes (dead articulated valves), and cultch (single oyster shells and shell fragments). Data from a long-term oyster monitoring program from February 2016 to October 2020 were used to generate a monthly time series of the percent of total carbonate weight contributed by live oysters, boxes, and cultch at four reefs in the Mississippi Sound. These percentages vary spatially and temporally. When reefs were healthy, live oysters dominated the total carbonate. During the study period, two mass mortality events occurred. Following the 2016 mortality event, the substrate contributing the majority of the carbonate shifted from live oysters to cultch at all reefs sampled. Three reefs exhibited a modest population recovery following the mortality event only to be impacted by a second, more severe mass mortality event in 2019. Boxes usually had the highest number of spat per gram carbonate at all reefs. The potential surface area (PSA) of each substrate type was calculated by comparing the available surface area of each substrate type and the number of spat that settled on each substrate. Correction factors were generated to account for larval settlement preferences and used to either debit or credit the PSA to calculate effective surface areas (ESA) for each substrate type. Cultch offered the highest ESA at Pass Christian, and cultch ESA was higher than box ESA at Henderson Point and Between Bridges reefs. At Bay St. Louis, box ESA was twice that of cultch. These results suggest cultch and boxes are more valuable settlement substrates than live oysters in this region under the conditions present during the survey time frame, which was characterized by low oyster abundance and aperiodic mass mortality. The unbalanced ESA, in which live oyster ESA is underrepresented, represents an unhealthy condition and demonstrates that a critical period exists for reef recovery after mass mortality in which the timely coincidence of increased box ESA and larval availability is essential for rapid recovery from mass mortality.

Florida is one of the largest exporters of aquarium ornamental species in the world, but trade is expanding to include harvest of herbivorous invertebrates that play important ecological roles in nature, such as grazing algae from seagrass and corals. Here, stable isotope sclerochronology is used to document life history traits of two of the most intensely harvested herbivorous gastropod species in Florida, the turbinids Lithopoma americanum and Turbo castanea. Such information is critical to assessing whether current harvest intensities are sustainable. Populations of L. americanum and T. castanea in Florida consist of rapidly maturing individuals that reach maximum sizes within 2 y and 1 y, respectively. Rapid maturation should allow these populations to recover rapidly from intense harvest, but short-lived species are also intrinsically susceptible to population collapse from recruitment failure, complicating effective management of the fishery. In addition, the short lifespans of these turbinids suggest that hobbyists may purchase replacement animals frequently, increasing fisheries pressure on natural ecosystems.

Accurate distribution and density data of endangered marine species may be complicated by artifacts from exploitation, survey design, and general difficulty in accessing subtidal habitats. Occasional review of survey data may help restructure survey efforts to improve conservation outcomes. The white abalone (Haliotis sorenseni) is a marine gastropod listed under the Endangered Species Act thought to primarily inhabit depths beyond conventional scientific SCUBA limits (30–60 m) in the southern California Channel Islands. This study reviews surveys at four Channel Islands and four locations along the southern California mainland coast within SCUBA depth ranges and conducts a simulation comparison of the larger survey design used for this study with the standard transect approach presently common in the region. White abalone density was greater along the mainland, particularly in Point Loma and La Jolla, than the Channel Islands, where no live white abalone were recorded. The larger survey approach was found to be more effective at finding simulated white abalone, beyond the expected difference in areal coverage alone. These results show that surveys within SCUBA limits are an effective way to monitor H. sorenseni and that impacts from overfishing on the Channel Islands may make sections of the mainland coast one of the last refuges of white abalone. The greater efficiency of larger surveys can complement standard transect approaches to improve abalone monitoring at sites of interest. Both results can be applied to the immediate conservation of white abalone by improving site selection and monitoring approaches to active restoration efforts.

Predation by crustaceans and echinoderms is a significant driver of mortality for sessile invertebrates in near-shore marine ecosystems. As a response, shellfish growers use predator exclusion cages to grow their product. Oysters grown in these cages and clams in and under nets have been observed to exhibit thinner, brittle shells, which is not optimal for market, nor for those being grown for restoration purposes. Here, the nonconsumptive predator effects of several native and nonnative predators on shell morphology of Crassostrea virginica oyster spat. Juvenile (1–3 mm) seed oysters were exposed separately to chemical cues of five different predators and one nonpredator crab were investigated and compared with control (no exposure) spat. Significant effects of predator presence on the total wet weight (g) of the spat was demonstrated, with the highest increase for spat exposed to black-fingered mud crabs (Panopeus, 1.70 mg d–1) and the biggest decreases for spat exposed to the European green crabs (Carcinus maenas—1.34 mg d–1) and the sea stars (Asterias rubens—1.47 mg d–1). Changes to oyster length (mm) and shell density (crushing resistance) were not significant. Implications for aquaculturists and wild bivalve populations are that growth could be negatively affected by the lack of predators on these important organisms.

The Atlantic surfclam (Spisula solidissima) is an important commercial fishery resource on the U.S. MidAtlantic continental shelf. Although the 2016 stock assessment found that surfclams are neither overfished nor is overfishing occurring, uncertainty in the scale of spawning stock biomass persists. As a consequence of this uncertainty, the MidAtlantic Fishery Management Council (MAFMC) lowered the acceptable biological catch in 2016. A simulation analysis was developed for Atlantic surfclam to estimate the overfishing risk associated with the catch recommendation and its adherence to the MAFMC risk policy. Operating models conditioned on the 2016 stock assessment model structure generated simulations of the surfclam population, with alternative models to represent uncertainty in steepness (h) of the stock-recruitment curve and natural mortality

Crustacean female sex hormone (CFSH) plays a pivotal role in developing adult-specific female characteristics, specifically the mating and parental care system of the female blue crab, Callinectes sapidus, manifested after the puberty-terminal molt. Therefore, this study aimed to determine if there is a relationship between CFSH and the development of phenotypes specific to the female C. sapidus during its life cycle and if the continued presence of CFSH is required for developing adult-specific features during the prepuberty molt cycle. First, CasCFSH transcripts in females steadily increase, starting from crab stages 3-4 to prepuberty, except for a decrease at crab stages 15-16. The prepuberty females have the highest CasCFSH transcripts, with ∼5.6-fold higher than adults. CFSH protein levels at prepuberty are the highest but similar to adults. The first and visible secondary female characteristics include a pair of gonopores or a triangular abdomen and four pairs of pleopods seen as early as crab stages at ∼3 (carapace width, CW, 5-7 mm) - 5 (CW 8-10 mm), respectively. The adult-specific female morphological features that are developed gradually throughout the prepuberty molt cycle are manifested only after the puberty-terminal molt. A CasCFSH knockdown study by injecting CasCFSH-dsRNA into prepuberty females at specific molt stages provides further evidence: the continued presence of CasCFSH is required for gradually developing adult-specific morphological features during the prepuberty molt cycle. Overall, the abdomen size is first determined at the intermolt stage. Then, the abdominal shape, gonopores, sternal tubercles, spermathecae, and ovigerous setae and hairs are formed at the intermolt and early premolt stages. Finally, the plumose hairs are developed during intermolt, early, and late premolt stages.

In general, pearl cultivation has advanced with organisms produced and improved in hatchery; however, wild spat collection is still the primary source for commercial cultivation. In Mexico, progress toward pearl oyster hatchery spat production is yet in the experimental stage. The only three farms established in the country (Guaymas, La Paz, and Cozumel Island) rely on extensive culture. Constant spat supply is imperative to ensure a successful operation; at La Paz Bay, however, larval uptake of the pearl oyster Pinctada mazatlanica in artificial collectors has always been low. This study aimed to assess spatio-temporal and bathymetric patterns of spat distribution across the area to locate suitable sites to install spat collecting stations. Our results showed significant differences (P < 0.05) between stations. Mogote, Caimancito, Punta Colorada, and Gaviota Island were the stations with the highest spat abundance at 1-m depth in July–September after 40 and 60 days of immersion. The data were also analyzed with generalized linear models. The best models, selected with the Akaike and Bayesian criteria, suggest that 1-m depth, 40- and 60-day immersion time, and site (particularly, Caimancito Beach, Punta Colorada, and Gaviota Island) contributed significantly to explaining the highest catches (mean: 5–8 organisms/collector) of P. mazatlanica spat in La Paz Bay. Therefore, the area within these sites should be considered suitable for installing the network of artificial collectors during the season of high spat abundance.

Crustaceans of the family Gonodactylidae (Order Stomatopoda) are potential predators of cultured pearl oysters in ocean-culture systems, yet they have not previously been implicated in contributing to on-farm mortality of culture stock. Improved knowledge of the threat posed by stomatopods to pearl oyster survival in ocean-culture systems, as well as possible influencing factors, is necessary to determine whether stomatopod predation merits concern and for prioritizing efforts to prevent and control predator incursions. The aims of this study were, therefore, to determine if the presence of stomatopods within culture units significantly affects cultured pearl oyster survival in an ocean-culture system, and whether predator or prey size exert influencing effects. Mortality of Akoya pearl oysters (Pinctada fucata) over a 6-wk culture period ranged from zero to 33.3% among individual culture units containing a single stomatopod (Gonodactylaceus falcatus) at the study site in north Queensland, Australia. An interaction between stomatopod size and their time at liberty within culture units, as well as an interaction between stomatopod size and pearl oyster size, explained 84.1% of the variance in pearl oyster survival among culture units. Most prominently, small stomatopods (total length: 37.0 ± 0.9 mm) caused minimal mortality of culture stock (4.6% ± 1.1%), whereas large stomatopods (total length: 69.0 ± 1.1 mm) had a significantly greater impact (20.8% ± 2.1% mortality) over the 6-wk period (P < 0.05). Given the potential for a single G. falcatus to cause up to 33.3% mortality of culture stock within a culture unit, the threat from stomatopod predation during ocean culture of pearl oysters could be significant and collection of site-specific information to assess this threat is recommended.

Freshwater clams, better known as pokea clams in Indonesia, are among the important economy-generating resources whose population continues to decline in line with the increase in fishing activities. The present study aims to determine the age group, growth, mortality, and exploitation rate of pokea clams. This research was conducted in the estuary segment of Laeya River, Southeast Sulawesi, Indonesia, from March 2016 to February 2017. Pokea samples were taken using a traditional fishing tool called Tangge. Data on age groups, growth, mortality (natural, fishing, and total) and exploitation rate were processed using the Bhattacharya method, the von Bertalanffy inverse function, the width converted catch curve, and Pauly's empirical formula, respectively, accommodated in the FiSAT II program version 3.0. The results showed that the male and female pokea were spread out in 1 and 2 size groups. Male pokea was dominated by 2 size groups, whereas the female pokea was dominated by 1 size group. The growth of the male and female clams followed the equations Lt = 83.89 – (83.89–0.025)e–0.54t and Lt = 77.38 – (77.38–0.025)e–0.52t. The male natural mortality (M), fishing mortality (F), and total mortality (Z) were 2.04 y–1, 0.91 y–1, and 2.94 y–1, respectively, whereas the natural mortality, fishing mortality, and total mortality of the female clams were 1.51 y–1, 0.90 y–1, and 2.41 y–1, respectively. In general, the male and female pokea clams in the Laeya River are overexploited, with the exploitation rates of 0.69 and 0.63, respectively.

Oyster population demographics are used to estimate shell standing stock (g m–2) and rates of shell production (g m–2y–1) and loss by oyster, Crassostrea virginica, populations in both the Virginia and Maryland portions of the Chesapeake Bay. Source data are from long-term stock assessments whose footprints cover the majority of extant fished reefs in Virginia and a mix of fished and sanctuary reefs in Maryland. Individual longevity in extant fished populations is typically less than or equal to 5 y and truncated when compared with fossil C. virginica populations. Shell standing stock and productivity are maximal in year 1 or 2 of the progression of a year class through the population. Maintenance of the underlying reefs structure is dependent on regular shell input from mortality. The combination of truncated population structure and variable recruitment make shell addition temporally unstable. High turnover rates (≥30% y–1) of the shell substrate pool in the oxic region above the sediment water interface are present. Reef accretion rates are generally less than the combination of sedimentation and relative sea level rise in most of the Bay system. Greater individual oyster longevity is required to ensure development of self-sustaining reef structures in the Chesapeake Bay.