The fan mussel Pinna nobilis is threatened by several anthropogenic disturbances that are only partially mitigated by current conservation measures. In the Faro Lake Natural Reserve, the fan mussel population suffers from insufficient recruitment while, due to periodic dredging, a high larval supply within the canals does not support a stable population. In the present study, a robust number of fan mussel specimens were transplanted from a high-impact site to a guarded area to test the effects of transplantation on future conservation efforts. Over a 12-mo period, high survival and elevated growth were observed in the test population in comparison with the local population, demonstrating transplantation as a feasible and efficient method to prevent P. nobilis population decline. Such small-scale experiments provide useful indications for better management approaches for both of the threatened species and the natural hosting environment.

Mussels play an important supplementary role in the diet of coastal communities in many parts of the world. Over the last three decades, exploitation pressure on the intertidal brown mussel Perna perna on the southeast coast of South Africa has become unsustainable, eliminating mussels from substantial areas of suitable habitat and creating the need to rehabilitate denuded shores. The effect of mussel size on the effectiveness of the rehabilitation technique was tested, hypothesizing that mussel size may influence the effectiveness of rehabilitation due to size-dependent energy allocation (e.g., growth versus reproduction). Immature, small (1–2 cm), and sexually mature larger mussels (3–4 cm) were deployed at four sites, separated by distances of about 100 m, and sampled after 2, 4, and 6 mo. It was found that there were no significant differences between the two size classes in survival rates, which were always high (∽60–80%). There were frequent size effects on the other variables measured, but these tended to depend on the criteria used. Small mussels showed significantly greater growth in terms of shell length, increase in weight, and percentage increase in dry weight. Similarly, small mussels had weaker byssal attachment strength than large mussels, but higher tenacity when attachment strength was normalized to shell area. Small mussels also generally had higher condition indices than large mussels. This was probably related to spawning by adults and the difference was not always significant. For large mussels, maintenance, including byssal thread production to resist dislodgement, seemed to have higher priority than shell growth and condition. The absence of significant differences in tenacity between size classes would explain their similar survival rates. No difference was found between size classes in the numbers of new recruits appearing in experimental patches. Deciding which size class is better for rehabilitation depends on the criterion used. Overall, it was found that ontogenetic reallocation of energy reserves affected neither biomass increase nor survival, probably the most meaningful definitions of success. Given their greater availability and efficiency at increasing biomass, it is suggested that on balance small mussels are likely to be more effective in restoring mussel populations.

Modifications in shell structure, mantle, and adductor muscle are considered derived adaptations that allowed scallops to swim. This suggests that morphological properties of the adductor muscle and shell should relate to swimming performance in scallops. Various morphological characteristics of the shell (mass, aspect ratio, and volume between the valves) and the adductor muscle (size, position, and attachment to the shell) were measured in six scallop species (Amusium balloti, Placopecten magellanicus, Equichlamys bifrons, Pecten fumatus, Mimachlamys asperrima, and Crassadoma gigantea) with distinct swimming strategies, as documented by measurements of muscle use during induced escape responses. Morphological characteristics of the shell and adductor muscle differed markedly between the species, but did not always follow their swimming strategies. Principal components analysis revealed that shell width, shell and muscle masses, and associated morphological attributes were closely linked with swimming endurance. The intensity of the escape response was best predicted by the aspect ratio and the obliqueness of the adductor muscle.

A genetic linkage map of the blood clam (Tegillarca granosa) was constructed based on simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers. An F₁ family consisting of 109 individuals was created using the “two-way pseudo-testcross” mapping strategy. A total of 568 polymorphic markers, including 32 SSRs and 534 AFLPs, were used in the linkage mapping. The female linkage map consisted of 250 marker loci (15 SSR and 255 AFLP), which formed 18 linkage groups with an average marker space of 7.15 cM; they spanned a total length of 1,649.33 cM, covering 84.49% of the estimated genome size. The male map consisted of 290 marker loci (14 SSR and 276 AFLP), which mapped to 22 linkage groups with an average marker spacing of 5.56 cM. They spanned a total length of 1,485.09 cM, covering 84.43% of the estimated genome size. This map is the first genetic linkage map in the blood clam and provides a basis for mapping quantitative trait loci and for breeding applications.

Ocean quahogs [Arctica islandica (Linnaeus, 1769)] are the longest-lived, noncolonial animal known today, with a maximum life span exceeding 500 y. Ocean quahogs are a commercially important bivalve, inhabiting the continental shelf of the North Atlantic Basin. Although considerable information exists on the growth and physiology of A. islandica, limited information is available regarding recruitment; accordingly, sustainably managing the fishery is a challenge. To investigate long-term recruitment trends, the age of ocean quahogs from Georges Bank which were fully recruited to the commercial fishery (>80 mm shell length) was determined by analysis of annual growth lines in the hinge plate. Ages of animals representing the fully recruited size range were used to develop an age—length key, enabling reconstruction of the population age frequency. The population age frequency showed that the Georges Bank population experienced an increase in recruitment beginning in the late 1890s. Initial settlement, documented by a few ocean quahogs that were much older, occurred much earlier, in the early 1800s. Following the late 1890s increase in recruitment, the population expanded rapidly reaching carrying capacity in 20–30 y. Recruitment was more or less continuous after this expansion, consistent with maintenance of a population at carrying capacity. Unusually large year classes were not observed, nor were significant periods of high recruitment interspersed with periods of low recruitment. The relationship of growth rate with age for the oldest clams was assessed using the time series of yearly growth increments and the resulting relationship fitted to three models (von Bertalanffy, Gompertz, and Tanaka's ALOG curve). The ALOG model was clearly superior because it allows for persistent indeterminate growth at old age, rather than the asymptotic behavior of the other two and because it allows for a rapid change in growth rate at what is presumed to be maturity.

In Florida, culture of the sunray venus Macrocallista nimbosa is currently limited by seed supply. Hatcheries have not been able to condition and spawn brood stock on a predictable and consistent basis. The objective of this study was to determine the relative effects that temperature and diet have on the natural gametogenic cycle of this species so that improved conditioning protocols can be established for this species. The sunray venus M. nimbosa from west central Florida (Anna Maria Island) reached sexual maturity at a shell length >35 mm (age 6–8 mo). Small clams (mean shell length: 60 mm) had a 1:1 sex ratio, whereas larger clams (mean shell length: 129 mm) were predominantly female. This species exhibited a poorly defined annual reproductive cycle, and development was not synchronous between the sexes. Males developed mostly over the cooler months and spawned in the spring and early summer. Females exhibited two periods of relatively greater development: June to October and December to February, with relative little development occurring in November and from March to May. Nonetheless, mature individuals of both sexes were found throughout the year. All of these suggest that spawning within this population is almost continuous and that as females develop mature ova, they are released sporadically and fertilized by male clams, and a new generation of oocytes is rapidly produced. Given the large time over which gametes are produced, temperature does not seem to be critical. Instead, it is likely that M. nimbosa responds to fluctuations in food supply by rapidly developing gametes, spawning, and redeveloping. Future conditioning attempts should therefore focus on diet quality and quantity.

The cardid bivalve Acanthocardia tuberculata is harvested in southern Spain and on the Atlantic coast of Morocco for the Spanish canning industry. The reproductive cycle and population structure of this species were studied in southern Spain from June 1999 to May 2000, using histology and condition indices, as well as modal size classes in length-frequency distribution analysis. The samples were collected monthly during autumn and winter months and fortnightly during spring and summer months. A total of 4,047 specimens were examined, from which 3,539 specimens were processed for biomass analyses and 508 for the study of the gametogenic cycle. Shell lengths of individuals ranged from 6 to 76 mm (48.15 ± 15.15 mm, mean ± SD), and the sex ratio was 1:1. The reproductive cycle of A. tuberculata showed an annual pattern, with an extended sexual activity from January to July, during which successive spawning events were observed, and with a clear-cut resting period from September to November. Small-size individuals are recruited into the population from June to December. No correlations were found between the environmental variables (sea water temperature and concentration of chlorophyll a) and the condition indices, which could be explained by the presence of upwellings in the area that introduce random fluctuations of these environmental variables. To improve management of the wild stock, a closed season during June–July was proposed together with a minimum harvest size of 45 mm.

A study was conducted on the relationship between the reproductive cycle and shell growth rate of Anadara granosa (Linnaeus, 1758). Gonadal maturity stages, increment width, and environmental factors were examined by means of a field enclosure experiment in Balik Pulau, Penang Island, Malaysia, from December 2011 to November 2012. Histological analysis of gonads showed that gametogenic activity of A. granosa occurred throughout the year, with maximum spawning activity observed from April 2012 to late June 2012 (15%–28%) in males and from March 2012 to late June 2012 (19%–44%) in females. Shell cross-section analysis showed that the increment widths of both sexes in the growing group (indeterminate and developing stages) and the spawning group (ripe and spawning stages) ranged from 35–57 to 8–17 µm, respectively. Seawater temperature and salinity recorded on a daily basis throughout the study period ranged from 22–33°C and 29–31, respectively. A comparison of increment width and gonad development stages in different environmental conditions showed that shell growth in the growing group decreased when seawater temperature and salinity decreased slightly. In contrast, increment widths in the spawning group were much narrower and were influenced by energy consumption during ripe and spawning stages. This study shows spawning breaks in shell structure are considered markers for identifying the period of sexual maturity. Therefore, spawning breaks are suitable proxies for interpretation of the temporal changes in shell microgrowth lines in terms of reproductive cycle of cockle and understanding the number of spawning periods throughout the year.

Successful and sustainable oyster reef restoration relies on suitable substrate material that is both readily available and encourages long-term recruitment and growth of oysters. China is increasing oyster reef restoration, however, little information is available to guide sustainable practices under local conditions and on ecologically relevant time scales. This study examines the effects of four substrate materials (oyster shell, clam shell, limestone, and clay brick) on community demographics for the Kumamoto oyster (Crassostrea sikamea) and associated macrofauna over a 3-y period in Xiangshan Bay, China. During the first 2 y, oyster and clam shell had similarly high recruitment and abundance of live oysters when compared with limestone and clay bricks. All substrate types, however, ended up with similar oyster abundances and size distributions after 3 y. Similar trends existed with regard to structural complexity (weight and volume) of substrate and any differences at the onset of the experiment were no longer apparent by the end. Abundance and community structure of associated macrofauna did not differ among the four substrate types regardless of time. These results indicate that different types of substrate material may be used for oyster reef restoration in China given projects have a scope longer than 2 y. These restored reefs can be expected to support viable and self-sustaining oyster populations with increased structural complexity and vibrant macrofaunal communities. Restoration practitioners using the Kumamoto oyster in China may use local materials as substrate for reefs and look forward to success where oyster recruitment is adequate and other factors such as predation and sedimentation are low.

The ubiquitous loss of natural intertidal oyster reefs and associated ecosystem services has fueled restoration efforts throughout the world. Effective restoration requires an understanding of the distribution, density, and demographic rates (growth and survival) of oysters inhabiting existing natural reefs and how these may vary as a function of landscape-scale factors, such as tidal range and fetch distances. Furthermore, natural intertidal habitats are increasingly being replaced with hardened shoreline structures that may be colonized by oysters, yet little is known about habitat quality (as indexed by oyster density and demographic rates) of these hardened structures relative to natural habitats. The present study sought to compare oyster density, demographic rates, and population estimates (1) across estuarine landscape settings to inform natural intertidal oyster reef restoration (i.e., comparing natural intertidal reefs within adjacent water bodies that vary in tidal regimes and fetch distances) and (2) across natural habitats and human-made structures to assess variation in habitat quality between natural reefs and hardened shorelines. Oyster density, growth rates, and population estimates on natural intertidal reefs were greatest within the smaller, more tidally influenced Core Sound versus the larger, wind-driven Pamlico Sound, with no significant difference in survivorship identified between the two water bodies. Natural intertidal reefs and hardened shoreline structures were compared within Pamlico Sound only, with natural intertidal reefs hosting three to eight times higher oyster densities than hardened shoreline structures. When mean oyster density/m² was multiplied by reef area to estimate population size, natural intertidal reefs within Pamlico Sound hosted considerably greater populations of oysters relative to hardened shorelines. The present study fills an existing need to understand oyster density and demographic rates on natural intertidal reefs and hardened shorelines to better inform future restoration and shoreline management scenarios.

The eastern oyster Crassostrea virginica once supported one of the largest fisheries in the eastern United States. Oyster populations and the reefs they form have suffered chronic long-term decline throughout the species' range, including in northwest Florida's Pensacola Bay estuary system (PBS). To guide efforts to rebuild oyster populations in the PBS, connectivity patterns were evaluated among historic and extant reef locations using an integrated biophysical numerical model. Water quality parameters and oyster recruitment were monitored in May 2007 and then monthly from July 2007 through July 2008. Resultant salinity data were used to calibrate an Estuarine Coastal Ocean Model—based numerical circulation model of Pensacola Bay, which was then coupled to an existing, individual-based, oyster larvae routine to predict ontogenetic larval distribution. Threedimensional Lagrangian transport algorithms were used to simulate transport of modeled larvae during four 20-day time periods during those summer and autumn months when oyster recruitment was empirically recorded in the bay. Based on outcomes from contemporaneous sampling of oyster larvae, the model was shown to represent the salient features of oyster larval distribution in Pensacola Bay. There were, however, instances of incongruity between modeled and sampled outcomes, indicating that model outcomes not validated with field data must be interpreted with caution. Larval supply was highly variable and spatially complex, but potentially limiting to successful recruitment and reef replenishment. Larval transfer rates within and among previously identified oyster reefs in Pensacola Bay were determined and were used to predict optimal oyster reef restoration or rehabilitation sites. Finally, larval exports from the bay were estimated and considered within the context of larval exchange among north Florida estuaries and potential repercussions to the long-term health of the Gulf of Mexico oyster metapopulation.

This work was undertaken to assess the effects that different environmental conditions of tropical and temperate aquaculture sites have on growth, survival, and reproduction of diploid and triploid Pacific oyster Crassostrea gigas. Diploid and triploid oysters were evaluated with the purpose of determining if the triploid condition results in any advantage on growth and survival that can be exploited for aquaculture of this species in tropical environments. The evaluations were performed by comparing three sites: two tropical sites in the Gulf of California and one temperate site in the Pacific Coast of the Baja California Peninsula, Mexico. When comparing tropical versus temperate sites, C. gigas growth and survival were less at the tropical sites regardless of ploidy. This can be attributed to environmental conditions, that is, high temperatures causing low productivity, in addition to an earlier-onset and sustained reproductive condition in the tropical sites when compared with the temperate site regardless of ploidy. Analyses of gonad maturation stages and number of oocytes among triploids indicated that a larger reproductive effort occurs at the tropical sites than at the temperate site. Regardless of the lower performance of both ploidy groups in the tropical environmental conditions, triploids grew significantly better than diploids in both tropical sites, and survival was the same for both ploidy groups. This contrasts with the marginal differences observed in growth between ploidies at the temperate site, where triploids showed lower survival than diploids. Possible causes for the lower triploid survival at this site are discussed.

Temperature is one of the main factors influencing biological processes of ectothermic species. An optimum temperature of 16–18°C has been suggested for the development of early life stages of temperate Australian abalone, yet there are little physiological or behavioral data to support this suggestion. This study examines the acute thermal preferences (T_pref), swimming speeds (U), and oxygen consumption rates (ṀO₂) of veliger larvae of blacklip abalone [Haliotis rubra (Leach, 1814)], greenlip abalone [Haliotis laevigata (Donovan, 1808)], and their interspecies hybrid. Thermal preference and U were measured in a thermal gradient with temperatures ranging from 12°C to 25°C, and ṀO₂ was measured at 4–7 temperatures between 12°C and 32°C. Thermal preference increased in all three groups of abalone during development from a T_pref of 16°C in 1-day-old early veligers to a T_pref of 20°C in 3-day-old late veligers. Swimming speed increased with temperature in all three groups of abalone and increased with age in H. rubra and hybrids but not in H. laevigata. Veliger ṀO₂ increased throughout the ecologically relevant temperature range in all three abalone groups. Higher temperatures were examined in hybrids, and it was found that ṀO₂ reached a peak at 25°C and declined thereafter. These results align with the temperatures that veligers may experience in their natural habitat and provide support that current temperatures maintained at Australian aquaculture hatcheries are within optimal ranges for larval performance.

A 16-wk feeding trial was conducted to assess the effects of different types of dietary carbohydrate on growth and body composition of juvenile abalone (Haliotis discus). A total of 1,680 abalone were randomly distributed among 24 containers (70 per container) and fed one of eight diets, including seven experimental diets containing different types of carbohydrates, including dextrin (DT), glucose (GC), corn starch (CS), α-cellulose (CL), maltose (MT), sucrose (SC), and wheat flour (WF), and Undaria to compare effect of experimental diets. Water stability of the diets was measured 12, 24, and 48 h after seawater immersion. Water stability of the diets was different over all periods of time and their significant interaction was also observed. Survival was not significantly affected by diet. Weight gain and specific growth rate were greatest in abalone fed on the CL diet. Shell length, width, height, and soft body weight were greatest in abalone fed the CL diet, followed by the WF, DT, SC, CS, GC, and MT diets and Undaria. Weight gain, specific growth rate, crude protein, and crude lipid contents of the soft body of abalone fed on the experimental diets were greater than those fed on Undaria. This study shows that CL is the most effective carbohydrate source for improving growth of this species of juvenile abalone and practically applicable in formulating abalone feed.

Abalone are planktonic larvae in their early life history stages, and their dispersal predominantly takes place during these stages. Abalone stocks rely on the natural supply of larvae in self-recruiting populations, larval connectivity in metapopulations, and artificial hatchery—produced larvae in regions where larval restoration is needed. Larval dispersal is, therefore, one of the key factors in the management of wild populations as well as in the establishment of resilient and genetically viable populations during restoration. In this review of abalone larval dispersal studies conducted in different regions of the world, evidence is found for three modes of larval dispersal; (1) short distance, (2) long distance, and (3) both short and long distance (dual mode). Four biological factors (spawning, larval duration, vertical behaviors, and presettlement mortality) are proposed to influence larval dispersal. Consideration of larval dispersal mode, influential biological factors, and their interactions may improve estimation of connectivity in metapopulations for establishment of effective marine protected areas, which could help the recovery of declining populations and the conservation of endangered abalone species.

Hydrogen peroxide (H₂O₂) is used routinely by the abalone farming industry to induce spawning of adult abalone. The aim of the current study was to quantify DNA integrity of adult hemolymph cells as well as germ cells (oocytes and sperm) with different recovery times between spawning events. In addition, fertilization success of exposed germ cells was quantified. The results indicate that spawning events separated by short recovery (2–6 wk) will not provide sufficient recovery from H₂O₂-induced DNA fragmentation in adult hemocytes. It is recommended that the industry should ideally allow 6–8 wk between spawning events to prevent accumulation of DNA strand breaks in adults over time and to ensure adequate fertilization success to maximize farm production.

Four previously published metrics for determining nutritional condition in decapods were evaluated for efficacy, specifically a serum protein index and three hepatopancreas-based indices (dry weight index, percent tissue dry weight, and relative weight). Using the Caribbean spiny lobster Panulirus argus (Latreille, 1804) as a model, lobsters were subjected to 5 wk of controlled diets in a laboratory-feeding trial. Three of the four indices detected significant differences between lobsters fed 15% or 100% of their daily maximum food intake, but lobster size and molt stage significantly influenced several metrics. Dry weight index of the hepatopancreas performed best, but relative weight of the digestive gland was the least affected by lobster size and molt stage. As both are destructive methods that require dissection of the lobster, these may not be useful for all studies. Hemolymph serum protein concentration is nondestructive and can be assessed rapidly in the laboratory or field, but it is strongly affected by molt stage. Thus, consideration of potential confounding factors is essential in choosing the proper measure of nutritional condition in studies of decapods.

The tropically associated black mangrove (Avicennia germinans) is experiencing a climate-induced range shift and expanding into salt marshes of northern Florida, southern Louisiana and most recently, Horn Island, MS. To date, little is known about how black mangroves function as nursery habitat for important fishery species such as shrimps or how their increase may affect survival of such species. The main objective of our study was to determine habitat preference and survival rates of common, economically important penaeid shrimps in the presence and absence of the increasingly abundant tropical predator, the gray snapper (Lutjanus griseus). We also examined the effects of habitat identity and structure on juvenile white shrimp (Litopenaeus setiferus) and brown shrimp (Farfantepenaeus aztecus) behavior, using preference experiments in indoor mesocosms both with and without the predatory gray snapper. Results showed that shrimp prefer Spartina over Avicennia with or without predation risk. Survival of shrimp was lowest in sand and highest in medium-density Spartina. Thus, a marsh-to-mangrove habitat conversion could ultimately result in decreased shrimp survival.

European green crabs (Carcinus maenas) are voracious, invasive predators of molluscs and their range is expanding throughout the northwest Atlantic Basin. Green crabs rapidly established following the 2002 partial restoration of East Harbor (EH) (42″039330 N, 70″079430 W), a back-barrier salt marsh lagoon within Cape Cod National Seashore, MA, where crabs potentially contribute to abrupt shifts in bivalve abundance and compromise restoration outcomes. Green crab prey preferences and effects on molluscan assemblages at this site have not been documented. Between June and September 2013, the prey selections of green crabs were documented using mesocosm feeding experiments and green crab diet through stomach content analyses. To evaluate prey availability, molluscan assemblage characteristics were also characterized using benthic coring. In the mesocosm experiments, green crabs strongly preferred large softshell clams [Mya arenaria (Linneaus, 1758)] and also chose small M. arenaria and Baltic clams [Macoma balthica (Linneaus, 1758)]. Crabs infrequently chose quahogs [Mercenaria mercenaria (Linneaus, 1758)], and only small individuals. Six dietary groups were documented in stomachs of crabs captured in the field; arthropods, molluscs, and vegetation were common stomach contents. Twelve molluscan species were detected throughout EH, many of which likely serve as prey for green crabs. Although mollusc abundance in EH has fluctuated because restoration began, the mollusc community remains sufficiently diverse and abundant to provide ample food for green crabs. In this nascent, simplified system, green crabs have few if any predators and thus may exert greater influence as a predator in EH than in other, more well-developed benthic communities.

Although the European green crab Carcinus maenas has persisted in Oregon and Washington coastal estuaries, and thrived in the inlets of the west coast of British Columbia since 1998, populations of this species had not established themselves in the inner Salish Sea, between southern Vancouver Island, the mainland, and Puget Sound. It has been hypothesized that the Strait of Juan de Fuca acts as a semipermeable barrier preventing C. maenas larvae from entering this inland sea. Most years, the water is too cold (<10°C) for larvae to develop and the predominately estuarine surface outflow flushes larvae out to sea. In late August and September of 2016, a total of five live Carcinus maenas were discovered in Westcott Bay and Padilla Bay, Washington, suggesting that this species recently entered the inland sea as larvae. Unusually warm surface water in the northeast Pacific (>2.5°C above average) from the fall of 2013 to 2015 would have allowed larvae to survive alongshore transport off the coasts of Oregon, Washington, and southern British Columbia. Reversals of the estuarine current in the Strait of Juan de Fuca forced by strong southerly winds associated with major storms along the outer coast in late October 2014 and 2015 could have transported the warm ocean water and larvae inward through the strait and, with the aid of local winds and tidal currents, into the inner Salish Sea. Preferential inward transport would have been with the Olympic Peninsula Countercurrent that forms along the U.S. side of the channel.

Major rocky intertidal predators in the northeast Pacific such as sea stars, whelks, and birds can consume foundation species such as mussels and thereby affect zonation patterns and diversity in these habitats. Predation specifically on juvenile intertidal invertebrates can also substantially impact population dynamics and influence community structure. The lined shore crab Pachygrapsus crassipes (Randall, 1840) is an abundant denizen of sheltered and exposed intertidal habitats in the northeast Pacific from Canada to Mexico. This study examined potential P. crassipes predation on juvenile mussels (Mytilus galloprovincialis), whelks [Nucella ostrina (Gould, 1852)], and abalone [Haliotis rufescens (Swainson, 1822)] due to conflicting reports on the diet of this species. Crabs consumed more juvenile mussels and abalone than seaweed (Ulva lactuca) and fed preferentially on the smallest mussels (6- to 10-mm size class). Further experiments showed that predation on mussels by P. crassipes was highly size dependent, with the largest crabs consuming over twenty-five 15-mm mussels per day. Field outplant experiments revealed that P. crassipes consumed high numbers of juvenile mussels in a natural setting, meaning that it could substantially affect mussel recruitment. This crab species appears to be an opportunistic predator that could have significant impacts on the recruitment and early life history of several invertebrate prey species.

This research tested the null hypothesis that there is no seasonal variation in the recruitment, body size, and growth status of juvenile Callinectes sapidus and Callinectes similis at a soft sediment site at Port Fourchon, LA, which varied in collection salinity between 17 and 37. Monthly collections of 5- to 30.6-mm carapace width (CW) juvenile crabs were made with a push net between March 2007 and February 2009. Juvenile C. sapidus were primarily recruited in March 2007, November 2007 to February 2008, June and July 2008, and in December 2008 and January 2009, whereas the major recruitment times for C. similis were April–October 2007,March–May 2008, August through October 2008 and February 2009. The ratio of juvenile C. sapidus:C. similis was not significantly related to the ambient salinity at the time of collection. The average wet weight, dry weight, and ash-free dry weight of a standard 17.5-mm CW blue crab and lesser blue crab was determined monthly with second-degree polynomial (quadratic equations fit to the data). Juvenile 17.5-mm CW C. sapidus was considerably heavier than C. similis but the percent ash of juvenile crabs of both species was the same. Missing appendages indicative of agonistic interactions or sublethal stress of both species in all collections containing at least 10 crabs were 18.7% of juvenile C. sapidus compared with 16.3%of C. similis. RNA:DNA ratios of both species indicated robust growth potential at all collections. Agonistic pressure on juvenile crabs of both species by adult blue crabs and other predators and other juvenile crabs likely limits the population size of C. sapidus and C. similis in lower Barataria Bay.

Populations of the black sea urchin Arbacia stellata present in the Gulf of California and outer Pacific Coast area are probably the result of colonization from the Panamic region. In the Pacific Coast of Baja California, this species experiences seasonal fluctuations of temperature. It was determined the preferred temperature (PT), critical threshold limits represented for Critical Thermal Maximum (CTMax) and oxygen consumption rate in organisms acclimated to 16°C, 19°C, 22°C, and 25°C in controlled conditions. The PT of A. stellata was determined in organisms using the acute method. As the acclimation temperature increases, the PT also increases significantly (P < 0.05) and decreases to 22.8°C. In the acclimation temperature of 25°C, PT for black sea urchins was 23.3°C ± 0.3°C. A direct relation was determined between the CTMax and acclimation temperatures being of 36.48°C ± 0.6°C, 37.64°C ± 0.76°C, 38.08°C ± 0.94°C, 38.42°C ± 0.71°C. The end point of CTMax was stage E4, where the sea urchins stop moving, relax the large spines but activity continues with light movements of small spines and when the organisms lose the ability to remain attached to the substrate. The oxygen consumption rates increased significantly (P < 0.05) from 5.59 to 11.5 mg O2 kg/h wet weight (w.w.) as the acclimation temperature increased from 16°C to 25°C. The range of temperature coefficient (Q10) between 16°C and 25°C (lowest) was 1.90, indicating that within that range of acclimation temperature, organisms are adapted to maintain homeostasis. This corresponded with the interval of PT of the species. These results may partially explain their distribution pattern in Baja California Coast.

Understanding the population structure of a commercially fished species and how those populations change over time is essential for proper management. Although the blue crab Callinectes sapidus (Rathbun, 1896) covers a large geographic range spanning two continents and several distinct ecosystems, there are no clear morphological characters and a paucity of genetic data that can be used to distinguish populations within and among management areas. In this study, diversity indices were calculated for four loci in the mitochondrial genome of C. sapidus using specimens collected from the Rhode River in Maryland during the summers of 2003 to 2005. The locus with the highest diversity, which occurs within the open reading frame of the nad2 mitochondrial gene, was then used as a marker to determine population structure for samples collected from the Atlantic locations of the Chesapeake Bay; Raleigh, North Carolina; Meadowlands and Tuckerton, New Jersey; and Massachusetts, as well as locations in the Gulf of Mexico spanning the waters of Florida, Alabama, Mississippi, and Texas from 2003 to 2008. For the entire dataset, the genetic variation within each sample site accounted for 99.5%of the total diversity. Also, the Atlantic sampling sites could not be distinguished from the Gulf of Mexico sites using Bayesian inference. Interestingly, the sampling sites from Massachusetts did not show a reduction in their level of genetic diversity despite its location at the northern limit of C. sapidus habitat. There were significant differences looking temporally, however, with the 2003 samples, the year of hurricane Isabel, differing from the 2004 and 2005 samples. Using the nad2 marker along with four microsatellite loci on a sample of 28 megalopae entering the mouth of Chesapeake Bay also demonstrated extremely high diversity at all loci, and the megalopae were significantly different from an adult population of the same year at two of the microsatellite loci. This indicates that genetic diversity is high in adult as well as larval populations and that offshore mixing may be playing a large role in the observed diversity shared among geographically distant habitats. Seasonal weather patterns during larval development followed by selection during the multiple subsequent recruitment events may play a large role in shaping local populations, and larval transport and settling models will provide much more understanding of the population dynamics of this species.

The Atlantic blue crab [Callinectes sapidus (Rathbun, 1896)] is a commercially and recreationally important decapod crustacean found in estuarine and nearshore waters of the western Atlantic. Recent declines in abundance, compounded with a scarcity of biological and genetic information, have made blue crab a high-priority species for research and conservation in South Carolina (SC). A suite of microsatellite loci was used to estimate the genetic diversity and effective population size of blue crab collected from Charleston Harbor, SC, in 2012 to 2013. Genetic diversity of the Charleston Harbor blue crab population was relatively high, whereas inbreeding was fairly low. Effective size estimates were on the order of several hundred to several thousand individuals. The results of our study exhibit good indications for the overall genetic “health” of the Charleston Harbor blue crab population and provide valuable information that can be incorporated into management plans to aid in the conservation of blue crab in SC.

Previous genetic studies of the blue crab Callinectes sapidus along the U.S. Atlantic and Gulf coasts have reported weak or temporally variable spatial structure, suggesting high gene flow among distant populations possibly facilitated by long-distance larval dispersal or other features of blue crab life history. The use of relatively few genetic markers, however, may have limited power to detect subtle but significant structure that could inform fisheries management. In this study, the potential for genome-scale datasets to uncover subtle patterns of population structure in the blue crab was examined using a high-throughput genotyping approach (genotyping-by-sequencing) that generated data for more than 9,600 single nucleotide polymorphisms (SNPs) in crabs from three populations: Panama City Beach, FL, Agawam River, MA, and Porto Alegre, Brazil. Principle components analyses among the three populations revealed very distinct clustering of the Brazilian samples from U.S. populations, likely reflecting restricted gene flow across the equator. Detailed analysis of population structure between the two U.S. populations revealed low but significant genetic differentiation (F_ST = 0.0103), with F_ST values ranging from -0.05 to 0.48. Previous studies have failed to detect significant genetic structure on a similar geographic scale. F_ST outlier analysis identified 242 loci (2.45% of total) with statistically extreme values at the false discovery rate α = 0.05 level, only 16 of which showed significant sequence homology to annotated proteins via BLASTx alignment. Top BLASTx hits were to crustacean or arthropod sequences and 8 of the 16 had high sequence similarity to transposable elements or related machinery. Finally, results of population assignment tests for the two U.S. populations showed that the full marker dataset provided good power to assign individuals back to their population of origin (∼83% and 92% success for Panama City Beach and Agawam River, respectively), which dropped significantly when using only 500 randomly selected SNPs (∼61% and 72% success). Overall, this study demonstrates the great utility of high-throughput sequencing technologies for characterizing fine-scale patterns of genetic structure in blue crabs, and this approach should substantially improve the delineation of stock structure and further advance our understanding of blue crab population connectivity and ecology.

Heteroplasmy is the presence of multiple genotypes in an individual and is commonly associated with mitochondria where thousands of copies of the genome can be present in a single organelle. Even in low frequencies, it can cause severe illness or death and strong selective pressures usually result in a low occurrence. Despite this, cloning and sequencing of a portion of the open reading frames of the nad2, nad4, and coI mitochondrial loci in the blue crab Callinectes sapidus (Rathbun, 1896) revealed abnormally high levels of heteroplasmy at all loci with as many as 24 haplotypes in a single individual and the dominant haplotype accounting for as little as 43.9% of the total sequences. A minimum spanning network comparing these individuals at each locus demonstrated an overlap of haplotypes between the female and themegalopa with almost no overlap of themale sequences. Illumina sequencing ofmuscle and testes froma single individual usingmultiple differentDNA-based amplificationmethods as well as cDNA amplification confirmed heteroplasmic circular mitochondrial DNA templates with portions of the reads containing unmapped highly repetitive regions at specific sequence positions in both tissue types. Thus, the blue crab appears to possess a highly degenerate and possibly fragmented mitochondrial genome that is present in germline tissue and linearly inherited. A general lack of fragmentation present in the cDNA sequences as well as site-specific sequence changes argues for mitochondrial editing as a way of maintaining sequence integrity. This is the first evidence for mitochondrial editing in a crustacean and a potential explanation for observations of extremely high population diversity when using blue crab mitochondrial markers.

In the blue crab Callinectes sapidus (Rathbun, 1896), double ejaculations have been observed; however, it is not known if these multiple inseminations are the products of different males or if they lead to effective multiple paternities. In this study, 75 mature females and their spermathecae were genotyped for five polymorphic microsatellite loci. The incidence of multiple paternity was analyzed by comparing the genotypes of either spermathecae or individual ejaculates with the corresponding mother, and the male contribution was then deduced. Females contained double ejaculates (5.3%),which genotyping confirmed as the products of different males. In addition, a routine screening of 68 crabs from a single hatchery brood at two loci indicated more than two parents. Mitochondrial analysis confirmed that the brood shares the same mother; therefore, the extra alleles must be due to different fathers. Our findings indicate that female blue crabs are not only capable of mating with more than one male but that multiple inseminations can lead to multiple paternity within a brood.

Before animals reared in captivity can be used as a model for study or as a supplement for wild populations, it is important to demonstrate that they can integrate with high success and without adversely affecting the natural population. For the blue crab Callinectes sapidus (Rathbun, 1896), coded wire tags have been used to positively discriminate hatchery-raised individuals from wild. This technique can be prohibitively expensive, however, due to high start-up costs and manpower needs during implantation, and mortality as a result of the tagging process is also a consideration. To reduce costs and increase the number of possible individuals monitored per unit effort, the suitability of the mitochondrial gene nad2 as a genetic tag to identify hatchery-produced crabs was tested. Batches of juvenile crabs approximately 20 mm in carapace width were implanted with wire tags and released into a variety of locations in the upper Chesapeake Bay. Juveniles were later recaptured from release sites and scanned for wire tags in the field. Tissue samples from recaptured crabs were also sequenced with nad2 specific primers. Comparison of sequences from recaptured individuals to batch mothers showed 95% congruence in positive identification through wire tagging and nad2 sequencing and an ability to discriminate hatchery batches from wild crabs with 97.8% success. Thus, use of an nad2 marker as a genetic tag is as successful as wire tags in C. sapidus with lower costs and mortality.

The blue crab [Callinectes sapidus (Rathbun, 1896)] is a benthic decapod with a varied diet. The diet includes invertebrates and detrital material that can have relatively large amounts of chitin and cellulose, both of which can be difficult to digest for many organisms and often require the aid of specific bacteria in the gut microbiome. In this study, juvenile blue crabs were fed an optimized defined pelleted diet with a 20% replacement of wheat flour filler with either chitin, cellulose, or a 14%/6% mix of both, followed by a diet switch to the opposing ingredient. Crabs had increasing growth performance with increasing amounts of cellulose in the diet versus chitin and had an additional molt in most cases. This occurred during the initial phase and following the switch, indicating that performance can be recovered. Subsequently, cellulose and chitin digestion assays were used to show that the foregut, midgut, and hindgut were all able to significantly digest more cellulose than chitin with the majority of activity in the foregut and midgut. Implications for rearing and diet formulations as well as the role of cellulose and chitin digestion in the natural diet are discussed.