As a result of insufficient sampling, differences in estuarine attributes, species variation, and poor links to anthropogenic sources, responses of bivalve mollucs to anthropogenic nutrient enrichment of coastal waters remains poorly defined for most systems worldwide. To establish the net effect of nutrient enrichment on bivalves, we compared changes in growth and survival of different bivalve species reported in 5 studies conducted in a representative estuarine system (on Cape Cod, MA) in which effects of eutrophication on food supply and habitat were quantified and related directly to land-derived nitrogen (N) sources. N-stable isotope ratios in suspended particulates and bivalve tissues demonstrated that N derived from anthropogenic wastewater was assimilated into bivalve tissues as N loads increased. Bivalve shell and soft-tissue growth also increased in response to increased chlorophyll a concentrations driven by land-derived N loads. Growth was accompanied by increased percent N content of tissues in some species, suggesting a change in tissue composition with N enrichment. In contrast, bivalve survival was lower in years of higher microalgal production, suggesting eutrophic-driven habitat degradation may have contributed to mortality. The net effect of eutrophication on bivalves, therefore, depended on the balance between enhanced food supply and habitat alterations that are mediated by attributes of the receiving estuary, and differences among species, particularly feeding habits, feeding physiology, and tolerance to hypoxia.

Growth of Pteria penguin pearl oysters was monitored for 20 mo, from April 2009 to November 2010, to investigate differences in growth performance at three dissimilar sites: Pioneer Bay, Cape Ferguson, and Horseshoe Bay in the Great Barrier Reef lagoon. Growth parameters generated with the von Bertalanffy growth function ranged from K = 0.09–0.32 and L_∞ = 283.6–822.5. Overall growth performance (Φ′) ranged from 4.40–4.77. Time to reach commercial size (T₁₀₀) was between 1.38 y and 1.54 y, and T₁₂₀ was between 1.74 and 1.92 y. A more accurate estimate of the L_∞ = 213.4-mm dorsoventral measurement (DVM) was obtained at Pioneer Bay by using a larger data set that incorporated a wider size range of oysters. Overall monthly increase in DVM of oysters held at Horseshoe Bay (5.3 ± 0.2 mm) was more than that at Pioneer Bay (4.7 ± 0.2 mm) and Cape Ferguson (4.9 ± 0.2 mm), and there were significant differences in the monthly DVM increase among the sites during growth measurement periods (P < 0.05). Monthly DVM growth was fastest (7.2 ± 0.2 mm) in small oysters (DVM, 50–70 mm) in the spring and summer and was lowest (2.4 ± 0.4 mm) in larger oysters (DVM, 105–110 mm) during the spring. Regression analysis showed anteroposterior measurement (APM), shell thickness (ST), and whole weight (WW) were significantly correlated with DVM for all groups (P < 0.001). In the commercial size class of 100–120 mm DVM, mean WW of oysters at Cape Ferguson was significantly greater (P < 0.01), and the APM-to-DVM ratio was also significantly greater for oysters at Cape Ferguson and Horseshoe Bay (P < 0.01), whereas there were no significant differences among groups with regard to the ST-to-DVM ratio. At all 3 sites, the highest mortalities (measured as a percentage) were recorded for small oysters (DVM, 25–50 mm) during the winter period. Suspended particulate inorganic matter (measured in grams) levels were significantly different among sites (P < 0.001). Comparison among growth rates obtained during this study demonstrate that there is significant variability in growth between sites in the Great Barrier Reef lagoon, and that P. penguin are able to tolerate—and even thrive-under a wide range of turbidity levels.

Diploid and triploid Eastern oysters, Crassostrea virginica, were tested at 3 sites characterized by low or moderate salinity regimes in the Virginia part of the Chesapeake Bay from November 2005 through October 2007. Both diploid and triploid cultures were replicated 3 times by producing separate spawns from different broodstock. Ploidy had a generally consistent effect on the performance of C. virginica at the 3 test sites. At the end of the study, in October 2007, and across all sites, triploid oysters had lower cumulative mortality than diploids (-34%), and greater shell height ( 25%), whole weight ( 88%), and yield ( 152%). as well as a higher proportion of market-size oysters ( 114%) than diploids. Both diploids and triploids were similarly infected by Perkinsus marinus and, to a lesser extent, by Haplosporidium nelsoni. In a closer look, growth parameters (shell height growth, whole weight, yield, and percentage of marketable oysters) were always higher in triploids than in diploids regardless of the parental source, strongly supporting the superior advantage of triploids. Similar results were obtained for cumulative mortality, but to a lesser extent as a result of the large variation in mortality for both diploid and triploid cohorts among sites, as well as a significant site-by-cohort interaction. Our report is the first clear illustration of variation for the cumulative mortality exhibited among different spawns in triploids, and comes with the lesson that care must be taken in experiments in which the goal is to test the effect of ploidy on this trait. Our results support the notion that selective breeding programs to reduce mortality, coupled with triploid production to increase growth, can further optimize yield. The best-performing replicate spawn had 80% survival after 2.5 y, and reached an average shell height of 92 mm, weighing 142 g.

The DNA amplified fragment length polymorphism (AFLP) fingerprinting approach was used to identify a shell color-linked marker in the noble scallop Chlamys nobilis Reeve. The marker B1f176 was linked completely to the gene for bright-orange shell color with no recombination in the progeny we sampled. This marker was amplified in bright-orange parents and all orange progeny, but was absent in all of the brownish purple progeny. Nevertheless, AFLP markers are not feasible for large-scale application. Thus, we converted B1f176 into a sequence-characterized amplified region (SCAR) marker that we designated as SCAR Orange-142. The marker Orange-142, like the AFLP band from which it was derived, amplified a robust band in only the bright-orange scallops, both in F₁ and F₂ families as well as in a test group obtained from a seafood market. These results indicate that Orange-142 is tightly linked to the gene for orange shell color. In all but 1 of 10 F₂ families derived from bright-orange F₀ grandparents, the observed frequencies of orange progeny were consistent with Mendelian ratios expected from a 1-locus 2-allele system in which the brownish purple genotype was recessive. This study is the first report of the genetic basis for shell color in C. nobilis. The identification of a shell color-linked marker in the noble scallop improves our understanding of shell color inheritance and may contribute to C. nobilis broodstock enhancement programs using marker-assisted selection.

Supply of softshell clam (Mya arenaria) seed for culture and restoration usually comes from hatcheries or through transfers from one site to another. Natural spat collection using Astro-Turf mats installed directly onto the sediments could be a viable alternative. Here, we describe a series of experiments to examine the performance of mats for benthic collection, and how to use them efficiently. Interannual variability was studied for an 8-y period (2002 to 2009) at a commercial clam culture site located in the Havre-aux-Maisons lagoon (Îles-de-la-Madeleine, southern Gulf of St. Lawrence). Spat collection (clams, 2.5–15 mm) ranged from 883–2,422 clams/m² (overall mean, 1,599 clams/m²). Throughout the years, clams on the mats were 7 times more abundant than in the nearby sediments. Their mean shell length varied from 7.3–9.9 mm relative to the year. Mats were deployed during an extended 5-wk period (early June to early July), and also retrieved during an extended 5-wk period (early September to early October) with no negative effect on collection success. Indeed, spat abundance was higher when mats were retrieved later in the season (late September to early October). Spat collection was greater at the mid to upper intertidal level (1,551–2,622 clams > 2.5 mm/ m²) compared with the lower intertidal (near-subtidal) level (586 clams > 2.5 mm/m²). Indeed, the lowest abundances and the smallest sizes were observed on mats deployed at the lower intertidal level. Mats were installed side-by-side in groups of 35 (7 × 5), with no negative impact on collection success compared with individual mats. Last, spat collection was examined at two different sites within the lagoon for 4 y. Although the overall mean number of clams was similar at both sites (1,538 clams > 2.5 mm/m² vs. 1,503 clams > 2.5 mm/m²), collection success varied among sites (951–1,916 clams > 2.5 mm/m² vs. 552–2,938 clams > 2.5 mm/m²) from year to year. Therefore, collection success with mats should be investigated for any new site and for several years.

Both red snow crab (Chionoecetes japonicus Rathbun, 1932) and snow crab (Chionoecetes opilio Fabricius, 1788) are commercially important species in Korea. The geographical ranges of the two species overlap in the East Sea, where both species are fished commercially. Morphological identification of the two species and putative hybrids can be difficult because of their overlapping morphological characteristics. The presence of putative hybrids can affect the total allowable catch (TAC) of C. japonicus and C. opilio, and causes problems managing C. japonicus and C. opilio wild resources. To date, however, no natural hybridization has been reported between C. japonicus and C. opilio, despite their overlapping distributions along the coast of the East Sea. In this study, the internal transcribed spacer (ITS) region of major ribosomal RNA genes from the nuclear genome and the cytochrome oxidase I (CO I) gene from the mitochondrial genome were sequenced to determine whether natural hybridization occurs between the two species. Our results revealed that all putative hybrids identified using morphological traits had two distinct types of ITS sequences corresponding to those of both parental species. Mitochondrial CO I gene sequencing showed that all putative hybrids had sequences identical to C. japonicus. A genotyping assay based on single nucleotide polymorphisms in the ITS1 region and the CO I gene produced the most efficient and accurate identification of all hybrid individuals. Molecular data clearly demonstrate that natural hybridization does occur between C. japonicus and C. opilio, but only with C. japonicus as the maternal parent.

We present the first record of two nonnative Bivalvia species originally from North America, Mercenaria mercenaria and Ensis directus, in the waters of the Iberian Peninsula (southwest of the Bay of Biscay). This constitutes the southernmost distribution for these species in the northeast Atlantic to date. We provide notes on the relative abundance, depth range, and substrate preferences of the species in their new habitat. The bivalve E. directus has became the dominant Ensis species along the Cantabric sandy shores it has colonized.

Three selected mussel tissues (digestive gland, mantle, and gills) were studied to determine which was the most suitable for the potential use of the cellular energy allocation (CEA) methodology in indigenous mussels Mytilus galloprovincialis. In addition, the applicability of CEA in the assessment of natural stress caused by salinity fluctuations in stratified estuary was tested in selected tissues. It was important to identify the mussel gender to reliably assess the changes in organism energy budget. CEA value was calculated as a ratio between available energy (E_a) and energy consumption (E_c). Mantle tissue was under the strongest influence of the differences in protein and lipid content between male and female mussels, and therefore reflected physiological changes in the organism itself, rather than those caused by natural environmental stress. CEA in gills had lower values than in mantle and digestive gland, and was similar at two selected sampling sites, so the changes in CEA caused by natural stress could not be detected in the gill tissue. Greater E_c in mussels from the estuarine site than from the coastal site was detected only in the digestive gland tissue, and can probably be attributed to the energetically costly maintenance of osmotic balance. Last, using digestive gland tissue in CEA analysis demonstrated a clear difference between coastal and estuarine sampling sites, providing the measure of the natural stress posed by variations in salinity.

Three size classes of mussels (Mytilus spp.) (small, 26–35 mm; medium, 45–54 mm; and large, 65–74 mm) were exposed to 4 experimental diets consisting of mixed algae, diatom pastes, salmon feed “fines,” or salmon feces. Salmon culture byproduct particles (feces and feed fines) were found to have minimal effect on the biophysical properties of mussel feces when compared with those from an algal-based diet. Differences in fecal morphology (feces widths) of mussel feces were found to be minimal in small mussel sizes, but became more significant as mussel shell length increased (45–74 mm). Furthermore, faeces from fish farm-based diets were found to be significantly narrower than algal based diets. Absorption efficiencies of the 4 different diets were 87%, 81%, 90%, and 86%, respectively. Regardless of diet, small mussels produced feces that dispersed as a function of settling velocity (small, 0.18 cm/sec; medium, 0.29 cm/sec; and large, 0.54 cm/sec (settling velocity of 50% of particles)) over much larger areas than those feces produced by larger mussels, suggesting that the influence of mussel culture on benthic loading of organic material around an aquaculture site will tend to increase over time as the mussel crop grows to maturity.

This study determined the growth and biochemical composition of blue mussels (Mytilus edulis) reared on effluent from Atlantic cod (Gadus morhua) and compared it with mussels reared on a standard shellfish diet. Feeding trials lasted 6 mo, and mussels were sampled on a monthly basis. Dry weight, ash-free dry weight, shell length, and condition index were all significantly higher in algae-fed mussels at the end of the experiment compared with effluent-fed mussels. The carbon content decreased for mussels fed both diets; however, their nitrogen and protein content increased, with effluent-fed mussels having significantly more nitrogen and protein than algae-fed mussels, suggesting that effluent can increase mussel growth. Total lipid and fatty acid (FA) content decreased for effluent-fed mussels at the end of the experiment. There were no significant differences in the lipid class composition between mussels fed the 2 diets. Mussels fed both diets significantly decreased in the amount of 14:0, 16:1ω;7, 16:2ω;4, 16:4ω;1 and 20:5ω;3, and effluent-fed mussels also decreased in 18:4ω;3 and 21:5ω;3, as well as increased in the amount of 17:1, the Zooplankton markers 20:1ω;11 and 22:1ω;11, and the dienoic nonmethylene-interrupted fatty acids (NMIDs) 20:2a and 22:2b. Significant differences in the amount of individual FAs between mussels fed the 2 diets included a larger amount of 18:2ω;6 and 20:4ω;6 in algae-fed mussels, and a significantly larger amount of 16:4ω;1 in mussels fed effluent. Mussels fed both diets underwent significant increases in the proportion of bacterial FAs, ω;6 FAs, Zooplankton markers, and NMIDs. Effluent-fed mussels had a significantly larger proportion of monounsaturated FAs, Zooplankton markers, and NMIDs, as well as a smaller proportion of polyunsaturated FAs, and ω;3 and ω;6 FAs than algae-fed mussels. The increased presence of Zooplankton markers supports the use of these FAs to track aquaculture wastes.

Vibrio cholerae may cause diarrheal diseases and wound infections, both of which have the potential to be fatal. Transmission to humans is often linked to consumption of contaminated shellfish/drinking water or dermal exposure to water (e.g. when swimming). In this study, we investigated whether different isolates of Vibrio cholerae differ in terms of accumulation, persistence, and viability when encountering blue mussels (Mytilus edulis). Mussel uptake and elimination of three different V. cholerae strains were compared: one fatal clinical non-O1/O139 isolate, one highly potent El Tor biotype, and one marine strain isolated from blue mussels. The results showed that the uptake of the marine strain was significantly higher than the clinical strain, but the elimination process of the marine strain was also more efficient. The El Tor strain was not at all ingested by the mussels. In addition, the survival of bacteria when incubated together with M. edulis hemocytes was tested in vitro. The viability of clinical strains was unaffected by the presence of hemocytes, and the marine strains were even more resistant and able to multiply. We conclude that the highly virulent El Tor biotype was not taken up by the mussels and could thereby escape the mussels' elimination process. The potentially fatal non-O1/O139 V. cholerae strain may accumulate in low numbers, but could be very persistent in mussels.

Stramonita haemastoma, the southern oyster drill, is a predatory gastropod that locates prey using waterborne chemical cues. These cues move by advection and are subjected to hydrodynamic forces such as turbulence, which can have significant effects on both the delivery of cues and on the efficiency and success of organisms that use chemical cues to find prey. We investigated how flow velocity and turbulence would affect oyster drill foraging behavior in a laboratory flume, and found that oyster drills would move upstream toward exudates from fouled oyster clumps but not toward seawater controls. We then measured foraging behavior in a range of flow conditions and did not find significant differences in either foraging success or efficiency among the flow treatments. We also found that a significant number of oyster drills would continue to move upstream even if cue delivery was stopped midway through the trial. Oyster drills placed their siphon near the sediment when oyster reef exudates were delivered through the sediment, and in turbulent flows when greater momentum delivered cues to the sediment. In all flow treatments, oyster drills spent ∼2.5 min motionless before proceeding upstream. Based on these observations, we posit that when first detecting an attractive cue, oyster drills evaluate the cue and flow direction using cues in the sediment and water column before making a decision to move upstream. While moving toward an attractive cue source, oyster drills will continue to move upstream even when the attractive cues are no longer being released, which allows them to find oyster reef habitats successfully in a range of flow conditions.

The banded tulip snail, Fasciolaria (Cinctura) lilium hunteria (Perry), is a predatory gastropod that is capable of subduing a wide range of prey items using multiple attack behaviors. However, the literature contains conflicting accounts of this predator's prey preferences, which vary between the extremes of strong preferences for snails over bivalves to opportunistic behavior in which prey are incorporated into the diet based on their relative abundance in the environment. Here we reexamine the extent to which prey items in the diet of F. hunteria are distributed in preference hierarchies to update the natural history data on this molluscan predator. We tested F. hunteria's preference between oysters, Crassostrea virginica (Gmelin), and snails, Urosalpinx cinerea (Say), two ecologically co-occurring prey items that require different attack behaviors to subdue. Based on cost-benefit analyses, U. cinerea is more energetically profitable than C. virginica, so we predicted that it should be favored by tulip snails. We offered both prey simultaneously to F. hunteria in a Y maze to test this hypothesis. Despite the vast differences between the prey items in terms of potential biomass reward, handling times, and risk to the predator, F. hunteria did not prefer either C. virginica or U. cinerea, live or crushed. Our results suggest F. hunteria has no strong preferences among prey items in its diet, and is an opportunistic predator. This study is an example of the necessity of revising natural history information at a time when accumulation of such data is declining. In light of our results, we discuss the importance of examining the sources of natural history information, and of considering the time period and theoretical framework in which natural history data were gathered and interpreted to prevent cascading error effects resulting from the use of flawed natural history observations.

Jorunna funebris is one of the nudibranch species with the largest distribution worldwide, but there is lack of information about its life history. To provide more information on embryonic development, 19 adult nudibranchs ranging in length from 1.3–6.5 cm were collected from the Gulf of Thailand for examination of embryonic development under laboratory conditions. The seawater conditions in the broodstock aquaria were as follows: temperature range, 22.3–26.3°C; salinity, 27.9–34.0 psu; dissolved oxygen, 7.0–8.3 mg/L; and pH, 7.2–8.9. Each nudibranch laid only 1 egg mass after culturing for 1–3 days. The egg masses of J. funebris ranged from 17.1–48.0 cm in length, and between 0.4 cm and 0.7 cm in width. The density of egg capsules varied from 27–64 egg capsules/mm² of egg mass (n = 4), and each egg capsule had 1–4 larvae inside (n = 9). The embryonic period (expressed as the mean ± SD) was 7.3 ± 1.0 days (n = 7 egg masses). Based on the results of uncleaved embryonic diameter, embryonic period, and shell pattern, the development mode of J. funebris could be defined as “planktotrophic development.”

We describe some growth aspects of Octopus vulgaris located along the eastern coast of Tunisia. Age and growth parameters of this species were studied from August 2004 to July 2005 using a modal progression analysis. Dorsal mantle length (DML)—weight relationships of O. vulgaris were established for males, females, and both sexes. Statistical tests show that growth is isometric. Comparison of the length (DML)—weight relationship for males and females does not show a significant difference. Absolute growth has been studied according to the Battacharya method, which allows one to determine the growth parameters of the von Bertalanffy model (L_∞, K, and t₀) and the age—length relationship. The asymptotic length (L_∞) and weight (W _∞) were estimated to be 28.3 cm and 6.8 kg, respectively. We compared results with other studies in different regions. They show a comparable weight growth to the octopus in the Gabès Gulf and Occidental Mediterranean, but not to those in the Atlantic. The monthly growth rate of eastern octopus stock is superior to that seen in the Gabès Gulf.

Changes in the number and abundance of the cohorts of jumbo squid are a demographic response associated with high variability in recruitment, and have implications for availability and accessibility to the fishing fleets. In this study, we analyzed the interannual changes in the size structure, recruitment, and sex ratio of jumbo squid Dosidicus gigas in the central Gulf of California, Mexico. Data were analyzed for the 2000 to 2009 fishing seasons (from March to November). The biological data were collected biweekly at the port of Santa Rosalía, Baja California Sur, during each fishing season. We recorded mantle length and mantle weight, and sex (male or female) was identified from morphochromatic properties of fresh gonads. We concluded that the mantle length structure of jumbo squid changed between 1 cohort and 3 cohorts from 2000 to 2009. In the study zone, the presence of 2 cohorts is common. The species shows positive allometric growth, and the females are more abundant than the males in the region. The comparison between the most important fishing grounds in the central Gulf of California (Santa Rosalia and Guaymas) showed similar patterns, such as the number of cohorts, sex ratios, growth pattern, and migration pattern identified between both coasts. We believe that this could be evidence of one population that is widely distributed in the central Gulf of California.

Specimens of Illex argentinus from trawl catches along southern Brazil were sampled between March 2007 and January 2008 to study aspects of their life cycle and the connectivity with stocks from the southern range of the distribution of the species. Small mature specimens occurred year-round, whereas those with a mantle length (ML) of more than 250 mm were rare in the warm months, from December to May. More than 79% of the mature females were mated, providing evidence of year-round spawning in southern Brazil. Mature males were 131–330 mm and 147–275 days old, and females were 166–341 mm and 146–257 days old; mean ML at 50% maturity was 156.3 mm and 181.2 mm, respectively. The number of daily increments decreased from the capture date showed that hatching occurred year-round, mostly from August to January. Daily mean ML increment of juveniles to adults hatched during the warm season and caught during the cold season was larger than that of those hatched during the cold season and caught during the warm season, suggesting greater growth in winter and spring associated with increasing primary productivity in the region. A life cycle shorter than 1 y suggests genetic isolation neither between both seasons nor among larger and smaller adult squids. The number of daily increments in the postnuclear zone of the statoliths was substantially lower than that recorded for specimens maturing along Patagonian waters, suggesting that those squid do not reach southern Brazil.

Reproductive effort and population structure of the nonnative clam Corbicula fluminea were studied in an oligotrophic subalpine lake. Three shallow sites (5 m) and one deeper site (20 m) were studied between May 11, 2010, and November 5, 2010, to determine spatial variation and the influence of environmental conditions (e.g., temperature and food availability as determined by total organic carbon (TOC) and sediment particulate organic matter (SPOM) on reproductive effort. The clam C. fluminea exhibited a univoltine spawn cued by increases in temperature. Reproductive effort calculated for adult clams (13.67 ± 0.03 mm (SE), n = 1,875) across sites was not influenced by TOC and SPOM concentrations, and overall reproductive effort was less than more productive ecosystems, which may be a result of Lake Tahoe's ultraoligotrophy. All 3 shallow sites had similar levels of reproductive effort. Once veligers were observed, of the 603 clams then dissected, there were 10 ± 2 veligers per clam (±SE), 25 clams had≥100 veligers per clam (286 ± 28 veligers per clam), 78 clams contained less than 100 veligers (20 ± 2 veligers per clam), and 498 clams had no veligers present, indicating the population exhibits a highly variable reproductive effort. There was, at a minimum, a 4-wk delay from the point that temperatures reached a threshold for fertilization and veliger release until they were observed in dissected clams. At 20 m, C. fluminea were high in abundance compared with shallow sites, but contained few fully developed juveniles, indicating a potential population sink. Overall population structure was dominated by adult clams (≥13 mm), with a minimal presence of juveniles (≤4 mm).

Little is known about the nutrition or lipid metabolism of cold-water crabs, particularly in the North Pacific. We undertook a 2-part study to understand more completely the energetics and nutritional requirements of juvenile red king crab (RKC; Paralithodes camtschaticus). First, we investigated changes in proximate composition, total lipids (TLs), lipid classes, and fatty acids (FAs) throughout a molt cycle (C4–C5). Trends in lipid parameters were described by a 3-part piecewise linear regression with 3 distinct stages: (1) a postmolt phase (∼0–7 days), (2) an intramolt stage (∼7–24 days), and (3) a premolt stage (∼24–33 days). Significant intramolt differences in TLs indicated that caution should be taken when comparing crabs of unknown molt stage in future aquaculture and ecological experiments. However, little variability was found in the proportional FA composition of crabs, indicating that the intramolt stage has little effect on the interpretation of FA biomarkers. During a second investigation, we examined differences in lipid classes and FAs from cultured and wild RKC. We found significantly higher proportions of the essential fatty acids (EFAs) 20:5n-3 (EPA) and 20:4n-6 (AA) in wild crabs compared with cultured animals at the same stage. Furthermore, higher proportions of bacterial markers and lower proportions of Zooplankton FA markers were found in wild than in hatchery-reared crabs. Here, we provide the first baseline data for future dietary studies on juvenile cold-water crabs. We suggest that an initial EFA ratio for DHA:EPA:AA of 5:8:1 could be used as a starting point for controlled dietary studies on the effect of EFAs on juvenile growth, molt success, and survival.

The commercial fishery for American lobster Homarus americanus Milne Edwards in Maine has experienced the highest landings during the past 2 decades than at any time since the 1950s. However, there is no scientific consensus on why landings have increased nearly 250% from 1990 to 2010, and no one can predict how long landings can be expected to remain at current levels. This uncertainty has sparked a renewed interest in lobster stock enhancement using cultured individuals. Historically, lobster stock enhancement in North America has focused primarily on releasing early benthic phase (stage IV) animals. It is not cost-effective to feed and maintain animals in the laboratory or hatchery until they are larger (ca. stage X–XI), as is typical of enhancement efforts with cultured individuals of Homarus gammarus (L.) in Europe, even though survival to commercial size presumably would be greater. One difficulty with releasing early benthic phase animals is that they have the capacity to swim away from the release site, making tests to determine the efficacy of such programs logistically difficult and expensive. A low-cost, low-maintenance, ocean-based nursery grow-out system for stage IV H. americanus was tested in waters off eastern Maine using technology first developed and implemented successfully for cultured individuals of H. gammarus in Ireland. A single individual was added to a plastic soda bottle (ca. 350 mL) or Petri dish (440 mL) containing a series of small holes to allow continuous flow of seawater into and out of the units. Bottles (n = 630) and dishes (n = 420) were added to rigid nursery cages constructed of traditional vinyl-coated lobster trap wire and deployed in July 2002 ca. 2 m off the bottom in depths of 10 m, 15 m, and 25 m in and around Chandler Bay near Jonesport. After nearly 70 days, survival in the bottles varied from 20% at the deepwater site to 90% at the shallow-water site; however, after an additional 244–288 days, most bottles had filled with muddy sediments, and mortality rate was nearly 100%. Conversely, survival rates after 448 days in the dishes varied, on average, from 21.5–47.2% per cage originally deployed at the deepest and shallowest site, respectively. Growth rates in the dishes generally doubled during the 14-mo field trial from a carapace length of 4.2 mm to that of 8.9 mm. Results suggest that ocean nurseries can be used to rear cultured lobsters to larger sizes prior to release for stock enhancement purposes; however, these animals are too small to apply visible tags (i.e., streamer or T-bar tags) that fishers could discern easily.

Historically, stock enhancement programs for American lobster, Homarus americanus, have a common theme: production and release of large numbers of stage IV or stage V individuals. However, these animals are difficult to mark, highly mobile when released on the bottom, and susceptible to a wide array of predators, and their claws have yet to develop bilateral asymmetry. Many of these attributes make it difficult to test the efficacy of hatch-and-release efforts. It is possible to hold postlarval lobsters individually in the laboratory or hatchery and provide food regularly for several months to release older, larger individuals (as with enhancement efforts in Europe with Homarus gammarus). However, the costs to do so compared with the value of commercial-size animals makes this practice cost prohibitive. Attempts to reduce costs of rearing early postlarvae to larger sizes in ocean-based nursery cages in eastern Maine for periods of longer than 1 y have resulted in variable survival (in general, <50%) and slow growth (doubling in carapace length (CL) from 4.2–8.9 mm). A series of field trials (2004 to 2010) examined methods to improve survival rates and enhance growth with the goal of producing animals large enough to apply a physical tag that can be seen easily by fishers and scientists interested in testing directly the efficacy of enhancement efforts. The effect of flow rates into and out of various types of containers (350 mL and 440 mL) holding individual, cultured stage IV lobsters was examined experimentally during a 309-day period from August 2004 to July 2005 in off-bottom, ocean-based nursery cages deployed in shallow (12 m) water near Great Wass Island, Beals, ME. Mean survival rate varied directly with flow as animals in containers with the greatest exchange of seawater demonstrated survival rates of ca. 90% compared with ca. 30% in containers allowing lower flow rates. Sediment deposition in the low-flow rate containers tended to be high, and was associated with significantly lower mean lobster survival. In a separate field trial in shallow water from August 2009 to October 2010 (419 days), lobster growth in submerged wooden trays was assessed using 5 different container sizes that ranged from 0.02–0.26 m² (ca. 1.5–21 L). Growth was best described by a sigmoidal function, with a strong linear component over container sizes between 0.02 m² and 0.13 m² (ca. 1.5–10 L), and no significant difference observed in mean CL of lobsters in the largest 2 container sizes. Final mean CL and mass (23.9 ± 1.4 mm and 10.7 ± 2.1 g, respectively, ±95% CI) of animals in the 2 largest containers was 57.4% and 349% greater, respectively, than animals in the smallest containers. Rearing cultured individuals of H. americanus to large sizes in ocean-based nursery cages may provide managers of stock enhancement programs with a more viable assessment tool than those used traditionally.

In many animals, sex pheromones are involved in behavioral reproductive isolation, which is thought to be more important than other isolation barriers in causing rapid speciation. Lysmata species living in the western Atlantic waters have been recently redefined taxonomically, with some of the species having overlapping distribution. It has been found that prezygotic mating isolation is not complete between two Lysmata species—Lysmata wurdemanni and Lysmata boggessi—and there is asymmetry in mate recognition between the two species. Male-role L. wurdemanni can mate with female-role L. boggessi, but not vice versa. This study shows that the asymmetric mating isolation is caused by the difference in sex pheromone detection (both distance and contact sex pheromones). Male L. wurdemanni can detect and respond to distance sex pheromones secreted by female L. boggessi, even at low concentrations, but male L. boggessi did not respond to distance sex pheromones of L. wurdemanni at any concentration, which suggests that their asymmetric mate recognition is not caused by a different response threshold to conspecific and interspecific sex pheromones. Instead, minor differences in the molecular structure of sex pheromones and/or a different ratio in components of sex pheromones may result in asymmetric reproductive isolation.