Ronald Goldberg

Strategies for enhancement of natural bay scallop, Argopecten irradians irradians, populations; A case study in the Niantic River estuary, Connecticut, USA

We investigated strategies to enhance populations of bay scallops,Argopecten irradians irradians (Lamarck, 1819), in a presumablyrecruitment-limited natural habitat. At present, the Niantic Riverestuary supports only a minor bay scallop population that is harvestedrecreationally. Three enhancement strategies were evaluated; (1)collection and redistribution of natural spatfall, (2) introduction andover-wintering of hatchery-reared stock into natural habitat to providenew spawning stock, and (3) over-wintering of hatchery-reared stock insuspension culture for creation of mobile spawner sanctuaries. Anassessment of natural bay scallop recruitment in the Niantic Riverconducted in 1997 indicated that few spat were found, they were widelydispersed within the river, and peak spawning occurred in late July1997. Direct re-seeding was evaluated as an enhancement measure byplanting hatchery-reared scallops (≌ 38 mm shell height) insmall-scale, 100-m2 plots at different times and densities.Time of planting and the inferred predation intensity were major factorsaffecting survival; whereas, planting density had no significant effect.Approximately 9,000 scallops (35–45 mm shell height), broadcastwithin an eelgrass bed in November 1997, had high over-winter survivaland underwent gametogenesis and spawning during 1998. Of 26,000 bayscallops (≌ 45 mm shell height) over-wintered in suspensionculture from 1998–1999, approximately 60–80%survived, and these scallops spawned in mobile sanctuaries, during thesummer of 1999. There is good potential for using aquacultural methodsfor enhancement of bay scallop populations when natural recruitment ispoor and habitat and environmental conditions are not limiting.

Some effects of gas-supersaturated seawater on Spisula solidissima and Argopecten irradians☆

Abstract Two size classes of the surf clam, Spisula solidissima, and the bay scallop, Argopecten irradians, were exposed to different concentrations of gas-supersaturated seawater in a flowing seawater system. Both species tested experienced no mortality when held in the control treatment maintained at 96% oxygen and 109% nitrogen. Mortality, gill tissue damage, gas emboli, membranous tissue blisters, and abnormal secretion of shell material were induced experimentally at elevated levels of gas supersaturation. Results indicate significant mortalities of surf clams and scallops held at 114% O2 and 195% N2, and at higher levels of gas concentration. These values suggest a point of reference for the bivalve culturist in identifying potential problems which can be caused by gas-supersaturated seawater.

Impact of Predation by the Invasive Crab Hemigrapsus sanguineus on Survival of Juvenile Blue Mussels in Western Long Island Sound

Abstract Hemigrapsus sanguineus (Asian Shore Crab) has shown a remarkable ability to colonize rocky intertidal communities along the east coast of the United States since its introduction in the late 1980s and is an important predator of juvenile Mytilus edulis (Blue Mussel) in invaded habitats. In this study, we used two field-caging experiments and the Kaplan-Meier model to assess the impact of predation by Asian Shore Crab on the survival of juvenile Blue Mussels in an intertidal habitat of western Long Island Sound along the Connecticut coastline. Five treatment levels (high-density enclosure, low-density enclosure, exclosure, partial cage, and open plot) were used in the 2007 experiment. The high-density enclosure treatment was omitted in the 2010 experiment since there was no statistically significant difference in the proportion of mussels surviving between low- and high-density crab treatments in 2007. In 2007, we measured a statistically significant difference in mussel mortality between exclosure and crab-enclosure cages, with crabs lowering the median survival time for mussels from 15.4 to 7.6 days. In 2010, we again measured a statistically significant difference in mussel mortality between exclosure and crab-enclosure cages, suggesting a crab effect on mussel survival. In the 2010 experiment, approximately 25% of the mussel mortality was attributable to crab predation, which reduced median survival time for mussels from 12.8 to 5.6 days. The median survival time for mussels exposed to the full complement of factors affecting survival (open plots and partial cages) was only 2–3 days. Our study shows that predation by Asian crabs may account for up to 25% of the Blue Mussel mortality in the intertidal zone at Black Rock Harbor. Further studies focusing on the importance of other biotic and abiotic factors are needed to understand the apparent declines in Blue Mussel populations and the interannual variability in recruitment success in this area.

Observations of Juvenile Lobsters, Homarus americanus, on a Rock-Reef in Long Island Sound

Abstract Movements of juvenile Homarus americanus (American Lobster; hereafter lobster) on and around a naturally occurring rock reef were monitored over a 3-year period. Lobsters were sampled with baited traps deployed at each often sites. Catch-per-unit-effort (CPUE) and number of lobsters collected per trap haul was calculated for each sampling event. Physical habitat, visually characterized by underwater video and diver observations, differed among sites. Lobster CPUE was significantly greater at rocky sites (>70% density of cobble and/or boulder) containing complex structure, vertical relief from the seafloor, and colonies of macroalgae, sponge, and hydroids. Lobster CPUE was highest from late June to mid-July. Lobsters ranged from 18 to 82 mm carapace length (CL), with 90.7% of tagged lobsters measuring between 30 to 60 mm CL. Relative lobster abundance remained similar over the course of the study. Catch data were kriged to illustrate spatial patterns of distribution. Over the study period, a total of 934 lobsters were tagged and 66 were recaptured, for an overall recapture rate of 7.1%. The majority of recaptured animals (88%) were found at the original tagging site or adjacent sites, with one lobster remaining at liberty for 397 days. Most juvenile lobsters showed fidelity to their initial site of capture on a small, relatively isolated patch of rock-reef habitat in the central basin of Long Island Sound.

Benthic Ecology of Northern Quahog Beds with Different Hydraulic Dredging Histories in Long Island Sound

ABSTRACT Mercaldo-Allen, R.; Goldberg, R.; Clark, P.; Kuropat, C.; Meseck, S.L., and Rose, J.M., 2016. Benthic ecology of northern quahog beds with different hydraulic dredging histories in Long Island Sound. This paper evaluates benthic community composition of four shellfish beds in Long Island Sound near Milford, Connecticut, where northern quahog or hard clams, Mercenaria mercenaria (Linnaeus 1758), were harvested by hydraulic dredge. These leased beds reflect a variety of dredging histories; 0 year (dredged just before sampling began), 1 year postharvest, 2 years postharvest, and an inactive clam bed left fallow for at least 10 years. Benthic sediment was sampled at 1- to 2-week intervals from June to October 2011 using a Smith–McIntyre grab. Benthic community composition was significantly influenced by dredging history and sampling month. Abundance of benthic organisms (number of individuals and biovolume) and total organic matter concentrations were significantly greater at the 0-year site than at the 1-, 2-, and 10+-year sites, and significantly greater at the 1- and 2-year sites than at the 10+-site. Newly settled bivalves, primarily Nucula spp. and Yoldia limulata, were significantly more prevalent on the recently harvested 0-, 1-, and 2-year sites vs. the 10+-year site and highest at the 0-year site. A significantly greater number of species was observed on the 1- and 2-year sites vs. the 0- and 10+-year locations. Species richness at the 0-year site was significantly lower than at the 1-, 2-, and 10+-year sites, whereas diversity and evenness at the 0-year site was significantly lower than at the 10+-year site. This study observed successional changes in community structure of inshore clam beds related to the length of time elapsed after harvest dredging.

Variability in sediment-water carbonate chemistry and bivalve abundance after bivalve settlement in Long Island Sound, Milford, Connecticut

Cues that drive bivalve settlement and abundance in sediments are not well understood, but recent reports suggest that sediment carbonate chemistry may influence bivalve abundance. In 2013, we conducted field experiments to assess the relationship between porewater sediment carbonate chemistry (pH, alkalinity (At), dissolved inorganic carbon (DIC)), grain size, and bivalve abundance throughout the July-September settlement period at two sites in Long Island Sound (LIS), CT. Two dominate bivalves species were present during the study period Mya arenaria and Nucula spp. Akaikes linear information criterion models, indicated 29% of the total community abundance was predicted by grain size, salinity, and pH. When using 2 weeks of data during the period of peak bivalve settlement, pH and phosphate concentrations accounted 44% of total bivalve community composition and 71% of Nucula spp. abundance with pH, phosphate, and silica. These results suggest that sediment carbonate chemistry may influence bivalve abundance in LIS.

Scanning Electron Microscopic Aids for Identification of Larval and Post-Larval Bivalves

ABSTRACT The identification of bivalve larvae and early postlarvae in plankton and benthic samples has long been a challenge, hampering both basic and applied research efforts in marine, estuarine, and freshwater environments. The usefulness of published optical micrographs of the early life-history stages of bivalves is limited because of the great morphological similarity of the imaged articulated shells, particularly at the early (straight-hinge) developmental stages. While a number of techniques have been refined in recent years and show promise for use in routine identifications of larval and post-larval bivalves (e.g., single-step nested multiplex polymerase chain reaction; in situ hybridization protocols through color coding with taxon-specific, dye-labeled DNA probes; coupled fluorescence in situ hybridization and cell sorting; and image analysis techniques using species-specific shell birefringence patterns under polarized light), no adequate comprehensive reference source exists that accurately depicts the morphology and morphometry of the shells of larval and post-larval stages of target bivalve species in a consistent format to assist in identification of such stages. To this end, scanning electron micrograph (SEM) sequences are presented of the disarticulated shell valves of laboratory-reared larval and post-larval stages of 56 species of bivalve molluscs from a wide spectrum of marine, estuarine, and freshwater habitats. Emphasis is placed on the usefulness of the morphology and morphometrics of consistently-oriented, disarticulated shell valves and associated hinge structures in discriminating the early life-history stages of these various bivalve species. Although the scanning electron micrograph sequences presented accurately depict the gross morphologies/ morphometrics and hinge structures of the disarticulated shell valves of the larvae and/or postlarvae of the 56 species of bivalves, it is important to emphasize that a scanning electron microscope is not necessary to observe even fine hinge structures associated with the early ontogenetic stages of these species. Such structures are readily visible using a wide range of optical compound microscopes equipped with high-intensity reflected light sources, although the disarticulated shell valves must be viewed in several planes of focus to discern the often subtle details seen clearly in the scanning electron micrographs. These morphological characters provide researchers with invaluable aids for the routine identification of the early life-history stages of these species isolated from plankton and benthic samples.

Correction to: Effects of clam dredging on benthic ecology of two cultivated northern quahog beds with different harvest histories and sediment grain sizes

The original version of this article unfortunately contained an error where the symbol for phi size was inadvertently omitted from the text.