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Daphne M Munroe - One of the best experts on this subject based on the ideXlab platform.
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energetic response of atlantic surfclam Spisula solidissima to ocean acidification
Marine Pollution Bulletin, 2020Co-Authors: Emilien Pousse, Matthew E Poach, Dylan Redman, George Sennefelder, Lauren E White, Jessica M Lindsay, Daphne M Munroe, Deborah R Hart, Daniel Reneau Hennen, Mark S DixonAbstract:Abstract In this study, we assessed the Atlantic surfclam (Spisula solidissima) energy budget under different ocean acidification conditions (OA). During 12 weeks, 126 individuals were maintained at three different ρCO2 concentrations. Every two weeks, individuals were sampled for physiological measurements and scope for growth (SFG). In the high ρCO2 treatment, clearance rate decreased and excretion rate increased relative to the low ρCO2 treatment, resulting in reduced SFG. Moreover, oxygen:nitrogen (O:N) excretion ratio dropped, suggesting that a switch in metabolic strategy occurred. The medium ρCO2 treatment had no significant effects upon SFG; however, metabolic loss increased, suggesting a rise in energy expenditure. In addition, a significant increase in food selection efficiency was observed in the medium treatment, which could be a compensatory reaction to the metabolic over-costs. Results showed that surfclams are particularly sensitive to OA; however, the different compensatory mechanisms observed indicate that they are capable of some temporary resilience.
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the effect of rearing temperature on the survival and growth of early juvenile atlantic surfclams Spisula solidissima
Aquaculture Reports, 2019Co-Authors: Michael P. Acquafredda, Daphne M Munroe, Lisa Ragone M. Calvo, Michael De LucaAbstract:Abstract The Atlantic surfclam (Spisula solidissima) is not currently cultivated on commercial scales, but it represents a potentially beneficial target species for crop diversification in the Northeast region of the United States. Surfclams are native to the region and rapid growth gives this species the potential to reach marketable sizes within 12 to 18 months. Since heating and chilling seawater are major operating costs for bivalve seed production, a thorough understanding of how temperature influences juvenile surfclam survival and growth during the nursery phase – the period between metamorphosis and out-planting – must be determined before mainstream production can occur. We assessed early juvenile rearing temperature by conducting a month-long study where post-metamorphic surfclams (initial shell length ≈0.7 mm) were exposed to one of five temperature treatments (18.0, 20.2, 23.2, 24.4, and 26.3 °C.). Survival was approximately twice as high at 18 °C compared to 26 °C. Growth was maximized at intermediate temperatures between 20 and 24 °C. Additionally, we monitored the survival and growth of juvenile surfclams for 20 weeks during the Northeast’s typical bivalve nursery operating season. Surfclams (initial shell length ≈1.5 mm) were reared at a commercial-scale using flow-through upwelling systems, supplied with ambient seawater from the Cape May Canal. Surfclam seed survival after the 20-week study was 52%, with most mortality occurring after the temperature peaked around 27 °C. The average growth rate over this study was 0.049 mm d−1. Our results suggest that juvenile surfclams should be reared in temperatures close to 20 °C for the duration of the nursery phase. Colder temperatures increase survival but tend to slow growth. Prolonged exposure to warm temperatures can cause severe mortality, yet juvenile surfclams seem to have the ability to tolerate short-term exposures to unfavorably warm temperatures. Across the Northeast, the ambient seawater should be sufficient for surfclam seed production at commercial scales.
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The effect of rearing temperature on the survival and growth of early juvenile Atlantic surfclams (Spisula solidissima)
Elsevier, 2019Co-Authors: Michael P. Acquafredda, Daphne M Munroe, Lisa Ragone M. Calvo, Michael De LucaAbstract:The Atlantic surfclam (Spisula solidissima) is not currently cultivated on commercial scales, but it represents a potentially beneficial target species for crop diversification in the Northeast region of the United States. Surfclams are native to the region and rapid growth gives this species the potential to reach marketable sizes within 12 to 18 months. Since heating and chilling seawater are major operating costs for bivalve seed production, a thorough understanding of how temperature influences juvenile surfclam survival and growth during the nursery phase – the period between metamorphosis and out-planting – must be determined before mainstream production can occur. We assessed early juvenile rearing temperature by conducting a month-long study where post-metamorphic surfclams (initial shell length ≈0.7 mm) were exposed to one of five temperature treatments (18.0, 20.2, 23.2, 24.4, and 26.3 °C.). Survival was approximately twice as high at 18 °C compared to 26 °C. Growth was maximized at intermediate temperatures between 20 and 24 °C. Additionally, we monitored the survival and growth of juvenile surfclams for 20 weeks during the Northeast’s typical bivalve nursery operating season. Surfclams (initial shell length ≈1.5 mm) were reared at a commercial-scale using flow-through upwelling systems, supplied with ambient seawater from the Cape May Canal. Surfclam seed survival after the 20-week study was 52%, with most mortality occurring after the temperature peaked around 27 °C. The average growth rate over this study was 0.049 mm d−1. Our results suggest that juvenile surfclams should be reared in temperatures close to 20 °C for the duration of the nursery phase. Colder temperatures increase survival but tend to slow growth. Prolonged exposure to warm temperatures can cause severe mortality, yet juvenile surfclams seem to have the ability to tolerate short-term exposures to unfavorably warm temperatures. Across the Northeast, the ambient seawater should be sufficient for surfclam seed production at commercial scales. Keywords: Atlantic surfclam, Spisula solidissima, Temperature, Rearing conditions, Nursery cultur
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biological reference points for atlantic surfclam Spisula solidissima in warming seas
Fisheries Research, 2018Co-Authors: Daniel Reneau Hennen, Daphne M Munroe, Roger Mann, Eric N PowellAbstract:Abstract Atlantic surfclam ( Spisula solidissima ) are a large, commercially important shellfish in the United States faced with several important management challenges. Compared to many harvested fish and shellfish, their life history is relatively unknown. They are undergoing contraction in the southern and inshore parts of their range, as well as expansion into deeper water. Atlantic surfclam are thermally sensitive, and the changes in their distribution track changes in maximum bottom temperature. Sessile species cannot emigrate and are limited to recruitment and mortality as mechanisms for redistribution in response to changing climate. Management of Atlantic surfclam should account for these challenges. We describe a simulation designed to calculate biological reference points that will work well for Atlantic surfclam relative to biological and fishery goals, over a range of life history parameters, assessment uncertainties, and increases in temperature. Simulations of the trade-off between somatic growth and mortality under increased temperature led to target fishing mortality rates higher than the status quo, but also to increased variability in yield. Results suggest that increasing temperature may adversely affect the Atlantic surfclam industry, which prefers stable catches to short term increases in yield, due to market limitations. The results of this analysis are specific to Atlantic surfclam, but the methods described here could be used to enhance management for other harvested species facing similar challenges.
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an overview of factors affecting distribution of the atlantic surfclam Spisula solidissima a continental shelf biomass dominant during a period of climate change
Journal of Shellfish Research, 2018Co-Authors: Eileen E Hofmann, Daphne M Munroe, Roger Mann, Eric N Powell, Diego A Narvaez, John M Klinck, Dale B Haidvogel, Xinzhong Zhang, Kelsey M KuykendallAbstract:ABSTRACT The Atlantic surfclam (Spisula solidissima) is a dominant member of the biological community of the Middle Atlantic Bight continental shelf and a commercially harvested species. Climate warming is affecting the biology and distribution of this species, which provides an opportunity to investigate the processes and conditions that are restructuring this fishery and the implications for ecological and socioeconomic systems. A Management Strategy Evaluation (MSE) developed for the surfclam fishery provides a mechanistic description of the surfclam's response to climate change and understanding of the cascade of effects initiated by changes in oceanographic conditions that ultimately appear as social and economic effects. This understanding in turn informs development of management policies for the resource. This overview considers the components of the surfclam MSE, relevant results, and implications for management and policy. The lessons learned from the surfclam MSE provide a basis for applying si...
Robert E. Palazzo - One of the best experts on this subject based on the ideXlab platform.
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reconstitution of microtubule nucleation potential in centrosomes isolated from Spisula solidissima oocytes
Journal of Cell Science, 2000Co-Authors: Bradley J Schnackenberg, Dawn Hull, Ronald D Balczon, Robert E. PalazzoAbstract:Treatment of isolated Spisula solidissima centrosomes with KI removes (gamma)-tubulin, 25 nm rings, and their microtubule nucleation potential, revealing the presence of a filamentous lattice, the 'centromatrix'. Treatment of this centromatrix with Spisula oocyte extract results in the binding of (gamma)-tubulin and 25 nm rings, and the recovery of microtubule nucleation potential. Fractionation of this extract resulted in the separation of elements that are required for the recovery of microtubule nucleation potential. We show that some, but not all, of the elements needed cosediment with microtubules. Further, extracts prepared from activated (meiotic) and non-activated (interphase) Spisula oocytes, CHO cells blocked in S phase, Drosophila embryos and Xenopus oocytes all support the recovery of microtubule nucleation potential by the Spisula centromatrix. These results demonstrate that components necessary for centrosome-dependent microtubule nucleation are functionally conserved and abundant in both interphase and meiotic/mitotic cytoplasm.
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dynein is required for spindle assembly in cytoplasmic extracts of Spisula solidissima oocytes
Journal of Cell Science, 1999Co-Authors: Robert E. Palazzo, Eugeni A Vaisberg, Dieter G Weiss, Sergei A Kuznetsov, Walter SteffenAbstract:Meiosis I spindle assembly is induced in lysate-extract mixtures prepared from clam (Spisula solidissima) oocytes. Unactivated lysate prepared from unactivated oocytes contain nuclei (germinal vesicles, GVs) which house condensed chromosomes. Treatment of unactivated lysate with clarified activated extract prepared from oocytes induced to complete meiosis by treatment with KCl induces GV breakdown (GVBD) and assembly of monopolar, bipolar, and multipolar aster-chromosome complexes. The process of in vitro meiosis I spindle assembly involves the assembly of microtubule asters and the association of these asters with the surfaces of the GVs, followed by GVBD and spindle assembly. Monoclonal antibody m74-1, known to react specifically with the N terminus of the intermediate chain of cytoplasmic dynein, recognizes Spisula oocyte dynein and inhibits in vitro meiosis I spindle assembly. Control antibody has no affect on spindle assembly. A similar inhibitory effect on spindle assembly was observed in the presence of orthovanadate, a known inhibitor of dynein ATPase activity. Neither m74-1 nor orthovanadate has any obvious affect on GVBD or aster formation. We propose that dynein function is required for the association of chromosomes with astral microtubules during in vitro meiosis I spindle assembly in these lysate-extract mixtures. However, we conclude that dynein function is not required for centrosome assembly and maturation or for centrosome-dependent aster formation.
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chapter 3 isolation of centrosomes from Spisula solidissima oocytes
Methods in Cell Biology, 1998Co-Authors: Robert E. Palazzo, Jacalyn M VogelAbstract:Publisher Summary This chapter describes the methods used for isolating centrosomes from oocytes of the marine surf clam, Spisula solidissima. The oocytes in Spisula are arrested in late prophase of meiosis I and are activated en mass by simply elevating the potassium concentration of the surrounding seawater. Once activated, the oocytes proceed synchronously through a number of critical cell cycle events, including centrosome assembly, germinal vesicle (nuclear envelope) breakdown, and assembly of the meiosis I spindle. The chapter then describes the methods for preparing lysates and obtaining functional centrosomes from oocytes 4 min after their activation. Once isolated, centrosomes can be used for protein analysis, ultrastructural studies, or in functional reconstitution assays. In addition, these preparations offer the isolation of sufficient quantities of centrosome proteins to be used as antigens for generating centrosome-specific antibodies or for obtaining protein sequence for the purpose of antibody production or the design of oligonucleotide primers for isolating cDNA fragments coding for centrosome proteins.
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centrosomes isolated from Spisula solidissima oocytes contain rings and an unusual stoichiometric ratio of α β tubulin
Journal of Cell Biology, 1997Co-Authors: Jacalyn M Vogel, Conly L Rieder, Tim Stearns, Robert E. PalazzoAbstract:Centrosome-dependent microtubule nucleation involves the interaction of tubulin subunits with pericentriolar material. To study the biochemical and structural basis of centrosome-dependent microtubule nucleation, centrosomes capable of organizing microtubules into astral arrays were isolated from parthenogenetically activated Spisula solidissima oocytes. Intermediate voltage electron microscopy tomography revealed that each centrosome was composed of a single centriole surrounded by pericentriolar material that was studded with ring-shaped structures ∼25 nm in diameter and a ) proteins that contained M-phase–specific phosphoepitopes (MPM-2), ( b ) α-, β-, and γ-tubulins, ( c ) actin, and ( d ) three low molecular weight proteins of
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Centrosomes isolated from Spisula solidissima oocytes contain rings and an unusual stoichiometric ratio of �/� tubulin
1997Co-Authors: Jacalyn M Vogel, Conly L Rieder, Tim Stearns, Robert E. PalazzoAbstract:Abstract. Centrosome-dependent microtubule nucleation involves the interaction of tubulin subunits with pericentriolar material. To study the biochemical and structural basis of centrosome-dependent microtubule nucleation, centrosomes capable of organizing microtubules into astral arrays were isolated from parthenogenetically activated Spisula solidissima oocytes. Intermediate voltage electron microscopy tomography revealed that each centrosome was composed of a single centriole surrounded by pericentriolar material that was studded with ring-shaped structures �25 nm in diameter and �25 nm in length. A number of proteins copurified with centrosomes including: (a) proteins that contained M-phase–specific phosphoepitopes (MPM-2), (b) �-, �-, and �-tubulins, (c) actin, and (d) three low molecula
Francois Dube - One of the best experts on this subject based on the ideXlab platform.
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characterization of a novel octopamine receptor expressed in the surf clam Spisula solidissima
General and Comparative Endocrinology, 2010Co-Authors: Veronique Blais, Nassim Bounif, Francois DubeAbstract:We have cloned and sequenced a cDNA from the surf clam (Spisula solidissima, a pelecypod mollusc) that encodes an octopamine receptor which we have named Spi-OAR. The sequence of Spi-OAR shares many similarities with two Aplysia and three Drosophila octopamine receptors belonging to a sub-group of beta-adrenergic-like octopamine receptors. Using an expression vector and transient transfections of Spi-OAR into HEK 293 cells, we observed an increase of cAMP upon addition of octopamine and, to a lesser extent, of tyramine, but not after addition of dopamine, serotonin, or histamine. Using a battery of known agonists and antagonists for octopamine receptors, we observed a rather unique pharmacological profile for Spi-OAR through measurements of cAMP. Spi-OAR exhibited some constitutive activity in HEK 293 cells and no Ca(2+) responses could be detected following addition of octopamine to Spi-OAR-transfected cells. RT-PCR analysis revealed ubiquitous expression of Spi-OAR mRNA in all adult tissues, oocytes and early embryos examined. While addition of serotonin to isolated clam oocytes resulted in meiotic activation, similar additions of octopamine had no effect, suggesting that its potential role in clam reproductive physiology differs significantly from that of serotonin. This work identifies Spi-OAR as a novel mollusc octopamine receptor closely related to other invertebrate beta-adrenergic-like octopamine receptors, with possible reproductive and other physiological functions. This initial characterization of Spi-OAR makes possible further investigations and comparisons with more studied and familiar insect or gastropod mollusc octopamine receptors.
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localization and quantification of gonad serotonin during gametogenesis of the surf clam Spisula solidissima
The Biological Bulletin, 2002Co-Authors: Isabfjllf Masseau, Pierre Bannon, Michel Anctil, Francois DubeAbstract:In the surf clam, Spisula solidissima, serotonin was reported to induce spawning when injected into the gonads. At nanomolar concentrations, it facilitates the fer- tilizability of oocyte by sperm, at micromolar concentration, it triggers the meiotic maturation of prophase 1-arrested oocytes, thus mimicking the effect of sperm. To further understand the role of serotonin in the gametogenic and spawning processes, we used both immunohistochemistry and high-pressure liquid chromatography linked with elec- trochemical detection to detect serotonin in the gonads of the surf clam. We found serotonin-containing varicose fi- bers covering the surface of the germinal epithelium in both sexes. The area occupied by the serotonergic innervation field encircling gonad acini varied according to the gonadal stages (active phase, ripe phase, partially spawned phase, spent phase). We also found large variations in the serotonin concentration between specimens during the gametogenic cycle. The serotonin concentration was correlated with go- nad growth: it decreased in the ripe phase in comparison with the previous phase, the active phase. We attribute the decrease to the increase of total gonad mass in this stage. In contrast, as spawning begins, the total gonad mass declines while the gonad serotonin concentration increases to a level similar to that found in active phase. The finding that prior to spawning, serotonin is present in the gonads within fibers exhibiting distinct varicosities suggests that it is implicated in spawning.
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mechanisms of activation of surf clam Spisula solidissima oocytes
Invertebrate Reproduction & Development, 1996Co-Authors: Francois DubeAbstract:Summary Surf clam (Spisula solidissima) oocytes, when shed, are at prophase I of meiotic maturation. Fertilization is the normal activation process leading to germinal vesicle breakdown (GVBD) and further steps of meiosis, followed by successive embryonic mitoses. We review here work suggesting that early rises in intracellular Ca2+ and pH (pHi) are normally associated with oocyte activation. Experimental evidence suggesting a pivotal role for the Ca2+ response and a more modest contribution of pHi are presented. The mechanisms of activation of Spisula oocytes by various artificial agents mimicking sperm are discussed in relation to their potential relevance to the physiological process of fertilization. We emphasize that serotonin-induced activation of Spisula oocytes is probably the best available model system to gain knowledge on the signal transducing systems stimulated by both serotonin or sperm. The potential physiological role of serotonin receptors present on oocytes is critically considered. Futu...
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optimization of fertilization parameters for rearing surf clams Spisula solidissima
Aquaculture, 1993Co-Authors: Gilles Clotteau, Francois DubeAbstract:Abstract Laboratory experiments were conducted to determine optimal conditions for “in vitro” fertilization of surf clam, Spisula solidissima , oocytes. Critical variables such as concentration of gametes, number of spermatozoa per oocyte, temperature, pH and salinity were investigated and assessed in relation to the proportion of monospermic and polyspermic fertilizations. The optimal concentrations of sperm and oocytes for monospermic fertilizations were 0.8–4×10 6 spermatozoa/ml and 5–30×10 3 oocytes/ml. Good percentages of monospermic fertilizations (80%) were thus obtained at sperm: oocyte ratios of 30:1 to 500:1 with optimal success (95% monospermic fertilizations) at a sperm: oocyte ratio of 50:1 to 100:1. Higher ratios induced increased polyspermic fertilizations while, at lower values, the oocytes remained unfertilized. Temperature, pH and salinity of natural sea water were varied separately from the standard values of 18°C, pH 8.0 and 24‰ and the success of fertilization was assessed. Temperatures ranging from 6 to 24°C had no detrimental effects upon fertilization and temperatures of 8 to 20°C appeared adequate for optimal fertilization. Fertilization rates, not affected at pH values ranging from 7.5 to 10.5, decreased rapidly at other values. Fertilization was not affected at salinities ranging from 20 to 35‰ and a salinity range of 23 to 30‰ was ideal for fertilization.
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studies on the chromosomes of the giant scallop placopecten magellanicus gmelin and the surf clam Spisula solidissima dillwyn
Cytologia, 1993Co-Authors: Jianhai Xiang, Richard R Desrosiers, Francois DubeAbstract:The karyotypes of two bivalve molluscs, the giant scallop Placopecten magellanicus and the surf clam Spisula solidissima, were examined in unfertilized eggs and embryos. In both bivalves, a haploid number of 19 and a diploid number of 38 were determined in well-spread metaphase chromosomes of meiotic and mitotic cells respectively. Moreover, karyological analysis of induced triploid embryos in Placopecten magellanicus indicates a chromosome number of 57 and thus corroborates the haploid and diploid counts. The chromosomes of Spisula solidissima are shorter than those of Placopecten magellanicus. Their sizes vary from 1.5 to 4.4μm in surf clam while those in giant scallop range from 3.3 to 8.5μm. Both bivalve species have submetacentric, subtelocentric and telocentric chromosomes but only Spisula solidissima has metacentric chromosomes.
Eric N Powell - One of the best experts on this subject based on the ideXlab platform.
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the effect of abundance changes on a management strategy evaluation for the atlantic surfclam Spisula solidissima using a spatially explicit vessel based fisheries model
Ocean & Coastal Management, 2019Co-Authors: Kelsey M Kuykendall, Eric N Powell, John M Klinck, Paula Moreno, Robert T LeafAbstract:Abstract Increased bottom water temperatures have caused a relocation and contraction of the range of the Atlantic surfclam, Spisula solidissima, in the Mid-Atlantic Bight (MAB). Consequences include declining stock abundance and landings per unit effort (LPUE) in southern portions of the range. A management strategy evaluation (MSE) assessed the potential of rotational closures to improve surfclam productivity and fishery viability under three levels of abundance. In simulations, fishing vessels harvest the stock under performance and quota constraints and captain behavioral proclivities. Management alternatives examined included the addition of area management to the current management plan using two closure location rules and three closure durations at two levels of incidental mortality. Simulations showed that area management increased stock abundance and fishery LPUE, particularly when surfclam abundance was low. Simulations suggest area management could help insulate the stock and commercial fishery from further shifts in range.
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biological reference points for atlantic surfclam Spisula solidissima in warming seas
Fisheries Research, 2018Co-Authors: Daniel Reneau Hennen, Daphne M Munroe, Roger Mann, Eric N PowellAbstract:Abstract Atlantic surfclam ( Spisula solidissima ) are a large, commercially important shellfish in the United States faced with several important management challenges. Compared to many harvested fish and shellfish, their life history is relatively unknown. They are undergoing contraction in the southern and inshore parts of their range, as well as expansion into deeper water. Atlantic surfclam are thermally sensitive, and the changes in their distribution track changes in maximum bottom temperature. Sessile species cannot emigrate and are limited to recruitment and mortality as mechanisms for redistribution in response to changing climate. Management of Atlantic surfclam should account for these challenges. We describe a simulation designed to calculate biological reference points that will work well for Atlantic surfclam relative to biological and fishery goals, over a range of life history parameters, assessment uncertainties, and increases in temperature. Simulations of the trade-off between somatic growth and mortality under increased temperature led to target fishing mortality rates higher than the status quo, but also to increased variability in yield. Results suggest that increasing temperature may adversely affect the Atlantic surfclam industry, which prefers stable catches to short term increases in yield, due to market limitations. The results of this analysis are specific to Atlantic surfclam, but the methods described here could be used to enhance management for other harvested species facing similar challenges.
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an overview of factors affecting distribution of the atlantic surfclam Spisula solidissima a continental shelf biomass dominant during a period of climate change
Journal of Shellfish Research, 2018Co-Authors: Eileen E Hofmann, Daphne M Munroe, Roger Mann, Eric N Powell, Diego A Narvaez, John M Klinck, Dale B Haidvogel, Xinzhong Zhang, Kelsey M KuykendallAbstract:ABSTRACT The Atlantic surfclam (Spisula solidissima) is a dominant member of the biological community of the Middle Atlantic Bight continental shelf and a commercially harvested species. Climate warming is affecting the biology and distribution of this species, which provides an opportunity to investigate the processes and conditions that are restructuring this fishery and the implications for ecological and socioeconomic systems. A Management Strategy Evaluation (MSE) developed for the surfclam fishery provides a mechanistic description of the surfclam's response to climate change and understanding of the cascade of effects initiated by changes in oceanographic conditions that ultimately appear as social and economic effects. This understanding in turn informs development of management policies for the resource. This overview considers the components of the surfclam MSE, relevant results, and implications for management and policy. The lessons learned from the surfclam MSE provide a basis for applying si...
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fishing and bottom water temperature as drivers of change in maximum shell length in atlantic surfclams Spisula solidissima
Estuarine Coastal and Shelf Science, 2016Co-Authors: Daphne M Munroe, Roger Mann, Eric N Powell, Diego A Narvaez, Eileen E Hofmann, D Hennen, L Jacobson, John M KlinckAbstract:Abstract Maximum shell length of Atlantic surfclams (Spisula solidissima) on the Middle Atlantic Bight (MAB) continental shelf, obtained from federal fishery survey data from 1982-present, has decreased by 15–20 mm. Two potential causes of this decreasing trend, fishery removal of large animals and stress due to warming bottom temperatures, were investigated using an individual-based model for post-settlement surfclams and a fifty-year hindcast of bottom water temperatures on the MAB. Simulations showed that fishing and/or warming bottom water temperature can cause decreases in maximum surfclam shell length (body size) equivalent to those observed in the fished stock. Independently, either localized fishing rates of 20% or sustained bottom temperatures that are 2 °C warmer than average conditions generate the observed decrease in maximum shell length. However, these independent conditions represent extremes and are not sustained in the MAB. The combined effects of fishing and warmer temperatures can generate simulated length decreases that are similar to observed decreases. Interannual variability in bottom water temperatures can also generate fluctuations in simulated shell length of up to 20 mm over a period of 10–15 years. If the change in maximum size is not genotypic, simulations also suggest that shell size composition of surfclam populations can recover if conditions change; however, that recovery could take a decade to become evident.
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long term dynamics in atlantic surfclam Spisula solidissima populations the role of bottom water temperature
Journal of Marine Systems, 2015Co-Authors: Diego A Narvaez, Daphne M Munroe, Roger Mann, Eric N Powell, Eileen E Hofmann, John M Klinck, Enrique N CurchitserAbstract:Abstract The potential linkages between warming bottom temperatures and increased mortality and/or reduced growth of the Atlantic surfclam (Spisula solidissima) were investigated using a model that simulates the temperature-dependent growth of the post-settlement population at specific locations on the Middle Atlantic Bight (MAB) continental shelf. External forcing for the individual-based surfclam model is provided by a 50-year simulation (1958–2007) of bottom water temperature obtained from an implementation of the Regional Ocean Modeling System for the northwestern Atlantic. The simulations show that in years with above average bottom water temperature (> 2 °C above average), surfclam assimilation rate is significantly reduced as a result of thermal stress, which leads to starvation mortality and an overall decline in the surfclam population of 2–9%, mainly in the inner shelf regions. Years with warmer bottom water temperatures were preceded by warm winters, which produced an earlier and longer summer season. These results suggest that the long-term observed decline in Atlantic surfclam populations on the MAB is a response to episodic warm years rather than a gradual warming trend in bottom water temperature, as previously suggested. These temperature driven population declines can persist for several years and have the largest effect on older and larger animals, which are the target of the commercial fishery.
James R Weinberg - One of the best experts on this subject based on the ideXlab platform.
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age structure recruitment and adult mortality in populations of the atlantic surfclam Spisula solidissima from 1978 to 1997
Marine Biology, 1999Co-Authors: James R WeinbergAbstract:The Atlantic surfclam, Spisula solidissima (Dillwyn, 1817), is a dominant member of the benthic community on the continental shelf from Georges Bank to North Carolina, USA. This bivalve has supported a major fishery, primarily off New Jersey and the Delmarva Peninsula, since the 1960s. Early papers documented that these populations were at historical lows in the mid-1970s owing to commercial harvesting and a hypoxic event off New Jersey. It was also shown that major recruitment took place off New Jersey in 1976 and off the Delmarva Peninsula in 1977. Because the size frequencies of surfclams from federal surveys do not show distinct year classes, there has been uncertainty about the number of year classes in these populations throughout the 1980s and 1990s. The present study describes changes in population age- and size-structure from 1978 to 1997 in federal waters (≥5.5 km from shore) of the USA. Given the 30 to 35 year life span of S. solidissima, these populations could be composed of many year classes. Yet, these populations were composed of only two to three year classes in 1978. Through annual recruitment, the number of year classes increased over time, and populations off New Jersey and the Delmarva Peninsula contained at least 19 year classes in 1997. This major change in population structure over time was not evident from examination of available size-frequency data, and could only be inferred from data on age-composition. Throughout the 1980s and 1990s, the surfclam fishery was supported by multiple year classes. The mean and variance of recruitment to the New Jersey region, as indicated by the abundance of 4-year-olds over time, was greater than that off Delmarva, particularly between 1980 and 1986. The instantaneous rate of adult mortality, which includes the effect of harvesting, was approximately 0.26 yr−1 in each region.
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density dependent growth in the atlantic surfclam Spisula solidissima off the coast of the delmarva peninsula usa
Marine Biology, 1998Co-Authors: James R WeinbergAbstract:Spisula solidissima (Dillwyn, 1817) is a large, suspension-feeding bivalve, whose range extends from Nova Scotia to South Carolina. This species is harvested commercially. Shell length and age data were collected for this species from 1980 to 1994 during surveys of population size and structure. These data were used to examine the relationship between the growth rate of S.␣solidissima and intraspecific density. The null hypothesis was that density (represented by number of individuals per tow) would have no effect on rate of growth. A negative relationship would support the alternative hypothesis, that intraspecific competition had taken place. This analysis focused on the surfclam population offshore from the Delmarva Peninsula, USA because: (1) a major recruitment event occurred in 1977, (2) clam fishermen had reported “stunted” surfclams in that area, (3) a wide range of local densities were available to examine, and (4) the existence of a closed area within the study area set up an interesting contrast with areas left open to harvesting. Maps of surfclam abundance across the Delmarva region demonstrate that areas of highest density have generally remained in the same location through time. The results suggested that intraspecific competition has been important in structuring this population. Based on data from 1980 to 1992, shell length was significantly reduced at high density, and a significant interaction between age and density was observed. Growth modeling indicated decreased asymptotic lengths and growth rates with increasing density. In nine out of ten pairwise randomization tests, fitted von Bertalanffy growth curves, representing different densities, were significantly different from each other. High densities of clams have persisted in the area that was closed to harvesting for 11 years (1980 to 1991). In 1994, length at age was significantly less in this closed area compared to that in the surrounding area. This effect was apparent in clams from 3 to 17 years of age, and most pronounced in the cohort that recruited to the Delmarva region in high numbers in 1977. Lower growth rates within the closed area have management implications for the optimal duration of closures.
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growth of the atlantic surfclam Spisula solidissima from georges bank to the delmarva peninsula usa
Marine Biology, 1996Co-Authors: James R Weinberg, Thomas E HelserAbstract:Age/shell length data for offshore surfclam, Spisula solidissima (Dillwyn, 1817), populations were used to estimate the parameters of the von Bertalanffy growth model by time period and region, from Georges Bank in the north to the Delmarva Peninsula in the south. Randomization tests were used to compare curves. We tested the a priori hypothesis that growth curves would change over time in the “south” (i.e., New Jersey and Delmarva) but remain constant in the “north” (i.e., Long Island and South New England). This hypothesis was proposed because surfclam population structure in the “south” had been altered by the hypoxic event of 1976, and possibly by intense, long-term commercial harvesting. Northern regions, unaffected by these factors, served as natural controls. Based on a comparison of data collected in 1980 with pooled data from 1989 and 1992, the hypothesis was supported. Both the growth coefficient (k) and maximum shell length (L ∞) declined between two time periods in the two “southern” regions, while during the same time interval, no change occurred in the two “northern” regions. Differences in growth between regions were often statistically significant. For example, compared with the “southern” regions, the growth coefficient on Georges Bank was larger, and those clams attained a smaller maximum length. In a comparison of adjacent regions from Delmarva to S. New England, k increased from south to north. This could imply faster growth in cooler water, as well as no relationship between growth and primary productivity. Alternatively, size-selective mortality, imposed by the commercial fishery, was discussed as a mechanism that might account for this unexpected pattern.