Shrimp Crangon Research Articles

Abundance, biomass, and productivity of invertebrate hyperbenthos in a temperate saltmarsh creek system

The hyperbenthos of two saltmarsh creeks at Bull Island, Dublin, Ireland was sampled to quantify its contribution to the larger trophic system of the lagoon. The brown shrimp Crangon crangon (L.) dominated in terms of both abundance and biomass. All species displayed marked seasonal and spatial variability which was reflected in the estimates for production, and especially in the vales for incremental change in biomass (δB) and mortality (M). The major contributions to production were by C. crangon and the shore crab Carcinus maenas, (L.) and to a lesser extent by Palaeomonetes varians (Leach) although the actual proportions varied according to the method used to calculate production. Total system production by the hyperbenthos in the creeks was around 20 kJ m−2 y−1. The contribution of hyperbenthic production was negligible in terms of overall system energy transfer to Dublin Bay, but it may play a crucial role in the saltmarsh creeks’ nursery function and trophic transfers.

Age estimation of brown shrimp Crangon crangon: comparison of two approaches applied to populations at the biogeographic edges

In this study, 2 methods for age estimation of Crangon crangon were compared: one based on total length, the other based on the number of segments in the antennules, as suggested by Tiews' findings (1954: Ber Deut Wiss Kommiss 13:235�269). Shrimps from populations near the species' geographic edges, from Valosen Estuary (Norway) in the north and the Minho Estuary (Portugal) in the south, were used. These showed great individual variability in shrimp size growth and in antennule segment number increment, due to the presence of fast- and slow-growing shrimps in the 2 populations, implying that shrimps of different ages may have similar sizes, as well as similar segment numbers. Additionally, the origin of shrimp population, sex, length and segment number, and water temperature were found to influence growth, both in the length- and the segment-increment models, often being interacting parameters. Both methods resulted in growth curves similar to a typical von Bertalanffy growth curve. The growth rate was higher for females than for males and positively related to temperature; the maximum size was also larger for females. In contrast, maximum segment number was larger for males than for females, as has also been found by Tiews (1954). The 2 models resulted in considerably different age estimates, par- ticularly for older shrimps (i.e. shrimps of larger size or with more antennule segments). The models also suggest site-specific growth rates. Any age estimation approach will therefore need to be validated for each population.

Vulnerability of artisanal fisheries to climate change in the Venice Lagoona

Within the context of global warming, the western coast of the northern Adriatic Sea can be regarded as an extremely vulnerable area. Owing to the local geographic features, this area has been described as the Venetian lacuna, where Mediterranean Sea climatic conditions are replaced by Atlantic Ocean ones, supporting the presence of glacial relicts, such as sprat Sprattus sprattus, flounder Platichthys flesus and brown shrimp Crangon crangon. Nektonic assemblage therefore represents a good candidate in terms of an early proxy for thermal regime alterations. It represents a dynamic component of the lagoon ecosystem, changing in space and time, actively moving through the entire system, and dynamically exchanging with the open sea. Here, the first signals of the change have been already detected, such as the presence of alien thermophilic species. Within this context, since the beginning of the century, sampling of the nektonic assemblage has been carried out, integrating them with landings data from the fish market. Vulnerabilities to thermal regime changes have been tested by (1) categorizing species according to the mean distribution area in terms of latitudinal range (over 45°, 30°-45° and below 30°), and (2) analysing both spatial and temporal variations within fishing grounds. Results indicated a high potential vulnerability of the artisanal fishery to climate change, as the commercial catch is entirely composed of species from cold (>45° N) and temperate (between 45° and 30° N) latitudes. At present no alien thermophilic species have been recorded within the lagoon, which is possibly a sign of good resilience of the assemblage. Finally, abundance of species from cold latitudes has decreased during the past decade. All of this has been discussed in the context of the mean annual temperature trend.

Maturity, size at age and predator–prey relationships of winter skate Leucoraja ocellata in the southern Gulf of St Lawrence: potentially an undescribed endemic facing extirpation

The goals of this study were to document the size and age structure, size at maturity, ovarian fecundity and diet of the endangered population of winter skate Leucoraja ocellata that resides in the southern Gulf of St Lawrence (SGSL). The maximum size observed for SGSL L. ocellata was 68 cm total length (LT ) but >99% of animals caught were <60 cm LT . Fifty per cent of male and female L. ocellata were fully mature at 40 and 42 cm LT , respectively, age c. 5 years. The oldest individual caught was age 11 years, but 98% of the 561 individuals examined were ≤age 8 years, indicating a short reproductive life span. Ovarian fecundity was low; no more than 29 ova >10 mm diameter were ever observed. At 40 cm LT , the diet changed from one dominated by shrimp Crangon septemspinosa and gammarid amphipods to one dominated by fishes (mainly sand lance Ammodytes spp. and rainbow smelt Osmerus mordax) and Atlantic rock crab Cancer irroratus. Sufficient differences were observed between SGSL L. ocellata and other populations in their size-at-maturity pattern and maximum size to propose the taxonomic re-evaluation of the population.

Spatial variation in growth rate of early juvenile European plaice Pleuronectes platessa

Patterns and causes of spatial variation in RNA-predicted growth rates in mid-August were examined in young-of-the-year European plaice Pleuronectes platessa (‘YOY plaice’) at 22 beaches along a 300 km stretch of coastline in west Scotland in 3 consecutive years. According to restricted maximum likelihood models, growth rates varied among beaches (25 km scale), but these spatial patterns were not consistent across years. We found no evidence for spatial variation in growth at the scale of subregions (50 km) or regions (100 km). Growth rate was positively correlated with total length, both within and among beaches and years. In general, YOY plaice in mid-August grew more slowly than estimated ad libitum laboratory rates. Average growth rates by beach and year were inversely related to intraspecific competitor densities, but not interspecific competitor densities (brown shrimp Crangon crangon) or 2 environmental productivity metrics (nearshore chlorophyll a concentration and lugworm Arenicola marina cast density). Physical beach characteristics also explained a significant source of spatial growth variation, with fish growing faster at beaches with larger tidal range and wave fetch. Therefore, the hypothesis of sub-maximum growth due to intraspecific competition (density-dependent growth) was supported, but additional, previously unexplored processes related to physical beach characteristics appear to have important influences on the spatial growth dynamics of YOY plaice.

Feeding ecology of the sand shrimp Crangon hakodatei Rathbun, 1902 (Decapoda: Crangonidae) in the East Sea of Korea

The feeding habits of the sand shrimp Crangon hakodatei in the East Sea (Korea) were investigated through analysis and comparison of the stomach contents of 602 individuals according to season, shrimp size class, and prey diversity. The diet of C. hakodatei consisted of 17 prey categories mainly comprising crustaceans, molluscs, polychaetes, nematodes, algae, and fishes, with crustaceans dominating the diet. Molluscs, nematodes, and fishes were also important prey, whilst other categories including polychaetes and algae comprised small percentages of the diet. For small C. hakodatei individuals (<10 mm carapace length [CL]), amphipods and mysids comprised more than 67% of the prey in both relative abundance and frequency of occurrence. Large individuals (>10 mm CL) tended to be more dependent on amphipods than mysids. Amphipods and mysids together constituted the dominant prey, accounting for more than 50% of the diet in terms of both percent occurrence and relative abundance. The abundance and occurrence of prey showed a seasonal variation, with amphipods and mysids being the predominant prey in autumn (45%), winter (30%), and spring (40%). Amphipods were the dominant prey with regard to season, size class, sex, and area.

Cloning and functional analysis of the ecdysteroid receptor complex in the opossum shrimp Neomysis integer (Leach, 1814)

In this paper, the non-target effects of tebufenozide were evaluated on the estuarine crustacean, the opposum shrimp Neomysis integer (Leach, 1814). Tebufenozide is a synthetic non-steroidal ecdysone agonist insecticide and regarded as potential endocrine-disrupting chemical (EDC). N. integer is the most used crustacean in ecotoxicological research in parallel to Daphnia sp. and has been proposed for the regulatory testing of potential EDCs in the US, Europe and Japan.Major results were: (i) cDNAs encoding the ecdysteroid receptor (EcR) and the retinoid-X-receptor (RXR), were cloned and sequenced, and subsequent molecular phylogenetic analysis (maximum likelihood and neighbor-joining) revealed that the amino acid sequence of the ligand binding domain (LBD) of N. integer EcR (NiEcR) clusters as an outgroup of the Crustacea, while NiRXR-LBD clusters in the Malacostracan clade (bootstrap percentage=75%). (ii) 3D-modeling of ligand binding to NiEcR-LBD demonstrated an incompatibility of the insecticide tebufenozide to fit into the NiEcR-ligand binding pocket. This was in great contrast to ponasterone A (PonA) that is the natural molting hormone in Crustacea and for which efficient docking was demonstrated. In addition, the heterodimerization of NiEcR-LBD with the common shrimp Crangon crangon (Linnaeus, 1758) RXR-LBD (CrcRXR-LBD) was also modeled in silico. (iii) With use of insect Hi5 cells, chimeric constructs of NiEcR-LBD and CrcRXR-LBD fused to either the yeast Gal4-DNA binding domain (DBD) or Gal4-activation domain (AD) were cloned into expression plasmids and co-transfected with a Gal4 reporter to quantify the protein–protein interactions of NiEcR-LBD with CrcRXR-LBD. Investigation of the ligand effect of PonA and tebufenozide revealed that only the presence of PonA could induce dimerization of this heterologous receptor complex. (iv) Finally, in an in vivo toxicity assay, N. integer juveniles were exposed to tebufenozide at a concentration of 100μg/L, and no effects against the molting process and nymphal development were scored.In conclusion, the in vitro cell reporter assay, based on NiEcR-LBD/CrcRXR-LBD heterodimerization in Hi5 cells and validated with the natural ecdysteroid hormone PonA, represents a useful tool for the screening of putative EDCs. As a test example for non-steroidal ecdysone agonist insecticides, tebufenozide had no negative effects on NiEcR/RXR receptor dimerization in vitro, nor on the molting process and nymphal development of N. integer at the tested concentration (100μg/L) in vivo.

Identification of Lipid Components in the Abdominal Muscle of Fall-CaughtCrangon crangonfrom a Coastal Area of the Baltic Sea

The main aim of this work was to determine the principal lipid classes and compositions of fatty acids (FFAs) in triacylglycerols (TAGs) and phospholipids in adult shrimps Crangon crangon from coastal areas of the Gulf of Gdansk (Baltic Sea, Poland). High performance liquid chromatography with a laser light-scattering detector (HPLC-LLSD) was used to separate the lipid classes. The FFA composition was determined with gas chromatography-mass spectrometry (GC-MS) and matrix-assisted laser-desorption time-of-flight mass spectrometry (MALDI-TOF-MS). The following lipid classes were separated using HPLC-LLSD: TAGs, FFAs, sterols (ST) and polar lipids (PL). The HPLC-LLSD analysis showed the dominance of sterols, which were missing from MALDI-TOF-MS, sterols made up 2.5 mg g-1 of the total lipids on the basis of this analysis. TAGs and FFAs were the next most abundant lipid classes, accounting 1.9 mg g-1 and 2.0 mg g-1 of the total lipids, respectively.

Long-term mean annual microphytobenthos chlorophyll a variation correlates with air temperature

Long-term interannual variations in the mean microphytobenthos chlorophyll a (chl a) of the Ems estuary were investigated. Concentrations in the 1990s were on average 1.5 times higher than during the period from 1976 to 1978, but a trend in chl a over the entire period (1976 to 1999) was not found. In agreement with findings from the late 1970s, the mean chl a concentrations over the post 1990 period correlated significantly with the station elevation related exposure time. Over the entire 1976 to 1999 study period, the estuary mean annual chl a concen- trations correlated strongly and significantly with the mean annual air temperature. Although the range of the variation in the mean annual air temperature of the studied years was only 7.5 to 10.2°C, it surprisingly corresponded with a ca. 2.5-fold variation in the mean annual microphyto- benthos chl a. In addition to chl a, mean monthly C:chl a ratios from 1976 to 1977 also correlated positively with changes in temperature. Microphytobenthos carbon biomass (chl a × (C:chl a)) may, therefore, respond even stronger to air temperature than chl a does. The correlations are most likely a combination of direct temperature effects on microphytobenthos and stronger, prob- ably complex, indirect temperature effects on the seasonal development and standing stock of young and adult grazers (bivalves) and their carnivores like the brown shrimp Crangon crangon.

Prey selectivity by juvenile Atlantic cod Gadus morhua in three coastal habitat types

Coastal habitats are heavily subjected to eutrophication and commercial fisheries, and such alterations can affect organism interaction strengths and potentially influence trophic dynamics. A key species inhabiting coastal environments in temperate waters is the Atlantic cod Gadus morhua, which utilises coastal areas for food and shelter. We used an experimental mechanistic approach to assay prey selectivity by juvenile cod when foraging on grass shrimp Palaemon elegans and brown shrimp Crangon crangon, under light and dark conditions, in 3 of the most abundant habitat types in temperate coastal environments-sand, eelgrass (artificial vegetation mimicking Zostera marina), and bladderwrack Fucus vesiculosus. Using functional response relationships from single-prey experiments, we calculated the energetically best foraging strategy for cod in the 3 habitats, i.e. feeding selectively on either of the shrimp species or on a combination of both. These predictions were tested in experiments where the cod predator was offered both prey species. Cod selected both prey species in accordance with our predictions in eelgrass and in bladderwrack under light conditions, but a lower than predicted consumption of grass shrimp was found in sand and in bladderwrack under dark conditions. Cod decreasingly selected grass shrimp with increasing habitat complexity, i.e. the highest selectivity was in sand and the lowest selectivity was in bladderwrack. As the 2 shrimp species have different trophic roles, cod selective predation may have effects on lower trophic levels. We provide a quantitative prediction of cod selective predation in habitat types that undergo degradation, and suggest that such predation can influence the trophic consequences from environmental change. (Less)

Absence of Ca2+-induced mitochondrial permeability transition but presence of bongkrekate-sensitive nucleotide exchange in C. crangon and P. serratus

Mitochondria from the embryos of brine shrimp (Artemia franciscana) do not undergo Ca2+-induced permeability transition in the presence of a profound Ca2+ uptake capacity. Furthermore, this crustacean is the only organism known to exhibit bongkrekate-insensitive mitochondrial adenine nucleotide exchange, prompting the conjecture that refractoriness to bongkrekate and absence of Ca2+-induced permeability transition are somehow related phenomena. Here we report that mitochondria isolated from two other crustaceans, brown shrimp (Crangon crangon) and common prawn (Palaemon serratus) exhibited bongkrekate-sensitive mitochondrial adenine nucleotide transport, but lacked a Ca2+-induced permeability transition. Ca2+ uptake capacity was robust in the absence of adenine nucleotides in both crustaceans, unaffected by either bongkrekate or cyclosporin A. Transmission electron microscopy images of Ca2+-loaded mitochondria showed needle-like formations of electron-dense material strikingly similar to those observed in mitochondria from the hepatopancreas of blue crab (Callinectes sapidus) and the embryos of Artemia franciscana. Alignment analysis of the partial coding sequences of the adenine nucleotide translocase (ANT) expressed in Crangon crangon and Palaemon serratus versus the complete sequence expressed in Artemia franciscana reappraised the possibility of the 208-214 amino acid region for conferring sensitivity to bongkrekate. However, our findings suggest that the ability to undergo Ca2+-induced mitochondrial permeability transition and the sensitivity of adenine nucleotide translocase to bongkrekate are not necessarily related phenomena.

Brown shrimp abundance in northwest European coastal waters from 1970 to 2010 and potential causes for contrasting trends

We investigated long-term trends in abundance of the NE Atlantic population of brown shrimp Crangon crangon based on data collected in annual autumn surveys carried out along the coasts of the North Sea in The Netherlands, Germany and Denmark. Surveys covered some estuaries and intertidal areas, as well as shrimp fishery grounds. The 40 yr period showed distinct regional trend differences, but only in estuarine areas: the Western Dutch Wadden Sea (increase), the Eastern Dutch Wadden Sea (decrease) and the Oosterschelde (decrease). The decrease in the Oosterschelde coincided with the closure of this sea arm from fresh water inflow. Increases in the Western and Eastern Dutch Wadden Sea were driven primarily by increased abundance of small shrimp, suggesting that the causative mechanism likely affected younger shrimp. Trends in potential causes were examined in the 2 regions. Of all abiotic factors investigated, only water clarity decreased significantly in the west but not in the east. Mean abundance of potential predators (cod, whiting, shore crab and swimming crab) was used as an indicator of predation pressure. Shore crab showed similar increases in both areas. In the other 3 species, predator abundance in the east was generally initially higher than in the west, but declined towards similar densities in recent years. Shrimp fishing pressure in NW Europe has increased strongly since the 1990s. Preliminary, spatially resolved logbook data show that shrimp landings from the Western Wadden Sea followed this increase, but those from the Eastern Wadden Sea remained stable. Apart from mechanisms related to fishing pressure and water clarity, a candidate cause of differences in abundance may be differences in food condition or competition for food. Generally biomass of benthos, a primary food for shrimp, increased in the west and remained stable in the east. However, because brown shrimp are omnivorous, quantification of changing fractions of food available to them is difficult

Composition of fatty acids and sterols composition in brown shrimp Crangon crangon and herring Clupea harengus membras from the Baltic Sea

Abstract The composition and the content of lipids, fatty acids and sterols during spawning (spring) in different tissues of herring Clupea harengus membras were compared with quantities of lipid compounds in abdomen muscle of brown shrimp Crangon crangon. The largest quantity of fatty acids in lipids (93.7%), was observed in fish muscle. The liver was characterized by a higher content and variety of sterols (about 4.6 times more than in fish muscle), and in fish sperm, additional fatty acids were identified and the highest amount of EPA and DHA (22% and 34% of fatty acids, respectively) was recorded. The brown shrimp, despite its small size, contained significantly more lipids than the Baltic herring per g of tissues. Fatty acids were at the same level (83% of the total lipids in shrimp muscle and 93.7% in fish muscle), but the amount of sterols was significantly higher in the muscle of shrimp (5.50 ±0.31 mg g−1, 17% of total sterols, n=10) than in fish muscle (1.33 ±0.04 mg g−1, 6.3% of total lipids, n=6). And thus, shrimp is a good source of food for higher trophic levels, and in consequence — a good source of PUFAs for humans. With these results we prove that shrimp and herring play an important role in the supply of EFAs, which has great pharmaceutical and medical benefits.

Catalytic properties and polymorphism of serine endopeptidases from the midgut gland of the brown shrimp Crangon crangon (Decapoda, Caridea)

The brown shrimp Crangon crangon is a key species in the coastal areas of the North Sea. It constitutes a significant food source for fishes. Simultaneously, it is an important predator on a wide range of invertebrates. C. crangon shows a variety of digestive enzymes that allow to utilizing a wide range of food items. The initial step of alimentary protein digestion, that is the degradation into peptides, is facilitated by set of endopeptidases which are expressed by the midgut gland. In crustaceans, these endopeptidases are often dominated by serine proteinases. C. crangon, however, predominantly express cysteine proteinases, while only some specimens show a highly variable pattern of serine proteinases. The composition of these serine endopeptidases was investigated using liquid chromatography, substrate gel electrophoresis and inhibitor assays. Distinctly elevated activities were present only in about 10% of the samples. When activity was detected, two peaks, one with tryptic activity and the other one with chymotryptic activity, could be separated by anionic exchange chromatography. Moreover, specimens with elevated tryptic activities often showed highly polymorphic patterns of endopeptidases after electrophoretic separation. Overall, 30 different bands of endopeptidases were identified. There was no similarity between animals from the same sampling sites, neither between animals of similar size, weight or nutritive state. The polymorphism of proteinase from the midgut gland seems to reflect the high adaptive potential of this species to variable trophic conditions in a continuously changing environment.

A new method to determine in situ growth rates of decapod shrimp: a case study with brown shrimp Crangon crangon

Shrimps are economically and ecologically very important, yet a lack of ageing techniques and hence unknown growth rates often impairs analytical assessments and management. A new method for the determination of in situ growth rates of shrimps is presented, based on dry weight condition. Since this index oscillates from low values directly after moult to highest values prior to moult in constantly feeding shrimp, the lowest observed pre-moult condition followed by a moult was introduced as a reference value to separate growing and starving individuals in field data. Experiments with Crangon crangon confirmed that (1) post-moult condition varies in a narrow physiologically optimal range, regardless of recent growth increments, and (2) dry weight condition prior to moult is closely related to the subsequent length increment. The method was applied to estimate growth increments from in situ dry weight condition data of C. crangon. The new method can easily be applied to other related species, since the required data can be obtained from very simple short-term experiments.

Molecular detection of plaice remains in the stomachs of potential predators on a flatfish nursery ground

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 444:223-238 (2012) - DOI: https://doi.org/10.3354/meps09439 Molecular detection of plaice remains in the ­stomachs of potential predators on a flatfish ­nursery ground Aitor Albaina1,3,*, Martin I. Taylor1, Clive J. Fox2 1Molecular Ecology and Fisheries Genetics Laboratory, School of Biological Sciences, ECW Building, Bangor University, Bangor LL57 2UW, UK 2Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK 3Present address: Laboratory of Genetics, Department of Genetics, Physical Anthropology & Animal Physiology, University of the Basque Country, Leioa 48940, Spain *Email: aitoralbaina@hotmail.com ABSTRACT: Stomach contents of potential predators from a flatfish nursery ground on the Scottish west coast were examined visually and probed using a TaqMan real-time PCR based assay designed to detect plaice Pleuronectes platessa DNA. Stomachs from 1137 brown shrimp Crangon crangon, along with a lesser number of shore crab Carcinus maenas, grey gurnard Eutrigla gurnardus and Gobiidae were analysed. Overall 45% of shrimp tested positive for plaice DNA, a proportion considerably higher than in stomachs containing visually identifiable flatfish remains. When scaled to the population level, predation by shrimp generated an estimated mortality of ~9% d–1, which compares with a decline in plaice abundance from mid-May to mid-June of ~4.4% d−1. The discrepancy between mortality estimates based on molecular and catch-curve analysis might be due to sampling being conducted at low water between dusk and dawn, which would concentrate predators and prey at times coincident with peaks of shrimp feeding. In addition, the sensitivity of the TaqMan assay could have led to some over-estimation because non-fatal interactions may also have been detected, e.g. shrimp are known to nibble the fins of flatfish, that might result in a positive TaqMan result but not necessarily in mortality for the fish. The percentage of shrimp testing positive for presence of plaice DNA in their stomachs was also related to plaice density in a positive, linear manner. For less abundant predators, stomachs of 6% of shore crabs, 40% of gurnards and 11% of large gobies also tested positive. KEY WORDS: Stomach contents · TaqMan real-time PCR assay · Pleuronectes platessa · Crangon crangon · Carcinus maenas · Predator−prey interactions · Nursery ground · Tralee Beach Full text in pdf format PreviousNextCite this article as: Albaina A, Taylor MI, Fox CJ (2012) Molecular detection of plaice remains in the ­stomachs of potential predators on a flatfish ­nursery ground. Mar Ecol Prog Ser 444:223-238. https://doi.org/10.3354/meps09439 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 444. Online publication date: January 10, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Spatial and Temporal Diet Patterns of Subadult and Small Adult Striped Bass in Massachusetts Estuaries: Data, a Synthesis, and Trends across Scales

AbstractSubadult and small adult (375–475 mm total length) striped bass Morone saxatilis are abundant and represent an important component of the recovered U.S. Atlantic coast stocks. However, little is known about these large aggregations of striped bass during their annual foraging migrations to New England. A quantitative understanding of trends in the diets of subadult and small adult migrants is critical to research and management. Because of the complexity of the Massachusetts coast, we were able to compare diets at multiple spatial, temporal, and taxonomic scales and evaluate which of these provided the greatest insights into the foraging patterns of this size of fish. Specifically, during spring through autumn, we quantified the diets of 797 migratory striped bass collected from 13 Massachusetts estuaries distributed among three geographic regions in two biogeographic provinces. Our data provided three useful results. First, subadult and young adult striped bass ate a season‐specific mixture of fish and invertebrates. For example, more juvenile Atlantic herring Clupea harengus were eaten in spring than in summer or autumn, more juvenile Atlantic menhaden Brevoortia tyrannus were eaten in autumn than in spring or summer, amphipods were eaten primarily in the southern biogeographic province, and shrimp Crangon sp. were eaten in all locations and seasons. Second, examining diets by season was essential because of the temporal variability in striped bass prey. Grouping prey by fish and invertebrates revealed the potential for predictable differences in growth across geographic locations and seasons, based on the output from simple bioenergetics simulations. Third, of the three spatial scales examined, region provided the most quantitative and interpretable ecological trends. Our results demonstrate the utility of comparing multiple scales to evaluate the best way to depict diet trends in a migrating predator that seasonally uses different geographic locations.Received March 3, 2010; accepted May 3, 2011

Seasonal and interannual variations in size, biomass and chemical composition of the eggs of North Sea shrimp, Crangon crangon (Decapoda: Caridea)

In the shrimp Crangon crangon, an important fishery resource and key species in the southern North Sea, we studied temporal variations in size, biomass (dry weight, W) and chemical composition (C, N, protein and lipid) of eggs in an initial embryonic stage. Data from 2 years, 1996 and 2009, consistently revealed that egg size and biomass varied seasonally, with maxima at the beginning of the reproductive season (January), decreasing values throughout spring, minima in June–July, and a slight increase thereafter. This cyclic pattern explains why “Winter eggs” are on average larger and heavier than “summer eggs”. Using a modelling approach, we estimated the duration of oogenesis in relation to seasonally changing seawater temperatures. According to an additive model of multiple explanatory variables, the C content per newly laid egg showed in both years a highly significant negative relationship with day length (r² = 0.38 and 0.40, respectively; P < 0.0001), a weak positive relationship with temperature (r² = 0.08 and 0.09; P < 0.05), and a weak negative relationship with phytoplankton biomass (r² = 0.11 and 0.12; P < 0.05) at the estimated time of beginning oogenesis. Phenotypic plasticity in initial egg size and biomass is interpreted as an adaptive reproductive trait that has evolved in regions with strong seasonality in plankton production and periods of larval food limitation. In contrast to biomass per egg, the percentage chemical composition remained similar throughout the reproductive period. Both the absolute and percentage values also showed significant interannual variations, which caution against generalizations based on short-term studies of reproductive traits of C. crangon and other species of shrimp.

Effect of cadmium and glutathione on malic enzyme activity in brown shrimps (Crangon crangon) from the Gulf of Gdańsk

The high level of cadmium in the abdominal muscle of the brown shrimp Crangon crangon is due to the serious pollution of the water in the Gulf of Gdańsk. The inhibition of malic enzyme (ME) activity by cadmium, and in consequence the reduced formation of NADPH, could interfere with cellular mechanisms for detoxifying the organism and reducing oxidative stress. The reduced glutathione (GSH) concentration in the abdominal muscle of C. crangon was calculated to be 5.8mM. The objective of this study was to evaluate the part played by GSH in the effect of cadmium on the activity of NADP-dependent malic enzyme from abdominal muscles of brown shrimps. This enzyme is activated by certain divalent cations (Mg, Mn). The results demonstrate that cadmium inhibits ME activity from shrimp muscle, and that GSH and albumin can reduce this cadmium-inhibited NADP-dependent malic enzyme activity.

Trophic Ecology of Summer Flounder in Lower Chesapeake Bay Inferred from Stomach Content and Stable Isotope Analyses

AbstractTrophic studies of summer flounder Paralichthys dentatus have relied on traditional stomach content analyses to infer contributions of prey to species productivity. We applied both stable isotope and stomach content analyses to identify prey groups that are responsible for summer flounder productivity in lower Chesapeake Bay and to explore ontogenetic patterns in prey utilization. Summer flounder (total length = 138–682 mm; age = 0–11 years) were collected for stomach and tissue samples (liver, blood, and muscle) during spring–summer (May–July) and fall (November) of 2006 and 2007. Commonly consumed crustacean and fish prey species were also collected: mysid shrimp Neomysis americana, sevenspine bay shrimp Crangon septemspinosa, mantis shrimp Squilla empusa, bay anchovy Anchoa mitchilli, spotted hake Urophycis regia, and juvenile sciaenids. Analysis of the nitrogen stable isotope ratio (δ15N; ratio of 15N to 14N relative to a standard) revealed that crustaceans comprised the majority (72–100% on average) of the summer flounder diet except in spring 2006, when fish consumption was more dominant. Analysis of corresponding stomach contents indicated a lower contribution of crustacean prey. Based on isotopes, summer flounder tended to occupy the same trophic level as the prey fishes. The δ15N in all tissues exhibited a positive trend with body length, indicating that larger summer flounder fed at approximately one trophic level above smaller individuals; the positive trend also corresponded with increasing proportions of fish in summer flounder stomachs. Our stable isotope analysis indicates that growth and production of summer flounder in lower Chesapeake Bay are highly dependent on assimilation of mysid shrimp, sevenspine bay shrimp, and mantis shrimp—more so than previously expected based on stomach content research.