Juvenile Summer Flounder Paralichthys Dentatus Research Articles

Foraging by estuarine juveniles of two paralichthyid flounders: experimental analyses of the effects of light level, turbidity, and prey type

Juvenile summer flounder Paralichthys dentatus and southern flounder P. lethostigma inhabit turbid salt marsh estuaries. Predation rates by juveniles (50-90 mm) were examined at 5 daytime light levels (6 × 1011 to 2 × 1014 quanta s-1 cm-2) and in darkness and 4 turbidity levels (clear [≤1], 11, 20, and 40 NTU) at an intermediate light level. Both species fed equally well on benthopelagic mysid shrimp and benthic spionid polychaetes at all daytime light levels tested. However, predation on mysids was significantly reduced in the dark. Consumption of polychaetes was not reduced in the dark by either species, illustrating the effectiveness of non-visual foraging methods on benthic prey. Turbidity levels tested did not affect predation on either prey type by either flounder species. Locomotor behavior was examined at the same turbidity levels. P. lethostigma spent more time swimming in the water column than P. dentatus in lower turbidity (clear-20 NTU), and both species reduced swimming at 40 NTU. It appears that both species primarily use a benthic-oriented ambush foraging strategy under high turbidity conditions. This is a particularly pronounced switch in foraging style for P. lethostigma. Estuarine turbidity is increasing due to the impacts of climate change. When turbidity is elevated enough to eliminate light sufficient for visual feeding on mysids (between darkness and the lowest light level tested), feeding on this motile prey is negatively impacted for both species. Turbidity can thus alter foraging modes and types of prey consumed, affecting nursery habitat quality and the prey base supporting these young fishes.

Comparison of Thermohaline Optima for Juveniles of Two Sympatric Paralichthyid Flounders: Ecophysiological Evaluation of Estuarine Nursery Quality

Juvenile summer flounder Paralichthys dentatus and southern flounder Paralichthys lethostigma exhibit ontogenetic segregation during spring and summer in southeastern USA estuaries, with summer flounder remaining primarily in polyhaline regions and southern flounder migrating to oligohaline habitat. To determine physicochemical conditions contributing to optimal nursery ground function for each species, growth rates, feeding rates, and gross growth efficiencies were examined in common-garden experiments at spring and summer thermohaline regimes. Experiments were conducted on young-of-the-year (45–100 mm total length; 0.9–8.9 g) summer flounder (15–25 °C, 10–30‰) and southern flounder (15–30 °C, 0–30‰) from North Carolina, and juvenile summer flounder from Delaware (15–25 °C, 30‰ only). Over the 15–25 °C and 10–30‰ conditions common to both species, means of all dependent variables were greater in summer flounder than southern flounder. Summer flounder grew best at 21–23 °C and 21–28‰. Low salinity (0–10‰) was physiologically suboptimal, especially at high (25 °C) summer temperatures. There was a significant direct effect of location (North Carolina vs Delaware) on growth efficiency of juvenile summer flounder, but not on growth rate, feeding rate, or linear growth rate. Growth potential of southern flounder was maximum at 25–26 °C and 10–30‰, and growth efficiency was highest at mesohaline salinities; yet growth was maintained at moderate levels over a broad range of oligohaline conditions, including ≤ 10‰, even at 30 °C. Differences in thermohaline conditions that affect growth potential illustrate spatiotemporal patterns and dynamics of optimal nursery potential for these two paralichthyid flounders.

Temporal dynamics of condition for estuarine fishes in their nursery habitats

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 557:207-219 (2016) - DOI: https://doi.org/10.3354/meps11858 Temporal dynamics of condition for estuarine fishes in their nursery habitats R. W. Schloesser1,2,*, M. C. Fabrizio1 1Virginia Institute of Marine Science, College of William & Mary, PO Box 1346, Gloucester Point, Virginia 23062, USA 2Present address: Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, Florida 34236, USA *Corresponding author: rschloesser@mote.org ABSTRACT: The condition of individuals in a year class may contribute to recruitment variability due to differential survival of poor- and well-conditioned fish, but the temporal dynamics of juvenile fish condition are poorly understood. We examined inter- and intra-annual dynamics of condition for juveniles of 3 species collected from estuarine nursery areas of Chesapeake Bay from November 2010 to June 2014. We describe temporal patterns in length-based indices, the hepatosomatic index (HSI), and relative subdermal lipid estimates for juvenile summer flounder Paralichthys dentatus (n = 1771), Atlantic croaker Micropogonias undulatus (n = 3911), and striped bass Morone saxatilis (n = 874). Multiple indices provided a more complete understanding of energy-storage strategies for juveniles because temporal patterns among condition indices were not congruent for a given species. Most juvenile summer flounder and Atlantic croaker migrate from Chesapeake Bay in the fall, and both species exhibited increases in subdermal lipids in the time period prior to migration. For all species, individuals that remained in the estuary during winter exhibited high HSI values, indicating a common energy-storage strategy during winter. Mean condition of juveniles varied among year classes, but differences were inconsistent among indices, suggesting that energy was differentially stored among tissues for these year classes. Density-dependent effects contributed to variation in mean condition for summer flounder and striped bass. Our understanding of recruitment variability may be improved by assessing annual differences in mean condition as revealed by multiple indices. KEY WORDS: Fulton’s K · Hepatosomatic index · Subdermal lipid · Fish fatmeter · Juveniles · Bioenergetics · Recruitment Full text in pdf format PreviousNextCite this article as: Schloesser RW, Fabrizio MC (2016) Temporal dynamics of condition for estuarine fishes in their nursery habitats. Mar Ecol Prog Ser 557:207-219. https://doi.org/10.3354/meps11858 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 557. Online publication date: September 28, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Evaluating the effects of diel-cycling hypoxia and pH on growth and survival of juvenile summer flounder Paralichthys dentatus

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 556:223-235 (2016) - DOI: https://doi.org/10.3354/meps11817 Evaluating the effects of diel-cycling hypoxia and pH on growth and survival of juvenile summer flounder Paralichthys dentatus Max I. Davidson1,*, Timothy E. Targett1, Paul A. Grecay2 1University of Delaware, College of Earth, Ocean and Environment, School of Marine Science and Policy, Lewes, DE 19958, USA 2Salisbury University, Department of Biological Sciences, Salisbury, MD 21801, USA *Corresponding author: maxiandavidson@gmail.com ABSTRACT: Effects of diel-cycling dissolved oxygen (DO) and pH on young-of-the-year summer flounder Paralichthys dentatus were examined in laboratory experiments. Flounder were exposed to 2 cycling DO levels (extreme = 1-11 mg O2 l-1; moderate = 3-9 mg O2 l-1), 2 cycling pH levels (extreme = 6.8-8.1; moderate = 7.2-7.8), and static normoxia (7.5 mg O2 l-1) and pH (7.5) in a fully crossed 3 × 3 experimental design for 20 d. Cycling conditions reflected summertime DO and pH fluctuations in flounder nursery habitat. Experiments were conducted over 3 partial factorial trials. Growth was significantly reduced in fish exposed to the most extreme diel-cycling DO, across all pH treatments, with no consistent growth reduction in other treatments. Cycling treatments with mean daily low pH (~6.87) and high pCO2 (~10000 µatm) had neither an independent nor interactive effect, with hypoxia, on growth. Flounder exhibited growth rate recovery. Following initial growth reduction when exposed to extreme diel-cycling hypoxia and pH over Days 1-10, growth increased ~2-fold under static DO (7.5 mg O2 l-1) and pH (7.5) conditions over the following 10 d. Flounder did not exhibit growth rate acclimation, defined as increased growth during prolonged exposure, under extreme diel-cycling DO and pH for 20 d. Flounder experienced mortality (>90% of individuals) after 2-3 wk exposure to extreme diel-cycling DO and pH. These experimental results demonstrate that extreme diel-cycling DO and pH can significantly impact summer flounder growth and survival and that the growth rate reduction is driven by DO. KEY WORDS: Diel-cycling hypoxia · Diel-cycling pH · Eutrophication · Flounder · Hypoxia · Ocean acidification Full text in pdf format PreviousNextCite this article as: Davidson MI, Targett TE, Grecay PA (2016) Evaluating the effects of diel-cycling hypoxia and pH on growth and survival of juvenile summer flounder Paralichthys dentatus. Mar Ecol Prog Ser 556:223-235. https://doi.org/10.3354/meps11817 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 556. Online publication date: September 08, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Relationships among Proximate Components and Energy Density of Juvenile Atlantic Estuarine Fishes

AbstractInformation on the energy density of juvenile fishes is needed to inform food web and bioenergetic models. Several approaches may be used to estimate energy density, and although these approaches are expected to yield similar estimates, the accuracy of such estimates has not been assessed. Estuarine fishes have unique life history strategies that influence the water, protein, lipid, and ash composition of their tissues. Because proximate components vary among species, the preferred approaches for estimating energy density from these components may also differ. We investigated the suitability of five approaches to estimate energy density measured by bomb calorimetry from water content for juvenile Summer Flounder Paralichthys dentatus, Striped Bass Morone saxatilis, and Atlantic Croaker Micropogonias undulatus. Approaches were based on the following: (1) relationships between water and percent composition, (2) relationships between water and the mass of proximate components, (3) water content alone (by percentage and by mass), (4) percent water and fish mass, and (5) published relationships between energy density and percent dry weight. The mean predicted energy densities from alternative approaches were generally within 10% of the mean energy densities measured by bomb calorimetry (4.21 kJ/g to 4.94 kJ/g). For Summer Flounder and Atlantic Croakers, regressions based on the percent water from whole fish provided estimates of energy density closest to those from bomb calorimetry, and including fish mass improved the accuracy of energy density estimates for Striped Bass. Energy density calculated from percent composition overestimated measured energy density, even with conservative lipid‐to‐energy conversion factors; this was most pronounced for individuals with energy densities less than 5 kJ/g. Because lipid‐to‐energy conversion factors may not be temporally stable or spatially invariant, further research is needed on the energy content of lipid classes in fishes. The types of lipids used for energy storage likely vary among life stages and species, and extrapolating approaches to different size‐classes or species groups may bias estimates of energy content.

Characterizing the escape response of juvenile summer flounder Paralichthys dentatus to diel‐cycling hypoxia

Swimming speed, angular correlation and expected displacement were measured in juvenile summer flounder Paralichthys dentatus acclimated to either oxygen saturation (c. 7.8 mg O(2) l(-1); saturation-acclimated fish) or diel-cycling hypoxia (cycling between 11.0 and 2.0 mg O(2) l(-1)) for 10 days and subsequently exposed to more severe diel-cycling hypoxia (cycling between 7.0 and 0.4 mg O(2) l(-1)). Saturation-acclimated P. dentatus exhibited an active response to declining dissolved oxygen (DO) by increasing swimming speed, angular correlation and expected displacement to peak levels at 1.4 mg O(2) l(-1) that were 3.5, 5.5 and 4.2 fold, respectively, greater than those at DO saturation. Diel-cycling hypoxia-acclimated P. dentatus also exhibited an active response to declining DO, although it was relatively less pronounced. Diel-cycling hypoxia-acclimated P. dentatus swimming speed, however, still doubled as DO decreased from 7.0 to 2.8 mg O(2) l(-1). Diel-cycling hypoxia-acclimated P. dentatus did not recover as well from low DO exposure as did saturation-acclimated fish. This was reflected in their relatively more random swimming (low angular correlation between successive moves) and poor maintenance of rank order between individuals during the recovery phase. Even saturation-acclimated P. dentatus did not resume swimming at speeds observed at saturation until DO was 4.2 mg O(2) l(-1). Paralichthys dentatus were very sensitive to decreasing DO, even at DO levels that were not lethal or growth limiting. This sensitivity and their poor recovery may preclude juvenile P. dentatus from using highly productive nursery habitats affected by diel-cycling hypoxia.

Reovirus-like Infection of Cultured Summer Flounder Paralichthys dentatus

Examination via light and electron microscopy of juvenile summer flounder Paralichthys dentatus experiencing a subacute to chronic mortality revealed severe necrotizing hepatitis characterized by necrotic multinucleated giant cells (syncytia). The cytoplasms of syncytia contained paracrystalline arrays of reovirus-like particles, strongly suggesting that the epidemic was caused by the virus. This is the first report of a putative viral infection in summer flounder.

Demonstration and implications of habitat‐specific chemical signatures in otoliths of juvenile summer flounder (Paralichthys dentatus Linnaeus) in North Carolina

The objective of this pilot study was to determine if otolith signatures of juvenile summer flounder Paralichthys dentatus (Linnaeus) were differentiable between beach and marsh habitat types within two North Carolina (NC), U.S.A., estuarine systems. Elemental signatures were differentiable between habitats in both systems, and in one system at smaller spatial scales (<5 km) than have been reported for any estuarine species using otolith microchemistry. These results indicate the potential for using summer flounder otolith elemental analysis to assess the nursery role of habitats within NC estuaries.

Ecophysiological responses of juvenile summer and winter flounder to hypoxia: experimental and modeling analyses of effects on estuarine nursery quality

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 325:255-266 (2006) - doi:10.3354/meps325255 Ecophysiological responses of juvenile summer and winter flounder to hypoxia: experimental and modeling analyses of effects on estuarine nursery quality Kevin L. Stierhoff1,2, Timothy E. Targett1,*, KerriLynn Miller1,3 1University of Delaware, College of Marine and Earth Studies, Lewes, Delaware 19958, USA 2Present address: NOAA Fisheries, Southwest Fisheries Science Center, Fisheries Ecology Division, 110 Shaffer Rd, Santa Cruz, California 95060, USA 3Present address: Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328 Duke University, Levine Science Research Center, Durham, North Carolina 27708, USA *Corresponding author. Email: ttargett@udel.edu ABSTRACT: Growth and feeding rates were measured in juvenile summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus exposed to sub-lethal hypoxia (low dissolved oxygen, DO) over a range of temperatures, to determine its potential effects on nursery habitat quality for these 2 estuary-dependent flatfishes. Growth rates of both species were generally reduced as DO decreased, particularly at DO levels of 50 to 70% air saturation, and as temperature increased. Summer flounder were more tolerant of low DO than were winter flounder at both 20 and 25°C. At these temperatures, summer flounder growth was reduced by ~25% (compared to growth at normoxia [7.0 mg O2 l–1]) at 3.5 mg O2 l–1 and by 50 to 60% at 2.0 mg O2 l–1. In contrast, growth of winter flounder at 20°C was reduced by ~50% at both 3.5 and 5.0 mg O2 l–1, and growth was zero at 2.0 mg O2 l–1. At 25°C, winter flounder grew poorly in all DO treatments and lost weight at 2.0 mg O2 l–1. Summer flounder were also tested at 30°C. Growth was significantly reduced even at 5.0 mg O2 l–1, and was reduced by ~90% at 2.0 mg O2 l–1. A significant relationship between feeding rate and growth suggested reduced consumption to be a major cause of growth limitation under hypoxia. There was no evidence of growth acclimation for either species after 7 to 14 d exposure to hypoxia. The effect of hypoxia on growth of summer flounder was reduced at lower salinity (15 vs. 25‰) and was unaffected by the presence of a sand substrate. Similarity between modeled growth under hypoxic conditions, based on our laboratory results, and observed growth of summer flounder in a hypoxic estuarine tributary suggests growth limitation in the wild. These laboratory and field results demonstrate that even moderate hypoxia can adversely affect growth rates, and thus the quality of estuarine nursery habitats for juvenile flatfishes. KEY WORDS: Hypoxia · Summer flounder · Winter flounder · Flatfish · Essential fish habitat · Nursery habitat · Growth limitation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 325. Online publication date: November 07, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Estuarine habitat evaluation measured by growth of juvenile summer flounder Paralichthys dentatus in a North Carolina estuary

Habitat quality and fish success, in terms of growth and mortality, are presumably correlated, and abiotic conditions are likely to be a major component in determining habitat quality. We assessed habitat quality in terms of fish growth and mortality using basic abiotic factors as the major variables. Juvenile summer flounder Paralichthys dentatus (42 to 59 mm total length) were caged at 5 sites in and around Masonboro Island, North Carolina, USA, during June and July 1999. Temperature, dissolved oxygen, salinity and pH were recorded every 30 min at each enclosure site during the experiment. Potential predators were excluded by cages and known quantities of food were provided to reduce potential impacts of food availability. Fish were individually tagged, and growth rates calculated for surviving fish. Abiotic conditions varied significantly among sites, although no differences in growth rates were detected among sites. Variability in growth rates both within and among sites was high, with 1 site experiencing total mortality. Results suggest that basic abiotic conditions, at the levels and durations that occur within a southeastern US estuary during summer, have little impact on juvenile summer flounder growth, but may influence survival.

Dietary Lipid Utilization by Juvenile Summer Flounder Paralichthys dentatus

AbstractThe ability of juvenile summer flounder Paralichthys dentatus to utilize dietary lipid as energy, and the effect of dietary lipid on weight gain and body composition was investigated in a 12‐week feeding trial. Diets were formulated to provide 55% crude protein from herring meal and casein. Menhaden oil was added to produce diets with 8, 12, 16 or 20% total lipid while providing 16.0 kJ available energy/g dry diet. The diet containing 20% total lipid supplied 16.7 kJ available energy/g dry diet due to the high levels of protein and lipid. An additional diet was included to reproduce currently available commercial diet formulations for flounder, providing 55% crude protein supplied solely from herring meal and 16% total dietary lipid. Juvenile summer flounder (initial weight 23 g) were stocked into triplicate aquaria in a closed, recirculating system maintained at 20 C. Fish were fed 2% of body weight each day divided into two equal feedings. Upon termination of the study, effects of dietary lipid on weight gain, body condition indices, and proximate composition were determined. Weight gain (96–149% of initial weight), feed efficiency ratio values (0.43–0.48). fillet yield, and whole‐body composition all were unaffected by dietary lipid level. High levels of dietary lipid did increase the lipid content in the finray muscle, as fish fed diets containing 16 and 20% dietary lipid had significantly higher lipid levels than fish fed the diet containing 8% lipid. No apparent protein sparing effect of lipid was observed. These data indicate that currently available commercial feeds for summer flounder may be over‐formulated and show a need for further research to determine specific and accurate nutritional information for this species.

Pilot evaluation of summer flounder stock enhancement potential using experimental ecology

Stock enhancement is receiving increasing attention as a management tool to rebuild depleted fisheries. Unfortunately, proactive studies addressing the potential of stock enhancement to accomplish management goals prior to the implementation of enhancement efforts are uncommon. We outline an ecologically based, pilot protocol with which to address the potential of fisheries stock enhancement using hatchery-reared (HR) organisms, through trial releases coupled with laboratory and field experiments with juvenile summer flounder Paralichthys dentatus. Released HR fish did not persist in nursery habitats in which wild fish enjoyed relatively long residence times and high sur- vival. Multiple lines of observations and evidence suggest that the relatively rapid disappearance of released HR fish was not a result of emigration. Caging and tethering trials, coupled with previously obtained behavioral data, suggest that the poor performance of HR fish in this study was a result of increased susceptibility to predation-induced mortality, as compared with wild fish. These results suggest that post-release survival of HR summer flounder might be increased by (1) improving meth- ods of predator-conditioning, (2) releasing HR fish in sites that serve as natural refuges from preda- tors, or (3) releasing fish at larger sizes. While poor post-release survival of HR summer flounder may limit the success of stock enhancement efforts with this species, we suggest that conclusions regard- ing the potential of stock enhancement as a management tool can only be made if biological in- formation is coupled with economic information to predict economic costs associated with stock enhancement relative to costs associated with alternative management approaches.

Effects of Ration Limitation and Low Temperature on Growth, Biochemical Condition, and Survival of Juvenile Summer Flounder from Two Atlantic Coast Nurseries

Laboratory experiments were conducted on juvenile summer flounder Paralichthys dentatus (25–80 mm total length) from Delaware and North Carolina nurseries to compare their responses to temperature and to ration limitation. Ad libitum feeding rates, maximum growth rates, and growth efficiency were measured at temperatures from 2 to 20°C. Although ad libitum feeding rates did not differ between fish from the two locations, North Carolina juveniles had higher maximum growth rates and growth efficiencies than Delaware juveniles between 6 and 18°C. Growth rates and changes in biochemical condition were also measured for different rations at temperatures that persist during the months following settlement (10–16°C). Survival was high (>98%) after 10–14 d of starvation and suboptimal rations at 10–16°C, but growth rates were highly dependent on feeding rates. Maintenance rations remained constant between 10 and 16°C, but scope for growth increased with temperature, Scope for growth of North Carolina juveniles was higher than that of Delaware juveniles between 10 and 16°C, and growth rates of North Carolina juveniles were more sensitive to changes in ration. Changes in RNA:DNA ratios over the course of each 10–14-d experiment depended primarily on ration; ratios increased as temperature and feeding rate increased. Low-temperature tolerance (at 1–4°C) of juveniles was highly dependent on the rate of temperature decline, not on feeding rate, Time until 50% mortality (LT50) varied from 14 d (–1.3°C/d, fast rate) to 31 d (–0.3°C/d, slow rate); North Carolina juveniles were significantly less tolerant of decreasing temperatures than were Delaware juveniles.

Feeding, growth and survival of juvenile summer flounder Paralichthys dentatus: experimental analysis of the effects of temperature and salinity

Feeding, growth and survival of juvenile summer flounder Paralichthys dentatus: experimental analysis of the effects of temperature and salinity