Intra-Specific Difference in the Effect of Salinity on Physiological Performance in European Perch (<i>Perca fluviatilis</i>) and Its Ecological Importance for Fish in Estuaries

Changes in environmental salinity challenge fish homeostasis and may affect physiological performance, such as swimming capacity and metabolism, which are important for foraging, migration, and escaping predators in the wild. The effects of salinity stress on physiological performance are largely species specific, but may also depend on intra-specific differences in physiological capabilities of sub-populations. We measured critical swimming speed (U crit ) and metabolic rates during swimming and at rest at salinities of 0 and 10 in European perch ( Perca fluviatilis ) from a low salinity tolerance population (LSTP) and a high salinity tolerance population (HSTP). U crit of LSTP was significantly reduced at a salinity of 10 yet was unaffected by salinity change in HSTP. We did not detect a significant cost of osmoregulation, which should theoretically be apparent from the metabolic rates during swimming and at rest at a salinity of 0 compared to at a salinity of 10 (iso-osmotic). Maximum metabolic rates were also not affected by salinity, indicating a modest tradeoff between respiration and osmoregulation (osmo-respiratory compromise). Intra-specific differences in effects of salinity on physiological performance are important for fish species to maintain ecological compatibility in estuarine environments, yet render these sub-populations vulnerable to fisheries. The findings of the present study are therefore valuable knowledge in conservation and management of estuarine fish populations

The effects of temperature acclimation on swimming performance in the pelagic Mahi-mahi (Coryphaena hippurus)

Mahi-mahi (Coryphaena hippurus) are a highly migratory pelagic fish, but little is known about what environmental factors drive their broad distribution. This study examined how temperature influences aerobic scope and swimming performance in mahi. Mahi were acclimated to four temperatures spanning their natural range (20, 24, 28, and 32{\deg}C; 5-27 days) and critical swimming speed (Ucrit), metabolic rates, aerobic scope, and optimal swim speed were measured. Aerobic scope and Ucrit were highest in 28{\deg}C-acclimated fish. 20{\deg}C-acclimated mahi experienced significantly decreased aerobic scope and Ucrit relative to 28{\deg}C-acclimated fish (57 and 28% declines, respectively). 32{\deg}C-acclimated mahi experienced increased mortality and a significant 23% decline in Ucrit, and a trend for a 26% decline in factorial aerobic scope relative to 28{\deg}C-acclimated fish. Absolute aerobic scope showed a similar pattern to factorial aerobic scope. Our results are generally in agreement with previously observed distribution patterns for wild fish. Although thermal performance can vary across life stages, the highest tested swim performance and aerobic scope found in the present study (28{\deg}C), aligns with recently observed habitat utilization patterns for wild mahi and could be relevant for climate change predictions.Comment: 24 pages, 3 figures main text, 6 figures supplemental text, published in Frontiers in Marine Science https://www.frontiersin.org/articles/10.3389/fmars.2021.654276/ful

Mahi-mahi (Coryphaena hippurus) life development: morphological, physiological, behavioral and molecular phenotypes.

BackgroundMahi-mahi (Coryphaena hippurus) is a commercially and ecologically important fish species that is widely distributed in tropical and subtropical waters. Biological attributes and reproductive capacities of mahi-mahi make it a tractable model for experimental studies. In this study, life development of cultured mahi-mahi from the zygote stage to adult has been described.ResultsA comprehensive developmental table has been created reporting development as primarily detailed observations of morphology. Additionally, physiological, behavioral, and molecular landmarks have been described to significantly contribute in the understanding of mahi life development.ConclusionRemarkably, despite the vast difference in adult size, many developmental landmarks of mahi map quite closely onto the development and growth of Zebrafish and other warm-water, active Teleost fishes

Processing arctic eddy-flux data using a simple carbon-exchange model embedded in the ensemble Kalman filter

Author Posting. © Ecological Society of America, 2010. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 20 (2010): 1285–1301, doi:10.1890/09-0876.1.Continuous time-series estimates of net ecosystem carbon exchange (NEE) are routinely made using eddy covariance techniques. Identifying and compensating for errors in the NEE time series can be automated using a signal processing filter like the ensemble Kalman filter (EnKF). The EnKF compares each measurement in the time series to a model prediction and updates the NEE estimate by weighting the measurement and model prediction relative to a specified measurement error estimate and an estimate of the model-prediction error that is continuously updated based on model predictions of earlier measurements in the time series. Because of the covariance among model variables, the EnKF can also update estimates of variables for which there is no direct measurement. The resulting estimates evolve through time, enabling the EnKF to be used to estimate dynamic variables like changes in leaf phenology. The evolving estimates can also serve as a means to test the embedded model and reconcile persistent deviations between observations and model predictions. We embedded a simple arctic NEE model into the EnKF and filtered data from an eddy covariance tower located in tussock tundra on the northern foothills of the Brooks Range in northern Alaska, USA. The model predicts NEE based only on leaf area, irradiance, and temperature and has been well corroborated for all the major vegetation types in the Low Arctic using chamber-based data. This is the first application of the model to eddy covariance data. We modified the EnKF by adding an adaptive noise estimator that provides a feedback between persistent model data deviations and the noise added to the ensemble of Monte Carlo simulations in the EnKF. We also ran the EnKF with both a specified leaf-area trajectory and with the EnKF sequentially recalibrating leaf-area estimates to compensate for persistent model-data deviations. When used together, adaptive noise estimation and sequential recalibration substantially improved filter performance, but it did not improve performance when used individually. The EnKF estimates of leaf area followed the expected springtime canopy phenology. However, there were also diel fluctuations in the leaf-area estimates; these are a clear indication of a model deficiency possibly related to vapor pressure effects on canopy conductance.This material is based upon work supported by the U.S. National Science Foundation under grants OPP-0352897, DEB-0423385, DEB-0439620, DEB-0444592, and OPP- 0632139

Women’s subsistence strategies predict fertility across cultures, but context matters

While it is commonly assumed that farmers have higher, and foragers lower, fertility compared to populations practicing other forms of subsistence, robust supportive evidence is lacking. We tested whether subsistence activities—incorporating market integration—are associated with fertility in 10,250 women from 27 small-scale societies and found considerable variation in fertility. This variation did not align with group-level subsistence typologies. Societies labeled as “farmers” did not have higher fertility than others, while “foragers” did not have lower fertility. However, at the individual level, we found strong evidence that fertility was positively associated with farming and moderate evidence of a negative relationship between foraging and fertility. Markers of market integration were strongly negatively correlated with fertility. Despite strong cross-cultural evidence, these relationships were not consistent in all populations, highlighting the importance of the socioecological context, which likely influences the diverse mechanisms driving the relationship between fertility and subsistence

Optimizing Transport of Live Juvenile Cobia (Rachycentron canadum): Effects of Salinity and Shipping Biomass

Live juvenile cobia (Rachycentron canadum) transport methods were examined to determine opportunities for increasing packing density in closed containers for temporal durations up to 24 hours. Juvenile cobia (27 to 46 days-post-hatch (dph)) were tested for salinity tolerance following abrupt transfer from 35 ppt salinity water to salinities ranging from 0 ppt to 55 ppt. Results indicate a wide range of tolerance, with 100% survival at 24 hours post-transfer in salinities between 11 ppt and 45 ppt. Salinity preference was also tested to determine a possible correlation between acclimation salinity and salinity preference using an experimental horizontal salinity gradient with juvenile cobia (87 dph) over a period of 24 hours. Results of the salinity preference trials showed that salinity preference was directly related to acclimation salinity. Using two different salinities within the range tested in the tolerance trials (12 ppt and 32 ppt), a 24 hour simulated shipping trial was conducted comparing final survival between the two salinities at each of four packing densities (5 kg/m3, 10 kg/m3, 15 kg/m3, and 20 kg/m3). Results indicated a significant relationship between salinity and stocking density on survival of juvenile cobia following a 24 hour simulated shipment. At packing densities above 10 kg/m3, survival was significantly higher in the low salinity (12 ppt) treatments as compared to survival rates in the higher salinity (32 ppt) treatments. To help aquaculture professionals make accurate and economical decisions regarding the shipment of live juvenile cobia in closed containers, a bioeconomic model was constructed using survival data at different packing densities (1 kg/m3 to 20 kg/m3) and salinities (12 ppt and 32 ppt) obtained in the experimental trials combined with shipping cost and fingerling price data. The resulting model enables cobia fingerling producers to optimize their shipping methods and protocols, allowing for reductions in labor and material costs

Nutritional physiology of mahi-mahi (Coryphaena hippurus): Postprandial metabolic response to different diets and metabolic impacts on swim performance

Migratory pelagic fish species, such as the mahi-mahi (Coryphaena hippurus), must balance numerous metabolic demands simultaneously in order to survive in a challenging oceanic environment. Energetic support for such demands comes from a variety of natural prey items in the wild and can come from manufactured pelletized feed in captivity. This study quantified postprandial metabolism, commonly referred to as specific dynamic action (SDA), over time in adult mahi-mahi (706±25g; 38±0.7cm FL) in response to satiation feeding using three different natural and manufactured diets. Results indicate that during satiation feeding the amount of food ingested is dictated by energy content rather than prey mass, regardless of moisture content of the diet. Ingested meal energy did not differ significantly across groups (473±45kJ), nor did the duration of SDA (36±2.1h). Satiation feeding levels ranged from 2.9-16.2% bodyweight depending on the diet. Peak SDA and SDA magnitude were both significantly decreased in response to dry pelletized diet compared to the natural forage diets, despite equivalent energy consumption. Swim performance and maximum metabolic rate were not impacted significantly in satiation fed fish compared to unfed fish, supporting the evidence that mahi-mahi are able to maintain multiple metabolic demands at one time without compromising performance

Optimizing transport of live juvenile cobia (Rachycentron canadum): Effects of salinity and shipping biomass

Live juvenile cobia (Rachycentron canadum) transport methods were examined to determine opportunities for increasing packing density in closed containers for durations up to 24h. Juvenile cobia (27 to 46days post-hatch (dph)) were tested for salinity tolerance via abrupt transfer from 35ppt salinity water to salinities ranging from 0ppt to 55ppt. Results indicated 100% survival at 24h post-transfer at salinities between 11ppt and 45ppt. Using two different salinities within the range tested in the tolerance trials (12ppt and 32ppt), a 24h simulated shipping trial was conducted comparing final survival between the two salinities at each of four packing densities (5kg/m3, 10kg/m3, 15kg/m3, and 20kg/m3). At packing densities above 10kg/m3, survival was significantly enhanced at 12ppt relative to rates in the higher salinity (32ppt) treatments. Additionally, there were no apparent effects on post-transport aquaculture performance of the fish shipped at high densities in reduced salinity water. Results of this study suggest that cobia fingerling producers can optimize their current shipping methods and protocols by increasing stocking densities in closed containers, allowing for reductions in labor, material, and mass-dependent transport costs. ► We examined the effects of shipping variables on the survival of juvenile cobia. ► Focused on salinity and shipping biomass to determine optimal levels for live shipment. ► Juvenile cobia have a wide salinity tolerance, including abrupt transfer tolerance. ► Lower salinity treatment significantly reduced mortality at increased packing density. ► Potential for significant savings on behalf of cobia producers and operators

Chapter 1 - Overview on Status and Technological Advances in Tuna Aquaculture Around the World

The current status of tuna fiseries, fattening and farming practices, as well as advances in closed-cycle tuna aquaculture, are summarized. The emergence and expansion of tuna fattening and farming activities during the last four decades have led to a shift from traditional fisheries toward aquaculture. This change is entirely reshaping the tuna fishery industry and the management of their stocks worldwide. Tuna fattening and farming operations still rely primarily on wild-caught juveniles that are fattened using small pelagic fish, blurring the line between fisheries and aquaculture and merging these activities to the point that it is no longer possible to analyze them separately. Progress in fattening operations has been limited to improved management and decreased mortalities during the capture, towing, transferring, and feeding stages of the tuna in cages. However, tuna aquaculture is now rapidly changing due to remarkable progress in closed-cycle tuna aquaculture production through advancements in broodstock maturation, spawning, larval rearing, and juvenile production technologies. Indeed, following the pioneering achievement of closing the life cycle of the Pacific bluefin tuna (PBFT) in Japan, researchers the world over are now making significant progress in hatchery technology. Closing their life cycle and the development of ecologically and economically efficient feeds that meet the specific nutritional requirements of tuna are required to ensure the future of tuna production and the conservation of tuna species. Collective efforts by researchers, academics, and the global industry are making it possible to achieve these goals