•A new calibration of a DEB model for anchovy and a first set of parameter estimates for sardine in the Bay of Biscay.•Using a robust method for parameter estimation, the evolution strategy, ...guaranteeing the uniqueness of the solution.•The sardine model is derived from the anchovy one through a scenario approach that successively tested the effect of distinctive traits (size, spawning, feeding).•Bioenergetics and reproduction strategy strongly interact.•Sardine displays a slower but more regular energy allocation to both growth and reproduction than anchovy.
Similar or very contrasted puzzling population dynamics between anchovy and sardine occur worldwide. Underlying factors are not well understood, but insights towards different biological traits are suggested, in particular trophic specialisation, leading to different responses to environmental conditions. Based on most striking differences in biological and life history traits, i.e. size, spawning and feeding, we calibrated a bioenergetics model, based on the Dynamic Energy Budget theory, for Engraulis encrasicolus and Sardina pilchardus in the Bay of Biscay. Starting from the anchovy model, differences in traits were successively integrated to build the sardine model through a novel exploratory approach by scenarios. We used a robust method for parameter estimation, the Evolution Strategies, with a large dataset of length and mass at age, as well as energy density, which is the first time in such a model calibration. Energy density data proved to be particularly well suited to assess the quality of DEB model predictions and parameter set estimates. Insights in respective physiology were drawn from analysis of parameter values and predictions of the model. We showed that anchovy and sardine have distinct strategies with respect to energy acquisition and especially to allocation to spawning. Anchovy are characterised by higher metabolic rates and requirements. This species is more likely to benefit from periods of high food availability to carry out both growth, spawning and reserve storage. Sardine have less demanding food requirements and metabolic costs. Sardine take advantage of larger reserves storage capacity to decouple spawning and prey blooms and to lengthen spawning period, and thus display a more capital breeding spawning behaviour. Overall, our model outputs distinguish between anchovy that tend towards an almost “all or nothing” energetic strategy, and sardine that tend to carry out lower metabolic activities but on a more regular basis. This first modelling demonstration of a bioenergetics difference between these two species, and the explanation it brings in the understanding of their respective reproduction strategies, opens new perspectives in the interpretation of their differential responses at the population scale to environment variability.
CXC chemokine receptor 4 (CXCR4), a member of the G-protein-coupled chemokine receptor family, can serve as a co-receptor along with CD4 for entry into the cell of T-cell tropic X4 human ...immunodeficiency virus type 1 (HIV-1) strains. Productive infection of T-lymphoblastoid cells by X4 HIV-1 markedly reduces cell-surface expression of CD4, but whether or not the co-receptor CXCR4 is down-regulated has not been conclusively determined.
Infection of human T-lymphoblastoid cell line RH9 with HIV-1 resulted in down-regulation of cell surface CXCR4 expression. Down-regulation of surface CXCR4 correlated temporally with the increase in HIV-1 protein expression. CXCR4 was concentrated in intracellular compartments in H9 cells after HIV-1 infection. Immunofluorescence microscopy studies showed that CXCR4 and HIV-1 glycoproteins were co-localized in HIV infected cells. Inducible expression of HIV-1 envelope glycoproteins also resulted in down-regulation of CXCR4 from the cell surface.
These results indicated that cell surface CXCR4 was reduced in HIV-1 infected cells, whereas expression of another membrane antigen, CD3, was unaffected. CXCR4 down-regulation may be due to intracellular sequestering of HIV glycoprotein/CXCR4 complexes.
Understanding the distribution and reproductive behavior of marine species can inform ocean spatial management to address conservation needs and reduce risks of conflicts among various marine and ...coastal industries. Combining spatial data on species behavior with fish harvesters’ knowledge can be particularly effective for identifying spatiotemporal overlaps between human activities and critical events at various life stages of marine species. In the present study, the migratory behavior of Atlantic halibut (Hippoglossus hippoglossus), a flatfish of great economic importance in the Gulf of St. Lawrence, was characterized using electronic tags, and potential ocean industry impacts to the halibut population were identified using fish harvesters’ knowledge reported at public meetings and during semi-structured interviews. Results from electronic tagging analyses, including potential seasonal migration paths and presumed spawning locations, were presented to halibut harvesters who responded by identifying industries that could impact the halibut population. Harvesters identified the potential for halibut bycatch in the developing redfish trawl fishery as the main risk to the current high halibut abundance levels, which they attributed to the reduction of Gulf trawling and halibut bycatch since the 1990s. Other potential impacts to halibut identified by harvesters included offshore oil and gas drilling, and effluent discharge from a paper mill transformation project. The present study demonstrates that utilizing complementary data from both fish tracking devices and fish harvesters’ knowledge can help identify and anticipate potential conflicts between fisheries and other ocean industries, and ultimately inform the ecosystem-based marine spatial management of large marine ecosystems.
•Fish tracking devices combined with fish harvesters’ knowledge revealed spatial overlaps of fisheries and other ocean uses.•Atlantic halibut presumed spawning habitats overlap with potential trawling areas of a re-emerging redfish fishery.•Halibut may also be impacted by oil drilling and paper pulp effluent in locations that overlap with halibut migrations.•Using complementary data sources can identify ocean use conflicts and inform ecosystem-based marine spatial management.
Anchovy Engraulis encrasicolus distribution in European waters spans from the Mediterranean Sea to the North Sea, and is expected to expand further north with global warming. Observations from the ...eastern Mediterranean (North Aegean Sea), the Bay of Biscay and the North Sea reveal latitudinal differences in growth, maximum size, fecundity and timing of reproduction. We set up a mechanistic framework combining a bioenergetics model with regional physical–biogeochemical models providing temperature and zooplankton biomass to investigate the underlying mechanisms of variation in these traits. The bioenergetics model, based on the Dynamic Energy Budget theory and initially calibrated in the Bay of Biscay, was used to simulate growth and reproduction patterns. Environment partly explained the increased growth rate and larger body size towards the north. However, regional calibration of the maximum assimilation rate was necessary to obtain the best model fit. This suggests a genetic adaptation, with a pattern of cogradient variation with increasing resource towards the north, in addition to a countergradient thermal adaptation. Overall, the seasonal energy dynamics supports the pattern of body-size scaling with latitude, i.e. food-limited growth but low maintenance costs in the warm Aegean Sea, and larger size in the North Sea allowing sufficient storage capacity for overwintering. Further, the model suggests a synchronisation of reproductive timing with environmental seasonality as a trade-off between thresholds of temperature and reserves for spawning and overwintering, respectively. Finally, low temperature, short productive and spawning seasons, and insufficient reserves for overwintering appear to be current limitations for an expansion of anchovy to the Norwegian Sea.
Growing evidence suggests that complex spatial structure occurs within the Scotian Shelf and southern Grand Banks (SSGB) Atlantic halibut stock, yet large knowledge gaps remain about diversity of ...migratory and spawning behaviors. Here, 71 pop-up satellite archival tags were deployed on large Atlantic halibut (FL: 87–166 cm) between 2012 and 2020. Migration tracks were successfully reconstructed for 43 fish using a hidden Markov geolocation model, and temperature and depth time series were available for an additional nine fish (total n = 52). Five migratory behavior categories were identified: shelf residency, slope residency, shelf-channel migration, shelf-slope migration, and dispersal. High-resolution data for four of 20 physically recovered tags provided evidence of putative spawning behavior in deep channels on the continental shelf and along the continental slope between January and February. Additionally, four halibut displayed previously undocumented periods of sustained, oscillatory vertical movements along the continental slope between November and February. The high migratory diversity observed in this study provides support for the existence of multiple resident and migratory contingents in the SSGB stock in the apparent absence of significant genetic structure.
We assessed the impact of an additional 100 mm square mesh cylinder (SMC) on the selective property of the demersal whitefish trawl in the Celtic Sea. Sea trials were conducted on board a French ...trawler using twin trawl rigging. We tested the effects of the position of the SMC (in front of and behind the mandatory 100 mm square mesh panel) and of the insertion of a dispersive float. Selectivity analysis revealed the 50% retention length (L50) to be greater than the Minimum Conservation Reference Sizes regardless of species (haddock, whiting or megrim) or rigging configuration. Results did not reveal a clear effect of the SMC position. However, the insertion of the float led to a decrease in selection ranges suggesting enhanced contact probabilities with the square meshes. With the largest L50 values, the SMC placed in the front position (and without the float) proved to be the most selective rigging configuration and was then tested under commercial conditions. Catch comparisons revealed that the test gear retained less fish across all size classes than the commercial gear. For haddock, the test gear retained less fish below 50 cm in length. Catch comparisons also indicated significant discards of fish above the MCRS, i.e. “high-grading” practices. Under the requirements of the landing obligation (LO), unwanted catches must be stored on-board and landed regardless of economic value. The SMC is thus a valuable tool to mitigate the impact of the LO on the demersal whitefish fishing fleets operating in the Celtic Sea.
•Test of a 100 mm SMC in addition to the mandatory 100 mm SMP.•No clear effect of SMC position.•The dispersive float inside the SMC sharpened selection curves, suggesting enhanced escapement trials by fish at any size.•Escapement of several fish larger than the MCRS, but no commercial losses, due to on-board sorting practices.•Combination of absolute and relative size selectivity analysis strengthened study conclusions.
Abstract
Knowledge of movement ecology, habitat use, and spatiotemporal distribution is critical to inform sustainable fisheries management and conservation. Atlantic halibut in the Gulf of St. ...Lawrence (GSL) is of great economic value, although little is known about its spatiotemporal distribution, seasonal migrations, and spawning areas. To investigate these aspects, 114 pop-up satellite archival tags (PSATs) were deployed on halibut from 2013 up to 2018 throughout the GSL. A total of 62 physically recovered PSATs provided complete archived datasets with high temporal resolution. PSAT detachment locations revealed specific summer site fidelity. In contrast, the reconstruction of movement tracks with a geolocation model revealed that all fish converged to the Gulf’s deep channels to overwinter and spawn. This suggests strong mixing during the spawning period and thus one reproductive population within the GSL. These findings illustrate the utility of large-scale PSAT tagging combined with dedicated PSAT-recovery surveys to reveal critical stock-scale information on movements and spawning locations. This information addresses important gaps in the movement ecology of this halibut stock, revealing that reported summer site fidelity, based on years of conventional tagging, also conceals important winter mixing that is only apparent through analyses of movement on the time scale of annual cycles.
Reproductive timing, location, and behavior are important characteristics that determine marine population dynamics, structure, and resilience to threats, including fishing and climate change. It is ...challenging to evaluate factors driving variability in these reproductive traits in wild fishes because of the difficulty observing individuals in their natural environments. In the present study, we used high-resolution depth, temperature, and acceleration time series recorded by pop-up satellite archival tags to (1) identify and characterize patterns in depth and acceleration that may be indicative of spawning events in large Atlantic halibut (Hippoglossus hippoglossus), and (2) estimate the effects of individual traits (body size and sex) and environmental factors (location and temperature) on spawning time and frequency. Unique rapid rises observed in the winter depth profiles were interpreted as spawning events. The initiation of the first presumed spawning rise was negatively correlated to water temperature experienced during the prespawning season, suggesting that currently increasing water temperature in the Gulf of St. Lawrence may induce phenological change in halibut spawning time. The number of rises of batch-spawning females was unrelated to female body size. The present study demonstrates how electronic tagging can be used for in-depth characterization of timing, location, and behaviors associated with spawning in a large flatfish species. Such information can inform spatiotemporal management and conservation measures aiming to protect species from directed fishing and by-catch during spawning.
Uncertainties in fish tracking studies limit their integration into conservation and fisheries management plans. This is especially true for archival tagging studies that rely on geolocation models ...to infer fish tracks from recorded environmental variables. Hidden Markov Models (HMMs) are increasingly popular to geolocate marine fish equipped with archival tags; however, true errors and sensitivity of geolocation HMMs are seldom evaluated. In this study, we first review validation methods and implementations of geolocation HMMs to adapt to regional oceanography, fish species and tag data. We then use a case‐study to evaluate strengths and limitations of each validation approach and to illustrate the sensitivity of geolocation HMMs to implementation assumptions. Simulated and fixed tag locations are the most widely implemented methods, but less common methods relying on true fish tracking, that is double‐tagging or distance from recapture experiments, provide more informative estimates of model accuracy and precision. Results showed that model performance can be improved using simple assumptions when pre‐processing tag data rather than using a complex movement behaviour model. In addition, accelerometer show potential to further parameterise geolocation models. Overall, results from our case‐study and previous studies showed that current geolocation HMMs have average errors of ca. 30–50 and 120 km for demersal and large pelagic fish, respectively. We suggest that these errors are acceptable for investigations at the scale of fisheries management units.
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