Reproductive Migration Research Articles

Lipid distribution and composition in Antarctic toothfish before and after reproductive migration: implications for the life cycle

Lipid distribution and composition in Antarctic toothfish before and after reproductive migration: implications for the life cycle

Ecological stoichiometric of C, N and P of Coilia species

Fish of the Coilia genus play a crucial ecological role by serving as a vital link between marine and freshwater ecosystems. To gain a comprehensive understanding of the ecological patterns, intra-interspecific variations, and potential determinants of Coilia from an ecological stoichiometry perspective, analyzed the concentrations of C, N, and P elements in various types of Coilia, including C. nasus, C. mystus, C. grayii, C. brachygnathus, and C. nasus taihuensis, across the Yangtze River basin. The result shows that: 1) A broad spectrum of eco-stoichiometric patterns within Coilia species, facilitating their adaptation to diverse ecosystems, including seawater and freshwater. Specifically, the C content in Coilia species from 40% to 70%, while N% and P% range between 4%–12% and 0.5%–3%, respectively. 2) Intriguingly, interspecific variations in eco-stoichiometric patterns are predominantly driven by anadromous populations. The anadromous Coilia species, including C. nasus, C. mystus, and C. grayii, exhibit significantly higher C contents and C/N, C/P, and N/P ratios compared to their landlocked and freshwater counterparts (C. nasus taihuensis and C. brachygnathus). However, the trends in N and P content are reversed. 3) Intraspecific differences vary among Coilia species, notably observed in C. nasus taihuensis and C. brachygnathus, where there's minimal correlation with body size. Conversely, C. nasus and C. mystus demonstrate a substantial influence of body size, with increasing fish size associated with higher C content, C/N, C/P, and N/P ratios, while N and P content decrease. This suggests that larger fishes store more energy (C%) in preparation for reproductive migration. In conclusion, this study provides a scientific foundation for comprehending the ecological patterns and intra-interspecific variations in Coilia. Furthermore, it contributes to the application of ecological chemometrics in the study of migratory fish, enriching our understanding of the intricate dynamics within this ecologically significant species.

Superoxidase dismutases (SODs) in the European eel: Gene characterization, expression response to temperature combined with hormonal maturation and possible migratory implications

Superoxide dismutases (SODs) are antioxidant enzymes that protect cells from oxidation. Three SODs have been identified in mammals, but there is limited information in teleosts. This study investigates SODs in the European eel and their expression patterns during testis maturation. Phylogenetic and synteny analyses revealed SODs paralogs and their evolution in vertebrates. The eel possesses one SOD1 and two SOD2/3 (a and b), indicating SOD2 and SOD3 duplication in elopomorphs. SODs expression were then evaluated in various male and female tissues. SOD1 is more expressed in females, while SOD2a and SOD2b dominate brain-pituitary-gonad tissues in both sexes. SOD3a showed predominant expression in the ovary and the male livers, whereas SOD3b was found in the pituitary and brain of both sexes. The effects of different maturation protocols (standard hormonal treatment vs. same protocol preceded with cold seawater pre-treatment) on SODs expression during testis maturation were evaluated. Salinity increase at the onset of standard treatment at 20 °C, simulating early migration, upregulated SOD1, SOD2a, and SOD2b, coinciding with spermatogonia type A differentiated cells dominance. Thereafter, SOD2a and SOD3a decreased, while SOD2b increased during hormonal treatment-induced spermatogenesis. Pre-treatment with seawater at 10 °C, mimicking the conditions at the beginning of the seawater migration, downregulated SOD1 but increased SOD3a expression. Finally, the standard hormonal treatment, replicating spawning at higher temperatures, downregulated SOD1 in eels without any pre-treatment while SOD2a expression increased in pre-treated eels. This study revealed tissue-specific, sex-dependent, and maturation-related SOD expression patterns, predicting SODs dynamic expression profiles during their reproductive migration.

An assessment of the potamodromous fish Opsariichthys uncirostris uncirostris (Hasu fish) during its reproductive migration to a Lake Biwa tributary using stable isotope ratios and biometric data

An assessment of the potamodromous fish Opsariichthys uncirostris uncirostris (Hasu fish) during its reproductive migration to a Lake Biwa tributary using stable isotope ratios and biometric data

Ascaridoid Nematodes Infection in Anadromous Fish Coilia nasus from Yangtze River

The longjaw tapertail anchovy Coilia nasus, which migrates from ocean to freshwater for spawning in spring, is an important anadromous fish with ecological and cultural significance. To determine parasite infection in anadromous C. nasus, a total of 103 fish from the Yangtze River were collected and examined in 2021 and 2022. The overall infection prevalence of nematodes in C. nasus was 100%, with a mean intensity of 13.81 ± 16.45. The mean intensity of nematode infections in 2022 was significantly higher than that observed in 2021 across all sampling sites (p < 0.05). Nematodes were widely detected in the mesentery, pyloric cecum, stomach, and liver, among which the mesentery accounted for the highest proportion, reaching up to 53.52%. A total of eight ascaridoid nematodes belonging to the family Anisakidae and Raphidascarididae were identified by using morphological characters and molecular biological techniques, including two species of Anisakis, five species of Hysterothylacium, and one species of Raphidascaris. A. pegreffii was found as the predominant species, accounting for 48.65% of all identified parasitic nematodes in liver, while Raphidascaris sp. was the most common nematode in the mesentery, pyloric cecum, and stomach, reaching up to 39.81%, 36.21%, and 74.36%, respectively. The present study systematically investigated the parasitic status and community structure of the nematode in C. nasus during its migration in the Yangtze River. This research provides a foundation for studying the impact of nematode parasitism on the reproductive migration and population recruitment of C. nasus, and offers valuable insights for biomarker screening and nematode identification in C. nasus.

Gulf householding: implications of gulf migration for social reproduction

ABSTRACT This paper introduces the idea of ‘Gulf householding’ to reflect on migrant households that send their members to the Arab Gulf states for work and rely on material and non-material supports for formation and sustenance of households. Millions of households in the global South receive remittances from the Arab Gulf states, amounting to more than US$135 billion annually, and this vast amount of household income is a manifestation of Gulf householding. The paper examines the implications of Gulf householding for social reproduction by centreing on key spheres of household activities. Empirically, this study draws on interviews with Gulf migrant households at a village in Bihar, India. This research reports that access to the Gulf labour market and remittances shapes the quality of life of Gulf households. This study suggests that research on Gulf householding across multiple countries and regions has the potential to underscore the complex development processes from below.

Traffic and weather influence on small wildlife carcass persistence time on roads

The rapidly expanding road network threatens the persistence of many terrestrial species through mortality associated with wildlife-vehicle collisions. Roadkill monitoring under-estimate actual collision numbers as the time during which roadkill carcasses remain visible on the road is often shorter than the frequency of road monitoring. By placing passerine and amphibian carcasses on stretches of roads we surveyed every 2 h, we fine-tuned existing persistence estimates for these species. The time for half of the carcasses to disappear was less than 30 min for birds and 1–18 h for amphibians depending on the volume of traffic, which is much shorter than previous estimates. We show the implications of our results by performing roadkill surveys on common toads 3 h after the window of reproductive migration, showing roadkill is under-estimated by half, and by estimating from citizen-science data that passerine collisions could be as high as 10 individuals.km-2.year-1 in south-eastern France.

Long-term trends in juvenile Mugil liza abundance in relation to selected environmental and fisheries influences in southern Brazil

Overfishing constitutes a major threat affecting marine fish population worldwide, including mullet species that have been exploited by fisheries during the reproductive migration in temperate and tropical latitudes for millennia. In the present study, we investigated the relationship of fishing intensity of mullet Mugil liza during its reproductive migration and the abundance of their juveniles in an essential nursery ground for the species in the southwest Atlantic Ocean. To carry out this analysis, we used a 23-year standardized long-term time series (1997–2019) of monthly abundance of M. liza juveniles, local/regional (water temperature, salinity, water transparency and river discharge) and global (ENSO) environmental factors, along with compilations of fishing landing data for the species. Generalized Additive Models (GAM) revealed the negative effect of fishing adult populations on the abundance of juveniles when they reach the marine surf-zone and after recruiting into the estuary. Our results reinforce the importance of adequate conservation and fishery regulation policies to prevent the species' stock from collapsing.

Identifying migration hotspots of the potamodromous fish Opsariichthys uncirostris in Lake Biwa tributaries using environmental DNA and visual counts during its reproductive season

AbstractMigration is vital for the continuation of a species. In this study, we explored migration hotspots of the vulnerable Hasu fish in Lake Biwa tributaries using two complementary methods: environmental DNA (eDNA) and visual counts. The study encompassed the known range of Hasu around Lake Biwa tributaries during its reproductive season. Monthly water sampling and visual inspection was conducted, from May to September, in 32 Class A tributaries—at the river mouth and within the river channel. Hasu eDNA was extracted from water samples and quantified using real‐time polymerase chain reaction. Environmental factors were also assessed on‐site, and their effects on eDNA and visual count trends evaluated using linear models and Akaike information criterion. eDNA was detected at sites where the fish were both observed and not observed. A zero‐hurdle model revealed positive correlation between eDNA copies and visual counts of migrating Hasu, with pH having a reducing effect on the relationship (p < 0.05). Analysis of Hasu eDNA copies and visual count trends, with environmental factors as explanatory variables, indicates that Hasu is likely to be found in rivers that are wide and deep enough to accommodate migrating individuals, have fast‐flowing currents, and sandy‐gravel substrates during reproductive migration. Such rivers are mostly located on the western side of the northern basin and include the Ado, Chinai, and Shiotsuo Rivers. These could be considered as Hasu migration hotspots and require protecting if the population of Hasu in Lake Biwa is to be recovered.

Репродуктивна динаміка ропухи сірої Bufo bufo (Linnaeus, 1758) і жаби трав’яної Rana temporaria (Linnaeus, 1758) як один з ключових етапів їх сезонного циклу

The results of research on the reproductive dynamics of the key amphibian species of the Ukrainian Roztochchia are presented. Since reproduction is one of the most important and key stages of the seasonal cycle of amphibians, special attention was paid to this period. We used classic and typical methods of recording reproductive activity of amphibians: route records, searching for dead amphibians on the roads, vocalization methods and installation of temporary protective barriers that prevent amphibians from crossing the road. Therefore, amphibians of the genera Rana and Bufo belong to the species with a sudden type of reproduction. We included representatives of the genera Lissotriton, Triturus, Bombina, Hyla, and Pelophylax to the long-term breeding species. In particular, temporary protective barriers gave us indicative and clear concepts regarding the temporal peaks and troughs of reproductive migrations of the studied amphibian species, as well as the direction of movement to reproductive and trophic habitats. Comparing the beginning of reproductive activity and its course throughout the season, we can see certain differences between the model species B. bufo and R. temporaria, in particular, the choice of breeding ponds, the time of spawning and the period of activity of sexually active individuals. Reproductive activity of the common frog occurs in the first half of March — mid-April. In the second half of April, we caught common frogs on both sides of the barriers, which indicates a “turning point” in the sexual activity of this species. Although the common toad is the first to appear after hibernation, spawning occurs approximately a decade later than that of the common frog but takes a little longer. We believe that such research should be continued regularly and our results will encourage herpetologists to further and long-term research.

Effects of temperature and precipitation changes on shifts in breeding phenology of an endangered toad

In the last century, a plethora of species have shown rapid phenological changes in response to climate change. Among animals, amphibians exhibit some of the greatest responses since their activity strongly depends on temperature and rainfall regimes. These shifts in phenology can have negative consequences for amphibian fitness. Thus, understanding phenological changes in amphibians is pivotal to design conservation actions to mitigate climate change effects. We used data on Common Spadefoot Toad (Pelobates fuscus) reproductive migration to wetlands over a period of 8 years in Italy to (i) identify the factors related to breeding migrations, (ii) assess potential phenological shifts in the breeding period, and (iii) determine which climatic factors are related to the observed phenological shifts. Our results showed that toads migrate to spawning sites preferably in early spring, on rainy days with temperatures of 9–14 °C, and with high humidity. Furthermore, despite an increase in average temperature across the study period, we observed a delay in the start of breeding migrations of 12.4 days over 8 years. This counterintuitive pattern was the result of a succession of hot and dry years that occurred in the study area, highlighting that for ephemeral pond breeders, precipitation could have a larger impact than temperature on phenology. Our results belie the strong presumption that climate change will shift amphibian phenology toward an earlier breeding migration and underline the importance of closely investigating the environmental factors related to species phenology.

Phylogeography of the true freshwater crab, Geothelphusa dehaani: Detected dual dispersal routes via land and sea

Dispersal is an important factor that determines the potential for colonization to pioneer sites. Although most decapods employ seaward migration for reproduction with a planktonic larval phase, true freshwater crabs spend their entire life cycle in freshwater. Therefore, it is expected that genetic regionality can be easily detected. In this study, we focused on true freshwater crabs, Geothelphusa Stimpson, 1858. Herein, we reveal the evolutionary history and dispersal patterns of freshwater crustaceans. We collected and genetically analyzed 283 specimens at 138 localities across the Japanese Islands. Phylogenetic analyses were conducted on the combined dataset (mtDNA COI, 16S, and nDNA ITS1, histone H3 regions) and the data set based on the mtDNA COI region. The phylogenetic relationships detected 10 clades that were highly monophyletic. The highlights of this study were the discovery of several cryptic species or undescribed species, and the completely different heterogeneous dual dispersal pathways within a single species; i.e., both land and ocean routes. Although it was concluded that Japanese crabs are basically genetically divided by straits, strong evidence for dispersion via ocean currents was also detected (i.e., a “sweepstake”). It was also confirmed that Geothelphusa dehaani (White, 1847) could survive in seawater.

Differential digestive and metabolic profile of juveniles and adults of the estuarine-dependent marine fish Mugil liza (Mugilidae) cohabiting inside a southwestern Atlantic coastal lagoon

Integrative studies on intraspecific differences of digestive enzymes, energy reserves, and morphological/somatic traits in juveniles and adults of estuarine-dependent marine fish while inhabiting inside a coastal lagoon are lacking. This study was carried on juveniles and adults of Mugil liza Valenciennes, 1836 inhabiting inside Mar Chiquita Coastal Lagoon (Argentina). Both stages exhibited amylase, maltase, sucrase, lipase, trypsin, and aminopeptidase-N activities in the intestine, which were active over a wide range of pH and temperatures and exhibited Michaelis–Menten kinetics. Adults exhibited higher intestinal coefficient (31%), higher amylase (32%), and lower maltase (82%) and lipase activities (38%). Glycogen concentration in liver and muscle was similar, while free glucose concentration was higher in adults (772% and 400%, respectively). In adults, retroperitoneal fat (absent in juveniles) constituted the main triglycerides (TAG) storage site, while TAG concentration in liver and muscle was lower (86% and 80%, respectively) than that in juveniles. No differences were found in protein concentration in any storage organ. The results show that juveniles and adults exhibit a digestive and metabolic profile at the biochemical level and intraspecific differences in key components of carbohydrate and lipid metabolism that could support preparation for reproductive migration of adults outside the coastal lagoon.

Analysis of short-term and local scale variations in fish community structure in Dachen Island waters

Understanding the changes in community structure of fishery resources in island reef waters is crucial for effective fishery resource management, as these waters constitute a critical link in maintaining the sustainable development of offshore fishery resources. The study analyzed the structure of the fish community in the waters surrounding Dachen Island by using data collected during four voyage surveys conducted between September 2020 and April 2021. The study utilized co-occurrence network analysis, multiple regression trees, and functional diversity analysis to investigate the short-term and local scale changes in fish community structure. The results showed that the fish community in the waters adjacent to Dachen Island can be categorized into two groups: annual and stage-use species. The stage-use species include Scoliodon laticaudus, Trichiurus lepturus, Tetraodontidae, and others, which are used during the summer and autumn stages of bait migration. Additionally, Dasyatidae and others, which used during the winter and spring stages of reproductive migration. Furthermore, the study found that the habitats dominated by nearshore rocky habitats and distant deep habitats formed the local scale variation in community structure in island waters. The integrated analysis of species α-diversity and functional diversity provided a basis for understanding the mechanisms of biodiversity action. Our study aims to provide a theoretical framework for the development of fishery resource management strategies based on the life cycle of fish, and to serve as a reference for the prioritization of key protection areas for fishery resources in island and reef environments. Overall, the study’s findings can promote the understanding of community structure dynamics in island waters. Additionally, these findings can offer valuable insights into the restoration of habitats and the implementation of marine ranching activities in Dachen Island. Moreover, the outcomes can serve as a theoretical foundation for the development of appropriate management and conservation strategies for fisheries resources.

Diverse environmental cues drive the size of reproductive aggregation in a rheophilic fish

BackgroundAnimal migrations are periodic and relatively predictable events, and their precise timing is essential to the reproductive success. Despite large scientific effort in monitoring animal reproductive phenology, identification of complex environmental cues that determine the timing of reproductive migrations and temporal changes in the size of reproductive aggregations in relation to environmental variables is relatively rare in the current scientific literature.MethodsWe tagged and tracked 1702 individuals of asp (Leuciscus aspius), a large minnow species, and monitored with a resolution of one hour the size of their reproductive aggregations (counts of sexes present at the breeding grounds standardized by the sum of individuals in the season) over seven breeding seasons using passive integrated transponder tag systems. We examined the size of reproductive aggregations in relation to environmental cues of day number within a reproductive season (intra-year seasonality), water temperature, discharge, hour in a day (intra-day pattern), temperature difference between water and air, precipitation, atmospheric pressure, wind speed and lunar phase. A generalized additive model integrating evidence from seven breeding seasons and providing typical dynamics of reproductive aggregations was constructed.ResultsWe demonstrated that all environmental cues considered contributed to the changes in the size of reproductive aggregations during breeding season, and that some effects varied during breeding season. Our model explained approximately 50% of the variability in the data and the effects were sex-dependent (models of the same structure were fitted to each sex separately, so that we effectively stratified on sex). The size of reproductive aggregations increased unimodally in response to day in season, correlated positively with water temperature and wind speed, was highest before and after the full moon, and highest at night (interacting with day in a season). Males responded negatively and females positively to increase in atmospheric pressure.ConclusionThe data demonstrate complex utilization of available environmental cues to time reproductive aggregations in freshwater fish and their interactions during the reproductive season. The study highlights the need to acquire diverse data sets consisting of many environmental cues to achieve high accuracy of interpretation of reproductive timing.Graphical abstract

The effects of spatial and temporal variations in spawning on offspring survival in Northeast Arctic cod

Abstract Climate change and harvesting result in temporal and spatial changes and variability in spawning, and thus in offspring ambient drift conditions. As a result, variable survival of offspring and thereby in recruitment are expected. This is especially true for species with long reproduction migration as is the case for some Atlantic cod stocks. We utilize biophysical model simulations to analyze survival from spawning until age 1 resulting from different scenarios of spatial and temporal changes in spawning. We find that survival is 1.5–2 times higher when spawning is shifted southwards as compared to northerly shifts. In general, survival is more sensitive to shifts in spawning location than in spawning time. Early spawning is only favourable if spawning is concurrently shifted farther north. A future spawning scenario with a northward shift in spawning grounds beyond what has been observed historically suggests reduced offspring survival and increased sensitivity to the timing of spawning.

Redefining Bioavailability through Migrant Egg Donors in Spain

This article utilises feminist technoscience studies’ notions of bodily ‘materialisation’ and ‘ontological choreographies’, offering a cyborg feminist account of ‘bioavailability’ as embodied becomings, rather than a fixed ontological state of being. Drawn from 2 years’ ethnographic study in in vitro fertilisation clinics in Spain with migrant women who provided eggs to the cross-border in vitro fertilisation industry, this work explores how global understandings of race and inequalities, clinical practices and women’s own emotional and physical labours collectively produce bioavailability. Through examples from observations and interviews in in vitro fertilisation clinics, we examined women’s embodied stories to understand the ways in which bioavailability becomes. The article demonstrates a novel way in which to think about ‘bioavailability’, a concept which has already been of enormous use to the social sciences since its introduction by Lawrence Cohen. We examine recent configurations of bodily extraction in the reproduction–migration nexus that help us rethink the concept of bioavailability.

The precision of the migration image of the depth section on the seismometry observations on northwestern Black Sea shelf

For many years, the Institute of geophysics has been developing original versions of the finite-difference migration and wavefield modeling techniques for a valid reproduction of the geological cross-section. The modeling provides a practical test of the accuracy of the reproduction of various geological structure features on a migration result and a way to define, in the observed field, the waves which can be used to produce a migration image of the geologic environment efficiently.
 In 2013, the Institute conducted a marine seismic investigation with reflection CDP (Common Deep Point) profiles on the continental slope of the NW part of the Black Sea. The registered wavefields were processed using full-wave finite-difference post-stack migration. The efficiency and validity of the processing methods for various geological structures were evaluated with the help of finite-difference modeling of the wavefield based on solving the wave equation on a grid with a seven-point pattern.
 The study validates the precision of marine seismic data processing using full-wave finite-difference post-stack migration with the help of wavefield modeling.

Gradually elevated salinities alter the haemolymph metabolic profile and nitrogenous wastes of the mature Chinese mitten crab, Eriocheir sinensis (Decapoda, Varunidae)

Abstract To understand the metabolic adjustments and nitrogen excretion in haemolymph of mature Eriocheir sinensis during the reproductive migration from fresh water to seawater, haemolymph metabolic variations and nitrogenous wastes were determined after gradual acclimation of females and males from fresh water to different salinities (7, 14, 21, 28 and 35). Total protein content in both female and male crabs was reduced with increased salinity. The contents of lipids including triglyceride and cholesterol significantly decreased at salinities of 0-21, suggesting the lipids of E. sinensis might be mobilized to produce energy for osmoregulation and gonad development at a different salinity. Interestingly, the lipid levels in the females were higher than those in the males, implying the females need to store more lipids to prepare for reproduction. The glucose level was low in this study, which was related to the diet with high protein. Haemolymph urea and uric acid level together decreased at first and then increased, indicating that E. sinensis could regulate the nitrogen excretion pattern by inhibiting or activating ureogenesis and uricogenesis to acclimate to a different osmotic environment. Notably, the females might be more tolerant to salinity increase and have a faster metabolic reorganization than males. These facts could indicate that a different strategy has been employed in mature E. sinensis when encountering salinity stress during the reproductive migration form fresh water to seawater.

Immune function modulation during artificial ovarian maturation in Japanese eel (Anguilla japonica): A transcriptome profiling approach

The Japanese eel (Anguilla japonica) experiences dramatic internal and external environmental changes during its transoceanic reproductive migrations. Here, we assess immune function changes in the primary and secondary immune organs (head kidney and spleen) of A. japonica during artificial ovarian maturation at the previtellogenic (PV), midvitellogenic (MV), and ovulating (OV) stages by transcriptome analyses. Stress responses were also assessed by determining the serum concentrations of lysozyme, alkaline phosphatase, acid phosphatase, total antioxidant capacity, and superoxide dismutase. Our results showed that together with increased serum 17β-estrogen and testosterone, lysozyme activity and antioxidant capacity were suppressed during artificial ovarian maturation. Comparisons across these developmental stages identified 60 (head kidney) and 36 (spleen) differentially expressed genes associated with the immune system. Genes related to the key activation markers of innate immune function, such as CXCL10, CXCL11, CCL20, HSP90B, MMP9, and MMP13, were upregulated and significantly enriched in the interleukin-17 signaling pathway. Adaptive immune function-related genes (IGM and MHC1) were upregulated in the head kidney from PV to MV, and their levels increased thereafter in the spleen. Moreover, a correlation between Pax5 expression and IGM expression in the spleen of MV (IGM+/Pax5+) and OV (IGM++/Pax5−) stage suggests that adaptive immune function was enhanced during ovarian maturation. To our knowledge, the present study is the first to describe transcriptome profiling of immune organs during ovarian maturation in teleost. Our findings suggest that the interleukin-17 pathway and IgM may play important roles in spawning.