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1. Daily Patterns of River Herring ( Alosa spp.) Spawning Migrations: Environmental Drivers and Variation among Coastal Streams in Massachusetts

   https://doi.org/10.1002/tafs.10301  

   Legett, Henry D. ; Jordaan, Adrian ; Roy, Allison H. ; Sheppard, John J. ; Somos‐Valenzuela, Marcelo ; Staudinger, Michelle D. ( May 2021 , Transactions of the American Fisheries Society)

   The timing of life history events in many plants and animals depends on the seasonal fluctuations of specific environmental conditions. Climate change is altering environmental regimes and disrupting natural cycles and patterns across communities. Anadromous fishes that migrate between marine and freshwater habitats to spawn are particularly sensitive to shifting environmental conditions and thus are vulnerable to the effects of climate change. However, for many anadromous fish species the specific environmental mechanisms driving migration and spawning patterns are not well understood. In this study, we investigated the upstream spawning migrations of river herringAlosaspp. in 12 coastal Massachusetts streams. By analyzing long‐term data sets (8–28 years) of daily fish counts, we determined the local influence of environmental factors on daily migration patterns and compared seasonal run dynamics and environmental regimes among streams. Our results suggest that water temperature was the most consistent predictor of both daily river herring presence–absence and abundance during migration. We found inconsistent effects of streamflow and lunar phase, likely due to the anthropogenic manipulation of flow and connectivity in different systems. Geographic patterns in run dynamics and thermal regimes suggest that the more northerly runs in this region are relatively vulnerable to climate change due to migration occurring later in the spring season, at warmer water temperatures that approach thermal maxima, and during a narrower temporal window compared to southern runs. The phenology of river herring and their reliance on seasonal temperature patterns indicate that populations of these species may benefit from management practices that reduce within‐stream anthropogenic water temperature manipulations and maintain coolwater thermal refugia.

    

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2. Going Downriver: Patterns and Cues in Hurricane-Driven Movements of Common Snook in a Subtropical Coastal River

   https://doi.org/10.1007/s12237-019-00617-y  

   Massie, Jordan A. ; Strickland, Bradley A. ; Santos, Rolando O. ; Hernandez, Javiera ; Viadero, Natasha ; Boucek, Ross E. ; Willoughby, Hugh ; Heithaus, Michael R. ; Rehage, Jennifer S. ( August 2019 , Estuaries and Coasts)

   Extreme climate events such as hurricanes can influence the movement and distribution of fish and other aquatic vertebrates. However, our understanding of the scale of movement responses and how they vary across taxa and ecosystems remains incomplete. In this study, we used acoustic telemetry data to investigate the movement patterns of common snook (Centropomus undecimalis) in the Florida Coastal Everglades during Hurricane Irma, which made landfall on the southwest Florida coast as a Category 3 storm on 10 September 2017 after passing in close proximity to our study site. We hypothesized that the hurricane resulted in shifts in distribution and that these movements may have been driven by environmental cues stemming from changes in barometric pressure associated with hurricane conditions, fluctuations in water levels (stage) characterizing altered riverine conditions, or a combination of both hurricane and riverine drivers. The data revealed large-scale movements of common snook in the time period surrounding hurricane passage, with 73% of fish detected moving from the upper river into downriver habitats, and some individuals potentially exiting the river. Furthermore, regression model selection indicated that these movements were correlated to both hurricane and riverine conditions, showing increased common snook movement at higher river stage and lower barometric pressure, and stage explaining a larger proportion of model deviance. Animal movement has widespread and diverse ecological implications, and by better understanding the factors that drive movement, we may anticipate how future extreme climate events could affect fish populations in impact-prone regions. 

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3. Acoustic signature reveals blue whales tune life‐history transitions to oceanographic conditions

   https://doi.org/10.1111/1365-2435.14013  

   Oestreich, William K. ; Abrahms, Briana ; McKenna, Megan F. ; Goldbogen, Jeremy A. ; Crowder, Larry B. ; Ryan, John P. ( February 2022 , Functional Ecology)

   Matching the timing of life‐history transitions with ecosystem phenology is critical for the survival of many species, especially those undertaking long‐distance migrations. As a result, whether and how migratory populations adjust timing of life‐history transitions in response to environmental variability are important questions in ecology and conservation. Yet the flexibility and drivers of life‐history transitions remain largely untested for migratory marine populations, which contend with the unique spatiotemporal dynamics and sensory conditions found in marine ecosystems.

   Here, using an acoustic signature of blue whales’ regional population‐level transition from foraging to breeding migration, we document significant interannual flexibility in the timing of this life‐history transition (spanning roughly 4 months) over a continuous 6‐year study period.

   We further show that variability in the timing of this transition follows the oceanographic phenology of blue whales’ foraging habitat, with a later transition from foraging to breeding migration occurring in years with an earlier onset, later peak and greater accumulation of biological productivity.

   These findings indicate that blue whales delay the transition from foraging to southward migration in years of the highest and most persistent biological productivity, consistent with the hypothesis that this population maximizes energy intake on foraging grounds rather than departing towards breeding grounds as soon as sufficient energy reserves are accumulated.

   The use of flexible cues (e.g. foraging conditions and long‐distance acoustic signals) in timing a major life‐history transition may be key to the persistence of this endangered population facing the pressures of rapid environmental change. Furthermore, these results extend theoretical understanding of the flexibility and drivers of population‐level migration to a relatively solitary marine migrant.

   Read the freePlain Language Summaryfor this article on the Journal blog.

    

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4. Stream and ocean hydrodynamics mediate partial migration strategies in an amphidromous Hawaiian goby

   https://doi.org/10.1002/ecy.3800  

   Lisi, Peter J. ; Hogan, J. Derek ; Holt, Galen ; Moody, Kristine N. ; Wren, Johanna L. K. ; Kobayashi, Donald R. ; Blum, Michael J. ; McIntyre, Peter B. ( August 2022 , Ecology)

   Partial migration strategies, in which some individuals migrate but others do not, are widely observed in populations of migratory animals. Such patterns could arise via variation in migratory behaviors made by individual animals, via genetic variation in migratory predisposition, or simply by variation in migration opportunities mediated by environmental conditions. Here we use spatiotemporal variation in partial migration across populations of an amphidromous Hawaiian goby to test whether stream or ocean conditions favor completing its life cycle entirely within freshwater streams rather than undergoing an oceanic larval migration. Across 35 watersheds, microchemical analysis of otoliths revealed that most adultAwaous stamineuswere freshwater residents (62% ofn = 316 in 2009, 83% ofn = 274 in 2011), but we found considerable variation among watersheds. We then tested the hypothesis that the prevalence of freshwater residency increases with the stability of stream flows and decreases with the availability of dispersal pathways arising from ocean hydrodynamics. We found that streams with low variation of daily discharge were home to a higher incidence of freshwater residents in each survey year. The magnitude of the shift in freshwater residency between survey years was positively associated with predicted interannual variability in the success of larval settlement in streams on each island based on passive drift in ocean currents. We built on these findings by developing a theoretical model of goby life history to further evaluate whether mediation of migration outcomes by stream and ocean hydrodynamics could be sufficient to explain the range of partial migration frequency observed across populations. The model illustrates that the proportion of larvae entering the ocean and differential survival of freshwater‐resident versus ocean‐going larvae are plausible mechanisms for range‐wide shifts in migration strategies. Thus, we propose that hydrologic variation in both ocean and stream environments contributes to spatiotemporal variation in the prevalence of migration phenotypes inA. stamineus. Our empirical and theoretical results suggest that the capacity for partial migration could enhance the persistence of metapopulations of diadromous fish when confronted with variable ocean and stream conditions.

    

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5. A hydrogen isoscape for tracing the migration of herbivorous lepidopterans across the Afro‐Palearctic range

   https://doi.org/10.1002/rcm.9675  

   Ghouri, Sana ; Reich, Megan S. ; Lopez‐Mañas, Roger ; Talavera, Gerard ; Bowen, Gabriel J. ; Vila, Roger ; Talla, Valery N. K. ; Collins, Steve C. ; Martins, Dino J. ; Bataille, Clement P. ( December 2023 , Rapid Communications in Mass Spectrometry)

   Many insect species undertake multigenerational migrations in the Afro‐tropical and Palearctic ranges, and understanding their migratory connectivity remains challenging due to their small size, short life span and large population sizes. Hydrogen isotopes (δ²H) can be used to reconstruct the movement of dispersing or migrating insects, but applyingδ²H for provenance requires a robust isotope baseline map (i.e. isoscape) for the Afro‐Palearctic.

   We analyzed theδ²H in the wings (δ²H_wing) of 142 resident butterflies from 56 sites across the Afro‐Palearctic. Theδ²H_wingvalues were compared to the predicted local growing‐season precipitationδ²H values (δ²H_GSP) using a linear regression model to develop an insect wingδ²H isoscape. We used multivariate linear mixed models and high‐resolution and time‐specific remote sensing climate and environmental data to explore the controls of the residualδ²H_wingvariability.

   A strong linear relationship was found betweenδ²H_wingandδ²H_GSPvalues (r² = 0.53). The resulting isoscape showed strong patterns across the Palearctic but limited variation and high uncertainty for the Afro‐tropics. Positive residuals of this relationship were correlated with dry conditions for the month preceding sampling whereas negative residuals were correlated with more wet days for the month preceding sampling. High intra‐siteδ²H_wingvariance was associated with lower relative humidity for the month preceding sampling and higher elevation.

   Theδ²H_wingisoscape is applicable for tracing herbivorous lepidopteran insects that migrate across the Afro‐Palearctic range but has limited geolocation potential in the Afro‐tropics. The spatial analysis of uncertainty using high‐resolution climatic data demonstrated that many African regions with highly variable evaporation rates and relative humidity haveδ²H_wingvalues that are less related toδ²H_GSPvalues. Increasing geolocation precision will require new modeling approaches using more time‐specific environmental data and/or independent geolocation tools.

    

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