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Hello! I’m excited to share my #PhD work on the behavioural ecology of lowland river fishes in the #NorfolkBroads UK in collaboration with @BU_Research, @NaturalEngland, @EnvAgencyAnglia and @Fishtrack1. This is part of the #BESaquaticECRTweets seminar #BESAG2020 (1/12)
I’ll be giving a summary of the past 2.5 years of #acoustic #telemetry data analysis & stable isotope analysis #SIA, aiming to assess how fish use the #NorfolkBroads wetland – a historically well-connected system of rivers, lakes & dykes #letitflow #trackingnotslacking (2/12)
Understanding fish movement is important for freshwater #conservation #restoration. Individuals of the same species may show different tendencies to move/migrate. This variation is an important part of #biodiversity that affects species’ persistence and adaptive potential (3/12)
We used #acoustic #telemetry to track 181 common #bream and 45 #pike for up to 2.5 years throughout the Rivers Bure, Thurne and Ant (~60 km river length).
We also used #isoscapes to predict bream movement based on their stable isotope ecology (4/12)
We also used #isoscapes to predict bream movement based on their stable isotope ecology (4/12)
Tagged bream were lost at a higher rate than expected by natural mortality, but we provide the first suggestion of acoustic tag expulsion in this species.
Loss rate also varied by date of tagging (bream), day of year (bream & pike) & by sex (pike)
https://doi.org/10.1111/jfb.14504 (5/12)
Loss rate also varied by date of tagging (bream), day of year (bream & pike) & by sex (pike)
https://doi.org/10.1111/jfb.14504 (5/12)
Some bream made repeated spring spawning migrations of up to 25 km & individuals were highly consistent in their behaviour (resident/migrant) between years. Is this evidence of #partialmigration and #homing – characteristics for which much-loved salmonid species are famed? (6/12)
We also found tidal phase was a significant predictor of movement, with fish generally travelling in the same direction as tidal flows (7/12)
During spawning, bream social associations were non-random, suggesting the existence of distinct shoals. However, their co-occurrence was not explained by fish length, sex or movement type (resident/migrant) (8/12)
We found dual-isotope (C & N) isoscapes were more reliable at predicting roach foraging locations than single-isotope isoscapes.
Dual-isoscapes were then used to predict bream movement, which correlated with the extent of their subsequent movement recorded by telemetry (9/12)
Dual-isoscapes were then used to predict bream movement, which correlated with the extent of their subsequent movement recorded by telemetry (9/12)
Results suggest the #NorfolkBroads bream population consists of several semi-independent spatially discrete subpopulations which converge during spawning. This diverse space and resource use likely reduces population dependence on a confined spawning/rearing habitat (10/12)
This is important considering stressors in the system such as saline intrusion, blooms of toxic algae #Prymnesiumparvum and planned loss of lateral connectivity due to habitat works https://www.gov.uk/government/news/permit-granted-for-next-stage-in-hoveton-great-broad-restoration (11/12)
Thanks @BES_AquaEco, @NaturalEngland for funding & @EnvAgencyAnglia @Fishtrack1 for fieldwork & resource support. Don’t forget to read https://doi.org/10.1111/jfb.14504 and keep an eye out for future papers. Questions most welcome! #BESaquaticECRTweets #BESAG2020 @BU_Research (12/12)
