These marine protected areas are also not aligned with such fish species’ core habitat, it adds
A river lamprey, one of the species studied by the researchers. Photo: iStock
A new study has found that 62 per cent of Marine Protected Areas (MPAs) dedicated to protect rare migratory fish species fall outside their core habitats.
The study, published in the British Ecological Society’s Journal of Applied Ecology, found that MPAs designated to protect diadromous fish species did not align with their core habitats.
Diadromous fish are those which migrate between saltwater and freshwater environments.
Only 55 per cent of modelled core habitats identified for diadromous fish overlapped with the MPAs. Of these protected areas, only half had measures in place for the protection of the fish, according to the study.
The scientists tested 11 rare and data poor diadromous fish: the allis shad (Alosa alosa), twait shad (Alosa fal- lax), Mediterranean twaite shad (Alosa agone), the European eel (Anguilla anguilla), the European flounder (Platichthys flesus), the river (Lampetra fluviatilis) and sea lamprey (Petromyzon marinus), Atlantic salmon (Salmo salar), sea trout (Salmo trutta), the thinlip mullet (Chelon ramada) and smelt (Osmerus eperlanus).
They were observed during their at-sea migration in the southern North Sea, Bay of Biscay, French Mediterranean waters and the English Channel.
The researchers implemented their newly developed modelling approach on diadromous fish due to a lack of knowledge about their at-sea life history stage and no existing model of their distribution.
Diadromous fish are sensitive to anthropogenic pressures. They are subjected to terrestrial, freshwater, and marine pressures such as agricultural and pollutant runoffs, habitat destruction, barriers to migration, fishing, bycatch, and climate change.
Barriers to migration like dams, weirs and locks have a collective impact as these fish move between freshwater and marine habitats throughout their life cycle.
Not matching up
The researchers analysed specific individual species and found that less than 30 per cent of endangered species such as Mediterranean twaite shad (Alosa agone) dwelt in core habitat within MPAs.
Another revelation was that though species such as the European eel and European smelt had nearly 70 per cent of their core habitats within MPAs, only nine per cent of these MPAs had specific steps to protect the European eel and no measures existed to protect the European smelt.
In a press statement shared by the British Ecological Society, Sophie Elliott of the Game and Wildlife Conservation Trust and lead author of the study, said, “We found that existing MPAs with and without measures to protect listed diadromous fish across France, England, Belgium, and the Netherlands are not adequately protecting them despite a number of these fish being protected.”
She added that given the sharp decline in diadromous fish which was noted just last week by The Living Planet Index (LPI) for the Migratory Freshwater Fishes 2024 Update, it is a surprise more isn’t being done to protect these species.
Laurent Beaulaton, also at the French Biodiversity Agency and a co-author, said, “We hope that our ‘Combined Model for Accurate Prediction’ methodological framework can help improve accurate rare species distribution modelling for reliable biodiversity assessments, meaning conservation measures can be targeted in specific areas that protect rare and poorly detected species while also minimising conservation impacts on human activity.”
The researchers emphasised that the modelling approach devised by them could be applied on other protected, threatened and rare species in contexts where protected areas have been designated for their conservation.
The study found that MPAs are set up with an absence of data on rare and threatened species habitats (in this case diadromous fish) and this modelling can help fill these data gaps.
Regarding climate change impacting these species, Elliott told Down To Earth on email, “Research has found more Northerly shifts in the at-sea migration pattern of these species. Severe climate change effects (such as population declines) have been observed in more southerly populations. Changes in their timing of migration have also been observed which may have knock-on consequences for progeny survival and or food availability.”
She added that the authors are currently involved in a new project (EU DiadSea project) to apply the modelling CMAP framework (used in this study) to diadromous fish at sea and improve understanding of climate change effects on these species.
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