Recent change in spatial distribution of the European flat oyster (Ostrea edulis) inferred from field data and empirical models of living oysters and empty shells

Abstract

Marine coastal areas are increasingly affected by human activities resulting in changes in species and habitat distributions. Understanding these patterns and its causes and consequences is important for conservation and restoration of such changing habitats. One habitat that has been heavily affected by human use are the North Sea oyster beds which once were abundant but have lost large parts of its coastal distribution due to overexploitation. Based on data of living and dead assemblages of Ostrea edulis collected using video transects, we used an ensemble modeling technique to model and predict current and recent distribution of O. edulis along the Swedish west coast where its distribution is, in relative terms, still rather unaffected. We could detect a recent change in the distribution of O. edulis along the coast which to a large extent could be attributed to a change in depth distribution, suggesting that the population of O. edulis have a slightly shallower distribution today than in the past. Although a potential mismatch between living and dead assemblages, caused by a complex combination of biological and environmental conditions, needs to be considered in the interpretations drawn, it may be a way around the lack of suitable background data in management decisions. This provides important information for management and conservation of the native oyster beds. Furthermore, this study illustrates a method for identifying recent changes in species distribution using dead assemblages of bivalves.

Site selection for European native oyster (Ostrea edulis) habitat restoration projects: An expert‐derived consensus

“…In the European context, however, O. edulis habitats have all but disappeared and evidence of the historical distribution of O. edulis , in particular in offshore sites, is extremely challenging to obtain (Bennema, Engelhard & Lindeboom, 2020). Even inshore, determining the exact age of extinction of historical native oyster beds can present a significant challenge, as shell material can persist for millennia, and written records from locations distant to key trading ports is often scant (Fariñas‐Franco et al, 2018; Bergström, Thorngren & Lindegarth, 2022). Nevertheless, there is significant evidence that oyster beds were extremely widely distributed throughout the North Sea (Gercken & Schmidt, 2014; Bennema, Engelhard & Lindeboom, 2020; Sander et al, 2021), and in many coastal estuaries where they are no longer in evidence (Beck et al, 2011 ) .…”

Climatic Variability Caused by Topographic Barrier Prevents the Northward Spread of Invasive Ageratina adenophora

“…The predictive power of modeling varies due to the use of different algorithms and data processing methods [23]. The ensemble modeling approach combined with several algorithms is an increasingly used method, which can avoid uncertainty caused by model selection and obtain more reliable predictions [24]. In this study, GLM, GBM, RF, and MaxEnt were combined, and the AUC and TSS statistics results (0.96 and 0.82, respectively) showed that the final ensemble model had good discriminability for predicting A. adenophora distribution.…”