An individual-based dataset of carbon and nitrogen isotopic data of Callinectes sapidus in invaded Mediterranean waters

Salinity patterns and local migration determine the isotopic composition of the invasive blue crab, Callinectes sapidus, along the Spanish Mediterranean coast

δ13C and δ15N patterns of the blue crab, Callinectes sapidus, and its potential diets, were investigated in eleven localities within four invaded regions of the Spanish Mediterranean (Catalonia, Valencia, Alicante, and Murcia) subjected to contrasting salinities and degrees of connectivity with the open sea. These regions host blue crab fisheries of variable importance that might be regulated by availability of food resources and local environmental conditions. When present, large adults and immature, subadult sizes of each sex were captured to evaluate possible differences associated to age movement across habitats. SIBER and MixSIAR were used to assess patterns of isotopic niche and dietary contributions. Results showed significant effects for all factors and interactions (except for Sex and Sex x Size in δ15N). The effect size in Region (ηp2 = 0.82 and 0.70, respectively for δ13C and δ15N) and Locality (ηp2 = 0.53 and 0.46), was substantially greater than that of crab Size (ηp2 = 0.37 and 0.21) and Sex (ηp2 = 0.06 and 0.02), concurring with increasing levels of isotopic niche overlap (9% and 11% in Locality and Region, 32% in Size and 44% in Sex). MixSiar results indicated strongly variable contributions from food sources at each locality (TPs from 2.3 to 3.6), but with higher quantity of fish, algae, and crustaceans (27.7%, 18% and 15.1%). Dietary results showed little relation with isotopic patterns, whereas significant associations were found between local salinities and signatures in both crabs (R2 = 0.518 and 0.757, for δ13C and δ15N) and diets. Overall, our study suggests that blue crab habitat use in small Mediterranean estuaries might largely differ from native areas, with movements being mostly restricted to young individuals and/ or certain localities with higher connectivity with the open sea (e.g., the Ebro River). Salinity conditions emerge as a major variable shaping isotopic patterns of populations on a large scale.

Isotopic variability of the invasive blue crab Callinectes sapidus in the Gulf of Cadiz: Impacts and implications for coastal ecosystem management

The variability in trophic position and carbon isotopic signatures can provide information about their dietary flexibility and its ability to adapt to changing environmental conditions. The impact of the invasive blue crab Callinectes sapidus was assessed by estimating its trophic position and isotopic niche using stable isotopes (δ1³C, δ1⁵N, δ³⁴S) across different invaded Atlantic coastal areas. This study, the first of its kind in the eastern Atlantic range, reveals the crab's omnivorous behavior with a wide trophic position (TP = 2-4), consistent with findings from its native range. Significant spatial variability in trophic roles was observed between habitats, with salt marshes showing enriched δ1³C and lower TP due to differences in primary producers like Spartina detritus and phytoplankton. Estuaries exhibited higher and broader δ1⁵N and TP ranges, influenced by prey availability and anthropogenic nitrogen inputs, that implies a significant impact on marine benthic and pelagic animal communities. Seasonal changes in the Guadalquivir estuary, linked to overwintering and brooding migrations, showed sexual differences in isotopic signatures, with males more enriched in δ1⁵N than females, indicating varied prey availability or metabolic differences. Overall, the Atlantic invaded range displayed broader and lower TP compared to the Mediterranean, underlining the blue crab's flexible and diverse trophic role across different habitats and trophic levels. The variability in trophic position and carbon isotopic signatures reflects the dietary flexibility of this invasive species and its potential effects on native fauna. These findings emphasize the need to consider trophic interactions in ecosystem management and conservation efforts.

When Nature Requires a Resource to Be Used-The Case of Callinectes sapidus: Distribution, Aggregation Patterns, and Spatial Structure in Northwest Europe, the Mediterranean Sea, and Adjacent Waters

The Atlantic blue crab Callinectes sapidus, which is native to the western Atlantic coast and listed among the 100 most invasive alien species in the Mediterranean Sea, is attracting a great deal of interest because of its rapid colonisation of new areas, the significant increase in its population, and the impacts it may have on ecosystems and ecosystem services. Outside its natural distribution range, the species was first found on European Atlantic coasts in the early 1900s and was introduced into the Mediterranean Sea a few decades later, probably through ballast water. Currently, it is found in almost the entire Mediterranean Basin and is also expanding into the Black Sea and along the north African and Iberian Atlantic coasts. Based on a systematic review of C. sapidus occurrences, this study describes its distribution, aggregation patterns, and spatial structure in Northwest Europe, the Mediterranean Sea, and adjacent waters through a series of ecological indicators elaborated using GIS spatial-temporal statistics. The main results highlight that the species is expanding in the Mediterranean and adjacent waters, while in northern Europe, the population remains confined in some areas. Furthermore, the main species detection methods are analysed, finding that traps and nets are the most frequently used methods, and management suggestions are provided.

Individual and population-scale carbon and nitrogen isotopic values of Procambarusclarkii in invaded freshwater ecosystems

Background

Freshwater ecosystems are amongst the most threatened habitats on Earth; nevertheless, they support about 9.5% of the known global biodiversity while covering less than 1% of the globe's surface. A number of anthropogenic pressures are impacting species diversity in inland waters and, amongst them, the spread of invasive alien species is considered one of the main drivers of biodiversity loss and homogenisation in freshwater habitats.Crayfish species are widely distributed freshwater invaders and, while alien species introductions occur mostly accidentally, alien crayfish are often released deliberately into new areas for commercial purposes. After their initial introduction, crayfish species can rapidly establish and reach high-density populations as a result of their adaptive functional traits, such as their generalist diet.The Louisiana crayfish Procambarusclarkii (Girard, 1852) is globally considered one of the worst invaders and its impact on recipient freshwater communities can vary from predation and competition with native species, to modification of food webs and habitat structure and introduction of pathogens. Native to the south United States and north Mexico, P.clarkii has been introduced in Europe, Asia and Africa, determining negative ecological and economic impacts in the majority of invaded habitats where it became dominant within the receiving benthic food webs. Due to its flexible feeding strategy, P.clarkii exerts adverse effects at different trophic levels, ultimately affecting the structure and dynamics of invaded food webs. It is, therefore, paramount to evaluate the ecological consequences of P.clarkii invasion and to quantify its impact in a spatially explicit context.

New information

In the past decades, the analysis of stable isotopes of carbon, nitrogen and other elements has become a popular methodology in food web ecology. Notably, stable isotope analysis has emerged as a primary tool for addressing applied issues in biodiversity conservation and management, such as the assessment of the trophic ecology of non-indigenous species in invaded habitats. Here, we built two geo-referenced datasets, resolved respectively at the population and individual scale, by collating information on δ¹³C and δ¹⁵N values of P.clarkii within invaded inland waters. The population-scale dataset consists of 160 carbon and nitrogen isotopic values of the Louisiana crayfish and its potential prey, including living and non-living primary producers and benthic invertebrates. The dataset resolved at individual scale consists of 1,168 isotopic records of P.clarkii. The isotopic values included within the two datasets were gathered from 10 countries located in Europe, Asia, Africa and North America, for a total of 41 studies published between 2005 and 2021. To the best of the authors' knowledge, this effort represents the first attempt to collate in standardised datasets the sparse isotopic information of P.clarkii available in literature. The datasets lend themselves to being used for providing a spatially explicit resolution of the trophic ecology of P.clarkii and to address a variety of ecological questions concerning its ecological impact on recipient aquatic food webs.