Growth patterns of the invasive crab Cronius ruber (Brachyura, Portunidae) in the Canary Islands (Central-East Atlantic)

The growth pattern, including the moult process, relative growth, and estimation of von Bertalanffy growth parameters of the invasive non-indigenus species (NIS) Cronius ruber were studied in the Canary Islands. Despite being found in both, native and invaded areas, the life cycle and ecology of this species remain unknown. The study revealed a greater abundance of females than males, with males exhibiting larger carapace sizes and weights than females. Throughout ontogeny, relative growth was observed, with males reaching carapace widths (CW) between 54.5 and 57.8 mm and females reaching 49.9 mm CW. Allometry in the growth of the males’ chelae and females’ abdomen was consistently positive. Cronius ruber was found to be a fast-growing species, reaching the postpubertal growth phase (maturity) between 0.5 and 1 year of age in males and between 0.4 and 0.8 years in females. The intermoult period increased by more than 638 % in males and 443 % in females with age. Individuals undergo 13 moults during the first phase of life (until 30 mm CW) and then reduced to 6 moults until the end of life, concluding with a final terminal moult. The lifespan until the terminal moult is approximately 2.5 years, followed by a survival time over 1.5 years. von Bertalanffy growth parameters estimated using monthly CW-frequency data for males (L ∞ =97.4 mm CW, k=1.89 years −1 , t o =0.31 years), and for females (L ∞ =86.72 mm CW, k=1.91 years −1 , t o =0.29 years). Similar results were obtained using growth increment data. • The intermoult period increases by more than 638 % for males and 443 % for females with age. • The intermoult lasts 26–32 days for smaller individuals (30–39 mm CW) and 166–142 days for larger individuals (70–79 mm CW). • The ecdysis process occurs in an average time of 3.3±0.8 hours. • Ontogenetic change in the growth correspond to the inflection point between the pre- and postpubertal growth phases. • The postpubertal growth phase begins between 0.5 and 1 years old in males and between 0.4 and 0.8 years in females. • Cronius ruber has 13 moults during the first phase of life 25 mm CW) and from then there are only 6–7 moults. • C ronius ruber has terminal moult. • Lifetime to terminal moult was estimated at 2.5 years and subsequent survival time at more than 1.5 years.