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- Comparative study of Ruditapes philippinarum and Ruditapes decussatus in Ria de Aveiro, Portugal: Invasive species management and marine resource conservationPublication . Manuel da Silva Rodrigues Maia, Francisco; Gaspar, Miguel; Barroso, Carlos M.Research on the biological traits of commercial bivalves is essential for developing effective management strategies and ensuring their sustainable exploitation. This study offers a comparative analysis of the invasive Manila clam R. philippinarum and the native grooved carpet clam R. decussatus in the Ria de Aveiro, Portugal, focusing on shell morphometry, growth, reproductive cycle, condition index, and length at 50% maturity (L50). Analysis of internal shell microgrowth bands revealed that R. philippinarum exhibits a higher growth coefficient (K) than R. decussatus, with von Bertalanffy growth equations of Lt = 59.49 [1 - e -0.78 (t-0.55)1 and Lt = 75.09 [1 - e -0.33 (t0.10)1, respectively. Notably, the K value for R. philippinarum is among the highest recorded for this species, indicating exceptional growth performance in the Ria de Aveiro. The reproductive cycle analysis showed that R. philippinarum has a longer and more intense spawning period, extending from April to October 2013 and from April to September 2014, with peaks in August and September. In contrast, R. decussatus exhibited a shorter spawning season, from May to October 2013 and from June to September 2014, peaking in August. Seasonal variations in the condition index, likely linked to food availability and reproductive cycle, showed R. philippinarum in better condition during the early stages of gonadal development, indicating more efficient energy allocation towards reproduction. Rapid growth and fast sexual maturity during the first year of benthic life enable recruits of both species to spawn during the following year's spawning season. R. philippinarum reaches sexual maturity slightly faster than R. decussatus (L50 = 20.0 mm SL vs. L50 = 22.1 mm SL), maturing at around 1.08 years compared to 1.15 years. Although this difference is minor, it enables R. philippinarum recruits to begin reproduction approximately one month earlier in the year. Improved growth rates of R. philippinarum during its second and third years likely enhance reproductive capacity, as larger individuals typically produce more offspring. These results suggest that R. philippinarum has a competitive advantage over R. decussatus due to its faster growth and greater reproductive potential. However, these factors do not conclusively explain the rapid proliferation and establishment of R. philippinarum in the Ria de Aveiro, nor the sudden decline in R. decussatus populations following the introduction of the invasive species. Fishery management strategies are proposed based on two distinct scenarios.