Growth parameters of the invasive gastropod Melanoides tuberculata (Müller, 1774) (Gastropoda, Thiaridae) in a semiarid region, Northeastern Brazil

ABSTRACT

Melanoides tuberculata has invaded several aquatic ecosystems in the Neotropical region. This species shows high adaptive capacity and plasticity, establishing itself in several basins, promoting negative impacts on environments and native species. Here, we determine the growth parameters and the population structure of this species, in a semi-arid environment, in Northeast Brazil (Pernambuco state). Monthly captures were conducted at three types of substrate site 1 soft bottom with macrophytes, site 2 soft bottom without macrophytes, and site 3 gravel and rocks. Shells were classified as occupied or empty, and their shell length (SL) and opening width (SW) were measured. The growth parameters of the von Bertalanffy’s model were estimated from the size-length frequency distribution using the ELEFAN I. Also, the maturity was verified, through the size at onset of maturity (SOM - 14.85 mm SL) proposed in the literature. A total of 1,013 individuals were collected, with shells varying from 7 to 39 mm SL and mean density of 84.42 (± 3.86) individuals m-2. The substrate with the largest number of mollusks was the site 1. Largest amount of empty shells was detected at site 3. Growth of M. tuberculata indicates rapid increment, with k = 0.56, L∞ = 42 mm and t0 = -0.26 years. The mean estimated age for the species was 0.95 years. According to the SOM, 86% of individuals sampled were considered mature.