Ecologia populacional e dinâmica pesqueira de Anomalocardia flexuosa (Linnaeus, 1767) (BIVALVIA: VENERIDAE) em um estuário hipersalino do semiárido brasileiro

Abstract

The present work was developed with the objective of analyzing the population dynamics of Anomalocardia flexuosa in a hypersaline estuary off the coast of the white coast in Rio Grande do Norte. During the period from November 2015 to October 2017 samples of biological material, sediment for particle size analysis, and abiotic parameters (salinity and temperature) were collected in 3 different areas of the Apodi/Mossoró estuary. An innermost area 9 km from the mouth (A), an intermediate area (B) and an area in the mouth of this estuary (C). The salinity showed a decreasing inverted pattern inside the estuary, where the highest values of salinity were recorded in A. The granulometric characterization differed between areas and presented a higher percentage of silt and clay in area B and greater percentage of sand in area C. The density of A. flexuosa differed between areas, where A presented always the highest values, registering up to 4,728 ind / m2, and C the lowest, with an average of 370 ind / m2. The precipitation showed a positive correlation with the density of A. flexuosa. Hypersalinity did not limit the distribution and abundance of the species, however, space competition with a prairie of Halodule wrightii, established in C, restricted the distribution and density of A. flexuosa. Growth was considered fast with a short life cycle. The morphological sexual maturity size was 13.8 mm and agrees with that recorded in the literature. Recruitment was constant, but with periods of greater representativeness and abundance of recruits regulated by the survival of adults as a result of competition for space and resource. Thus, abundance of A. flexuosa also interfered in the structural processes of this population, causing effects of dense dependence. Natural mortality was higher than fishing mortality and the current rate of fishing operation did not exceed the maximum limit borne by the species. However, future projections of increased farm rate indicate low productivity. The community of bacteria associated with A. flexuosa was different from the microbiota of the water and the bivalves Tivela mactroides and Phacoides pectinatus and the hypersalinity did not interfere in the composition of the A. flexuosa microbiome. Thus, the species presents a wide tolerance to the variations of several abiotic factors, however, biotic factors such as competition and predation by fishing may be influencing the structure of this population.