Aspectos populacionais, habitat, preferência alimentar e exploração de Cassis tuberosa (Gastropoda: Cassidae): implicações para a conservação e manejo

• Autor(a) principal: Mota, Ellori Laíse Silva
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/123456789/18233
• topic: Microhabitat; Estoques populacionais; Preferência por presa; Taxa de consumo; Cadeia de comércio; Conservação; Microhabitat; Population stocks; Prey preference; Consumption rate; Trade chain; Conservation; CNPQ::CIENCIAS BIOLOGICAS::ZOOLOGIA

The marine gastropod Cassis tuberosa is a large species that, due to its shell morphological characteristics in all stages of life and reach up to 30 cm in total shell length, is the target of capture to supply the international shell trade. The species is not on the IUCN (International Union for Conservation of Nature and Natural Resources) list. In local assessments such as the Colombian Caribbean, the species has been listed in the Red Book of Threatened Species as Vulnerable (VU), and in Brazil the species is classified as Near Threatened (NT). In general, studies of the species C. tuberosa are limited to records and information about biology and ecology of gastropod. The species is cited basically as a component of marine benthic communities and as a component of commercialized fauna. Given this, the present study aimed to study population, habitat and natural aspects of Cassis tuberosa, and to analyze the fishing and trade of this target gastropod, as well as to provide recommendations for the species management. Chapter I is the first effort to map and evaluate populations of this species in a coastal line of Northeastern Brazil. The population densities of the present study are among the highest ever recorded for the species throughout its distribution. On the other hand, there is a deficit of adult individuals in the population, which are the main targets of the shell trade. The species presents greater selectivity of soft substrates, such as sand, gravel and clay, essential components for the burying habit, which represents the predominant diurnal behavior of the species. Chapter II analyzed the food preference of the gastropod experimentally, and showed that C. tuberosa preferred the sand-dollar Mellita quinquiesperforata, and showed size selectivity for the biggest prey. The drilling were predominantly made on the oral surface and peristomial region. The predator C. tuberosa has a higher activity rate in the early hours of the night, being strictly related to foraging behavior. Chapter III characterizes the catch and trade chain of C. tuberosa, and aspects of fishermen's traditional ecological knowledge of the species. The gastropod suffers capture pressure associated with fishing activities related to other target resources such as fish, lobsters and octopuses. Along the trade chain of the species, the use of the shell for ornamental purposes is the most widespread, and this demand is enhanced by the intensity of tourism in the region. Knowledge about species capture and treatment techniques is transmitted vertically in the community. Local ecological knowledge indicates to population decline over time and attributes such decline to increased capture. Chapter IV presents the first recommendations of actions for management of C. tuberosa based on analysis of existing data on the species. Therefore, a total prohibition on the capture of individuals independently of shell size is recommended, considering illegal the practice of capturing and selling of the specimens in all aspects; effective monitoring of fishing landings mainly resulting from fishing for other resources such as fish, octopus and lobster in order to curb the improper exploitation of the gastropod; and the continuous development of scientific research, as well as mapping and monitoring of population stocks throughout the species distribution.