Ostreicultura no nordeste paraense: estado atual e perspectivas futuras

Abstract

In the first article (Chapter 1), aspects related to the oyster culture supply chain in the state of Pará were evaluated. Between 2013 and 2014, research was carried out in seven associations involved in oyster culture through interviews with the president of each association, as well as with 56 members (72% of the total). Secondary data were obtained with the permission of management reports from the Brazilian Micro and Small Business Support Service of the State of Pará. The associations Agromar, Nova Olinda and Aquavila, Lauro Sodré stand out from the rest due to their larger on-growing areas and total production in 2013. However, smaller associations are more efficient with higher production per unit area. Although associations have grown in numbers since 2006, along with increased capacity and output due to government assistance, compared to other regions of Brazil, they need to be better organized internally. Associations should be less reliant on public funding and develop more partnerships with private enterprise. In addition, there must be active co-participation in the development of legislation and public policies that regulate oyster culture and the protection of natural oyster beds. In the second article (Chapter 2), the present study investigated the physico-chemical characteristics of water at all oyster farming units in Pará. Salinity, temperature (oC), oxidation-reduction potential (mV), pH, dissolved oxygen (mg.l-1), depth (m) and the concentration of chlorophyll-a (mg.m3) were measured in situ in both the dry season of 2013 and the rainy season of 2014. All variables, except depth, were significantly higher in the dry season. Mean salinity, which ranged from 2.4 to 46, is the most important variable that explains the variation between associations in relation to the season, date of sampling in each season and state of the tide. However, dissolved oxygen, pH and depth were also important.Oyster culture units in Pará can be defined in terms of water quality as suitable for harvesting xxii seed from the wild (lower salinity and pH), or for on-growing of adults (higher values of salinity, pH and depth). In the third article (Chapter 3), settlement, seed size, larval development in the laboratory, growth and aspects of the commercialization of cultivated oysters were investigated from 2012 to 2016 in five culture units in pará, during periods varying from 6 to 12 months. Seed length differed between December 2014 (21 mm) and April 2015 (12 mm) and smaller size appears associated with higher precipitation. Native seed numbers were higher in the on-growing area whereas abundance of exotic seed was low. Larval development is best at salinities of 16 and 21, in which the pediveliger stage appeared after 53 days. Oyster growth in culture was variable, but market size was reached in at least 4 months at Agromar, Aappns and Asapaq. Mortality ranged from 19% to 46%, comparable to other C. gasar cultures. Oyster mass varies monthly and between crops, and is related to pre-sale size selection. On average, oysters in the Baby and Médio classes are 77% and 80% shell. Aquavila is suitable for harvesting seed, whereas Agromar has the lowest mortality and is suitable for on-growing. Most of the oysters sold at Agromar are within the class limits, whereas those sold at Aquavila are larger.