Assessment of the fishing unit of effort in a coastal artisanal fishery in Manzanillo, Colima, Mexico

From February 1992 to April 1993 a daily sampling was carried out in the port of Manzanillo, Colima (Mexico), in order to obtain information an boats, fishing gear and fishing effort. The coastal fishing system presents a high diversification; therefore, a strategy was elaborated to determine which is the best measure of effort that could be used in the coastal fishery management. A time-series analysis was carried out to establish the appropriate temporary level and the monthly grouping was the most appropriate. Models of simple and multiple regression were adjusted, as well as analyses of residuals for three measures of fishing effort: fishing time, number of fishermen and number of trips. Of these three measures, the number of trips and the hours of fishing are the ones that best represent the fishing effort. The use of variables in a model of multiple linear regression is a better indicator; however, the increase of the explained variance is not significant and this model increases the complexity of the design and handling of the information. Although the information analyzed was obtained during an El Nino, it is considered that this phenomenon did not affect the results, because the use of total catch disguises specific effects. The use of the fishing trip is recommended as the best measure of the effort, in terms of its statistical validity and the simplicity for obtaining it. This approach is a basic requirement for the structuring of a system to study a fishery.