Red swamp crawfish Procambarus clarkii is native to north-eastern Mexico and the south-central USA, and it has been introduced worldwide becoming the most widespread crawfish in the world (Gherardi 2008, Tablado et al. 2010). The species was legally introduced by the central government in 1974 in the Bajo Guadalquivir rice fields for commercial reasons and its natural expansion was enhanced by fishers and promoted by the Spanish Government (Alcorlo et al. 2008) being today present throughout almost all the Iberian Peninsula. There is no evidence of scientific studies at that time assessing its possible impacts.

Freshwater species are generally not considered as professional fishing resources in Spain; nevertheless the red swamp crawfish in the Guadalquivir Delta is an exception due to the socio-economic importance of the crawfish processing industry in Seville province grouped since 2011 in a single association (Pebagua). Fishing is only allowed only in the marshes and rice fields of 13 municipalities within the Guadalquivir Delta (Junta de Andalucía, 2014). Authorized fishers must be in possession of a a generalist recreational licence given by the Junta de Andalucía and they have to be registered as providers of one of the processing factories. Fishing in done on foot in the marshes, no boat is needed, instead fishers move by car setting and collecting the traps, and all the catches have to be sold to the processing factories. As most of the fishing in this area happens in rice fields or their irrigation channels, the fishing campaign is closely linked to the rice culture cycle; on an average year rice fields are flooded in May and by the end of September the water level starts descending, so the rice can be finally harvested in October. The red swamp crawfish fishing season lasts approximately for three months, starting in August and finishing in October-November.

In 2013 there were 419 registered fishers in Andalusia, and the four factories grouped under a single processor’s association (Pebagua) processed 4,600 tons of crawfish (3,000 tons caught in Andalusia) (Pebagua, personal communication). Spain is the 3rd largest producer of P. clarkii in the world after China and the USA, selling 8-10% of the world commerce.