World Aquaculture 53 cerning the peripheral and unintended impacts attributed to this non-native species. Impacts are generally based on three major attributes: omnivorous diet, disease vector and behavioral damage (Geiger et al. 2005). The omnivorous diet of the Procambarus has been reported to cause rice yield depression and wild habitat alteration (Gutiérrez et al. 1998), both impacts documented in their native range. The role as a possible vector of Aphanomyces is likewise accepted, as Procambarus has developed host resistance to this infection by co-evolving with the fungal agent. The behavioral impacts of Procambarus are centered on either their burrow damage to irrigation infrastructure or competitive aggression /exclusion with other aquatic invertebrate populations. Secondary impacts to terrestrial vertebrates are mixed between positive and negative, with many consumers of crayfish benefiting from their availability as a dietary item (Delibes and Adrian 1987). Commercialization of Spanish Procambarus Since 1973, commercial Procambarus production in Spain has stabilized within the region of Las Marismas, with harvest tied to local rainfall abundance (de Andalucía 2001). Ranging yearly from 3000-5000 t (live weight) of marketable animals, annual production during the 2000 season indicates that over four percent of the global Procambarus harvest comes from descendants of the initial 100 kilograms of viable broodstock introduced from North America. Such harvest potential places Spain third behind USA and unrivaled global leader, China (Figure 2). Far eclipsing the combined production in the native range of USA and introduced Spain, non-native Chinese Procambarus are harvested predominately from large volunteer populations in waterways similar to the situation in southern Spain (Figur 3, Liu and Li 2009). By 2000, the Spanish crayfish sector was centered near the town of Isla Major, centrally located in the rice-growing region of Andalucía. With eight crayfish processing companies employing some 700 workers, a good proportion of the product value of US$13 million Fig. 1. Crayfish trade reversal (t) between Spain and France. Fig. 2. Harvested Procambarus from three major producing countries in 2006. Fig. 3. Development of the China Procambarus harvest (t) by year. Fig. 4. Marketing of Spanish Procambarus into whole (dark) and tail meat (light) products (t) in 2006. is returned to the local economy, with US$7 million in salaries. Of note is the estimate that 30 percent of processed product within these plants is from traditional marine shrimp species. While the majority of the incoming Spanish Procambarus product is destined to be marketed whole (live, chilled or frozen), over 32 percent of product is cooked and peeled for
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