**5. Can** *P. vannamei* **potentially compete with native shrimp species?**

Studies have shown that there is a potential risk of a negative impact of the introduced Pacific whiteleg shrimp *P. vannamei* on native species and the invaded ecosystems [21, 30, 44]. An alien species like *P. vannamei* could potentially interact with local species through food competition, either by exploitative or interference competition [21].

Recently, Chavanich et al. [56] conducted a laboratory assessment of feedingbehavior interactions between the introduced *P. vannamei* and five native shrimps plus a crab species in Thailand. Results showed that the shrimp was nonselective with respect to the palatability of the five native shrimps as food. The shrimp was behaviorally dominant when competing for food one-on-one with the native shrimp species. According to Gamboa-Delgado et al. [57], the shrimp is an opportunistic feeder that can adapt well to changes in diet composition. Though laboratory studies could not represent the feeding interactions under field conditions, the non-native shrimp could become a serious threat to native shrimps when the frequency of escapes is increasing and when they begin to reproduce successfully. One of the key factors influencing the success of invading species is propagule pressure or total quantity [58, 59]. Increasing the propagule pressure may enhance the foundation of an invasive population [58]. In Bangpakong estuary, increased frequency of encountering the shrimp is reflecting an increase in propagule pressure because the frequency of escapes is increasing [30]. However, Chavanich et al. [56] suggested

**149**

*Ecological and Social Impacts of Aquacultural Introduction to Philippines Waters of Pacific…*

more studies are needed to provide insights into the interactions between the introduced white shrimp and native shrimp species and into the ecosystem-wide

Diseases are worldwide top issues and challenges in shrimp aquaculture based on the survey of global aquaculture alliance from 2016 to 2017 [60]. Modern shrimp farming is, in a way, shaped by viral disease outbreaks in the nineties and early 2000s [61]. On the other hand, Itsathitphaisarn et al. [62] reiterated that viral pathogens pose a primary threat to global shrimp aquaculture. According to Lightner and Redman [63], there are about 20 viral pathogens that can cause serious epizootics in penaeid shrimp. In the Philippines, major viral pathogens affecting the shrimp aquaculture include white spot disorder infection (WSSV), monodon baculovirus (MBV), irresistible hypodermal and hematopoietic rot infection (IHHNV), hepatopancreatic parvovirus (HPV), yellow head infection (YHV), and Taura disorder infection (TSV) [61]. A disease caused by TSV was first described from Ecuador in the early 1990s. Lightner [64] and Lightner [65] reported that the disease outbreaks caused catastrophic losses with cumulative mortality rates of 60 to >90% in pond-cultured shrimp. The principal host species for TSV are the *P. vannamei* and the *P. stylirostris*, and it has been documented in all life stages (i.e., post-larvae, juvenile, adults) of *P. vannamei* except in eggs, zygote, and larvae [66]. TSV is a particularly virulent

shrimp species including *P. monodon*, *P. aztecus*, *P. duorarum*, *Litopenaeus setiferus*, *L. stylirostris*, *Marsupenaeus jaiponicus*, *Macrobrachium rosenbergii*, *Metapenaeus* 

According to Wertheim et al. [67], TSV is now widely distributed in the shrimpfarming regions of the Americas, Southeast Asia, and the Middle East. Additionally, evidence showed that TSV is present in natural populations of *P. vannamei* in Central America such as Mexico and Ecuador and may be elsewhere [66, 68]. The international trade of live shrimp resulted in a rapid spread of TSV in the Americas and Asia [69]. TSV was introduced to Asia in 1998 by careless importation of shrimp stocks for aquaculture but has not been reported to cause problems with local crustacean species [70]. Recently, Thitamadee et al. [71] reported TSV has become innocuous due to the widespread use of highly tolerant specific-pathogen-

In the Philippines, there was no documentation on the introduction of *P. vannamei* from Panama into Iloilo in the 1970s and from Hawaii in 1990, and it was not known whether the exotic species introduced any new pathogens [18]. As of 2015, there was no documented report regarding TSV presence in the Philippines [61] and have yet to be detected as stated in the NACA, OIE, and FAO [72] quarterly animal disease report of 2018. However, this will not justify that TSV is not present in the Philippines because there was no study conducted on the detection of the viral disease since the introduction of *P. vannamei* until the importation ban was lifted in 2007 up to 2018. Rosario and Lopez [36] reported that even with the strict implementation of the BFAR formulated FAO 207 series of 2001 which further strengthened FAO 189 series of 1993 which among others prohibit the importation of exotic shrimps and strict surveillance in airports, traders were finding other ways in bringing the illegal shrimp inside the Philippines without passing through the airports. Shrimp Importation, Monitoring, and Surveillance (SIMS) team spearheaded six major confiscations in late 2002 up to 2003 and reported around 700

**6. What is the extent of the geographic spread of the alien** 

pathogen of *P. vannamei*, and it can infect several other

free (SPF) stocks of *P. vannamei* that dominate production.

*ensis*, *Fenneropenaeus chinensis*, and *L. schmitti* [61].

*DOI: http://dx.doi.org/10.5772/intechopen.91775*

consequences of this introduction.

**pathogen, TSV?**

*Ecological and Social Impacts of Aquacultural Introduction to Philippines Waters of Pacific… DOI: http://dx.doi.org/10.5772/intechopen.91775*

more studies are needed to provide insights into the interactions between the introduced white shrimp and native shrimp species and into the ecosystem-wide consequences of this introduction.
