Invasion
Invasion Description
1st Record: Moanolua, Oahu/HI/Pacific Ocean (1905, Brock 1960)
Geographic Extent
Moanolua, Oahu/HI/Pacific Ocean (1905, Brock 1960); HI/'freshwaters of all the islands (Brock 1960); 'throughout Oahu'/HI/many streams (England et al, 2000, 'up to 41 ppt in Nanakuli Stream'); Hawaii/HI/3 of 6 wetlands sampled (2009, MacKenzie and Bruland 2012, 0.1-14.6 PSU); Kauai/HI/6 of 8 wetlands sampled (2009, MacKenzie and Bruland 2012, 0.1-19.8 PSU); Maui/HI/3 of 6 wetlands sampled (2009, MacKenzie and Bruland 2012, 0.14-14.3 PSU); Molokai/HI/4 of 5 wetlands sampled (2009, MacKenzie and Bruland 2012, 9.7-61.6 PSU); Oahu/HI/9 of 13 wetlands sampled (2009, MacKenzie and Bruland 2012, 0.5-101.7 PSU); Hawaiian Island/HI/anchiahaline ponds (Marrack 2016)
Vectors
| Level | Vector |
|---|---|
| Probable | Biocontrol |
Regional Impacts
| Ecological Impact | Predation | |
| Gambusia affinis is a predator on the native Hawaiian shrimp Halocaridina rubra. However, in the presence of G. affinis, the shrimp is active only at night, minimizing predation (Capps et al. 2009). | ||
| Ecological Impact | Competition | |
| When the two species are present together in brackish ponds in Hawaii, Gambusia affinis and the native Hawaiian shrimp Halocaridina rubra both feed largely on periphyton algae, since the major potential animal prey for G. affinis, the shrimp, are only active at night. Consequently, both species are grazers on algae on the rocks, G. affinis by day, and H. rubra by night (Capps et al. 2009). | ||
| Ecological Impact | Herbivory | |
| In brackish ponds in Hawaii, Gambusia affinis feeds largely on periphyton algae, and has a trophic position of 2.2 (Capps et al. 2009). | ||
| Economic Impact | Fisheries | |
| Inroduced mosquitofish threaten traditional fisheries for the native Hawaiian shrimp Halocaridina rubra (opae’ula). Eradication attempts, using rotenone, have been unsuccessful (Nico and Walsh 2011) | ||