Marine dispersal determines the genetic population structure of migratory stream fauna of Puerto Rico: evidence for island-scale population recovery processes

Cook, Benjamin D.; Bernays, Sofie; Pringle, Catherine M.; Hughes, Jane M. 2009. Marine dispersal determines the genetic population structure of migratory stream fauna of Puerto Rico: evidence for island-scale population recovery processes. Journal of the North American Benthological Society. 28(3): 709-718.

Various components of island stream faunas, including caridean shrimps, fish, and gastropods, undertake obligate amphidromous migration, whereby larvae are released in upstream freshwater reaches, drift downstream to estuaries or marine waters, then migrate upstream as postlarvae to freshwater adult habitats. Longitudinal migration from estuaries to headwaters is well documented for many amphidromous species, but the degree of among-river marine dispersal is poorly known for most species. We need better understanding of the potential for marine dispersal in population processes of amphidromous species, particularly recolonization and population recovery in impacted lotic systems, such as those on Puerto Rico, because some theories of dispersal for species with marine larvae predict high rates of self-recruitment. We tested population genetic predictions for widespread marine larval dispersal and self-recruitment to the natal river for 11 amphidromous species, including shrimps, fish, and a gastropod, in Puerto Rico. Population genetic analysis of mitochondrial DNA data showed high rates of gene flow among rivers and indicated that marine dispersal determines the population genetic structure of all 11 species. Difficulty in recruiting to oceanic currents promotes closed population structures in some marine species, but larvae of amphidromous species entrained in downstream river flow might be delivered more readily to ocean currents. Population recovery processes occurred at the island scale rather than at the river scale, but further studies are needed to identify whether population recovery processes are likely at larger spatial scales (e.g., among islands). River management strategies should maintain environmental flows that allow larval export, maintain longitudinal dispersal pathways over dam spillways and via subterranean passages, and maintain open and healthy estuaries.

Conservation and management of migratory fauna and dams in tropical streams of Puerto Rico

Greathouse, E. A., C. M. Pringle, and J. G. Holmquist.
2006. Conservation and management of migratory
fauna: dams in tropical streams of Puerto
Rico. Aquatic Conservation 16:695–712.

1. Compared to most other tropical regions, Puerto Rico appears to have dammed its running waters decades earlier and to a greater degree. The island has more large dams per unit area than many countries in both tropical and temperate regions (e.g., 3x that of the U.S.), and the peak rate of large dam construction occurred two and three decades prior to reported peak rates in Latin America, Asia and Africa. 2. Puerto Rico is a potential window into the future of freshwater migratory fauna in tropical regions, given the island’s extent and magnitude of dam development and the available scientific information on ecology and management of the island’s migratory fauna. 3. We review ecology, management and conservation of migratory fauna in relation to dams in Puerto Rico. Our review includes a synthesis of recent and unpublished observations on upstream effects of large dams on migratory fauna and an analysis of patterns in free crest spillway discharge across Puerto Rican reservoirs. Analyses suggest that large dams with rare spillway discharge cause near, not complete, extirpation of upstream populations of migratory fauna. They also suggest several management and conservation issues in need of further research and consideration. These include research on the costs, benefits and effectiveness of simple fish/shrimp passage designs involving simulating spillway discharge and the appropriateness of establishing predatory fishes in reservoirs of historically fishless drainages.

Distribution of migratory fishes and shrimps along multivariate gradients in tropical island streams

Fievet E, Doledec S, Lim P. 2001. Distribution of migratory fishes and
shrimps along multivariate gradients in tropical island streams. Journal
of Fish Biology 59: 390–402.

Among the 16 species of fishes and shrimps studied at 51 sites along several small streams at Basse Terre, Guadeloupe, Lesser Antilles, more than 60% showed a spatial distribution significantly influenced by environmental conditions. These included altitude, basin size, terrestrial vegetation and land use. However, the range of the species habitat was generally high, except for three species limited to the downstream stretches (two fishes and one shrimp). The habitat characteristics of fish and shrimp species tended to differ, but the difference was not significant (P<0·05). On the contrary, the habitat characteristics of amphidromous and catadromous species clearly differed, with a lower occurrence at the most elevated sites of catadromous species than amphidromous species.
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