Tracking Puerto Rico's Freshwater Gems

From Microcosm Aquarium Explorer


The Sirajo Goby, capable of climbing sheer rock walls and dams with its sucker-like pelvic fins.

Thomas Kwak/NC State University

While best known for its marine species, both large gamefish and coral reef denizens, Puerto Rico is also home to poorly documented populations of freshwater aquatic fishes in its many rivers and forest streams.

Now a team of researchers led by North Carolina State University has made a significant advance in understanding the diversity and species numbers found in the island's freshwater ecosystems.

NC State's Dr. Thomas Kwak, who led the study, says many of these species "are hidden gems that have been largely ignored," and calls the research "a huge first step in conserving and protecting these fish and their habitat."

"Many Charismatic Species"

The study is the first-ever comprehensive population and habitat survey of freshwater fishes in Puerto Rico, Kwak says. The study focuses on identifying those features that support native fish populations, and distinguishing those features that make a system susceptible to invasion by exotic species.

Kwak says the research will likely have a significant impact on how the Puerto Rican government makes decisions on issues ranging from fisheries management to water use and habitat management. Kwak also hopes that the study raises the profile of the freshwater fishes in Puerto Rico both on the island itself and abroad as part of Puerto Rico's natural heritage.

Rainforest stream in El Yunque National Park. Image by Stan Shebs/GNU.

"Just letting the world know the fish are there is an accomplishment," Kwak says. "Many of these fish are very charismatic – they are unique and really worthy of conservation." For example, Kwak points to Puerto Rico's native Sirajo Goby, Sicydium plumieri, brilliantly colored fish that has evolved sucker-like pelvic fins that allow it to climb steep waterfalls and even the sheer faces of some artificial dams.

Study Details

In the abstract of the study, Kwak says: "We employed a standardized fish sampling protocol using three-pass removal backpack or barge electrofishing at 81 stream sites to quantify fish and crustacean populations and measured instream, riparian, and water quality parameters.

"We quantified density of 24 fish species (10 native) and 15 crustacean species (11 shrimp, 3 crabs, 1 crayfish). The most abundant fish species were Agonostomus monticola (Mountain Mullet), Poecilia sphenops (Mexican Molly), Poecilia reticulata (Guppy) and Sicydium plumieri, the Sirajo Goby."

The Puerto Rico Department of Natural and Environmental Resources funded the research with federal Sport Fish Restoration funds, and an overview of the study was presented at the American Fisheries Society (AFS) Annual Meeting in Ottawa, Ontario, earlier this year.

Kwak is a professor of biology at NC State, and a unit leader of the U.S. Geological Survey's North Carolina Cooperative Fish & Wildlife Research Unit. Other researchers involved in the study include: NC State research biologist Patrick Cooney, who was lead author for the AFS presentation; NC State graduate student Christin Brown; and Dr. Craig Lilyestrom, director of the Division of Marine Resources in Puerto Rico's Department of Natural and Environmental Resources.

Sources:" From materials released by North Carolina State University. North Carolina State University

  • From: "Puerto Rico Stream Fishes: Sampling, Distribution, and Influential Factors"
  • Presented: August 21, 2008, at the 138th Annual Meeting of the American Fisheries Society in Ottawa, Ontario.
  • Authors: Patrick B. Cooney, Dr. Thomas J. Kwak, Christin H. Brown, North Carolina State University; Dr. Craig G. Lilyestrom, Puerto Rico Department of Natural and Environmental Resources