Puerto Rico’s Inland Waters and Recreational Fishery are Threatened by Invasive Exotic Species.

Fishing, Beaches and the Environment recognizes that Puerto Rico has an uneasy relationship
with exotic species in the island’s inland waters. In the 20 th century, when rivers were being
dammed for hydroelectric power, drinking water supply or flood control, the native riverine
fauna, with very few exceptions, were unable to adapt to the reservoir environment. Exotic
species were introduced mainly from North America (largemouth bass, sunfish, catfish,
threadfin shad), and later peacock bass from South America and tilapia from Africa. Gambusia,
small livebearers, were introduced to control mosquitos. These were planned introductions by
government agencies, with a stated purpose of providing a recreational fishery plus a source of
protein to rural populations, control of rooted aquatic vegetation by the tilapia, and avoiding
disease in the case of the mosquitofish. These planned fish species introductions were wildly
successful in providing a high quality inland recreational fishery that lead to the formation of
numerous bass fishing clubs that hold tournaments throughout the year, benefitting the local
economy in various ways. They provide a source of enjoyment for tens of thousands of
occasional anglers as well. The Puerto Rico Department of Natural and Environmental
Resources supports this activity through regular fish community composition evaluations, fish
stockings from the Maricao Fish Hatchery as needed, educational programs to encourage new
anglers to join in the fun, and has developed 4 first-class recreational fishing facilities at
reservoirs.

In spite of these advances, a threat to the inland fishery has grown over the years, as has
happened in many countries around the world. The threat stems from two separate sources:
the aquaculture industry and the ornamental fish trade and the unplanned release of invasive
exotic species into inland waters.
In 1994, Armored catfish from the Amazon were reported in Puerto Rico reservoirs and rivers as
having been present since about 1990. It was speculated that they were the result of aquarium
fish releases, as they possibly grew too large for their tanks. At the time, it was limited to a few
rivers and reservoirs. Currently, the species is found in nearly every inland water body, in great
abundance, as it has no natural predators or competitors.
In 2001, a warning was published about the recent introduction of exotic aquatic invertebrates
in Puerto Rico waters – including Asian clams (probably from an aquaculture source) and
Australian redclaw crawfish (from an unpermitted aquaculture source in the Loiza River
headwaters). Asian clams are now abundant in reservoirs across the island, and redclaw are in
many streams and reservoirs.
More recently, additional studies in Puerto Rico’s reservoirs and rivers have detected the
presence of many species of fish that have been introduced in an uncontrolled fashion, with no
logical or reasonable purpose, many of which significantly complicate the standard fishery
management techniques and strategies that in the past helped provide a quality, sustainable
recreational fishery. Some of these species are highly aggressive and voracious predators

A new (2020) publication has summarized the current status of exotic fish species in inland
waters of Puerto Rico and warns especially of the dangers of the cichlid species sold in
aquarium stores, since there are already 13 species established in our reservoirs. The authors
warn that non-native species can pose a serious threat to freshwater ecosystems, especially on
island ecosystems. (https://www.tandfonline.com/doi/full/10.1080/23766808.2020.1729303)
This report lists 46 freshwater fish for Puerto Rico freshwater systems. Thirteen of the species
are cichlids, and 7 are poeciliids, neither of which are native to the island. Only 9 species are
native to Puerto Rico.
Fishing, Beaches and the Environment joins with the researchers and authors of the present
and past studies in exhorting the public and the pertinent environmental agencies to avoid any
further unplanned introductions of exotic species in the inland or marine waters of Puerto Rico.
Once a species is established in the wild, there is no way to eliminate it, no matter how
damaging it may be.

References:
Bunkley-Williams, L., E.H. Williams, Jr. C.G. Lilyestrom, I. Corujo-Flores, A. J. Zerbi, C. Aliaume,
and T. N. Churchill. 1994. The South American Sailfin Armored Catfish, Liposarcus
multiradiatus (Hancock), a New Exotic Established in Puerto Rican Fresh Waters.
Caribbean Journal of Science, 30 (1-2): 90-94.
Ruber Rodriguez-Barreras, Camille Zapata-Arroyo, Wilfredo Falcón L. & Maria de Lourdes
Olmeda (2020) An island invaded by exotics: a review of freshwater fish in Puerto Rico.
Neotropical Biodiversity. 6:1, 42-59. DOI: 10.1080/23766808.1729303
Williams, Jr., E.H., L. Bunkley-Williams, C.G. Lilyestrom and E. A.R. Ortiz-Corps. 2001. A Review
of Recent Introductions of Aquatic Invertebrates in Puerto Rico and Implications for the
Management of Nonindigenous Species. 2001. Caribbean Journal of Science, 37 (3-4):246-
251.