DOI: 10.5061/dryad.70rxwdc03
title: Supporting tables and figures for Cancel Villamil JJ, Locke SA (2022) - Fish assemblage response to removal of a low‐head dam in the lower reach of a tropical island river, Freshwater Biology

description: Table S1 summarizes studies of the effects of dams on freshwater fish
 assemblages Table S2 provides results of fishing in 39 samples in three
 rivers in Puerto Rico in 2017-2019. See 2, below.  Figure S1
 shows the relationship between fish species richness and time spent
 electrofishing in these samples. Abstract of article: 1. Dams are often
 removed from rivers to restore habitat connectivity for biota such as
 fish. Removal of inland dams is well studied in temperate mainland rivers
 but this approach has been little studied in fish assemblages in islands,
 tropic systems, or for dams near the mouth of the river. In Puerto Rico,
 one of the most intensively dammed territories in the world, all native
 river fishes migrate between fresh water and the sea, and previous work
 shows these movements are impeded or blocked by dams. 2. Fish assemblages
 were compared before and after removal of the Cambalache dam, a porous,
 low-head structure near the mouth of the Río Grande de Arecibo, as well as
 in two other rivers in Western Puerto Rico, one with a similarly sized and
 positioned dam, and one reference river without artificial barriers. Fish
 were sampled using backpack electrofishing on 39 occasions during
 2017-2019, including seven samples collected after removal of the
 Cambalache dam, at between four and six sites per river. 3. Fish
 assemblages upstream from dams were poorer in species, and species
 richness showed a marginal tendency (P=0.0515) to increase upstream of the
 Cambalache dam three months after its removal. The two small lowland dams
 studied herein limited the upstream extent of marine species, which
 recolonized upstream sites of the Río Grande de Arecibo after removal of
 the Cambalache dam. An estimate of relative density (catch per unit
 effort) of common native freshwater species was higher above these two
 dams, and decreased at upstream sites after removal of the Cambalache dam.
 The estimated relative density of a native freshwater species that is of
 conservation concern, the American eel (Anguilla rostrata), was reduced
 above dams, and increased upstream of the former Cambalache dam after its
 removal.  4. In extensive surveys conducted previously in Puerto
 Rico, sampling was concentrated higher in the watershed, and native fishes
 were more common and abundant below than above dams. The present work was
 conducted near the river mouth, and opposite results were observed. These
 contrasting results suggest that the effects of dams (or dam removal) on
 fish assemblages vary along the river gradient, although data from other
 systems are needed to confirm this. 5. The present results suggest
 low-head dam removal to be a viable method of restoring connectivity in
 fish assemblages in lower reaches of rivers in Puerto Rico and,
 potentially, other tropical islands. Removal of dams near the mouth of the
 river appears to be of particular benefit to marine fish species that use
 lower river reaches.
description: Citation: Title: Fish assemblage response to
 removal of a low‐head dam in the lower reach of a tropical island
 river<br> Authors: Johann J. Cancel Villamil, Sean A.
 Locke<br> Journal: Freshwater Biology<br> Year: 2022