7987

• UCREFRP Catalog Number: 7987
• Author: Sheldon, A. L.
• Title: Conservation of Stream Fishes
• USFW Year: 1988
• USFW - Doc Type: Patterns of Diversity, Rarity, and Risk
• Copyright Material: YES

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Conservation of Stream Fishes:
Patterns of Diversity, Rarity, and Risk

ANDREW L. SHELDON

Zoology Department
University of Montana
Missoula, MT 59812, U.SA.

Abstiact: North America has a rich fauna of freshwater
fishes which attains greatest diversity in the central and
southeastern United States. Many stream fishes have limited
ranges and are locally rare and patchily distributed Local
diversity increases doumstream and total diversity follows
typical species-area relationships. Drainages linked with the
large Mississippi system support more species than those of
comparable area flowing directly to the sea, and rivers iso-
lated by falls have notably few species. The between-
drainage component of diversity is large. Threats to this
fauna, which are not addressed by management focused on
threatened species, include fragmentation of drainage net-
works by impoundments and homogenization of faunas by
interbasin connections and introductions. Conservation ef-
forts require a biogeographic perspective; they should focus
on streams of intennediate size (orders 4-6) plus the up-
stream portion of each drainage and should attempt to
maintain total diversity and, inclusively, populations of
rare or threatened species.

Introduction

The rivers and lakes of North America are inhabited by
a rich assemblage of fishes. Approximately 700 species
regularly spend all or significant portions of their life
histories in the fresh waters of the United States and
Canada (Lee et al. 1980); the diversity exceeds that of
the birds of the same region (Robbins, Bruun, & Zim
1966). The distinctive Mexican fauna (Miller 1966;
Miller & Smith 1986), with numerous endemics and an
infusion of neotropica1 taxa, adds many more. Although
the diversity of fishes in the United States does not ap-

Resumen: America del Norte tiene una fauna rica en peces
de agua dulce, la cual alcanza su mayor diversidad en las
regiones central y sureste de los Estados Unidos. Mucbos de
los peces de a7TO)l0s tienen una extencion limitada, son raros
a nivellocal y se encuentran irregularmente distribuidos. La
diversidad a nivel local aumenta aguas abajo, y la diver-
sidad total sigue las relaciones tipicas de especies-area. Las
cuencas conectadas con el gran sistema del rio Mississippi
contienen mas especies que aquellas de super/iete compara-
ble que desembocan directamente al mar, y los rlos aislados
por cataratas presentan un numero de especies notable-
mente pequeno. EI componente de la diversidad de las espe-
cies que se encuentran en las areas entre drenajes, es grande.
Las amenazas a esta fauna, problema no tratado por el
manejo enfocado en especies en peligro de extincion, in-
cluyen la fragmentaciOn de las redes de drenaje por media de
represas y la homogenizacion de faunas mediante conec-
ciones entre cuencas e introducciones. Los esfuerzos de con-
servacion requieren de una perspectiva biogeografica, deben
enfocarse en arroyos de tamaflO intermedio (orden de 4-6)
mas Ie poreion aguas arriba de calla drenaje, Y deberlan
intentar mantener la diversidad total e, incluso, las pobla-
ciones de especies rams 0 en peligro de extinci6n.

proach that of the great tropical rivers of South America,
Africa, and Asia, it far exceeds that of European fresh
waters (lowe-McConnell 1969, 1975).
Freshwater fishes of the United States include survi-
vors of ancient lineages such as the bowfin (Amiidae),
gars (Lepisosteidae), sturgeons (Acipenseridae), paddle-
fish (Polyodontidae), and mooneyes (Hiodontidae).
Many families (e.g., minnows, Cyprinidae) are shared
with Eurasia, and in some families, including the pikes
(Esocidae) and sculpmS (Cottidae), genera or species
occur throughout the Holarctic. Sunfishes (Ceo-
trarchidae) and a catfish family (Ictaluridae) are re-

149

Conservation Biology
Volume 2, No. 2, June 1988