7374

• UCREFRP Catalog Number: 7374
• Author: Sheldon, A. L.
• Title: Conservation of Stream Fishes
• USFW Year: 1988
• USFW - Doc Type: Patterns of Diversity, Rarity, and Risk
• Copyright Material: YES

1;0 Conservation of Stream fishes c>

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stricted to North America and the suckers(Catostomi-
dae) nearly so. Smaller families also confmed to North
America are pirate perch (Aphredoderidae), trout-
perches (Percopsidae), and cavefishes (Amblyopsidae}
Darters (Etheostomatini, Percidae) have radiated spec-
tacularly (Page 1983); they contribute about 20% of the
species in the total fish fauna north of Mexico and are
among the most attractive of all fishes. The . cyprinid
genus Notropis (which may be polyphyletic) is similarly
diverse. Gilbert (1976) and Hocutt & Wiley (1986) pro-
vide thorough treatments of the origin and distribution
of North American fishes. Moyle and Cech (1982) illus-
trate representatives of most families and summarize
their biology.
Minnows dominate.. the fauna and the Percidae
(mostly darters) run a close second in diversity. Other
prominent families are the suckers, catfishes, and sun-
fishes. Killifishes (Cyprinodontidae) and livebearers
(Poeciliidae) are widely distributed and are especially
characteristic of remnant waters of the southwestern
United States (see Vrijenhoek & Meffe, this issue}
Salmonidae' (trout, salmon, whitefish, grayling) and
sculpins become increasingly common in the northern
United States and Canada. Approximately twenty addi-
tional families contribute species, many of which are
widespread and numerous.
These fishes are not evenly distributed(F~g. I} ltivers
west oftbc O)D'IiIlc:!ftbtl. divide contain'fdatively few,
species. althougbtheirtimnas are distinctive and ende.
mism is high (e.g., Stanford & Ward 1986). East of the
divide, the Mississippi system is far richer than the
smaller Gulf and Atlantic coastal rivers although these in
turn have more species than the Pacific drainages. Fish
diversity is greatest in the southeastern United States
(see McAllister et al. [1986] for a quantitative analysis of
patterns of species richness} Diversity decreases north-
ward, especially along the Atlantic coast. Rivers such as
the Savannah that drain phySiographieally, diverse areas
have more species than rivers such as the St. Johns in
Florida that are confined to lowlands.
The Great Lakes and tributaries, which are not con-
sidered further in this essay, have 162 native species
(Underhill 1986). Most of these occur in streams. The
lacustrine component of the fish fauna has been cata-
strophically altered by introductions, exploitation, and
pollution (e.g., Smith 1968; Crowder 1980), resulting in
the extinction of three species and one subspecies
(Williams & Nowak 1986).

Conservation Status

More than half of the freshwater fishes of the United
States and Canada receive some legal protection in at
least part of their range Oohnson 1987). Far fewer (a
total of 75 species and subspecies) are federally desig-

Conservation Biology
Volume 2, No. 2. June 1988

Sheldon

nated as endangered or threatened (U.S. Fish & Wildlife
Service 1987} Endangered taxa are strongly concen-
trated in the arid west (Fig. 2). Threatened species (Fig.
3) likewise are predominantly western but include a
greater proportion from the diverse southeastern fauna. .
Many of these fishes, especially the western ones, are
extremely localized in springs and fragmented desert
drainages. Ono et aI. (1983) provide species accounts
for these and additional rare species.
The emphasis in the conservation of fishes has been
on habitat preservation and single-species management.
Given the restricted habitats of many fishes and the eco-
nomic value of water in arid landscapes, this emphasis is
understandable and sensible. Focused plans for the man-
agement of species and habitats will continue to be an
integral part of fish conservation. However, I suggest
that a comprehensive view of river systems and their
fishes is required if more than a small fraction of the fish
fauna is to persist.

Patterns of Distribution and Abundance

Few species of stream fish are widely distributed (McAl-
lister et al. 1986). Abundances in local assemblages ap-
proximate lognormal frequency distributions (Loubens
1970; Sheldon 1987} Thus, most species are geograph-
ically restricted and numerically rare where they occur.
Furthermore, patchy distributions are common; Some
threatened species (Fig. 3) apparently exist in only a
few widely separated localities. Although this apparent
patchiness may be a consequence of general rarity and
low detectability (e.g., Starnes et al. 1977), present ev-
idence implies both local rarity and restricted range.
Historical records are adequate to show substantial
declines of many stream fishes. For example, the rosy-
face shiner, Notropis rubellus, remains widely distrib-
uted (Lee et al. 1980) and locally common, yet it had
disappeared from much of its range in Ohio by midcen-
tury (Trautman 1957). A more extreme case is the hare-
lip sucker Lagochila, which vanished from the rivers of
nine southeastern and midwestern states before 1900
(Ono et aI. 1983).

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~.relati~Wnd..Ih-~:Df,f~~_+
ness ClCCUp1.a.~.ptace'id'~oIr~,
and stream systems are amenable to this approach. The
geometry of drainage area has been related to species
richness of fishes (Eadie et al. 1986; Larsen et al. 1986;
Swift et al. 1986) and molluscs (Sepkoski & Rex 1974).
DifJdlIl'ge,' a more directmc~ of a~~"'"
thibitat, wasusro'by . Livingstone, . Rowland, 8r Ba.lley
(1-9*2 ) and Sheldon (1987) in place of area.. ;'fhe ob-
served increase of faunal diversity with increasing drain-

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