7926

• UCREFRP Catalog Number: 7926
• Author: Annear, T. C. and A. L. Conder.
• Title: Relative Bias of Several Fisheries Instream Flow Methods.
• USFW Year: n.d.
• USFW - Doc Type: Cheyenne, Wyoming.
• Copyright Material: NO

(migration or spawning).

Such a concept also supposes that a

Pe rhaps :1 more realis tic approach (in ecological terms) to ins tream

analysis is the concept of dynamic instreamflow needs. This concept addres~

seasonally adjusted flow needs based on fish species, life stage,

possible flows at a given time of year will impact the fishery

degrees.

Although both threshold and dynamic concepts of instream flow analysis should

be considered when addressing this issue, they may not always both be

appropriate (as in free-flowing streams where threshold flows may be the primary

concern) or necessary (as in low priority cases). Any method used to define an

instream flow for fisheries should be (1) based on biological data, (2) defen-

sible, and (3) capable of quantifying trade~offs to some degree.

(i :::r:.\

In situations where only reconnaissance-grade MF estimates are required

(such as early planning stages of water projects), the Tennant method based on

30% AF may be a useful tool.

The recommendations generated by this method

appear

relatively unbiased, they can be developed quickly (especially when

stream flow records are available), and the method is in~xpensive. The primary

value of this method is' that it is generally defensible bas~d on its acceptance

by both biologists and non-biologists as well as the rather broad data base from

which the method was developed. . however, its applicability is limited by its

failure to incorporate site-specific biolo~ical and hydrological information

and inability to quantify trade-offs.

Although cost and time should not be the most important factors in the

selection of an appropriate method, they are nonetheless important con-

:

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