7612 ‎(2)‎

• UCREFRP Catalog Number: 7612
• Author: Roberts, B. and M. Moretti.
• Title: Final Fisheries Survey of the San Juan River, Utah 1988.
• USFW Year: 1988.
• USFW - Doc Type: Salt Lake City, Utah.
• Copyright Material: NO

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was too deep to safely cross, the sei ne haul s began and ended on the same
shoreline, sampling as deep as possible. Shallow backwaters that were long and
narrow were also sampled parallel to shore to increase the sampling area.
Para 11 e 1 sei ne haul s were termi nated away from the end of the backwater to
prevent crowding. Data recorded for the first seine haul included the following:
.B.ll rare_f.llhes t.~at could be reliabl identified in t!le field were measur~j.m:J
re 1 eased. A 11 otfler 1 s es re 1a 1 ent' . Ii .c6Ufifea- anarereased.
~nlaentllie lS es were reserve % buffered forma ln or 1 1 lca 10n
in tea oratory. . In e secon selne aul, all rarefrs-es werenanal'edthe
same-a"s-in-tfie-rirst seine haul. ather fishes reliably identified were released
without enumeration. Third and fourth seine hauls were made in some larger
backwaters to increase the chance of catching rare fishes. Due to the scarcity
of backwaters above RMI 15.0, all backwaters of approximately 30 m2 or greater
surface area were seined. Below RMI 15.0, lout of every 3 or 4 backwaters were
seined. In August, seining efforts between RMI 15-5 concentrated on the shallow
temporary backwaters located on the downstream ends of point sand bars. Seining
efforts in the same river reach in September concentrated on the deeper, more
stable backwaters located near mouths of the numerous washes (e.g., Oljeto,
Steer, Whirlwind, etc.) where yay Colorado squawfish were collected by the BOR
in 1987.

Physjcal habitat measurements were taken at all areas seined with
standardized methods. Maximum water depth, length and width of habitat and of
area seined, water depth at the midpoint of the long axis of the backwater and
water depths midway between the shorelines and the midpoint were recorded at
each backwater. In backwaters where seine hauls began and ended on the same
shoreline, the deepest depth and depths 1/3 and 2/3 of the distance between the
shoreline and the outside edge of the sampled area were measured. The size of
the predominant and second most common substrate on either side of the maximum
seining depth was estimated and recorded. The silt/mud depth at the mid-point
of the long axis of the backwater was also recorded. Data for each seine haul
also included water temperature at the mid-point of the long axis of the habitat,
and water temperature in the mid-channel of the river adjacent to the habitat
seined.

Incidental yay seining was conducted in conjunction with spring electro-
fishing (RMI 135-87) and canyon netting (RMI 60-20). The primary objective of
the incidental seining was to document the distribution of yay and/or juvenile
rare fishes. Areas seined included backwaters, isolated pools, back eddies and
other slow moving riverine habitats. Width and length of each seine haul was
measured to quantify density of fishes.

RESULTS AND DISCUSSION

Mean monthly flows were considerably lower in 1988 than in 1987 and post-
Navajo Dam years, 1965-1986 (Figure 4). Differences in the electrofishing/YOY
seining catch rates and species composition between the two study years are
probably related to these flows. It is difficult to draw any conclusions .based
on two years of data, especially when the two years were extremely different in
terms of the flows. .

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