Douglas S. Bateman

Evaluating Single-Pass Catch as a Tool for Identifying Spatial Pattern in Fish Distribution

ABSTRACT We evaluate the efficacy of single-pass electrofishing without blocknets as a tool for collecting spatially continuous fish distribution data in headwater streams. We compare spatial patterns in abundance, sampling effort, and length-frequency distributions from single-pass sampling of coastal cutthroat trout (Oncorhynchus clarki clarki) to data obtained from a more precise multiple-pass removal electrofishing method in two mid-sized (500–1000 ha) forested watersheds in western Oregon. Abundance estimates from single- and multiple-pass removal electrofishing were positively correlated in both watersheds, r = 0.99 and 0.86. There were no significant trends in capture probabilities at the watershed scale (P > 0.05). Moreover, among-sample variation in fish abundance was higher than within-sample error in both streams indicating that increased precision of unit-scale abundance estimates would provide less information on patterns of abundance than increasing the fraction of habitat units sampled. In the two watersheds, respectively, single-pass electrofishing captured 78 and 74% of the estimated population of cutthroat trout with 7 and 10% of the effort. At the scale of intermediate-sized watersheds, single-pass electrofishing exhibited a sufficient level of precision to be effective in detecting spatial patterns of cutthroat trout abundance and may be a useful tool for providing the context for investigating fish-habitat relationships at multiple scales.

Survival and growth of age-0 steelhead after surgical implantation of 23-mm passive integrated transponders

Abstract Little information is available on the effects of implanting 23-mm passive integrated transponder (PIT) tags in salmonids less than 90 mm fork length (FL). Using juvenile steelhead Oncorhynchus mykiss (range, 73–97 mm FL), we compared instantaneous growth rates and survival among three experimental groups: control, surgery with no tag, and surgery with tag. Survival rate was lower for tagged fish (86%) than for control and surgery−no tag fish (virtually 100% in each group). Approximately 90% of the mortalities occurred during days 1–3. Growth rate for the tagged group was lower for the first two 10-d measurement intervals; however, during the third 10-d interval, growth rates for tagged fish equaled or exceeded values for the other groups. These results suggest that tagged fish recovered by day 20. Growth rates for the control and surgery−no tag groups did not differ from one another during any measurement interval. Tag retention rate was 97% over the 30-d period of the study. It appears that the...

Digital terrain modeling of small stream channels with a total-station theodolite

Abstract A Digital Terrain Model (DTM) is an alternative to traditional measures of stream channel morphology that allows for extraction of many different types of data. This paper describes a method of creating high-resolution Digital Terrain Models of stream channels using an electronic, digital, total-station theodolite and standard methods of land surveying, and also includes considerations unique to hydrological application. Included is a detailed description of one application in Oregon, and also suggestions of how to apply the method in other research of morphology.

Passive Integrated Transponder Tag Retention Rates in Headwater Populations of Coastal Cutthroat Trout

Abstract Passive integrated transponder (PIT) tags have desirable qualities (e.g., unique identification, indefinite tag life, and capacity for remote detection) that make them useful for evaluating survival, growth, and movement of fish, but low tag retention rates can confound data interpretation. Although the effects of PIT tags on short-term growth and survival have been minimal and tag retention rates in laboratory and field studies using only juvenile individuals have been high, tag retention rates for fish at different ontological stages (including reproductively active males and females) remain unknown. We evaluated tag retention rates in wild populations of coastal cutthroat trout Oncorhynchus clarkii clarkii in three catchments of western Oregon using a double-marking approach (i.e., the adipose fin was removed from all fish that were PIT-tagged). Tags were inserted into the body cavities of fish 100 mm or more in length (fork length; range = 100–250 mm). In the study catchments, this size range...

Physical Aquatic Habitat II. Pools and Cover Affected by Large Woody Debris in Three Western Oregon Streams

Abstract Large woody debris (LWD) is important in affecting stream channel morphology and aquatic habitat. Although the greatest effects on streams of the Pacific Northwest have been by LWD from large conifers, many riparian forests in the region are dominated by red alder Alnus rubra. The effects of the small size and short life of LWD from red alders on channel morphology may be different from that of conifers and are poorly understood. We added LWD (primarily red alder) to three third-order streams in the Oregon Coast Range and used digital terrain models to evaluate physical habitat for salmonids over 3 years. Total residual pool volume increased in two streams, but in the one with the lowest gradient it did not change in the treated portion and even decreased in the untreated portion. In all streams, both the relative proportion and absolute amount of residual pool volume from deep pools increased from their pretreatment values. Cover from LWD in pools increased after treatment and remained high, but...

Nest Site Selection by Reticulate Sculpin in Two Streams of Different Geologies in the Central Coast Range of Oregon

Abstract Nest sites of reticulate sculpin Cottus perplexus were located in segments of two streams that were similar in gradient, basin area, elevation, climate, and riparian vegetation but that differed in geology and biological community structure. An electivity index was used to determine habitat selected for nest sites. Strong positive selection for moderately embedded cobble substrate was shown in pools and riffles from both stream segments, even though the availability of that habitat varied. No eggs were found attached to bedrock, wood, or particles smaller than large gravel. Only 1 of the 471 nests located was associated with rocks that were embedded more than 50%.