William J. Matter

Effects of Flooding on Abundance of Native and Nonnative Fishes Downstream from a Small Impoundment

Abstract Flooding can benefit native fishes in southwestern streams by disproportionately displacing nonnative fishes. We examined how the presence of an upstream impoundment affected this relationship in lower Sonoita Creek, Arizona. Nonnative species not found in the reservoir decreased in abundance in lower Sonoita Creek after flooding. The catch and relative abundance of some nonnative species found in both the reservoir and the creek increased in lower Sonoita Creek after flooding. Movement of nonnative fishes out of the reservoir via the spillway during periods of high water probably contributes to the persistence and abundance of these species downstream. Both preventing nonnative fishes from escaping reservoirs and the release of flushing flows would aid conservation of native southwestern fishes downstream.

Standard weight (Ws) equations for four rare desert fishes

Abstract Standard weight (W s) equations have been used extensively to examine body condition in sport fishes. However, development of these equations for nongame fishes has only recently been emphasized. We used the regression-line-percentile technique to develop standard weight equations for four rare desert fishes: flannelmouth sucker Catostomus latipinnis, razorback sucker Xyrauchen texanus, roundtail chub Gila robusta, and humpback chub G. cypha. The W s equation for flannelmouth suckers of 100–690 mm total length (TL) was developed from 17 populations: log10 W s = −5.180 + 3.068 log10TL. The W s equation for razorback suckers of 110–885 mm TL was developed from 12 populations: log10 W s = −4.886 + 2.985 log10TL. The W s equation for roundtail chub of 100–525 mm TL was developed from 20 populations: log10 W s = −5.065 + 3.015 log10TL. The W s equation for humpback chub of 120– 495 mm TL was developed from 9 populations: log10 W s = −5.278 + 3.096 log10TL. These equations meet criteria for acceptable ...

Effects of Temperature, Fish Length, and Exercise on Swimming Performance of Age-0 Flannelmouth Sucker

Abstract The flannelmouth sucker Catostomus latipinnis is one of the few native fish that persists in the lower Colorado River basin. Little is known about the effects of hypolimnetic releases of cold, swift water from Colorado River dams on flannelmouth sucker populations. We conducted fatigue velocity tests on age-0 flannelmouth suckers in the laboratory to evaluate the effects of water temperature and fish size on swimming ability. Fish of 25-114 mm total length (TL) were subjected to incremental increases in water velocity until the upper limit of their swimming ability was reached. Swimming tests were conducted at 10, 14, and 20°C. Swimming ability increased with fish length and was directly related to water temperature at all fish sizes. A decrease in water temperature from 20°C to 10°C resulted in an average decrease in swimming ability of 40%. Mean swimming ability of wild-caught flannelmouth suckers was 7 cm/s higher than that of captive-reared flannelmouth suckers of similar size at 20°C and 14°...

EFFECTS OF SMALL GREEN SUNFISH (LEPOMIS CYANELLUS) ON RECRUITMENT OF GILA CHUB (GILA INTERMEDIA) IN SABINO CREEK, ARIZONA

Young-of-year Gila chub (Gila intermedia) were abundant in upstream reaches of Sabino Creek, Arizona, devoid of green sunfish (Lepomis cyanellus), but were absent in downstream areas occupied by green sunfish. We examined potential reasons for this pattern by studying piscivory and habitat use of small green sunfish ( 150 mm TL) green sunfish. However, even small green sunfish were highly predacious on young-of-year Gila chub, and our habitat study demonstrated that both taxa occupied similar mesohabitats. Co-oc- currence of Gila chub and green sunfish in Sabino Creek seems to be the result of periodic downstream movement of adult Gila chub from reaches devoid of green sunfish. Young life stages of Gila chub apparently do not persist in sections of Sabino Creek occupied by green sunfish. RESUMEN-Juveniles del afio de charalito de Gila (Gila intermedia) abundaban rio arriba de Sabino Creek, Arizona, carente de robalo verde (Lepomis cyanellus), pero no estaba rio abajo en

HOW DO PREY PERSIST

Abstract Understanding predator–prey relations is critical for management and conservation of species. Common descriptions of predator–prey dynamics often imply that low population density of prey, prey switching by predators, and high fecundity or productivity of prey are important in allowing prey species to coexist with predators. Studies of the effects of introduced predators on prey species do not support the idea that low prey density, switching by predators, and fecundity of prey are vital to coexistence of predator and prey. More likely, prey have a suite of morphological and behavior adaptations, including uses of specific habitat features, that render some individuals far less vulnerable to predation and allow predators and prey to coexist. Management activities designed to maintain desired prey species should include maintaining or enhancing features of habitat that reduce prey vulnerability.

Food and Habitat Use by Different Sizes of Largemouth Bass (Micropterus salmoides) in Alamo Lake, Arizona

ABSTRACT Each of three size groups of largemouth bass (Micropterus salmoides) differed in foraging behavior and habitat use in an Arizona reservoir. Small bass ( 38 cm TL) were generally found as solitary individuals near submerged structures suitable for ambush feeding. The allometric growth of these fish may have rendered them too bulky to effectively forage in the limnetic zone. Differences in habitat use and foraging behavior for different sizes of largemouth bass in the reservoir appear to be the result of the interaction of the behavioral flexibility of the species, site-specific resources and ecomorphological constraints.

A Laboratory Approach for Studying Emigration

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Vulnerability of Redbelly Tilapia Fry to Bluegill Predation with Changes in Cover Availability

Abstract The successful use of redbelly tilapia (Tilapia zilli) to control aquatic plants in ponds with game fish depends on high survival of tilapia young. We tested the vulnerability of redbelly tilapia fry under parental care to predation by bluegill. Experiments were conducted for a 3-day period in 5.5-m diameter pools at three levels of artificial plant cover (25, 50, and 75%) and at two densities of predators (15 and 20 per pool). Predation rates on 14-day-old, unprotected fry also were determined. Fry survival was lowest with 25% cover (mean 40%) and highest with 75% cover (mean 72.5%). The survival of fry at 50% cover (mean 68.2%) was significantly higher than survival at 25% cover, but there was no significant difference in fry survival between 50 and 75% cover. Fry survival was poor without parental care, ranging from 6 to 34%. Extrapolation of the survival data indicated that too few Tilapia zilli, when stocked with predatory game fish, would survive to the size where they could adequately cont...

The impact of surface mine reclamation on headwater streams in Southwest Virginia

Recovery of headwater streams following the cessation of mining and the application of terrestrial (vegetative) reclamation techniques was assessed by comparison of water quality and aquatic biota in two such systems (reclaimed four to seven years) with that of an unimpacted stream and of streams draining mine areas which were abandoned without reclamation. Alkalinity, hardness, sulfate, and conductivity were elevated in the reclaimed mine streams as were fine-particle suspended solids and sediment. Overall water quality was comparable to streams draining unreclaimed lands. Benthic invertebrate and fish populations were significantly lower in abundance in the reclaimed mine streams than in the reference stream and showed less taxonomic richness and stability; they were similar in these respects to the biota of the unreclaimed mine streams. Continued sedimentation from mined areas and haul roads affected stream habitat and appeared to be the major factor limiting biotic recovery. These findings emphasize that terrestrial reclamation does not assure lotic restoration. Water quality criteria merit consideration in the refinement of reclamation procedures for mined lands.

Changes in reproductive biomarkers in an endangered fish species (bonytail chub, Gila elegans) exposed to low levels of organic wastewater compounds in a controlled experiment

In arid regions of the southwestern United States, municipal wastewater treatment plants commonly discharge treated effluent directly into streams that would otherwise be dry most of the year. A better understanding is needed of how effluent-dependent waters (EDWs) differ from more natural aquatic ecosystems and the ecological effect of low levels of environmentally persistent organic wastewater compounds (OWCs) with distance from the pollutant source. In a controlled experiment, we found 26 compounds common to municipal effluent in treatment raceways all at concentrations <1.0 microg/L. Male bonytail chub (Gila elegans) in tanks containing municipal effluent had significantly lower levels of 11-ketotestosterone (p=0.021) yet higher levels of 17beta-estradiol (p=0.002) and vitellogenin (p=0.036) compared to control male fish. Female bonytail chub in treatment tanks had significantly lower concentrations of 17beta-estradiol than control females (p=0.001). The normally inverse relationship between primary male and female sex hormones, expected in un-impaired fish, was greatly decreased in treatment (r=0.00) versus control (r=-0.66) female fish. We found a similar, but not as significant, trend between treatment (r=-0.45) and control (r=-0.82) male fish. Measures of fish condition showed no significant differences between male or female fish housed in effluent or clean water. Inter-sex condition did not occur and testicular and ovarian cells appeared normal for the respective developmental stage and we observed no morphological alteration in fish. The population-level impacts of these findings are uncertain. Studies examining the long-term, generational and behavioral effects to aquatic organisms chronically exposed to low levels of OWC mixtures are needed.