Christopher A. Myrick

Potential impacts of global climate change on freshwater fisheries

Despite uncertainty in all levels of analysis, recent and long-term changes in our climate point to the distinct possibility that greenhouse gas emissions have altered mean annual temperatures, precipitation and weather patterns. Modeling efforts that use doubled atmospheric CO2 scenarios predict a 1–7°C mean global temperature increase, regional changes in precipitation patterns and storm tracks, and the possibility of “surprises” or sudden irreversible regime shifts. The general effects of climate change on freshwater systems will likely be increased water temperatures, decreased dissolved oxygen levels, and the increased toxicity of pollutants. In lotic systems, altered hydrologic regimes and increased groundwater temperatures could affect the quality of fish habitat. In lentic systems, eutrophication may be exacerbated or offset, and stratification will likely become more pronounced and stronger. This could alter food webs and change habitat availability and quality. Fish physiology is inextricably linked to temperature, and fish have evolved to cope with specific hydrologic regimes and habitat niches. Therefore, their physiology and life histories will be affected by alterations induced by climate change. Fish communities may change as range shifts will likely occur on a species level, not a community level; this will add novel biotic pressures to aquatic communities. Genetic change is also possible and is the only biological option for fish that are unable to migrate or acclimate. Endemic species, species in fragmented habitats, or those in east–west oriented systems will be less able to follow changing thermal isolines over time. Artisanal, commercial, and recreational fisheries worldwide depend upon freshwater fishes. Impacted fisheries may make it difficult for developing countries to meet their food demand, and developed countries may experience economic losses. As it strengthens over time, global climate change will become a more powerful stressor for fish living in natural or artificial systems. Furthermore, human response to climate change (e.g., increased water diversion) will exacerbate its already-detrimental effects.Model predictions indicate that global climate change will continue even if greenhouse gas emissions decrease or cease. Therefore, proactive management strategies such as removing other stressors from natural systems will be necessary to sustain our freshwater fisheries.

How High Can Brook Trout Jump? A Laboratory Evaluation of Brook Trout Jumping Performance

Abstract Quantitative data on how high brook trout Salvelinus fontinalis can jump are crucial for efforts by fisheries managers to exclude brook trout from streams containing native cutthroat trout Oncorhynchus clarkii subspp. and to build effective fishways for brook trout migration. We identified factors that could influence brook trout jumping ability and demonstrated how this knowledge could be applied to improve the design of barriers to brook trout migration or fishways to facilitate their migration. Our objective was to measure brook trout jumping performance under laboratory conditions to identify design features for constructing waterfall-type barriers or pool-and-weir-type fishways. We used flashboard-type and flume-type adjustable waterfall devices to measure brook trout jumping performance at various combinations of vertical or waterfall height (13.5–93.5 cm in 10-cm increments) and plunge pool depth (10–60 cm in 10-cm increments) over a 24-h interval. We tested three size-classes of brook tro...

Swimming performances of four California stream fishes: temperature effects

The critical swimming velocity (Ucrit) of four California stream fishes, hardhead, Mylopharodon conocephalus, hitch, Lavinia exilicauda, Sacramento pikeminnow, Ptychocheilus grandis, and Sacramento sucker, Catostomus occidentalis was measured at 10, 15, and 20°C. Hardhead, Sacramento sucker, and Sacramento pikeminnow swimming performances tended to be lowest at 10°C, higher at 15°C, and then decreased or remained constant at 20°C. Hitch swimming performance was lower at 10°C than at 20°C. There were no significant differences among species at 10 or 15°C, although pikeminnow and hitch were ca. 20% slower than hardhead or sucker. At 20°C hardhead, Sacramento sucker, and Sacramento pikeminnow had remarkably similar Ucrit but hitch were significantly (by 11%) faster. We recommend that water diversion approach velocities should not exceed 0.3 ms−1 for hitch (20–30 cm total length) and 0.4 ms−1 for hardhead, Sacramento pikeminnow, and Sacramento sucker (20–30 cm TL).

The Swimming and Jumping Ability of Three Small Great Plains Fishes: Implications for Fishway Design

Abstract There is a distinct need for fishway designs that are passable by small-bodied fishes. Like many lotic systems worldwide, the streams of the North American Great Plains are frequently fragmented by instream structures and other potential migration barriers. This makes small-bodied fishes of the North American Great Plains appropriate species to use for fishway development. The swimming and jumping abilities of brassy minnow Hybognathus hankinsoni, Arkansas darters Etheostoma cragini, and common shiners Luxilus cornutus, acclimated to water temperatures of 10, 17.5, and 25°C, were quantified in the laboratory. Endurance increased with temperature for brassy minnow but not for the other two species. Based on swimming trial results, current velocities in fishways should not exceed 64 cm/s for brassy minnow or common shiners and 32 cm/s for Arkansas darters. Jumping experiments showed that the presence of a low vertical barrier (5 cm high) dramatically reduced the probability of upstream movement of ...

Effects of Temperature on the Growth, Food Consumption, and Thermal Tolerance of Age-0 Nimbus-Strain Steelhead

Abstract Although steelhead (anadromous rainbow trout Oncorhynchus mykiss) have the widest natural distribution among Pacific Coast salmonids, their populations have declined because of habitat loss, habitat alteration, and overexploitation. Because juvenile steelhead can be exposed to high summer water temperatures in streams and in California hatcheries that rely on surface water sources, we compared the food consumption, growth, and temperature tolerance of Nimbus-strain steelhead (an introgressed breeding stock in the American River) held at 11, 15, and 19°C in replicated laboratory experiments. Although food consumption rate showed no statistically distinguishable difference among temperatures, the growth rate was higher at 19°C than at 11°C or 15°C, providing evidence that food conversion efficiency in juvenile steelhead is higher at the warmer temperature. Age-0 steelhead showed a clear thermal acclimation effect, as their critical thermal maximum increased from 27.5°C for 11°C-acclimated fish to 2...

Two adjustable waterfalls for evaluating fish jumping performance

Abstract Instream obstacles such as low-head dams and waterfalls are important in fisheries management because they can restrict the movement of fishes. This can have detrimental or beneficial effects on a fish population, depending on whether a particular structure operates as a barrier to migration or as a barrier to invasion. We developed flashboard-type and flume-type adjustable waterfalls in the laboratory to study the effects of waterfall height and plunge pool depth on fish jumping performance. Our ultimate goal was to provide a quantitative method of evaluating pool-and-weir fish passage structures and waterfall barriers that could be applied to field situations. The adjustable waterfalls were successfully tested using adult Rio Grande cutthroat trout Oncorhynchus clarkii virginalis. The flashboard waterfall worked well in experiments where the combined waterfall height and plunge pool depth were less than the depth of the raceway. The flume waterfall worked well for the same conditions, but as de...

An Annular Chamber for Aquatic Animal Preference Studies

Abstract Preference chambers are widely used to measure the responses of aquatic organisms to different environmental gradients, such as temperature, salinity, and pollutants. Most of the preference chambers used to date have been handicapped by the presence of one or more confounding variables, including differential light intensities and water depths and the presence of cover. We present a design and test results for an annular preference chamber with uniform environment water depth, light intensity, and cover. Preliminary testing with juvenile anadromous rainbow trout Oncorhynchus mykiss showed that they selected temperatures (±SE) of 18.1 ± 0.3°C, a result that compares favorably with values reported in the literature. We demonstrate that the annular chamber is a viable alternative to the more traditional horizontal, vertical, or shuttlebox-type designs for preference studies of aquatic organisms.

Effects of Waterfall Dimensions and Light Intensity on Age-0 Brook Trout Jumping Performance

Abstract We conducted three experiments to understand the effects of (1) waterfall design (width, height, and plunge pool depth) and (2) light intensity on the ability of age-0 brook trout Salvelinus fontinalis to successfully jump over small waterfalls or vertical obstacles, such as pool-and-weir fishways. We measured the jumping performance of brook trout as a function of waterfall height (2–24 cm), plunge pool depth (8–18 cm), and fish size (total length (TL), mm). Waterfall height and TL had the largest effects on jumping performance. Maximum heights jumped decreased as waterfall height increased or TL decreased. Our second experiment measured the effects of waterfall widths of 10, 20, and 30 cm on age-0 brook trout jumping ability for a fixed waterfall height of 20 cm and a plunge pool depth of 40 cm. Significantly fewer fish jumped through the 10-cm-wide waterfall than through either the 20- or 30-cm-wide waterfalls. Our third experiment measured the jumping success of brook trout at light levels of...

A low-cost system for capturing and analyzing the motion of aquatic organisms

Abstract Capture and quantitative analysis of the motion of organisms is a powerful tool that can be used in diverse biological fields including physiology, behavior, kinematics, and ecology. A number of high-end commercial motion capture and analysis systems that offer a wide array of features and image capture and analysis capabilities are available. However, few, if any, such systems are low cost and could be used for projects with small budgets or by researchers interested in collecting pilot data before upgrading to an expensive motion capture and analysis system. Our paper describes a low-cost (<

Are We Preparing the Next Generation of Fisheries Professionals to Succeed in their Careers?: A Survey of AFS Members

US1000, not including the cost of the computer) motion capture and analysis system that simultaneously captures live video from 5 digital video cameras (Unibrain Fire-i FireWire [IEEE 1394]) using standard security camera software (SecuritySpy 1.3.1). The video analyses are carried out using a combination of standard spreadsheet software (Microsoft Excel) and a freeware image-analysis program (NIH Image J), with one of the available particle-tracking plugins. Tests using New Zealand mudsnails (Potamopyrgus antipodarum) demonstrated that the system could record and accurately track the movement of small (4 mm) targets. Recommendations for designing similar project-specific systems are provided.